用可调探深的电子能量损失谱研究Sn/Si界面

用可调探测深度的电子能量损失谱辅以俄歇电子能谱和低能电子衍射,研究Sn/Si系统的界面反应。结果表明:当Sn蒸镀量大于两个原子单层,退火温度由400℃到700℃,在Sn/Si(111)界面Sn与Si发生互混,形成几个原子层厚的Sn/Si互混层,该互混层的特征体峰在15.5eV。在相同温度范围退火,Sn/Si(001)界面无可察觉的互混,仍有Sn岛存在,长时间在550℃退火低能电子衍射图形上出现(113)小晶面的衍射斑。 关键词：     

Moir patterns and step edges on few-layer graphene grown on nickel films

Few-layer graphene grown on Ni thin films has been studied by scanning tunneling microscopy. In most areas on the surfaces, moir′e patterns resulted from rotational stacking faults were observed. At a bias lower than 200 mV, only one sublattice shows up in regions without moir′e patterns while both sublattices are seen in regions with moir′e pattens. This phenomenon can be used to identify AB stacked regions. The scattering characteristics at various types of step edges are different from those of monolayer graphene edges, either armchair or zigzag.     

一维石墨烯超晶格上的氢吸附

通过化学气相沉积法在一种典型的高指数面铜(410)-氧上制备出了一维石墨烯超晶格,并利用拉曼光谱(Raman)、低能电子衍射(LEED)、扫描隧道显微术(STM)等方法研究了氢原子在该超晶格上的吸附.实验结果揭示了由于超晶格的调制作用所引起的无缺陷石墨烯区域的选择性吸附,氢原子优先吸附在石墨烯超晶格一维周期中的相同部位.这一发现为进一步通过一维超晶格调控石墨烯的性质提供了更多可能.在石墨烯上的吸附氢原子除了单个或成对存在之外,实验还首次观察到一种新的三氢原子位型.     

甘氨酸在Cu(001)表面的吸附结构

结合低能电子衍射(LEED)及其消失斑点规律和扫描隧道显微镜(STM)手段确定了室温下甘氨酸在Cu(001)表面能形成c(2×4)和两种(2×4)吸附结构((2×4)₁和(2×4)₂),并推断出在两种(2×4)结构单胞中两甘氨酸分子的羧基相对于衬底的吸附取向一致,而它们的氨基则不同.实验中还观察到c(2×4)与(2×4)₂结构能相互转变成窄条相互穿插共存,这说明几种吸附结构能量相近. 关键词：     

QUASI-KINEMATIC LOW-ENERGY ELECTRON DIFFRACTION AND ITS LATEST APPLICATIONS

In order to determine the structure of complex and/or stepped surfaces that are very difficult to or even beyond the capability of the full dynamic low-energy electron diffraction calculation, recently we have proposed the quasi-kinematic low-energy electron diffraction (QKLEED) approach and employed it to solve the structure of some important surfaces such as Si(111)-(3^1/2×3^1/2) R30°-Al and Si(111)-(3^1/2×3^1/2) R30°-Ag. In the present paper, following the highlights of QKLEED we give the latest application of it, i.e., the structural determination of the Si(111)-(3^1/2×3^1/2) R30°-Au, Si(111)-(3^1/2×3^1/2) R30°-Sn, and Pd(001)-c(2×2)-Mn surfaces.     

一种改进的运动学低能电子衍射和数据平均方法在Si(111)3~(1/2)×3~(1/2)-Al表面上的应用

本工作运用运动学低能电子衍射和数据平均方法(KLEED和CMTA),对Si(111)3~(1/2)×3~(1/2)-Al表面的原子结构进行研究。在大的参数范围内对T_4和H模型进行优化后,发现T_4模型与实验符合得更好(R_(VHT)=0.158),并且定出Al原子和最上面六层Si原子的位置。该模型中所有键长相对于体内值的变化都在5％以内。它与由全动力学低能电子衍射(DL-EED)分析得到的模型完全相符。这一成功的应用再次表明改进后的KLEED和CMTA方法是一种简单、实用、可靠的表面结构分析手段,用它对一些很复杂的表面进行结构分析已成为可能。     

Adsorption geometry of glycine on Cu（001） determined with low—energy electron diffraction and scanning tunnelling microscopy

Using low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) it has been found that glycine molecules adsorbed on Cu(001) can form but only the (2×4) and c(2×4) superstructures. On the basis of the missing LEED spots of the surface, it has been concluded that: each (2×4) unit cell consists of two molecules, one being the mirror image of the other; the C－C axis of both molecules lies in the mirror plane of the Cu substrate without a significant shift and twist from the plane; and the two O atoms of the carboxylate group of both molecules locate at the same height level without significant buckling. According to these conclusions, a structural model has been proposed for the (2×4) superstructure (a model for the c(2×4) superstructure already exists). We argue that the (2×4) and c(2×4) superstructures must have similar specific surface free energy, that their hydrogen bonds must be of N-H-O_II type, and that their local adsorption geometry must be similar or even the same. The advantage of combining STM with LEED to determine surface structures is clearly demonstrated.     

Moire patterns and step edges on few-layer graohene grown on nickel films

Few-layer graphene grown on Ni thin films has been studied by scanning tunneling microscopy. In most areas on the surfaces, moir6 patterns resulted from rotational stacking faults were observed. At a bias lower than 200 mV, only one sublattice shows up in regions without moir6 patterns while both sublattices are seen in regions with moir6 pattens. This phenomenon can be used to identify AB stacked regions. The scattering characteristics at various types of step edges are different from those of monolayer graphene edges, either armchair or zigzag.     

三个新的稳定硅表面及其家族领地

为了对稳定硅表面进行广泛的搜索,利用低能电子衍射(LEED)研究了13个散布在极射投影三角内各处的高指数硅表面:Si(10　4　13),(6　2　7),(8　4　11),(4　1　10),(2　1　5),(5　1　10),(5　2　10),(5　1　5),(5　1　6),(4　0　5),(12　4　19),(12　3　14)和(12　3　16).结果发现这些清洁的硅表面都不稳定,因为在被充分退火后,它们会彻底小面化成为分属一个或几个稳定表面的小面.提出了一套行之有效的方法,使小面化表面的复杂LEED图得以可靠地标定,进而确定了全部出现的稳定表面的指数.除已知的Si(15　3　23)外,还发现三个新的稳定表面,即Si(20　4　23),(3　1　4)和(3　1　7).同时也粗略地确定了它们的家族领地为了对稳定硅表面进行广泛的搜索,利用低能电子衍射(LEED)研究了13个散布在极射投影三角内各处的高指数硅表面:Si(10　4　13),(6　2　7),(8　4　11),(4　1　10),(2　1　5),(5　1　10),(5　2　10),(5　1　5),(5　1　6),(4　0　5),(12　4　19),(12　3　14)和(12　3　16).结果发现这些清洁的硅表面都不稳定,因为在被充分退火后,它们会彻底小面化成为分属一个或几个稳定表面的小面.提出了一套行之有效的方法,使小面化表面的复杂LEED图得以可靠地标定,进而确定了全部出现的稳定表面的指数.除已知的Si(15　3　23)外,还发现三个新的稳定表面,即Si(20　4　23),(3　1　4)和(3　1　7).同时也粗略地确定了它们的家族领地 关键词： 高指数表面 硅 铟 小面化     

室温下单个甘氨酸分子在Cu(111)表面的操纵研究

先用低能电子衍射(LEED)证明了甘氨酸(NH₂-CH₂-COOH)能在室温下在Cu单晶表面产生比较稳定的吸附，然后用扫描隧道显微镜(STM)进一步研究了其吸附情况，看到单个甘氨酸分子在Cu(111)面上吸附稳定并至少有三种吸附状态.分子操纵研究结果表明，甘氨酸分子是被针尖“推着”移动的，它在Cu(111)面有固定的吸附位，并且移动时其吸附状态可以不变.研究结果表明，甘氨酸适合做室温下小分子的可控操纵研究，并且也说明室温下小分子的可控操纵是可能的. 关键词：