Abstract
The surface photovoltage of zinc oxide fine powder was measured by the Kelvin method. Spectral response measurements show that the photovoltage is produced not only by wavelength light from 300 to 400mμ, but also by longer wavelength light from 500 to 800mμ. In the short wavelength light, the decay of photovoltage on turning off the light is rapid at high light lntensity, but slow at low light intensity. There are also the similar phenomenon with long wavelength light, though the increasing curve is different from that of short wavelength exposure.
During exposure with short wavelength, the photovoltage increases by replacing the ambient air with an inert nitrogen, and, in long wavelength, no change in photovoltage is observed by the same treatment. It may be considered that these behaviors occur from the difference of extinction coefficient of zinc oxide crystal for different wavelength lights.
The photovoltage is proportional to the logarithm of the incident light intensity in both wave-length ranges.
It is suggested therefore that the change in surface charge is less sensitive to the change of light intensity.
