Effect of film thickness on the structural and physical properties of cdznte thin films

Different thickness of CdZnTe films were deposited onto glass substrates by RF magnetron sputtering from Cd_0.9Zn_0.1Te crystals target. Their structural characteristics were studied by X-ray diffraction (XRD). The XRD experiments showed that the films are polycrystalline and have a zinc-blende (cubic) structure. The crystallite size and micro-strain were calculated. It is observed that the crystallite size increases and micro-strain decreases with the film thickness. The optical measurements showed that the average transmittance of all the samples have is less than 50% in the visible range. The possible optical transition in these films is found to be allowed direct transition with energy gap increase from 1.53 to 1.75 eV. For the electrical properties, the sheet resistivity decreased from 2.582×10 ⁸ to3.069×10⁷ Ohm/sq when the thickness increased from 307 to 823 nm; while the carrier concentration seems to be less affected by the film thickness. This behaviour in electrical properties was explained by the crystallinity and the grain size evolution.