Reversible Cu2-xSe⇆Cu3Se2 phase transformation in copper selenide thin films prepared by chemical bath deposition

This paper reports the inter phase conversion of Cu2-xSe and Cu3Se2 thin films prepared using the chemical bath deposition (CBD) technique. Chemically prepared Cu2-xSe phase is found to be less stable than the Cu3Se2 phase in ambient conditions. With aging the Cu2-xSe phase gets converted to the Cu3Se2 phase along with the formation of copper oxide impurity. The Cu3Se2 phase is stable in ambient conditions but is unstable at temperatures above 140 degreesC where it reverts to the Cu2-xSe phase. This inter phase conversion is found to be cyclic. The relative stability of these phases is studied in detail with the help of X-ray diffraction, optical absorption and X-ray photoelectron spectroscopy. (C) 2001 Elsevier Science B.V. All rights reserved.