Amorphous semiconducting liquid

The fourth volume concentrates mainly on the properties of semiconducting compounds, including transition-metal silicides, amorphous and liquid semiconductors, and particularly the nature of the chemical bonds in these materials. 

The microscopic mechanisms for the MNM transition described in the previous section are quite general. They can be related to a wide variety of physical systems. These include not only expanded electronically conducting fluids, but liquid solutions such as the molten metal-salt solutions, metal-ammonia solutions, semiconducting liquid alloys, etc. The mechanisms are also relevant to the MNM transitions in various solids, including amorphous semiconductors, heavily doped crystalline semiconductors, and metal oxides. Our concern is with fluids and so we turn now to summarize briefly some of the theoretical investigations specifically focused on the MNM transition and its relation to the phase transition behavior of fluid metals. 

The electrical properties of semiconductors depend on the perfection of the crystal structure and the nature of the impurities it contains. However, the decisive factor responsible for semiconductor properties is the short-range order. By this is meant the symmetry of the electron shells, the valence an es, the interatomic distances, etc., i.e., the nature of the forces of the chemical interaction between the atoms. This is indicated by the fact that the semiconducting properties of many crystalline semiconductors are retained after melting [1] and also by the existence of a large number of liquid, amorphous, and glassy semiconductors. 

Among liquids that may exhibit a liquid-liquid phase transition, a feature, that is, special to silicon (though not uniquely so see earlier discussions) is the change in electronic properties that accompany the liquid-liquid phase transition. Indeed, this is a feature that has been exploited in studies from early on in experimental probing of the transition. The amorphous-amorphous transition in silicon has been also found to be a transition from a semiconducting low-density state to a metallic high-density state. The liquid form of these phases has shown similar change in the... 

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