金粗糙表面原子水平的STM研究

至今为止所报道的对固体表面原子水平的研究几乎毫无例外的局限在单晶表面。其主要原因之一是存在着在多晶或粗糙表面上获得原子分辨ＳＴＭ图象的困难性。尽管如此，由于多晶材料是更为普遍、更切实际的进行各种物理和化学过程的场所，若能实现多晶或粗糙表面的原子水平的观察，其研究意义和前景将大为拓宽。本文报道在含氯化钾的电化学体系中极端条件下金（１１１）面和多晶金表面结构的原子水平的ＳＴＭ观察。图一为Ａｕ（１１１）面在不同条件下的电化学现场ＳＴＭ图。在４００～－４００ｍＶ电位区间内Ａｕ（１１１）保持稳定的（１ｘ１）结构，未观察到来自于Ａｕ表面的重构或Ｃｌ－吸附层结构。当电位负移至－６００以内，尽管此时金电极仍处于双电层区，Ａｕ表面已出现一定程度的粗糙。有趣的是，当电位经过１．０Ｖ后返回至０Ｖ时，大范围的ＳＴＭ图象显示了由原子台阶构成的孔洞和原子平整的晶面共成的情形。图二为空气下得到的金多晶的表面形貌（Ａ）和原子分辨表面结构（Ｂ）的ＳＴＭ图。分析图二（Ｂ）和（Ｃ）可以得知，图中两亮点之间的平均距离为０．４ｎｍ，可以排除原子簇结构的可能。可以确定这些具有一定取向的亮点为原子阵列，而较大的原子间距正反应了多晶表面与本体结构的不同之     

液晶吸附结构的STM形貌研究

在室温下 ,利用扫描隧道显微镜 (STM )对 4 戊基 4′ 甲氧基苯甲酸苯酯吸附在石墨基底上的结构进行了研究 ,结果表明分子为单层且有一定位错的头 (甲氧基 )对头、尾 (烷基 )对尾排列 ;理论计算表明 :外加偏压产生的电场对分子轨道能级及其极化率具有一定的影响 ;由于分子的HOMO ,LUMO能级与石墨费米能级之间的能量差值较大 ,低偏压下不利于STM成象 ,因此 ,分子的极化率对石墨基底功函数的影响可能是形成该液晶分子STM形貌的主要因素 .     

沥青基碳纤维表面复合处理的研究

研究了硝权氧化和硝酸－钛酸酯复合对沥青基碳纤维（Ｃ－１２）进行表面处理的影响。利用富里衰转换红外光谱扫描、接触角测定及Ｘ－射触角测定及Ｘ－射线衍射等手段,对表面处理各阶段碳纤维的性能与结构进行表征。复合处理与砂酸氧化的机理与效果不同,红外光谱中有新峰出现,纤维表面极性与浸润性发生了变化,认为复合处理方法将有利于拓宽碳纤维的应用范围。     

液晶CPBOB吸附的STM研究

利用STM对吸附在导电基底上的液晶进行研究，能提供近原子分辨的液晶分子图象，这一创新不仅拓宽了STM的研究领域，也使STM成为研究液晶吸附的重要手段之一．根据液晶相变特征不同，样品的制备方法大致分四种情况：直接法，加热法，气相沉积法和溶剂法．无论采用以上哪种方法，     

表面分子手性识别与组装结构的STM研究

表面手性现象是物理化学科学研究的重要内容之一,研究表面手性现象,将有助于对分子吸附,分子间相互作用,多相手性催化,手性分离与拆分等科学和实际应用问题的深入理解.在表面手性现象和手性结构的研究中,扫描隧道显微技术（STM）发挥着重要作用,成为研究表面手性现象的重要手段.该综述文章以本课题组近年已发表的研究工作为主,重点介绍利用STM研究固体表面分子吸附组装体系中关于手性问题的部分结果,包括固有手性分子在固体表面的吸附,非手性分子组装形成手性结构,以及表面手性结构的转化和调控.还结合实验结果分析探讨了表面手性的结构形成、放大和传递等,展望了该研究领域的发展趋势.     

化学修饰针尖对STM成像及物种识别研究的进展

化学修饰的STM（扫描隧道显微镜：Scanning Tunneling Microscope)针尖可以改变STM图像的反差,影响STM成像,这一功能现已被发展用于成分及物种识别。本文简要介绍了与其相关研究的应用与进展。     

发光多孔硅表面的STM研究

自从Canham首次报道了室温下多孔硅的光致发光现象以来^[1],多孔硅已成为半导体光电化学及材料领域内最为热门的研究课题^[2].     

谢尔宾斯基三角分形结构的STM研究

分形结构因其特殊的数学和美学意义受到科学家们长期以来的广泛关注。化学家更是试图利用共价键和配位键等来合成各类分子分形结构,但由于溶解性的限制,始终无法实现高级别、无缺陷的分子分形结构的构筑。最近我们采用超高真空表面制备方法,成功获得了基于卤键与配位键的谢尔宾斯基三角分形结构,并使用扫描隧道显微镜(STM)对其生长机制进行了研究。4, 4′′′-二溴-1, 1′:3′, 1′′:4′′, 1′′′-四联苯分子在Ag(111)表面通过自组装形成了一系列无缺陷卤键分形结构。由于卤键作用较弱,该结构只能稳定在液氮温度以下。在Au(111)表面共沉积4, 4′′-二氰基-1, 1′:3′, 1′′-三联苯分子与铁原子可以制备出更稳定的配位分形结构。密度泛函理论计算揭示了分形结构的成像机制。蒙特卡洛计算表明,表面三节点的形成对谢尔宾斯基三角分形结构的生长具有重要意义。     

芳香化合物STM研究的进展

本文系统介绍了用STM技术研究苯、萘和蒽等芳香化合物的诸多成果，表明分子间相互作用、分子与基底间相互作用等对该类化合物吸附结构的影响，以及溶液中分子的结构、结构转化及表面反应与电极电位的关系，阐明了在原子分子惊讶上研究芳香化合物的重要性及发展趋势。     

稀土/纳米TiO2的表面电子结构

用浸泽法对纳米TiO2粉末进行稀土处理，制得稀土／纳米TiO2光催化功能材料。利用扫描隧道显微镜／扫描隧道谱技术研究稀土／TiO2纳米光催化材料的表面电子结构。结果表明：在纳米TiO2中加入铈元素制备的Ce/TiO2纳米粉末材料，其表面禁带内－0．8及 0.5eV附近可出现新能级，稀土能促进羟基自由基产生、提高光催化活性，可实现可见光条件下光催化净化空气。     

Scanning tunneling microscopy on clean and adsorbate covered metal surfaces

The use of scanning tunneling microscopy (STM) for atomic scale characterization of clean and adsorbate covered (single-crystalline) metal surfaces is discussed. Topographic images reveal details on their periodic structure and on the atomic arrangement in the surface layer, and in particular on surface defects. The observation and characterization of individual adsorbate species gives access to the local electronic structure of the adsorption complex and to details of the chemical bond between substrate and adsorbate. Atomic resolution imaging opens new perspectives for the investigation of various surface processes such as surface diffusion, thin film growth or surface reactions.     

扫描隧道显微镜在有机化学中的应用

扫描隧道显微镜的最大优点是可达到原子量级的分辨率。本文综述了STM对有机分子的结构、聚集形态及其反应过程的研究。     

Scanning tunneling microscopy study of fullerenes

Scanning tunneling microscopy investigations of adsorption and film growth of various fullerenes on semiconductor and metal surfaces are reviewed. The fullerenes being studied are C₆₀, C₇₀, C₈₄, Sc@C₈₂ and Y@C₈₂ and the substrates being used for adsorption are Si (111), Si (100), Ge (111), GaAs (110), GaAs (001), Au (111), Au (110), Au (100), Cu (111) and Ag (111) surfaces.     

Au-Induced Faceting of Si(5 5 12)

The growth of Au on the stable, high-index Si(5512) surface has been studied using scanning tunneling microscopy (STM). At very low coverages and moderate annealing temperatures (0.1ML, 400–500°C), Au appears to decorate the underlying Si rows and form an array of rows that maintains the underlying (5512) periodicity of 5.4nm. For higher annealing temperatures and coverages, however, Au causes faceting to a number of nearby planes. The two primary facets formed at lower (0.15ML) and higher (0.5–2ML) coverages are the (337) and (225) planes, which are tilted 0.7° down [towards (111)] and 1.1° up from (5512), respectively. Both orientations are in fact subunits of the (5512) unit cell, so their presence is not surprising. In addition to these facets, two types of sawtooth morphologies composed of planes oriented further from (5512) are found at very high annealing temperatures (800–900°C). These include (113)+(7715) planes at very low coverage (0.05ml) and (113)+(5511) planes at higher coverage (1ML), where (113) is tilted up by 5.3° and (7715) and (5511) are tilted down by 2.9° and 2.2°, respectively. Au adsorption on Si(5512) therefore results in the formation of five possible facet planes: (113), (225), (337), (5511), and (7715).     

Isolated supramolecules on surfaces studied with scanning tunneling microscopy

To date, supramolecular chemistry is an ever growing research field owing to its crucial role in molecular catalysis, recognition, medicine, data storage and processing as well as artificial photosynthetic devices.Different isolated supramolecules were prepared by molecular self-assembly on surfaces. This review mainly focuses on supramolecular aggregations on noble metal surfaces studied by scanning tunneling microscopy, including dimers, trimers, tetramers, pentamers, wire-like assemblies and Sierpin′ ski triangular fractals. The variety of self-assembled structures reflects the subtle balance between intermolecular and molecule–substrate interactions, which to some extent may be controlled by molecules, substrates and the molecular coverage. The comparative study of different architectures helps identifying the operative mechanisms that lead to the structural motifs. The application of these mechanisms may lead to novel assemblies with tailored physicochemical properties.     

The effect of electrochemical surface treatments of carbon fibers using scanning tunneling microscopy

Scanning tunneling microscopy (STM) has been applied to the study of the topography of polyacrylonitrile (PAN)-based carbon fibers before and after electrochemical surface treatments. The results show that the electrical anodic oxidation only changes the surface aspects; at nanometric resolution; the nanostructure and nanotexture such as the step-like crystallite stacking are decreased with increasing electric current densities.     

Atomic-scale scanning tunneling microscopy study of plasma-oxidized ultrahigh-modulus carbon fiber surfaces

In the present work, scanning tunneling microscopy (STM) was employed to study the surface modification of ultrahigh modulus carbon fibers at the atomic level by oxygen plasma. As detected by STM, the distinctive feature of the fresh, untreated surface was the general presence of atomic-scale arrangements in different degrees of order (from atomic-sized spots without a clearly ordered disposition to triangular patterns identical to those typical of perfect graphite). Following fiber exposure to the plasma, the STM images showed evidence of the abstraction of carbon atoms from random locations on the fiber surface, giving rise to the development of defects (i.e., structural disorder), which in turn were the places where oxygen could be introduced during and after the plasma etching. It was observed that the most effective treatments in terms of extent of surface structural modification (disordering) and uniform introduction of oxygen were those carried out for just a few ( approximately 3) minutes. Considerably shorter exposures failed to provide a homogeneous modification and many locations on the fiber surface remained unaltered, retaining their original atomic-scale order, whereas longer treatments did not bring about further structural changes to the surface and only led to fiber consumption. These results are consistent with previous X-ray photoelectron spectroscopy measurements on these fibers and provide an atomic-level understanding of the saturation effect observed in the surface oxygen concentration of this and other types of carbon fibers with plasma oxidation. Such understanding may also prove helpful for the accurate control and optimization of fiber-matrix interaction in composite materials.     

Nucleation and growth of Ge nanoclusters on the Si(111)‐(7 × 7) surface studied by scanning tunneling microscopy

Nucleation and growth of two‐dimensional Ge nanoclusters on the Si(111)‐(7 × 7) surface at elevated substrate temperatures have been studied using scanning tunneling microscopy. The uniformity of the Ge nanoclusters is improved with the increase of substrate temperature, and ordered Ge nanoclusters are formed on the faulted and unfaulted halves of (7 × 7) unit cell at substrate temperature of 200 °C. It is proposed that the Ge nanoclusters consist of six Ge atoms with three on top of the center adatoms and others on the rest atoms within one half of a unit cell. Copyright © 2014 John Wiley & Sons, Ltd.     

Scanning tunneling microscopy study of DNA-chromophore motif on solid surfaces

We focus our studies on DNA-chromophore motif on surfaces using samples prepared by the synthetic methods described by Wang and Li in a recent publication (J. Am. Chem. Soc. 2003, 125, 5248-5249). Scanning tunneling microscope (STM) was used to investigate the DNA-chromophore hybrids adsorbed on Au(111) and highly oriented pyrolytic graphite (HOPG) surfaces at room temperature in air. Experiments found that the DNA-chromophore hybrid molecules easily formed multimolecule aggregations on gold surface. On HOPG surfaces, however, DNA-chromophore hybrids were usually adsorbed as single molecules. STM images further showed DNA-chromophore hybrids adsorbed on Au(111) surfaces existed in the form of single molecule, dimer, trimer, tetramer, etc. The occurrence of molecular aggregations indicates that molecular interactions are comparable or stronger than molecule-substrate interactions; such weak interactions control the geometrical sizes and topographical shapes of the self-assembled DNA-chromophore hybrids on surfaces.     

Electric properties of self-assembled monolayers of helical peptides by scanning tunneling spectroscopy

Helical peptides having a disulfide group at one terminal, Lipo-(Leu-Aib)₁₂-OBzl (Lipo and OBzl represent lipoic acid and benzyl ester, respectively, SSL24B), and Boc-NHCH₂CH₂NHCO-Fc-CO-Ala-(Leu-Aib)₈-lipoamide (Boc, Fc, and lipoamide represent t-butyloxycarbonyl, ferrocene, and lipoamine, respectively, FcL16SS), were synthesized, and self-assembled monolayers (SAMs) of the helical peptides were prepared on gold. When the SSL24B SAM was observed at high-bias voltage by scanning tunneling microscopy (STM) under ultrahigh vacuum, bright spots with higher conductivity appeared in the STM image. The image was restored again to a homogeneous surface with lower bias voltage, suggesting that Au–S linkage should be reversibly changed to a conductive state. The current/voltage (I-V) curve by scanning tunneling spectroscopy (STS) at the bright domains demonstrated a rectification behavior where current increases drastically at a positive bias voltage above 3.0 V. However, the I-V curve of the FcL16SS SAM showed a current increase at negative bias voltage below −1.5 V. The redox group is, thus, a determining factor for the direction of this flow. However, STS at low-bias voltage and with the tip being inserted in the peptide SAM revealed a zero-conductance region in the I-V curve. The peptide layer may act as a molecular capacitor because of a large dielectric constant of the helical peptide. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3493–3500, 2003