Optical and Electrical Properties of CuAlSe2 Thin Films Obtained by Selenization of Cu/Al/Cu…Al/Cu Layers Sequentially Deposited

Abstract

Optical and electrical properties of CuAlSe2 thin films obtained by selenization of Cu/Al/Cu…Al/Cu layers sequentially deposited have been investigated. It is shown that the expected energy gap (2.67 eV) is measured for well crystallized films, whereas a slightly higher value is measured for films not so well crystallized. Raman diffusion also shows differences between well and poorly crystallized films with peaks corresponding to the reference powder for the former samples. A p-type conductivity is found whatever the crystalline quality of the samples. The conductivity of the films depends also strongly on their crystalline properties. When the films are badly crystallized their conductivity is controlled by highly disordered domains at the grain boundaries. When the films are well crystallized with (112) texturation the room temperature conductivity of the films is three orders of magnitude higher than that of poorly crystallized films. Moreover, in the high temperature range, the different domains of the plot ln (σ) versus (1/T) can be understood by using single crystal models, which demonstrates the high crystalline quality of the films. In the lower temperature range, the conductivity is governed by grain boundary scattering mechanisms.