Role of Cl on diffusion of Cu in In 2 S 3 layers prepared by ion layer gas reaction method

Abstract

Ion layer gas reaction (ILGAR) method allows for deposition of Cl-containing and Cl-free In 2 S 3 layers from InCl3 and In(OCCH 3 CHOCCH 3 ) 3 precursor salts, respectively. A comparative study was performed to investigate the role of Cl on the diffusion of Cu from CuSCN source layer into ILGAR deposited In 2 S 3 layers. The Cl concentration was varied between 7 and 14 at.% by varying deposition parameters. The activation energies and exponential pre-factors for Cu diffusion in Cl-containing samples were between 0.70 to 0.78 eV and between 6.0 × 10 -6 and 3.2 × 10 -5 cm 2 /s. The activation energy in Cl-free ILGAR In 2 S 3 layers was about three times less compared to the Cl-containing In 2 S 3 , and the pre-exponential constant six orders of magnitude lower. These values were comparable to those obtained from thermally evaporated In 2 S 3 layers. The residual Cl-occupies S sites in the In 2 S 3 structure leading to non-stoichiometry and hence different diffusion mechanism for Cu compared to stoichiometric Cl-free layers.