Polycrystalline silicon, and

The best colour contrast of red blood cells is achieved on mono- and polycrystalline silicon, and monocrystalline surfaces of refractory metals molybdenum and tungsten, which possess maximal reflectivity. 

Polycrystalline silicon, produced from silane (SiH4) or trichlorosilane (SiHCl3) forms the upstream part of the semiconductor sector. Monocrystalline silicon is extracted from polycrystalline silicon and sliced into wafers 25 microns thick and 8 to 10 centimeters in diameter. 

Polycrystalline silicon and germanium are difficult to obtain (monocrystalline materials, especially germanium, are much more readily available but they rupture by cleavage under stress). Moreover, since they are opaque in the visible, they do not allow safe seating of the windows (see below). 

Theoretical conversion efficiencies of photovoltaic systems depend on the semiconductor materials used in the cells and on the ambient tanperatuie. The materials currently used to make photovoltaic cells can be grouped into three broad categories 1) expensive, efficient monocrystalline silicon, 2) less efficient but much lower cost polycrystalline silicon, and 3) the lowest cost and poorest performer, amorphous silicon material. Conversion efficiencies of commercial polycrystaUine silicon cells are 10 to 15 percent. Now the primary development areas are in how to use monocrystalline silicon with solar concentrators and making thin-film cells by depositing a 5- to 20-micron film of silicon onto an inexpensive substrate, because the estimated efficiency of these cells is above 20 percent. Work is ongoing with other materials, including amorphous silicon (a-Si), copper indium diselenide (CuInSe2 or CIS) and related materials, and cadmium telluride (CdTe). 

PECVD has been used industrially for several decades to deposit oxides and nitrides of silicon, polycrystalline silicon, and epitaxial silicon (Tedrow and Reif, 1994) for microelectronics. There are also many applications in the automotive. 

Polycrystalline silicon. Although the contacts between polycrystalline silicon and the filament are inherently perfect, the high resistance in combination with the high positive TCR of the poly-Si limits the operation temperature of the structure. Increasing the input power (and temperature) the resistance of the polysilicon wires on the suspension beams may dominate, resulting in malfunction of the device. 

Dichlorosilane is primarily used in the electronics industry for such applications as growth of epitaxial or polycrystalline silicon and chemical vapor deposition of silicon dioxide and silicon nitride. 

For high electric and thermal conductivity, metals such as gold (Au), copper (Cu), and aluminum (Al) are used widely. Magnetic metals such as nickel (Ni) and iron (Fe) are utilized to form magnetic actuators. Some metal thin films such as chromium (Cr) and titanium (Ti) are applied to enhance the adhesion of other metal thin films to a substrate. Doped polycrystalline silicon and metal silicides [12] have electric conductivities slightly inferior to metals but much better than insulators. They have also become integral materials for microelectronics. 

The problems of rms addressing of liquid crystal devices can be circumvented by incorporating a semiconductor switch at each pixel of the display. The most usual architecture uses a field effect transistor as the switch [69], while other active components such as diode networks [70] and MIM (metal-insulator-metal) switches [71] have also been used (Fig. 18). The semiconductor material is usually amorphous silicon, which can be deposited and processed at temperatures compatible with a glass substrate. Polycrystalline silicon and other semiconductors, especially cadmium selenide, are also used in special applications such as those requiring very small pixel geometries and, by virtue of their higher carrier mobility, offer the... 

Figure 10 Time-of-flight spectra for (A) vanadium, (B) polycrystalline silicon and (C) vitreous germania. Also shown are the normalized spectra for (D) polycrystalline silicon and (E) vitreous germania.

Interplanar Spacings. Diffractometer alignment procedures require the use of a well-prepared polycrystalline specimen. Two standard samples found to be suitable are silicon and a-quartz (including Novaculite). The 26 values of several of the most intense reflections for these materials are listed in Table 7.6 (Tables of Interplanar Spacings d vs. Diffraction Angle 26 for Selected Targets, Picker Nuclear, White Plains, N.Y., 1966). To convert to d for Ka or to d for Ka2, multiply the tabulated d value (Table 7.6) for Ka by the factor given below ... 

Polysilicon is a contraction of polycrystalline silicon, (in contrast with the single-crystal epitaxial silicon). Like epitaxial silicon, polysilicon is also used extensively in the fabrication of IC s and is deposited by CVD.f l it is doped in the same manner as epitaxial silicon. Some applications of poly silicon films are ... 

Venkatesan, M., and Beinglass, I., Single-Wafer Deposition of Polycrystalline Silicon, Solid State Technology, pp. 49-53 (March 1993)... 

FIGURE 4.4 The production of polycrystalline silicon for the eleetronics industry involves several ehemieal steps aimed at the reduetion of impurities. These inelude (1) reaction of metallurgical grade silicon to produce a mixture of chlorosilanes, (2) distillation of trichlorosilane, and (3) reduction of trichlorosilane to polycrystalline silicon. Excerpted by special permission from Chemical Engineering, June 10, 1985. Copyright 1985 by McGraw-Hill, Inc., New York, NY 10020. 

Most important, reliable and no-regrettable measures are two move to renewable energies and energy saving/conservation. The concept of renewable energy is shown in Fig. 2. The trials of developments of new route to solar energies, for example production of polycrystalline silicon is important [9, 10]. The conversion of waste oil to fiiel has also been investigated [11]. The study on coal conversion is also developed to the biomass conversion study. 

Seager, C.H., and Ginley, D.S., (1982). Fundamental Studies of Grain Boundary Passivation in Polycrystalline Silicon with Application to Improved Photovoltaic Devices, Sandia Report, SAND82-1701, p. 19-21. 

K.F. Lee, T.J. Stultz, and James F. Gibbons, Beam Recrystallized Polycrystalline Silicon Properties, Applications, and Techniques... 

Schropp, R. E. I. Carius, R. Beaucarne, G. 2007. Amorphous silicon, microcrystalline and thin-film polycrystalline silicon solar cells. MRS Bull. 32 219-223. 

Kuo, Y. (Editor). 2004. Thin-Film Transistors Materials and Processes, Amorphous Silicon Thin-Film Transistors, Polycrystalline Silicon Thin Transistors. Kluwer, New York. 

Afentakis, T. Hatalis, M. Voutsas, A. T. Hartzell, J. 2006. Design and fabrication of high-performance polycrystalline silicon thin-film transistor circuits on flexible steel foils. IEEE Trans. Electron Dev. 53 815-822. 

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