JPH0789475B2 - Atom or molecule supply cylinder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing fine crystals by manipulating atoms or molecules.

[0002]

2. Description of the Related Art It is important and highly desired to freely manipulate atoms one by one to create a new crystal structure which has not been possible until now, because it is important for improving the performance of devices and developing new devices. It is a technique. Until now, STM has been used as a method for producing fine crystals by manipulating atoms one by one.
(Scanning Tunneling Micros
Cope: scanning tunneling microscope)
The probe was used for atomic manipulation. FIG. 3 shows a basic method of conventional atomic operation. The tip of the STM probe 4 having a sharp tip on the order of atoms is sharpened to the size of an atom. The atomic manipulation method is as follows. First, the STM probe 4 is moved to the atomic bath 5, and the atom 3 is captured at the tip of the probe. Next, the substrate is moved to a position on the substrate 2 where the crystal grows, and the atom 3 at the tip of the needle is ejected to place one atom at a predetermined position. By repeating this, a plurality of atoms are manipulated. (Eggler (D.
M. Eigler) and others, Nature
44, 524, 1990).

[0003]

However, in the above method, the distance between the atomic bath and the crystal growth site is large, and since the atoms are manipulated one by one, the movement of the probe between them is frequently performed. It has to be carried out, and there has been a problem that crystal growth requires an extremely long time. For example, in order to fabricate a fine crystal structure in a short time, a component that efficiently supplies one atom at a time is required, but such a component has not been known so far.

It is an object of the present invention to provide an atom supply component which can operate atoms one by one and in a short time.

According to the present invention, an atom or molecule once
By using carbon nanotubes with an inner diameter that allows one to pass through, it became possible to supply atoms one by one and continuously.

Also, one atom or molecule can pass through at a time
By providing a structure in which carbon nanotubes having a similar inner diameter are continuously connected to carbon nanotubes having a larger inner diameter , it is possible to more efficiently supply atoms or molecules .

When growing, a probe of a scanning tunnel microscope or an atomic force microscope is placed in the vicinity of the carbon nanotube, and the position to grow is specified by this probe. Also, if carbon nanotubes with a narrow band gap are used, an electric current can be passed through the tube, so the tube itself can be used as a probe for a scanning tunneling microscope.

Carbon nanotubes (hereinafter abbreviated as nanotubes or tubes) have a planar network network (graphite layer) having benzene shell-like hexagonal molecules formed by covalently bonding carbon atoms as constituent units. , A cylindrical polymer formed by rolling an atom or molecule into an inner diameter such that one atom or molecule can pass through at a time. It is chemically very stable and has low reactivity with other atoms. Therefore, it is possible to pass atoms through the nanotubes without causing a chemical reaction. Therefore, it is possible to form a crystal by placing a portion for crystal growth at the tip of the nanotube and continuously emitting atoms or molecules from the tip.

In the present invention, crystals are grown by supplying atoms and molecules from one end of the nanotube, passing through the tube, and discharging from the other end. Therefore, if the tip of the nanotube is brought to the portion where the crystal grows, atoms can be continuously emitted from the tip to form a crystal.

The emission of atoms can be accomplished by connecting the opposite end to an adapter that converts to a large inner diameter and connecting it to a pressure source of the vapor pressure of like atoms and molecules. . The adapter is manufactured as follows. For example, one end of cylindrical graphite is processed with an electron beam or an ion beam to form a hole having a size approximately equal to that of the carbon nanotube. The other end can be manufactured by dry etching or mechanically shaving, making a hole with a size of about several tens of μm or more deeply, and connecting both holes. To connect the adapter to the carbon nanotube, the carbon nanotube may be inserted into the hole of the adapter. Alternatively, the adapter with the holes as described above is placed in the chamber for growing the nanotubes with the small holes facing up, and the nanotubes are formed on the holes when the nanotubes are grown by discharge, CVD method, or the like. You can use it because you can create something. Further, as the pressure source of vapor pressure of atoms and molecules of the same kind, for example, in the case of metal, a molecular beam cell may be used. In other words, if you put metal in the crucible and heat it into a liquid state, metal vapor will be generated from it, so you can use it. In addition, a resistance wire is formed on the adapter and an electric current is applied to make it a heater.

To release atoms and molecules one by one, the following procedure should be performed. The minimum pressure released by atoms and molecules is investigated in advance, a pulse-like electric current is passed through the heater, and the vapor pressure is changed in pulses above and below this minimum vapor pressure.
Moreover, it is possible to release one atom at a time with one pulse by appropriately setting the upper and lower widths of the vapor pressure. The vertical width is determined as follows. First, try to release atoms and molecules with an appropriate vapor pressure of the upper and lower widths, and then STM, AFM (A
The atomic force microscope (Atomic Force Microscope) and the like are scanned to check how many atoms are emitted, and the feedback is used to determine the vertical width for emission of one atom.

In order to move the cylinder to the place where it is desired to discharge it, the following may be done.

Iijima et al. (Solid physics, Vol. 27 , p. 441,
1992), nanotubes have a diameter of 2 to
It is extremely fine, about 50 nm. Therefore, it is possible to approach a specific place of the crystal to such a distance . A probe such as an STM or AFM may be arranged in the vicinity of the nanotube, a specific location of the crystal may be found by the probe, and the nanotube may be moved back to the specific location by calculating backward from the distance between the nanotube and the probe. Since the moving distance is short, the moving time is shorter than that in the conventional example shown in FIG.
It should be noted that the nanotubes are wound on the graphy surface, but there are tubes with a narrow band gap, tubes with a wide band gap, and tubes in between, depending on the winding direction. If a narrow band gap semiconductor, that is, a narrow gap semiconductor, is used, current can be passed through the tube, and the supply cylinder itself is an STM.
It is not necessary to have both the STM and the supply cylinder, and the supply of atoms and molecules becomes more efficient.

Further, by using nanotubes having different inner diameters which are continuously connected, the atom supply efficiency can be further improved. Such nanotubes are
It occurs when a part of the six-membered ring structure is replaced by a five-membered ring or a seven-membered ring structure during tube growth. That is,
When the five-member ring entered, the tip of the tube tried to close,
When the seven-membered ring enters, the tip tries to widen. When the tip is closed or expanded to some extent and replaced with a six-membered ring structure again, nanotubes with different inner diameters can be continuously connected. Such a thing has been actually observed (Iijima et al., Solid State Physics, Vol. 27, 44).
1 page, 1992), you can select and use the one that suits your purpose. By using such a nanotube, atoms can be temporarily stored in a tube having a large inner diameter , so that atoms can be supplied with higher efficiency.

[0015]

EXAMPLE 1 An example of the present invention is shown in FIG. Prepare two cylinders provided close to each other, and supply Ga atoms 3 from one tube and As from the other tube (not shown) to form a fine pattern of GaAs on the single crystal GaAs substrate 2. Is an example of forming. Here, a tube having an inner diameter of about 1 nm was used. G
The Knudsen cell (K cell) used in MBE is used as a supply source of a and As. When using the K cell, it is better to face the substrate downward and the cylinder upward (in FIG. 1, they are drawn upside down for clarity). An adapter is placed on the cell, and vapors of Ga and As exiting from the cell are guided to the adapter and filled in a tube. Next, a place where the terrace structure exists on the surface of the substrate 2 is searched for by STM. This is because the place with the terrace structure becomes a stable site of atoms.
Next, the tube 1 is moved there, and an electric current is passed through the heater in a pulsed manner to heat the adapter for a moment to raise the vapor pressure therein and release one Ga atom. The released Ga atom is taken into the terrace. In the same way, As is also released and Ga
One As molecule is formed. Such a procedure is repeated to produce a fine structure.

Since the intervals between the tips of the two tubes can be made extremely close to each other, the movement of each tube to the crystal growth site can be performed in a very short time. Further, since it is possible to continuously release atoms without having to take them out from the atomic bath as in the conventional case, crystal growth can be performed in a short time.

Ga is used as an atom for producing a fine crystal.
It is also possible to use a substance that forms a solid by itself, or a substance such as a molecule of arsine (AsH3) that decomposes after being attached to a crystal. The raw materials are not limited to Ga and As, but Al, Ga and As
Can be used to form AlGaAs, and Al and Sb can be used to form AlSb, and it is easy to form a hetero fine structure. Further, it is obvious that not only compounds but also single element materials such as silicon and germanium can be prepared.

Although the tube 1 is inclined with respect to the substrate 2 in FIG. 1, the tube 1 may be vertically arranged. Being slanted is convenient when it is desired to form a fine structure on the slope.

(Embodiment 2) Another embodiment of the present invention is shown in FIG. When the nanotubes 1 and 10 having different inner diameters are continuously connected, the thin nanotube 1 is brought close to the substrate 2 and the atom 3 is emitted from the tip thereof. Nanotube with large inner diameter 1
If the inner diameter of 0 is set to, for example, about 100 angstroms, atoms can be temporarily stored. Therefore, even if the supply of atoms from the outside is stopped, a considerable amount of crystals can be grown using the atoms accumulated in the thick nanotube 10 for a while.

(Embodiment 3) In Embodiments 1 and 2, the STM was installed in the vicinity of the atom supply tube and movement was performed by this STM. However, if a narrow band gap semiconductor tube is used, the tube itself will be STM. Since it can be used as, the device becomes extremely simple.

[0021]

By using the atom / molecule supplying cylinder of the present invention, it is possible to carry out crystal growth by manipulating atoms and molecules one by one in a short time when producing a fine crystal structure or the like.

[0022]

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing an atomic manipulation method using a conventional STM probe.

[Explanation of symbols]

 1,10 carbon nanotube 2 substrate 3 atom 4 STM probe

Claims (4)

[Claims] 1. A cylinder for supplying atoms or molecules, wherein carbon nanotubes having an inner diameter such that one atom or molecule can pass through at a time are used as parts for supplying atoms or molecules one by one . 2. A carbon nanotube having an inner diameter that allows one atom or molecule to pass through at a time and a carbon nanotube having a larger inner diameter as a component for supplying atoms or molecules one by one. A cylinder for supplying atoms or molecules, characterized in that they are connected together electrically. 3. A cylinder for supplying atoms or molecules according to claim 1 or 2, wherein a probe of a scanning tunnel microscope or an atomic force microscope is arranged in the vicinity of the carbon nanotube, and a position to be grown by the probe is specified. . 4. The atom or molecule supplying cylinder according to claim 1, wherein the tube itself is used as a probe of a scanning tunneling microscope by using a carbon nanotube having a narrow band gap.