JPH05259533A - Electronic element having resonance tunnel effect characteristics - Google Patents

Abstract

PURPOSE:To bear various characteristics by selecting the kinds of organic molecules to be used in a simple structure and at low cost. CONSTITUTION:A thin film comprising organic molecules, preferably organic semiconductor is formed on a conductive substrate 1. In such a constitution, when a probe 4 is arranged making a gap 3 to observe a tunnel current using the substrate 1 and the probe 4 as electrodes, the phenomena of increasing the tunnel current and making the organic molecules transparent can be observed by feeding the probe 4 with a potential corresponding to the energy equal to the molecular orbit given to the orbit of the organic molecular film. At this time, the title electrode element can be used as a negative resistance element having the current at this time making the negative resistance. In the concrete, in order to constitute the title element, a negative resistance element can be manufactured by arranging a conductor on both surfaces of a thin film element through the intermediary of an insulator body thin film so as to use this conductor as an electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state electronic device, and more particularly to a novel solid-state electronic device which can obtain a resonance tunnel effect characteristic by utilizing an organic molecular thin film.

[0002]

Resonant tunnel effect devices are already known as devices using a semiconductor superlattice structure. For example, GaA
It has been proposed to use the discrete electronic levels of subbands in a quantum well formed as a stack of thin film of compound semiconductor such as s, AlGaAs or the like having a thickness of several tens to several hundreds of angstroms as the resonance level. In order to obtain the tunnel resonance energy level, a plurality of compound semiconductors having different energy band gap widths are stacked with a quasi-atomic layer level accuracy to form a quantum well. However, it is extremely difficult and expensive to manufacture a semiconductor laminated film with an accuracy of several tens of angstroms. Further, there is a problem in that the accuracy is lowered due to technical difficulty, and there is a problem that it is difficult to obtain a target characteristic and poor reproducibility, and thus it is difficult to put it into practical use widely. Further, it was difficult to manufacture a device with high precision due to the manufacturing method, and it was difficult to obtain typical characteristics.

Here, the principle of the STM and the resonance tunnel effect will be described with reference to FIGS. Figure 1 is ST
It is a principle diagram of M (Scanning Tunnel Microscope). When the probe and the sample are brought close to each other in the range of about several angstroms to about 10 angstroms,
Under a voltage of a few v or less, a current flows even if the probe and the sample are not in contact with each other. This is called a tunnel current, but the current value naturally changes depending on the gap length between the probe and the sample. Therefore, the solid surface is approached (gap length is usually several angstroms) until the tunnel current flows through the probe and the sample, and the x and y planes are scanned by the piezoelectric element. At that time, the voltage applied to the piezoelectric element in the z direction through the feedback circuit is controlled so that the tunnel current becomes constant, so that the distance between the probe and the solid surface of the sample becomes constant. A map of the voltage applied to the piezoelectric element in the z direction is the STM image. Therefore, the surface shape of the sample can be obtained by this.

FIG. 2 is a principle diagram showing why a tunnel current flows. 2A to 2C, the vertical axis represents the energy level (which can also be expressed as voltage) and the horizontal axis represents the element thickness. a and c are tunnel barriers, b is a quantum well, and b ′ is a subband quantum level. FIG. 2A shows the case where the potentials at both ends of the device (the left and right electrodes, which correspond to the probe in the STM described above and the sample) are equal, and no current flows from the left side to the right side. When a potential difference is applied to both ends in such a state, a current flows out when the quantum level of the subband is lowered to reach the same level as the potential on the left side, but when the potential difference between both ends is further increased, the current decreases again. However, when the potential difference is still increased, the current again increases according to the strength of the electric field. This voltage-current characteristic is shown in FIG. Thus, the portion where the current decreases with increasing voltage can be used as a negative resistance element.

[0005]

DISCLOSURE OF THE INVENTION The present invention eliminates the drawbacks of the conventional resonant tunneling device composed of an inorganic multi-layered electrode thin film mainly composed of a semiconductor, and is simple to manufacture, inexpensive and usable. The object is to obtain an electronic device capable of selecting various characteristics by selecting the type of organic molecule to be used.

[0006]

SUMMARY OF THE INVENTION The present invention is basically a film of organic molecules, preferably organic semiconductor, formed on a metal or conductor substrate. This makes it possible to use the eigenvalue of the molecular orbital energy peculiar to the organic molecule, which is essentially different from the conventional one, as the resonance energy level.

In a device having such a structure, when a resonance tunnel current is observed through an organic molecular film, a tunnel corresponding to the energy corresponding to the molecular orbital energy of the orbit of the organic molecular film is applied to the STM probe. It was discovered that the current increased and the organic molecules became transparent in the tunnel image. The present invention further develops this, and an insulating film as a tunnel gap is provided on the upper and lower surfaces of an organic molecular thin film, and conductive layers are provided on both surfaces of the insulating film, and a resonant tunnel effect characteristic is also obtained by using this as an electrode. Is something that can be done. In addition, by providing a noble metal on both sides of the organic semiconductor thin film, an insulating layer as a Schottky barrier is formed at the interface between the noble metal and the organic semiconductor thin film, so that a conductive layer is provided on both sides of the organic molecular thin film via the insulating film. It is possible to obtain an element similar to the above element.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows the basic structure of the present invention. In the figure, the present invention relates to a case where an organic molecular thin film (preferably an organic semiconductor thin film) 2 is provided on a conductive substrate 1,
A gap is present between the probe 4 and the organic molecular thin film 2, and a potential difference is applied between the substrate 1 and the probe 4.
When the following experiment was performed using such a basic configuration, it was possible to observe that there was a resonance tunnel effect.

Experimental Example 1 Polysilane Styrene (commonly known as polysilane) was dissolved as an organic thin film on a cleaved surface of a single crystal of HOPG (Highly Oriented Pyrolitic Graphite) as a solvent, and the solution was spin-coated. Then, a film was formed. At this time, the spinner speed is 5
After rotating at 000 rpm (5000 rpm for 1 minute) for about 30 seconds to form a thin film, it was naturally dried for 12 hours. Film thickness is about 50
It is 0 angstrom. When the behavior of the tunnel current through the surface was observed through this organic film by using the principle of STM as shown in FIG. 3, that is, a voltage was applied between both electrodes using the HOPG substrate and the probe as electrodes. When the applied voltage was 1.5 v, the state of the surface of the organic molecule was seen as an STM image (see FIG. 4, full scale 80 Å). However, when the applied voltage was lowered to 0.3 v, an STM image of hexagonal coordination of carbon atoms of HOPG of the substrate was clearly revealed through the organic film (see FIG. 5, full scale 50 angstrom). After that, apply voltage again
When the voltage was increased to 1.5 v, the surface of the organic film appeared again, and the carbon atom array image disappeared and disappeared. This phenomenon has been shown to be reproducible. This phenomenon electrically means that the electric resistance decreases as the applied voltage decreases, and thus this element can be used as a negative resistance element or a non-linear element.

Considering this cause, it is considered that the molecular orbital energy of the organic molecule and the tunnel voltage (that is, the applied voltage) resonate with each other, so that the molecular film becomes transparent.
Therefore, using this principle, a resonant tunneling device can be obtained by stacking an organic molecular thin film on a substrate. Experimental Example 2 A thin film of Perylen as an organic semiconductor was formed on the cleaved surface of a HOPG single crystal by an evaporation method, and the structure shown in FIG. 3 was obtained to obtain the relationship between the tunnel voltage and the tunnel current (IV
Characteristics) was measured. The measurement results are as shown in FIG.
In this case, perylene is a P-type semiconductor and the tunnel voltage is defined as the voltage applied to the probe. The measurement was performed by bringing the probe close to the surface of the perylene film, which is an organic semiconductor thin film, within a few angstroms. In this graph, it can be seen that the probe voltage clearly shows a negative resistance characteristic in the range of applied voltage of about -0.75v to about -0.9v.

As described above, in the basic structure of the present invention, when the tunnel gap resistance and the thin film resistance of organic molecules are compared,
In general, the resistance value of the tunnel gap is considerably larger than that of the thin film, so that it is clear that more remarkable characteristics can be obtained by further reducing the resistance of the tunnel gap. Moreover, by selecting various thicknesses of the organic molecular thin film, it is possible to obtain those having different characteristics.

A modified example of the device using the above principle will be shown below. As shown in FIG. 7, a conductive substrate 1, an insulator thin film 5, an organic molecule thin film (preferably an organic semiconductor thin film) 2, an insulator thin film 6 and a conductor 4 are laminated, and the substrate 1 and the conductor 4 are used as electrodes. A voltage is applied between the electrodes. In the device having such a structure, the organic molecule thin film 2, the insulator thin films 5 and 6 between the conductor 4 and the substrate 1 form a tunnel gap, and thus the device easily operates as a resonance tunnel device from the above experimental example. It will be understood that it does. The structure of FIG. 7 shows the case where there are two tunnel gaps, but in comparison with the basic structure of the present invention, the structure in which the insulator thin film 5 between the substrate (conductor) 1 and the organic molecule thin film 2 is not present. It can be easily understood that the resonance tunnel effect can be obtained even with the above. In this case, a tunnel gap exists only between the upper conductor 4 and the organic molecular thin film 2.

As another modification, as shown in FIG. 8, a noble metal 7, an organic molecule thin film (preferably an organic semiconductor thin film) 2 and a noble metal 8 are further laminated on a substrate 1,
The noble metals 7 and 8 are used as electrodes. In such a structure, the Schottky barrier between the organic molecule thin film 2 and the noble metals 7 and 8 forms a tunnel gap. In this case, the tunnel gap resistance is shown in FIG.
There is a feature that it is possible to easily obtain a smaller size than that of the above. It should be noted that the substrate 1 in this configuration simply fixes the noble metal and the organic molecular thin film. Also in the configuration in FIG. 8, it is possible to omit the noble metal 7 between the substrate 1 and the organic molecular thin film 2, as in the case of FIG. 7. In this case, it is natural to use the substrate 1 as the lower electrode. It can be easily understood that the tunnel gap exists only between the upper noble metal 8 and the organic molecular thin film 2 in this structure.

As described above, a negative resistance element or a non-linear element can be obtained by various elements according to the present invention. Next, an example of a memory device using the element of the present invention will be shown. In the device having the structure shown in FIGS. 7 and 8, the upper and lower electrodes have a structure in which a large number of thin wires are arranged in parallel and the upper and lower thin wires are crossed, and the organic molecular thin film at the preselected intersection is, for example, high. Large-capacity ROM if it is deformed (for example, destroyed) by applying a voltage
Its use as (not shown) would be easily understood. When recalling the memory contents of this memory device, if a pulse voltage that causes a resonance tunnel effect is applied to the upper and lower thin lines, an output cannot be obtained because the intersection point where the organic molecular thin film is deformed is not conductive, but An output is obtained because the intersection that has not been deformed is conducting. Also, the output can be taken out in any manner depending on the usage of the storage device. For example, if so-called multiplexing driving is performed on the storage device having such a configuration, the intersection of the upper and lower fine lines can be scanned and output.

[0015]

As described above, according to the present invention, it is possible to obtain an inexpensive negative resistance element or non-linear element, which is simple in structure and manufacturing. It can also be used as a large-capacity storage element. Moreover, various characteristics can be selected by selecting the type of organic molecule to be used.

[Brief description of drawings]

FIG. 1 shows the basic configuration of an STM.

FIG. 2 is a principle diagram for explaining the resonance tunnel effect.

FIG. 3 is a basic configuration diagram of the present invention.

FIG. 4 is an STM image of the surface of an organic film (polysilane).

FIG. 5: STM image of carbon atom arrangement on substrate

FIG. 6 shows measurement results of IV characteristics.

FIG. 7 is a structural diagram in which an insulator thin film according to the present invention is used as a tunnel gap.

FIG. 8 is a configuration diagram in which a Schottky barrier according to the present invention is used as a tunnel gap.

[Explanation of symbols]

 1 substrate 2 organic molecule thin film 3 gap 4 probe 5, 6 insulator thin film 7, 8 noble metal

Claims (6)

[Claims] 1. An electronic device comprising a substrate and an organic molecular thin film formed on the substrate, and causing a resonance tunnel effect. 2. A probe having a substrate, an organic molecular thin film formed on the substrate, and fine tips arranged close to the surface of the thin film, and a three-dimensionally operable probe. An electronic device characterized in that a voltage is applied between a substrate and the probe to generate a tunnel current. 3. An electronic device having conductive electrodes attached to both sides of an organic molecular thin film, wherein the conductive electrodes are attached via a tunnel gap layer on at least one side of the organic molecular thin film. Characteristic electronic device. 4. The electronic device according to claim 3, wherein the tunnel gap layer is made of an insulating thin film. 5. The conductive electrode is made of a noble metal, and the tunnel gap layer is made of a Schottky barrier formed at the interface between the noble metal and the organic molecule thin film by directly attaching the noble metal and the organic molecule thin film. The electronic device according to claim 3, wherein: 6. The conductive electrode comprises a plurality of thin wires,
4. The plurality of thin wires are arranged in parallel, and the upper surface thin wires and the lower surface thin wires intersect each other.
The electronic device according to 1.