科研之友
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摘要
The initial stage of oxidation of an Si (110)-(1 ℅ 1) surface was analyzed by using the first-principles calculation. Two calculation cells with different surface areas were prepared. In these cells, O atoms were located at the Si每Si bonds in the first layer (A-bonds) and at the Si每Si bonds between the first and second layers (B-bonds). We found that (i) the most stable site of one O atom was the A-bond, and (ii) an O (A-bond) 每Si每O (A-bond) was the most stable for two O atoms with a coverage ratio of while an O (A-bond) 每Si每O (B-bond) was the most stable for . The stability of O (A-bond) 每Si每Si每O (A-bond) was less than the structures obtained in (ii). The other calculations showed that the unoxidized A-bonds should be left when a coverage ratio of is close to 1. These simulations suggest that the O atoms will form clusters in the initial stage of oxidation, and the preferential oxidation will change from the A-bonds to the B-bonds up to the formation of 1 monolayer (ML) oxide. The results obtained here support the reported experimental results. 1. Introduction The performance of electronic devices has been markedly improved with the development of microfabrication technology, which allows for the use of thin nanoscale Si films. However, as the improvements in scaling technology will reach their uppermost limit in the near future, alternative technology is required. There is a great deal of engineering interest in Si (110) wafers used as the substrates of large-scale integrations (LSI) for next generation technology because the hole mobility of (110) is higher than that of a (100) surface; about 2.5 times as high as that of (100) [1]. Despite this importance, few studies on Si (110) surface have been reported in comparison with other low-index surfaces. It was previously reported that the most stable configuration of a Si (110) clean surface was a (16 ℅ 2) reconstruction at temperatures of less than about 700～C [2]. The detailed structure and initial oxidation of a Si (110)-(16 ℅ 2) clean surface were experimentally [3每5] and theoretically [6, 7] studied by different research groups including us [7]. On the other hand, at temperatures higher than about 700～C, the Si (110)-(1 ℅ 1) surface was the most stable [2]. Suemitsu et al. [8] experimentally studied the oxidation process up to 1 monolayer (ML) of the Si (110)-(1 ℅ 1) surface and suggested the preferential oxidation of B-bonds (Si每Si bonds between the first and second layers). However, to the best of our knowledge, there have been few theoretical studies on the initial stage of oxidation on Si
