Metal-insulator-double semiconductor

This double layer may also form in systems as, for example, the interface between two metals of different nature (with different work functions) or between two immiscible electrolytes and even when one of the two phases is an insulator or a semiconductor [7, 10]. 

Substrates The substrates in microelectronics are mainly Si wafers. For mobile applications, silicon-on-insulator (SOI) wafers increasingly replace bulk Si wafers and for very specific high-frequency applications, III-V compound semiconductors (e.g., GaAs) are used. The majority of substrates in microfabrication are Si wafers, but metal, glass, and ceramic substrates are also common. Particularly when using glass, quartz, and ceramic wafers in CMP processes, it has to be taken into account that they are brittle and easy to break. The situation is worse when the material is also under stress induced by deposited layers. For applications where the backside of the wafer has to be structured (e.g., in bulk micromachining), double-side polished substrates are employed. 

This section presents results that show how the rates of photoelectrochemical processes can be derived from time resolved measurement of the photoinduced current or potential in the external circuit of a photoelectrochemical cell. The capacitance of the Helmholtz-double layer is of the order of lO Fcm , the depletion layer capacitance of an extrinsic semiconductor junction is typically 10 -10 Fcm , while the capacitance of an insulator is orders of magnitude lower. With a value of 100 Ohm for the resistance Rd + R of the cell, the time constant of photoelectrochemical cells is 10 s for metallic electrodes, 10 -10" s for semiconductor electrodes and much lower for insulator electrodes. The rates of photoelectrochemical processes also span a wide range. This makes photoelectrochemical kinetics a rich, albeit demanding, area for research. 

The progress in the discovery and use of new polymer electrodes is briefly discussed. Some of the possible applications of these new electrodes are suggested. As important background information for studying organic polymer electrochemistry, knowledge of the conduction mechanism is needed. The theory of bipolaron formation, as proposed by Bredas, et al., is presented. It is important to study the electrode-solution interface. Double layer models for metal, semiconductor, and insulator electrodes are probed. Recent work and applications of these electrodes are then briefly reviewed. This includes initiatives in the fields of electrode generated reactions, photoelectrochemistry, batteries, and molecular electronics. Finally, the needed areas of research, from an electrochemical point of view, are presented. 

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