Published online by Cambridge University Press: 21 December 2004
The incorporation of the doping element Na as well as the impact of this element on the structural, morphological and optical properties of evaporated CuInS2 films on Corning 7059 glass substrates is studied. The element Na was evaporated from a thermal evaporation source. The amount of the Na source was determined to be 0–1 at.% compared with CuInS2 source. The substrate temperature was maintained at 200 °C. The effects of Na on films properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical transmittance and reflectance spectra. SEM observation revealed the increase of the surface crystallinity and an enhancement of surface grain size with Na doping. The optical properties of the CuInS2:Na films revealed direct optical transitions which were attributed to the fundamental edge. The optical band gaps of the thin CuInS2:Na films decrease linearly with increasing the Na concentration. An unstable N type conductivity was firstly determined after what the layers are converted to P-type conductivity.