Physical Characteristics of Nano-Scale

Hikmat S. Hilal's picture
Type: 
Thesis
Year: 
2010
Students: 
Israa Tayseer Lutfi Hamdan
Abstract: 

Polycrystalline CdS thin films were prepared by electrodeposition technique (ED) on fluorine-doped tin oxide (FTO) coated glass substrates. The deposited CdS thin films were exposed to different treatment methods at different experimental conditions. The films were heated to desired temperatures of 100o C, 200oC and 300oC under air. Cooling of heated films to room temperature was achieved using two different methods, slow cooling and quenching.The effect of heat treatment on film characteristics has been studied by: Electronic Adsorption Spectra, Photoluminescence (PL) Spectra, XRD Spectra and SEM Imaging. The efficiency of CdS films was attenuated by altering the values of the pH. The most intensive PL spectra was obtained for the sample prepared with pH = 2.6, annealed at T=200oC and quenched. By using X-Ray Diffraction the analysis indicated a hexagonal phase with lattice parameters (a=b=2.14oA and c=6.8oA) in all samples. The crystallite size for the slowly cooled samples equal to that for as grown samples from~15nm to~40nm, but as we see from the table(4.4) in quenching samples the crystallite size increased here ~(48-65)nm and this is the same in SEM. Quenched CdS electrodes quenched from temperatures above 100oC showed better results than slowly cooled electrodes (higher PL intensity, Larger grain size in SEM images and XRD diffraction, and higher peak intensity in XRD Spectra). The results indicate that physical characteristics of electrodeposited CdS thin films can be enhanced by controlled annealing and cooling. The deposited films were too thin to prevent short circuit. Therefore, their photoelectrochemical characteristics could not be studied here.