Thermodynamic Assessment of the Si-Ta and Si-W Systems
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ection I: Basic and Applied Research
Thermodynamic Assessment of the Si-Ta and Si-W Systems Zhongnan Guo, Wenxia Yuan, Yu Sun, Zhoufei Cai, and Zhiyu Qiao
(Submitted September 8, 2009) The knowledge of phase diagram and thermodynamic properties of the Si-Ta and Si-W systems is of technical importance for metallic contacts between Ta, W, and SiC in electrical and electronic devices. The phase diagram and thermodynamic properties of the Si-Ta and Si-W systems were assessed using the CALPHAD approach with available experimental data. The intermetallic compounds of the two systems were modeled as stoichiometric ones. A set of self-consistent thermodynamic parameters were obtained and the calculated phase equilibria were found to be in reasonable agreement with most experimental data. The calculated enthalpies of formation of the silicides in the Si-Ta and Si-W systems were compared with the reported values. The enthalpies of mixing of liquid at 2000 K in similar Si-transition metal systems were used for comparison in order to judge the rationality of the calculations. The assessed thermodynamic descriptions of the Si-Ta and Si-W binary systems will serve as part of the thermodynamic database for the Si-C-M (M: Ta and W) alloys.
Keywords
phase diagram, Si-Ta, Si-W, thermodynamic assessment
1. Introduction SiC has been investigated as a wide band gap semiconductor for more than three decades. Quality contacts between SiC and metals are important for both performance and durability of electronic devices which are capable of operation at elevated temperatures. Many metals, especially transition metals are investigated to manufacture good Schottky/ohmic contacts with SiC.[1,2] The interface structures might affect the electrical properties of the contacts because a certain degree of solid state reaction between metals and SiC gives rise to the product layer formation at the interface. Usually, silicides play a positive role to decrease the contact resistivity due to their considerable
This article is an invited paper selected from participants of the 14th National Conference and Multilateral Symposium on Phase Diagrams and Materials Design in honor of Prof. Zhanpeng Jin’s 70th birthday, held November 3-5, 2008, in Changsha, China. The conference was organized by the Phase Diagrams Committee of the Chinese Physical Society with Drs. Huashan Liu and Libin Liu as the key organizers. Publication in Journal of Phase Equilibria and Diffusion was organized by J.-C. Zhao, The Ohio State University; Yong Du, Central South University; and Qing Chen, Thermo-Calc Software AB. Zhongnan Guo, Wenxia Yuan, Yu Sun, and Zhoufei Cai, Department of Chemistry, School of Applied Science, University of Science and Technology Beijing, Beijing 100083, P.R. China; Zhiyu Qiao, Department of Physical Chemistry, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China. Contact e-mail: wxyuan@sas. ustb.edu.cn.
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thermal stability, oxidation resistance, high thermal and electrica
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