金刚石/硅(001)异质界面的分子动力学模拟研究

采用分子动力学方法模拟研究了未重构的金刚石/硅(001)面相接触时界面层原子的弛豫过程及所形成的异质界面的结构特征.硅碳二元系统中原子间的相互作用采用Tersoff多体经验势描述.弛豫前沿[110]与[110]方向界面碳硅原子数之比均为3∶2.界面碳硅原子总数之比为9∶4.弛豫后金刚石与硅界面处晶格匹配方式改变为[110]方向基本上以3∶2关系对准,而[110]方向大致以1∶1关系对准.相应地,界面碳硅原子总数之比接近3∶2.界面下方部分第二层硅原子在弛豫过程中向上迁移至界面是引起这种变化的原因,同时该层其他原子及其底下一到两个原子层厚度的区域在[001]方向上出现一定程度的无序化转变倾向.金刚石/硅异质界面处的硅碳原子发生强烈键合,形成平均键长为0.189nm的硅碳键.研究证实,晶格匹配主要呈现界面及其附近硅原子迎合界面碳原子排列的特点.关键词：金刚石硅异质界面分子动力学

A MOLECULAR DYNAMICS SIMULATION OF DIAMOND/SILICON(001) INTERFACE

The structure of diamond/silicon interface, which was formed by the contact and the subsequent relaxation of the unreconstructed (001) surfaces of diamond film and silicon substrate, has been investigated by molecular dynamics simulation. The interaction among atoms of the silicon/carbon binary system was described by Tersoff many-body empirical potential. Before relaxation, the ratios of silicon atoms to carbon atoms along ［110］ and ［110］ directions are both 3∶2 and the ratio of the total number of interfacial silicon atoms to that of carbon is 9∶4. After relaxation, the matching of diamond and silicon lattices has been changed: along［110］ direction, a 3∶2 coincidence relation is roughly remained, but along ［110］ direction, a 1∶1 coincidence relation is approximately adopted. Accordingly, the ratio of the total number of interfacial silicon atoms to that of carbon is near 3∶2. The migration of partial silicon atoms, which were originally in the second layer, upward to the interface is responsible for such changes. The silicon lattice near the interface shows the tendency of disordering along ［001］ direction. The strong bonding between interfacial silicon and carbon atoms was found and Si-C bonds with an average length of 0.189 nm were formed. This study has confirmed that the main feature of lattice matching is the meeting of silicon atoms at and near the interface to the arrangement of interfacial carbon atoms.