Studies on the Physical Properties of Cadmium Telluride Nanostructure Thin Films

Abstract

Among Π-VІ semiconductor binary system microstructure, Cadmium Telluride is of technological importance in optoelectronic devices, detectors and solar cells application. On the other hand, devices based on nanomaterial have a great potential application in all of fields in human life. Nano-structure CdTe coming to replace microstructure CdTe due to its great benefits in solar cell application, optoelectronic devices, bio-imaging and PH sensitive detectors. Nanostructure CdTe in form of quantum dots (QDs) have been synthesized using hot injection chemical technique. Three samples with different particle size have been synthesized. CdTe QDs thin films have been deposited by thermal evaporation technique. The CdTe QDs powder and the as deposited films were characterized using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM).The X-ray analysis shows that both CdTe QDs powder and the as deposited films crystallize in cubic zinc-blende type structure. The optical properties of the as deposited films have been characterized by using double beam UV-Vis-NIR spectrophotometer Abstract XIII at normal incidence. The optical band gaps have been found to tunable with the variation of particle size, which attributed to quantum confinement effect. The optical constants (refractive index and absorption coefficient) also have been calculated. The refractive index in non-absorbing region was found to decrease than its value in microstructure CdTe. The dispersion parameters also have been calculated by using classical models and some empirical relations. The photovoltaic properties and current conduction mechanisms of dark (I-V) characteristics of Au/CdTe QDs/p-Si/Al heterojunction diode were studied. In this thesis, all the obtained-calculated- data were compared with the data from literature for microstructure CdTe. The results confirm the importance of CdTe QDs in solar, detectors and sensors