Role of Cu/S ratio and Mg doping on modification of structural and optical characteristics of nano CuS.

Nano CuS with different Cu to S ratio and also Mg‐doped nano CuS are prepared using a thermolysis procedure under nitrogen flows. The effect of changing copper to sulfur ratio in preparation of CuS under flowing nitrogen and also Mg‐doped CuS on the lattice parameters and crystallite size is studied using X‐ray diffraction data by applying the Rietveld profile method. Scanning electron microscope mapping is used to verify the distribution of different elements over undoped and doped CuS samples. Fourier transforms infrared spectroscopy spectra confirm that the structure of CuS is not altered by doping or changing of the Cu to S ratio. In order to examine the effect of changes of Cu to S or Mg doping on the absorption behavior of nano CuS, ultraviolet spectroscopy is used. The energy gaps of different samples are determined using Tauc's relation. The photoluminescence spectroscopy reveals that all samples exhibit violet and blue sub‐emissions except a CuS with Cu:S ratio 1:4 which also emits green sub‐emission. [ABSTRACT FROM AUTHOR]