Фазовая диаграмма системы C-Si

К оглавлению: Другие диаграммы (Others phase diargams)


C-Si (Carbon-Silicon) R.W. Olesinski and G.J. Abbaschian Because of difficult experimental requirements, only a few comprehensive investigations of the Si-C phase diagram have been undertaken, and the results are somewhat conflicting. The present diagram is based primarily on the experimental work of [60Dol], with a review of the work of [59Sca], [67Str], [ 70Noz], and [73Vol]. The assessed Si-C phase diagram is characterized by a peritectic reaction at 2545 с 40 C, involving Si-C and a liquid of 27 at.% C, and a eutectic reaction at 1404 с 5 C and 0.75 с 0.5 at.% C [60Dol]. In the assessed phase diagram, the high-temperature melting points of [67Str] have been used. The present evaluators conducted thermodynamic calculations to determine the stability of various phases of the Si-C system. They determined that (1) the cubic form of silicon carbide (bSiC) is more stable than the hexagonal form ( aSiC) at any temperature below the peritectic point; (2) the solid bSiC can decompose under atmospheric pressure to C and liquid Si at 3076 C if nonmixing of C and Si phases is assumed, i.e., zero entropy of mixing (the transformation of the silicon carbide to a mixture of Si and C can occur at a lower temperature because of a positive entropy of mixing); and (3) the atmospheric boiling point of Si is 3227 C, and the atmospheric sublimation point of C is 3798 C. The solid solubility for C in (Si) at 1200 to 1400 C is ~10<310>3 to 10<310>4 at.% C, and C dissolves substitutionally in (Si). At the eutectic temperature, the solubility is approximately 0.0007 [70Noz] or 0.00018 [73Vol] at.% C. Extended solid solubility of C in Si has been reported in films prepared on quartz substrates by the pyrolysis of heptane vapor at 1252 C. The electron- diffraction determination of the lattice parameter of the Si phase was interpreted as evidence of the formation of a solid solution, containing as much as 10 at.% C; the SiC phase was also observed in the diffraction patterns. In Si-C films synthesized by a plasma deposition process on Si and quartz substrates, the substrate temperature ranged from 200 to 600 C, and the reaction gases consisted of CH4 and SiH4. The formation of amorphous SiC films with a composition of 39 at.% Si and 61 at.% C was obtained by RF sputtering. Silicon carbide is well known for its numerous polytypes, which are mostly modifications of the aSiC (hexagonal) structure. 59Sca: R.I. Scace and G.A. Slack, J. Chem. Phys., 30, 1551-1555 (1959). 60Dol: R.T. Dolloff, WADD Tech. Rep. 60-143, Wright Air Development Division ( 1960). 67Str: H.M. Strong and R.E. Hanneman, J. Chem. Phys., 46, 3668-3676 (1967). 70Noz: T. Nozaki, Y. Yatsurugi, and N. Akiyama, J. Electrochem. Soc., 117, 1566-1568 (1970). 73Vol: F.W. Voltmer and F.A. Padovani, Semicond. Silicon, Pop. Int. Symp. Silicon Mater. Sci. Technol., 2nd; 75-82 (1973). Published in Bull. Alloy Phase Diagrams, 5(5), Oct 1984. Complete evaluation contains 1 figure, 2 tables, and 28 references. 1