In situ

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• 作者：Kazuhiro Akiyama ; Yasuhiro Ishii ; Hisashi Murakami ; Yoshinao Kumagai ; Akinori Koukitu
• 关键词：A1. Surface processes ; A1. Morphological stability ; A3. Vapor-phase epitaxy ; B1. Nitrides ; B1. Sapphire ; B2. Semiconducting aluminum compounds
• 刊名：Journal of Crystal Growth
• 出版年：2009
• 出版时间：1 May 2009
• 年：2009
• 卷：311
• 期：10
• 页码：3110-3113
• 全文大小：163 K

文摘

Surface reactions between a (0 0 0 1) C-plane sapphire and NH₃, with He as an inert carrier gas, were investigated at high temperatures over 1200 °C using the in situ gravimetric monitoring method. Although the sapphire substrate was stable up to 1400 °C under a He atmosphere, decomposition started to occur at 1300 °C under a 0.1 atm NH₃+He and the decomposition rates were found to be lower than those in 0.1 atm H₂+He at each temperature. These results imply that sapphire can be decomposed by NH₃ and/or hydrogen generated by the decomposition of NH₃ over 1300 °C. The decomposition rate in NH₃+He was decreased with increase in NH₃ flow time, and the decomposition rate became constant after 60 min of NH₃ flow. Moreover, the activation energy for sapphire decomposition before 60 min of NH₃ flow was different from that after 60 min of NH₃ flow time, which indicates that the surface reaction between sapphire and NH₃ and/or hydrogen generated from NH₃ changes depending on the time of NH₃ flow. The dependence of the surface reactions and rate-limiting reactions between sapphire and NH₃ on the time of NH₃ flow is discussed.