Abstract
Cu(2)HgI(4) powder has been prepared by precipitation from reactive chemical solutions. An electron beam gun evaporation system was used to deposit the prepared powder in a thin film form onto a Corning 7059 glass substrate. The x-ray diffraction study reveals that the as-deposited films are polycrystalline in nature and have a composition corresponding to the Cu(2)HgI(4) single phase. The differential thermal analysis curve exhibits a strange endothermic peak located at a temperature of 355.5 K, corresponding to the phase change from the first-order phase to the fast ion-conducting phase. The phase change is accompanied by a colour change from bright-red (beta-phase) to dark-brown (alpha-phase). The optical properties of as-deposited films have been calculated from the recorded transmission and reflection data in the spectral range 600-2500 nm. The refractive index of the as-deposited films was found to follow the two-term Cauchy dispersion relation and is adequately described by the effective-single-oscillator model. The refractive index-wavelength variation leads to the determination of the oscillator parameters E(o) and E(d) to be 3.113 and 9.883, respectively. The static refractive index, n(o)(0), and static dielectric constant, epsilon(s), were also calculated as a result of the latter data and were found to be 2.043 and 4.175, respectively. The analysis of the optical absorption coefficient confirmed the presence of a direct optical transition with a band gap energy of 1.96 eV.