Intrinsic defects doping in spray deposited CuInS2 thin films

Thin layers of copper indium disulfide CuInS2 were prepared on corning glass substrate at 300 degrees C by the chemical reactive spray process from an aqueous solution containing cuprous and indium chlorides CuCl2, InCl3 and thiourea SC(NH2)(2). The Cu/In molar ratio is varied from 0.5 to 1.5 whereas the Sulfur concentration was maintained constant at 0.04 mol/l in the precursor's solution. Films bulk composition and surface morphology were analyzed by Electron Microprobe Analysis (EMPA) and Scanning Electron Microscopy (SEM). Surface topography of submicron crystallites were observed by Atomic force microscopy. Electrical conductivity was investigated by hot probe and hall-effect methods. It was found that films grown under Cu rich condition have p type conductivity with a hole concentration of order of 1020 cm(-3) in the bulk. The resistivity of the films was found to decrease with the increase of the copper to indium ratio in the precursor solution. Raman spectrum of copper deficient films show A(1) (290 cm(-1)) and A*(1) (305 cm(-1)) vibration modes due to Chalcopyrite (CH) and Copper Gold (Au /Cu) ordering in the films. CuInS2 possesses a number of intrinsic (native) defects which controls the doping of the films. The initial composition of precursors solution is critical to determine the nature of defects (interstitials, vacancy or substitution) and the conductivity type of the deposited films. CuInS2, thin layers deposited from copper-rich solutions resulted in p type CIS films with a high conductivity. The objective of this work is to investigate the role of cations concentration ratio in the sprayed solution on the electrical, optical and structural properties of CuInS2 deposited layers.