Electron transfer at n-silicon-methanol junctions

Citation

Shreve, Gary A. (1995) Electron transfer at n-silicon-methanol junctions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/0c04-3j56. https://resolver.caltech.edu/CaltechETD:etd-10222007-110727

Abstract

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One of the first semiconductor systems limited by electron transfer has been explored. Rate constants for electron transfer from n-Si to methyl viologen dichloride [...] and benzyl viologen dichloride [...] in LiC1 methanol solutions have been measured for the first time. The driving force dependence of ket for electron transfer to MVC12 from n-Si has been determined. Best fit to the data gave a reorganization energy of 0.9 eV and a maximum rate constant (ket,max) for this system of [...] . To our knowledge this is the first experimentally determined value for the maximum rate constant predicted by Marcus theory at a semiconductor/liquid interface. This allowed an upper limit of [...] nO greater than [...] to be determined for this system.

This work describes a search for active corrosion of Si in contact with [...] and [...] solutions through the use of very sensitive electrochemical, chemical, and physical methods. For [...] solutions, an upper limit on the active corrosion rate of [...] has been established through direct experimental measurements; thus, a 400 im thick Si photoelectrode in contact with the [...] electrolyte would require over 1500 years to corrode completely at room temperature. An alternative explanation for scanning electrochemical microscopy data published previously claiming [...] is presented, based on the documented existence of an inversion layer at the Si/liquid contact, and shown to be consistent with the available data.

Key differences between the conventional and "irreversible" models of semiconductor photoelectrochemistry are identified and discussed within the framework of experimental observations. Conceptual differences between these two models appear to lie in the treatment of interfacial charge transfer processes for photogenerated charge carriers. It is shown analytically that the two models predict differences in the behavior of the available free energy produced by a photoelectrochemical cell at a fixed incident light intensity and are compared to experimental results for semiconductor/liquid junctions.

Thesis Files