物理学报. 2003,
52(9): 2268-2273.
α-Al2O3(0001)基片表面结构与能量研究
- 1. (1)电子科技大学微电子与固体电子学院,成都 610054; (2)电子科技大学微电子与固体电子学院,成都 610054;四川师范大学数学与软件科学学院,成都 610068; (3)中国物理工程研究院,绵阳 621000
- 收稿日期:
2002-11-08
- 修回日期:
2002-12-30
- 刊出日期:
2003-09-20
摘要: 对α-Al2O3(0001)晶体表层三种不同终止原子结构的计算模型, 在三维周期边界条件下 的κ空间中,采用超软赝势平面波函数描述多电子体系.应用基于密度泛函理论的局域密度 近似,计算了不同表层结构的体系能量,表明最表层终止原子为单层Al的表面结构最稳定. 对由10个原子组成的菱形原胞进行了结构优化,得到晶胞参数值(a0=0.48178n m)与实验 报道值误差小于1.3%.进一步计算了超晶胞(2×2)表面弛豫,弛豫后原第2层O原子层成为最 表层; 对不同表层O,Al原子最外层电子进行了布居分析,表面电子有更大的概率被定域在 O原子的周围,表面明显地表现出O原子的电子表面态.
Study on the structure and energy of the (0001) surface of α-Al2O3 substrate
- Received Date:
08 November 2002
- Accepted Date:
30 December 2002
- Published Online:
20 September 2003
Abstract: There are three different structures of the α-Al2O3(0001) crystal surface b ecause different atoms are terminated on the outermost layer. Our calculations a re based on the density functional theory in local density approximation, and on ultra-soft pseudopotential methods, with the valence orbital expanded in plane- wave by using three-dimensional periodic boundary conditions in κ-space, first ly, the calculation result is that α-Al2O3(0001) crystal surface structure which the outermost layer is terminated by a single layer of Al atoms is much mo re stable than the other two structures. Secondly, a rhombohedral primitive cell is employed to perform cell optimizations, with ten atoms in the unit cell, and the calculated equilibrium parameters are:a0=0.48178nm,γ=120.16, which are in excellent agreement with recent experimental values(a0=0.47591nm ),with a difference of less than 1.3%. Moreover, our calculations are performed with a su per-cell slab model in vacuum environment, in which the outermost layer is termi nated by single Al atoms. By investigating the four-layer relaxation and Al-O a toms population of the surface, we obtain results that the top single Al layer i s an inward relaxation of 0.0792 nm—0.098nm, that is, the second-layer O atoms are turned into the top layer,and the top O and Al atoms population analysis sho w that the valence electrons are concentrated on the surface oxygen ions with a greater probability,it is obvious that the α-Al2O3(0001) crystal surface ap pears in the O-surface state,which is discussed from the microstructure of α-Al 2O3(0001)crystals in details.