Influence of sulfurization on optical properties of CdS nanocrystals

Optical properties of 1D nanocrystals of cadmium sulfide synthesized by vapor– liquid–solid growing were investigated as the function from such technological parameter as overpressure of sulfur vapor at the synthesis process or post-processing by the additional annealing in the sulfur atmosphere (sulfurization). The analyses of UV-vis absorption and photoluminescence spectra indicate considerable dependences of CdS nanocrystals optical parameters from sulfur compensation degree at the synthesis process. The photo- luminescence spectra are characterized by changing the ratio of intensities of the defect level and near band edge emissions at overpressure sulfur vapor treatment. A significant decrease in the intensity of defect level emission after the growth or post-growth treatment in sulfur vapor has been observed. Optical absorption edge calculated using the Tauc relation demonstrates improvement of the crystal structure, which is reflected by the rising optical band gap value that approaches to the value for the bulk material at curing of sulfur vacancies by different technological ways. Optical properties obtained by absorption and luminescent measurements demonstrate total correlation, which corresponds to applied technology.