Effects of oxygen and chlorine on the interfacial crystallization of amorphous selenium films

The interfacial crystallization of vapor deposited selenium films has been investigated. It is shown that the interfacial crystalline layer does not form immediately upon condensation of the vapor on aluminum substrates held at 80 °C but forms by crystallization of the condensed amorphous phase. This transformation gives rise to a highly imperfect crystalline layer. Trace amounts of oxygen which can not easily be detected analytically increase the interfacial crystallization rate of selenium. The addition of chlorine to selenium is shown to have the opposite effect. Films fabricated from selenium containing more than 1000 ppmw of chlorine do not show any crystalline formation at the interface. The relationship between our findings and earlier work on the crystallization behavior of melt quenched selenium is discussed.