Fabrication, characterization, and modification of semiconductor surfaces

The development of a cycle for the formation of CuInSe{dollar}sb2{dollar} by Electrochemical Atomic Layer Epitaxy (ECALE) was studied with a Thin-Layer Electrochemical Cell (TLEC). Surface-limited reactions were observed for each of the individual elements on polycrystalline Au electrodes, and atomic layers of each were successfully fabricated. Layers of Cu{dollar}sb2{dollar}Se, InSe, and InSe{dollar}sb2{dollar} were also successfully fabricated, but the extension to CuInSe{dollar}sb2{dollar} proved problematic due to differences in the stability of atomic layers of Cu and In. It was observed that In atomic layers stripped at potentials for the underpotential deposition (UPD) of Cu atomic layers. Attempts to force the formal potential of Cu to more negative values by complexing with EDTA were observed to impede UPD of Cu on Se. Further studies of Cu activity are necessary before an ECALE cycle for CuInSe{dollar}sb2{dollar} will be possible.; ZnO:Zn phosphor powders were reduced with a basic solution of Sodium Borohydride to attempt to enhance the cathodoluminescence (CL) of the phosphor at low electron acceleration voltages. An increase in CL intensity of approximately 100% was observed at reduction times of 20 minutes. No detectable change in phosphor particle size or surface elemental composition was observed, but Electron Paramagnetic Resonance (EPR) indicated an increase in the concentration of singly-ionized oxygen vacancies ({dollar}Vsb{lcub}o{rcub}spcdot{dollar}) with increasing reduction times. ZnO thin films on Si substrates were studied to elucidate the origin of the increase in {dollar}Vsb{lcub}o{rcub}spcdot{dollar} concentration and its effect on CL enhancement. X-Ray Photoelectron Spectrometry indicated an increase in the surface concentration of hydroxide species. Zn/O peak ratios showed a decrease in the surface concentration of Zn. Cathodoluminescence Surface State Spectrometry (CLSSS) indicated a decrease in band-edge CL intensity, which is interpreted to indicate a decrease in the surface band bending of the ZnO thin film as a function of reduction time. These results suggest that the reduction of the ZnO surface to ZnOH and the corresponding decrease in surface band bending increases the probability of oxygen vacancies trapping electrons. The increase in singly-ionized oxygen vacancies increases the probability of radiative recombination and enhances the CL intensity of ZnO:Zn phosphor powders at all electron acceleration energies.