Structural, morphological, optical and electrical properties of e-beam deposited nanocrystalline CdTe:Cu alloy thin films from mechanical alloyed samples

Cadmium telluride (CdTe) and copper incorporated CdTe (CdTe:Cu) alloys were prepared by mechanical alloying using a planetary ball mill. X-ray diffraction results showed that the prepared CdTe:Cu alloys belong to CdTe cubic system. Surface morphology of CdTe and CdTe:Cu alloys, investigated by scanning electron microscope shows the formation of agglomerated structures of various shapes. The prepared respective sample was used as the source material to deposit CdTe and CdTe:Cu alloy thin films by e-beam evaporation method. X-ray diffraction studies showed that the films grow along (111) plane. The crystallite size of the films varies in the ∼28 to 37 nm range whereas the optical band gap is increased from 1.45 to 1.54 eV with increasing copper concentration in the CdTe:Cu alloy films. The wavelength at which maximum optical transmittance occurred in CdTe is shifted from 900 nm to 837 nm due to various level of Cu concentration in CdTe:Cu alloy films. Intensity of the photoluminescence and Raman spectra of CdTe films is decreased due to increase in the Cu concentration in CdTe:Cu alloy film. Hall measurement studies revealed that 2wt.% and 4wt.% Cu concentration in CdTe:Cu alloy film gives a minimum resistivity of ∼1.8 × 104 Ω cm.