JPS6096599A - Production of superconductive thin film of oxide - Google Patents

Abstract

PURPOSE:To produce a superconductive thin film of a single cyrstal oxide having excelent electrical properties, by growing an oxide thin film having the same structure as the superconductive oxide on a saphire single crystal substrate, and growing the single crystal thin film of the superconductive oxide on the grown oxide thin film. CONSTITUTION:The thin film of an oxide (SrTiO3, BaTiO3, etc.) having a perowskite crystal structure same as that of a superconductive oxide BaPb1-xBixO3 (0.05<x<0.30) and having a lattice constant close to that of the superconductive oxide, is grown on a saphire single crystal by the epitaxial growth using a high- frequency magnetron sputtering process. The obtained product is used as the new substrate, and a thin film of the superconductive oxide is formed on the composite substrate by the epitaxial growth using a high-frequency magnetron sputtering process.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a method for producing an oxide superconductor thin film, and in particular, to a method for producing an oxide superconductor thin film, in particular an oxide BaPb1-XBIXO3 (0,0!;
0,30) (hereinafter abbreviated as BPB), it relates to a method for epitaxial growth of a crystalline thin film.

[Prior art]

Conventionally, when producing a BPB thin film by radio frequency (r, f-) magnetron sputtering, a sapphire single crystal was used as a substrate, which is relatively inexpensive, easy to handle, and physically and chemically stable. The thin film obtained on the substrate has a lattice mismatch near the interface with the substrate due to a mismatch in lattice constants and a difference in crystal symmetry between BPB and the substrate, resulting in low crystallinity. O These films, for example, BaPb□, 7 B16, which are formed by heat-treating a BPB thin film formed on a sapphire single crystal (8-sided) substrate at 0°C in a mixed gas atmosphere of oxygen and lead diluted In the case of a .303 thin film, as shown in FIG. 1, when the film thickness was less than 3 times θθX, the superconducting transition temperature Tc decreased as the film thickness decreased due to a decrease in crystallinity.

〔the purpose〕

Therefore, an object of the present invention is to solve the above-mentioned drawbacks.
To provide a method LIIM in which an oxide thin film having the same perovskite structure as BPB is epitaxially grown on a sapphire single crystal substrate and a BPB single crystal N film with good crystallinity is epitaxially grown on the new substrate.

[Structure of the invention]

In order to achieve such an objective, that is, to perform epitaxial growth of a BPB single crystal without impairing the physical and chemical stability of the sapphire single crystal as a substrate, the present invention uses a sapphire substrate. B on top of
Pepsiskite-type oxides with lattice constants and crystal symmetries close to PB, e.g. 5rTiOa, BaT10
3, KTaOa, (Sr, Ba)TiO
A laminated composite substrate on which a thin film of aw(Ca, 5r)T103, MgO, etc. is formed is used, and an epitaxial thin film of BPB is formed on the composite substrate.

The BPB'fII film obtained according to the present invention has a film thickness of J
It shows a high superconducting transition temperature even below θA, and has a higher quality BP than a BPB thin film fabricated directly on a sapphire substrate.
A B thin film is obtained.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

First, a film thickness of 300θ to 300θ was formed on the C-plane of a sapphire substrate (α-AJ203) by magneto-sensor battering.
Single-crystal 5rT103 thin films were formed with various values of θoo and X within the range. The sputtering conditions in this case are a mixed gas of 1% argon and Q% oxygen as the atmospheric gas, gas pressure APa, substrate temperature 1.30°C, applied voltage λ, 1IK.
The deposition rate was V/30 A/mln.

5rTIO3/α-AA'203 obtained by this
On top of the laminated composite substrate, BPB is further applied by R, F, and magnetron sputtering. P! gkθ~
Da! The product was multiplied by θθh. The BPH sputtering conditions at that time are argon! θ% and oxygen! The mixed gas with θ% is used as the atmospheric gas, and the gas pressure is ×/θ Torr.
s Substrate temperature details θ℃, applied voltage #KV, deposition rate 3oo
A/msn. 5rTi obtained in this way
03/(BPB on X-AJ203 laminated composite board
The thin film is strongly influenced by the orientation of 5rT103, and as seen in the XM diffraction pattern indicated by the dotted line l in Figure 2, it is oriented approximately in the (///) direction even in the so-called as-deposit state. . Furthermore, such a BPB i film was subjected to t in a mixed gas atmosphere of oxygen and lead oxide.
By heat treatment at AO°C for about 1 hour,
As shown by the solid line C in FIG. 2, a completely (///') oriented (C θ=77, Jgo) BPB thin film was obtained.

Regarding the BPII thin film thus obtained, the change in superconducting transition temperature Te with respect to the film thickness is as shown by the solid line 3 in FIG. In FIG. 3, the curved line indicated by the dotted line indicates the case of a conventional BPB thin film. Therefore, as can be seen from FIG. 3, even with the same film thickness, according to the present invention, the superconducting transition temperature Tc is higher than in the conventional case, and it is therefore confirmed that a thin film with good crystallinity can be obtained. It was done.

Instead of 5rTi03, )CI'a03, Ba
TiO3, Sr6, 68mg, 4T103.

Similarly, when a BPB thin film was deposited on a laminated composite substrate in which Ca□, 4 SrO, and 6 Ti03 were formed on a sapphire substrate, a nail crystalline thin film with uniform crystal orientation could be formed.

〔effect〕

As explained above, according to the present invention, five particles having the same perovskite crystal structure as BPB are formed on a sapphire substrate.
rTiOa e BaTi0a tK['aoa s
(Sr a Ba )TiOat(Cm , Sr
) By depositing a single-crystalline thin film of oxide such as Ti03 or MgO as an intermediate layer and forming a BPB thin film on top of it, the lattice constant and crystal symmetry between the substrate and BPB become close, so that the initial deposition This has the advantage that a single crystalline BPB thin film with good crystallinity and good electrical properties can be obtained.

[Brief explanation of the drawing]

Figure 1 is a characteristic curve diagram showing the change in superconducting transition temperature Te depending on the film thickness of a BPB thin film fabricated on a conventional sapphire single crystal (R plane). 5rTi03 was prepared as 5rTi03, and then alt=dep was prepared on it by r, f, magnetron sputtering.
Fig. 3 is an explanatory diagram of the X@ diffraction pattern of each BPB thin film after osite and heat treatment. FIG. 3 is a characteristic curve diagram showing a comparison of changes in superconducting transition temperature Tc with respect to film thickness of the produced BPB thin film. /... Xl5li1 diffraction pattern of am-deposit, C... Completely (/l/) oriented X-ray diffraction pattern, 3... BPB thin film according to the present invention, D... Conventional BPB thin film. Patent applicant Yoshi Tani, patent attorney representing Nippon Telegraph and Telephone Public Corporation −

Claims (1)

[Claims] Acetide superconductor BaPJ-xBIXo3 (θ, θ! < x <
θ, Jθ) In preparing the thin film, the thin film was prepared on a sapphire single crystal, which had the same Vero 1-skite crystal structure as BaPJ-1Biz03, and whose lattice constant was the same as that of BaPJ-2Biz03.
A method for producing an oxide superconductor thin film, characterized by growing a thin film of an oxide having a value close to 03, and epitaxially growing BaPJ-xnixo3 on the obtained composite substrate. , 2. In the IJI3+ production method of an oxide superconductor thin film according to claim 1, the oxide is SrTi.
O3, BaTiO3, KTaO3, (Sr, Ba)
TiOat(Ca, Sr) TiO3 or Mg
A method for producing an oxide superconductor N film characterized by Q.