Optical diagnostics of laser evaporation of CuInS2 polycrystalline compound

Abstract

In the radiation spectrum of the erosion laser plasma of CuInS2 polycrystalline compound, the presence of resonance spectral lines of CuIn and InI is revealed, as well as of spectral lines which correspond to cascade transitions and of lines from the displaced terms of the copper atom. No intense radiation of positive ions is observed in the spectral range from 200 to 600 nm. The binding energies of Cu–S, In–S, Cu–Cu, In–In, and Cu–In atoms, as well as atomic and orbital bond orders of the CuInS2 cluster, are calculated by the Hueckel pseudoempirical method within the valent approximation. It is found that In(1, 3) atoms inversely centering the lower faces of cations Cu(6, 6I), as well as cations Cu(4, 4I ) and In(5, 5I ) centering the lateral faces of the crystal, do not form strong bonds in the structure. Therefore, in the evaporation processes they must easily evolve from the structure of the CuInS2 chalcopyrite crystal and make a predominant contribution to the radiation spectrum of laser plasma. From the standpoint of energy, the atoms of sulfur and nodal atoms of copper evaporate mainly in the form of combined complexes of CuS molecules. One can assume that the initial growth layers will be obtained with a deficiency in sulfur and with substantial violation of their stoichiometry and the structure of the initial compound.