Silicon carbide single crystal

Resistivity measurements of doped, alpha-silicon carbide single crystals from —195 to 725°C showed a negative coefficient of resistivity below room temperature, which gradually changed to positive above room temperature (45). The temperature at which the changeover occurred increased as the ionization of the donor impurity increased. This is believed to be caused by a change in conduction mechanism. 

M. Kikuchi, Y. Takahashi, T. Suga, S. Suzuki, Y. Bando, Mechanochemical polishing of silicon carbide single crystal with chromium (iii) oxide abrasive, J. Am. Ceram. Soc. 75 (1992) 189-194. 

Oyanagi, N. (2003) Method for growth of silicon carbide single crystal, silicon carbide seed crystal, and silicon carbide single crystal (sic ). W0/2004(111318). 

Note The principal reinforcement, with respect to quantity, is glass fibers, but many other types are used (cotton, rayon, polyester/TP, nylon, aluminum, etc.). Of very limited use because of their cost and processing difficulty are whishers (single crystals of alumina, silicon carbide, copper, or others), which have superior mechanical properties. 

Silicon carbide occurs in two slightly different crystal structures a single cubic form, (3SiC, and a large number of hexagonal... 

Single-crystal silicon carbide, 22 525 manufacture and processing of, 22 532 Single-crystal silicon substrates, 23 39-40 Single-crystal structure determination information from, 26 426 macromolecule, 26 425-426 small-molecule, 26 423—425 Single-electron transistors (SETs), 22 169, 171-172... 

The properties of silicon carbide (4—6) depend on purity, polytype, and method of formation. The measurements made on commercial, polycrystalline products should not be interpreted as being representative of single-crystal silicon carbide. The pressureless-sintered silicon carbides, being essentially single-phase, fine-grained, and polycrystalline, have properties distinct from both single crystals and direct-bonded silicon carbide refractories. Table 1 lists the properties of the fully compacted, high purity material. 

A progressive etching technique (39,40), combined with x-ray diffraction analysis, revealed the presence of a number of a polytypes within a single crystal of silicon carbide. Work using lattice imaging techniques via transmission electron microscopy has shown that a-silicon carbide formed by transformation from the p-phase (cubic) can consist of a number of the a polytypes in a syntactic array (41). 

Silicon carbide has been described as a mild inhalation irritant (143). The threshold limit value for silicon carbide in the atmosphere is 5 mg/m3. Because of increased interest in SiC whiskers as a reinforcement for composites, the ASTM has established Subcommittee E34.70 on Single-Crystal Ceramic Whiskers to write standards for handling this form of SiC (144). 

Fig. 2. Researcher Dan Barrett (Westinghouse Science Technology Center) checks the hot (2400°C) crystal growfli furnace that he designed for physical vapor transport growth of single crystals of silicon carbide...

Bulk silicon carbide has the zincblende crystal structure and has been studied, not in single crystal form, but as a micron depth thin film created by chemical vapor deposition on a Si(100) substrate (Powers et al., 1992). I vo C-terminated c(2x2) structures have been studied by LEED, one with, and one without exposure, to C2II4 following cleaning. In both cases, the surface is terminated with coplanar C-C dimers which bridge the second layer Si sites. The Si rich surface terminates with an asymmetric Si dimer (Powers ct al., 1992). 

P.B. Pickar et al [Engineering Sciences Lab., Dover, NJ, Research on Optical Properties of Single Crystal of Beta Phase Silicon Carbide. Summitry Tech. Rept. no. OR8394, May 5, 1965-June 5, 1966. Contract no. DA-28-017-AMC-2002, A, Oct. (1966) 85p. AD-641 198 ]... 

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. 

Sublimation is one of the main methods of growing silicon carbide. This method is employed for growth of the material for abrasive applications as well as for the growth of single crystals and epitaxial layers for use in semiconductor electronics. The idea of the method is fairly simple, and is based on material transport from a hot source of material to a substrate which rests at a somewhat lower temperature. The transport is performed by the intrinsic vapour of the material at a high temperature, usually in the range 1600-2700 °C. 

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