How quantum confinement comes in chemically deposited CdS?—A detailed XPS investigation

Chemically deposited thin films of cadmium sulfide (CdS) nanoparticles are analyzed using different techniques to estimate the origin of quantum confinements of CdS clusters in the film. The increase of Cd(OH)2 in the sample with the increase of pH of the bath, observed in XPS depth profiles, depicts the possibility that the CdS clusters of finite size are embedded in Cd(OH)2 surroundings, which ultimately makes the clusters electrically isolated and hence providing carrier confinements. X-ray diffraction and optical absorption studies on these films indicated clear clustering and subsequent carrier confinement effects. An XPS of the same film, after 1 month, shows the conversion of surface layers of Cd(OH)2 into CdO, which is rather a conducting compound.