Copper diffusion in thin In2S3 layers was investigated by measuring copper concentration profiles with Rutherford Backscattering Spectroscopy (RBS). For this purpose In2S3 layers (thickness 100 nm) were evaporated on crystalline silicon substrates and Cu was diffused from a CuSCN surface layer at temperatures between 150 and 250 degrees C. The CuSCN source layer was removed in pyridine solution before RBS measurements were performed. Diffusion coefficients of Cu in In2S3 were obtained by simulating the diffusion process in a one-dimensional model and comparing measured and simulated Cu concentration profiles. The values of the exponential prefactor of the diffusion coefficient and of the activation energy were 9 x 10(-11) cm(2)/s and 0.3 eV, respectively. (C) 2012 Elsevier B. V. All rights reserved.