JPH03285146A - Method and apparatus for evaluating superconductor thin film - Google Patents

Abstract

PURPOSE:To simply and rapidly evaluate a superconductor membrane in a non- destructive manner by irradiating the necessary region of a superconductor crystal with polarized light and detecting the intensity of the reflected light of a polarized component crossing irradiated light at a right angle from a grain to be aimed at. CONSTITUTION:The polarized light from a light source 11 is applied to the necessary region of a superconductor membrane 4 to be evaluated through a polarizer 12, a half mirror 13 and a lens 14. Subsequently, the reflected light from the irradiated region is guided to a detector 15 through the lens 14 and the mirror 13 and only the reflected light of a polarized component crossing the irradiated light at a right angle is guided to a high sensitivity camera 17 through a lens 16 and the intensity thereof is detected. The membrane 4 is rotated around the axis vertical to the surface of a rotary type sample table 21 being a single crystal plate in such a state that the setting conditions of the irradiated light and reflected light are fixed. By this method, the difference between the angle allowing the main axis of the substrate crystal to coincide with the polarized direction of the irradiated light and the angle minimizing the detected intensity of the reflected light is calculated to evaluate the crystal azimuth relation between the membrane 4 and the substrate single crystal.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a superconductor thin film evaluation method and evaluation device, and includes methods for evaluating individual orientations of crystal grains in a polycrystalline superconductor thin film, crystal grain size distribution by orientation, and crystal grain orientation. The purpose of the present invention is to provide an evaluation method for simply, quickly, and non-destructively determining the distribution and deviation of crystal orientation within the thickness, and an evaluation device for its implementation. , irradiate polarized light onto the surface of a polycrystalline superconductor thin film formed on a single crystal substrate,
Measure the reflected light intensity of the polarized light component orthogonal to the polarization direction of the irradiated light from the crystal grain of interest, rotate the thin film within its plane, and use the position where the reflected light intensity is maximum as a reference.
By determining the difference between the rotation angle to the position where the intensity of the reflected light is the minimum and the rotation angle at which the known principal axis direction of the substrate single crystal and the polarization direction of the irradiation light match, the crystal grain of interest and the above The method of evaluating crystal grain size distribution by orientation and crystal grain orientation distribution according to the present invention, which is configured to evaluate the crystal orientation relationship with the substrate single crystal, irradiates the film surface of a polycrystalline superconductor thin film with polarized light, Observe the reflected light image of the polarized light component orthogonal to the polarization direction of the irradiated light from the film surface area of interest, classify the individual crystal grains based on the difference in brightness of the individual crystal grain images in the reflected light image,
The area and density of crystal grains with equivalent brightness were measured, the thin film was rotated within its plane, the reflected light image was observed at multiple rotational positions, the crystal grains were classified, and the area and density were measured.
The evaluation apparatus according to the present invention is configured to evaluate the distribution of crystal grain size by orientation and the distribution of crystal grain orientation in the plane of a thin film by performing density measurement, and the evaluation apparatus according to the present invention for implementing these evaluation methods is a polarized light irradiation and reflected light intensity measuring section that irradiates an object with polarized light and measures the intensity of reflected light from the object to be measured; a holding and rotating section that holds and rotates the object to be measured; and a rotation of the holding and rotating section. and a control and image processing unit that performs image processing on data from the polarized light irradiation and reflected light intensity measurement unit corresponding to the rotation angle thereof, and the crystal orientation within the film thickness according to the present invention The method of evaluating the deviation in each region is to irradiate the surface of a polycrystalline superconducting thin film formed on a single crystal substrate with polarized light, and to evaluate the polarization component perpendicular to the polarization direction of the irradiated light from the film surface region of interest. The reflected light image is observed, the individual crystal grains are classified based on the difference in brightness of the individual crystal grain images in the reflected light image, and then polarized light is irradiated from the bottom surface of the single crystal substrate to separate the single crystal substrate and its Transmits through the superconducting thin film above,
The transmitted light image of the polarized light component perpendicular to the polarization direction of the irradiated light is observed, the individual crystal grains are classified based on the difference in brightness of the individual crystal grain images in the transmitted light image, and the reflected light image and the transmitted light image are separated. The method of evaluating the crystal orientation deviation within the film thickness for each crystal grain according to the present invention is configured to evaluate regions in which crystal grains with misaligned crystal axis orientations are stacked vertically. The surface of a polycrystalline superconducting thin film formed on a substrate is irradiated with polarized light, and the reflected light intensity of the polarized light component orthogonal to the polarization direction of the irradiated light from the crystal grains of interest is measured.
The thin film is rotated within its plane to fix the thin film at a position where the intensity of reflected light from the crystal grains is minimum, and then polarized light is irradiated from the bottom surface of the single crystal substrate to cover the single crystal substrate and the superstructure above it. Transmit the conductive thin film and measure the intensity of the transmitted light of the polarized component perpendicular to the polarization direction of the irradiated light for the crystal grain of interest,
By detecting the uneven transmitted light intensity distribution that appears within the crystal grains, the present invention is configured to evaluate the presence or absence of crystal grains with misaligned crystal axes between the target crystal grain and the substrate. The evaluation device according to the present invention for implementation includes a polarized light irradiation unit (1) that irradiates polarized light from the front side and back side of a measurement target, and a reflected light unit that measures the intensity of reflected light and transmitted light from the measurement target. and transmitted light intensity measuring section (2
), a holding and rotating part (3) that holds and rotates the object to be measured, and a part that controls the polarized light irradiation part (1) and the reflected light and transmitted light intensity measuring part (2) and measures the reflected light and transmitted light intensity. An image processing section (2) that performs image processing on the data from section (2)
4).

[Industrial application field]

The present invention relates to a method and apparatus for evaluating superconductor thin films.

In recent years, research and development of oxide high-temperature superconducting materials has been progressing [e.g. bismuth-strontium-calcium-copper-
Oxygen (Bi-3r-Ca-Cu-0) system and yttrium-barium-copper-oxygen (Y-Ba-Cu-〇) system] are different from conventionally used superconducting materials [niobium (Nb)
, niobium nitride (NbN), niobium trigermanium (
Nb3Ge), etc.], the critical temperature (Tc) is so high that it exceeds the liquid nitrogen temperature (77K). This eliminates the need to use expensive liquid helium for cooling to achieve a superconducting state, making it easier to handle and making it a more practical superconducting material. It can be applied to wiring materials for semiconductor devices, etc.

For use in such applications, high quality and good properties are required.
In particular, there is a need to produce thin films of oxide superconductors with high critical current densities, and various growth and film-forming methods have been developed. However, since currently available superconducting thin films have a polycrystalline structure, the critical current density depends on both the quality of the crystal itself and the characteristics of the boundaries between crystal grains.

To this end, we investigated the size of crystal grains (hereinafter referred to as "grains") contained in the fabricated oxide superconducting thin film, their crystal orientation, the orientation relationship between grains, the relationship with the substrate crystal orientation, and Easily calculate the statistical distribution within the thin film plane of
There is a need for the development of an efficient evaluation method.

[Conventional technology]

Conventionally, transmission electron microscopy has been used to evaluate the size of grains contained in polycrystalline oxide superconductor thin films, their crystal orientations, the orientation relationships between grains, and their relationships with the substrate crystal orientation. Ta. This method involves thinning the fabricated superconducting thin film to a thickness that allows sufficient penetration of the electron beam, irradiating the microscopic area with the electron beam, and determining the structure and orientation of the crystal from the diffraction pattern of the electron beam that passes through the area. The orientation relationship between the superconducting thin film crystal and the substrate crystal is determined by observing a thin sample including the region of the substrate crystal.

However, it requires a great deal of effort to thin the sample to a thickness suitable for transmission electron microscopy. Furthermore, since the range in which the orientation can be determined at one time by this method is at most about a few, it is important to note that superconducting thin films with large grain diameters of several 107 or more [for example, in chemical vapor deposition (CV[l] method, the grain diameter 100p or more] was not suitable for evaluation.

[Problem to be solved by the invention]

An evaluation method for simply, quickly, and non-destructively determining the individual orientation of crystal grains in a polycrystalline superconductor thin film, the grain size distribution and grain orientation distribution by orientation, and the deviation of crystal orientation within the film thickness, and its implementation. The purpose is to provide an evaluation device for

[Means to solve the problem]

In order to achieve the above object, the method for evaluating individual crystal grains according to the present invention (hereinafter referred to as the "first invention") uses polarized light on the film plane of a polycrystalline superconductor thin film formed on a single crystal substrate. , measure the intensity of the reflected light of the polarized component perpendicular to the polarization direction of the irradiated light from the crystal grain of interest, rotate the thin film within its plane, and set the position where the intensity of the reflected light is maximum as a reference. By determining the difference between the rotation angle to the position where the reflected light intensity is minimum and the rotation angle at which the known principal axis direction of the substrate single crystal and the polarization direction of the irradiation light match, the crystal grain of interest and The method for evaluating crystal grain size distribution by orientation and crystal grain orientation distribution according to the present invention (hereinafter referred to as "second invention") is characterized by evaluating the crystal orientation relationship with the substrate single crystal. The film surface of the conductor thin film is irradiated with polarized light, and the reflected light image of the polarized light component orthogonal to the irradiated light polarization direction from the film surface area of interest is observed, and the brightness of individual crystal grain images in the reflected light image is determined. The individual crystal grains are classified according to the difference in brightness, the area and density of the crystal grains with equivalent brightness are measured, the thin film is rotated within its plane, the reflected light image is observed at multiple rotational positions, and the crystal grains are measured. It is characterized by evaluating the distribution of crystal grain size by orientation and the distribution of crystal grain orientation in the plane of the thin film by performing the classification and the area/density measurement described above.

The evaluation device according to the present invention for carrying out the above first and second inventions (hereinafter referred to as the "third invention") irradiates a measurement object with polarized light and measures the intensity of reflected light from the measurement object. a polarized light irradiation and reflected light intensity measuring section; a holding and rotating section that holds and rotates the object to be measured; and a polarized light irradiating and reflected light that controls the rotation of the holding and rotating section and corresponds to the rotation angle thereof. It is characterized by having a control unit and an image processing unit that perform image processing on data from the intensity measurement unit.

The method of evaluating the crystal orientation deviation within the film thickness for each region according to the present invention (hereinafter referred to as the "fourth invention") is to irradiate the surface of a polycrystalline superconducting thin film formed on a single crystal substrate with polarized light. Then, the reflected light image of the polarized light component perpendicular to the polarization direction of the irradiated light from the film surface area of interest is observed, and the individual crystal grains are classified based on the difference in brightness of the individual crystal grain images in the reflected light image. Next, polarized light is irradiated from the bottom surface of the single crystal substrate and transmitted through the single crystal substrate and the superconducting thin film thereon, and a transmitted light image of the polarized light component perpendicular to the polarization direction of the irradiated light is observed. The individual crystal grains are classified based on the difference in brightness of the individual crystal grain images,
By comparing the reflected light image and the transmitted light image, the area where crystal grains with shifted crystal axis orientations are stacked up and down can be evaluated. The method for evaluating each case (hereinafter referred to as the fifth invention) is to irradiate polarized light onto the surface of a polycrystalline superconducting thin film formed on a single crystal substrate, and to evaluate the polarized light from the crystal grains of interest. The reflected light intensity of the polarized light component perpendicular to the direction is measured, the thin film is rotated within its plane, the thin film is fixed at the position where the reflected light intensity of the crystal grains is minimum, and then the thin film is measured from the bottom surface of the single crystal substrate. Polarized light is irradiated and transmitted through the single crystal substrate and the superconducting thin film thereon, and the intensity of the transmitted light of the polarized component perpendicular to the direction of polarization of the irradiated light is measured for the crystal grains of interest to determine the defects appearing within the crystal grains. The fourth and fifth inventions are carried out by detecting a uniform transmitted light intensity distribution to evaluate the presence or absence of a crystal grain whose crystal axis direction is shifted between the crystal grain of interest and the substrate. The evaluation device according to the present invention (hereinafter referred to as the "sixth invention") includes a polarized light irradiation section that irradiates polarized light from the front side and the back side of the object to be measured;
a reflected light and transmitted light intensity measurement section that measures the reflected light intensity and transmitted light intensity from the measurement object; a holding and rotation section that holds and rotates the measurement object; and the polarized light irradiation section and the reflected light and transmitted light intensity. It is characterized by having an image processing section that controls the measurement section and performs image processing on data from the reflected light and transmitted light intensity measurement section.

[For production]

The method for evaluating a superconductor thin film according to the first invention irradiates the surface of an oxide superconductor thin film grown on a substrate crystal with polarized light, and detects the intensity of reflected light of a polarized component perpendicular to the irradiated light. This was done based on the knowledge that the above-mentioned reflected light intensity is the weakest when the direction of polarization matches the a-axis or b-axis direction of the superconductor crystal.

The steps are as follows.

■ Irradiates polarized light to the required areas of the superconductor crystal,
From the grain of interest, the intensity of reflected light of a polarization component orthogonal to the irradiated light is detected.

■ While the setting conditions of the irradiated light and reflected light remain fixed, rotate the superconductor crystal around an axis perpendicular to the substrate crystal surface, and measure the angle at which the principal axis of the substrate crystal coincides with the polarization direction of the irradiated light. θ1 and an angle θ2 at which the detected reflected light intensity is minimized are determined.

(2) From the difference between the above-mentioned angles θ1 and θ2, the angular deviation between the crystal orientation of the grain irradiated with light and the orientation of the substrate crystal is determined.

Therefore, according to the method for evaluating a superconducting thin film according to the first invention, the relationship between the crystal orientation of the polycrystalline grains present in the oxide high temperature superconductor thin film and the crystal orientation of the substrate crystal can be easily and quantitatively measured. can do.

The method for evaluating a superconducting thin film according to the second invention is to irradiate polarized light onto a required region on the surface of a superconductor crystal, and observe an image of reflected light from the region with a polarized light component orthogonal to the irradiated light. This was done based on the knowledge that images of crystal grains with different brightness can be obtained in regions with different crystal orientations.

The steps are as follows.

■ Irradiates polarized light to the required areas of the superconductor crystal,
The image of the reflected light from the area, which is a polarized light component orthogonal to the irradiated light, is observed with a television camera or the like, and the image is input.

(2) Binarize the image data of the obtained reflected light image into an area with the same brightness as the grain of interest and an area with other brightness.

■ Perform particle analysis on the binarized image data and calculate its area and proportion to the total area.

Therefore, according to the method for evaluating a superconducting thin film according to the second invention, the size and in-plane distribution of the crystal orientation of polycrystalline grains present in an oxide high-temperature superconductor thin film can be easily and easily measured over a range of several millimeters. and can be measured statistically.

The superconductor thin film evaluation device according to the third invention irradiates the object to be measured with polarized light in the polarized light irradiation and reflected light intensity measurement section and measures the intensity of reflected light from the object to be measured, and the holding and rotating section irradiates the object to be measured with polarized light. By holding and rotating the object, controlling the rotation of the holding and rotating section in the control and image processing section, and image processing the data from the polarized light irradiation and reflected light intensity measuring section corresponding to the rotation angle. , the evaluation method of the first invention and/or the second invention can be implemented as necessary.

Since the first, second, and third inventions described above evaluate using reflected light from the thin film surface, grains with misaligned crystal axes are stacked up and down inside a polycrystalline thin film with a thickness of 500 Å or more. In this case, only the grains on the surface side appear sensitively in the image, making it difficult to identify grains that are misoriented within the film thickness.

When the thickness of the superconducting thin film is about 500 mm or more, the fourth invention and the fifth invention use transmitted light in addition to reflected light.
The evaluation method of the invention and the evaluation device of the sixth invention for implementing these are suitable.

A method for evaluating a superconducting thin film according to the fourth aspect of the present invention is that when the surface of a polycrystalline superconducting thin film grown on a substrate crystal is irradiated with polarized light, the crystal grain orientation is determined from the surface to a depth of approximately half the penetration depth of the light. - A polarized light is irradiated from the lower surface of the blade wheel crystal substrate and transmitted through the single crystal substrate and the superconducting thin film thereon, and a transmitted light image of the polarized light component perpendicular to the polarization direction of the irradiated light is obtained. When observed, an image is obtained that reflects the entire crystal grain orientation from the surface of the thin film to the interface with the substrate, so when comparing the image of reflected light and the image of transmitted light, it is possible to see that the crystal axis orientation has shifted. This was done based on the knowledge that there is a difference between reflected light images and transmitted light images in regions where crystal grains are stacked one above the other.

The steps are as follows.

■ Irradiates polarized light to the required areas of the superconductor crystal,
An image of the reflected light from the region having a polarization component perpendicular to the polarization direction of the irradiated light is observed with a television camera or the like, and the image is input.

(2) The image data of the obtained reflected light image is divided into groups according to the brightness of each grain. The darkest grain is the brightness level 0, and the brightest grain is the brightness level N-1 (N=2
r', n depends on the functionality of the analog-to-digital (AD) converter. For example, if an AD converter with n=8 bits is used, N=256. ).

■ Polarized light is irradiated from the bottom surface of the substrate crystal, transmitted through the substrate crystal and the superconducting thin film thereon, and the reflected light is measured. Transmitted light of a polarized light component perpendicular to the polarization direction of the irradiated light from the same region. Observe the image with a television camera, etc., and input the image.

■ The image data obtained in ■ is grouped using the same method as in ■, and subtraction is performed between the images with the image data grouped in ■.
A region in which the difference between the two has reached a significant size is identified in the obtained image data.

Therefore, according to the method for evaluating a superconducting thin film according to the fourth aspect of the invention, the presence or absence of grains with misaligned crystal axes existing between the grains identified near the surface and the substrate is determined in a region containing a large number of grains. It can be easily evaluated.

A method for evaluating a superconducting thin film according to the fifth invention irradiates the surface of a polycrystalline superconducting thin film grown on a substrate crystal with polarized light,
The thin film is fixed at a position where the reflected light intensity of the polarized light component perpendicular to the irradiated light from the grain of interest is minimized, and polarized light is irradiated from the bottom side of the single crystal substrate, and the polarized light component perpendicular to the irradiated light polarization direction is fixed. This was based on the knowledge that when observing the transmitted light image of a substrate, the grains recognized on the surface side differ from the crystal grain orientation, and the grains existing between the substrate crystal and the grains on the surface side can be identified with the highest sensitivity. It is.

The steps are as follows.

(2) Irradiate the surface of the superconductor crystal thin film with polarized light and measure the reflected light intensity of the polarized light component perpendicular to the polarization direction of the irradiated light of the grain of interest.

■ While the setting conditions of the irradiation light and reflected light remain fixed, the superconductor crystal is rotated around an axis perpendicular to the substrate crystal surface and the sample is fixed at the position where the intensity of the reflected light is minimized. A reflected light image is recorded in a region containing the grain of interest.

(2) Polarized light is irradiated from the bottom surface of the substrate crystal and transmitted through the substrate crystal and the superconducting thin film thereon, and a transmitted light image of the polarized light component orthogonal to the polarization direction of the irradiated light is recorded for the grain of interest, and A location where the brightness of the transmitted light image is uneven compared with the reflected light image is detected.

Therefore, according to the method for evaluating a superconducting thin film according to the present invention, the grains recognized on the surface side of the superconducting thin film have different crystal axis orientations, and the grains existing between the substrate crystal and the grains on the surface side are most sensitive. Good and easy to evaluate.

As an application of the method for evaluating superconducting thin films according to the fifth invention, after carrying out the method, the sample is rotated by a small angle, focusing on the brightness distribution of internal grains with different orientations, and the angle at which the grains of interest become the darkest is determined. , it is possible to measure the misalignment between the surface grains and the internal grains.

The steps are as follows.

■ By the method for evaluating superconductor crystal thin films according to the fifth invention,
The grains recognized on the surface side of the superconductor thin film have different crystal axis orientations, and the grains existing between the substrate crystal and the grains on the surface side are detected.

■ While the setting conditions of the irradiated light and reflected light remain fixed, the superconductor crystal is rotated several degrees around the axis perpendicular to the substrate crystal surface until the reflected light intensity of the grain of interest is minimized. Measure the rotation angle.

In the superconducting thin film evaluation device according to the sixth aspect of the present invention, the polarized light irradiation section irradiates polarized light from the front and back sides of the object to be measured, and the reflected light and transmitted light intensity measurement section measures the intensity of reflected light from the object to be measured. The transmitted light intensity is measured and the reflected light image and transmitted light image are observed.The holding and rotating section holds and rotates the object to be measured, and the control and image processing section measures the intensity of the reflected light and transmitted light with the polarized light irradiation section. The evaluation method of the fourth invention and/or the fifth invention can be implemented as necessary by controlling the parts and performing image processing on the data from the reflected light and transmitted light intensity measuring parts.

Hereinafter, the present invention will be described in detail by way of embodiments with reference to the accompanying drawings.

[Example 1] FIG. 1 shows a configuration example of a superconductor thin film evaluation apparatus of the present invention. The apparatus shown in the figure basically consists of three components: a polarized light irradiation and reflected light intensity measurement section 1, a sample holding and rotation section 2, and a control and image processing section 3. The irradiation/measurement unit 1 includes a light source 11 such as a halogen lamp or an ultra-high pressure mercury lamp, a polarizer 12 using a polarizing prism, a polarizing filter, a catadioptric polarizer, etc., an analyzer 15, a lens 14° 16, a mirror 13, It consists of a high-sensitivity camera 17 using SIT or CCD, a camera control device 18, and a monitor television 19. The holding/rotating unit 2 includes a rotating sample stage 21, a rotating step motor 22, and a step motor power source 23. Then, the control and image processing unit 3 extracts the necessary grains from the reflected image, processes the reflected light intensity data corresponding to the rotation angle, and calculates the angle at which the intensity is the minimum value, and the image The image of the input reflected light is binarized into an area with the same brightness as the desired grain and an area other than the desired grain, as will be described in detail later.
This is to perform particle analysis.

The operation of the apparatus shown in FIG. 1 will be explained.

A polarizer 12 is placed in the necessary area of the superconductor thin film 4 to be evaluated.
, a half mirror 13 , and a lens 14 , polarized light is irradiated from the light source 11 . Next, the light reflected from the required area is guided to the analyzer 15 via the lens 14 and the mirror 13, and only the reflected light with a polarization component orthogonal to the polarization of the irradiated light is guided to the television camera 17 via the lens 16.

In the first invention, the control and image processing device 3 measures in real time the intensity change of a part of the image data detected by the television camera 17 as the sample rotates, and in the second invention, it measures the entire image data obtained. performs image processing.

[Example 2] An example of the method for evaluating a superconducting thin film according to the first invention using the apparatus of Example 1 will be described.

The method for evaluating a superconductor thin film according to the first invention is to determine the difference between the rotation angle at which the reflected light intensity is minimized and the rotation angle at which the principal axis direction of the substrate crystal coincides with the polarization direction of the irradiated light. This study evaluates the relationship between the crystal orientation of polycrystalline dalein in a superconducting thin film and the crystal orientation of the substrate crystal.

An example in which the first invention is applied to a Bi-5r-Ca-Cu-0 based superconductor thin film will be described below. The substrate is made of magnesium oxide (MgO), yttrium stabilized zirconia (YSZ), magnesia spinel (MgA
f20. ), titanate stone (TiS
r03) etc. can be used.

As a method for depositing a superconductor thin film on a substrate, a sputtering method, a vapor deposition method, a molecular beam epitaxy (MBE) method, a chemical vapor phase epitaxy (CV[l) method, or the like can be used.

As an example, Bi
-3r-Ca-Cu -0 based superconductor thin film with Mg[l
What is formed on the substrate will be explained.

Relationship between the angle at which the superconductor thin film is rotated about the axis perpendicular to the substrate crystal surface and the reflection intensity from within appropriate grains within the thin film crystal for two types of sample 1 and sample 2 with different growth conditions. are shown in Figures 2 and 3, respectively. The rotation angle of the sample is based on the <100> orientation of the substrate crystal (
0°).

Figure 2 shows three adjacent grains A and B in sample 1.
, C shows the change in the reflection intensity of the rotation angles of -10°, 15°, and 45°, respectively, and the reflection intensity shows the minimum value. Therefore, these grains A, B, C
The a-b axis of and the main axis of the substrate crystal are each -10°
, 15°, 45° shifted, grains A-B, B-
The misalignment between C and C-A is 25° and 30°, respectively.
, 35゛.

Figure 3 shows two adjacent grains D and E in sample 2.
The figure shows the change in the reflection intensity of , and the reflection intensity is minimum when the rotation angle is Oo and 45°, respectively. Therefore, the a-b axis of grain D is the <100> axis of the substrate crystal,
It can be seen that the a-b axis of grain E coincides with the <110> axis of the substrate crystal.

From these facts, when applying the first invention, the <100> orientation of the substrate crystal is set as the reference (
It can be seen that by using the <100> orientation of the substrate crystal at 0°), it is possible to directly determine the deviation between the substrate crystal orientation and the grain orientation of the superconducting thin film.

[Example 3] An example of a method for evaluating a superconducting thin film according to the second invention using the apparatus of Example 1 will be described.

The method for evaluating a superconductor thin film according to the second invention identifies crystal grains with different orientations based on differences in the brightness of crystal grains included in a reflected image, and measures the area and density of grains with equivalent brightness. By doing so, the in-plane distribution of the polycrystalline grain size and crystal orientation of the superconducting thin film is statistically evaluated.

An example in which the first invention is applied to a Bi-3r-Ca-Cu-0 based superconductor thin film will be described below. The substrate includes magnesium oxide (MgO), yttrium stabilized zirconia (YSZ), and magnesia spinel (MgO).
gA j! 204), strontium titanate (T+
5rOs), etc. can be used.

As a method for depositing a superconductor thin film on a substrate, a sputtering method, a vapor deposition method, a molecular beam epitaxy (MBE) method, a chemical vapor phase epitaxy (CVD) method, etc. can be used.

As an example, a Bi
-5r -Ca -Cu -0 based superconductor thin film with Mg
What is formed on the O substrate will be explained.

For example, a case will be described in which a reflected image of the sample 1 (FIG. 4(a)) is observed in an arrangement where the polarization direction of the irradiated light matches the <IQO> direction of the substrate crystal. First, this is recorded in the data processing device 3 using the high-sensitivity camera 17, and then image measurement is performed to obtain a histogram. The results are shown in Figure 4 (b
). The horizontal axis shows the brightness, and the vertical axis shows the proportion occupied by the area of that brightness.

It can be seen that there are roughly three types of areas with different brightness in FIG. 4(b). Next, the brightness area of interest and other areas are binarized. By converting the binarized data back into image data, the grain of the brightness of interest can be recognized.

The area corresponding to brightness 1 in Fig. 4(b) is shown in Fig. 4(C).
corresponds to the bright area of In the case of this sample, the a-b plane directions are oriented in various directions, and the average area of the grains is about 0.02 mm'. In the grain shown in FIG. 4(C), the a-b axis orientation is rotated by approximately 45 degrees from the <100> direction of the substrate crystal, and the proportion of the entire field of view is approximately 58 degrees.
You can see that there is a percentage.

Figures 5 (a) and (b) show the configuration obtained in (a) where the polarization direction of the irradiated light coincides with the <100> direction of the substrate crystal, and (b) where it is rotated by 45°. This is a reflected image of sample 2. In the field of view in the same figure, the region where the direction of the a-b axis of the superconductor thin film coincides with the <100> direction of the substrate crystal is approximately 15% of the field of view, and the region in which the direction of the a-b axis of the superconductor thin film coincides with the <100> direction is approximately 15% of the field of view. It was found that about 80% of the area coincides with the direction, and about 5% of the area coincides with the other directions.

[Embodiment 4] FIG. 6 shows a configuration example of a superconductor thin film evaluation apparatus according to the sixth invention. The apparatus shown in the figure basically consists of four components: a polarized light irradiation section 101, a reflected light and transmitted light intensity measurement section 102, a holding and rotation section 103, and a control and image processing section 104. The polarized light irradiation unit 101 includes light sources 111 , 11 such as a halogen lamp or an ultra-high pressure mercury lamp.
4, a polarizer 112, 115 using a polarizing prism, a polarizing filter, a catadioptric polarizer, etc., and a mirror 11.
Consists of 3.116.

The reflected light and transmitted light intensity measurement unit 102 includes an analyzer 122
, lens 121.123 , SIT or CCD
It consists of a high-sensitivity camera 124 using The holding and rotating section 103 includes a rotating sample stage 131, a rotating step motor, and its power source 132. The control and image processing device 141 of the control and image processing 8104 determines the sample stop position by measuring the reflected light intensity while rotating the sample, and performs control to switch between observing the reflected light image and the transmitted light image. This is for performing image processing of reflected light images and transmitted light images.

This series of operations is performed while watching the monitor television 142.

The operation of the apparatus shown in FIG. 6 will be explained.

In the case of measurement using reflected light, a polarizer 112 and a half mirror 113 are placed in necessary areas of the superconductor thin film 105 to be evaluated.
, and a lens 121, irradiate polarized light from the light source 111, and in the case of measurement using transmitted light, a polarizer 115
, polarized light from the light source 114 is irradiated via the mirror 116 . Next, the light reflected or transmitted from the required area is passed through the lens 12L and mirror 113 to the analyzer 122.
Only the reflected light of the polarization component orthogonal to the polarization of the irradiated light is guided to the television camera 117 via the lens 123. In the fourth invention, the control/image processing device 141 performs image processing of image data obtained by the television camera 124,
In the fifth aspect of the invention, intensity changes in part of the image data inspected by the television camera 124 as the sample rotates are measured in real time.

[Example 5] An example of a superconducting thin film evaluation method according to the fifth invention using the apparatus of Example 4 will be described.

Hereinafter, an example in which the present invention is applied to a Bi-3r-Ca-Cu-0 based superconductor thin film will be described. On the board,
Magnesium oxide (MgOL Yttrium stabilized Zirninia (YSX), ?gnesia spinel (MgAl
204>, Strontium titanate (TiSrO5)
etc. can be used.

Sputtering methods, vapor deposition methods, molecular beam epitaxy (MBE) methods, chemical vapor phase epitaxy (CVD) methods, and the like are used as methods for depositing superconductor thin films on substrates.

In this example, the critical temperature was set to 80°C by an atmospheric pressure halide CVD method using a halogen compound as a source material.
Bi-5r-Ca-Cu-0 based superconductor thin film with MgO
What is formed on the substrate will be explained.

The growth conditions are as follows.

■ BiCI! 3 Temperature: 150-170℃■ CuB
r2 temperature: 340-380℃■ CaI2 temperature near 5
0 to 800℃ ■ Srl, temperature near 60 to 820℃ ■ Substrate temperature near 50 to 820℃ ■ He carrier gas flow rate: 20 to 501/min ■ 0□
Concentration of gas to He: 2 to 8% ■ Concentration of H2C to He: 100 to 1000 ppl? +■ Growth rate: 3 to 30 people/min The observation example of the transmitted light image of the thin film obtained by the above growth method is shown in the seventh example.
FIG. 8 shows an example of observing a reflected light image at the same location. Both were observed at a rotation angle of θ−〇°. For example, if we focus on the grains marked a in FIGS. 7 and 8, the absolute brightness in FIGS. 7 and 8 is different, but they are relatively the brightest. Furthermore, there is no difference between the two in the brightness distribution within the grain.

On the other hand, if we pay attention to the marks, we can detect grains that are the darkest in the reflected light image (FIG. 8), but have different brightness in the transmitted light image (FIG. 7). This means that the a-axis on the surface side of region b is M
This shows that although the orientation is aligned with the <100> axis of the gO substrate, there are grains with misaligned crystal orientations inside.

Next, FIG. 9 is a transmitted light image of the same area as above observed at a rotation angle θ=45°. The reason why the distribution of brightness and darkness of the grains is reversed from that of the reflected light image in FIG. 3 is that most of the grains contributing to the brightness and darkness in FIG. 9 are present on the surface side. In the region shown in FIG. 9, there are grains whose orientations are shifted inside, but since the grains on the surface side become brighter, the dark grains inside cannot be detected. Therefore, it can be seen that the fifth aspect of the invention is effective in detecting the area with the most sensitive orientation.

FIGS. 10 and 11 are examples of observation of transmitted light images of t, showing an application example of the fifth invention. The sample was rotated in a configuration for observing a reflected light image to determine the position where the entire field of view was darkest (θ=0°), and then the sample was rotated by a small angle in a configuration for observing a transmitted light image. Figure 1O is θ=-7°, Figure 11 is θ=
These are the observation results at 10°. For example, focus on areas marked c and d. Area C is dark in FIG. 11 and bright in FIG. 10, but area d shows the opposite brightness and darkness. This is because the a-axis direction of the region d is shifted by 17 degrees from the substrate crystal, so it is the darkest in Figure 10, and conversely, the region C is shifted +10 degrees, so it is the darkest in Figure 11. be.

Thus, it can be seen that the fifth invention is effective for investigating internal crystal orientation deviations.

〔Effect of the invention〕

As explained above, according to the present invention, the relationship between the a-axis or b-axis direction of each crystal grain existing in an oxide high temperature superconductor thin film and the main axis direction of the substrate crystal can be determined in a short time and quantitatively. It can be used to easily and non-destructively measure the in-plane distribution of the size and crystal orientation of polycrystalline grains present in oxide high-temperature superconductor thin films over a range of several millimeters. be able to.

In addition, by using transmitted light in addition to reflected light, it was possible to detect crystal grains present in the oxide high temperature superconductor thin film.
It is easy and non-destructive to remove grains that have different orientation from the grains on the surface side and are distributed between the grains on the surface side and the substrate crystal.
Can be measured with high sensitivity.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is an apparatus configuration diagram showing an example of an apparatus for carrying out the evaluation method of the present invention. FIGS. Graphs showing the results of evaluating the azimuth relationship with the rotation angle, Figure 4 (a), (b),
and (C) are (a) metallographic photographs showing examples of image observation of crystal grain dimensions and orientations according to the present invention; (b)
Graphs and (C) Metal structure photographs. Figures 5 (a) and (b) are metal structure photographs showing examples of image observation of crystal grain dimensions and orientations according to the present invention. Figure 6 is evaluation of the present invention. An apparatus configuration diagram showing an example of an apparatus for carrying out the method, and FIGS. 7 to 11 are metallographic photographs showing examples in which crystal grains were observed according to the present invention. DESCRIPTION OF SYMBOLS 1... Polarized light irradiation and reflected light intensity measurement unit, 2... Holding and rotation unit, 3... Control and image processing device, 4... Superconducting thin film to be evaluated, 11... Light source, 12 ...Polarizer, 13
...Mirror 14.16...Lens, 1
5... Analyzer, 17... High sensitivity camera,
18... Camera control device, 19... Monitor television, 21... Rotating sample stage, 22... Step motor for rotation, 23... Power supply for step motor, 101... Polarized light irradiation unit, 102...Reflected light and transmitted light intensity measurement unit, 103.
...Holding and rotating section, 104... Control and image processing section, 105... Superconducting thin film to be evaluated, 111, 114... Light source, 112, 115.
...Polarizer, 113, 116...Mirror 12
1, 123...lens, 122...analyzer,
124...High sensitivity camera, 119...Monitor TV, 131...Rotating sample stage, 132...
- Rotating step motor and its power source, 141... control/image processing device, 142... monitor television. Figure 1 Relative brightness (b) Figure 320- Figure 1 (O) (b) 321-'', O(> 1., l- Figure 10 Figure 11

Claims (1)

[Claims] 1. Polarized light is irradiated onto the film surface of a polycrystalline superconductor thin film formed on a single crystal substrate, and reflected light of a polarized light component perpendicular to the polarization direction of the irradiated light is reflected from the crystal grains of interest. Measure the intensity, rotate the thin film within its plane, and calculate the rotation angle from the position where the reflected light intensity is maximum to the position where the reflected light intensity is minimum and the known principal axis of the substrate single crystal. Evaluation of a superconductor thin film, characterized in that the crystal orientation relationship between the crystal grain of interest and the substrate single crystal is evaluated by determining the difference between the direction and the rotation angle at which the polarization direction of the irradiated light matches. Method. 2. Irradiate the film surface of the polycrystalline superconductor thin film with polarized light, observe the reflected light image of the polarized light component orthogonal to the polarization direction of the irradiated light from the film surface region of interest, and identify individual crystals in the reflected light image. Individual crystal grains are classified according to differences in the brightness of the grain images, the area and density of crystal grains with equivalent brightness are measured, the thin film is rotated within its plane, and the reflected light image is measured at multiple rotational positions. Evaluation of a superconductor thin film characterized by evaluating the distribution of crystal grain size by orientation and the distribution of crystal grain orientation in the plane of the thin film by performing observation, the above-mentioned crystal grain classification, and the above-mentioned area/density measurement. Method. 3. An evaluation device for carrying out the evaluation method according to claim 1 or 2, comprising polarized light irradiation and reflected light intensity measurement for irradiating a measurement object with polarized light and measuring the intensity of reflected light from the measurement object. part (1), a holding and rotating part (2) that holds and rotates the object to be measured, and a holding and rotating part (2) that controls the rotation of the holding and rotating part (2) and that corresponds to the rotation angle of the polarized light irradiation and A superconductor thin film evaluation device characterized by having a control and an image processing section (3) for image processing data from a reflected light intensity measuring section (1). 4. Irradiate the surface of a polycrystalline superconducting thin film formed on a single crystal substrate with polarized light, observe the reflected light image of the polarized light component perpendicular to the polarization direction of the irradiated light from the film surface area of interest, and calculate the reflected light. The individual crystal grains are classified according to the difference in brightness of the individual crystal grain images in the image, and then polarized light is irradiated from the bottom surface of the single crystal substrate and transmitted through the single crystal substrate and the superconducting thin film thereon, The transmitted light image of the polarized light component perpendicular to the polarization direction of the irradiated light is observed, the individual crystal grains are classified based on the difference in brightness of the individual crystal grain images in the transmitted light image, and the reflected light image and the transmitted light image are separated. A method for evaluating superconducting thin films characterized by comparing regions in which crystal grains with misaligned crystal axes are stacked one above the other. 5. The surface of a polycrystalline superconducting thin film formed on a single-crystal substrate is irradiated with polarized light, and the reflected light intensity of the polarized light component orthogonal to the polarization direction of the irradiated light from the crystal grains of interest is measured. The thin film is rotated within that plane to fix the thin film at a position where the intensity of reflected light from the crystal grains is minimum, and then polarized light is irradiated from the bottom surface of the single crystal substrate to separate the single crystal substrate and the superconducting thin film thereon. The transmitted light intensity of the polarized light component perpendicular to the polarization direction of the irradiated light is measured for the crystal grain of interest, and by detecting the uneven transmitted light intensity distribution that appears within the crystal grain, it is possible to identify the crystal grain of interest. A method for evaluating superconducting thin films characterized by evaluating the presence or absence of crystal grains with misaligned crystal axes between substrates. 6. In the evaluation method according to claim 5, after evaluating the presence or absence of crystal grains with shifted crystal axis orientations that are sandwiched between the crystal grains on the surface of interest and the substrate, the uneven transmitted light intensity is subsequently evaluated. Focusing on the crystal grains in the distribution, the sample is rotated by a small angle in the positive and negative directions, and areas that are partially darker than the brightness before rotation are detected, and the deviation of the crystal axis direction is detected based on the rotation angle. A method for evaluating superconducting thin films characterized by determining the angle. 7. An evaluation device for carrying out the evaluation method according to claims 4, 5, and 6, comprising: a polarized light irradiation section (1) that irradiates polarized light from the front side and the back side of a measurement object; ,
A reflected light and transmitted light intensity measurement unit (2) that measures the reflected light intensity and transmitted light intensity from the measurement object, a holding and rotation unit (3) that holds and rotates the measurement object, and the polarized light irradiation unit ( 1) and an image processing section (4) that controls the reflected light and transmitted light intensity measurement section (2) and performs image processing on data from the reflected light and transmitted light intensity measurement section (2). Evaluation device for superconductor thin films.