Background
Atomic Force Microscope (AFM), a scientific instrument with high resolution invented only in 1986, has been widely used in the fields of chemistry, biology, physics, and materials science, and in the industrial fields of semiconductors, integrated circuits, etc. The AFM has atomic-level spatial resolution, has various imaging modes, can represent the microscopic morphology of the surface of a material, and can also represent the electromagnetic property of the material; in addition, the interaction force between the needle tip and the sample can be used for representing the mechanical properties of the surface of the material, such as elastic modulus, viscous force and friction property; meanwhile, the device can work in air, liquid and vacuum environments.
One of the key components of AFM to achieve high resolution detection is the probe. The probe mainly comprises a substrate, a micro-cantilever and a needle tip, wherein in the testing process, the needle tip is contacted with the surface of a sample to generate an interaction force, so that the micro-cantilever of the probe is bent, and various information is obtained by detecting the bending size of the micro-cantilever. The parameters and precision of the probe have an important influence on the test result, and the conventional commercial probe is a substrate-micro cantilever-tip integrated structure which is processed by using semiconductor materials through etching, deposition and other technologies. The sharp needle tip is positioned at the free end of the micro-cantilever, the needle tip is generally in a shape of a four-cone or a cone, and the curvature radius is from several nanometers to dozens of nanometers. The main tip materials are silicon, silicon nitride and certain metals.
There has been a great deal of interest in the study of mechanical properties between specific materials, such as the interaction between drug particles and cells, and the desired results cannot be directly obtained using conventional commercial probes and colloidal probes. Thus, there will also be some spherical colloidal probes. The diameter of the used small ball is generally from several micrometers to dozens of micrometers, the small ball is adhered to the cantilever without the needle point through glue under an optical microscope, and the prepared needle point has a larger contact area with a sample. The chinese patent publication No. CN107796958A proposes a method for preparing a 30-100 micron probe, and for such micron colloidal particles with larger size, it is easier to adhere to the cantilever under an optical microscope.
However, for submicron particles, the optical microscope is not sufficiently magnified to directly observe the position of the particle, and the thickness of the glue on the microcantilever, if larger, may cover the submicron particles with excess glue, resulting in a change in the surface material properties of the particles.
Therefore, those skilled in the art are dedicated to provide a method for preparing a submicron probe for an atomic force microscope, and the problems of insufficient resolution and inconvenient operation of submicron particles in the existing preparation method are solved.
Disclosure of Invention
In view of the defects in the prior art, the technical problem to be solved by the invention is how to provide a method for preparing a submicron probe for an atomic force microscope, which can improve the resolution and is convenient to operate.
In order to achieve the aim, the invention provides a preparation method of a submicron probe for an atomic force microscope, which comprises the following steps:
step 1, cutting the front end of a micro-cantilever probe into a platform by a Focused Ion Beam (FIB) technology;
step 2, uniformly dispersing the microspherical particles for preparing the probe on a silicon chip;
step 3, lightly contacting the mechanical arm with the microspherical particles to enable the microspherical particles to be adsorbed on the surface of the mechanical arm;
step 4, moving the manipulator to enable the manipulator to be close to the surface of the probe, so that the microspherical particles are adsorbed on the surface of the probe;
and 5, utilizing an ion source to fix the microspherical particles on the surface of the probe.
Further, the micro-cantilever of the micro-cantilever probe in the step 1 is a micro-cantilever with a tip, a triangular micro-cantilever or a rectangular micro-cantilever.
Further, the width of the platform in the step 1 is 1-2 times of the diameter of the microsphere particles.
Further, the step 2 specifically includes the following steps:
2.1, sequentially placing the microspherical particles for preparing the probe in an acetone and ethanol solution for ultrasonic cleaning, and placing the cleaned microspherical particles in ethanol or water dispersion for storage for later use;
2.2, sequentially placing the polished silicon wafer in acetone, ethanol and deionized water for ultrasonic cleaning, and finally blowing the cleaned silicon wafer for later use by using pure nitrogen;
and 2.3, dropping a drop of the dispersion liquid with the microsphere particles obtained in the step 2.1 on the silicon wafer treated in the step 2.2, and drying for later use.
Further, in the step 3, the microspheroidal particles are adsorbed on the surface of the manipulator through electrostatic interaction.
Further, in the step 4, the microspheroidal particles are transferred and adsorbed on the surface of the probe through electrostatic interaction.
Further, in the step 2, the microspheroidal particles are uniformly dispersed on the silicon chip so that the microspheroidal particles are not affected with each other when being bonded to the probe.
Furthermore, the microspherical particles are spherical or lamellar particles with the size of 100-1000 nm.
Preferably, the microspheroidal particle is a silica bead or an organic drug particle.
The invention also provides a submicron probe for the atomic force microscope, which is obtained by the method for preparing the submicron probe for the atomic force microscope by the FIB technology.
The invention has at least the following beneficial technical effects:
1. the preparation method of the submicron probe for the atomic force microscope provided by the invention utilizes a scanning electron microscope-focused ion beam (SEM-FIB) technology, and has the advantages of high resolution, precise operation, convenience and intuition.
2. The preparation method of the submicron probe for the atomic force microscope provided by the invention can be used for processing commercial sharp probes, the materials are convenient to obtain, and the production cost is reduced.
3. The preparation method of the submicron probe for the atomic force microscope can prepare submicron particle probes with various shapes and properties, has wide application, can be used for detecting mechanical properties such as interaction force and friction between particle materials and other materials under different environmental conditions, and can also be used in the fields of life science, material science and the like.
The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.
Detailed Description
The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.
In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views.
As shown in fig. 1, in a preferred embodiment of the present invention, a method for preparing a submicron probe for an atomic force microscope includes the following steps:
step 1, cutting the front end of a micro-cantilever probe into a platform by a Focused Ion Beam (FIB) technology;
in a preferred embodiment of the present invention, the micro-cantilever of the micro-cantilever probe is a micro-cantilever with a tip, a triangular micro-cantilever or a rectangular micro-cantilever; the width of the platform after cutting is 1-2 times of the diameter of the microsphere particles.
Step 2, uniformly dispersing the microspherical particles for preparing the probe on a silicon chip;
in a preferred embodiment of the invention, the microspherical particles are spherical or lamellar particles with the size of 100-1000 nm, preferably silicon dioxide spheres or organic drug particles; the uniform dispersion of the microspheroidal particles on the silicon wafer is such that the microspheroidal particles do not interact when they are bonded to the probe.
The step 2 specifically comprises the following steps:
2.1, sequentially placing the microspherical particles for preparing the probe in an acetone and ethanol solution for ultrasonic cleaning, and placing the cleaned microspherical particles in ethanol or water dispersion for storage for later use;
2.2, sequentially placing the polished silicon wafer in acetone, ethanol and deionized water for ultrasonic cleaning, and finally blowing the cleaned silicon wafer for later use by using pure nitrogen;
and 2.3, dropping a drop of the dispersion liquid with the microsphere particles obtained in the step 2.1 on the silicon wafer treated in the step 2.2, and drying for later use.
Step 3, lightly contacting the mechanical arm with the microspherical particles to enable the microspherical particles to be adsorbed on the surface of the mechanical arm;
in a preferred embodiment of the present invention, the microspheroidal particles are electrostatically attracted to the surface of the robot.
Step 4, moving the mechanical arm to be close to the surface of the probe so as to enable the microspherical particles to be adsorbed on the surface of the probe;
in a preferred embodiment of the present invention, the microspheroidal particles are electrostatically attracted to the surface of the probe.
And 5, utilizing an ion source to fix the microspherical particles on the surface of the probe.
Fig. 2-4 are process diagrams illustrating the preparation of a submicron probe according to another preferred embodiment of the present invention. As shown in fig. 2 and 3, the microcantilever probe with a sharp tip was cut using FIB techniques to form a mesa with a width of 1 micron. As shown in fig. 4, after the surface of the manipulator adsorbs the microspheroidal particles through electrostatic interaction, when the manipulator is moved to the surface of the probe, the microspheroidal particles are transferred and adsorbed on the surface of the probe through electrostatic interaction, and then the microspheroidal particles are immobilized on the surface of the probe by using the ion source.
As shown in fig. 4, the present invention also provides a submicron probe for an atomic force microscope obtained by a method of preparing a submicron probe for an atomic force microscope by FIB technology.
The preparation method of the submicron probe for the atomic force microscope provided by the invention utilizes the SEM-FIB technology, and has the advantages of high resolution, precise, convenient and visual operation; the commercial sharp probe is processed, the material is convenient to obtain, and the production cost is reduced; the invention can prepare submicron particle probes with various shapes and properties and has wide application.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.