SPANNUNG FUELS WITH ELECTROTIC CRYSTAL AND SPANISH MEASUREMENT PROCEDURES.

摘要

A potential sensor comprises an electro-optical crystal which is constituted by epitaxially growing a high-resistance cpds. semiconductor on a low-resistance cpd. semiconductor. The electro-optical crystal has a large band-gap in both the low-resistance cpd. and the high-resistance cpd. cemiconductors. In the electro-optical crystal a reflecting dielectric film is formed on the high-resistance cpd. semiconductor. The electric potential of a sample is measured as follows. A sample is placed in close contact with the sensor and the low resistance cpd. semiconductor base is earthed. The sample-sensor system is irradiated with polarised light. A change is detected in the degree of polarisation of the polarised light. The low resistance cpd. semiconductor should not absorb the probe light; hence its band gap must be large. The value of the lattice const and the thermal expansion coeft. of the low and high resistance cpd. semiconductors are close to each other. The resistivity of the low resistance cpd. semiconductor is pref. 10 ohm or less since it functions also as an electrode. The high resistance cpd. should have a high electro-optic const, a large band gap and a resistivity of 10 power 5 ohms cm or higher. The wavelength of the probe light is preferably as short as possible since the change of retardation becomes more noticeable of short wavelengths.