JPH02116736A - Method and apparatus for determining crystal orientation - Google Patents

Abstract

PURPOSE:To determine a crystal orientation with a simple method by a method wherein a vibration plane of an electric vector of a laser light is turned to a crystal plane and the light comes into the crystal plane to measure a dependence of a reflection factor on angle of rotation. CONSTITUTION:A part of a beam B0 from a laser light source 1 comes into a photodetector 6 with a splitter 5 as monitor beam BM. Then, the beam transmitted through the splitter 5 is turned to a beam B1 with a vibration plane of an electric vector turning by a rotatable 1/2 wavelength plate 2 to come into a crystal 3 and reflected light BR thereof comes into a photodetector 4. Then, a reflection factor of the crystal 3 is measured from a ratio of intensities of the beams B1 and BR. A change in the intensity of the beam B1 is corrected by a beam BM, thereby enabling accurate measurement of dependence of the reflection factor on an angle of rotation of the beam B1. Thus, a crystal orientation can be determined with a simple method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for optically determining the crystal orientation of a crystal.

[Conventional technology]

As a method for determining the crystal orientation, there is a method of chemically etching the crystal to form etch pits and optically examining the surface state of the crystal (for example, Kyoritsu Shuppan "Crystal Optics Handbook"). According to this, specific etch pits and the like are formed depending on the crystal orientation, so the crystal orientation can be determined without using any special equipment. Moreover, as another determination method, there is a method of observing an X-ray diffraction pattern. According to this, the bonding state of atoms can be recognized as a diffraction pattern, making it possible to determine the crystal orientation extremely accurately.

[Problem to be solved by the invention]

However, the etching method requires empirical methods and requires the use of appropriate etchants, so it cannot be applied to all types of crystals. The method using X-ray diffraction requires expensive equipment and complicated data diffraction, and also requires skill.

Therefore, an object of the present invention is to provide a method and apparatus that can easily determine crystal orientation using a simple apparatus.

[Means to solve the problem]

In the crystal orientation determination method according to the present invention, when a laser beam is irradiated onto a predetermined crystal plane of a crystal whose crystal orientation is to be determined, the optical axis of the laser beam is set so that the vibration plane of the electric vector of the laser beam is set relative to the crystal plane. The intensity of the reflected light from the crystal plane caused by this rotation is measured, and the reflectance is determined from the relationship between the intensity of the laser beam and the intensity of the reflected light. The present invention is characterized in that the crystal orientation of the crystal is determined from the relationship between the reflectance of the crystal plane and the rotation angle of the vibration plane of the electric vector of the laser beam.

Further, the crystal orientation determining device according to the present invention includes a laser light source that emits a laser beam toward a predetermined crystal plane of a crystal whose crystal orientation is to be determined, and a vibration plane of an electric vector of the laser beam that is A vibration plane rotating means for rotating around an axis, a measuring means for measuring the intensity of the laser beam reflected from the crystal surface and determining the reflectance from the relationship between the emission intensity of the laser light source and the reflected light intensity, The method is characterized by comprising determining means for determining the crystal orientation of the crystal from the dependence of the electric vector on the rotation angle of the vibration plane.

[Effect]

According to the present invention, when the electric vector of a laser beam is incident on a crystal plane while rotating its vibration plane, the reflectance of the crystal plane changes depending on the relative relationship between the crystal orientation and the rotation angle of the vibration plane. Therefore, by examining the rotation angle dependence of the reflectance, it becomes possible to optically determine the crystal orientation of the crystal.

〔Example〕

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

FIG. 1 is a perspective view showing the overall configuration of a crystal orientation determination device according to an embodiment of the present invention. In the figure, laser light source 1
is formed by a He--Ne laser or the like that emits a linearly polarized beam B, and the emitted light B passes through a half-wave plate 2 and is irradiated onto the crystal plane of the crystal 3 as an incident beam B. The reflected beam BR reflected by the crystal 3 is incident on a light-receiving probe 4 made of a photodiode or the like, where it is converted into an electrical signal and sent to a determining device (not shown). Here, the beam splitter 5 splits the linearly polarized beam B from the laser light source 1 into an incident beam B1 and a monitor beam BM, and the monitor beam BM is monitored by a light receiving element 6 such as a photodiode.

Next, the functions of the apparatus shown in FIG. 1 will be briefly explained.

First, a linearly polarized beam B from a laser light source 1.

A part of the beam is taken out as a monitor beam BM by a beam splitter 5 and is incident on a light receiving element 6.

Therefore, even when the output of the laser light source 1 fluctuates, this fluctuation can be monitored, so the intensity of the incident beam B incident on the crystal 3 can be accurately grasped. The half-wave plate 2 is rotatable in the direction of the arrow in the figure, thereby rotating the plane of vibration of the electric vector of the incident beam BI. That is, if the 1/2 wavelength plate 2 is rotated by an angle θ around the optical axis of the incident beam B, the above vibration plane becomes 20
can only be rotated. Therefore, the incident beam B1 whose electric vector vibration plane rotates with respect to the crystal 3 can be made incident on the crystal plane of the crystal 3.

It is desirable that the crystal 3 has only the three surfaces shown in FIG. 1 mirror-finished, and the other three surfaces are rough-finished. This is to suppress reflection from the back surface of the crystal 3. When the incident beam B1 is incident on such a crystal 3, a reflected beam BR is generated and sent to the light receiving element 4. Here, if the angle of incidence of the incident beam B with respect to the incident surface of the crystal 3 is too large, the dependence of reflection on the vibration plane of the electric vector is likely to occur. Inject vertically. In addition, in order to improve measurement accuracy, it is desirable to use a light receiving element 4 whose output does not change depending on the position where the reflected beam BR is irradiated. By providing a mechanism for rotating the crystal 3 around the axis), the position of the reflected beam BR incident on the light-receiving element 4 can be adjusted to -.

Under such conditions, if the intensity of the reflected beam BR is determined from the output of the light receiving element 4, the reflectance of the crystal plane of the crystal 3 can be measured from the ratio of the intensity of the incident beam B1 and the intensity of the reflected beam BR. Furthermore, changes in the intensity of the incident beam B due to variations in the output of the laser light source 1 can be corrected by changes in the intensity of the monitor beam BH determined by the output of the light receiving element 6.

Therefore, the dependence of the reflectance on the rotation angle of the vibration plane of the electric vector of the incident beam BI due to the rotation of the half-wave plate 2 can be accurately measured.

Next, we will explain the principle of determining crystal orientation in Figures 2 to 7.
This will be explained using figures.

Generally, the refractive index characteristics of a crystal are expressed by an index ellipsoid. If the main chain of refractive index is n x , n , 2, n , then the ellipsoid is (x/n ) + (y/n ) + (z/n
)2-1x y
z...(1) Represented by: Here, in biaxial crystals, generally n <
n < nyZ.

As shown in FIG. 2(a), if the wavefront normal of light propagating in the crystal is , then the main chain n of an ellipse that passes through the index ellipsoid and is cut by a plane perpendicular to a. n 2 (Fig. 2(b)
) gives the refractive index of the characteristic polarization of the propagating light. For example, the refractive index of light propagating in the X-axis direction and vibrating in the X-axis direction is n 2 , and the refractive index of light vibrating in biaxial directions is n 2 .

Now, consider crystal 3 as shown in Figure 3, and consider the a, b, and c axes, or the x, y axis.
, z-axis cannot be identified.

Therefore, the reflection from the crystal plane is measured using the apparatus of the present invention to identify the crystal axis. Assuming that the output beam (linearly polarized beam B) of the laser light source 1 is incident from the C-axis direction and is vibrating in the C-axis direction, the rotation angle θ of the 1/2 wavelength plate 2 is 0.
When the incident beam B1 after passing through the 1/2 wavelength plate 2 is
The vibration plane does not change from the C-axis direction. When the refractive index is n, the reflectance from the crystal plane is R-f (n-1) / (n+1) l - (
2).

FIG. 4 shows the relationship between the refractive index n and the reflectance R. Let n be the refractive index when the vibration directions of the incident beam B are a, b, and c, respectively.
When a, nb, and n, when θ-O@, R-((n-1)/(n+1)12CC×100% (3).

When the 1/2 wavelength plate 2 is rotated by θ-45°, the incident beam B
The vibration surface of No. 1 is rotated by 90° and becomes in the b-axis direction. Reflectance R
Assuming that the dependence of is obtained on the rotation angle θ as shown in FIG. 5, n > n.

It turns out that it is. The above operation was repeated for the other two surfaces, and the θ dependence of the reflectance was measured.

By examining the magnitude relationship of nb, n, x, y.

The Z axis can be identified.

The above explanation was for the case where each axis and the crystal processing plane were perpendicular. However, if the measurement result of the reflectance R is as shown in Figure 6, the rotation angle θ is shifted by 22.5 degrees compared to Figure 5, so the crystal axis and the crystal machined surface are tilted by 45''. It is presumed that there are.

In other words, it can be seen that it is as shown in FIG. In this case, the crystal 3 can be reprocessed so that the axis and the crystal plane are perpendicular, and the crystal axis can be determined by the method described above.

Various modifications are possible to the present invention.

For example, the absolute value of the refractive index can be roughly calculated from equation (2). If an Ar laser, Kr laser, etc. is used instead of a He-Ne laser, different wavelengths (514, 514,
5nm, 488na, etc.). At this time, a half-wave plate corresponding to each wavelength may be used.

Since the refractive index is larger at short wavelengths, the reflectance is also larger, and therefore measurement accuracy can be improved by using short wavelength laser light.

〔Effect of the invention〕

As explained above in detail, in the present invention, when the vibration plane of the electric vector of the laser beam is rotated and incident on the crystal plane, the reflectance of the reflected light depends on the relative relationship between the crystal orientation and the rotation angle of the vibration plane. Therefore, by examining the rotation angle dependence of the reflectance, it becomes possible to determine the crystal orientation of the crystal using a simple method.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the overall configuration of a crystal orientation determining device according to an embodiment of the present invention, FIG. 2 is a diagram illustrating the refractive index of intrinsic polarization of propagating light, and FIG. FIG. 4 is a perspective view of the crystal to be determined; FIG. 4 is a perspective view showing the relationship between refractive index and reflectance; FIGS. 5 and 6 are graphs showing the rotation angle dependence of reflectance; FIG. FIG. 2 is a perspective view of a crystal whose crystal orientation is shifted. 1... Laser light source, 2... 1/2 wavelength plate, 3...
Crystal, 4.6... Light receiving element, 5... Beam splitter. Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent Attorney
Hase Yoshiki Figure 2 Figure 3 1.0 1.5 2.0 2.5 Ku #r9. n Figure 4 Figure 6

Claims (1)

[Claims] 1. A first step of irradiating a predetermined crystal plane of a crystal whose crystal orientation is to be determined with a laser beam; a second step of relatively rotating the light around the optical axis; and measuring the intensity of the reflected light of the laser light from the crystal plane, and determining the above from the relationship between the intensity of the laser light and the intensity of the reflected light. a third step of determining the reflectance of the crystal plane; and a fourth step of determining the crystal orientation of the crystal from the relationship between the reflectance of the crystal plane and the rotation angle of the vibration plane of the electric vector of the laser beam. A method for determining crystal orientation, comprising: 2. A laser light source that emits a laser beam toward a predetermined crystal plane of the crystal whose crystal orientation is to be determined, and a vibration plane rotation that rotates the vibration plane of the electric vector of the laser beam around the optical axis of the laser beam. means, measuring means for measuring the intensity of the reflected light of the laser beam from the crystal plane and determining the reflectance of the crystal plane from the relationship between the emission intensity of the laser light source and the intensity of the reflected light; and the reflectance. a crystal orientation determining device, comprising determining means for determining the crystal orientation of the crystal from the dependence of the electric vector on the vibration plane rotation angle. 3. The crystal orientation determining device according to claim 2, wherein the measuring means includes a monitoring means for monitoring the emission intensity of the laser light source.