Oxides and Semiconductors

In this chapter the electrochemical properties of materials with covalent bonds and stoichiometric composition will be described. Many of these materials are semiconductors. In the literature there is a classical description of their electrochemistry by Morrison. Memming has given a comprehensive review on semiconductor electrochemistry, Sato has described the electrochemistry for oxides and semiconductor electrodes, and Trasatti has edited a book on catalytic aspects of oxides. 

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Gerischer H (1989) Neglected problems in the pH dependence of the flatband potential of semiconducting oxides and semiconductors covered with oxide layers. Electrochim Acta 34 1005-1009... 

A variety of spectroscopic methods are available to investigate properties of semiconductors and oxides with relevance to the electrochemistry of these materials. These methods are often divided into in situ and ex situ methods. Some methods are described in other chapters (Chapters 7 and 11). Some aspects that are more closely related to oxides and semiconductors will be described in this chapter. Detailed descriptions exist and summaries of reviewing papers are found in the literature. - ... 

The general importance of microscopy for surface investigations is reflected in the in situ applications of optical microscopy, scanning tunneling microscopy (STM), and atomic force microscopy (AFM) to oxide and semiconductor electrodes. The methods were described in Chapter 4. Of equal importance for oxide and semiconductor electrodes is the application of ex situ methods like scanning electron microscopy (SEM). 

The application of STM to oxide and semiconductor electrodes differs from STM on metal surfaces. The problems are described in the literature and in special reviews, e.g., by Allongue. ... 

The impedance response obtained for polished -i- etched crystals and polished -I- etched -i- oxidized crystals (Figure 4.3.13a and b, respectively) show qualitatively different behavior, the principal one being the addition of at least one more time constant in the oxidized case as manifested by (at least) one additional peak in the imaginary part in Figure 4.3.13/ . Such behavior is reasonable since there is an additional interface between the oxide and semiconductor. 

Abstract Adsorption-desorption studies addressing the influence of surfaces and gas molecules associated to energy concepts and different mechanisms and models based on ideal and non-uniform surface energy on metals, metal oxides and semiconductors. 

Intercalation-induced stresses have been modeled extensively in the Hterature. A one-dimensional model was proposed to estimate stress generation in the lithium insertion process in the spherical particles of a carbon anode [24] and an LiMn204 cathode [23]. In this model, displacement inside a particle is related to species flux by lattice velocity, and total concentration of species is related to the trace of the stress tensor by compressibihty. Species conservation equations and elasticity equations are also included. A two-dimensional porous electrode model was also proposed to predict electrochemicaUy induced stresses [30]. Following the model approach of diffusion-induced stress in metal oxidation and semiconductor doping [31-33], a model based on thermal stress analogy was proposed to simulate intercalation-induced stresses inside three-dimensional eUipsoidal particles [1]. This model was later extended to include the electrochemical kinetics at electrode particle surfaces [2]. This thermal stress analogy model was later adapted to include the effect of surface stress [34]. 

Figure 13. (HgCd)-Te02-(HgCd)Te surface behavior diagram of Hgo8Cdo2Te with a 1600 A thick anodic oxide. The superimposed depth scale gives the equivalent thickness of oxide for an abrupt interface and a mean free path of 16 A. The dashed line represents the depth profile path for a stoichiometric oxide and semiconductor. (With permission of Elsevier Science Publishers.)...

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