The Effects of Oxygen on Evaporated PbSe Films

Evaporated PbSe films were oxidized at the temperature range of liquid-air temperature to 300°C. These films were converted from n-type to p-type through the quasi-intrinsic state with the lapse of oxidation time. The photoresponse of these films at the quasi-intrinsic state were observed. The film oxidized at 200°C gave the maximum photosensitivity. Furthermore, the temperature dependence of the electric current in the quasi-intrinsic film was measured at room temperature down to liquid-air temperature, and the desorption process of oxygen was studied. In this film oxygen is chemi-adsorbed onto the particle surface, produces the acceptor level by diffusing into the bulk of the particle, or forms the oxide layer by reacting with the particle. But oxygen contributing directly to photosensitization is the one which forms acceptor level in the bulk of the film by diffusing into the particle.