臭化銀結晶の光電流

抄録

Spectroscopic characteristic of photocurrent and of photoreverse-current and the creation of electron trapping levels by print out in particular are examined at low temperatures in air annealed silver bromide crystals. The effect of foreign ions on photochemical process is also studied. It is shown that, by irradiation, a great number of electron traps are created in the forbidden gap. These traps have their origin in color-center-like aggregates of silver atoms (green part, easily bleached by halogen gas) and in colloidal specks of metallic silver (red part, produced by strong irradiation). The apparent work function for raising the electron from metallic silver to the bottom of conduction band of the crystal is found to be 1.0 eV. The addition of cadmium ions considerably reduces the effect of irradiation upon the formation of additive photoconductive band, whereas the addition of ferric ions enhances the effect greatly and a marked peculiarity in photo-reverse-current is observed. As a subsidiary phenomenon of interest, when there are a large number of electron traps, the additive band is enhances by low temperature irradiation and at the same time the photocurrent at the edge of absorption band is reduced. This may be explained by the recombination of (shallow trapped) photoelectrons with remaining free holes, the number of which is the number of trapped electrons minus the number of hole traps.