Electroreflectance experimental results

Photoelectrochemistry (PEC) is emerging from the research laboratories with the promise of significant practical applications. One application of PEC systems is the conversion and storage of solar energy. Chapter 4 reviews the main principles of the theory of PEC processes at semiconductor electrodes and discusses the most important experimental results of interactions at an illuminated semiconductor-electrolyte interface. In addition to the fundamentals of electrochemistry and photoexcitation of semiconductors, the phenomena of photocorrosion and photoetching are discussed. Other PEC phenomena treated are photoelectron emission, electrogenerated luminescence, and electroreflection. Relationships among the various PEC effects are established. 

The second reason for the lack of exploitation of electroreflectance, at least as a probe of electric field distribution, has been the rather limited development of the theory. Whilst the basic equations describing the effect have been known for some time [9], they are of considerable complexity and the simplifications that have been made, such as the Aspnes "third derivative modulation spectroscopy [10] and the extended lineshape theories of Raccah et al. [11] have regions of applicability that may not include all commonly found experimental conditions. There are two difficulties with these theories. The first is that the electric field strengths found in practice in the semiconductors commonly used in electrochemical research may be too high for simple lineshape theories to be applicable the essential requirement of such theories is that the lineshape should be independent of applied d.c. potential, a result not always found in practice, as discussed below. The... 

The steady-state and dynamic properties of the Au(lll)/aqueous electrolyte interface were investigated experimentally with a variety of electrochemical and structure sensitive methods. Examples are impedance measurements [13], electroreflectance [14], LEED [14,15] SHG [16], in-situ surface X-ray scattering [17] and STM [18-20] experiments. In the following paragraph we will only focus on some essential results of our in-situ STM and SEIRAS studies [21,22]. 

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