The Reaction of Oxygen with Lead Selenide

Measurements are described of the oxidation of lead selenide, in the form of a powdered single crystal, at various temperatures in the range from room temperature to 280°C. These were aimed at gaining fundamental information about the photoconductive sensitization of evaporated layers of lead selenide by oxygen. Results obtained indicate that two processes occur during oxidation. In the range of temperature considered the predominating process appears to be the diffusion of oxygen ions to vacant selenium sites in the lattice; this was found to have an activation energy of 17 kcal mol -1 . The second process reveals itself only at the highest temperature employed, and is believed to determine the oxidation rate when all or nearly all the selenium vacancies are occupied by oxygen ions. The postulation of two oxidation processes is supported by earlier electrical measurements on lead selenide evaporated layers exposed to oxygen. Theories of photoconductivity in evaporated lead selenide layers sensitized by oxygen are discussed in relation to these experiments.