Multiple—Scattering of Near—Edge x—ray Absorption Fine Structure of Sulphur—Passivated InP（100） Surface

We use the multiple-scattering cluster method to calculated the sulphur 1s near-edge x-ray absorption fine structure (NEXAFS) of S-passivated InP(100) surface.The physical origins of the resonances in the NEXAFS have been unveiled.It is shown that the most important resonance is attributed to the photoelectron scattering between the central sulphur and the nearest indium atoms.The studies show that two S-S dimers with the bond lengths of 2.05A and 3.05A coexist in the surface,meanwhile the bridge and antibridge site adsorption of single S could not be ruled out.We support the scanning tunnelling microscopy result that the S-passivated InP(100) surface exhibits significant discorder.     

N2O多层膜局域结构的多重散射簇理论研究

利用多重散射簇(multiple scattering cluster, MSC)方法计算了N2O多层膜中氮原子的1s芯态近边X射线吸收精细结构(near edge X-ray absorption fine structure, NEXAFS)谱,首次给出N2O多层膜局域结构的模型. MSC研究显示多层膜中N2O分子以短程有序的分层错位链结构排列,并求得链中相邻分子间距为0.233 nm和相邻分子层之间距离为0.240～0.245 nm.用自洽场离散变分(discrete variation, DV)Xα方法计算的N2O多层膜电子结构支持了MSC的计算结果;阐明了NEXAFS谱中弱结构的物理起源.对N2O多层膜中分子之间相互作用的分析显示N2O多层膜的结构具有分子自组装的特性.     

Cl/GaAs(111)表面近边X射线吸收精细结构的多重散射研究

利用多重散射团簇方法（MSC）计算了Cl/GaAs(111)吸附表面的Cl原子k边X射线吸收精细结构谱（NEXAFS）.阐明了NEXAFS谱中各个弱结构的物理起源.根据模型计算的结果与实验比较,求得吸附在顶位的氯原子和最近邻的镓原子的键长为（0.213±0.005）nm.这个结果在0.005 nm的误差范围内将广延X射线吸收精细结构（EXFAS）实验谱的Fourier变换结果（0.217 nm）和Slab模型计算的结果（0.208 nm）合理地联系起来.此外,MSC计算求得衬底表面层Ga－As键长为（0.235±0.005）nm,证实Cl吸附引起GaAs(111)表面驰豫.