原子力显微术

德国的G.Binnig和瑞士的H.Rohrer研制成功能观察到物体表面原子象的具有超高分辨率的扫描隧道显微镜(scanning tunnelingmicroscope,简记为STM),并因此而获得了1986年诺贝尔奖金物理学奖.STM的出现,导致了许多用针尖在物体表面上扫描这种形式的,但具有不同“扫描探头”的显微镜的出现.原子力显微镜(atomic force　microscope,简记为AFM)就是这类新装置中的一种. G.Binnig 早在1985年就提出了原子力显微镜的设想.STM是用隧道电流来成象的.G.Binnig想到为什么不用力来成象呢?如果能用力来成象,会比用电流来成象更优越.因为它不仅能用…     

Ge(112)-(4×1)-In表面重构的原子结构

用扫描隧道显微镜(STM)研究了亚单层In原子引起的Ge(112)-(4×1)-In表面重构.结合随偏压极性不同而显著不同的STM图象和相应的“原子图象”,为这个重构提出了一个原子结构模型,供进一步研究参考.其中,In原子的吸附位置与它在Si(112)表面的吸附位置一致,但与Al原子和Ga原子在Si(112)表面的吸附位置不同.这个吸附位置的不同主要是由In原子较长的共价键键长引起的 关键词： 表面结构 In Ge 扫描隧道显微镜(STM)     

光学相干层析成象技术的医学诊断应用

利用超短脉冲飞秒激光建立了OCT实验装置,通过对动物肾脏组织样品的层析成象,OCT图象与传统组织学图谱能找到很好的对应关系;对动物脑梗塞模型组织的扫描成象,得到了脑梗塞侧和正常侧的OCT图象,实验中,大脑病变组织和正常组织能够被正确区分。     

扫描隧道显微镜中场蒸发过程的理论分析

从电热动力学(Electrothermodynamics)角度出发，分析了扫描隧道显微镜(STM)中场蒸发过程.引入了一个有效结合能，并推导得到了STM中的蒸发场强计算公式.用该公式计算得到了与实验一致的金离子的蒸发场强.同时发现传统的电荷交换模型与成象势垒模型，由于它们要求被蒸发原子完全电离并被蒸发到无穷远处，因而对STM计算的蒸发场强偏高. 关键词：     

石墨单晶表面原子的扫描隧道显微象

扫描隧道显微镜(STM)是近几年发展起来的一种直接观察物质表面微观结构的仪器.利用量子隧道效应,将极细的金属针尖接近样品表面扫描,从而获得样品表面的三维图象,可以反映表面原子排列和原子形态.图1是我们设计制造的扫描隧道显微镜原理图.采用压电陶瓷管P作为x,y和z方向的三维扫描器件.管表面等分为相邻90°的四个电极,针尖T固定在其中的一个电极上.尖端曲率半径为100nm左右的金属针尖,可用化学腐蚀法制备.两对电极上施加扫描电压时,针尖便在垂直于管轴z的x-y方向扫描,而z方向的高低变化则由加在内管壁上的电     

基于X射线掠射法的纳米薄膜厚度计量与量值溯源研究

为了实现纳米薄膜厚度的高精度计量,研制了可供台阶仪、扫描探针显微镜等接触测量的纳米薄膜样片,研究了X射线掠射法测量该纳米薄膜样片厚度的基本原理和计算方法,导出了基于Kiessig厚度干涉条纹计算膜层厚度的线性拟合公式,并提出了一种可溯源至单晶硅原子晶格间距和角度计量标准的纳米膜厚量值溯源方法,同时给出了相应的不确定度评定方法.实验证明:该纳米薄膜厚度H测量相对扩展不确定度达到U=0.3 nm+1.5%H,包含因子k=2.从而建立了一套纳米薄膜厚度计量方法和溯源体系.     

扫描探针显微学中的云纹方法

在扫描探针显微镜（SPM）的扫描过程中，由SPM的扫描线与物质表面周期性晶格结构进行干 涉可以形成纳米云纹图像.采用高取向热解石墨（HOPG）和云母作为试件，分别对扫描隧道 显微镜（STM）和原子力显微镜（AFM）云纹进行了研究，实验结果与理论分析完全一致.SPM 纳米云纹法在纳米测量和表征方面具有较大的应用前景. 关键词： 云纹 SPM 晶格栅线 纳米测量     

X-波段电子自旋成象

报道了自行设计研制的X-波段ESR成象装置并用之对典型样品作了ESR成象测定;用解卷积和分析图象重建中卷积滤波法对自旋样品体系进行了二维的图象重建,获取了能反映真实自旋分布的二维自旋密度图象.     

基于原子操纵技术的人工量子结构研究

扫描隧道显微镜原子操纵技术是指利用扫描探针在特定材料表面以晶格为步长搬运单个原子或分子的技术.它是纳米尺度量子物理与器件研究领域一种独特而有力的研究手段.利用这种手段,人们能够以原子或分子为单元构筑某些常规生长或微加工方法难以制备的人工量子结构,通过对格点原子、晶格尺寸、对称性、周期性的高度控制,实现对局域电子态、自旋序、以及能带拓扑特性等量子效应的设计与调控.原子操纵技术与超快测量及自动控制技术的结合,使得人们能够进一步研究原子级精准的量子器件,因而该技术成为探索未来器件新机理、新工艺的重要工具.本文首先简介原子操纵方法的发展过程和技术要点,然后分别介绍人工电子晶格、半导体表面人工量子点、磁性人工量子结构、人工结构中的信息存储与逻辑运算、单原子精度原型器件等方面的最新研究进展,以及单原子刻蚀和自动原子操纵等方面的技术进展,最后总结并展望原子操纵技术的应用前景和发展趋势.     

多光子成象术中深层图象损耗恢复的研究

本文在分析混浊介质对共焦三维扫描图象衰减的基础上,建立了多光子激发荧光扫描的深层图象恢复的数学模型.依照此模型对深层图象进行依赖组织光学参量的恢复,并给出了猪表皮三维扫描成象的恢复图象.     

STM analysis of triosmium carbonyl cluster adsorption at HOPG

The study of metallic carbonyl clusters as precursors in tailoring the heterogeneous metal catalysts has been of great importance. The catalytic nature of the adsorbed clusters in thin film form depends on the chemical properties of the substrate used. The metal-support interaction will determine various properties such as the surface morphology, adsorption features and the structural orientations. We report a scanning tunneling microscopy (STM) study of an osmium carbonyl cluster (Os₃(CO)₁₁(NCCH₃)) adsorbed on highly oriented pyrolytic graphite (HOPG). STM measurements showed that the osmium carbonyl cluster interacts with HOPG in such a way that it adsorbs on the basal plane showing regular lattice structure, whereas the axial planes of the HOPG surface shows no ordered structure. The regular cluster lattice structure of the carbonyl cluster on the basal plane of the graphite has lattice parameters of a=1.4 nm and b=1.5 nm. We believe that the regular orientation of the cluster indicates a monolayer adsorption of the cluster on the graphite basal planes. Scanning tunneling spectroscopy (STS) measurements also indicated an insulating behavior for the cluster molecules on HOPG, with a significant energy gap value of ca. 300 mV. The cluster interaction at the active sites, i.e. axial planes of the graphite, was also observed by in situ STM measurements.     

Two-dimensional self-assembly of esters with different configurations at the liquid-solid interface

Self-assembled monolayers of hexadecyl palmitate (HP) and 3,3′-thiodipropionic acid di-n-octadecyl ester (TADE) physisorbed on highly oriented pyrolytic graphite (HOPG) are investigated using scanning tunneling microscope (STM) and computer simulation. Both molecules form alkane-like linear shapes to maximize the interactions with substrate when they adsorb on HOPG surface. The HP molecules self-assemble into lamellae with the chain-trough angle of 48°, which is the result of a shifting 3/2 units from the adjacent molecule in a lamella. Based on the simulation insights combined with STM images, we confirm that a perpendicular orientation appears in which the HP molecular backbone is rotated 90° with respect to the substrate such that the carbonyl points away from the HOPG surface. TADE molecules form three kinds of configurations with chain-trough angles of 90°, 72° and 60° by shifting 0, 1/2 and 1 units from their adjacent molecules, respectively. The bright stripes in STM images reveal the electron density distribution of the part between two ester groups. The energy differences of three TADE adsorption configurations by molecular mechanics (MM) simulation are used to explain the structural coexistence phenomenon. It is also shown that lattice match between alkyl chain of molecules and HOPG substrate could change molecular conformation upon self-assembly.     

Simultaneous observation of the triangular and honeycomb structures on highly oriented pyrolytic graphite at room temperature: An STM study

Scanning tunneling microscopy (STM) was used to study the surface structures of dry-prepared and di-chloroethane-treated HOPG samples. Both triangular and honeycomb structures were simultaneously observed with the same tip at room temperature around a strand (grain boundary) on the HOPG surface. This observation did not support the tip effect in STM imaging explanation for HOPG in literature. A general layer-sliding model was utilized to explain the experimental results: sliding of the HOPG topmost layer was used to explain the origins of the triangular and honeycomb structures, and molecule intercalation into inter-layer spacing between the first and second layers of HOPG induced inhomogeneous deformation of the HOPG topmost layer that accordingly generated the Moiré patterns of the HOPG sample in di-chloroethane.     

Insight into STM image contrast of n-tetradecane and n-hexadecane molecules on highly oriented pyrolytic graphite

Two-dimensional ordered patterns of n-tetradecane (n-C₁₄H₃₀) and n-hexadecane (n-C₁₆H₃₄) molecules at liquid/graphite interface have been directly imaged using scanning tunneling microscope (STM) under ambient conditions. STM images reveal that the two different kinds of molecules self-organize into ordered lamellar structures in which alkane chains of the molecules extend along one of three equivalent lattice axes of highly oriented pyrolytic graphite (HOPG) basal plane. For n-C₁₄H₃₀ molecules, the molecular axes are observed to tilt by 60° with respect to inter-lamellar trough lines and the carbon backbones of the alkane chains are perpendicular to the HOPG basal plane in an all-trans conformation. However, for n-C₁₆H₃₄ molecules, the molecular axes are perpendicular to lamellar borders (90°) and the planes of the all-trans carbon skeletons are parallel to the graphite basal plane. The results clearly indicate that outmost hydrogen atoms of the alkane chains dominate atom-scaled features of the STM images. That is, in the case of long-chain alkane molecules, topographic effects dominantly determine STM image contrast of the methylene regions of the alkane chains that are adsorbed on HOPG.     

扫描隧道显微镜纳米云纹法的实验研究

提出了应用扫描隧道显微镜(STM)纳米云纹法测量面内位移的原理。测量中,把扫描隧道显微镜的探针扫描线作为参考栅,把物质原子晶格栅结构作为试件栅,对这两组栅线干涉形成的云纹进行了纳米级变形测量。对扫描隧道显微镜纳米云纹的形成原理及测量方法进行了详尽的讨论,并运用该方法对高定向裂解石墨(HOPG)的纳米级变形虚应变进行了测量研究,得到了随扫描范围变化的虚应变场,并与理论值进行了比较。     

Observation of the Damage on HOPG Surface Induced by Ar+8 Ions

Highly oriented pyrolytic graphite (HOPG) samples were bombarded by Ar+8 ions with energy range from 10.1 to 112MeV. After bombardment the sample surfaces were observed using a STM and NanoScope. The resultS show that the energetic ion could cause observable praotrusionlike damage on the HOPG surface.The relationship betWeen damage and energy loss, and the possible mechanism of damage process are discussed.     

Ar+8轰击石墨表面损伤的扫描隧道显微镜观测研究

报道了用10—112MeV能量的Ar+8离子轰击高定向石墨造成损伤的原子水平观测结果,给出了损伤形貌、损伤大小和损伤数密度.讨论了损伤与表面核能损的关系及损伤过程的可能机制.     

Highly oriented pyrolitic graphite anomalous structures and fullerenes self-assembly

Scanning tunneling microscopy (STM) was used to look for unusual self-structures on highly oriented pyrolitic graphite (HOPG) that can mimic fullerenes assemblies. HOPG features that may be taken as C₆₀ molecular structures were found on this surface. The HOPG self-structures have been presented earlier as anomalies of the bare HOPG surface in the literature. The experimental results are in agreement with earlier STM reports on bare and modified HOPG.     

Palladium nano-clusters grown on prestructured HOPG substrates

The growth of Palladium nano-clusters prepared by atomic beam deposition on prestructured highly oriented pyrolytic graphite (HOPG) surfaces has been investigated by means of scanning tunnelling microscopy (STM). Preformed nanosized pits created on the HOPG surfaces are used as localized pinning sites for Pd cluster nucleation and growth at room temperature. We succeeded in obtaining Pd clusters of nanometric size and with rather sharp size distributions. A systematic morphological study conducted by STM reveals a linear dependence between the height and the diameter of the Pd nanostructures. Finally, Pd nano-clusters stabilized on prestructured HOPG surfaces were found to be active catalysts in the Heck cross-coupling reaction.     

Folding and cracking of graphene oxide sheets upon deposition

Graphene Oxide (GO) sheets, suspended in an aqueous solution, were deposited on freshly cleaved highly oriented pyrolytic graphite (HOPG) and studied using Raman spectroscopy, atomic force microscopy (AFM) and scanning tunneling microscopy (STM). AFM phase imaging shows a distinct contrast between GO and the underlying HOPG substrate. Raman spectroscopy clearly showed the presence of GO sheets on the top of HOPG substrate. The AFM and STM images also reveal wrinkling, folding, and tearing of individual GO sheets after depositing onto an HOPG substrate. We have also observed a distinct cracking of a GO sheet after folding. We attribute this new cracking phenomenon to a weakening of C–C bonds during the oxidation of a graphene sheet.