Date of Award

1984

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

Photoelectron emission currents from P-GaAs and p-InP into aqueous and non-aqueous electrolytes have been measured and current theories examined critically. The linearized optimal current/potential relation for p-GaAs followed the 3/2 power law and gave the reciprocal power results 0.66 (+OR-) 0.17 and 0.61 (+OR-) 0.09 at pH 7.0 and 11.4, respectively. The threshold potential was -1.00 V (+OR-) 0.09 V(SCE) at both pH's. Corresponding experiments at p-InP gave 0.70 (+OR-) 0.07 for reciprocal power at these pH's and a threshold potential of -0.65 V (+OR-) 0.02 (SCE). Both crystals followed the 3/2 power law for the photocurrent/wavelength relation with work functions of 2.48 (+OR-) 0.12 eV and 2.53 (+OR-) 0.15 eV for p-GaAs and p-InP, respectively. The theoretical square law, which characterizes the photoelectron emitted at energies lower than the volume work function, was tested and both semiconductor followed it closely. The semiconductor surfaces were characterized with Mott-Schottky experiments. It was found that the crystal surfaces changed drastically with time in aqueous electrolytes, especially p-GaAs. These changes decreased the efficiency of the photocurrents and produced deviations from the 3/2 power law. During the performance of these experiments, it was found that nitrous oxide reduced in dark at pH > 9.0. It is postulated that hydrogen reduction and formation of solvated electrons at the interface are involved in this process. In the pH > 9 range an anodic wave was found and assigned to hydride states on the surface of p-GaAs. These hydride states might be the source of atomic hydrogen for the dark N(,2)O reaction. Similar processes were not observed at p-InP nor in nonaqueous systems. Organic solvents were used to study the photoemission currents; however, a full characterization of the process could not be achieved due to the lack of a suitable electron scavenger and the lower efficiencies of the photoemission processes.

Pages

379

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