Formation of CuIn1 − xAlxSe2 thin films studied by Raman scattering

CuIn1 − xAlxSe2 (CIAS) thin films (x = 0.06, 0.18, 0.39, 0.64, 0.80 and 1) with thicknesses of approximately 1 μm were formed by the selenization of sputtered Cu―In―Al precursors and studied via X-ray diffraction, inductively coupled plasma mass spectrometry and micro-Raman spectroscopy at room temperature. Precursor films selenized at 300, 350, 400, 450, 500 and 550 °C were examined via Raman spectroscopy in the range 50-500 cm− 1 with resolution of 0.3 cm− 1. Sequential formation of InxSey, Cu2 − xSe, CuInSe2 (CIS) and CIAS phases was observed as the selenization temperature was increased. Conversion of CIS to CIAS was initiated at 500 °C. For all CuIn1 − xAlxSe2 products, the A1 phonon frequency varied nonlinearly with respect to the aluminum composition parameter x in the range 172 cm− 1 to 186 cm− 1.