Carbide electrical properties

Electrical Properties. The electrical properties of siUcon carbide are highly sensitive to purity, density, and even to the electrical and thermal history of the sample. 

Mechanical and electrical properties of multilayer composites of silicon carbide... 

A.O. Konstantinov, C.I. Harris and E. Janzen, Electrical properties and formation mechanism of porous silicon carbide, Appl. Phys. Lett., 65, 2699-2701 (1994). 

Thermal oxidation of the two most common forms of single-crystal silicon carbide with potential for semiconductor electronics applications is discussed 3C-SiC formed by heteroepitaxial growth by chemical vapour deposition on silicon, and 6H-SiC wafers grown in bulk by vacuum sublimation or the Lely method. SiC is also an important ceramic ana abrasive that exists in many different forms. Its oxidation has been studied under a wide variety of conditions. Thermal oxidation of SiC for semiconductor electronic applications is discussed in the following section. Insulating layers on SiC, other than thermal oxide, are discussed in Section C, and the electrical properties of the thermal oxide and metal-oxide-semiconductor capacitors formed on SiC are discussed in Section D. 

Various electrical and optical properties that have been measured for the wet thermal oxide on silicon carbide are summarised in TABLE 3. In general, no systematic variation of any of the oxide properties has been reported with oxide growth temperature in the range of 1000 to 1250°C. However, oxide grown with a wet process has been shown to have lower oxide charges than oxide grown in dry oxygen. Variations in the measured electrical properties... 

It is highly probable that the metal contamination strongly affects the electrical properties of silicon carbide crystals and reduces the carrier lifetimes, as in other semiconductors. Unfortunately, no detailed studies of this effect have been reported thus far. 

The extraordinary mechanical, thermal and electrical properties of carbon nanotubes (CNT) have prompted intense research into a wide range of applications in structural materials, electronics, and chemical processing.Attempts have been made to develop advanced engineering materials with improved or novel properties through the incorporation of carbon nanotubes in selected matrices (polymers, metals and ceramics). But the use of carbon nanotubes to reinforce ceramic composites has not been very successful. So far, only modest improvements of properties were reported in CNTs reinforced silicon carbide and silicon nitride matrix composites, while a noticeable increase of the fracture toughness and of electrical conductivity has been achieved in CNTs reinforced alumina matrix composites. ... 

The pyrolysis of polysilanes and polycarbosilanes is usually carried out using inert gas (e.g., argon) as pyrolysis atmosphere. A general problem associated with the pyrolytic formation of carbides is the desired stoichiometry of the calcined products in contrast to nitrides, excess carbon carmot be evaporated during calcining it may therefore contaminate the powders obtained as an elemental impurity and thus influences the physical, especially mechanical and electrical, properties of the sintered ceramic bodies. The volatiles evaporated during pyrolytic treatment of carbosilanes to form a network structure are H2 and CH4, and they depend on the structure of the polycarbosilane used (Fig. 2). 

The dimensions of the added nanoelements also contribute to the characteristic properties of PNCs. Thus, when the dimensions of the particles approach the fundamental length scale of a physical property, they exhibit unique mechanical, optical and electrical properties, not observed for the macroscopic counterpart. Bulk materials comprising dispersions of these nanoelements thus display properties related to solid-state physics of the nanoscale. A list of potential nanoparticulate components includes metal, layered graphite, layered chalcogenides, metal oxide, nitride, carbide, carbon nanotubes and nanofibers. The performance of PNCs thus depends on three major attributes nanoscopically confined matrix polymer, nanosize inorganic constituents, and nanoscale arrangement of these constituents. The current research is focused on developing tools that would enable optimum combination of these unique characteristics for best performance of PNCs. 

A mixture of metallic, covalent and ionic components prevails in the bonding of transition metal carbides, nitrides, and carbonitrides. The metallic character is shown by the high electrical conductivities of these compounds. The bonding mechanism has been described extensively by a variety of approaches for calculating the density of states (DOS) and hence the electron density in f.c.c. transition metal carbides, nitrides, and oxides [11]. In the DOS of these compounds there is a minimum at a valence electron concentration (VEC) of 8, which corresponds to the stoichiometric composition of the group ivb carbides TiC, ZrC, and HfC. Transition metal carbides have a lower DOS at the Fermi level than the corresponding transition metal nitrides, hence the electrical properties such as electrical and thermal conductivity and the superconducting transition temperature, T, are lower than those of the nitrides. 

Electrical properties of MeC H films, deposited by reactive sputtering from metal or metal carbide targets in hydrocarbon atmosphere, have been described elsewhere [32]. In case of Ta as a typical refractory, carbide-forming metal, the electrical behavior can be divided into three categories, depending on the metal content ... 

Owing to the fact that valence electrons determine bonds, the electrical properties of a material are related to the bond type. In conductors such as metals, alloys, and intermetallics, the atoms are bound to each other primarily by metallic bonds, and metals such as tungsten or aluminum are good conductors of electrons or heat. Covalent bonds occur in insulators such as diamond and silicon carbide and in semiconductors such as silicon or gallium arsenide. Complexes and salts have ions that are bound with electrostatic forces. Ionic conductors can be used as solid electrolytes for fuel cells because solids with ionic bonds may have mobile ions. Most polymers have covalent bonds in their chains but the mechanical... 

In the case of the nitrides and carbides the structures have some effect on the electric properties. For compounds that have an NaCl structure, the mononitrides and carbides are better metallic conductors than the metals themselves. Those that have zinc blende or Wiirtzite structures (SiC, AIN, InN) or other (SigNJ are useful semiconductors or insulators. Tungsten carbide when sintered with cobalt shows some catalytic activity in fuel cells. This hybrid composite is so hard and tough that it is widely used in drill bits for concrete drilling. 

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