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Formation of transition-metal-based ohmic contacts to n-Mg2Si by Plasma Activated Sintering

Published online by Cambridge University Press:  01 February 2011

Yohei Oguni
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, 1Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Tsutomu Iida
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Atsunobu Matsumoto
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda -shi, Chiba, 278-8510, Japan
Takashi Nemoto
Affiliation:
sunflat84@yahoo.co.jp, Nippon Thermostat Co., Ltd., 6-59-2 Nakazato, Kiyose-shi, Tokyo, 204-0003, Japan
Junichi Onosaka
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Hironori Takaniwa
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda -shi, Chiba, 278-8510, Japan
Tatsuya Sakamoto
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Daisuke Mori
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda -shi, Chiba, 278-8510, Japan
Masayasu Akasaka
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
Junichi Sato
Affiliation:
sunflat84@yahoo.co.jp, Nippon Thermostat Co., Ltd., 6-59-2 Nakazato, Kiyose-shi, Tokyo, 204-0003, Japan
Tadao Nakajima
Affiliation:
sunflat84@yahoo.co.jp, Nippon Thermostat Co., Ltd., 6-59-2 Nakazato, Kiyose-shi, Tokyo, 204-0003, Japan
Keishi Nishio
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda -shi, Chiba, 278-8510, Japan
Yoshifumi Takanashi
Affiliation:
sunflat84@yahoo.co.jp, Tokyo University of Science, Department of Materials Science and Technology, 2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
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Abstract

Electrode materials consisting of Cu, Ti and Ni were formed on Bi-doped n-type Mg2Si by means of a monobloc plasma-activated sintering (PAS) technique. Due to the difference in thermal expansion coefficients between Ti and Mg2Si, rather high residual thermal stresses gave rise to the introduction of cracks, which were mainly located in the Mg2Si layer, when Ti was used as the electrode material. In the case of the Cu electrodes, monobloc sintering could not be performed in a reproducible manner because Cu melts abruptly and effuses at around 973K, which is 100 K lower than the sintering temperature that is required for Mg2Si of good crystalline quality. When compared with the results for Cu and Ti, the monobloc PAS process for Ni was both stable and reproducible. The room-temperature I-V characteristics of Ni electrodes were considered to be adequate for practical applications, with durable Mg2Si-electrode junction properties being realized at a practical operating temperature of 600 K with ΔT = 500 K. The highest open circuit voltage (VOC) observed was 41 mV at ΔT = 500 K (between 873 K and 373 K) for Ni electrodes fabricated using the monobloc PAS process. The voltage (V) and current (I) values with a 10 Ohm load were ∼ 48 mV and ∼ 2 mA at ΔT = 500 K.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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