Purities silicone

Silicon reacts at elevated temperatures with the halogens, forming SiCl, Sil, SiBr, and SiF. There is also a series of halogen-substituted silanes such as trichlorosilane, SiH Cl, and dichlorosilane, S1H2CI2. Both SiCl and SiH Cl are relatively easy to make, purify, and reduce to silicon. These are the silicon compounds most often used as feedstocks in the manufacture of high purity silicon. 

The commercial production of silicon in the form of binary and ternary alloys began early in the twentieth century with the development of electric-arc and blast furnaces and the subsequent rise in iron (qv) and steel (qv) production (1). The most important and most widely used method for making silicon and silicon alloys is by the reduction of oxides or silicates using carbon (qv) in an electric arc furnace. Primary uses of silicon having a purity of greater than 98% ate in the chemical, aluminum, and electronics markets (for higher purity silicon, see Silicon AND SILICON ALLOYS, PURE SILICON). 

Figure 6 Typical secondary ion mass spectrum obtained from high-purity silicon using an oxygen ion beam. Major ion peaks are identified in the spectrum.

P, Pohl, H.-J., Schenkel, T., I hewall, M.L.W., Itoh, K.M. and Lyon, S.A. (2012) Electron spin coherence exceeding seconds in high-purity silicon. Nat. Mater., 11, 143-147. 

Czochralski seeded single-crystal growth from semiconductors stable as melts, which yields the meters-large single crystals of ultra-high purity silicon used in nearly all technological applications. 

In high purity silicon below T = 140 K the Mu center is stable on the time scale of the muon lifetime (2.2 ps). However, in electron irradiated silicon Westhauser et al. (1986) have reported that Mu is metastable and makes a thermally induced transition to Mu at a temperature of 15 K. A similar transition between Mu and Mu was first discovered in diamond (Holz-schuh et al., 1982, Odermatt et al., 1988) and will be discussed in Sec-... 

The treatment assumes that the point defects do not interact with each other. This is not a very good assumption because point defect interactions are important, and it is possible to take such interactions into account in more general formulas. For example, high-purity silicon carbide, SiC, appears to have important populations of carbon and silicon vacancies, and Vsj, which are equivalent to Schottky defects, together with a large population of divacancy pairs. 

The chemical properties of silicon are not particularly sensitive to small amounts of impurities and have mostly been determined using low purity material. However, many of the mechanical, electrical, and optical properties are substantially altered by the level of impurities. These have been reexamined in detail since high purity silicon first became available in the late 1940s. 

The 1995 world production of high purity silicon was estimated at about 13,000 metric tons. The average selling price was about 48.00 /kg. Principal suppliers are listed in Table 7. This quantity of silicon supported a silicon device market, ie, primarily diodes, transistors, and integrated circuits, of about... 

The silicon required by the electronics industry for semiconductor devices has to have levels of key impurities, such as phosphorus and boron, of less than 1 atom in 10 ° Si. Silicon is first converted to the highly volatile trichlorosilane, SiHCls, which is then distilled and decomposed on rods of high purity silicon at 1300 K to give high purity... 

Fig. 3.14 A ToF spectrum of a high purity silicon whisker in hydrogen image gas, obtained with a pulsed-laser imaging atom-probe. Below 80 K, silicon is an excellent insulator. However, the tip surface can be easily field evaporated with the stimulation of laser pulses.

One of the most serious shortcomings of the HV pulse atom-probe is the inability to pulse field evaporate materials of very low electrical conductivity such as a high purity silicon. This is due to the difficulty of transmitting ns HV pulses across the tip. This limitation is overcome by the use of laser pulses which can be focused right to the tip apex. Thus the material applicability of the atom-probe is greatly expanded by the use of laser pulses for the pulsed-field evaporation. 

Crude elemental silicon can be obtained by reduction of silica sand with coke in the electric furnace (reaction 17.33) and may be adequate for making ferrosilicon alloys (Section 16.7.5) or silicones (Section 3.5). The high purity silicon used for electronic chips can be made from silica via silicon tetrachloride, which, like TiCU, is a volatile liquid (bp 57 °C) susceptible to hydrolysis but readily purifiable by fractional distillation. Indeed, the procedure for silicon resembles the Kroll process for titanium, except that an argon atmosphere is not necessary ... 

An efficient analytical procedure for the trace impurity analysis of Mg, K, Cr, Mn, Fe, Ni, Co, Cu, Zn, Ag, Cd, Ba and Pb in high purity silicon powder after a very simple matrix separation via microwave assisted volatihzation of silicon as silicon fluorides, was proposed by Ueng el al.59 The authors observed a nearly 99 % volatihzation of the matrix element silicon from the... 

Silicon tetrabromide [7789-66-4], SiBr4, and tribromosilane [7789-57-3], SiHBr3, are used in a process to make high purity silicon (40). Stannous bromide [10031-24-0], SnBi, is claimed as a catalyst in preparing a lubricant antioxidant (41). Stannic bromide [7789-67-5], SnBr is used in the metallurgical separation of minerals (42). 

Gu, H., (2002), Variation of width and composition of grain-boundary fdm in a high-purity silicon nitride with minimal silica , J. Am. Ceram. Soc., 85 (1), 33-37. 

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