Three-dimensional sketching defined

Fig. 5.3. Sketch of Mott-CFO model for covalent semiconductors having three-dimensional cross-linked network structure. The critical energies and define the mobility gap. For T > 0 the mobility m(E) niay be finite in the gap because of thermally assisted tunneling. Ep = Fermi energy. The distribution of localized gap states may be nonmonotonic when defect states of a certain energy are prevalent.

Network materials may be usefully defined as systems in which significant connectivity may be identified and preserved even in relatively disordered states (such as liquids and glasses). Considering material structure in terms of an underlying network can be traced to Zachariasen [1] who sketched a two-dimensional representation of a network formed from a mixture of two- and three-coordinate sites. The network connectivity may result from the percolation of relatively simple, well-defined units (such as the triangles in Zachariasen s image or the tetrahedral Si04 coordination... 

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