Stoichiometry and local bond configuration of In2S3:Cl thin films by Rutherford backscattering spectrometry

Abstract In 2 S 3 thin films deposited using chemical methods always contain residual elements from the precursors, which modify their properties. As buffer layers in solar cells, the residual elements in the In 2 S 3 layer affect the performance of these devices. The stoichiometry of In 2 S 3 thin films deposited by spray ion layer gas reaction (ILGAR) was studied as a function of the residual Cl from InCl 3 precursor by varying the deposition parameters. The chemical formula was deduced from the elemental composition determined using Rutherford backscattering (RBS). Incomplete sulfurization of the precursor implies that residual Cl − remains bonded to the In 3+ ions while some occupy interstitial and/or antisite positions in the In 2 S 3 matrix. This results in thin films with different stoichiometry, described by the formula In 4 S 6−x Cl 2x+2y . This changes the local bond configuration and geometry and underpins the influence of residual Cl on the physical properties of In 2 S 3 thin films.