Silicon phase diagram

Fig. 8.3 The lithium—silicon phase diagram. (By permission of the Journal of the Electrochemical Society R.A. Sharma and R.N. Seefurth, 1976, 123, 1763.)...

A cross-section of a modified surface is shown in Fig. 13.4. The schematic of the modifying process is shown in Fig. 13.5 and Figs 13.6 and 13.7 show the iron carbon diagram for austenitic T91 at 1050°C and 0.1%C, and the iron-silicon phase diagram with phase transformation from austenitic to ferrite steel lattice with growing Si content, respectively. 

FIGURE 8.10 The gold-silicon phase diagram (Courtesy of ASM International). 

Figure Al.3.23. Phase diagram of silicon in various polymorphs from an ab initio pseudopotential calculation [34], The volume is nonnalized to the experimental volume. The binding energy is the total electronic energy of the valence electrons. The slope of the dashed curve gives the pressure to transfomi silicon in the diamond structure to the p-Sn structure. Otlier polymorphs listed include face-centred cubic (fee), body-centred cubic (bee), simple hexagonal (sh), simple cubic (sc) and hexagonal close-packed (licp) structures.

Silicon is soluble in aluminum in the solid state to a maximum of 1.62 wt % at 577°C (2). It is soluble in silver, gold, and 2inc at temperatures above their melting points. Phase diagrams of systems containing silicides are available (2,3). 

Polymer-Fluid Equilibria and the Glass Transition Most polymer systems fall in the Class HI or Class V phase diagrams, and the same system can often change from one class into the other as the polymer s molecular weight changes. Most polymers are insoluble in CO9 below 100°C, yet CO9 can be quite sohible in the polymer. For example, the sorption of CO9 into silicone rubber is highly dependent upon temperature and pressure, since these properties have a large influence on the density and activity of CO9. 

Now for some practical examples of how phase diagrams are used. In the first, a typical design problem, we find out how solders are chosen for different uses. In the second we look at the high-technology area of microchip fabrication and study the production, by zone refining, of ultra-pure silicon. And lastly, for some light-hearted relief, we find out how bubble-free ice is made for up-market cocktails. 

Fig. 4.5. Schematic of top left corner of the "silicon-impurity" phase diagram. To make things simple, we assume that the liquidus and solidus lines ore straight. The impurity concentration in the solid is then always less than that in the liquid by the factor k (called the distribution coefficient).

Phase diagrams for the systems silver/copper (limited solubility in the solid) and aluminum/silicon (formation of an eutectic mixture)... 

The phase diagram for aluminum/silicon (Fig. 4.5) is a typical example of a system of two components that form neither solid solutions (except for very low concentrations) nor a compound with one another, but are miscible in the liquid state. As a special feature an acute minimum is observed in the diagram, the eutectic point. It marks the melting point of the eutectic mixture, which is the mixture which has a lower melting point than either of the pure components or any other mixture. The eutectic line is the horizontal line that passes through the eutectic point. The area underneath is a region in which both components coexist as solids, i.e. in two phases. 

The crystalline core can make SiNW either fairly straight, or coiled or curly. It was discovered that CH4 may affect the helicity. This may be caused by a more complicated phase diagram that involves carbon, silicon, and metal. 

Koh J, Ferlauto AS, Rovira PI, Wronski CR, Collins RW (1999) Evolutionary phase diagram for plasma enhanced chemical vapor deposition of silicon thin films from hydrogen diluted silane. Appl Phys Lett 75 2286-2289... 

A phase diagram for the carbon—silicon system and for the relationship between temperature and solubility of carbon in silicon has been determined... 

Massalski and Prince selected this particular phase diagram because of its simplicity for illustration and because this particular phase diagram is of considerable importance in the semiconductor device industry. Silicon chips are frequently bonded to a heat sink, using a gold alloy or more frequently a Au-Si alloy foil placed between them. Upon heating above 163 C. the Au reacts with Si to form a brazed joint between the silicon chip and the heat sink. 

Rogi, P. and J.C. Schuster Phase Diagrams of Ternary Boron Nitride and Silicon Nitride Systems, ASM International, Materials Park, OH. 1992. 

The melting point of pure aluminum is 660 °C and aluminum and silicon form a eutectic, the eutectic temperature is 577 °C, the eutectic composition is 12% Si, and the maximum solubility of of silicon in solid aluminum is 1.65%. Assume the phase diagram consists of straight lines. If aluminum containing 0.15 wt% Si were solidified, what would be the composition of the first solid to form ... 

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