Study on the one-dimensional structure of metals on semiconductor surfaces and buried interfaces

在Photon Factory使用表面X射线衍射技术研究Si（111）-6xl-Ag的表面结构。通过分析沿着00棒的CTR散射强度，确定了Ag和重构Si原子垂直于表面的位置。结果与提出的碱金属在Si（111）衬底上诱导的3xl结构的HCC模型一致。由此测定的表面Ag和Si原子的高度表明，当表面结构由Si（111）-x-Ag转变为Si（111）-6xl-Ag时，这些表面原子几乎没有垂直位移<3><3>。从GIXD测量，确定表面Ag原子的面内排列。结果表明，Ag原子在6xl和3xl结构之间的相变中横向移动了很大的距离。接下来，我们利用表面X射线衍射研究了Si（111）-5x2-Au的结构。通过GIXD观察到的衍射斑点的测量来分析表面结构。对三种模型进行最小二乘拟合;由透射电子衍射（1995）提出的Marks和Plass模型以及基于Erwin（2003）和Riikonen（2005）的第一性原理计算的理论模型。结果表明，最可能的模型是欧文模型，但结构参数应作较大修改。类似地，我们研究了当表面用约5 nm厚的非晶硅层掩埋时的Si（111）-5 x2-Au结构。我们可以清楚地观察到一些来自掩埋界面的衍射斑点。观察到的CTR散射强度分布与Erwin模型计算的一致。

The surface structure of Si(111)-6xl-Ag was investigated using surface X-ray diffraction techniques at the Photon Factory. By analyzing the CTR scattering intensities along 00 rod, the positions of the Ag and reconstructed Si atoms perpendicular to the surface were determined. The results agreed well with the HCC model proposed for a 3xl structure induced by alkali-metals on a Si(111) substrate. The heights of the surface Ag and Si atoms thus determined show that those surface atoms make little perpendicular displacement when the surface structure changes from Si(111)-√<3>x√<3>-Ag to Si(111)-6xl-Ag by the desorption of the Ag atoms. From the GIXD measurement, the in-plane arrangement of the surface Ag atoms was determined. The results indicate that the Ag atoms move large distances laterally at the phase transition between the 6xl and 3xl structures.Next we studied the structure of Si(111)-5x2-Au using surface X-ray diffraction. The surface structure was analyzed from the measurements of diffraction spots observed by GIXD. The least-squrares fit was done for the three models; Marks and Plass model proposed by transmission electron diffraction (1995) and theoretical models based on the first principles calculations by Erwin (2003) and Riikonen (2005). The results indicate that the most probable model is Erwin's model, but the structural parameters should be modified considerably. Similarly, we studied the Si(111)-5x2-Au structure when the surface is buried with a amorphous silicon layer of about 5 nm thickness. We could clearly observe some diffraction spots from the buried interface. The CTR scattering intensity distributions observed were consistent with those calculated for Erwin's model.