Other Silicides

Several other silicides of potential interest are the obj ect of active CVD development. 

The in-V compounds combine the elements of Group HI (aluminum, gallium, indium) with those of Group V (phosphorus, arsenic, antimony, bismuth). As can be imagined, a wide variety of compounds can be produced which, in addition to the binary materials, also include ternary and even quaternary materials. 

These materials are useful semiconductors and have a wide range of industrial applications, particularly in opto-electronics. One of their attractive features is the possibility of tailoring the band gap and the lattice constant in the ternary alloys by varying the composition. CVD is now a major production process of these materials. 

Crystalline form cubic close pack (zinc blende) Lattice parameters a = 0.56531 O.nm 

Bandgap at 300K (eV) 1.43 Saturated Drift Velocity (em/sec) 2.0x10 Drift Mobility 

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A similar discussion of transition-metal bond lengths has been reported for FeSi and other silicides with the 531 structure (Pauling Soldate, 1948), and Co2Al9 (Pauling, 1951). 

Deposition temperature from the fluoride is 250-300°C at a pressure of < 2 Torr. Deposition temperature from the chloride is 650-950°C at low pressure. In Reactions (1) and (2)—and in other silicide deposition reactions as well— the silane gas is usually highly diluted with an inert gas such as argon. 

Tungsten disilicide (WSi2) is refractory and stable with low resistivity. As with other silicides, a common deposition system uses silane as the silicon source with tungsten hexafluoride as follows ... 

Borides, Silicides, III-VandII—VI Compounds 333 2.11 Other Silicides... 

Therefore, we tried silicon carbide as the anode, which turned out to be completely stable against oxidation. Iron silicide and other silicides also seem to be stable. In our case, the reaction at the anode is the chlorination of the solvent. So, for instance, chlorinated products of THF can be detected by... 

BritP 17583 (1915) describes a family of expls prepd by mixing together 74—80p by wt of Amm chlorate, 6—18p of Si, ferro-Si, A1 silicide or other silicide, 2—6p of wood-meal, and 4—1 Op of nitrated or unnitrated fraction of rock oil, boiling above 250° 10—12p of a gelatine of NC with liq trinitrotoluene may be added Ref Colver (1938), 741... 

Si3N4/other silicides Less important due to less stability against oxidation or low melting point Under sintering conditions liquid silicides can concentrate in big defects, Fe silicide can improve the wear behaviour in engine applications [564]... 

Two other silicides have been described,2 namely, CoSi3 (m.pt. 1307° C.) and CojSig (formed slowly at 1180-1215° C. in the solid state from CoSi and Co2Si). 

The freezing-point curve of nickel and silicon indicates the existence of several other silicides, namely, NisSi, Xi3Si2, NiSi, and Xi2Sis.4 A tefranickel silicide, NijSi, has been isolated.6 Density curves,6 however, apparently indicate the existence of three silicides only, namely, Ni2Si, NiSi, and Ni3Si2. 

Q. Li et al. 1991), which corresponds to the magnetic moment of the iron sublattice. This value is higher than for any other silicide, suggesting antiferromagnetic coupling between the Fe and R (heavy) sublattices. The magnetic moment for the rare-earth sublattice equals 6.4, 8.0, 8.6, 8.3 and atom for Gd, Tb, Dy, Ho, and Er, respectively. These v ues... 

Unlike the oxides of many other silicide-based elements (e.g. Mo), the oxides of Ti are quite stable (Lee, 1992) (Fig. 6-3). Thermodynamic calculations for the Ti-Si-O system predict that a Si concentration of at least 35-45 at.% is required to make Si02 the stable oxide on binary Ti-Si alloys (Jiang etal., 1986 Luthra, 1991 Rahmel et al., 1991). Even for the Si-rich TiSi2, however, the formation of protective Si02 can be problematical (Becker et al., 1992a Lee, 1992 Melsheimer et al., 1997 a). 

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