Scanning Tunneling Microscopy of the Ytterbium Nanofilm Surface and Layers of Oxygen Molecules Adsorbed on It

Technical Physics - The surfaces of Yb–Si(111) and O–Yb–Si(111) structures (with a thickness of ytterbium nanofilms of 16 monolayers (6.08 nm)) have been investigated for the...     

原子力与光子扫描隧道组合显微镜

介绍了超高分辨光于扫描隧遭显微镜（PSTM）的计冗历程,为解决第一代（单光束照明）光千扫捕隧逼显傲镜中存在人为假象和样品光学图像与形貌图像难于分离两个难题,用“对称双光束照明方法消假象,用原子力与光子扫描隧道组合显微镜（AF／PSTM）图像分解方法分离样品光学透过率、折射率与形貌图像。研制成功新一代原子力与光子扫描隧道组合显微镜（AF／PSTM）样机。该样机在一次扫描中已获得两幅原子力显微镜图像（形貌与相位）和两幅光学图像（透过率和折射率）,有效地减少了假象,分解了样品光学折射率、透过率与形貌图像。     

Probing Single Nanometer-scale Particles with Scanning Tunneling Microscopy and Spectroscopies

Scanning tunneling microscopy can be used to isolate single particles on surfaces for further study. Local optical and electronic properties coupled with topographic information collected by the scanning tunneling microscope (STM) give insight into the intrinsic properties of the species under study. Since each spectroscopic measurement is done on a single particle, each sample is monodisperse, regardless of the degree of heterogeneity of the original preparation. We illustrate this with three example systems – a metal cluster of known atomic structure, metal nanoparticles dispersed from colloid suspensions, and metallocarbohedrenes (Met-Cars) deposited with other reaction products. Au and Ag nanoparticles were imaged using a photon emission STM. The threshold voltage, the lowest bias voltage at which photons are produced, was determined for Au nanoparticles. Electronic spectra of small clusters of Ni atoms on MoS₂ were recorded. Preliminary images of Zr-based Met-Car-containing soot were obtained on Au and MoS₂ substrates and partial electronic spectra were recorded of these possible Met-Car particles.     

Graphene/Rh(111) Structure Studied Using In-Situ Scanning Tunneling Microscopy

Scanning tunnel microscopy(STM)is performed to verify if an Rh 'nails' structure is formed accompanying the graphene growing during chemical vapor deposition.A structure of a graphene island in an Rh vacancy island is used as the start.While the graphene island is removed by oxygenation,the variations of the Rh vacancy island are imaged with an in-situ high-temperature STM.By fitting with our model and calculations,we conclude that the best fit is obtained for 0%Rh,i.e.,for the complete absence of nails below graphene on Rh(111).That is,when graphene is formed on Rh(111),the substrate remains flat and does not develop a supporting nail structure.     

光子扫描隧道显微镜的探测场

通过修改光子扫描隧道显微镜探测场的计算模型，推导出比较符合实际的探测场及透射系数的计算公式，并利用这一新计算公式在微机上进行了模拟计算，得到了一些过去未曾发现的现象，对光子扫描隧道显微镜的实际探测具有一定的指导意义。     

利用扫描隧道显微镜在溶液中直接观测过渡族金属硫属化合物

本文利用自制的溶液扫描隧道显微镜在溶液环境下直接观测到TiSe₂、MoTe₂和TaS₂样品的原子分辨率图像. 通过将单晶样品在溶液中直接解理,可以保护解理过的新鲜样品表面在几个小时内不会被严重污染. 利用自行搭建的溶液扫描隧道显微镜,首先观察到了TiSe₂活泼样品的原子分辨率图像,并观察到了TiSe₂表面所特有的点缺陷和三角形缺陷结构. 此外,还观察到了MoTe₂的原子分辨率超结构和TaS₂表面的电荷密度波结构. 结果表明：在室温、溶液环境下能更高效的研究过渡族金属硫属化合物等活泼样品的表面电子态结构,同样适用于溶液环境下的电催化和电化学研究.     

利用扫描隧道显微镜表征和操纵单分子

扫描隧道显微镜（STM）提供给我们一种表征单分子的局域物理和化学特性的特殊方法，甚至还能帮助我们操纵单分子以构造分子尺度的新型器件。本文中我们采用了两种新型STM技术分别来表征封装在富勒烯笼里面的金属原子和构造一种具有较强Kondo效应的分子器件。空间dI/dV映像谱被用来探索单个Dy@C82分子中能量分辨的金属-笼杂化态，揭示了有关Dy原子在碳笼中的空间位置和Dy-碳笼之间相互作用的重要信息。我们也通过控制STM针尖诱导的高电压脉冲来诱导CoPc分子的边缘脱氢化，从而改变了这个分子在Au(111)表面的吸附构型，导致吸附在Au表面的完整CoPc分子所不具备的Kondo效应产生。     

Resolution of Internal Total ReflectionScanning Near-field Optical Microscopy

In this paper, the probe-sample interaction equation based on Mie's scattering theory is derived, and the resolution of scanning near field optical microscopy is calculated numerically. The results show that the offset of far-field component to near-field component in total field plays an important role in the resolution and the size of samples also has influence on resolution.     

Resolution of Internal Total Reflection Scanning Near-field Optical Microscopy

In this paper, the probe-sample interaction equation based on Mie′s scattering theory is derived, and the resolution of scanning near field optical microscopy is calculated numerically. The results show that the offset of far-field component to near-field component in total field plays an important role in the resolution and the size of samples also has influence on resolution.     

Near-Field Scanning Optical Microscopy Combined with a Tapping Mode Atomic Force Microscope

Tapping mode atomic force microscopy is used to control the tip-sample distance in near field scanning optical microscopy (NSOM), which gives both topographic and near-field images simultaneously. The evanescent waves are scattered by a vibrating silicon-nitride tip in the proximity of sample surfaces and are detected through a microscope objective. This NSOM allows the observation of opaque samples with reflection illumination. A glass grating of 1-μm pitch and an InP grating of 0.5-μm pitch are observed with a lateral resolution of 100 nm.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27-29, Saitama, Japan     

Magnification Effects in Scanning Tunneling Microscopy: the Role of Surface Radicals

Journal of Experimental and Theoretical Physics - Scanning tunneling microscopy (STM) is a fundamental tool for determination of the surface atomic structure. However, the interpretation of high...     

Simulation of Properties of Images with Atomic Resolution in a Scanning Probe Microscope

A method for simulation of images in a scanning probe microscope (SPM) using simultaneous wavelet transform and median filtering is proposed. The wavelet transform with the fourth-order Daubechies kernel is used. Such a transform makes it possible to select details of different scales in the SPM image and, hence, study fractal properties of surfaces. Simulation is used to show that ultrahigh (atomic) resolution is possible in SPM provided that the size of the contact region in the probe–sample system is significantly greater than atomic size and the lattice atoms are randomly distributed. Contrast inversion in the SPM images in the multiscan mode is interpreted.     

Charge Density Wave States in 2H-MoTe_2 Revealed by Scanning Tunneling Microscopy

2H-and 1T′-phase monolayer MoTe_2 films on highly oriented pyrolytic graphite are studied using scanning tunneling microscopy and spectroscopy(STM/STS).The phase transition of MoTe_2 can be controlled by a postgrowth annealing process,and the intermediate state during the phase transition is directly observed by STM.For 2H-MoTe2,inversion domain boundaries are presented as bright lines at high sample bias,but as dark lines at lower sample bias.The dI/dV mappings reveal the distinct distributions of electronic states between domain boundaries and interiors of domains.It sihould be noted that a 2×2 periodic structure is clearlfy discernable inside the domains,where the STS measurement shows a small dip of size～150 meV at the vicinity of the Fermi level,indicating that the 2×2 periodic structure may be an incommensurate charge density wave.Moreover,a4×4 periodic structure appears in 2H-MoTe_2 grown at a higher substrate temperature.     

一体型平行弹簧扫描隧道显微镜

描述了一种新结构形式的扫描隧道显微镜系统。该系统使用一体型平行弹簧和压电致动元件作为精密二维位置控制器件，使得ｘ轴和ｙ轴间的位移干扰变得极其微小。控制ｚ轴位移及试件与探针间距的压电致动元件是以悬挂方式固定在一体型平行弹簧上的，因此，对ｚ轴的位移干扰亦忽略。     

Theoretical Analyses on the Resolution of Collection Mode Scanning Near-Field Optical Microscopy

Numerical simulations have been carried out in the framework of waveguide theory to model collection mode scanning near-field optical microscopy (SNOM). The theoretical model includes the optical fiber end and describes the metal coated aperture on the probe tip. The developed formalism goes beyond the existing Bethe-Bouwkamp theories for electromagnetic transmission of subwavelength apertures. The finite coating and optical fiber end are now taken into account. The new features enable us to simulate the near-field probes that are widely used in the collection mode SNOM. The emphases of the numerical analyses have been mainly on the resolution mechanism of the microscopy. Influence on the resolution from important parameters of the probe tips, such as the size of the apertures and the probe-sample distance, is extensively studied. The resolution dependence has been analyzed in the light of the near-field coupling efficiency of the probe tip. An optimum tip size has been found which is balanced between the significant signal transmission and the resolution of the device.