Mercury–cadmium–selenide thin film layers: structural, microscopic and spectral response studies

Chemo-mechanical synthesis of HgxCd1−xSe thin films with a variable mercury concentration has been brought about with an objective to study the physical, microscopic, compositional, structural and spectral changes caused due to the incorporation of Hg2+ in CdSe. The various physical preparative parameters and the deposition conditions such as deposition time and temperature, concentration of the chemical species, pH, speed of the mechanical churning, etc. were optimized to yield good quality films. The compositional analysis showed a non-linear behaviour between the Hg:Cd ratio of the bath and that in the film. The films are polycrystalline over the whole range studied with a predominant wurtzite structure in addition to the cubic zinc blend. The crystallite size determined from the XRD patterns and scanning electron microscope (SEM) micrographs is observed to be increasing with increase in the film composition (x), up to 0.05 and then remained more or less same for higher values of x. The estimated optical gaps showed a monotonic non-linear decrease in the band gap with increasing Hg content in the CdSe.