Semiconductors surface state manipulation

Manipulating surface states of semiconductors for energy conversion applications is one problem area common to electronic devices as well. The problem of Fermi level pinning by surface states with GaAs, for example, raises difficulties in the development of field effect transistors that depend on the... 

The structure and composition of a nanocrystalline surface may have a particular importance in terms of chemical and physical properties because of their small size. For instance, nanocrystal growth and manipulation relies heavily on surface chemistry [261]. The thermodynamic phase diagrams of nanocrystals are strongly modified from those of the bulk materials by the surface energies [262]. Moreover, the electronic structure of semiconductor nanocrystals is influenced by the surface states that He within the bandgap but are thought to be affected by the surface reconstruction process [263]. Thus, a picture of the physical properties of nanocrystals is complete only when the structure of the surface is determined. 

Polythiazyl (SN), . is an intrinsically metallic polymer. Fibrous highly crystalline samples are obtained by the solid-state polymerization of S2N2. The SN repeat unit has one excess electron and the polymer has a half-filled band. The density of states at Fp is low and (SN) is an anisotropic three-dimensional semimetal. Below 0.4 K, (SN) becomes superconducting both the transition-temperature and the room-temperature conductivity (2x 10 Scm ) are sample dependent. The conductivity of fibrous (SN) is enhanced to 2-4 x lO Scm" by exposure to halogens, which are assumed to form a layer on the surface of the fibres. Although efforts to prepare polymers related to (SN)j, have proved unsuccessful, new synthetic routes to SN) have yielded a better material. Despite the demonstration of efficient carrier-injection into semiconductors, the problems of preparation and manipulation have hindered the commercial use of (SN), ... 

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