Silicon transport properties

In the early 1970s, Spear and coworkers (Spear, 1974 Le Comber et al., 1974), although unaware of the presence of hydrogen, demonstrated a substantial reduction in the density of gap states (with a corresponding improvement in the electronic transport properties) in amorphous silicon films that were deposited from the decomposition of silane (SiH4) in an rf glow discharge. 

K. Okita, Y. Harima, K. Yamashita, and M. Ishikawa, Synthesis and optical, electrochemical, and electron-transporting properties of silicon-bridged bithiophenes, Organometallics, 18 1453-1459 (1999). 

The fabrication of active semiconductor devices from amorphous semiconductor films is a further application that offers considerable advantages. Thin-fihn transistors, based on amorphous films of hydrogenated silicon, are nnder intensive development. Other devices with monostable and bistable switching characteristics have also received considerable interest. Naturally enough, the performance of snch devices is intimately related to the transport properties of charge carriers in the materials employed. 

Little is known about the interactions between the transport properties in the melt and the production of defects at the melt-crystal interface. An exception is the swirl microdefect seen during processing of dislocation-free silicon wafers (118). The origins of this defect (119) are related to temperature oscillations and remelting of the interface. Kuroda and Kozuka (120) have studied the dependence of temperature oscillations on operating parameters in a CZ system but have not linked the oscillations to convective instabilities in the melt. 

Lopour P, Janatova V (1995) Silicone rubber-hydrogel composites as polymeric biomaterials. VI Transport properties in the water-swollen state. Biomaterials... 

The transport properties of hydrogen in silicon are complicated by trapping processes and molecule formation. For single-crystal silicon with low defect concentration (<10 cm ), diffusion coefficients on the order of 10 ernes have been measured [41]. 

Molecular dynamics simulations entail integrating Newton s second law of motion for an ensemble of atoms in order to derive the thermodynamic and transport properties of the ensemble. The two most common approaches to predict thermal conductivities by means of molecular dynamics include the direct and the Green-Kubo methods. The direct method is a non-equilibrium molecular dynamics approach that simulates the experimental setup by imposing a temperature gradient across the simulation cell. The Green-Kubo method is an equilibrium molecular dynamics approach, in which the thermal conductivity is obtained from the heat current fluctuations by means of the fluctuation-dissipation theorem. Comparisons of both methods show that results obtained by either method are consistent with each other [55]. Studies have shown that molecular dynamics can predict the thermal conductivity of crystalline materials [24, 55-60], superlattices [10-12], silicon nanowires [7] and amorphous materials [61, 62]. Recently, non-equilibrium molecular dynamics was used to study the thermal conductivity of argon thin films, using a pair-wise Lennard-Jones interatomic potential [56]. 

Membranes fabricated using the MEMS technology are finding an increasing number of applications in sensors, actuators, and other sophisticated electronic device. However, the new area of application of MEMS is creating new materials demands that traditional silicon cannot fulfill [43]. Polymeric materials, also in this case, are the optimal solution for many applications. Microfabrication of polymeric films with specific transport properties, or micromembranes, already exists, and much work is in progress [44-50]. 

M. L. Ciurea, V. lancu, V. S. Teodorescu, L. C. Nistor, and M. G. Blanchin, Microstructural aspects related to carrier transport properties of nanocrystalline porous silicon films, J. Electrochem. Soc. 146(9), 3516, 1999. 

Surface and transport properties of solvents are very important for solvents. Surface tension of a solvent shows how easy or difficult it would be to wet the surface on which the solvent is being applied. Low surface tension implies better wetting ability and vice versa. Water and other polar organic solvents have very high surface tension, whereas silicones, fluorocarbons, and aliphatic hydrocarbons have low surface tension. Solvents with low surface tension are easier to leak through threaded joints compared to those with high surface tension. 

Maroudas, D, and Brown, R. A., Calculation of thermodynamic and transport properties of intrinsic point defects in silicon. Phys. Rev. B 47,15562-15577 (1993). 

Pentacene is attracting considerable attention as its charge transport properties are excellent [4, 48], and films of pentacene on silicon oxide are commonly used for thin film transistors in which the silicon oxide serves as gate dielectric. 

Recent evidence indicates that the influence of molecular structure on gas permeation through polymers is complex. For example, reports investigating series of structurally varied polyimides (5-7), polyacetylenes (2), polystyrenes (2) and silicone polymers (12) show that gas transport rates within a particular polymer class can vary dramatically depending upon the structure of the monomer present. These observations on materials where the monomer changes while the functional "link" remains constant suggest that structural factors other than the polymer class are significant in determing gas transport properties. 

Typically, chemically modified surface layers involve thicknesses ranging from less than 1 micrometer(H) up to 20H-, so the overall mechanical properties of the treated objects are hardly affected by the process. Even if one limits the discussion to materials containing C-H bonds, practically all engineering plastics are covered except pure fluorocarbons and some silicones. Clearly, various gases can react with the carbon-hydrogen bonds on the surface of a plastic article and can reduce the diffusion coefficient of penetrants in the material. The choice of sulfonation as the preferred treatment, therefore, is not based solely on the ability to modify transport properties. 

In hydrogenated amorphous silicon (a-Si H) mobility measurements are much more difficult to perform and to interpret for two reasons (1) the material has a disordered structure, and (2) undoped a-Si H is a photoconducting insulator whose transport properties have much in common with those of dielectrics. In many instances, even doped a-Si H may be very resistive compared with conventional semiconductors. Nevertheless, the Hall mobility can still yield valuable information about the bands involved in electron and hole transport. In this chapter some of the ideas that make the... 

Aneja (2006) reported that biocomponent/composite hfs have major potential for the separation of organic and aqueous-organic mixtures via PV. They investigated the transport of isopentane through a composite of silicone rubber and PSf asymmetric hf membrane. A one-parameter mathematical model of the PV process was developed. The parameter was related to the sorption and transport properties of the penetrant through the membrane layers. They claimed that the PV parameter is a useful tool for membrane characterization and process design. 

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