用中能电子向前散射图像研究表面原子结构

INVESTIGATION OF THE ATOMIC STRUCTURE OF SURFACES BY MEANS OF FORWARD SCATTERING OF MEDIUM ENERGY ELECTRONS

从中能电子向前散射产生的实空间图像研究了Ｃｕ（１１１）１×１，Ｓｉ（１１１）（３×３）Ｒ３０°Ｉｎ及Ｇｅ（１１１）（３×３）Ｒ３０°Ａｇ的表面结构．Ｃｕ（１１１）１×１的图像不仅说明表面有三重旋转轴对称性，而且还表明ｆｃｃ结构一直保持到最表面一层原子．Ｓｉ（１１１）（３×３）Ｒ３０°Ｉｎ表面的图像说明Ｉｎ原子占据Ｔ４位，而不是Ｈ３位．Ｇｅ（１１１）（３×３）Ｒ３０°Ａｇ的图像说明ＨＣＴ模型是正确的．这些成功的应用说明从中能电子向前散射图像可以直观而且快捷地获得表面结构类型的可靠信息。

The atomic structure of several surfaces has been investigated on the basis of the real space patterns formed by forward scattering of medium energy electrons from the surface.The images of the Cu(111) surface show not only that the surface has the three fold symmetry but also that the fcc stacking sequence persists up to the topmost atomic layer.The images of the Si(111)(3×3) R 30° In surface support that In atoms occupy the T4 sites on the surface,rather than the H3 sites.In the case of Ge(111)(3×3) R 30° Ag surface the images indicate that the honeycomb chained triangle (HCT) model is correct.The success of these applications shows that reliable structural information of surfaces can be obtained quite straightforward by means of forward scattering of medium energy electrons,instead of via complicated calculations such as involved in LEED crystallography.