Characteristics of stacked CuInS2 and CuGaS2 layers as determined by the growth sequence

CuInS2 and CuGaS2 thin films have been prepared sequentially from elemental evaporation sources onto conventional soda lime glass substrates heated at 350 °C during the deposition process. The gradient in the structure and composition of the stacked layers has been investigated for the two possible growth sequences. Structural depth profiling and crystallographic phase analysis were performed by grazing incidence X-ray diffraction. The atomic distribution in the films depth was analyzed by X-ray photoelectron spectroscopy combined with sputter etching. Formation of the quaternary compound CuIn1 − xGaxS2, with a high Ga content x > 0.80, has been detected with different distribution depending on the growth sequence.