JPH025582A - Manufacture of superconducting thin film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for manufacturing a superconducting thin film.

Superconductors utilize the property of having zero electrical resistance to
For wiring of strong magnetic field generators and semiconductor devices.

It is also used as a high-speed switching element that utilizes the Josephson effect, and as a micromagnetic field or electric field sensor.

Conventional technologySuperconductors have great utility as thin films.Ceramics, single crystals, amorphous materials, metals, etc. are used for thin film substrates, but when creating oxide thin films, the type and creation of the substrate Depending on the conditions.

Crystal orientation is easily changed. TI, Ba, Ca
, Cu oxide superconductor is orthorhombic, (RE)
It has a crystal structure similar to that of BaaCusO□21-based superconductors (RE is a rare earth element), and it is estimated that current flows easily in the (100) and (010) directions. Journal of Applied Physics (
J, Appl, Phys,) Volume 28, Page L1
248~L1250. Received June 19, 1987].

From an application standpoint, it is desirable to align the (001) axes perpendicular to the substrate surface. It is necessary to select a substrate suitable for (001) orientation, that is, C-axis orientation, and create a thin film superconductor with highly C-axis orientation.

Problems to be Solved by the Invention An object of the present invention is to orient the (100) or (010) axis parallel to the substrate surface. That is, the (OOi) direction is oriented perpendicular to the substrate surface.

Means for Solving the Problem Using a (001) crystal in MgO as a substrate, the argon (Ar)/oxygen (02) ratio was 95 by weight.
15-60/40. Gas pressure is 80~200mT,
TL (Bat-ncall) ecuc022- by 9 sputtering method under the condition that the substrate temperature is 400 to 600°C.
x oxide [However, A=0.3-0.7. B=5
~9. C=3 to 7] is formed into a film.

Is the temperature of the working substrate too low, or is Ar102 too large?
Alternatively, if the gas pressure is too low, the thin film produced will be polycrystalline or amorphous.

However, suitable Ar102. At gas pressure and substrate temperature, the <001) axis of the thin film is aligned perpendicular to the substrate plane.

Ebitagistically oriented growth.

Example I Film It was prepared by RF-magnetron sputtering. The composition of the target is TL (for Bat-oca), I
Cuc02. -x +: However, A: -0 to 0,2
,8,R==J~10. C=2 to 8. Predetermined amounts of raw materials Tl2O3, BaCO3, CaC0a, and CuO were mixed to form a target. The target powder was placed in a copper pan and pressed at a pressure of 200 kg/cm2.

The sputtering gas is IAr102 with a volume ratio of 97/3~
50150 range. Gas pressure is 606
It was varied in the range of 0-25O. The temperature of the board is 350-
The temperature is 650°C. The distance between the substrate and the target is 8ern.

For the substrate, an MgO single crystal cleaved along the (100) plane was used. Film formation was carried out for 6 hours.

Similar crystal structure (RE)B a2 Cus Op?
-x In the case of single crystal, (010), (100) of orthorhombic system
It has been reported that the electrical resistance in the (001) direction is considerably lower than that in the (001) direction (references listed in -). Therefore, it can be easily estimated that the critical current density is also large in the (010) and (100) directions. The film was formed in a shape of +5 mm x 15 mm, and the X-ray diffraction pattern was observed.

Pt electrodes were attached using RF magnetron sputtering.

Electrical resistance was measured using a four-terminal method. For thin film samples prepared under various conditions, we investigated whether they exhibit superconductivity by measuring temperature changes in electrical resistance and magnetic susceptibility. (00
1), (002), (003)... To express the degree to which the directions are oriented perpendicular to the substrate, the orientation rate is expressed as I(0
01)/[I(001)→-I(010). If it is completely oriented in the (001) direction, that is,
If the (001) direction is perfectly aligned perpendicular to the substrate, the orientation ratio will be 1. The sputtering conditions were determined such that this orientation ratio was thick.Composition TL (Baa, 6Casr,
) Table 1 shows the orientation ratios of thin films produced under various sputtering conditions for acos022-x. A thin film with this composition exhibited superconducting properties within the range of sputtering conditions tested, with a critical temperature of 95-125°C.

Orientation rate I(001)/[I(001)+I(010)]
+Ar102 is 9515~60/40. Gas pressure is 8080-2O0, substrate temperature is 400-800℃
In the range of , it is very large and exceeds 0.5.

Table 1 T L (Ba@, 5Cal11.5) scuG
Relationship between production conditions and orientation rate of o22-x [1 piece Table 1 T la (B aa, s Cae, s ) * Cua
Relationship between production conditions and orientation rate of O22-X [2 pieces Table 1 T 1a(Baa, 5Caa, 5)scueo2a-x
Relationship between production conditions and orientation rate [3 pieces Table 1
Relationship between production conditions and orientation rate [4] C and A=0.2 to 0.8. B=4-10. C
Table 2 shows the relationship between the superconducting critical temperature Tc and the orientation rate when the superconducting critical temperature Tc is varied within the range of =2 to 8. × indicates a sample that did not exhibit superconductivity at least above the liquid nitrogen temperature.

From the results in Table 2 + T14 (Ba+-acall)
scucOaa-i+ [: However, A=0.3~0
．． 7. B=5-9. It can be seen that the sample with a composition of C=3 to 7] has a critical temperature of 77 or higher and a high orientation rate.

The specific resistance at room temperature of samples with a high orientation ratio of 0.5 or more was quite low. For example, the specific resistance of a sample with an orientation rate of 0.76 was about 1/60 of the specific resistance of a sample with an orientation rate of 0.17.

(Left below) Next, the sputtering conditions were kept constant, that is, Ar
10a:90/10. Gas pressure = 200mT.

We investigated the composition dependence of the superconducting properties and orientation ratio of thin films prepared at a substrate temperature of 550°C. Composition formula % Formula % Table 2 Composition formula Tla (Bat-ncan) Bcu
c022-.

Composition dependence of superconducting critical m degree TO2 coordination ratio of thin film [1
] Table 2 Composition formula TIA (Bat-ncaa) ecueo22-
Superconducting critical temperature Tc+ of the thin film of
22- Superconducting Critical Temperature Tc+ of Thin Film Composition Dependency of Orientation Rate [3 Effects of the Invention According to the present invention, argon/oxygen is used by the sputtering method.

By simply controlling the gas pressure and substrate temperature, it is possible to form a superconducting thin film on an MgO single crystal with low resistivity parallel to the nine planes, that is, with the (001) axis highly oriented perpendicular to the X-plate plane.

Claims (1)

[Claims] On a MgO (magnesia) single crystal substrate cleaved in the (100) plane, argon/oxygen was applied at a volume ratio of 95/5 to 60.
/40, gas pressure is 80-200mT, substrate temperature is 4
Tl_4(Ba
_1_-_ACa_A)_BCu_CO_2_2_-_
X oxide [However, A = 0.3 to 0.7, B = 5 to 9, C
=3~7] By forming a thin film, crystal orientations (100) and (010) with low electrical resistance parallel to the substrate surface
A method for producing a superconducting thin film characterized by orienting its axes.