JP2817082B2 - High temperature single electron tunneling structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high temperature single electron tunneling structure. More specifically, the present invention relates to an electron tunneling structure that can be formed at room temperature and is useful in various fields such as electronic devices such as a one-electron tunneling transistor having a new structure and ultra-fine processing.

[0002]

2. Description of the Related Art A scanning tunneling microscope (ST)
M) The development of technology has opened up new technological horizons as a means for observing the fine structure of the material surface. With the development of this technology, studies of the phenomenon of one-electron tunneling and its application are being advanced.

[0003] This single electron tunneling (Single Electron Tunneling)
Conventionally, as shown in FIG. 1, for example, a scanning tunneling microscope (STM) fine probe (1) and a metal particle (2) arranged through a minute gap,
This has been realized in a system of a metal oxide film (3) and a metal substrate (4). This one-electron tunneling (SET)
Is caused by the discretization of the chemical potential of the central electrode as the metal particles (2), and a unique iv curve is formed by this system. This curve is schematically shown in FIG. 2, which shows that the current changes every time the surplus charge of the center electrode increases or decreases.

Since this iv curve can be controlled by a gate, it is expected that the one-electron tunneling phenomenon can be applied as a new transistor or the like. However, there is a drawback that, for example, the one-electron tunneling structure illustrated in FIG. 1 cannot be realized unless the temperature is extremely low, for example, 4 K or less, depending on the knowledge and technology so far. For this reason, there is a serious obstacle to practical use in applying it to a new transistor or the like.

Therefore, the present invention solves the above-mentioned drawbacks of the prior art, and realizes one-electron tunneling in a higher temperature region at or near room temperature without being restricted by a cryogenic condition of 4 K or less. It aims to provide a new structure that can be used.

[0006]

In order to solve the above-mentioned problems, the present invention is characterized by sequentially arranging molecules and a substrate on a fine probe via a minute gap and performing one-electron tunneling. Provide high temperature single electron tunneling structure. Furthermore, in a preferred embodiment of the present invention, a molecule such as a liquid crystal that undergoes transition alignment near room temperature is provided as the molecule.

With this structure, without being restricted by the conventional cryogenic temperature condition of 4K or less,
For example, it is only possible to realize one-electron tunneling near room temperature. More specifically, whether or not one-electron tunneling (SET) is realized is determined by the magnitude relationship between the electrostatic energy (e ² / 2C) and the thermal energy (kT), where e is a physical fundamental constant. The electrostatic energy is the capacitance of the center electrode (C)
And the capacitance (C) is determined by the area of the central electrode. Therefore, if the material constituting the central electrode can be made a material having a smaller capacitance, the electrostatic energy larger than the thermal energy at room temperature Is formed, and one-electron tunneling occurs even at room temperature.

Therefore, in the present invention, instead of the conventional metal particles, material molecules are arranged in order to realize one-electron tunneling at room temperature. This molecule can be selected to produce a very large electrostatic energy upon injection of one electron. As a typical example,
Liquid crystal molecules can be exemplified. Of course, the present invention is not limited to liquid crystal molecules, and molecules having the above-mentioned characteristics may be selected and used.

In the case of liquid crystal molecules, it can be said that they are extremely useful for controlling one-electron tunneling by forming an alignment structure. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0010]

EXAMPLES Example 1 4'-n-alkyl-4-cyanobiphenyl (mCB;
m represents the number of carbon atoms of the alkyl group, and m = 5, 6, and 7)
Were used as configuration molecules. This molecular compound forms a smectic liquid crystal (LC) phase near room temperature.

The mCB as the liquid crystal molecules was disposed on the graphite surface. In this case, the outermost surface of graphite was stripped before use to expose a new surface. S
A metal wire was used as the TM probe. For each liquid crystal molecule, maintain at normal temperature and normal pressure so that it is slightly lower than its nematic phase transition temperature,
The STM image was observed, and the iv curve was measured. i
The -v characteristic was measured in a range of a bias voltage of -200 mV to 200 mV.

When 8CB, 10CB and 12CB having more carbon atoms than those described above are used as the mCB, a two-layer structure is observed. Was observed as an STM image. FIG. 3 shows an STM image of 5CB, and FIG.
CB, FIG. 5 shows an STM image of 7CB.

This is a 56 × 56 ASTM image. The alkyl moiety is represented darker than the cyanobiphenyl moiety. The set point current is 0.2 nA and the bias voltage is 1V. Incidentally, FIG. 4 suggests that 6CB has a quasi-single-layer structure and that the cyanobiphenyl groups are opposed. FIGS. 6, 7 and 8 each show:
It shows an iv curve in the case of 5CB, 6CB and 7CB, in which a multi-step curve is observed.

FIG. 6 shows a bias scan of 427 mV, a bias modulation of 50 mV, a set point current of 2 nA, a bias voltage of 1 V, and a sample period of 100.
μs. FIG. 7 shows the result at a set point current of 0.2 nA for 6 CB, and FIG. 8 shows the result at a set point current of 2 nA for 7 CB.
FIG. 9 is an iv curve when the probe is located above the alkyl group portion for 6CB, and FIG. 10 is an iv curve when the probe is located above the cyanobiphenyl group portion. In the latter case, it can be seen that a clear multi-step curve is observed. Example 2 In Example 1, the substrate was replaced with platinum, and molecules were provided on the surface of the platinum crystal.

In this case, a clearer step-shaped iv curve characteristic was obtained. Further, the substrate was changed to a metal such as Au, and similar STM observation and measurement of an iv curve were performed. Although the results were different depending on various combinations with the probe material, the effectiveness of using molecules was confirmed in the same manner as described above.

[0016]

As described in detail above, the present invention provides a new structure capable of achieving one-electron tunneling even at a high temperature near room temperature.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a conventional one-electron tunneling structure.

FIG. 2 is a conceptual diagram showing an iv curve in a one-electron tunneling phenomenon.

FIG. 3 is an STM image diagram of 5CB as an example.

FIG. 4 is an STM image diagram of 6CB.

FIG. 5 is an STM image diagram of 7CB.

FIG. 6 is an iv curve diagram of 5CB.

FIG. 7 is an iv curve diagram of 6CB.

FIG. 8 is an iv curve diagram of 7CB.

FIG. 9 is an iv curve diagram of the alkyl group portion of 6CB.

FIG. 10 is an iv curve diagram of a cyanobiphenyl group portion of 6CB.

Claims (3)

(57) [Claims] 1. A high-temperature, single-electron tunneling structure characterized in that molecules and a substrate are sequentially arranged on a fine probe through a minute gap to perform one-electron tunneling. 2. The structure according to claim 1, wherein the molecule is a transition orientation molecule near room temperature. 3. The structure of claim 2 , wherein the molecules are liquid crystal molecules.