Cadmium telluride and cadmium sulfide thin film preparation using RF planar magnetron sputtering

The objective of this dissertation is to develop the radio-frequency (rf) planar magnetron sputtering method for preparation of CdS/CdTe thin-film solar cells and to optimize the deposition conditions. The underlying physics of thin film preparation by rf magnetron sputtering, including the glow discharge, sputtering, particle transport, and thin film growth processes, was intensively investigated and discussed. The distribution of the electrical and magnetic fields in the sputtering system was numerically computed and measured. The preparation processes were diagnosed by Langmuir probe measurements, optical emission spectroscopy, and growth rate measurements. The plasma parameters, such as the plasma potential, the density and the temperature of electrons, the energy and the flux of ions bombarding the substrate, and the substrate self bias, were measured. The optical emission and growth rate as functions of deposition conditions were studied. The preparation-structure relations were systemically investigated by using scanning electron microscopy (SEM). The effects of the growth conditions on the microstructure of thin films were analyzed. The optimized preparation parameters based on the investigations above and the early work of our group are presented in this dissertation. It is by following these optimized conditions that our group, to date, holds the record of the highest solar cell efficiency by this preparation method.