权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Studies on the phase transition of √3 x√3-Ag structures formed on the Si(111) surface

Si(111)表面√3 x√3-Ag结构的相变研究

基本信息

批准号：
13450018
负责人：
TAKAHASHI Toshio
金额：
$ 9.47万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13450018/
关键词：
surface structure phase transition x-ray diffraction Si(111)Ag HCT IET √3x√3 structure √<3>X√<3>構造 X線回析

项目摘要

A sample manipulator, regulating the temperature from 50 K to 1400K, has been designed and fabricated for the measurements of surface X-ray diffraction planned at the beamline 15B2 of the Photon Factor in KEK.The Si(111)/3x/3-Ag surface has been formed by depositing a monolayer of silver on the clean Si(111) surface kept at 500K. The measurements of grazing incidence x-ray diffraction have been done both at a low temperature of 50K and room temperature. The integrated intensities obtained at both temperatures for 26 diffraction spots have shown different intensity distributions. Furthermore, at low temperatures, diffuse scattering has been observed, indicating the formation of twin structures in which Ag atoms forming a triangle rotate in opposite directions each other around its center. Thus the symmetry of the surface structure changes from pSm to pS.The least squares analysis of intensity data also showed that the surface takes an inequvalent Triangle structure with p3 symmetry proposed by first-principles calculations and STM studies at low temperatures, while the surface is well explained by the well-known Honeycomb Chained Triangle model if anisotropic thermal vibrations are taken into account at room temperature. The result also indicates that the phase transition belongs to a displacive one with structural changes, and doesn't support order-disorder phase transitions proposed on the basis of the Inequvalent Triangle structures.

设计并制作了一个温度范围为50 ~ 1400 K的样品操纵器，用于KEK中光子因子的15 B2束线上的表面X射线衍射测量.在500 K的清洁Si（111）表面上沉积单层银，形成Si（111）/3 x/3-Ag表面.在50 K低温和室温下进行了掠入射X射线衍射测量。在两种温度下获得的26个衍射点的积分强度显示出不同的强度分布。此外，在低温下，已经观察到漫散射，表明形成孪晶结构，其中形成三角形的Ag原子围绕其中心以彼此相反的方向旋转。强度数据的最小二乘法分析也表明，该表面需要一个不等三角形结构与p3对称性提出的第一性原理计算和STM研究在低温下，而该表面是很好地解释了著名的蜂窝链三角形模型，如果考虑到各向异性的热振动在室温下。结果还表明，该相变属于结构变化的位移相变，不支持基于不等三角结构的有序-无序相变。