Optical and electrical optimization of dysprosium-doped CdS thin films
As-grown and Dy-doped CdS thin films containing concentrations of 1, 2, 3, 4 and 5 at.% Dy atom were prepared via chemical spray route on glass substrates. The constructed thin films were searched through analyzing their structural, morphological, optical and electrical features. X-ray diffraction (XRD) surveys showed that as-grown and Dy-doped CdS thin films had hexagonal structure and the preferential orientation was along (101) plane for as-grown, 1 and 2 at.% Dy-dopings. But further dopings (3 and 4 at.%) caused more random orientation, especially for the case of 5 at.%, the preferred orientation changed to (002) plane. The crystallite size progressively lessened from 39 to 27 nm with increasing Dy-doping. The existence of a close relation between grain shape and the preferential orientation appeared as compared to micrographs of scanning electron microscopy with XRD data. 5 at.% Dy-doped CdS thin films possessed the best transmittance (over 80%) among all the samples. Except for 2 at.% Dy-doped CdS sample, the other samples had almost a band gap of 2.45 eV. Photoluminescence results revealed that more stoichiometric thin films were formed after Dy-incorporations. The outcomes of the electrical investigation evidenced that the best sample was 1 at.% Dy-doped CdS thin films since the lowest resistivity (6.35 × 103 Ω cm) and highest carrier concentration (1.06 × 1014 cm−3) were obtained for this specimen.
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