High-temperature spectrophotometry of indium chloride vapours as a method of study of the In - Se system
The goals of this work are as follows: (а) searching for a method of study of the In - Se system taking into account the specified problems and difficulties, (b) choosing a way for the instrumental implementation of this method, and (c) obtaining experimental evidence that this method and its implementation are promising. The choice of the In - Se system is related to the fact that indium selenides, layered structures and semiconductor phases with stoichiometric vacancies, are promising from the point of view of materials science. This choice is also related to the use of binary precursors for the synthesis of heterostructures based on CIS compounds. We studied the possibility of applying the auxiliary component method using the equilibrium with the participation of indium chloride vapours which were made to contact the condensed phases of the In - Se system. Equilibrium was achieved using high-temperature spectrophotometry of the vapour phase. The experiment had two stages. During the first stage we determined the absorption characteristics of the InCl<sub>3</sub> vapour. During the second stage we studied the heterogeneous equilibrium of the unsaturated indium chloride vapour with several phases of the In - Se system. Over the course of the study, we determined the molar attenuation coefficients of the InCl<sub>3</sub> vapour and plotted the temperature dependences of the value K<sub>P</sub><sup>#</sup>. It was found that the phase composition of the alloys significantly influences the position of the corresponding lines on the K<sub>P</sub><sup>#</sup>-T diagram, which proves the possibility of using the suggested auxiliary component method in its specific instrumental (spectrophotometric) implementation in order to study the In - Se system. We also showed the additional possibilities of using this method for plotting T-x diagrams of binary systems in such high-temperature areas where the binary solid phase is in equilibrium with the melt. This application of the method is related to the solubility of a vapour of an auxiliary component (chlorine in the form of indium chlorides) in the melts of binary phases (indium selenides).