Investigation of Na out-diffusion and structural properties of IGS film during three-stage growth process of CIGS thin film

(In,Ga)2Se3 (IGS) thin films were deposited on Molybdenum (Mo) coated soda lime glass (Mo/SLG) substrates, using physical vapor deposition (PVD) technique, resembling only the first stage of the typical 3-stage growth process of CIGS thin film. The Mo thin films were sputtered on SLG substrates using DC planar magnetron sputtering at working gas (Ar) pressure that varies from 0.6 mT to 16 mT. The sputtering pressure of Mo thin films was varied in order to induce variations in the sputtered films´ morphology and microstructure; as well as to subsequently induce variations in the rate of Na out-diffusion from SLG substrate. The IGS thin film deposition process was carried out with the same conditions of substrate temperature (Ts ∼ 400°C) and deposition rate that are required to accomplish the first stage of the complete typical 3-stage process of a CIGS thin film growth. To gain an understanding of the structural correlation between Mo and IGS films, and the effect of this correlation on Na out-diffusion process from SLG substrate. The Mo and IGS films´ structures were examined by θ/2θ X-Ray Diffraction (XRD) characterization technique. Secondary-ion mass spectrometry (SIMS) was also applied to depth profile the Na, Se, and O in the IGS/Mo films. Whereas, the root-mean-square (RMS) surface roughness of both Mo and IGS films, was determined using Atomic Force Microscopy (AFM).