Reconstructions of Elemental Semiconductor Surfaces

This is a huge issue and one that will be covered at length throughout this and subsequent volumes. Very often, elemental semiconductors exhibit a much richer variety of reconstructions than metal surfaces do [115, 116], fortunately, much of the qualitative insight into semiconductor surfaces has been condensed into a series of general principles, first laid down by Duke [117, 118] and discussed at length in several other books [116, 119]. A discussion of the relevant principles along with a few examples is sufficient to provide a flavor of how some of the most common elemental semiconductor surfaces behave. 

The first principle that we discuss here is often described as the basic or guiding principle of semiconductor surfaces, and it states that the surface structure observed will he the lowest free energy structure kinetically accessible under the preparation conditions. This, rather obvious statement, is true of any surface. However, it is especially pertinent to semiconductors since which surface is observed is known to depend sensitively on cleavage, annealing, and growth conditions. 

Stemming from the guiding principle is a series of other principles. Of relevance to the present discussion on elemental semiconductors is one that basically implies that a surface tends to minimize the number of dangling bonds by 

15) Duke arrived at five principles. Only the four of relevance to elemental semiconductor surfaces are discussed here. The fifth states that surfaces tend to be auto-compensated , which is simply a principle prohibiting the accumulation of charge at the surface. Duke s principles were first 

As we have indicated already, the bulk-truncated (111) surface of Si is unstable and undergoes reconstruction, notably to (2x1) and (7x7) phases. We discuss here the simpler (2x1) reconstruction and refer the interested reader to many of the other texts, including Chapter 1, which describes at length the nature of the (7x7) reconstruction, which is indeed not only the most famous but also the most complex reconstruction in surface physics (e.g., [116, 118, 119, 127, 128]). 

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