Natalia Maticiuc

Annealing effect on CdS films: transition from glass to ITO

Structural and optical properties of CdS films deposited on glass and ITO substrates and annealed in H2, N2 or H2+N2 atmospheres at 250 °C and 400 °C were compared. The optical thickness 405±10 nm of the CdS films was found not to be influenced by any annealing conditions or substrate. The as deposited films on both substrates had similar diffraction patterns with one narrow peak corresponding to the (111) cubic plane at 2θ 26.70° and 26.75°, respectively. Higher density of nucleation centres on the ITO surface generated denser CdS films. In the annealing process of CdS/ITO a slower shift of both (111) peak and lattice constant was observed in the direction of pure zinc blende modification. Similar values of band gap and transmittance were determined for as-deposited CdS while annealing at 400 °C decreased transmittance by 5% and 16% for CdS on glass and ITO, respectively. Transmittance dropped because of the destruction of hydroxide group in the CdS lattice, the formation of cadmium excess and the reduction of SnO2 to black SnO in the ITO structure.

Structural and optical properties of ZnTe thin films

Thin films of ZnTe have been prepared by close spaced sublimation technique. The deposited films have been characterized by using optical absorption, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Structural investigations performed by X-ray diffraction technique showed that studied samples are polycrystalline and have a cubic (zinc blende) structure. XRD patterns have been used to determine the microstructural parameters (crystallite size, lattice parameter) of investigated films. Surface morphology studies SEM shows that the grains are uniformly distributed over the entire surface of the substrate. Optical properties of ZnTe films were studied extensively in the range of incident photon energy (0.5-4.0) eV. In the studied ZnTe films the direct transitions take place.

Influence of technological conditions on the properties of CBD CdS layers

This work evaluates the efficacy of the chemical bath deposition (CBD) and technological conditions for preparation of homogeneous CdS thin films with high transparency and low resistivity. The effects of various technological parameters (magnetic agitation of solution, pre-treatment in vacuum, annealing in hydrogen atmosphere, and concentration of chlorine as dopant in the deposition bath) on morphology, transmittance and electrical properties were studied. Together, these results show that CBD is an efficient technique, helpful for the scaling-up of the manufacturing process of suitable and reproducible window n-type CdS layers for further solar cell application.