JPH0328190A - Lb film substrate - Google Patents

Abstract

PURPOSE:To readily form a homogeneous ultrathin film of a single crystal without requiring regulation of substrate temperature or selection of a substrate excellent in conformity by growing a thin film of the single crystal on an Langmuir-Blodgett(LB) film substrate. CONSTITUTION:A monomolecular film, such as stearic acid, is formed on the surface of water and compressed to a desired surface density with a barrier. In the process, the distance between mutual molecules constituting the LB film is set so as to be equal to the lattice constant of a substance from which a crystal is to be grown or a multiple of an integer thereof. Monomolecular films are then cumulated on a glass substrate, etc., to prepare the LB film. The number of cumulation is such that the homogeneity of the surface is improved. The resultant film is used as a substrate to grow a single crystal thin film, such as metal, semiconductor or oxide high temperature superconductor, by a vacuum deposition, sputtering, CVD method, etc. Thereby, the substrate sticking to the LB film substrate is not converted into an island-like structure. As a result, an ultrathin film excellent in crystallinity can be formed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to thin film crystal growth, and is particularly suitable for uniformly growing metals, semiconductors, oxide high temperature superconductors, etc. on a substrate. This invention relates to an LB film substrate whose consistency can be changed by changing the molecular surface density of the LB film. [Prior art] For a description of thin films, see pages 65 to 70 of Physical Engineering Experiment 5 "Basic Technology of Thin Films" by Awa Kanehara, University of Tokyo Press, (May 20, 1965, 8th edition). and 11 pages 115 and 115. Thin films made by vacuum evaporation or sputtering are described in 6 of the same document.
7. As seen in the electron micrograph on page 68, this is an island-like structure that gradually grows and sticks together. Therefore, it inevitably becomes a collection of many crystal grains,
Many grain boundaries enter. Therefore, thin films formed by these methods are often polycrystalline thin films. [Problem to be solved by the invention] In the above-mentioned prior art, the easiest method was to form a polycrystalline thin film. However, from the basic standpoint of thin film research, there is a deep interest in single crystal thin films, and this is also necessary for semiconductor device fabrication. In order to specifically grow single-crystal thin films, it was necessary to select a substrate with good lattice constant matching with the material to be grown, and to perform heat treatment. Matching the lattice constant using crystal cleavage planes is
The problem was that the number of specific products was limited, and the boards themselves were expensive. Further, it has been found through observation of electron \@*lA photographs that thin films made by vacuum evaporation or sputtering have an island-like structure when the film thickness is several tens of λ. In other words, it has been difficult to produce a uniform ultra-thin film (for this purpose, an appropriate substrate, appropriate temperature, and appropriate evaporation rate must be selected).

The electrical properties of a thin film with an island structure are quite different from those in the bulk state. The electrical resistivity is high compared to the bulk value, and the residual resistance ratio RRR at extremely low temperatures is also small. A problem with superconducting materials is that when they become ultra-thin films, the superconducting transition temperature 'I' c decreases, and the value of the critical current density Jc also decreases. The purpose of the present invention is to grow a single-crystal thin film on a substrate without adjusting the substrate temperature or selecting a well-matched substrate. Another object of the present invention is to prevent formation of an island-like structure when producing an ultra-thin film with a film thickness of several 1 OA to several 100 OA. [Means for Solving the Problems] In order to achieve the above object, an LB film, which can change the molecular surface density and can have a metal salt on the surface, is used as a substrate. Or LB of organometallic complex
The membrane is used as a substrate. There are an almost infinite number of molecules that make up the LB membrane, and by subtly changing their molecular weights, it is possible to freely adjust the intermolecular distance. Examples of materials for the rB film include fatty acids such as stearic acid, alcohols, esters, diacetylene derivatives (which also form polymers), phthalocyanine derivatives, pigments such as merocyanine and hemicyanine, and organometallic complexes. Metals used for metal salts include ゛Li, Cu, Cd.
, Ba;'Ca, Pb, -}'e, Afi, etc., but it is known that metal salts with a high valence generally form a hard LB film. The oxide high-temperature superconducting material to be grown as a single crystal basically contains a two-dimensional copper-oxygen lattice, including Cu, O
In addition to 'I' Q , - B i , L a ,
Y, S r, yb, Lu, 'I'm, Dy, Sc, C
e. Pr, Nd, Srri, Eu, Gd, ′l”b
, Ho, Er, Sr, Ha, Ca, and Mg. [Operation] First, a monomolecular film is created on the water surface and compressed with a barrier to the desired areal density.At this time, the distance between the molecules that make up LHW4 is determined by the lattice of the substance whose crystal is to be lengthened. Make it equal to a constant or an integral multiple of it. In other words, the density can be changed by adjusting the surface pressure of the monolayer. However, when it contains a polyvalent metal salt, the valence increases even more. Also, by changing the molecular weight of the molecules forming the film, you can subtly adjust the intermolecular distance! It is Noh. Next, a monomolecular film is accumulated on a glass substrate or the like to produce an LB film. The cumulative number is until the uniformity of the surface becomes good, and if this is satisfied, one layer may be sufficient. When using metal salt parts, accumulate them so that the hydrophilic groups are on the surface. In the case of 1 layer, it is sufficient to hydrophobically treat the glass substrate.There are two general methods of accumulation: the vertical dipping method and the horizontal adhesion method, but the latter method is more sensitive to changes in density during accumulation. This is suitable because it is difficult to attach and the parent wood becomes the surface of the board. The specific accumulation method is described in the above-mentioned “Kagaku Review Review No. 40, 1983,
(Edited by the Chemical Society of Japan, published by the Society Publishing Center) Published on pages 83 and 84 of J. Using this as a substrate, vacuum evaporation, sputtering, carbon
Grow single M thin films such as Kinarashi, semiconductors, P & compound high temperature superconductors, etc. using the VL) method. The metal salt on the surface of the LB film can be considered to have already been produced as a uniform ultra-thin metal film of a single atomic layer. Therefore, the substance attached to the LH film substrate does not form an island-like structure, and an ultra-thin film with good crystallinity is formed. In addition, oxide high-temperature superconductors contain a copper-oxygen lattice in the substrate, and if the copper salt (C=O)O-Cu+ is prepared using a molecule containing a carboxyl group, consistency can be achieved. gets better.

〔Example〕

Embodiment 1 of the present invention will be explained below with reference to the drawings. First, stearic acid (C tt
A monomolecular film of H ss C O OH (see Figure 1(a)) is prepared on the water surface. The aqueous phase is ultrapure water (~17MΩ
al), the composition of which is PbCQx: 10 Ichiban M,
F e C Q x : 1 0 −' M t H
CQ: 2 X 1 0 -' M +K1:5X1
It is 0-5M. The pH is 5 and the temperature is room temperature.
(CtyHasCOO−)zPb+” intermolecular distance is p
Adjust the surface pressure of the monolayer so that it becomes an integral multiple of the lattice constant of b. C'rAB (Cetyl Trimethylammonium Bromide)
m Bro+wide, C Ha (CHz) N+
A glass substrate was hydrophobically treated with (CHs)sBr-), and LH[ of the Fb salt of steering acid was prepared by the horizontal deposition method so that the molecular surface density remained the same as the value set on the water surface. This L}! A pbfJI film was fabricated on a film substrate by sputtering. A schematic diagram of the ultra-thin film fabricated using this method is shown in Figure 1(b). When an ultra-thin film of tens to hundreds of layers is fabricated on a glass substrate without Ll3 film, Pb grows into an island-like structure as shown in the second country, and the electrical resistivity decreases compared to the bulk value. rise very much. However, if an LH film substrate is used, the electrical resistivity does not change much even if an ultra-thin film is produced. FIG. 3 is a measurement diagram of resistivity in which the above comparison was made.

Even when AQ was formed on the Afi salt stearic acid L}S film substrate by the sputtering method, an ultra-thin film with low electrical resistivity could be similarly obtained. Next, Example 2 will be described. Figure 4 shows LHIIQ of ester derivatives of ferrocene. It is known that in double-stranded derivatives, the cyclobentadiene rings are oriented perpendicular to the membrane surface. This LB film was produced in the same manner as in Example 1. An Fe# film was fabricated on this LB film substrate by vacuum evaporation. As a result, an ultra-thin film with a bcc structure was obtained. Next, Example 3 will be explained. Polydiacetylane (see Figure 5) LB
A single crystal thin film of an oxide high temperature superconductor was grown on a membrane substrate. First, the diacetylene derivative heptacosa-10, which is the monomer or film molecule of the polydiacetylene LH film, is
．． 1 2 -diynoid acid(;Ha(
CHz)zδ-CmiC-CmiC ((;Hz)acO
A monomolecular film of o-H+ was prepared on the water surface. The composition of the aqueous phase was Cu(;I2: 10-''8M. A boridiacetylene monomolecular film was formed on the water surface by irradiation with ultraviolet rays.Other conditions were the same as in Example 1 to produce an LB film. Oxide high temperature superconductor YHa on polydiacetylene LB film substrate
A thin film of zCugO7-δ was produced by a sputtering method. As a result of measuring the superconducting transition temperature Tc, the value was almost the same as that of a thin film fabricated on a Sr1"i0s substrate with good consistency. The measurement results of X-ray diffraction also indicate that a film with good orientation was obtained. I understand.

Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to these embodiments as long as it does not depart from the spirit of the present invention. Not limited to the above. [Effects of the Invention] According to the present invention, it is possible to obtain a low electrical resistivity close to the bulk value in an ultra-thin metal film made up of several tens to hundreds of people. Single crystal growth is also possible by adjusting the molecular surface density. It is also effective in producing thin single crystals of oxide high temperature superconductors.

[Brief explanation of drawings]

Fig. 1 (a) is a diagram showing the structural formula and molecular model of steering acid, Fig. 1 (b) is a schematic side view of an embodiment of the present invention, and Fig. 2 is a normally seen island-like structure of a thin film. FIG. 3 is a measurement diagram showing the thickness dependence of the electrical resistivity of the PB thin film according to the present invention, FIG. 4 is a diagram showing the structural formula of the ester derivative of ferrocene, and FIG. This is a diagram showing the structural formula of acetylene. Fig. 2 Fig. 3) 11 4 (A冫VJl1!1 (ku)

Claims (1)

[Claims] 1. An LB film substrate on which a single crystal thin film is grown. 2. The LB film substrate according to claim 1, wherein the LB film is an organometallic complex or has a metal salt on the surface, and a single crystal thin film is grown on the surface. 3. The LB according to claim 2, wherein the LB film is an organometallic complex or has a metal salt on the surface, and a single crystal thin film of an oxide high temperature superconductor is grown on the surface.
membrane substrate. 4. The LB film according to claim 1 or 2, wherein the LB film is an organometallic complex or has a metal salt on the surface, and a single crystal thin film of the metal or a compound containing the metal is grown. membrane substrate. 5. Claim 4, wherein the LB film is an organometallic complex or has a metal salt on the surface, and a single crystal thin film of the metal or an oxide high temperature superconductor containing the metal is grown. The LB film substrate described. 6. The LB film substrate according to claim 4, wherein the LB film has a copper salt on its surface, and a single crystal thin film of an oxide high temperature superconductor is grown on that surface. 7. A method for forming a single crystal film, characterized by growing it on an LB film.