Au(111)表面自组装硫醇单分子膜的STM成像机理

本文利用基于密度泛函理论的算法模拟Au(111)表面紧密堆构型的烷烃硫醇自组装单分子层膜(SAMs)中单分子的扫描隧道显微镜(STM)图像，发现图像细节依赖于偏压和烃链链长，主要由受电子效应影响的形貌效应决定。同时进行了电子结构分析以研究硫醇SAMs的STM成像机制，还发现烷烃硫醇分子中的S原子在Au表面的吸附模式也明显地影响着STM图像细节。     

Au(111)表面Dy@C82分子单层膜的STM研究

利用超高真空扫描隧道显微镜(UHV-STM),在低温(78K)下研究了不同覆盖度下Dy@C82(Ⅰ)膜在Au(111)表面的生长和结构.Dy@C82分子首先吸附于金台阶,进而延伸至金台面上形成紧密排列的一维分子链或二维分子岛.高分辨STM图像显示ZDy@C82分子具有多种不同的内部结构,表明Dy@C82分子在金表面的取向是无序的.     

基于隧道电流检测方式的原子力显微镜纳米检测系统设计

原子力显微镜（AFM）是当前进行材料表面微观形貌观察及分析的强有力工具之一。本文主要介绍一种隧道显微镜（STM）检测方式的原子力显微镜纳米检测系统（AFM.IPC-208B）,该AFM系统设计是在STM.IPC-205B系统设计的基础上,采用隧道电流工作方式,将STM与AFM功能组合兼容。文章详细阐述了AFM.IPC-208B系统的设计原理、镜体、扫描控制以及数据采集。新设计的AFM.IPC-208B系统仍具有0.1nm的分辨率,检测范围为0～2mm×2mm,系统操作简易,工作效率高,与原STM.IPC-205B系统兼容,工作性能稳定可靠。     

C90分子单层膜在Au(111)表面的STM研究

在超高真空中使用热蒸发方法,在Au(111)表面上制备了C90分子的分子单层膜,并利用超高真空低温扫描隧道显微镜在120 K温度下对其结构进行研究.观察到C90分子在Au(111)表面上先是沿着台阶边缘生长,分子铺满一层后,会在薄膜上形成岛状结构.本文对岛状结构进行了原位高分辨表征,观察到C90分子在正偏压和负偏压下的...     

激光原子力显微镜及其对光学表面粗糙度的研究

自一九八五年,Binnig与斯坦福大学的Quate和IBM公司苏黎士实验室的Christoph合作推出了世界上第一台原子力显微镜(简称AFM)以来,AFM的研究及应用迅速扩展。它不仅象扫描隧道显微镜那样能从原子尺度上对导体、半导体表面而且还能对非导体的表面进行成像,拓宽了STM的应用范围。     

金纳米棒在Au(111)表面上的分散与STM表征

本文报道了金纳米棒的合成、在Au(111)表面上的分散、有机污染物清洗以及STM形貌表征工作.金纳米棒通过金晶种在金生长液中的选择性生长来制备.通过对金纳米棒和Au(111)表面进行修饰,利用涂层外端基团之间的静电相吸作用,把金纳米棒经由点滴法均匀地吸附在Au(111)表面上,且分散密度可通过点滴次数加以控制.本文进一...     

C_(90)分子单层膜在Au(111)表面的STM研究

在超高真空中使用热蒸发方法,在Au(111)表面上制备了C90分子的分子单层膜,并利用超高真空低温扫描隧道显微镜在120 K温度下对其结构进行研究。观察到C90分子在Au(111)表面上先是沿着台阶边缘生长,分子铺满一层后,会在薄膜上形成岛状结构。本文对岛状结构进行了原位高分辨表征,观察到C90分子在正偏压和负偏压下的几种不同形貌,并给出了各种形貌所对应的C90分子构型。     

半金属表面上酞菁锰分子的转动态研究

利用低温STM研究了半金属Bi(111)表面上单个酞菁锰分子的转动态。通过高分辨STM图发现,在液氮温度(77K)下单个酞菁锰分子呈六角形。利用STM操纵技术实现了对单个酞菁锰分子的制动,并通过对单分子的高低起伏和吸附构型分析,确定分子在Bi(111)表面做非连续的中心转动。这种单分子转动是三种相对稳定的吸附构型交替变化的结果。结合I-t谱技术,进一步验证了这三种分子吸附构型的存在;并利用近似统计分析方法得到三种吸附构型各自出现的概率以及其相对能量。     

分子取向的高分辨率扫描隧道显微术

本文介绍了一种借助于扫描隧道显微镜的空间高分辨能力探测单个分子取向的方法.利用这种方法,我们研究了以下四种体系中的分子取向二维C 60分子阵列;C 60(111)多层膜表面;吸附在Si(111) (7×7)表面的C 60单分子;Au(111)表面的硫醇自组装单分子层膜.结合局域密度近似方法理论计算,我们确定了以上体系中的分子取向.     

纳米操纵辅助的原子力显微镜原位定位观察

在原子力显微镜（atomic force microscope,AFM）原位定位观察中,时常会遇到因失去标记物而无法定位的情况。本文介绍了一种在表面标记物被覆盖后,运用原子力显微镜的操纵功能,将标记物上的覆盖物“扫”开,重新找到标记物并用于精确定位的方法。以对高序热解石墨（highly ordered pyrolytic graphite,HOPG）表面牛血清白蛋白（bovine serum albumin,BSA）吸附的原位观察为例,在BSA膜覆盖HOPG表面的原子台阶后．采用接触模式AFM扫描,将BSA“扫”开,露出HOPG原子台阶作为标记,对图像上的结构进行精确定位。通过调节设置点、扫描范围、扫描速率、扫描线数、偏置值等戍像参数及扫描时间,可以控制“清扫”的力度和范围。     

Highly Ordered 2D Hydrogen‐Bonded Structures of a Tetralactam Macrocycle on the Au(111) Surface

Monolayers of a tetralactam macrocycle, which are commonly used as building blocks in the synthesis of rotaxanes or catenanes, are deposited on a Au(111) surface by using vapor deposition. Due to self‐organization, 2D highly ordered supramolecular networks form. From scanning tunneling microscopy (STM) and concomitant density‐function theory calculations, two structurally different phases are found. In both phases, pairs of hydrogen bonds between the amide groups of next‐neighbor macrocycles are responsible for the structural arrangement of the macrocycles. The structure of both phases differs from that of bulk lattice planes, which reveals that the Au(111) surface acts as a template for the growth of the specific 2D structures. These networks of tetralactam macrocycles possibly open a route to study mechanical interlocking processes or guest/host interactions of the molecules in further detail by using STM.     

Novel local density of state mapping technique for low-dimensional systems

A novel local density of state (LDOS) probing method for low-dimensional electron systems is proposed. By applying a two-dimensional fast Fourier transform to a real-space image obtained by scanning tunneling microscopy (STM), visualization of a complementary image in k-space can be realized. Especially, low-dimensional Fermi contours can be extracted by applying the k-space imaging to real-space images containing sufficient LDOS information around the Fermi level. To realize a more enhanced LDOS visualization in both spaces, we have proposed the use of special materials for STM tips, which have relatively large LDOSs at the Fermi level. To demonstrate this idea, several kinds of STM tips (Ag, Au, W and Nb) with different types of LDOSs were developed. An Au(111)-(22 x square root(3)) reconstructed surface, where Shockley surface-state electrons form a nearly free electron gas, was selected as a test sample for the LDOS extraction. Visualization of standing waves in the surface LDOS modulated by herringbone reconstruction was attempted using the various types of STM tips. Significant effects of the LDOSs of the STM tips were clarified.     

Induced SER‐Activity in Nanostructured Ag–Silica–Au Supports via Long‐Range Plasmon Coupling

A novel Ag–silica–Au hybrid device is developed that displays a long‐range plasmon transfer of Ag to Au leading to enhanced Raman scattering of molecules largely separated from the optically excited Ag surface. A nanoscopically rough Ag surface is coated by a silica spacer of variable thickness from ～1 to 21 nm and a thin Au film of ～25 nm thickness. The outer Au surface is further functionalized by a self‐assembled monolayer (SAM) for electrostatic binding of the heme protein cytochrome c (Cyt c) that serves as a Raman probe and model enzyme. High‐quality surface‐enhanced resonance Raman (SERR) spectra are obtained with 413 nm excitation, demonstrating that the enhancement results exclusively from excitation of Ag surface plasmons. The enhancement factor is estimated to be 2 × 10⁴–8 × 10³ for a separation of Cyt c from the Ag surface by 28–47 nm, corresponding to an attenuation of the enhancement by a factor of only 2–6 compared to Cyt c adsorbed directly on a SAM‐coated Ag electrode. Upon immobilization of Cyt c on the functionalized Ag–silica–Au device, the native structure and redox properties are preserved as demonstrated by time‐ and potential‐dependent SERR spectroscopy.     

Simultaneous STM and UHV electron microscope observation of silicon nanowires extracted from Si(111) surface

A miniaturized scanning tunnelling microscope (STM) was fitted in a side-entry holder of an ultra-high vacuum electron microscope. The clean Si(111)7 x 7 surface was observed by both STM and reflection electron microscopy (REM) at atomic resolution. The tungsten tips were often rounded off upon tip-approach with a constant current, through a gentle touch with the sample surface. The apices of such rounded tips had radii of several tens of granometre with widths of about 3 x 3 nm. Atomically resolved STM of the Si(111)7 x 7 surface was obtainable when an atom or an atomic cluster sits on the tip surface. The rounded tips were used for fabrication of Si nanowires by the touch-and-away operation of the tip. The nanowires grew longer at higher substrate temperature and they reached as long as several tens of nanometre at 700 degrees C. The nanowire had many twins and the (111) twin lamellae were stacked in the direction of the wire axis. In another case, the twin planes were oblique to the wire axis so that the (112) direction was nearly parallel to the wire axis.     

Structural Dynamics of Ultrathin Cobalt Oxide Nanoislands under Potential Control

Cobalt oxide is a promising earth abundant electrocatalyst and one of the most intensively studied oxides in electrocatalysis. In this study, the structural dynamics of well-defined cobalt oxide nanoislands (NIs) on Au(111) are investigated in situ under potential control. The samples are prepared in ultra-high vacuum and the system is characterized using scanning tunneling microscopy (STM). After transfer into the electrochemical environment, the structure, mobility, and dissolution is studied via in situ electrochemical (EC) STM, cyclic voltammetry, and EC on-line inductively coupled plasma mass spectrometry. Cobalt oxide on Au(111) forms bilayer (BL) and double-bilayer NIs (DL), which are stable at the open circuit potential (0.8 V_RHE). In the cathodic scan, the cobalt oxide BL islands become mobile at potentials of 0.5 V_RHE and start dissolving at potentials below. In sharp contrast to the BL islands, the DL islands retain their morphology up to much lower potential. The re-deposition of Co aggregates is observed close to the reduction potential of Co²⁺ to Co³⁺. In the anodic scan, both the BL and DL islands retain their morphology up to 1.5 V_RHE. Even under these conditions, the islands do not show dissolution during the oxygen evolution reaction (OER) while maintaining their high OER activity.