Method and apparatus for determining a material's characteristic

Details Method and apparatus for determining a material's characteristic Method and apparatus for determining a material's characteristic

1989-09-13

1993-12-14

Rosenberger, Richard A.

Optics: measuring and testing

By shade or color

With color transmitting filter

356432, G01N 2125

Patent

active

052707970

ABSTRACT:
A method and apparatus for determining the characteristics of materials, particularly of semiconductors, semiconductor heterostructures and semiconductor interfaces by the use of photoreflectance, in which monochromatic light and modulated light beam reflected from the sample is detected to produce a d.c. signal and an a.c. signal, whereby the d.c. signal is applied to one input of a computer and the a.c. signal is used with another input of the computer which controls the light intensity of the monochromatic light impinging on the sample to maintain the d.c. signal substantially constant. A stepping motor is preferably utilized for varying the light intensity of the monochromatic light which is controlled by a computer to re-establish rapidly a predetermined d.c. signal established during normalization procedures when the light intensity of the monochromatic light changes, especially during change of its wavelength. Additionally, the modulation frequency of the modulated beam and/or the wavelength of the monochromatic light can also be varied by the computer.

REFERENCES:
patent: 4632549 (1986-12-01), Czabaffy et al.
patent: 4765742 (1988-08-01), Davinson
Ginley et al, Photoelectrochemistry and Electrosynthesis on Semiconductor Materials, vol. 88-14, 1988, pp. 468-476.
Shen et al, "New Normalization Procedure for Modulation Spectroscopy," Rev. Sci. Instrum. vol. 58, #8, Aug. 1987, pp. 1429-1431.

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