2015年 第76回応用物理学会秋季学術講演会

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一般セッション(口頭講演)

6 薄膜・表面 » 6.2 カーボン系薄膜

[15a-4F-1~9] 6.2 カーボン系薄膜

2015年9月15日(火) 09:00 〜 11:45 4F (438)

座長:大越 康晴(電機大),波多野 睦子(東工大)

11:00 〜 11:15

[15a-4F-8] [Young Scientist Presentation Award Speech] Nano-scale interlayer formation for thermally stable SBD electrical properties

〇Alexandre FIORI1, Tokuyuki TERAJI1, Jose PINERO2, Daniel ARAUJO2, Yasuo KOIDE1 (1.NIMS, 2.University of Cadiz)

キーワード:diamond,Schottky diode,interface

High temperatures diamond Schottky barrier diodes (SBD) have been developed these last years. In particular, problems of reproducibility and unstable Schottky barrier have been aroused. Zr/diamond SBDs showed rectification gain above 600 K [1]. A native oxide has been found at the Zr/diamond interface by transmission electron microscopy (TEM) [2]. This oxide provided the rectification at elevated temperature, but no ideal Schottky behaviors. In our group, tungsten carbide (WC)/diamond SBDs showed ideal Schottky behavior up to 600 K, after annealing [3]. In addition, stabilization and degradation domains have been identified [4]. Based on TEM, we proposed a model of the WC/diamond interface to explain these thermal modifications. The identification of mechanism undergoing will be helpful to select the ultimate Schottky metal combination.
WC has been deposited by conventional Ar plasma sputtering on lightly boron-doped epilayers whose surfaces were terminated by oxygen. SBDs have been cut in cross section in order to be analysed by TEM. The chemical composition of WC/diamond interface has been obtained by electron energy loss spectrometry (EELS).
The ratio of oxygen peak intensity over carbon pointed out an interfacial oxygen enrichment following the 600 K annealing. At higher temperature, this oxygen signal weakened, indicating an oxygen deficiency. The evolution of oxygen can be interpreted as reactions with tungsten and carbon to form different interlayers. We suggested the WC/diamond interface had a mixed composition over few monolayers before annealing. Oxygen termination might be dissociated by WC bombardment. Then, oxygen could diffuse in the interlayer toward the diamond interface by vacuum annealing at 600 K. The gain in Schottky ideality can be seen as the formation of a homogenous monolayer in contact with diamond. The effect of annealing at 900 K on oxygen is less evident. Catalytic effects of WC are suspected.

References
[1] A. Traore, P. Muret, A. Fiori, et al., Appl. Phys. Lett. 104, 052105 (2014).
[2] J. C. Pinero, D. Araujo, A. Traore, et al., Phys. Status Solidi A 211, 2367 (2014).
[3] A. Fiori, T. Teraji, Y. Koide, Appl. Phys. Lett. 105, 133515 (2014).
[4] A. Fiori, T. Teraji, Y. Koide, Phys. Status Solidi A 211, 2363 (2014).