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

在光子工厂用表面x射线衍射技术研究了Si(111)-6xl-Ag的表面结构。通过分析沿00棒的CTR散射强度，确定了银原子和重构硅原子垂直于表面的位置。结果与在Si（111）衬底上由碱金属诱导的3xl结构的HCC模型吻合得很好。测定的表面Ag和Si原子高度表明，当表面结构由Si(111)-√<3>x√<3>-Ag转变为Si(111)-6xl-Ag时，由于Ag原子的解吸作用，表面原子几乎没有垂直位移。通过测量，确定了表面银原子的面内排列。结果表明，在6xl和3xl结构之间的相变过程中，Ag原子横向移动距离较大。接下来，我们利用表面x射线衍射研究了Si(111)-5x2-Au的结构。通过对衍射斑点的测量，对其表面结构进行了分析。对三个模型进行最小二乘拟合；通过透射电子衍射（1995）提出的Marks and Plass模型和Erwin（2003）和Riikonen（2005）基于第一性原理计算的理论模型。结果表明，最可能的模型是Erwin模型，但结构参数需要进行较大的修改。同样，我们研究了表面埋有约5nm厚度的非晶硅层时的Si(111)-5x2-Au结构。从埋藏界面处可以清楚地观察到一些衍射斑。观测到的CTR散射强度分布与Erwin模型计算的结果一致。

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.