Effect of copper concentration on the physical properties of ZnS:Cu alloys prepared by chemical bath deposition

Abstract

ZnS:Cu thin films were deposited on glass substrates by chemical bath deposition technique. The structural, morphological, optical and electrical properties of the grown films were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectrometry, scanning electron microscopy, spectrophotometry, spectrofluorimetry and Hall effect measurements. Both XRD and Raman analysis indicated the coexistence of both sphalerite ZnS and covellite CuS with cubic and hexagonal structures, respectively. The optical band gap of the films increased from 3.70 to 3.75 eV with Cu concentration increment. Photoluminescence studies revealed that the incorporation of Cu2+ ions in ZnS matrix blue shifted and quenched the emission bands. Electric resistivity, volume carrier concentration, surface carrier concentration and Hall mobility were determined from Hall effect measurements. Indeed, for pure sample, the obtained values were about 7.586 × 104 Ω cm, 1.472 × 1011 cm−3, 2.944 × 106 cm−2 and 5.590 × 102 cm2 V−1 s−1, respectively. However, after Cu incorporation, these values varied in the range of (2.273 × 104–13.80 × 104) Ω cm, (2.334 × 1011–9.094 × 1013) cm−3, (4.668 × 106–1.819 × 109) cm−2 and (3.092 × 10−1–1.937 × 102) cm2 V−1 s−1, respectively.