Synthesis of CuInS₂ through laser impulse processing of Cu-In bimetallic films in sulphureous fluids

Abstract
Laser synthesis of thin films of semiconducting compounds is a highly promising method in microelectronics. It is technologically simple and makes possible the control of the size of thin film structures. The processing of single- and multy-layered films in chemically active media is markedly non-linear in the kinetic parameters of the reaction which facilitates the synthesis of single-phase films (i.e. through "phase selection") with specific chemical and physical properties. The paper features the synthesis of CuInS₂ through pulsed laser treatment of bimetallic Cu-In films in sulphureous fluids. CuInS₂ is currently regarded as a promising material for high efficiency solar cells. Non-stoichiometric bimetallic Cu-In films (0,5µm Cu + 0,2µm In) on glass ceramic bases, used as samples, were irradiated by single pulses of an Nd-glass laser under a laser of sulphureous fluid 1,5-2,0 mm thick containing 80 g per litre of sulphur. The samples were processed in the free-lazing (T = 10^-3s) and Q-switched modes (T = 10^-3s) with power density equal to (1,2-1,4)*10⁹ and 3,3*10⁴ - 1,0*10⁶ wt/cm², respectively. The X-ray analysis has revealed that the formation of CuInS₂ is restricted to the samples processed with ultrashort high-power pulses. No traces of CuInS₂ have been detected in the samples treated by single pulses of 10^-3 s in the given power density range. Selective formation of CuInS₂ phase in the free-lazing mode can be explained in terms of retarted chemical relaxation of the reacting system and the shock wave generated by ultrashort laser pulses in the process fluid and accelerating the chemical reaction.