M. Pilvet

Cu-In and Cu-Zn-Sn Films as Precursors for Production of CuInSe 2 and Cu 2 ZnSnSe 4 Thin Films

The co-sputtered Cu-In precursor layers were characterized by bi-layer surface structure in which island-type crystals were formed in a small-crystalline matrix layer. The elemental composition of the island-type crystals corresponds to the compound CuIn 2 and the matrix (area) consists of copper-rich Cu 11 In 9 phase. The surface morphology of sequentially evaporated Cu-Zn-Sn precursor layers is determined by the deposition order of stacked consistent metal layers. Precursor Mo-Sn-Zn-Cu films exhibit a well-formed “mesa-like” structure of the surface in which larger crystals (about 1,5 μm) are located on a “small-crystalline” valley. For films with other sequences of metallic layers, the mesa like structure is not so well exposed and well formed flat precursor layers were produced replacing separate metallic Cu and Sn layers with Cu/Sn alloy layer. Selenization of both Cu-In and Cu-Zn-Sn precursor layers begins with the formation of binary Cu-selenides with compositions varying with the temperature. At temperatures higher than 370 0 C the selenization of Cu-In results in single-phase CuInSe 2 films in contrast to the selenization of Sn-Zn-Cu films that results always in multi-phase films consisting of high quality Cu 2 ZnSnSe 4 crystals and of separate small-crystalline phase of ZnSe.

Reaction pathway to CZTSe formation in CdI2: Part 2: Chemical reactions and enthalpies in mixtures of CdI2–CuSe–SnSe and CdI2–CuSe–SnSe–ZnSe

The chemical reactions between CuSe, SnSe and ZnSe and their enthalpies in molten CdI2 in closed vacuum ampoules were investigated. Differential thermal analysis (DTA) was used for the determination of the temperatures of processes occurring in the studied mixtures. X-ray diffraction and Raman spectroscopy were performed to discover the phase changes in the long-term annealed samples at higher than peak temperatures in DTA. The occurring chemical reactions and their enthalpies were derived. The recrystallization of CZTSe in CdI2 was investigated. The results confirmed the formation of Cu2SnSe3, Cu2SnSe4, CdSe, Cu2CdSnSe4, Cu2ZnSnSe4, and Zn1−xCdxSe compounds and solid solutions.