Analysis of the Mechanistic Aspects Involved in PS Formation

Any models attempting to describe the overall formation mechanism of PS must consider the fundamental electrochemical reactions in three essential aspects (1) nature of reactions, reactants, products, intermediates, number of steps, and their sequences, (2) nature and rate of charge transport in the different physical phases at the silicon/elec-trolyte interface, and (3) spatial and temporal distributions of reactions and the cause of such distributions. Also, the models have to take into account every factors determining the PS morphology such as doping type and concentration, orientation of silicon, HF concentration, pH, illumination light wavelength and intensity, current density and potential. 

The first and second aspects have been extensively investigated and reasonably well characterized as can be appreciated by the results described in Chapters 2-5. The third aspect, on the other hand, is still not well characterized due to its complexity. However, it is this aspect that determines the specific morphology of PS formed under given conditions. It is not yet clear how this aspect can be described with an integral model in accordance with the morphology of PS. Nevertheless, the spatial and temporal distributions of reactions are governed by the elements and events involved in the system. The following is an attempt to qualitatively sort out the physical schemes of these elements and events and their relative importance in the context of the overall system. 

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