Semiconductive liquids

Typical results for a semiconducting liquid are illustrated in figure Al.3.29 where the experunental pair correlation and structure factors for silicon are presented. The radial distribution function shows a sharp first peak followed by oscillations. The structure in the radial distribution fiinction reflects some local ordering. The nature and degree of this order depends on the chemical nature of the liquid state. For example, semiconductor liquids are especially interesting in this sense as they are believed to retain covalent bonding characteristics even in the melt. 

All-plastic nonconductive pipe such as polyolefin is not recommended for handling nonconductive or semiconductive liquids except where it can be shown that the advantages outweigh any risks associated with external static ignition or leakage via pinholes, or where tests have demonstrated that the phenomena will not occur. Burying an all-plastic pipe prevents external... 

Where nonconductive and semiconductive liquids must be transferred through plastic piping systems, mitigating strategies include... 

Since the first synthesis of mesoporous materials MCM-41 at Mobile Coporation,1 most work carried out in this area has focused on the preparation, characterization and applications of silica-based compounds. Recently, the synthesis of metal oxide-based mesostructured materials has attracted research attention due to their catalytic, electric, magnetic and optical properties.2 5 Although metal sulfides have found widespread applications as semiconductors, electro-optical materials and catalysts, to just name a few, only a few attempts have been reported on the synthesis of metal sulfide-based mesostructured materials. Thus far, mesostructured tin sulfides have proven to be most synthetically accessible in aqueous solution at ambient temperatures.6-7 Physical property studies showed that such materials may have potential to be used as semiconducting liquid crystals in electro-optical displays and chemical sensing applications. In addition, mesostructured thiogermanates8-10 and zinc sulfide with textured mesoporosity after surfactant removal11 have been prepared under hydrothermal conditions. 

The conductivity of the mobile phase is a major factor in the electrostatic disruption of the liquid surface during ESI nebulization. Stable ESI conditions can only be achieved with semiconducting liquids (conductivity 10 -10 Q m ). Pure organic solvents like dichloromethane, benzene, and hexane are only suitable for ESI after mixing with >10% polar solvent (Ch. 6.3). 

Anomalous neutron scattering was undertaken on the unusual semiconducting liquid InSe. A first peak coordination number of 3 suggested that the underlying cause of the unusual behavior is not related to In-In homopolar bonding. 

The vapor phase of liquids like sulfur and selenium consists mainly of small species containing only a few atoms. The liquid-vapor equilibria of selenium and sulfur therefore correspond to equilibria between extended structures (chains) and small molecular species. To the extent that the electronic properties of the liquid phase are determined by the molecular structure, there is necessarily an electronic transition accompanying the liquid-vapor transition. For selenium the transition is one from a semiconducting liquid to an insulating vapor. 

It may be helpful at this point to summarize briefly the characteristic differences between fluid metals and semiconductors with respect to the state-dependent interaction. Compared with typical metals, the state-dependence of the interparticle interactions in semiconductors is much more closely associated with specific features of the fluid structure. In the liquid chalcogens, for example, these ttike the form of various molecular species including polymeric chains. In semiconducting liquid alloys, it is the short-range correlation of unlike atoms that is important. Consequently, as will be evident in chapter 5, experimental studies of fluid semiconductors are inevitably focused on the fluid structure, either with direct structural probes or more indirect methods such as magnetic studies. Determination of the arrangement of atoms in metallic liquids is also... 

The other major difference between fluid metals and semiconductors concerns the phase behavior and the electronic character in various regions of the temperature-density plane. The low-temperature liquid-vapor equilibrium of semiconducting liquids involves two nonmetallic phases whereas the vapors of metallic elements are, by definition, in equilibrium with a liquid metal phase. The metallic state develops in fluid semiconductors when the temperature and pressure are high enough to disrupt the structural order responsible for semiconducting electronic structure. If this occurs near the critical region, there exists the possibility of rapid MNM transitions and strong interplay between the electronic properties and critical density fluctuations. In this respect, fluid metals and semiconductors behave similarly under extreme conditions whereas they are markedly different near their respective triple points. 

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 dominant role of the temperature-dependent carrier concentration implied by Fig. 5.8 permits us to draw some semi-quantitative conclusions about electronic transport in semiconducting liquid selenium. Using the simple semiconductor model, we can estimate the carrier mobility from Eq. 5.2 from the fitted prefactor in Eq. 5.1. For this purpose we assume that the carrier masses are not too different from the free electron mass, that is, nig — nif, mo- This yields an estimated carrier concentration at 400 °C, 2 3 x 10 cm. The corresponding... 

Zhang, R, Funahashi, M., Tamaoki, N. High-performance thin film transistors from semiconducting liquid crystalline phases by solution processes. Appl. Phys. Lett. 91(6), 063515 (2007)... 

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