RU2374746C1 - Electrostatic micro-, nanomotor - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: electrostatic micro-, nanomotor is intended for constructing movement and transportation systems, in micro- and nano-dimensional scale, for example in robotic technology, and namely, in nano- and micro-robotic systems for medical purpose. Motor consists of power supply, at least two plates located relative to each other with a gap and with the possibility of changing owing to electrostatic impact of their spatial orientation relative to each other. In micro-, nanogap between the plates there located with the possibility of being fixed is corrugated self-forming elastic nanocover - spring made of mechanically stressed film. Nanocover - spring changes its shape and elastic coefficient at changing mutual position of plates, when supplying voltage to plates or also to nanocover - spring from power supply and their development of electrostatic impact.

EFFECT: enlarging functional capabilities and application fields of motor, increasing the range and improving accuracy of movements, increasing motor power.

17 cl, 17 dwg

Description

The invention relates to electromechanics, as well as to the field of microstructural technology, in particular to micromechanical devices with moving, flexible or deformable elements. The invention can be used to build micro- and nanomotors of systems of movement and transportation for various purposes, moving in a micro- and nanoscale scale, as well as motors having micro- and nanoscale, for example, in robotics, including nano- and microrobotics medical systems.

Known electrostatic micro-, nanomotor (German application for invention DE 102005018955, IPC: 8 H02N 1/00), containing a positioning unit made up of two pairs of counter electrostatic electrodes, an electrically insulated elastic element and an electrostatic converter of electrical energy into a mechanical, flat electrode - a substrate on which a positioning unit is located, and a power source for selectively supplying an electric potential to the electrodes. In the converter, comb structures are used that are arranged towards each other with the possibility of overlapping, representing a capacitor that provides movement by varying the capacitance. Counter electrodes are mechanically connected to an elastic element made of a polymer, polymethyl methacrylate. The flat electrode substrate acts as a contour electrode to the counter electrodes.

The disadvantages of the known technical solutions include: limited functionality and applications; limited range of movement; low accuracy of movement; low engine power. These disadvantages are due to the following reasons. Firstly, the movement is carried out in a direction perpendicular to the electric field vector, which leads to a small amount of forces developed by engines of this type with control voltages of the order of several volts. In order for these engines to have sufficient efficiency, a control voltage of about 100 V and large motor sizes are required. Secondly, during movement, there is the possibility of skewing and subsequent closure with friction of the electrodes of the comb structures, which significantly limit the length of movement and make it impossible to implement this engine on a nanoscale scale, with nanogaps. Comb type motors are bulky. The presence of a large number of combs is caused by the need to increase the total attractive force of the capacitor plates, which is an electrostatic converter. Thirdly, the implementation of this engine is based on the capabilities of standard technologies, with their inherent impossibility of scaling sizes downward, their precision exposure and a limited range of materials used in the structural elements of the engine, which ultimately leads to a lack of control in the development of static effects . Fourth, an engine of this type can be used for movements in only one direction.

Known electrostatic micro-, nanomotor (Y. Nemirovsky, O. Degani, A methodology and model for the pull-in parameters of electrostatic actuators. J. Micromech. Syst, v. 10, (4), 2001, pp. 601-615 ) containing a power source and two plates electrically connected to it. In this case, plane-parallel plates, which are electrodes, are placed relative to each other with a gap, one of them is fixed, and the other is suspended with the possibility of its rotation around an axis passing through the suspension point, when attracted towards the fixed plate when applying the potential difference to them and the occurrence of electrostatic gravity.

The disadvantages of the known technical solutions include: limited functionality and applications; limited range of movement; low accuracy of movement; low engine power. The main reason preventing the achievement of the technical result is the instability of the electrostatic motor (converter), known as the sticking of electrodes. When a potential difference is applied to the electrodes, an electrostatic force arises between them, forcing the suspended electrode to rotate and be attracted towards the stationary electrode until equilibrium between the electrostatic force and the mechanical elasticity of the suspension occurs. Equilibrium occurs in the cases when, after moving the movable electrode, the gap between the electrodes is sufficiently large, at least 2/3 of the initial gap. If, when a potential difference is applied to the electrodes, an electrostatic force arises that exceeds the elastic force of the suspension, then contact occurs between the electrodes - the sticking phenomenon. Thus, this fact, despite the attractiveness of electrostatic motors (converters), is largely due to the possibility of accumulation of a large energy density in them and the achievement of a large force in them, as well as the simplicity of design and manufacture, easy integrability in micro- and nanosystems, however less, is a significant obstacle to the use of engines in various micro and nanosystems. The sticking phenomenon is the reason for limiting the range of possible movements, low accuracy of movement, and prevents the development of large forces. Since the force of electrostatic attraction depends quadratically on the reciprocal distance between the plates, the maximum force is achieved at minimum distances between the plates. In the considered analogue it is impossible to achieve small distances (less than 2/3 of the initial distance), which limits the magnitude of the developed efforts. Therefore, despite these potential opportunities, the implementation of the engine can only be carried out as a low-power one. The same reason makes it impossible to scale down.

As the closest technical solution, an electrostatic micro-, nanomotor was identified (Y. Nemirovsky, O.Degani, A methodology and model for the pull-in parameters of electrostatic actuators. J. Micromech. Syst, v.10, (4), 2001, pp.601-615), containing a power source with which two plane-parallel plates are electrically connected, which are electrodes placed with respect to each other with a gap, one of them is fixed, and the other with the possibility of linear movement with attraction towards the fixed plate when feeding potential differences on the plates and the occurrence of electric ktrostaticheskoy gravity.

The disadvantages of the closest known technical solutions include: limited functionality and applications; limited range of movement; low accuracy of movement; low engine power. The main reason preventing the achievement of the technical result is the instability of the electrostatic motor, known as the sticking of electrodes. When a potential difference is applied to the plates, a Coulomb attraction is created, causing the plate to move and the distance between the movable and fixed plates to change. In this case, the possible range of movements is 1/3 of the initial distance between the plates. When you try to increase the displacement distance, the phenomenon of adhesion of the plates occurs. As a rule, an elastic element in an electrostatic engine that provides movement of the plate, for example a spring, changes its size in proportion to the applied force. The electrostatic force depends quadratically on the reciprocal distance between the plates. The difference in functional dependences on the distance of the elastic and attractive forces, in the first case is direct proportional, in the second case is inverse quadratic, limits the range of possible displacements to the specified value. Thus, the existence of the considered clumping phenomenon, despite the attractiveness of electrostatic motors, is largely due to the possibility of accumulation of a high energy density in them and the achievement of a large force in them, as well as the simplicity of design and manufacture, easy integrability in micro- and nanosystems, nevertheless is a significant obstacle to the use of engines in various micro and nanosystems. The sticking phenomenon is also the reason for the low accuracy of movement, since the working range is limited by the fulfillment of the condition of the presence of large distances between the plates. Thus, despite the fact that the potential for the development of large forces in this engine looks encouraging, in fact, the implementation of the engine can only be realized as a low-power and inaccurate in movement. The presence of the same phenomenon makes it impossible to scale down.

The technical result of the invention is:

- expansion of functionality and applications;

- increase the range of movements;

- a significant increase in the accuracy of movement;

- achievement of extremely large engine forces (increase in power).

The technical result is achieved in that in an electrostatic micro-, nanomotor containing a power source, at least two plates located with respect to each other with a gap and with the possibility of changing due to the electrostatic effect of their spatial orientation relative to each other, in a micro-, nano-gap a self-forming elastic nano-shell is placed between the plates with the possibility of fixation - a spring made of a mechanically strained film that changes its shape and coefficient of elasticity when measured By varying the relative position of the plates, the plates and the nano-shell - spring, or plates, or the plate and the nano-shell are made with the possibility of applying voltage to them from the power source, and working out the electrostatic effect.

In an electrostatic micro-, nanomotor nano-shell - the spring is made corrugated.

In the electrostatic micro-, nanomotor, the fixation of the nanoshell - spring is made by rigid fastening to the edges of the plate.

In an electrostatic micro-, nanomotor, a nanoshell - a spring is made of a semiconductor, or metal, or a dielectric, or a semiconductor and metal, or an dielectric and metal, or a dielectric and a semiconductor, or a semiconductor, and a dielectric, and metal.

In an electrostatic micro-, nanomotor, the plate is made of a semiconductor, or a metal, or a dielectric, or a semiconductor and a metal, or a dielectric and a metal, or a dielectric and a semiconductor, or a semiconductor, and a dielectric, and metal.

In an electrostatic micro-, nanomotor, the nano-shell is a spring that is corrugated unevenly with respect to its area, only at the edges, with an increase in the height of the corrugations in the direction towards the edges freed from communication with the plate.

In an electrostatic micro-, nanomotor nano-shell, the spring is corrugated uniformly in relation to its area with a continuously periodic arrangement of long identical corrugations.

In an electrostatic micro-, nanomotor, a nano-shell - the spring is corrugated uniformly with respect to its area with an intermittently or continuously periodic arrangement of extended zigzag corrugations.

In an electrostatic micro-, nanomotor nano-shell, the spring is corrugated uniformly with respect to its area, with a discontinuously periodic arrangement of dome-shaped corrugations.

In an electrostatic micro-, nanomotor as a part of plates and nano-shells - springs, or as part of plates, or as a part of a plate and nano-shells - springs, made with the possibility of using them as electrodes, an array of conductive elements designed to create a local electric field or its gradient, providing a controlled change in the angle between the plates.

An array of concentrically arranged conductive elements is formed in the electrostatic micro-, nanomotor, with the possibility of creating a local electric field or its gradient along radial lines, and along circles, while the orientation of the axes of the corrugations of the nanoshell - spring, is also made radial.

The electrostatic micro-, nanomotor is multi-stage, of n stages connected in series, where n≥1, while each of the plates of the nth stage is made with the possibility of belonging to the n-1 cascade or the n + 1 cascade.

In a multi-stage electrostatic micro-, nanomotor, a nano-shell - spring with respect to different stages is made of different thickness and / or height of the corrugation, and / or shape, and / or spatial orientation for precision control of the engine in relation to different stages.

In an electrostatic micro-, nanomotor nano-shell, the spring is made of a strained multilayer film containing at least one stretched layer.

In an electrostatic micro-, nanomotor, a nanoshell — the spring is made of a strained multilayer film containing three layers, the outer ones being compressed, and the film thickness periodically modulated by the outer layers, the modulation period of the thickness of one outer layer and the modulation period of the second outer layer being shifted relative to each other .

In an electrostatic micro-, nanomotor, at least one of the plates is made in the form of a cantilever.

In an electrostatic micro-, nanomotor, at least one of the plates is made in the form of an arch.

The invention is illustrated by the following description and the accompanying drawings.

Figure 1 schematically shows the sequence of formation of a bulging film freed from communication with the plate (substrate), which is the simplest nanoshell - spring: a) the stage of deposition of a sequentially sacrificial AlAs layer, an InAs functional layer on the plate (InP substrate), the lateral dimensions of the latter exceed the dimensions of the substrate InP, due to the fact that the InAs lattice constant is greater than the InP lattice constant; b) the finished InAs / AlAs / InP heterostructure, in which the InAs film inherits the lattice of a massive substrate (pseudomorphism phenomenon), as a result, the InAs layer is compressed; c) the stage of selective lateral removal of the sacrificial layer material, separation of the middle portion of the compressed InAs functional layer and the formation of the simplest nanoshell — fixed-spring springs as a result of buckling of the film portion separated from the substrate.

Figure 2 presents an illustration of the structure of a micro-, nanomotor, in which the upper movable plate is able to move in the vertical direction under pressure P, the force acting from the side of the movable plate on the nanoshell - spring - F: a) the initial state of the structure before applying external pressure R; b) image of the cross-section of the structure when pressure P is applied, in the formed region of tight fit of the nano-shell - the spring to the movable plate, l - the length of the substrate, l ₁ - the length of the curved part of the nano-shell - spring, l ₂ - the length of the adjacent part of the nano-shell - spring, h - distance between the plates; where 1 is a fixed plate (substrate), 2 is a movable plate, 3 is a nano-shell is a spring.

Figure 3 shows the dependence of the gap between the plates (left) - a) and the shape of the nanoshell - spring (right) - b) from the voltage applied to the plates; at the same time, “Load” - increase in applied voltage, “Unloading” - decrease in applied voltage, I - state of a system with one corrugation, II - state of a system with two corrugations, III - state of a system with three corrugations (i - corrugation touches the plates at the top points , ii - corrugations with a tight fit region of the nanoshell - the spring to the plate), the dashed arrows on the left show the order of changing the shape of the nanoshell - the spring with increasing pressure (load) on the upper movable plate, vertical curly arrows show the shape change during unloading.

Figure 4 shows the calculated dependences of the gap between the plates on the applied voltage, the calculations were performed for a nano-shell - a spring of InAs semiconductor material with a thickness of 6 nm and a strain of mismatch of the lattice parameters of 2% for the substrate length: a) 750 nm; b) 1000 nm; c) 1200 nm.

Figure 5 shows the calculated dependences of the threshold values of the vertical pressure caused by the electrostatic attraction of the plates on the thickness of the nanoshell - springs, the threshold values Iii correspond to the transition from the state with one corrugation to the state with two corrugations, and IIii correspond to the transition from the state with two corrugations four corrugations, the calculation was performed for the initial InAs semiconductor film with a thickness of 6 nm, a strain equal to 2%, and the length of the substrate: a) 750 nm; b) 1000 nm; c) 1200 nm.

Figure 6 presents a table of values of threshold values of vertical pressure at which there is a change in the shape of the nanoshell - spring.

Figure 7 shows a schematic illustration of the operation of a torsion electrostatic engine with a corrugated nanoshell - spring: a) a schematic representation of the initial structure with a corrugated nanoshell - a spring located in the gap between the plates; b) a schematic illustration of an engine with a movable top plate; c) rotation of the upper plate as a result of a change in the shape of the right half of the nano-shell - spring due to electrostatic attraction (when the right part of the nano-shell - the spring is attracted to the lower fixed plate, the upper movable plate turns to the right); d) when the left side of the nanoshell is attracted - the springs the upper movable plate rotates to the left; where 1 is a fixed plate (substrate), 2 is a movable plate, 3 is a nano-shell is a spring, 4 is a sacrificial layer.

Figure 8 shows the edge corrugated nanoshells - springs: a) the shape of the edge corrugated shell Si _0.6 Ge _0.4 / Si (thickness, respectively, 11 nm / 8 nm) obtained using an atomic force microscope, corrugation period 2 5 microns, height 120 nm; b) corrugation at the edges of SiGe film strips, 90 nm thick, corrugation period 2 μm; c) corrugation at the edge of the InGaAs / GaAs film, 70 nm thick; g) a schematic representation of elastically interacting edge corrugated nanoshells - springs; e) elastically interacting SiGe / Si corrugations (strip width 10 μm, film thickness 50 nm).

Figure 9 presents the edge corrugated nano-shells - springs with different periods and the height of the corrugations: a) a schematic representation of the corrugations, the period of which increases as the etching laterally deep into the sacrificial layer; b) corrugations containing corrugations with different periods and heights obtained on the same SiGe film.

Figure 10 shows the domed nano-shell springs:

a) a schematic representation of a domed nano-shell - a spring touching the upper movable plate at one point; b) a schematic representation of a circular region adjacent to the movable plate; c) an experimental photograph of a dome-shaped nano-shell - SiGe spring with a thickness of 150 nm, touching at one point (square size 8 μm × 8 μm); d) an experimental photograph of a domed nanoshell - Si springs in the phase of forming a circular region transparent to light (the flattened vertex of the convex domed shell (square size 8 μm × 8 μm) is clearly visible; e) InGaAs nanocupola (square size 100 nm × 100 nm); real images were obtained with an atomic force microscope.

11 shows electron microscopic images of experimental structures illustrating a twofold decrease in the period of a corrugated nanoshell - spring when it is compressed in the case of

GaAs-200 hm / In _0.35 Ga _0.65 As-2 nm corrugation on a GaAs substrate: a) the initial structure with a nanoshell — a spring in the gap between the fixed plate (substrate) and the upper transparent movable plate; b) the same structure, but after applying bias to the transparent movable plate and the substrate, with a corrugation period reduced by 2 times (it can be clearly seen that the number of corrugations with a maximum height doubled, while the corrugations at the upper edge with a low height remained unchanged , since the upper loaded transparent plate was parallel to the substrate and did not touch small corrugations).

Figure 12 shows the structures intended for the manufacture of electrostatic micro-, nanomotors: on the left a schematic illustration, the sacrificial layers are light, the experimental results are shown on the right (electron microscopic images of the cross-sections of the structures), the upper part shows the structure on which the engine was made with an overhead top movable plate, in the middle part shows a structure with InGaAs nano-shell - spring, almost ready for use as an engine (necessary only make the movable part of the upper plate), the lower part shows one of the many, more complex, structural options in which the nano-shell - InGaAs spring is also obtained by self-formation.

Figure 13 shows extended corrugated nano-shells - springs: a) a schematic representation; b), c) optical and d), e) electron microscopic experimental photographs illustrating the possibility of scaling the characteristic sizes of InGaAs nanoshells - springs from micrometers to nanometers.

On Fig presents: a) corrugated nanoshell - the spring of graphene (monatomic carbon layer), the image was obtained using an atomic force microscope; b) a cross-sectional profile of the corrugated graphene shell (along line A shown in part a) of this figure).

On Fig schematically presents a nano-shell - a spring in a multilayer design with compressed and stretched layers: a) corrugation of a strained three-layer film with compressed outer layers with a periodically modulated thickness due to the external, compressed layers; b) corrugation, which simultaneously performs the function of an electrode, when practicing static impact; where 1 is a fixed plate (substrate), 5 is a compressed outer layer, 6 is a stretched inner layer.

Figure 16 shows photographs of a real micro-, nanomotor with a fixed upper movable plate by means of lateral springs, with edge corrugation used as a nano-shell - spring: a) top view; b) side view (section); c) an array of edge corrugations - nanoshells - springs (the upper movable plate, the function of which is performed by a GaAs film, is removed); d) an enlarged image of a nano-shell - a spring, made in the form of edge corrugation along the perimeter of a quadrangle, oriented part inside out of communication with the substrate.

On Fig shows the capacitance-voltage characteristics obtained by testing laboratory samples of engines made on structures with a no-shell - spring In _0.15 Ga _0.85 As 20 thickness them: a) the capacitance-voltage characteristic of the engine, implemented on the edge corrugations on the perimeter of the quadrangles oriented, freed from communication with the substrate, the part inside the quadrangle, with forward and reverse motion, the nature of the change in capacitance with increasing and decreasing voltage is shown by arrows; b) the capacitance-voltage characteristic of the engine, implemented on the edge corrugations made on opposite sides along the perimeter of the quadrangle, oriented part inside the quadrangle freed from communication with the substrate; c) the capacitance-voltage characteristics of the engine with and without load on the upper movable plate.

The achievement of the technical result is based on the use of unique high-precision nanoshells - springs (shells of nanometer thickness), which are placed in a micro-, nanogap between the plates of an electrostatic motor that perform the function of capacitor plates with a variable gap size. Nano-shells - springs are made of strained solid-state films, which, upon local disconnection from the substrate (plate) (see Figure 1), are transformed into nano-shells of a given shape: in the form of corrugations, hemispheres, and other shapes (see Figure 1-3, FIG. 7-16). The main factor for achieving a technical result is that these nano-shells - springs are located between the plates of the electrostatic motor and are able to change their shape and, accordingly, increase the coefficient of elasticity as the plates approach each other. The location of elastic nanoshells - springs between the plates of the electrostatic engine in combination with the possibility of high-precision setting of micro- or nanogap between the plates, the possibility of a wide selection of materials for its manufacture, the possibility of high-precision setting of the thickness of the nanoshell - the spring, its atomic smoothness, and the increase in the rigidity of the nanoshell - the spring as the proximity of the plates during the application of electrostatic effects, in total, can achieve the expansion of functionality and areas of application and I; increase the range of movements; precision movement; increase engine power.

When forming a nano-shell - a spring from a mechanically stressed (compressed) layer by local disconnection from a fixed plate (substrate), depending on the area and geometric configuration of the detachable region of a mechanically strained film (film element), it is transformed into a shell of one form or another.

The simplest, from the point of view of formation, nano-shell - spring is an extended corrugation (see Figure 1, Figure 2). Long corrugation is obtained by disconnecting the middle part of the film element made in the form of a strip, in which portions of the ends of the strip remain connected to the substrate, due to which the nano-shell - spring is fixed (see Figure 1). In the simplest case, the nanoshell - the spring contains only one stressfully compressed layer. The stressfully compressed layer can be formed by epitaxy from a material having a crystal lattice constant greater than that of the material of the fixed plate (substrate) (see Fig. 1a)). A heterofilm is grown epitaxially on a plate (or substrate) from the sequence of the sacrificial layer, a mechanically compressed layer that, after being released from the bond with the substrate, is a functional element of the nanoshell - spring (see Fig. 1b)), observing the conditions of pseudomorphic growth under which each layer is successively grown inherits the lattice constant of the plate (substrate). During the subsequent directional side etching of the sacrificial layer, on which the made film element is located in the form of a strip of a tightly compressed layer, its middle part is separated from the plate (or substrate) (see Fig. 1 c). Since the interatomic forces in the compressed layer tend to increase the distance between the atoms, the linear dimensions of the film increase, which leads to bending, buckling of the film, and the formation of corrugation. Thus, as a result of the action of the internal (embedded in the layer) elastic deformation forces, the layer acquires a convex shape (corrugation) corresponding to the minimum energy of internal stresses. The opposite ends of the nanoshell - the springs are fixed on a fixed plate (substrate) (see Fig.1c)), since during the lateral etching the sacrificial layer has time to dissolve only in the middle part.

It was said above that nano-shells - springs can be of one form or another. When local areas of the film element are detached from the plate (substrate), for example, made in the form of a circle or a square, the detachable compressed film in this area expands and bulges, forming a nanoshell - a spring in the form, for example, of corrugation with more than one fold (corrugation), edge corrugations, hemispheres or domes, the edges of which remain fixed (see Fig.7-13).

It is important to emphasize that even at the stage of growing a multilayer heterostructure (see Fig. 1a)), the initial distance between the plates, the height and the corrugation period of the micro-, nanomotor can be set with high accuracy. The thickness of the nano-shell - the spring (or corrugation) can be set in the range from nanometer to micrometer, in accordance with the distance between the plates. Compression strain is set by the mismatch of the lattice parameters of the substrate (plate) and the grown compressed layer. For thin films, the deformation can reach a gigantic value of 7-5%.

Previously, the problem of creating an electrostatic micro-, nanomotor and the problem of nano-shells - springs were not considered. Structures for quantum devices were made by the method of self-formation. The essence of our approach is to apply: a) the sacrificial layer; b) directional etching and selective removal of the sacrificial layer; c) the formation and use of an elastically stressed layer due to a mismatch between the constant lattices of the heterofilm material and the substrate; d) forming the region of the detachable stress film or specifying the geometry of the detachable film element. The following experimental structures are grown and formed by us for the first time. The process of buckling of stressed films in the macrocosm is known and is described by the theory of elasticity. However, in the nanoworld, in which the electrostatic forces become gigantic, no one has previously dealt with the problem of the formation of nanoshells - springs and their placement in the micro-, nanogap between the plates. We first demonstrated the formation of this class of structures. It should be emphasized that the prior art does not know any other methods of placing a nano-shell - springs in a micro-, nano-gap between the plates of an electrostatic engine.

Note that the key points in the implementation of an electrostatic micro-, nanomotor are: firstly, the process of forming a nanoshell - a spring when a stressed-compressed film is disconnected from the substrate of a film element is self-forming; secondly, a nano-shell - the spring is automatically placed in the gap between the engine plates.

So, the proposed designs of micro-, nanomotors are based on self-forming and self-assembled precision elastic solid-state nanoshells-springs, moreover, they are automatically placed in micro-, nanogap between plates, which are capable of changing their shape and, accordingly, changing their coefficient of elasticity upon application of external influence.

Nano-shell - a spring with fixed ends or edges should be considered as an elastic spring, which, as the deformation increases with compressive force, is transformed into a more rigid nano-shell - a spring, with smaller characteristic periods and sizes. Thus, when a potential difference is caused from the power source that causes the plate to move, the nanoshell - spring due to internal elastic mechanical stresses can change shape and act like a spring with an increasing coefficient of elasticity, preventing the plates from coming together,

Auto-displacement in the micro-, nano-gap between the plates of the nanoshell - the spring prevents the adhesion of the plates (electrodes), eliminates the reasons that impede the achievement of the technical result in the above-described known technical solutions.

Consider in detail the physical side of achieving a technical result.

Let between the plane-parallel plates (1) and (2) of the electrostatic micro-, nanomotor there is a nanoshell - a spring (3) containing mechanically stressed layers, made in the form of a corrugation of the simplest form, that is, in the form of one wavy fold, or corrugation (see Figure 2). Opposite ends of the nano-shell obtained by the above-described method - springs (3) are fixed on a fixed plate (1) (substrate). Nano-shell - spring (3) touches the top of a single corrugation of the movable plate (2). The length of the nano-shell - spring (3) is greater than the length of the plate (1) (substrate) (the distance between the fixed ends of the nano-shell - spring (3) - l (see Fig.2b)). In the middle part, the initial film, separated from the plate (1) (substrate), bulges and takes the form of a corrugation.

Figure 2 a) shows the state of the micro-, nanomotor, in which there is no deformation due to the action of electrostatic forces (shape change) of the nanoshell - spring (3), and no pressure is applied to the movable plate (2). By changing the magnitude of the pressing force from the side of the movable plate (2), displaced in the normal direction of the fixed plate (1), you can control the height h, the shape and number of corrugations.

When applying the potential difference from the power source to the plates (1) and (2) under the action of an attractive force causing the plate (2) to move towards the fixed plate (1), or applying mechanical pressure P, deformation (change in the initial shape) of the nanoshell springs (3) (see Fig.2b)). If in the initial position (see Fig. 2a)) there was a contact only of the highest points of the only corrugation of the nanoshell - the spring (3) to the movable plate (2), and the ratio of the fixed plate (1) - only at the points of the ends, then with decreasing the gap (Figure 2, Figure 3) between the plates (1) and (2) under the action of electrostatic force or the application of mechanical pressure to the movable plate (2), relative to the nanoshell - spring (3) there is a pressing force and the contact area of the nanoshell - spring (3) with plate (2) increases. As the voltage applied to the plates (1) and (2) increases, the contact area l ₂ (see Fig. 2 b)) of the nanoshell - springs (3) with the plate (2) increases, and the mechanical compression stresses in the nanoshell also increase - the spring (3), causing a change in its shape, also increases the force F acting in the places of attachment of the nanoshell - spring (3) to the fixed plate (1) (substrate). During the formation of a spring (3), which is sufficiently long in the direction of the fixed ends of the adjacent part of the nanoshell, a loss of stability may occur in the area of contact. When the value of the mechanical compression stress in the contact areas reaches the threshold value, the flat part of the nanoshell - spring (3) in contact with the plate (2) becomes unstable, it flexes sharply towards the plate (1). As a result, two corrugations are formed from one corrugation (wavy fold) (see Figure 3, right part b), (II.i)).

Nano-shell - spring (3) changes its initial shape in steps, taking the form corresponding to a steady state. Suddenly, that is, in the switching mode, the number of corrugations also changes during the deformation of the nanoshell - springs (3). After switching, each of the formed corrugations is in the same conditions.

The plates (1) and (2), between which the nano-shell is placed - the spring (3), made non-conductive in this case, are the plates of a flat air condenser. The magnitude of the vertical pressure P is determined by the magnitude of the electrical voltage across the capacitor V. The dependence of P on V can be represented as:

where S is the area of the plates;

[Ф/м]-диэлектрическая постоянная;

[F / m] - dielectric constant;

h is the distance between the plates of the capacitor, as well as the height of the corrugations.

Thus, by changing the voltage across the capacitor (or plates (1) and (2)) and, consequently, the magnitude of the vertical pressure, it is possible to control through the distance between the plates the h shape and the number of corrugations of the nanoshell - the spring (3) located between the plates of the capacitor. A typical graph of the dependence of the gap on the value applied to the plates (1) and (2) voltage is shown in Fig.3. An increase in voltage leads to a nonlinear decrease in the gap and height of the corrugations, the greater the voltage, the less the size of the gap and the height of the corrugations and, consequently, the shape of the nanoshell - spring (3) change, which indicates an increase in its rigidity. The latter means that the greater the rapprochement of the plates, the greater the resistance will be provided by the nano-shell - the spring, preventing the rapprochement.

The distance between the plates (1) and (2) is reduced to almost zero. The nanoshell - spring (3) performs the function of a spring with a changing coefficient of elasticity, the value of which increases with decreasing distance between the plates (1) and (2). The initial value of the coefficient of elasticity is set with high accuracy, for example, during epitaxy by selecting materials of mechanically stressed layers of the nanoshell - springs (3) and their thicknesses. This means that the possibility of precision, with sub-angstrom accuracy, changes in the distance between the plates (1) and (2) is realized.

With further convergence of the plates (1) and (2), the pressing force on the nanoshell - the spring (3) increases. Considering that each formed corrugation is an independent nano-shell - spring (quasi-shell - spring), similar to the original nano-shell - spring (3) (see Figure 3, right-hand side b) (Ii)), the above process is repeated for each formed corrugation ( see Figure 3). Thus, if a nano-shell - spring (3) deformed as a result of the action of electrostatic forces of attraction of the plates, first touches the moving plate (2) with the highest points of both corrugations in two places (II.i), then with a further increase in the pressure force until the next threshold value is reached there is a formation of the area of tight fit of the nanoshell - the spring (3) in relation to each of the formed corrugations (see Figure 3, the right part b) (II.ii)), and upon reaching the next threshold value of the pressing force of quantities corrugations again abruptly doubled. Further, as the plates (1) and (2) come closer and the pressure exerts on the nanoshell - spring (3) increases, the whole process will be repeated first (see Figure 3, right-hand side b) (III.i) and (III.ii )). The solid arrows (see Figure 3, right-hand side b)) show the direction of the change in the shape of the corrugation (nanoshells - springs (3)) during the transition from the point of contact of the corrugation and the movable plate (2) at the tops of the corrugations to the formation of a tight fit region; the dashed arrows indicate the direction of the change in the shape of the corrugation with an abrupt increase in the number of corrugations.

During unloading, i.e., a decrease in the pressure force and the reverse stroke (removal of the plates (1) and (2) from each other), the areas of tight fit gradually decreasing will go into the state of point contact of the upper points of the corrugations with the movable plate (2) at those the threshold values of the pressing force and compressive force as a result of the attraction of the plates (1) and (2), at which areas of tight fit were formed during the forward stroke (the plates (1) and (2) approach each other). A jump (or switching) in the direction of decreasing the number of corrugations occurs if the magnitude of the pressing force and compressive force as a result of the attraction of the plates (1) and (2) is less than the minimum necessary value to ensure the existence of a single corrugation in each individual section of the nanoshell - springs (3), which is a single quasi-shell - a spring. When unloading, each subsequent switching reduces the number of corrugations by half. In Fig. 3, the unloading process in the reverse order is shown in the direction indicated by the vertical curly arrows.

Consider the influence of the length of the substrate (nano-shells - springs). Figure 4 shows the calculated dependences of the gap on the applied stress for a nano-shell - a spring made of InAs semiconductor material, the initial layer of which 6 nm thick was grown on an InP substrate (plate) (see Figure 1) For definiteness, the compression strain in the layer was set equal to 2% The graphs are plotted for different lengths of the substrate on which the nano-shell is fixed - spring: a) 750 nm, b) 1000 nm, c) 1200 nm. Different lengths of the substrate correspond to different lengths of the nanoshell - springs. It can be seen that the length affects the size of the gap (the height of the corrugations), the initial and formed during deformation of the nanoshell - spring under the influence of electrostatic effects. It should be noted that on inclined sections there is an almost linear change in the distance between the plates from the voltage. This suggests that it is possible to set with high accuracy the displacement of the upper, movable plate, throughout the entire phase of the formation of the area of tight adherence to it of the nanoshell - spring, until the moment of switching.

It is also clearly seen from the graphs that, depending on the length of the substrate, not only the height of the corrugations changes, but also the threshold stresses necessary to change the shape of the corrugations and their number (switching voltage or jump).

Moreover, we take for example nano-shells - springs with a thickness of 10 nm, 16 nm and 20 nm (see Fig. 6, table) and consider the values of threshold vertical pressure forces (or threshold stresses) for them. The table shows that with a fixed thickness, an increase in length leads to a decrease in threshold values. So, for the thickness of the nanoshell - spring 10 nm with a length of 750 nm, the threshold value is 689 kg / cm ² , with a length of 1000 nm - 291 kg / cm ² , with a length of 1200 nm - 168 kg / cm ² . A similar situation is observed for thicknesses of 16 nm and 20 nm. The considered features are due to nothing more than a decrease in the rigidity of the nanoshell - the spring with an increase in its length.

Thus, the calculated data (see Figure 4) show: a) the threshold nature of the transition from a state with one corrugation to a state with two corrugations and vice versa; b) the presence in the behavior of the system of gaps, characterized by a linear change in the distance between the plates with a change in voltage; c) the presence in the behavior of the system of gaps characterized by the accumulation of elastic energy at a constant distance between the plates (both in the case of loading and in the case of unloading).

These features can be used in the development of devices designed for nanosurgery, especially since the proposed micro-, nanomotors belong to the class of powerful, developing great efforts.

The effect on the rigidity of the nano-shell - spring is provided not only by the length of the substrate, but also by the thickness of the nano-shell - spring (see Fig. 6, table). Moreover, the role of thickness in increasing stiffness and the role of the length of the substrate are proportional. This is clearly seen from the table in which the magnitude of the vertical pressure force, with an increase in the thickness of the nanoshell - spring 1.6 times, changes about 4 times. A change, by 4 times, in the direction of decreasing, the magnitude of the vertical pressure force occurs with an increase in the length of the substrate from 750 to 1200 nm (also 1.6 times). This makes it possible to manipulate the properties of the device (such as stiffness, threshold transitions, precision offsets, and others).

The results of a study of the effect of the thickness of the nano-shell - spring are shown in Fig. 5 in the form of graphs of the calculated dependences of the threshold values of the vertical pressure force caused by the electrostatic attraction of the plates on the thickness of the nano-shell - spring. To obtain a complete picture, the calculation was performed for the same InAs film with a strain of 2%, although it is obvious that it is impossible to grow pseudomorphic InP films of large thickness (more than 10 nm).

The dashed curves correspond to threshold values during the transition: touching at one point is the formation of a tight fit region (I.i, II.i) (see Figure 5). The solid curves represent the condition under which switching occurs with an increase in the number of corrugations (I.ii, II.ii) (see Figure 5). The graphs clearly show that the threshold pressure forces characteristic of the indicated areas of contact differ by several times, and this gap increases very rapidly with increasing thickness. So, for example, when the film thickness changes from 10 to 20 nm, the threshold pressure values increase by almost 10 times (see Fig. 6, table).

Important from the point of view of practical applications, it is possible to set the required range of power (force) of a micro-, nanomotor on a scale from several tens of kilograms to several tons per square centimeter, setting the corrugation thickness or the length of the substrate. For the case of series-connected micro-, nanomotors, this opens up the possibility of controlling the strength of the engine and the accuracy of movements.

The presented dependences were obtained for a large area (cm ² ). Since the most important areas of application of the proposed engines are related to micro- and nanosurgery, micro- and nanorobots, it makes sense to recalculate the pressure data on micro- and nanoscale areas. So, for example, an engine with a size of 1 μm, as follows from Figure 5, can develop forces of almost 1 g, working in mode II, when switching to mode III (see Figure 3), the forces increase by 4 times. This is a giant effort in the micro and nanoworld.

Thus, in contrast to the well-known technical solutions, the proposed engine has the following abilities: to develop gigantic efforts (of the order of 10 t / cm ² ) when moving into the nanometer range; work with high accuracy with small offset values. The prior art does not know any other analogues of electrostatic motors that allow you to achieve gigantic forces at small sizes and subangstrem accuracy of movements. We emphasize that during switching, giant forces also develop.

Consider the technological aspect of the implementation problem of the proposed micro-, nanomotor with the achievement of the specified technical result.

The construction of the proposed electrostatic micro-, nanomotor is carried out on a new approach using the properties of nanofilms and nanoshells. The implementation of one of the most important structural elements in terms of achieving a technical result, namely, a nanoshell - a spring, the proposed device is based on the principles of previously developed nanotechnology (Prince V.Ya., Golod S.V. “Elastic nanoshells based on silicon films: formation, properties and practical application ", ПМФТ, 2006, vol. 47 (6), pp. 114-128; Prinz V. Ya." Properties of semiconductor nanotubes and nanoshells fabricated on (111), (110) GaAs, Si and on vicinal (001) GaAs substrates ", Physica E, 2004, V.23, pp260-268; Prince V. Ya." Three-dimensional self-forming nanostructures based on free strained heterofilms ", Proceedings of the Universities" Physics ", 2003, 46 (6), pp. 35-43; Prinz V.Ya." Precise semiconductor nanotubes and nanocorrugated quantum systems ", Physica E, 2004, V.24 , pp54-62; Prinz V.Ya. “A new concept in fabricating building blocks for nanoelectronic and nanomechanic devices”, Microalectronic Engineering, 2003, V.69 (2-4), pp466-475; Prince V.Ya. , Seleznev V.A., Chekhovsky A.V. "Self-forming semiconductor micro- and nanotubes." Microsystem technology, 2003, No. 6, pp. 10-16; Prinz V. Ya. "Precise, molecularly thin semiconductor shell: from nanotubes to nanocorrugated quantum systems", Phys. Stat. Sol. (b), 2006, V.243, Iss. 13, p.p.3333-3339). In the cited works, the principles of the formation of three-dimensional objects, shells under the action of elastic forces, when releasing planar structured films from communication with the substrate, are developed and developed.

The achievement of the technical result is possible due to the following.

Firstly, the achievement in the process of self-formation and self-assembly of a precise spatial configuration of a nano-shell - a spring with its automatic placement in the micro-, nano-gap of the engine plates.

Secondly, the possibility of varying the spatial configuration of the nanoshell - the spring, its scaling in the direction of decreasing / increasing sizes from micrometers to nanometers.

Thirdly, nano-shells - springs are movable, flexible, elements characterized by high strength and shape stability when they are repeatedly exposed.

Fourth, the variety of shapes and sizes of nanoshells - springs, and the variety of properties of the materials used for their manufacture. The possibility of using materials with different physical properties for mechanically stressed layers in combination with precision setting of the shape and size of a nanoshell - a spring placed in the gap between the plates, allows for the controlled conversion of the applied electrostatic effect to mechanical displacement at any given scale scale.

Fifth, the internal structure of the structural layers of the nanoshell - the spring, which meets the condition of high structural perfection, which is especially relevant when scaling downwards.

The main distinguishing feature of the proposed electrostatic engine is that the approach to its implementation includes the use of self-formation processes initiated by etching of the sacrificial layer material, as mentioned above. A sacrificial layer is formed from a material selectively removed with respect to the material of the stressed film. To access the etchant to the sacrificial layer, in a grown heterostructure, for example, windows are made using lithography, through which the etchant penetrates the sacrificial layer and performs selective etching. In the manufacturing process of windows, a heterofilm is simultaneously structured. The latter means that after all layers of the heterofilm have been grown, windows are made in a single process and a film element is formed, the geometric configuration (figure) of which is determined later on when etching the sacrificial layer and transforming the detachable portion of the film element into a nanoshell - a spring, the shape of the latter . The film element in the simplest case (Figure 1) can be made in the form of a strip, at the ends of which there are no windows for access to the etchant, in this place the nanoshell - the spring is fixed to the plate (substrate).

The characteristic size of the controlledly created nanoshells - springs of various spatial configurations depends on the thickness and mechanical stresses in the initial heterofilm (see Fig. 1b)) and lies in the range, for a period from 10 nm to 100 μm, for a height from 10 μm to 1 nm, for thicknesses from 100 nm to 1 nm. In this case, it is possible to use a wide range of materials, the group of which, in the general case, includes materials with different physical properties, such as metals, semiconductors and dielectrics, and create from them hemispheres, corrugations and other nanoshells - springs with precision dimensions of up to several nanometers . Modern epitaxy allows complex heterostructures from semiconductor materials, GaAs, InAs, AlAs, Si, Ge, GaP, GaSb, InSb, GaN, InN and other materials, solid solutions based on them, metals, and dielectrics to be formed from individual monolayers, monolayer after monolayer. It is possible to grow both semiconductor heterostructures and hybrid ones: metal-semiconductor, semiconductor-dielectric.

The shape and size of the nanoshell - the spring is set at the stage of growing the heterofilm and forming a film element from it (or structuring the heterofilm). The formation of a blank of a nano-shell - spring, in a flat form, is carried out at the stage of creating a film element, multilayer or single-layer, which allows the use of a wide arsenal of methods and materials of planar technology. A unique feature of epitaxial strained films is the ability to achieve gigantic internal stresses (strains). Knowing the mismatch of the lattice parameters of materials and being able to grow solid solutions, one can strictly set the elastic stresses in heterofilms in the range from 0 to 10 GPa (pseudomorphic layers). This circumstance provides the accuracy of specifying the sizes and shapes of nanoshells - springs, and allows you to choose materials that correspond to the required working out of static impact. Consideration of the possibility of practicing electrostatic effects is carried out not only by achieving the required dimensions and shapes of the nanoshell - springs, but also by the conductive properties of the selected materials.

For example, for the case when the control voltage is applied to the plates, which also perform the function of electrodes, the nanoshell is a spring located between them must be non-conductive. For A ₃ B ₅ semiconductors, this condition is easily satisfied due to the fact that their undoped films are always depleted in charge carriers (the surface potential has a value of about 0.5 eV and the depletion region penetrates even in the film doped to a level of 10 ¹⁶ cm ^-3 to a depth of 300 nm, undoped films are non-conductive) and the contribution of their influence on the electric field between the plates is negligible. Experimental verification showed a very satisfactory operation of the nanoshells - springs made of an unalloyed depleted p-type film, while the plates were made of an n-type semiconductor. In the case when the nano-shell - spring performs not only the function of the spring, but also the function of the electrode, it is necessary either to heavily dope the initial heterofilm or to use a hybrid structure of a heavily doped semiconductor and metal. In particular, micro- or nano-shells - springs based on hybrid strained metal-semiconductor films, SiGe / Si / Cr, or metal-dielectric-semiconductor, SiGe / Si / Si ₃ N ₄ / Cr, in which The nano-shell itself, the spring, may be subjected to electrostatic effects, since it is capable of performing the function of an electrode (see Fig. 7).

для Si/Ge

GaP/InAs

Поэтому слой InGaAs на подложке GaAs и слой SiGe на подложке Ge в исходном состоянии сжаты. Важно отметить, что молекулярные слои, выращенные таким образом, могут быть контролируемо расположены на заданном расстоянии друг от друга и иметь строго заданное несоответствие параметров решетки, то есть заданную упругую деформацию.The internal mechanical stress is determined by the fact that the heterofilm is formed from single-crystal materials having various lattice constants. When growing such a heterofilm on a thick single-crystal substrate, the crystal lattices of the materials are adjusted to each other and the substrate lattice. In this case, elastic deformation of the heterostructure layers occurs - a layer of material with a greater lattice constant is compressed. Thus, the mismatch of the InAs / GaAs lattice parameters

for Si / Ge

GaP / InAs

Therefore, the InGaAs layer on the GaAs substrate and the SiGe layer on the Ge substrate are compressed in the initial state. It is important to note that the molecular layers grown in this way can be controllably located at a given distance from each other and have a strictly specified mismatch of the lattice parameters, i.e., a given elastic deformation.

The high internal perfection of the stressed layers of the initial heterofilm predetermines the accuracy of setting the local curvature of the nanoshell - the spring and, therefore, its shape.

High perfection of the internal structure, defect-free, uniformity of the material of the stressed layers is an important factor, as it allows the development of electrostatic effects in a controlled manner, with maximum efficiency.

Additionally, we note that the high internal perfection of the stressed layers of the nanoshell - the spring is an important factor in achieving the ability to scale the engine.

In the composition of the initial heterofilm, as the functional layers of the nano-shell-spring, there can be from one layer stressed relative to the substrate (plate) (see Figure 1) and more layers mechanically stressed relative to each other (see Figure 7).

Strength, easy deformability and shape stability of a nanoshell - spring is determined both by the direct result of its implementation in the composition of the layers held together by internal stresses, and by the perfection of the internal structure of mechanically stressed layers.

The thickness of each layer can be set in the range from several microns to one monoatomic layer (Fig. 14). The precision of the corrugation height is ensured by the fact that the nanoshell - the spring is limited by the substrate (fixed plate) and a layer of unstressed material of the moving plate, while the height is determined by the total thickness of the etched sacrificial layers located between the substrate and the upper unstressed layer of the moving plate, which is set during the epitaxial growth of structures with high precision.

а/а материалов функционального слоя и подложки:In the case of one functional layer strained relative to the substrate (plate) during the formation of the nanoshell - spring, the initial compressed layer, when released by etching the sacrificial layer from the bond with the plate, in the local region of length L, relaxes elastically, increasing its length and bulging to some height h. Taking the shape of the free film as a sinusoidal, from geometric considerations, we can deduce the dependence of the height h on the length L and the relative mismatch of the crystal lattices

a / a materials of the functional layer and the substrate:

а/а)^1/2.h = 1.3 L (

a / a) ^1/2 .

а/а, равном 5%, высота выпученной области на основании теории упругости составляет 1/3 от длины.At

a / a, equal to 5%, the height of the bulged region based on the theory of elasticity is 1/3 of the length.

The release of strained heterofilms from which a significant elastic energy is stored (of the order of 0.5 eV per atom!) And the inclusion of self-formation processes, as well as processes of self-assembly of complex structures in the game, opens up an unusually wide opportunity in the creation of micro-, nanomotors.

Of particular note is the technological compatibility of this technology with the technology for manufacturing integrated circuits, both in the first and second, using traditional methods of planar technology and materials, as well as the possibility of mass in-line production.

In addition to the considered simplest, in the form of one fold, extended corrugation, other forms of manufacturing a nano-shell - springs are possible. Consider the results of the practical implementation of other structures of a micro-, nanomotor.

On Fig presents the simplest edge corrugations. They can be formed upon release from communication with the substrate (fixed plate) of the marginal region of a stressfully compressed heterofilm of a film element made, for example, in the form of a strip. After liberation of the marginal region by etching the sacrificial layer laterally inward, the compressed film is unstable and corrugated. On Fig shows the edge corrugation of heterofilms with a thickness of less than 100 nm.

При этом

где а - постоянная решетки, а Δа/а - несоответствие постоянной решетки подложки и гетеропленки SiGe. Плоское состояние такой сжатой освобожденной полоски SiGe неустойчиво, в результате освобожденная прикраевая область приобретает синусоидальную форму, гофрируется. Выполненные эксперименты по изготовлению структур показали, что период и высота гофрировки пропорционально зависят от латеральной глубины травления. На Фиг.8, Фиг.9 а) видна связь между глубиной травления, шириной полоски, и периодом синусоидальной гофрировки края полоски. Такая закономерность наблюдалась нами на гетеропленках SiGe различной толщины от 20 нм до 3 нм при содержании Ge от 10% до 80%, соответственно.Consider one of the simplest cases (see Fig. 8 a)), which refers to heterostructures fabricated by molecular beam epitaxy on a Si substrate. A stiffly compressed SiGe film (with 40% Ge content) of a thickness of about 10 nm doped with boron to a concentration of 10 ²⁰ cm ^-3 (Ge lattice constant is 4% higher than the Si lattice constant) was grown on an undoped Si buffer layer. A high doping level prevented the etching of the material of the initial heterofilm in a 3% aqueous solution of ammonia. In this case, the undoped buffer layer and the n-type silicon substrate, which act as the sacrificial layer, were etched at a high speed. Selectively etching the buffer layer and the substrate to a depth of H in the lateral direction (in the above illustrations, the depth of lateral etching for different samples ranges from 5 μm to 500 nm), we obtained a freed strip of the near-edge region of SiGe with a width of H fixed on the substrate with one edge (cm Fig. 8 a)), opposite the edge, in relation to which the etching was carried out. The material released by the near-edge region of the SiGe strip tends to expand. The freed edge region of the strip with the initial length L becomes longer than its fixed edge by an amount

Wherein

where a is the lattice constant, and Δa / a is the mismatch between the lattice constant of the substrate and the SiGe heterofilm. The flat state of such a compressed liberated SiGe strip is unstable, as a result, the liberated edge region acquires a sinusoidal shape and is corrugated. The performed experiments on the fabrication of structures showed that the period and height of the corrugation are proportionally dependent on the lateral depth of etching. On Fig, Fig.9 a) shows the relationship between the depth of etching, the width of the strip, and the period of sinusoidal corrugation of the edge of the strip. We observed such a pattern on SiGe heterofilms of various thicknesses from 20 nm to 3 nm with a Ge content from 10% to 80%, respectively.

The revealed nature of the formation of edge corrugations also takes place for other materials, for example, InGaAs / GaAs heterofilms (see Fig. 8c). Samples with pseudomorphic InGaAs / AlAs / GaAs heterostructures were experimentally fabricated, where InGaAs is a functional layer in a compressed state, AlAs is a sacrificial layer that can be selectively removed by an etchant based on HF (with a selectivity of 10 ⁹ with respect to GaAs), GaAs - substrate (fixed plate). Selectively etching the sacrificial AlAs layer to a depth H in the lateral direction, a liberated strip of the edge region of the film element was obtained, the shape of which changed as described above. On figv) the periodicity of the corrugation of the edge of the InGaAs film is clearly visible. The corrugation period is -2 microns.

In the same way, sinusoidal corrugations with the required parameters can be obtained with high accuracy in the range from micron to nanometer sizes.

To obtain high-quality periodic corrugation, it is only necessary to form a smooth edge of the film element, which is quite achievable. Figure 9 a) illustrates the change in the geometric parameters of the sinusoidal corrugation with increasing lateral etching depth of the sacrificial layer.

Promising is the possibility of creating corrugated nanoshells-springs, elastically interacting with each other (Fig. 8 g) and d)). Elastic interaction allows you to synchronize the corrugations and create two-dimensional and three-dimensional lattices.

Fig. 8d) and e) shows an example of creating a system of elastically interacting corrugations. From the SiGe / Si and InGaAs / AlAs / GaAs heterostructures, film elements were made in the form of strips 10 μm wide, which were etched to obtain the depicted corrugations. The etching of the substrate and the buffer layer of the heterostructure with SiGe / Si (Fig.8d)) was carried out simultaneously from both edges of the strip of the film element, in depth towards its middle. Both edge regions of the strip, freed from communication with the substrate, acquire a sinusoidal corrugated shape. It is seen that the periodicity of the sinusoidal edges of the liberated strip is synchronized with a half-period shift. The observed self-organization is explained by the interaction of the elastic fields of the corrugated strip edges.

The fact is that the lateral front of etching of the sacrificial layer (substrate and buffer layer, which perform the function of the sacrificial layer) is not uniform. In the part of the film element where the heterofilm is freed from bonding with the substrate, the etching proceeds better than where the heterofilm is connected to the substrate and is in a planar state, as a result of which weak periodic modulation of the lateral depth of etching is observed. Also, while the total value of the lateral etching depths does not exceed the lateral size of the non-etched part of the sacrificial layer (substrate and buffer layer), the edges of the film are bent and corrugated independently of each other. As soon as the total value becomes equal to the non-etched part of the sacrificial layer, the etching fronts meet.

At the moment of the meeting of the etching fronts, the interaction of the fronts, causing the synchronization, begins.

The state when the bending maxima (upward bend) of the released heterofilm are located opposite each other is unstable. The system tends to a minimum of elastic energy, which is achieved by arranging the minima (bending down) against the maxima (bending up), which is synchronization. The resulting state is stable and static.

Thus, the near-edge regions of the strip of the film element, freed from both sides of the bond with the substrate, undergo two successive stages of self-organization. The first is the stage of independent periodic corrugation, of each of them detaching near-edge regions of the strip of the film element, the second is the stage of interconnected synchronization.

The same behavior pattern is observed upon etching of the sacrificial layer of the film element of InGaAs / AlAs / GaAs heterostructures.

Fig. 9 a) is a schematic illustration of the process of changing the corrugation period with increasing lateral etching depth. Presented in Fig. 9b), the experimental result was obtained on a sample of the SiGe / Si heterostructure; different etching depths in the same etchant are due to variations in the window width along the contour (edges) of the strip of the film element through which the etchant is accessible.

A wider window provides better etching access and provides greater lateral etching depth. In the presented photograph (Fig. 9b)), smaller corrugations are also clearly visible, the etching of the sacrificial layer (substrate and buffer layer) for which passed through narrow window lines.

Figure 10 shows the dome-shaped nano-shells - springs, which also play the role of non-linear springs placed in the gap between the plates (see Figure 10, a) -e)).

To make them (see Fig. 10d)) a thin, strained InAs film is pseudomorphically grown on a thick InP substrate, the growth direction is [001]. The condition of pseudomorphic growth allows us to assume that the crystal lattices of the materials of the strained film and the substrate are stitched without defects. The voltage in the film is due to the difference between the constant lattices of the film a _InAs = 0.606 nm and the substrate a _InP = 0.587 nm and the initial deformation of the film (a _{InP-a InAs} ) / a _InAs is approximately 3.1%. This leads to the fact that a giant compressive force of more than 4 GPa acts on the heterofilm held by the substrate in a flat state.

In most of our structures, the compressive stresses are many times, tens of times higher than the critical value at which the compressed flat film loses stability. Due to this, the rectangular region of the film element, freed from communication with the substrate, is bulging.

When the heterofilm is separated from the substrate and its transformation, the formed dome-shaped nano-shell - the spring is localized in a strictly defined volume limited by two planes of the movable and fixed plates (see Fig. 10a) -d)), the distance between which is set at the stage of molecular beam epitaxy, the first the stage of manufacture of the film element. During the formation of the dome, a situation may occur in which the heterofilm bulging out meets an obstacle in the form of the upper bounding plane of the movable plate, and during its further buckling under certain conditions, the bulging film will bend downward, similar to the case with extended corrugation. The implementation of the described situation depends on the specified values of mechanical stresses, thicknesses of the initial layers, the area of the area of the film element released from communication with the substrate. The above conditions are set at the stages of manufacturing the film element.

Using the above corrugations, laboratory models of micro-, nanomotors were made and tested.

11, photographs show experimental results showing a twofold decrease in the InGaAs corrugation period on a GaAs substrate (lower fixed plate) when it is compressed due to a change in the gap between the plates (upper movable plate is transparent). For clarity and convenience of observation, large-scale corrugations were specially selected using an optical microscope. It is clearly seen that the initial large corrugations with a maximum height (see Fig. 11a)) were transformed with doubling into corrugations of a lower height (see Fig. 11b)), but also being maximum for the reduced phase of deformation of the nanoshell - the spring. While the initial small corrugations visible from the other edge of the corrugation remained unchanged, since the loading by means of the upper movable plate parallel to the substrate did not affect the small corrugations. When the load is removed, an elastic transition to the initial state occurs with a time constant of less than 10 ^-7 sec.

S/h). При приложении к электродам напряжения более 5 В наблюдалось сначала медленное увеличение емкости, а при 11 В емкость резко возрастала в 1,5 раза, что соответствовало резкому уменьшению величины зазора, с 50 нм до почти 30 нм.Based on this structure, using the laid on plane-parallel upper plate, which acts as an electrode, a micro-, nanomotor model was made. The function of the second electrode was performed by a fixed lower plate (substrate). Applying voltage to the electrodes, we measured the capacitance of the structure. It was found that the initial capacitance of structure C corresponds to the gap between the plates (electrodes) h = 70 nm (C =

S / h). When a voltage of more than 5 V was applied to the electrodes, at first a slow increase in the capacitance was observed, and at 11 V the capacitance sharply increased by 1.5 times, which corresponded to a sharp decrease in the gap from 50 nm to almost 30 nm.

Devices with an overhead top movable plate (electrode) have disadvantages associated with the problems and difficulties of arranging the top plate parallel to the substrate, so the following experimental prototypes of the engine were made on a completely epitaxial precision structure (see Fig. 8, Fig. 9, Fig. 12, Fig. 16), with extended or edge corrugation.

The fabricated fully epitaxial precision InGaAs / GaAs structures on a GaAs substrate were investigated by scanning electron microscopy, and Fig. 12 shows schematic three-dimensional images and experimental photographic images of the cross section of such structures containing extended corrugations. The upper movable GaAs wafer is also formed epitaxially during the manufacturing of the film element at the stage of growing the heterofilm. The corrugation was formed as a result of the removal of the material of the sacrificial layers, between which a functional InGaAs corrugation layer was grown during molecular beam epitaxy (see Fig. 12, middle and lower parts. Fig. 15 and Fig. 16).

Longer corrugations of a more complex shape are shown in Figs. 13 and 14. Fig. 13a) shows a schematic representation of a zigzag long corrugation obtained by modulating the shape of the fold along its length (substrate width). On Fig shows the edge corrugations made around the perimeter of the quadrangle.

To characterize the corrugations in the plan, structures without a top movable plate (electrode) were specially formed, which made it possible to obtain optical, electron microscopic, and atomic force images (Fig.13b) -e). Fig.14, Fig.16c) and d)). The transition from zigzag extended corrugations with a micron period to zigzag extended corrugations with a nanometer period is carried out by reducing the thickness of the detachable stressed film with functional layers / layer and increasing mechanical stresses in it.

On figv) and d) shows photographs of the edge corrugations, for the observation of which the upper movable plate (film) has been removed. InGaAs / GaAs film structuring and etching of AlAs and AlGaAs sacrificial layers were performed through windows in the upper plate. The upper plate in this case, in contrast to the upper plate in the case of Fig.16a), initially contained an array of quadrangular windows (squares, see Fig.16c) and d)). Etching of the lower sacrificial layer along the perimeter of the windows led to the formation of the shown edge corrugations.

Note that modeling the shape and predetermining the functions of the nanoshell - the spring (corrugation) in the engine is also possible by performing it from a strained multilayer film, for example, containing at least one stretched layer (see Fig. 15). The corrugation shown in Fig. 15 serves as an electrode (see Fig. 15b)) in the engine shown in Fig. 7. The corrugation is made of a strained multilayer film containing three layers, the outer ones being compressed, and the film thickness periodically modulated by the outer layers, the modulation period of the thickness of one outer layer and the modulation period of the second outer layer are shifted relative to each other. An external periodically modulated layer made, in particular, of a conductive material, is nothing more than an electrode in the form of an array of conductive elements designed to create a local electric field or its gradient, providing a controlled change in the angle between the plates.

In order to turn an epitaxially grown heterostructure into an electrostatic micro-, nanomotor (see Fig. 7b) -d). Fig. 12, Fig. 16a)) using lithography form from the upper, for example, a conductive n-layer (see Fig. 7, position (2)) a plane-parallel substrate (1) a movable plate (2), performing, in particular, electrode function. The movable plate is held by the lateral regions of the structure using thin zigzag lateral springs (see Fig. 16a)). They are formed using lithography. On figa) along the edges of the upper movable plate are visible windows through which the material of the sacrificial layers is removed. Of fundamental importance in terms of the implementation of an engine made on the basis of this heteroepitaxial structure is that the upper movable plate — the electrode — is made of an n-type semiconductor, and the sacrificial AlAs layers and the strained InGaAs layer are lightly doped p-type layers. It is precisely because of this circumstance that the manufacture of an electrostatic micro-, nanomotor is simplified, and the built-in n-pn junction isolates the current areas of the upper electrode (as part of the upper movable plate) from the current areas of the lower electrode (as part of the fixed plate). These sites can be further irradiated with ions to improve insulation.

Tests of experimental engine mock-ups performed on a fully epitaxial precision heterostructure (see Fig. 7, Fig. 12, Fig. 16) with extended or edge corrugation showed the following results (see Fig. 17).

The experimentally obtained volt-farad characteristics (see Fig. 17) show a qualitative agreement between the above-described theoretical representation of the behavior of the engine model (see Fig. 3 and Fig. 4) with that obtained in practice (see Fig. 17a)). The capacitance C is related to the gap h between the plates by the dependence

where S is the area of the engine plates (about 1 mm);

C is the capacity of the structure;

h is the gap between the plates;

The spasmodic nature of the change in capacitance from voltage during forward and reverse (see Fig. 17a)) qualitatively confirms the spasmodic change in the number of corrugations (with their transformation into corrugations of lower height), as well as the stiffness of the nanoshell - spring when the critical value of the pressure force is reached as a result increasing the voltage applied to the plates, causing the plates to come together and reducing the gap between them. However, for quantitative confirmation, it is necessary to take into account the area of the edge corrugations, which is not exactly known for our experiment.

On Fig.17b) and c) shows the capacitance-voltage characteristics for an engine implemented on the edge corrugations shown in Fig.16 c) and d). One can see the absence of a sharp transition with an increase in the number of corrugations (doubling), since the structure simultaneously contained different corrugation heights (see Fig. 16d).

To assess the power of an electrostatic micro-, nanomotor, measurements were made of the capacitance-voltage characteristics of loaded engines, that is, the upper plate was loaded with various loads. Applying or relieving stress, multiple lowering or lifting of the load on the upper movable plate was performed. A similar pattern of motion of the upper movable plate takes place in the absence of load on it. The measured capacitance-voltage characteristics with and without loading of the upper movable plate (see Fig. 17c)) are of a similar nature, however, in the absence of load, a smaller displacement must be applied to move the upper plate by the same distance. Figv) is indicative of the fact that it directly demonstrates what load the engine can "carry".

The curve labeled “with load” was obtained by measuring the capacitance-voltage characteristic with additional mechanical pressure on the movable plate with a load of 1.2 grams. In terms of 1 cm ² this is 100 grams. The quantitative data presented are close to theoretical estimates, since the distance between the plates was about 700 nm, which is an order of magnitude greater than for the calculation results presented in Figure 4 (the force increases quadratically with decreasing distance). The calculations were performed for corrugations that completely fill the area under the electrode (plate). Experimental data were obtained for edge corrugations with an area substantially smaller than the plate area in an experimentally tested engine. Nevertheless, the experiment convincingly demonstrates the performance of the engine.

Thus, the possibility of precision formation of edge and extended corrugations with a period from microns to nanometers and the implementation of an electrostatic micro-, nanomotor has been experimentally shown.

Note that the created micro-, nanostructures are resistant to various factors. It has been established, for example, that when nano-shells are realized - springs using silicon and germanium, long-term high-temperature annealing (up to 600 ° C) of these structures does not lead to relaxation and mixing of the germanium-silicon solid solution with the adjacent layers and, therefore, does not change the bending radius of the shells . When choosing silicon as the base material for the manufacture of engines, it should be borne in mind that this material refers to biocompatible materials and is suitable for the manufacture of surgical devices.

The inventive device in the General case of its implementation contains (see Figure 2) a power source (not shown), a fixed plate (1) (substrate), a movable plate (2) and a nanoshell - a spring (3). The plates (1) and (2) are located relative to each other with a micro-, nano-gap. When an electrostatic effect is applied to the plates (1) and (2), they change the spatial orientation with respect to each other, for example, approach each other. In the micro-, nano-gap between the plates (1) and (2), a self-forming elastic nanoshell - a spring (3), which changes its shape and coefficient of elasticity when changing the relative position of the plates (1) and (2), is placed with fixation. It is made of mechanically strained film. The plates (1) and (2) and the nano-shell - spring (3), or the plates (1) and (2), or the plate (1) or (2) and the nano-shell - spring (3) are made with the possibility of application to them from the source power (not shown) voltage, and the development of electrostatic effects. The composition of the plates (1) and (2), nanoshells - springs (3) made electrodes. In the simplest case, the electrode is a layer of conductive material, metal or a heavily doped semiconductor, the layer is in electrical communication with the power source.

In the proposed micro-, nanomotor (Figure 2, Figure 7), the nanoshell - spring (3) is made corrugated (Figure 2, Figure 7 - Figure 14), or in the form of corrugation. The corrugation is fixed to the fixed plate (1) (substrate) by rigidly fixing its edges.

For the manufacture of nano-shells - springs (3) and plates (1) and (2) use a variety of materials. In particular, these are semiconductors, or metals, or dielectrics, or combinations of a semiconductor and a metal, or a dielectric and a metal, or a dielectric and a semiconductor, or a semiconductor, and a dielectric, and a metal.

In special cases, the implementation of micro-, nanomotors use a variety of forms of corrugations (see Figure 2, Figure 7 - Figure 15). So, the nano-shell - spring, can be corrugated unevenly with respect to its area, only at the edges, with an increase in the height of the corrugations towards the edges freed from communication with the plate (1) (Fig. 8, Fig. 9, Fig. 11 ) - edge corrugations. In another particular case, the nano-shell - the spring is corrugated evenly with respect to its area with a continuously periodic arrangement of extended identical corrugations (see Figure 2, Figure 7, Figure 12). In the third particular case of the implementation of the nanoshell - the spring is made corrugated evenly in relation to its area, with discontinuous or continuous periodic arrangement of extended zigzag corrugations (see Fig.13, Fig.14). Also, in the particular case of implementation, the nano-shell - spring can be corrugated evenly in relation to its area, with a discontinuously periodic arrangement of dome-shaped corrugations (Figure 10).

A mechanically stressed film of a nano-shell - spring can be multilayer or single-layer, contain, in addition to a compressed layer or several compressed layers, one or more stretched layers. In particular, it is made of a strained three-layer film with compressed outer layers (see Fig. 15), and its thickness is periodically modulated by the outer layers. On Fig shows the periodic modulation of the thickness of the outer compressed layers. The modulation period of one layer and the modulation period of the second layer are phase shifted relative to each other, for example, by 180 °.

Figure 2 and Figure 7 shows the micro-, nanomotors in cases of their implementation using plane-parallel plates. Other embodiments of the proposed engine are structures in which at least one of the plates is made in the form of a cantilever, or at least one of the plates is made in the form of an arch. The implementation of the upper movable arch-shaped plate of GaAs is shown in the experimental photograph of Fig. 12 in the lower right.

As a part of plates and nano-shells - springs, or as a part of plates, or as part of a plate and nano-shells - springs, when they are used as electrodes, the electrode in various special cases of engine realization can be formed as an array of elements. The specified form of the electrode is designed to create a local electric field or its gradient. So, for example, the electrode can be an array of parallel conductive strips, each of which is connected to a power source. As a result of applying this electrode configuration, a controlled change in the angle between the plates is provided, as in a torsion electrostatic engine (see Fig. 7). In the simple case, the electrodes are made in the form of strips of metal deposited on the surface of the plate. Another option is also possible when the plate consists of two layers, a semi-insulating and an n ⁺ -type, the n ⁺ -type layer being structured to obtain electrodes in the form of an array of elements.

Also, for example, an electrode consisting of plates (1) and (2) and nano-shells-springs (3) can be made in the form of an array of concentrically arranged conductive elements, each of which is electrically connected to a power source. The implementation of the electrode of the reduced form makes it possible to create a local electric field or its gradient along radial lines and / or along circles. Nano-shell - the spring is also performed with radial orientation of the corrugation axes. It can be realized in the form of edge corrugation, making a film element in the form of a circle and performing directional etching to its center.

In particular cases of the invention, the electrostatic micro-, nanomotor can be multi-stage. The engine shown, for example, in figure 2 or figure 7 is made single-stage. A multi-stage option means the series connection of two or more single-stage motors in n stages. In multi-stage execution, each of the plates of the nth cascade is made with the possibility of belonging to the cascade n-1 or the cascade n + 1. In other words, the upper movable plate of the first stage performs the function of the lower fixed plate of the second stage, the upper movable plate of the second stage serves as the lower fixed plate of the third stage, and so on. The number of cascades in a micro-, nanomotor, their location and specific forms of execution are set at the stage of growing a multilayer heteroepitaxial structure.

With respect to the movable plate, both in the single-stage and multi-stage versions of the engine, its movable fastening (see Fig. 16a)) is made lithographically to the fixed plate (substrate).

Nano-shell - the spring in relation to different stages can differ in thickness and / or height of the corrugation, and / or shape, and / or spatial orientation. By varying these parameters, precise motor control is possible in stages.

Micro-, nanomotor works as follows. Voltage is applied to the plates (1) and (2) (see FIG. 2) from the power source. The plates simultaneously serve as electrodes. While practicing the electrostatic effect, the plate (2) makes a movement relative to the fixed plate (1). As a result of the latter, an effect is formed on the nano-shell - the spring (3), leading to a change in its shape and increasing its stiffness coefficient, which prevents the adhesion of plates (electrodes) when making a significant movement. When the supply voltage is removed from the electrodes, the plate (2) makes a reverse stroke, and the nanoshell - the spring (3) takes its original shape.

In the case when the nano-shell - spring (3) is also an electrode, the electrostatic effect is worked out not only by the plates (1) and (2), but also by the corrugation (see Fig. 7 and Fig. 15).

A multistage engine works in a similar way, the voltage from the power source is supplied in relation to each of the cascades.

Claims (17)

1. Electrostatic micro-, nanomotor, containing a power source, at least two plates located relative to each other with a gap and with the possibility of changing due to the electrostatic effect of their spatial orientation relative to each other, characterized in that in the micro-, nano-gap between plates placed with the possibility of fixation self-forming elastic nano-shell - a spring made of a mechanically strained film that changes its shape and coefficient of elasticity with a change in mutual the location of the plates, while the plates and the nano-shell - spring, or plates, or the plate and the nano-shell are made with the possibility of applying to them from a power source voltage, and working out the electrostatic effect. 2. The electrostatic micro-, nanomotor according to claim 1, characterized in that the nano-shell - the spring is corrugated. 3. The electrostatic micro-, nanomotor according to claim 1, characterized in that the fixation of the nanoshell - spring is made by rigid attachment to the plate of its edges. 4. The electrostatic micro-, nanomotor according to claim 1, characterized in that the nanoshell is a spring made of a semiconductor, or a metal, or a dielectric, or a semiconductor and a metal, or a dielectric and a metal, or a dielectric and a semiconductor, or a semiconductor, and a dielectric, and metal. 5. The electrostatic micro-, nanomotor according to claim 1, characterized in that the plate is made of a semiconductor, or metal, or dielectric, or semiconductor and metal, or dielectric and metal, or dielectric and semiconductor, or semiconductor, and dielectric, and metal . 6. Electrostatic micro-, nanomotor according to claim 1, or 2, characterized in that the nanoshell - the spring is corrugated unevenly with respect to its area, only at the edges, with an increase in the height of the corrugations in the direction towards the edges freed from communication with the plate. 7. Electrostatic micro-, nanomotor according to claim 1 or 2, characterized in that the nanoshell - the spring is corrugated evenly in relation to its area with a continuously periodic arrangement of extended identical corrugations. 8. The electrostatic micro-, nanomotor according to claim 1 or 2, characterized in that the nanoshell - the spring is corrugated uniformly with respect to its area with a continuously or continuously periodic arrangement of extended zigzag corrugations. 9. The electrostatic micro-, nanomotor according to claim 1, characterized in that the nanoshell - the spring is corrugated uniformly with respect to its area, with a discontinuously periodic arrangement of dome-shaped corrugations. 10. The electrostatic micro-, nanomotor according to claim 1, characterized in that in the composition of the plates and nano-shells are springs, or in the composition of the plates or in the composition of the plate and nano-shells are springs, made with the possibility of using them as electrodes, an array of conductive elements designed to create a local electric field or its gradient, providing a controlled change in the angle between the plates. 11. The electrostatic micro-, nanomotor according to claim 10, characterized in that an array of concentrically arranged conductive elements is formed, with the possibility of creating a local electric field or its gradient along radial lines, and along circles, while the orientation of the axes of the corrugations of the nanoshell - spring is also made radial. 12. The electrostatic micro-, nanomotor according to claim 1, characterized in that it is made of multistage of n cascades connected in series, where n≥1, while each of the plates of the nth cascade is configured to belong to the cascade n-1 or cascade n +1 13. The electrostatic micro-, nanomotor according to claim 12, characterized in that in the multistage electrostatic micro-, nanomotor, the nanoshell - the spring with respect to different stages is made of different thickness and / or height of the corrugation, and / or shape, and / or spatial orientation for precise engine control in relation to different stages. 14. The electrostatic micro-, nanomotor according to claim 1, characterized in that the nanoshell is a spring made of a strained multilayer film containing at least one stretched layer. 15. The electrostatic micro-, nanomotor according to claim 1 or 14, characterized in that the spring nano-shell is made of a strained multilayer film containing three layers, the outer ones being compressed and the film thickness periodically modulated by the outer layers, and the modulation period is one thickness the outer layer and the modulation period of the second outer layer are shifted relative to each other. 16. The electrostatic micro-, nanomotor according to claim 1, characterized in that at least one of the plates is made in the form of a cantilever. 17. The electrostatic micro-, nanomotor according to claim 1, characterized in that at least one of the plates is made in the form of an arch.

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