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Sample records for scanning tunneling spectra

  1. Unconventional scanning tunneling conductance spectra for graphene

    Saha, K.; Paul, I.; Sengupta, K.

    2009-01-01

    We compute the tunneling conductance of graphene as measured by a scanning tunneling microscope (STM) with a normal/superconducting tip. We demonstrate that for undoped graphene with zero Fermi energy, the first derivative of the tunneling conductance with respect to the applied voltage is proportional to the density of states of the STM tip. We also show that the shape of the STM spectra for graphene doped with impurities depends qualitatively on the position of the impurity atom in the grap...

  2. Importance of quantum correction for the quantitative simulation of photoexcited scanning tunneling spectra of semiconductor surfaces

    Schnedler, M.; Dunin-Borkowski, R. E.; Ebert, Ph.

    2016-05-01

    Photoexcited scanning tunneling spectroscopy is a promising technique for the determination of carrier concentrations, surface photovoltages, and potentials of semiconductors with atomic spatial resolution. However, extraction of the desired quantities requires computation of the electrostatic potential induced by the proximity of the tip and the tunnel current. This calculation is based on an accurate solution of the Poisson as well as the continuity equations for the tip-vacuum-semiconductor system. For this purpose, the carrier current densities are modeled by classical drift and diffusion equations. However, for small tip radii and highly doped materials, the drift and diffusion transport model significantly overestimates a semiconductor's carrier concentration near the surface, making the quantification of physical properties impossible. In this paper, we apply quantum correction to the drift and diffusion model, in order to account for the so-called quantum compressibility, i.e., reduced compressibility of the carrier gas due to the Pauli principle, in the region of the tip-induced band bending. We compare carrier concentrations, potentials, and tunnel currents derived with and without quantum correction for GaN (10 1 ¯0 ) and GaAs(110) surfaces to demonstrate its necessity.

  3. Tunneling spectra and superconducting gaps observed by scanning tunneling microscopy near the grain boundaries of FeSe0.3Te0.7 films

    Highlights: •We prepared FeSe0.3Te0.7 films with two orientations on the same MgO substrate by the pulsed laser deposition technique. •The STM tunneling spectra in the grains with two orientations and boundary between them. •Different superconducting gaps were observed in different orientations and their boundary. -- Abstract: We used scanning tunneling microscopy (STM) to study the tunneling spectra of FeSe0.3Te0.7 films with two orientations of the ab-planes and a connection ramp between them. We discovered that by pulsed laser deposition (PLD) method, the a- and b-axis of the FeSe0.3Te0.7 film deposited on an Ar-ion-milled magnesium oxide (MgO) substrate were rotated 45° with respect to those of MgO, whereas the a- and b-axis of the film grown on a pristine MgO substrate were parallel to those of MgO. With photolithography and this technique, we can prepare FeSe0.3Te0.7 films with two orientations on the same MgO substrate so that the connection between them forms a ramp at an angle of about 25° to the substrate plane. In the planar region, for either the 0° or 45° orientation, we observed tunneling spectra with a superconducting gap of about 5 meV and 1.78 meV, respectively. However, a much larger gap at about 18 meV was observed in the ramp region. Furthermore, we observed a small zero-bias conductance peak (ZBCP) inside the large gap at T = 4.3 K. The ZBCP becomes smaller with increasing temperature and disappeared at temperature above 7 K

  4. Tip induced doping effects in local tunnel spectra of graphene

    Choudhury, Shyam K.; Gupta, Anjan K.

    2010-01-01

    We report on tip induced doping in local tunnel spectra of single layer graphene (SLG) with tunable back-gate using room temperature scanning tunneling microscopy and spectroscopy (STM/S). The SLG samples, prepared on silicon dioxide surface by exfoliation method and verified by Raman spectra, show atomically resolved honeycomb lattice. Local tunnel spectra show two minima with a clear evolution in the position of both with doping by the back gate. A similar variation in spectra is also obser...

  5. Introduction to scanning tunneling microscopy

    Chen, C Julian

    2008-01-01

    The scanning tunneling and the atomic force microscope, both capable of imaging individual atoms, were crowned with the Physics Nobel Prize in 1986, and are the cornerstones of nanotechnology today. This is a thoroughly updated version of this 'bible' in the field.

  6. Scanning Tunneling Optical Resonance Microscopy

    Bailey, Sheila; Wilt, Dave; Raffaelle, Ryne; Gennett, Tom; Tin, Padetha; Lau, Janice; Castro, Stephanie; Jenkins, Philip; Scheiman, Dave

    2003-01-01

    Scanning tunneling optical resonance microscopy (STORM) is a method, now undergoing development, for measuring optoelectronic properties of materials and devices on the nanoscale by means of a combination of (1) traditional scanning tunneling microscopy (STM) with (2) tunable laser spectroscopy. In STORM, an STM tip probing a semiconductor is illuminated with modulated light at a wavelength in the visible-to-near-infrared range and the resulting photoenhancement of the tunneling current is measured as a function of the illuminating wavelength. The photoenhancement of tunneling current occurs when the laser photon energy is sufficient to excite charge carriers into the conduction band of the semiconductor. Figure 1 schematically depicts a proposed STORM apparatus. The light for illuminating the semiconductor specimen at the STM would be generated by a ring laser that would be tunable across the wavelength range of interest. The laser beam would be chopped by an achromatic liquid-crystal modulator. A polarization-maintaining optical fiber would couple the light to the tip/sample junction of a commercial STM. An STM can be operated in one of two modes: constant height or constant current. A STORM apparatus would be operated in the constant-current mode, in which the height of the tip relative to the specimen would be varied in order to keep the tunneling current constant. In this mode, a feedback control circuit adjusts the voltage applied to a piezoelectric actuator in the STM that adjusts the height of the STM tip to keep the tunneling current constant. The exponential relationship between the tunneling current and tip-to-sample distance makes it relatively easy to implement this mode of operation. The choice of method by which the photoenhanced portion of the tunneling current would be measured depends on choice of the frequency at which the input illumination would be modulated (chopped). If the frequency of modulation were low enough (typically < 10 Hz) that the

  7. Seismic scanning tunneling macroscope - Theory

    Schuster, Gerard T.

    2012-09-01

    We propose a seismic scanning tunneling macroscope (SSTM) that can detect the presence of sub-wavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the point scatterer is in the near-field region; if the sub-wavelength scatterer is a spherical impedance discontinuity then the resolution will also be limited by the radius of the sphere. Therefore, superresolution imaging can be achieved as the scatterer approaches the source. This is analogous to an optical scanning tunneling microscope that has sub-wavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by imaging of near-field seismic energy.

  8. Role of Inelastic Tunneling through the Barrier in Scanning Tunneling Microscope Experiments on Cuprates

    Pilgram, S.; T. M. Rice; Sigrist, M.

    2006-01-01

    The tunneling path between the CuO2-layers in cuprate superconductors and a scanning tunneling microscope tip passes through a barrier made from other oxide layers. This opens up the possibility that inelastic processes in the barrier contribute to the tunneling spectra. Such processes cause one or possibly more peaks in the second derivative current-voltage spectra displaced by phonon energies from the density of states singularity associated with superconductivity. Calculations of inelastic...

  9. Low-temperature scanning tunneling spectroscopy

    A scanning tunneling microscope (STM) was designed and built to operate at liquid helium temperature and was used to measure highly localized electron tunneling spectroscopy. Several instruments were built, all capable of operating in many different environments: air, vacuum, liquid helium and in a transfer gas. An adaptation of one particular design was made into an atomic force microscope capable of operating at low temperatures. Using a low temperature STM, three adsorbed molecular species (liquid crystals, sorbic acid, and carbon monoxide), deposited on a graphite substrate, have been imaged at 4.2K. The inelastic tunneling spectra of these adsorbates show strong peaks in dI/dV vs V curves at energies that correspond to known vibrational modes. The increase in conductance at the onset of inelastic tunneling was measured to be as high as 100 times. The spatial variation of the spectra was measured and was seen to change dramatically on the scale of angstroms, suggesting that individual molecular bonds could be measured. A theoretical model is presented to explain the contrast seen in the STM images of adsorbed molecules, thereby explaining why adsorbed molecules appear to be more conductive than the background. The microscope proved very useful for measuring the energy gap of high temperature superconductors. These materials often have submicron grain sizes. For LaSrCuO, YBaCuO, and BiCaSrCuO, the conductance curves showed a large energy gap suggesting a strongly coupled superconductor. The conductance curves also indicated that intergrain tunneling may occur and that the background conductance varied linearly with the applied voltage. The crystalline structure of Bi2Sr2CaCu2O8+δ was imaged by an STM operating in air and in ultra-high vacuum

  10. Fiber coupled ultrafast scanning tunneling microscope

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1997-01-01

    We report on a scanning tunneling microscope with a photoconductive gate in the tunneling current circuit. The tunneling tip is attached to a coplanar transmission line with an integrated photoconductive switch. The switch is illuminated through a fiber which is rigidly attached to the switch...

  11. Fiber coupled ultrafast scanning tunneling microscope

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1997-01-01

    We report on a scanning tunneling microscope with a photoconductive gate in the tunneling current circuit. The tunneling tip is attached to a coplanar transmission line with an integrated photoconductive switch. The switch is illuminated through a fiber which is rigidly attached to the switch substrate. By using a firmly attached fiber we achieve an excellent reproducibility and unconstrained positioning of the tip. We observe a transient signal with 2.9 ps pulse width in tunneling mode and 5...

  12. Scanning tunneling microscopy of dye thin films

    The Rhodamine 6G films on a metal and a semiconductor substrates were studied by scanning tunneling microscopy and spectral ellipsometry techniques. Scanning tunneling microscopy of dye on a metal substrate allowed obtaining interlayer surface profile with atomic spatial resolution 0.08 nm

  13. Radio-frequency scanning tunnelling microscopy

    Kemiktarak, U.; Ndukum, T.; Schwab, K. C.; Ekinci, K. L.

    2007-01-01

    The scanning tunnelling microscope (STM) relies on localized electron tunnelling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. In the 25-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical systems -— ranging from semiconductors to superconductors to atomic and molecular nanosystems. A severe limitation in scanning tunnelling microscopy is the low temporal resolution, originating from the diminishe...

  14. Scanning Tunneling Microscope For Use In Vacuum

    Abel, Phillip B.

    1993-01-01

    Scanning tunneling microscope with subangstrom resolution developed to study surface structures. Although instrument used in air, designed especially for use in vacuum. Scanning head is assembly of small, mostly rigid components made of low-outgassing materials. Includes coarse-positioning mechanical-translation stage, on which specimen mounted by use of standard mounting stub. Tunneling tip mounted on piezoelectric fine-positioning tube. Application of suitable voltages to electrodes on piezoelectric tube controls scan of tunneling tip across surface of specimen. Electronic subsystem generates scanning voltages and collects data.

  15. Investigation into scanning tunnelling luminescence microscopy

    Manson-Smith, S K

    2001-01-01

    This work reports on the development of a scanning tunnelling luminescence (STL) microscope and its application to the study of Ill-nitride semiconductor materials used in the production of light emitting devices. STL microscopy is a technique which uses the high resolution topographic imaging capabilities of the scanning tunnelling microscope (STM) to generate high resolution luminescence images. The STM tunnelling current acts as a highly localised source of electrons (or holes) which generates luminescence in certain materials. Light generated at the STM tunnelling junction is collected concurrently with the height variation of the tunnelling probe as it is scanned across a sample surface, producing simultaneous topographic and luminescence images. Due to the very localised excitation source, high resolution luminescence images can be obtained. Spectroscopic resolution can be obtained by using filters. Additionally, the variation of luminescence intensity with tunnel current and with bias voltage can provi...

  16. Fluctuation Dominated Josephson Tunneling with a Scanning Tunneling Microscope

    Naaman, O.; Teizer, W.; Dynes, R. C.

    2001-01-01

    We demonstrate Josephson tunneling in vacuum tunnel junctions formed between a superconducting scanning tunneling microscope tip and a Pb film, for junction resistances in the range 50-300 k$\\Omega$. We show that the superconducting phase dynamics is dominated by thermal fluctuations, and that the Josephson current appears as a peak centered at small finite voltages. In the presence of microwave fields (f=15.0 GHz) the peak decreases in magnitude and shifts to higher voltages with increasing ...

  17. Thermovoltages in vacuum tunneling investigated by scanning tunneling microscopy

    Hoffmann, D. H.; Rettenberger, Armin; Grand, Jean Yves; Läuger, K.; Leiderer, Paul; Dransfeld, Klaus; Möller, Rolf

    1995-01-01

    By heating the tunneling tip of a scanning tunneling microscope the thermoelectric properties of a variable vacuum barrier have been investigated. The lateral variation of the observed thermovoltage will be discussed for polycrystalline gold, stepped surfaces of silver, as well as for copper islands on silver.

  18. Investigation into scanning tunnelling luminescence microscopy

    This work reports on the development of a scanning tunnelling luminescence (STL) microscope and its application to the study of Ill-nitride semiconductor materials used in the production of light emitting devices. STL microscopy is a technique which uses the high resolution topographic imaging capabilities of the scanning tunnelling microscope (STM) to generate high resolution luminescence images. The STM tunnelling current acts as a highly localised source of electrons (or holes) which generates luminescence in certain materials. Light generated at the STM tunnelling junction is collected concurrently with the height variation of the tunnelling probe as it is scanned across a sample surface, producing simultaneous topographic and luminescence images. Due to the very localised excitation source, high resolution luminescence images can be obtained. Spectroscopic resolution can be obtained by using filters. Additionally, the variation of luminescence intensity with tunnel current and with bias voltage can provide information on recombination processes and material properties. The design and construction of a scanning tunnelling luminescence microscope is described in detail. Operating under ambient conditions, the microscope has several novel features, including a new type of miniature inertial slider-based approach motor, large solid-angle light collection optical arrangement and a tip-height regulation system which requires the minimum of operator input. (author)

  19. A Student-Built Scanning Tunneling Microscope

    Ekkens, Tom

    2015-01-01

    Many introductory and nanotechnology textbooks discuss the operation of various microscopes including atomic force (AFM), scanning tunneling (STM), and scanning electron microscopes (SEM). In a nanotechnology laboratory class, students frequently utilize microscopes to obtain data without a thought about the detailed operation of the tool itself.…

  20. Towards high-speed scanning tunneling microscopy

    Tabak, Femke Chantal

    2013-01-01

    In this thesis, two routes towards high-speed scanning tunneling microscopy (STM) are described. The first possibility for high-speed scanning that is discussed is the use of MEMS (Micro-Electro Mechanical Systems) devices as high-speed add-ons in STM microscopes. The functionality of these devices

  1. Scanning tunneling spectroscopy of Pb thin films

    Becker, Michael

    2010-12-13

    The present thesis deals with the electronic structure, work function and single-atom contact conductance of Pb thin films, investigated with a low-temperature scanning tunneling microscope. The electronic structure of Pb(111) thin films on Ag(111) surfaces is investigated using scanning tunneling spectroscopy (STS). Quantum size effects, in particular, quantum well states (QWSs), play a crucial role in the electronic and physical properties of these films. Quantitative analysis of the spectra yields the QWS energies as a function of film thickness, the Pb bulk-band dispersion in {gamma}-L direction, scattering phase shifts at the Pb/Ag interface and vacuum barrier as well as the lifetime broadening at anti {gamma}. The work function {phi} is an important property of surfaces, which influences catalytic reactivity and charge injection at interfaces. It controls the availability of charge carriers in front of a surface. Modifying {phi} has been achieved by deposition of metals and molecules. For investigating {phi} at the atomic scale, scanning tunneling microscopy (STM) has become a widely used technique. STM measures an apparent barrier height {phi}{sub a}, which is commonly related to the sample work function {phi}{sub s} by: {phi}{sub a}=({phi}{sub s}+{phi}{sub t}- vertical stroke eV vertical stroke)/2, with {phi}{sub t} the work function of the tunneling tip, V the applied tunneling bias voltage, and -e the electron charge. Hence, the effect of the finite voltage in STM on {phi}{sub a} is assumed to be linear and the comparison of {phi}{sub a} measured at different surface sites is assumed to yield quantitative information about work function differences. Here, the dependence of {phi}{sub a} on the Pb film thickness and applied bias voltage V is investigated. {phi}{sub a} is found to vary significantly with V. This bias dependence leads to drastic changes and even inversion of contrast in spatial maps of {phi}{sub a}, which are related to the QWSs in the Pb

  2. Tunneling spectra of graphene on copper unraveled

    Zhang, Xin; Stradi, Daniele; Liu, Lei;

    2016-01-01

    Scanning tunneling spectroscopy is often employed to study two-dimensional (2D) materials on conductive growth substrates, in order to gain information on the electronic structures of the 2D material-substrate systems, which can lead to insight into 2D material-substrate interactions, growth mech...

  3. Scanning tunneling microscope assembly, reactor, and system

    Tao, Feng; Salmeron, Miquel; Somorjai, Gabor A

    2014-11-18

    An embodiment of a scanning tunneling microscope (STM) reactor includes a pressure vessel, an STM assembly, and three spring coupling objects. The pressure vessel includes a sealable port, an interior, and an exterior. An embodiment of an STM system includes a vacuum chamber, an STM reactor, and three springs. The three springs couple the STM reactor to the vacuum chamber and are operable to suspend the scanning tunneling microscope reactor within the interior of the vacuum chamber during operation of the STM reactor. An embodiment of an STM assembly includes a coarse displacement arrangement, a piezoelectric fine displacement scanning tube coupled to the coarse displacement arrangement, and a receiver. The piezoelectric fine displacement scanning tube is coupled to the coarse displacement arrangement. The receiver is coupled to the piezoelectric scanning tube and is operable to receive a tip holder, and the tip holder is operable to receive a tip.

  4. Ultraviolet light emission from Si in a scanning tunneling microscope

    Schmidt, Patrick; Berndt, Richard; Vexler, Mikhail I.

    2007-01-01

    Ultraviolet and visible radiation is observed from the contacts of a scanning tunneling microscope with Si(100) and (111) wafers. This luminescence relies on the presence of hot electrons in silicon, which are supplied, at positive bias on n- and p-type samples, through the injection from the tip, or, at negative bias on p-samples, by Zener tunneling. Measured spectra reveal a contribution of direct optical transitions in Si bulk. The necessary holes well below the valence band edge are injec...

  5. Radio-frequency scanning tunnelling microscopy.

    Kemiktarak, U; Ndukum, T; Schwab, K C; Ekinci, K L

    2007-11-01

    The scanning tunnelling microscope (STM) relies on localized electron tunnelling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. In the 25-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical systems--ranging from semiconductors to superconductors to atomic and molecular nanosystems. A severe limitation in scanning tunnelling microscopy is the low temporal resolution, originating from the diminished high-frequency response of the tunnel current readout circuitry. Here we overcome this limitation by measuring the reflection from a resonant inductor-capacitor circuit in which the tunnel junction is embedded, and demonstrate electronic bandwidths as high as 10 MHz. This approximately 100-fold bandwidth improvement on the state of the art translates into fast surface topography as well as delicate measurements in mesoscopic electronics and mechanics. Broadband noise measurements across the tunnel junction using this radio-frequency STM have allowed us to perform thermometry at the nanometre scale. Furthermore, we have detected high-frequency mechanical motion with a sensitivity approaching approximately 15 fm Hz(-1/2). This sensitivity is on par with the highest available from nanoscale optical and electrical displacement detection techniques, and the radio-frequency STM is expected to be capable of quantum-limited position measurements. PMID:17972882

  6. Towards high-speed scanning tunneling microscopy

    Tabak, Femke Chantal

    2013-01-01

    In this thesis, two routes towards high-speed scanning tunneling microscopy (STM) are described. The first possibility for high-speed scanning that is discussed is the use of MEMS (Micro-Electro Mechanical Systems) devices as high-speed add-ons in STM microscopes. The functionality of these devices is shown using finite-element simulations, combined with measurements of their resonance frequency and actuation range. Tip deposition was done using EBID (Electron-Beam Induced Deposition) which a...

  7. Scanning Tunneling Spectroscope Use in Electrocatalysis Testing

    Turid Knutsen

    2010-06-01

    Full Text Available The relationship between the electrocatalytic properties of an electrode and its ability to transfer electrons between the electrode and a metallic tip in a scanning tunneling microscope (STM is investigated. The alkaline oxygen evolution reaction (OER was used as a test reaction with four different metallic glasses, Ni78Si8B14, Ni70Mo20Si5B5, Ni58Co20Si10B12, and Ni25Co50Si15B10, as electrodes. The electrocatalytic properties of the electrodes were determined. The electrode surfaces were then investigated with an STM. A clear relationship between the catalytic activity of an electrode toward the OER and its tunneling characteristics was found. The use of a scanning tunneling spectroscope (STS in electrocatalytic testing may increase the efficiency of the optimization of electrochemical processes.

  8. Spectroscopy of Light Emission from a Scanning Tunneling Microscope in Air

    Péchou, R.; Coratger, R.; Girardin, C.; Ajustron, F.; Beauvillain, J.

    1996-01-01

    Light emission has been detected at the tip-sample junction of a Scanning Tunneling Microscope (S.T.M.) in air on noble metallic surfaces. A spectroscopic study of emitted photons for Au-Au and PtIr-Au tunneling junctions is presented. The general aspect of the spectra depends on the materials used in the junctions; a study of the spectra as a function of tunneling current and surface bias voltage reveals similar and reproducible characteristics.

  9. Observation of negative differential resistance in tunneling spectroscopy of MoS2 with a scanning tunneling microscope

    Youngquist, M. G.; Baldeschwieler, J D

    1991-01-01

    A scanning tunneling microscope has been used for imaging and tunneling spectroscopy of 2Hb–MoS2 in ultrahigh vacuum. Atom-resolved images obtained in three distinct imaging modes–measuring z at constant current, barrier height at constant current, and current at constant z–are presented. Current–voltage (I–V) tunneling spectra reveal the occasional presence of negative differential resistance. Possible origins of the effect are discussed. Convolution of the sample energy density of states (D...

  10. Traceable long range scanning tunneling microscopy

    2008-01-01

    Dimensionally correct and directly traceable measurement is not feasible with conventional scanning tunneling microscopy (STMs) due to severe hysteresis and non-linearity of the commonly applied piezo tube scanners and the very short range.By integrating a custom made probing system based on tunneling current measurement into a commercially available and laser-interferometrically position controlled positioning system, an STM with a principal measuring range of 25 mm×25 mm×5 mm and traceable position measurement has been set-up and tested.

  11. Scanning tunneling microscopy II further applications and related scanning techniques

    Güntherodt, Hans-Joachim

    1995-01-01

    Scanning Tunneling Microscopy II, like its predecessor, presents detailed and comprehensive accounts of the basic principles and broad range of applications of STM and related scanning probe techniques. The applications discussed in this volume come predominantly from the fields of electrochemistry and biology. In contrast to those described in STM I, these studies may be performed in air and in liquids. The extensions of the basic technique to map other interactions are described in chapters on scanning force microscopy, magnetic force microscopy, and scanning near-field optical microscopy, together with a survey of other related techniques. Also described here is the use of a scanning proximal probe for surface modification. Together, the two volumes give a comprehensive account of experimental aspects of STM. They provide essential reading and reference material for all students and researchers involved in this field. In this second edition the text has been updated and new methods are discussed.

  12. Scanning tunneling microscopy II further applications and related scanning techniques

    Güntherodt, Hans-Joachim

    1992-01-01

    Scanning Tunneling Microscopy II, like its predecessor, presents detailed and comprehensive accounts of the basic principles and broad range of applications of STM and related scanning probe techniques. The applications discussed in this volume come predominantly from the fields of electrochemistry and biology. In contrast to those described in Vol. I, these sudies may be performed in air and in liquids. The extensions of the basic technique to map other interactions are described inchapters on scanning force microscopy, magnetic force microscopy, scanning near-field optical microscopy, together with a survey of other related techniques. Also described here is the use of a scanning proximal probe for surface modification. Togehter, the two volumes give a comprehensive account of experimental aspcets of STM. They provide essentialreading and reference material for all students and researchers involvedin this field.

  13. Spin-polarized scanning tunnelling microscopy

    The recent experimental progress in spin-polarized scanning tunnelling microscopy (SP-STM) - a magnetically sensitive imaging technique with ultra-high resolution - is reviewed. The basics of spin-polarized electron tunnelling are introduced as they have been investigated in planar tunnel junctions for different electrode materials, i.e. superconductors, optically excited GaAs, and ferromagnets. It is shown that ferromagnets and antiferromagnets are suitable tip materials for the realization of SP-STM. Possible tip designs and modes of operations are discussed for both classes of materials. The results of recent spatially resolved measurements as performed with different magnetic probe tips and using different modes of operation are reviewed and discussed in terms of applicability to surfaces, thin films, and nanoparticles. The limits of spatial resolution, and the impact of an external magnetic field on the imaging process

  14. Vibration Compensation for Scanning Tunneling Microscope

    LI Meng-chao; FU Xing; WEI Xiao-lei; HU Xiao-tang

    2003-01-01

    The influence of vibration is already one of main obstacles for improving the nano measuring accuracy.The techniques of anti-vibration,vibration isolation and vibration compensation become an important branch in nano measuring field.Starting with the research of sensitivity to vibration of scanning tunneling microscope(STM),the theory,techniques and realization methods of nano vibration sensor based on tunnel effect are initially investigated,followed by developing the experimental devices.The experiments of the vibration detection and vibration compensation are carried out.The experimental results show that vibration sensor based on tunnel effect is characterized by high sensitivity,good frequency characteristic and the same vibratory response characteristic consistent with STM.

  15. Scanning tunneling microscopy of biological molecules

    Scanning Tunnelling Microscopy (STM) has been used to image a number of biological molecules including thrombospondin and glycoprotein 88 (GP88). In this paper, STM images which clearly resolve the morphology of these molecules are presented. Ultimately, it is hoped that STM will provide information about the interaction between these molecules after overcoming problems associated with sample preparation and reproducibility of results which are discussed. 4 refs., 2 figs

  16. Imaging Pauli Repulsion in Scanning Tunneling Microscopy

    Weiss, C; Wagner, C.; Kleimann, C.; Rohlfing, M.; Tautz, F. S.; Temirov, R.

    2010-01-01

    A scanning tunneling microscope (STM) has been equipped with a nanoscale force sensor and signal transducer composed of a single D2 molecule that is confined in the STM junction. The uncalibrated sensor is used to obtain ultrahigh geometric image resolution of a complex organic molecule adsorbed on a noble metal surface. By means of conductance-distance spectroscopy and corresponding density functional calculations the mechanism of the sensor and transducer is identified. It probes the short-...

  17. A SCANNING TUNNELING MICROSCOPE FOR SURFACE MODIFICATION

    M. McCord; Pease, R

    1986-01-01

    With the recent success for the scanning tunneling microscope (STM) has come question of whether the instrument might be used for material modifications lithography. We embarked on the design of an STM with this application in mind. Its features include a wide x-y piezoelectric scan range of 10 or more microns, plus coarse mechanical motion in the x direction to a new region on the sample while in vacuum. Coarse motion in the z direction is accomplished with a micrometer drive, while fine mov...

  18. Topography Structure and Scanning Tunneling Spectrum of Nickel(Ⅱ)-tetraphenylporphyrin Molecules on Au(111)

    2006-01-01

    Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) were performed on monolayer film of NiTPP supported on Au(111) under ultrahigh vacuum (UHV) conditions. The constant current STM images show remarkable bias dependence. High resolution STM data clearly show the individual NiTPP molecules and allow easy differentiation between NiTPP and CoTPP reported before. Scanning tunneling spectra, as a function of molecule-tip separation, were acquired over a range of tip motion of 0.42 nm. Spectra do not show the variation in band splitting with tip distance. It appears for molecules such as NiTPP that the average potential at the molecule is essentially the same at the same metal substrate. For molecules of the height of NiTPP, the scanning tunneling spectra should give reliable occupied and unoccupied orbital energies over a wide range of tip-molecule distances.

  19. Conductivity map from scanning tunneling potentiometry

    Zhang, Hao; Li, Xianqi; Chen, Yunmei; Durand, Corentin; Li, An-Ping; Zhang, X.-G.

    2016-08-01

    We present a novel method for extracting two-dimensional (2D) conductivity profiles from large electrochemical potential datasets acquired by scanning tunneling potentiometry of a 2D conductor. The method consists of a data preprocessing procedure to reduce/eliminate noise and a numerical conductivity reconstruction. The preprocessing procedure employs an inverse consistent image registration method to align the forward and backward scans of the same line for each image line followed by a total variation (TV) based image restoration method to obtain a (nearly) noise-free potential from the aligned scans. The preprocessed potential is then used for numerical conductivity reconstruction, based on a TV model solved by accelerated alternating direction method of multiplier. The method is demonstrated on a measurement of the grain boundary of a monolayer graphene, yielding a nearly 10:1 ratio for the grain boundary resistivity over bulk resistivity.

  20. Superconducting phonon spectroscopy using a low-temperature scanning tunneling microscope

    Leduc, H. G.; Kaiser, W. J.; Hunt, B. D.; Bell, L. D.; Jaklevic, R. C.

    1989-01-01

    The low-temperature scanning tunneling microscope (STM) system described by LeDuc et al. (1987) was used to observe the phonon density of states effects in a superconductor. Using techniques based on those employed in macroscopic tunneling spectroscopy, electron tunneling current-voltage (I-V) spectra were measured for NbN and Pb, and dI/dV vs V spectra were measured using standard analog derivative techniques. I-V measurements on NbN and Pb samples under typical STM conditions showed no evidence for multiparticle tunneling effects.

  1. A compact low temperature scanning tunneling microscope

    We describe the design and fabrication of a compact Low Temperature Scanning Tunneling Microscope (LT-STM) together with a dipper cryostat for cooling the STM down to liquid helium temperatures. The STM, based on the piezo-tube walker as coarse approach mechanism, is suspended inside a cryostat vacuum can using three soft helical springs. The can is dipped into a liquid helium storage container for cooling the STM. Its compact size makes it less susceptible to mechanical vibrations and so the STM works with atomic resolution with a simple spring suspension. We demonstrate the performance of this STM for atomic resolution imaging and tunneling spectroscopy by observing the 3 x3 charge modulation and the energy gap in the Charge Density Wave (CDW) phase of 2H-NbSe2 at liquid helium temperatures.

  2. Simulation of scanning tunneling spectroscopy of supported carbon nanotubes

    The angle and energy dependent transmission of wave packets was calculated through a jellium potential model of a scanning tunneling microscope (STM) junction containing different arrangements of carbon nanotubes. The total tunnel current as a function of STM bias was calculated by statistical averaging over a distribution of wave packets in the allowed energy window. Three tunneling situations were studied: (i) a STM tunnel junction with no nanotube present, (ii) one single wall nanotube in the STM junction, and (iii) a nanotube 'raft'. The effects of point contacts at the STM tip/nanotube, at the nanotube/substrate, and at both interfaces were also investigated. The theory allowed us to identify components of pure geometrical origin responsible for the asymmetry in the scanning tunneling spectroscopy (STS) spectrum of the carbon nanotubes with respect to bias voltage polarity. The calculations show that for tip negative bias the angular dependence of the transmission is determined by the tip shape. The particular tip shape introduces an asymmetry on the negative side of the STS spectrum. For tip positive bias the angular dependence of the transmission depends strongly on the nature of the nanosystem in the STM gap. While the transmission of the STM tunnel junction with no nanotube present can be well represented by a one dimensional model, all other geometries cause a large normal-transverse momentum mixing of the wave packet. A diffraction-grating-like behavior is seen in the angular dependence of the transmission of the nanotube raft. Point contacts between the nanotube and the substrate cause an asymmetry in the positive side of the STS spectrum. Calculated STS spectra are compared to experimental ones

  3. COMBINED FIELD ION AND SCANNING TUNNELING MICROSCOPE

    Sakurai, T; Hashizurne, T.; Kamiya, I.; Hasegawa, Y.; Sakai, A; Kobayashi, A.; Matsui, J.; Takahashi, S; Kono, E.; Watanabe, H.

    1987-01-01

    Realizing the importance of characterizing a STM probe tip on an atomic scale, we have constructed a new instrument which combines a field ion microscope and scanning tunneling microscope. A complete STM set-up, which is similar to the one developed by Demuth, is mounted on an 8" O.D. flange and a FIM set-up is mounted on a 10" O.D. flange. FI images of the STM probe tip are observed using a 2" O.D. chevron channelplate-image intensifier screen assembly with liquid nitrogen cooling. A field n...

  4. Scanning Tunneling Spectroscope Use in Electrocatalysis Testing

    Turid Knutsen

    2010-01-01

    The relationship between the electrocatalytic properties of an electrode and its ability to transfer electrons between the electrode and a metallic tip in a scanning tunneling microscope (STM) is investigated. The alkaline oxygen evolution reaction (OER) was used as a test reaction with four different metallic glasses, Ni78Si8B14, Ni70Mo20Si5B5, Ni58Co20Si10B12, and Ni25Co50Si15B10, as electrodes. The electrocatalytic properties of the electrodes were determined. The electrode surfaces were t...

  5. Measuring voltage transients with an ultrafast scanning tunneling microscope

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1997-01-01

    We use an ultrafast scanning tunneling microscope to resolve propagating voltage transients in space and time. We demonstrate that the previously observed dependence of the transient signal amplitude on the tunneling resistance was only caused by the electrical sampling circuit. With a modified circuit, where the tunneling tip is directly connected to the current amplifier of the scanning tunneling microscope, this dependence is eliminated. Ail results can be explained with coupling through t...

  6. DIRECT TIP STRUCTURES DETERMINATION BY SCANNING TUNNELING MICROSCOPY

    GarcÍa CantÚ, R.; Huerta Garnica, M.

    1989-01-01

    An electrochemical etched scanning tunneling microscope tip is studied, using a long scan tunneling microscope and scanning electron microscopy, in order to characterize the neighborhood of the tip apex. Observed microstructure and protrusions are discussed in relation to chemical etching and mechanical resistance.

  7. Atomic and Molecular Manipulation with a Scanning Tunneling Microscope

    Sperl, Alexander

    2011-01-01

    In this thesis structural, electronic, chemical properties and dynamic processes of adsorbed nanostructures on metal surfaces are investigated with a low-temperature scanning tunneling microscope (STM).

  8. Scanning tunnel microscopy of semiconductor nanostructures

    In this work a scanning tunneling microscope (STM) is utilized as a surface sensitive tool for local characterization of internal potential profiles of GaAs/AlGaAs heterostructures. The STM is operated at variable temperatures under ambient conditions, i.e. either in air or in the variable temperature insert of a cryostat. Distinct local differences between current-voltage curves taken on inverted heterostructures, which were patterned by wet chemically etching, are found. The spectroscopic differences can be ascribed to the internal potential profile in the subsurface regions of the sample. Current imaging tunneling spectroscopy (CITS) is applied to study quantum wire regions. It is found that the magnitude of the CITS-current is an indirect measure of edge depletion zones, which are much larger at 4.2 K. Direct measurements of relevant energy levels in quantum structures were obtained by ballistic electron emission microscopy (BEEM). It is shown that this 3-terminal technique is an excellent tool for transport characterization of minibands formed in semiconductor superlattices. Furthermore, low dimensional electron gases are shown to act as very efficient collector electrodes at low temperatures. For the first time, BEEM experiments were performed at 4.2 K. The enhanced thermal resolution at 4.2 K allows an analysis of the relevant scattering processes. It is found that the collector current is strongly influenced by diffusive scattering at the metal/semiconductor interface. (author)

  9. Scanning tunneling microscope study of cadmium telluride

    Layered samples of cadmium telluride grown epitaxially on gallium arsenide substrates have been investigated by means of scanning tunneling microscopy (STM). The surface geometric and electronic structures are both of interest. Techniques were developed to remove the native oxide by etching, or to create a fresh surface by cleaving, and to protect them from oxidation by employing mineral or paraffin oil media. STM studies were conducted within the protective medium. These techniques were adapted and tested for both etched and cleaved samples of Si, CdTe and HgTe. The current-voltage characteristics of the CdTe surface were investigated during dynamic changes of the tunnel current and barrier height while the probe-to-sample separation (gap) was static. Recorded values are shown for current versus bias for several constant gap values. A range of bias values has been employed to test a possible solution for the problem of interference between the contributions from geometric and electronic structure factors

  10. Energy gaps measured by scanning tunneling microscopy

    A scanning tunneling microscope (STM) has been used to measure energy gaps in the charge-density-wave (CDW) phases of the layer-structure dichalcogenides and in the high-temperature superconductor Bi2Sr2CaCu2O8. Measured values of ΔCDW at 4.2 K for 2H-TaSe2, 2H-TaS2, and 2H-NbSe2 are 80, 50, and 34 meV giving values of 2ΔCDW/kBTc equal to 15.2, 15.4, and 23.9, indicating strong coupling in these CDW systems. Measured values of ΔCDW at 4.2 K in 1T-TaSe2 and 1T-TaS2 are ∼150 meV for both materials giving 2ΔCDW/kBTc∼5.8. STM scans of Bi2Sr2CaCu2O8 at 4.2 K resolve atoms on the BiOx layer and show possible variations in electronic structure. The energy gap determined from I versus V and dI/dV versus V curves is in the range 30--35 meV giving values of 2Δ/kBTc∼8. Spectroscopy measurements with the STM can exhibit large zero-bias anomalies which complicate the analysis of the energy-gap structure, but adequate separation has been accomplished

  11. Direct, coherent and incoherent intermediate state tunneling and scanning tunnel microscopy (STM)

    Theory and experiment in tunneling are still qualitative in nature, which hold true also for the latest developments in direct-, resonant-, coherent- and incoherent-tunneling. Those tunnel processes have recently branched out of the field of ''solid state tunnel junctions'' into the fields of scanning tunnel microscopy (STM), single electron tunneling (SET) and semiconducting resonant tunnel structures (RTS). All these fields have promoted the understanding of tunneling in different ways reaching from the effect of coherence, of incoherence and of charging in tunneling, to spin flip or inelastic effects. STM allows not only the accurate measurements of the tunnel current and its voltage dependence but, more importantly, the easy quantification via the (quantum) tunnel channel conductance and the distance dependence. This new degree of freedom entering exponentially the tunnel current allows an unique identification of individual tunnel channels and their quantification. In STM measurements large tunnel currents are observed for large distances d > 1 nm explainable by intermediate state tunneling. Direct tunneling with its reduced tunnel time and reduced off-site Coulomb charging bridges distances below 1 nm, only. The effective charge transfer process with its larger off-site and on-site charging at intermediate states dominates tunnel transfer in STM, biology and chemistry over distances in the nm-range. Intermediates state tunneling becomes variable range hopping conduction for distances larger than d > 2 nm, for larger densities of intermediate states n1(ε) and for larger temperatures T or voltages U, still allowing high resolution imaging

  12. Measuring voltage transients with an ultrafast scanning tunneling microscope

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1997-01-01

    We use an ultrafast scanning tunneling microscope to resolve propagating voltage transients in space and time. We demonstrate that the previously observed dependence of the transient signal amplitude on the tunneling resistance was only caused by the electrical sampling circuit. With a modified...... circuit, where the tunneling tip is directly connected to the current amplifier of the scanning tunneling microscope, this dependence is eliminated. Ail results can be explained with coupling through the geometrical capacitance of the tip-electrode junction. By illuminating the current...

  13. Scanning tunneling microscopy, orbital-mediated tunneling spectroscopy, and ultraviolet photoelectron spectroscopy of metal(II) tetraphenylporphyrins deposited from vapor.

    Scudiero, L; Barlow, D E; Mazur, U; Hipps, K W

    2001-05-01

    Thin films of vapor-deposited Ni(II) and Co(II) complexes of tetraphenylporphyrin (NiTPP and CoTPP) were studied supported on gold and embedded in Al-Al(2)O(3)-MTPP-Pb tunnel diodes, where M = Ni or Co. Thin films deposited onto polycrystalline gold were analyzed by ultraviolet photoelectron spectroscopy (UPS) using He I radiation. Scanning tunneling microscopy (STM) and orbital-mediated tunneling spectroscopy (STM-OMTS) were performed on submonolayer films of CoTPP and NiTPP supported on Au(111). Inelastic electron tunneling spectroscopy (IETS) and OMTS were measured in conventional tunnel diode structures. The highest occupied pi molecular orbital of the porphyrin ring was seen in both STM-OMTS and UPS at about 6.4 eV below the vacuum level. The lowest unoccupied pi molecular orbital of the porphyrin ring was observed by STM-OMTS and by IETS-OMTS to be located near 3.4 eV below the vacuum level. The OMTS spectra of CoTPP had a band near 5.2 eV (below the vacuum level) that was attributed to transient oxidation of the central Co(II) ion. That is, it is due to electron OMT via the half-filled d(z)(2) orbital present in Co(II) of CoTPP. The NiTPP OMTS spectra show no such band, consistent with the known difficulty of oxidation of the Ni(II) ion. The STM-based OMTS allowed these two porphyrin complexes to be easily distinguished. The present work is the first report of the observation of STM-OMTS, tunnel junction OMTS, and UPS of the same compounds. Scanning tunneling microscope-based orbital-mediated tunneling provides more information than UPS or tunnel junction-based OMTS and does so with molecular-scale resolution. PMID:11457159

  14. Scanning Tunneling Microscopy of Layered Materials

    Qin, Xiaorong

    This dissertation describes studies of the surfaces of layered materials, including graphite intercalation compounds, transition-metal-dichalcogenides, and single layers of MoS_2. with scanning tunneling microscopy (STM). In order to understand how tunneling images reflect the atomic nature of sample surfaces, the electronic and structural properties of intercalated graphite surfaces imaged with STM have been investigated theoretically. The corrugation amplitude (CA) and carbon site asymmetry (CSA) are sensitive to the number of graphite layers covering the first intercalate layer, to the amount and distribution of the charge transferred from intercalate to host and to the surface subband structure. The CA and CSA can be used to map the stage domains across a freshly cleaved surface. The STM images of the surfaces of both donor and acceptor graphite intercalation compounds are discussed. The theory successfully explained the available experimental results, and yielded some predictions which have been verified in recent experiments. A STM system for operation in air was assembled. The crystalline surfaces of graphite and three transition-metal -dichalcogenides (2H-MoS_2, WTe _2 and ReSe_2) have been studied with the STM system. Single layers of MoS_2 can be obtained by the exfoliation of lithium-intercalated MoS_2 powder in water and in several alcohols. In the STM observations, the samples were prepared by depositing either an aqueous or butanol suspension of single-layer MoS_2 on graphite substrates to form restacked films with two monolayers of solvent molecules included between the layers of MoS_2 . The real-space images obtained from the films all showed the existence of an approximate 2 x 1 superstructure on the surfaces, although the 2 x 1 pattern can be modulated by the interface interaction between the MoS_2 layer and the solvent molecules. These results, in conjunction with existing x-ray diffraction and Raman results, imply that the single layers of MoS_2

  15. Measurement of turbulence spectra using scanning pulsed wind lidars

    Sathe, Ameya; Mann, Jakob

    2012-01-01

    Turbulent velocity spectra, as measured by a scanning pulsed wind lidar (WindCube), are analyzed. The relationship between ordinary velocity spectra and lidar derived spectra is mathematically very complex, and deployment of the three-dimensional spectral velocity tensor is necessary. The resulting...... theoretical understanding of the shape of turbulent velocity spectra measured by scanning pulsed wind lidar is given a firm foundation....

  16. Bulk Cr tips for scanning tunneling microscopy and spin-polarized scanning tunneling microscopy

    Bassi, A. Li; Casari, C. S.; D. Cattaneo; Donati, F.; Foglio, S.; M. Passoni; Bottani, C. E.; Biagioni, P.; Brambilla, A.; Finazzi, M.; F. Ciccacci; Duo', L.

    2007-01-01

    A simple, reliable method for preparation of bulk Cr tips for Scanning Tunneling Microscopy (STM) is proposed and its potentialities in performing high-quality and high-resolution STM and Spin Polarized-STM (SP-STM) are investigated. Cr tips show atomic resolution on ordered surfaces. Contrary to what happens with conventional W tips, rest atoms of the Si(111)-7x7 reconstruction can be routinely observed, probably due to a different electronic structure of the tip apex. SP-STM measurements of...

  17. Scanning tunneling microscopy and inelastic electron tunneling spectroscopy studies of methyl isocyanide adsorbed on Pt(111)

    A low-temperature scanning tunneling microscope (STM) was used to investigate the adsorption state of a single methyl isocyanide (MeNC) molecule on the Pt(111) surface at 4.7 K. We found that MeNC was resolved as a round-shaped protrusion in the STM image. The STM image of paired MeNC is highly protruded in comparison with that of isolated MeNC due to the charge transfer from Pt to MeNC. Inelastic electron tunneling spectroscopy with the STM system (STM-IETS) was also employed in order to reveal the adsorption state of individual MeNC molecules on Pt(111). The STM-IETS spectrum of MeNC exhibits peaks at 8, 48 and 375 mV. Referring to the vibrational spectra reported previously, we assigned these peaks to the frustrated translation mode, PtC stretching mode and CH3 stretching mode, respectively. The absence of other vibrational modes could be due to a reduction of the elastic tunneling current.

  18. The fabrication of reproducible superconducting scanning tunneling microscope tips

    Naaman, O.; Teizer, W.; Dynes, R. C.

    2000-01-01

    Superconducting scanning tunneling microscope tips have been fabricated with a high degree of reproducibility. The fabrication process relies on sequential deposition of superconducting Pb and a proximity-coupled Ag capping layer onto a Pt/Ir tip. The tips were characterized by tunneling into both normal-metal and superconducting films. The simplicity of the fabrication process, along with the stability and reproducibility of the tips, clear the way for tunneling studies with a well-character...

  19. Spectral Measurement of Photon Emission from Individual Gold Nanoparticles Using Scanning Tunneling Microscopy

    S.A. Nepijko

    2016-06-01

    Full Text Available The light emission spectra of individual Au nanoparticles induced by a scanning tunneling microscope (STM have been investigated. Two-dimensional ensembles of tunnel-coupled Au particles were prepared by thermal evaporation onto a native oxide silicon wafer in ultrahigh vacuum (10 – 9 mbar. Our STM measurements show a single peak at photon energy 1.6 eV in the tunneling mode and two peaks at 2.2 eV (connected with the Mie plasmon and 1.45 eV (a new peak which was not discussed in literature before in the field emission mode.

  20. Investigation of local tunneling current noise spectra on the silicon crystal surfaces by means of STM/STS

    Mantsevich, V. N., E-mail: vmantsev@spmlab.phys.msu.su; Maslova, N. S. [Moscow State University, Department of Physics (Russian Federation); Cao, G. Y. [Chinese Academy of Sciences, Wuhan Institute of Physics and Mathematics (China)

    2015-08-15

    We report on a careful analysis of the local tunneling conductivity by means of ultra-high vacuum scanning tunneling microscopy/spectroscopy (STM/STS) technique in the vicinity of low-dimensional structures on the Si(111)–(7 × 7) and Si(110)–(16 × 2) surfaces. The power-law exponent α of low-frequency tunneling current noise spectra is investigated for different values of the tunneling contact parameters: relaxation rates, the localized state coupling, and the tunneling barrier width and height.

  1. Investigation of local tunneling current noise spectra on the silicon crystal surfaces by means of STM/STS

    We report on a careful analysis of the local tunneling conductivity by means of ultra-high vacuum scanning tunneling microscopy/spectroscopy (STM/STS) technique in the vicinity of low-dimensional structures on the Si(111)–(7 × 7) and Si(110)–(16 × 2) surfaces. The power-law exponent α of low-frequency tunneling current noise spectra is investigated for different values of the tunneling contact parameters: relaxation rates, the localized state coupling, and the tunneling barrier width and height

  2. Observation of spin-polarized tunneling by scanning tunneling microscopy

    The tunneling magnetoresistance (TMR) in ferromagnet-vacuum-ferromagnet junction was studied by using an STM setup. After in situ cleaning of both of two ferromagnetic electrodes, up to 20% of TMR was observed. Such a signal was not observed for air gap nor nonmagnetic electrode. This technique is suitable for basic research of the TMR effect

  3. Optical characterication of probes for photon scanning tunnelling microscopy

    Vohnsen, Brian; Bozhevolnyi, Sergey I.

    The photon scanning tunnelling microscope is a well-established member of the family of scanning near-field optical microscopes used for optical imaging at the sub-wavelength scale. The quality of the probes, typically pointed uncoated optical fibres, used is however difficult to evaluate in a...

  4. Compact, single-tube scanning tunneling microscope with thermoelectric cooling

    Jobbins, Matthew M.; Agostino, Christopher J.; Michel, Jolai D.; Gans, Ashley R.; Kandel, S. Alex

    2013-10-01

    We have designed and built a scanning tunneling microscope with a compact inertial-approach mechanism that fits inside the piezoelectric scanner tube. Rigid construction allows the microscope to be operated without the use of external vibration isolators or acoustic enclosures. Thermoelectric cooling and a water-ice bath are used to increase temperature stability when scanning under ambient conditions.

  5. Applications of terrestrial laser scanning for tunnels: a review

    Weixing Wang

    2014-10-01

    Full Text Available In recent years, the use of terrestrial laser scanning (TLS technique in engineering surveys is gaining an increasing interest due to the advantages of non-contact, rapidity, high accuracy, and large scale. Millions of accurate 3D points (mm level accuracy can be delivered by this technique with a high point density in a short time (up to 1 million points per second, which makes it a potential technique for large scale applications in engineering environments such as tunnels, bridges, and heritage buildings. Tunnels, in particular those with long lengths, create great challenges for surveyors to obtain the satisfactory scanned data. This paper presents a short history of TLS techniques used for tunnels. A general overview of TLS techniques is given, followed by a review of several applications of TLS for tunnels. These applications are classified as: detecting geological features of drilling tunnels, monitoring the geometry of tunnels during excavation, making deformation measurements, and extracting features. The review emphasizes how TLS techniques can be used to measure various aspects of tunnels. It is clear that TLS techniques are not yet a common tool for tunnel investigations, but there is still a huge potential to excavate.

  6. A cryogen-free low temperature scanning tunneling microscope capable of inelastic electron tunneling spectroscopy.

    Zhang, Shuai; Huang, Di; Wu, Shiwei

    2016-06-01

    The design and performance of a cryogen-free low temperature scanning tunneling microscope (STM) housed in ultrahigh vacuum (UHV) are reported. The cryogen-free design was done by directly integrating a Gifford-McMahon cycle cryocooler to a Besocke-type STM, and the vibration isolation was achieved by using a two-stage rubber bellow between the cryocooler and a UHV-STM interface with helium exchange gas cooling. A base temperature of 15 K at the STM was achieved, with a possibility to further decrease by using a cryocooler with higher cooling power and adding additional low temperature stage under the exchange gas interface. Atomically sharp STM images and high resolution dI/dV spectra on various samples were demonstrated. Furthermore, we reported the inelastic tunneling spectroscopy on a single carbon monoxide molecule adsorbed on Ag(110) surface with a cryogen-free STM for the first time. Being totally cryogen-free, the system not only saves the running cost significantly but also enables uninterrupted data acquisitions and variable temperature measurements with much ease. In addition, the system is capable of coupling light to the STM junction by a pair of lens inside the UHV chamber. We expect that these enhanced capabilities could further broaden our views to the atomic-scale world. PMID:27370453

  7. A cryogen-free variable temperature scanning tunneling microscope capable for inelastic electron tunneling spectroscopy

    Zhang, Shuai; Huang, Di; Wu, Shiwei

    While low temperature scanning tunneling microscope (STM) has become an indispensable research tool in surface science, its versatility is yet limited by the shortage or high cost of liquid helium. The makeshifts include the use of alternative cryogen (such as liquid nitrogen) at higher temperature or the development of helium liquefier system usually at departmental or campus wide. The ultimate solution would be the direct integration of a cryogen-free cryocooler based on GM or pulse tube closed cycle in the STM itself. However, the nasty mechanical vibration at low frequency intrinsic to cryocoolers has set the biggest obstacle because of the known challenges in vibration isolation required to high performance of STM. In this talk, we will present the design and performance of our home-built cryogen-free variable temperature STM at Fudan University. This system can obtain atomically sharp STM images and high resolution dI/dV spectra comparable to state-of-the-art low temperature STMs, but with no limitation on running hours. Moreover, we demonstrated the inelastic tunneling spectroscopy (STM-IETS) on a single CO molecule with a cryogen-free STM for the first time.

  8. Structural monitoring of tunnels using terrestrial laser scanning

    R. C. Lindenbergh; Uchanski, L.; Bucksch, A.; Van Gosliga, R.

    2009-01-01

    In recent years terrestrial laser scanning is rapidly evolving as a surveying technique for the monitoring of engineering objects like roof constructions, mines, dams, viaducts and tunnels. The advantage of laser scanning above traditional surveying methods is that it allows for the rapid acquisition of millions of scan points representing the whole surface of the object considered. Still it is a big challenge to obtain accuracies and precisions in the millimeter level when quantifying deform...

  9. Scanning Tunneling Spectroscopy on Electron-Boson Interactions in Superconductors

    Schackert, Michael Peter

    2014-01-01

    This thesis describes the experimental study of electron-boson interactions in superconductors by means of inelastic electron tunneling spectroscopy performed with a scanning tunneling microscope (STM) at temperatures below 1 K. This new approach allows the direct measurement of the Eliashberg function of conventional superconductors as demonstrated on lead (Pb) and niobium (Nb). Preparative experiments on unconventional iron-pnictides are presented in the end.

  10. Towards magnetic resonance in scanning tunneling microscopy using heterodyne detection

    Peter, Moritz

    2015-01-01

    The present work introduces a new concept for magnetic resonance measurements in the GHz regime inside a scanning tunneling microscope. It is based on heterodyne detection in a spin-polarized tunneling barrier. The experimental requirements, including a new method to suppress transmission effects, are explained. Measurements on three model systems which were studied to validate the new technique are presented and compared to simulations.

  11. Design of a scanning tunneling microscope for electrochemical applications

    Dovek, Moris M.; Heben, Michael J.; Lang, Christop A.; Lewis, Nathan S.; Quate, Calvin F.

    1988-01-01

    A design for a scanning tunneling microscope that is well suited for electrochemical investigations is presented. The construction of the microscope ensures that only the tunneling tip and the sample participate in electrochemical reactions. The design also allows rapid replacement of the tip or sample, and enables facile introduction of auxiliary electrodes for use in electrochemical experiments. The microscope utilizes stepper motor driven approach mechanics in order to achieve fully remote...

  12. Scanning tunneling spectroscopy on electron-boson interactions in superconductors

    Schackert, Michael Peter

    2015-01-01

    This work describes the experimental study of electron-boson interactions in superconductors by means of inelastic electron tunneling spectroscopy performed with a scanning tunneling microscope (STM) at temperatures below 1 K. This new approach allows the direct measurement of the Eliashberg function of conventional superconductors as demonstrated on lead (Pb) and niobium (Nb). Preparative experiments on unconventional iron-pnictides are presented in the end.

  13. Scanning Tunneling Luminescence of Pentacene Nanocrystals

    Kabakchiev, Alexander

    2010-01-01

    Organic semiconductors are promising materials for future electronic and electroluminescence applications. A detailed understanding of organic layers and nano-sized crystals down to single molecules can address fundamental questions of contacting organic semiconductors at the nanometer limit and obtaining luminescence from them. In this thesis, electroluminescence spectra from pentacene, a policyclic hydrocarbon (acene), are discussed. The luminescenc...

  14. Measurement of turbulence spectra using scanning pulsed wind lidars

    Sathe, A.; Mann, J.

    2012-01-01

    Turbulent velocity spectra, as measured by a scanning pulsed wind lidar (WindCube), are analyzed. The relationship between ordinary velocity spectra and lidar derived spectra is mathematically very complex, and deployment of the three-dimensional spectral velocity tensor is necessary. The resulting

  15. Probing the Inelastic Interactions in Molecular Junctions by Scanning Tunneling Microscope

    Xu, Chen

    With a sub-Kelvin scanning tunneling microscope, the energy resolution of spectroscopy is improved dramatically. Detailed studies of finer features of spectrum become possible. The asymmetry in the line shape of carbon monoxide vibrational spectra is observed to correlate with the couplings of the molecule to the tip and substrates. The spin-vibronic coupling in the molecular junctions is revisited with two metal phthalocyanine molecules, unveiling sharp spin-vibronic peaks. Finally, thanks to the improved spectrum resolution, the bonding structure of the acyclic compounds molecules is surveyed with STM inelastic tunneling probe, expanding the capability of the innovative high resolution imaging technique.

  16. A nanoscale gigahertz source realized with Josephson scanning tunneling microscopy

    Jäck, Berthold, E-mail: b.jaeck@fkf.mpg.de; Eltschka, Matthias; Assig, Maximilian; Etzkorn, Markus; Ast, Christian R. [Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart (Germany); Hardock, Andreas [Institut für Theoretische Elektrotechnik, Technische Universität Hamburg-Harburg, 21079 Hamburg (Germany); Kern, Klaus [Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart (Germany); Institut de Physique de la Matière Condensée, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland)

    2015-01-05

    Using the AC Josephson effect in the superconductor-vacuum-superconductor tunnel junction of a scanning tunneling microscope (STM), we demonstrate the generation of GHz radiation. With the macroscopic STM tip acting as a λ/4-monopole antenna, we first show that the atomic scale Josephson junction in the STM is sensitive to its frequency-dependent environmental impedance in the GHz regime. Further, enhancing Cooper pair tunneling via excitations of the tip eigenmodes, we are able to generate high-frequency radiation. We find that for vanadium junctions, the enhanced photon emission can be tuned from about 25 GHz to 200 GHz and that large photon flux in excess of 10{sup 20 }cm{sup −2} s{sup −1} is reached in the tunnel junction. These findings demonstrate that the atomic scale Josephson junction in an STM can be employed as a full spectroscopic tool for GHz frequencies on the atomic scale.

  17. A nanoscale gigahertz source realized with Josephson scanning tunneling microscopy

    Using the AC Josephson effect in the superconductor-vacuum-superconductor tunnel junction of a scanning tunneling microscope (STM), we demonstrate the generation of GHz radiation. With the macroscopic STM tip acting as a λ/4-monopole antenna, we first show that the atomic scale Josephson junction in the STM is sensitive to its frequency-dependent environmental impedance in the GHz regime. Further, enhancing Cooper pair tunneling via excitations of the tip eigenmodes, we are able to generate high-frequency radiation. We find that for vanadium junctions, the enhanced photon emission can be tuned from about 25 GHz to 200 GHz and that large photon flux in excess of 1020 cm−2 s−1 is reached in the tunnel junction. These findings demonstrate that the atomic scale Josephson junction in an STM can be employed as a full spectroscopic tool for GHz frequencies on the atomic scale

  18. Atomic and molecular manipulation with the scanning tunneling microscope.

    Stroscio, J A; Eigler, D M

    1991-11-29

    The prospect of manipulating matter on the atomic scale has fascinated scientists for decades. This fascination may be motivated by scientific and technological opportunities, or from a curiosity about the consequences of being able to place atoms in a particular location. Advances in scanning tunneling microscopy have made this prospect a reality; single atoms can be placed at selected positions and structures can be built to a particular design atom-by-atom. Atoms and molecules may be manipulated in a variety of ways by using the interactions present in the tunnel junction of a scanning tunneling microscope. Some of these recent developments and some of the possible uses of atomic and molecular manipulation as a tool for science are discussed. PMID:17773601

  19. Size dependence in tunneling spectra of PbSe quantum-dot arrays

    Interdot Coulomb interactions and collective Coulomb blockade were theoretically argued to be a newly important topic, and experimentally identified in semiconductor quantum dots, formed in the gate confined two-dimensional electron gas system. Developments of cluster science and colloidal synthesis accelerated the studies of electron transport in colloidal nanocrystal or quantum-dot solids. To study the interdot coupling, various sizes of two-dimensional arrays of colloidal PbSe quantum dots are self-assembled on flat gold surfaces for scanning tunneling microscopy and scanning tunneling spectroscopy measurements at both room and liquid-nitrogen temperatures. The tip-to-array, array-to-substrate, and interdot capacitances are evaluated and the tunneling spectra of quantum-dot arrays are analyzed by the theory of collective Coulomb blockade. The current-voltage of PbSe quantum-dot arrays conforms properly to a scaling power law function. In this study, the dependence of tunneling spectra on the sizes (numbers of quantum dots) of arrays is reported and the capacitive coupling between quantum dots in the arrays is explored.

  20. Design and calibration of a vacuum compatible scanning tunneling microscope

    Abel, Phillip B.

    1990-01-01

    A vacuum compatible scanning tunneling microscope was designed and built, capable of imaging solid surfaces with atomic resolution. The single piezoelectric tube design is compact, and makes use of sample mounting stubs standard to a commercially available surface analysis system. Image collection and display is computer controlled, allowing storage of images for further analysis. Calibration results from atomic scale images are presented.

  1. Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope

    Nazin, G. V.; S. W. Wu; Ho, W.

    2005-01-01

    The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks correspondi...

  2. Scanning tunneling microscopy III theory of STM and related scanning probe methods

    Güntherodt, Hans-Joachim

    1996-01-01

    Scanning Tunneling Microscopy III provides a unique introduction to the theoretical foundations of scanning tunneling microscopy and related scanning probe methods. The different theoretical concepts developed in the past are outlined, and the implications of the theoretical results for the interpretation of experimental data are discussed in detail. Therefore, this book serves as a most useful guide for experimentalists as well as for theoreticians working in the filed of local probe methods. In this second edition the text has been updated and new methods are discussed.

  3. Holders for in situ treatments of scanning tunneling microscopy tips

    We have developed holders for scanning tunneling microscopy tips that can be used for in situ treatments of the tips, such as electron bombardment (EB) heating, ion sputtering, and the coating of magnetic materials. The holders can be readily installed into the transfer paths and do not require any special type of base stages. Scanning electron microscopy is used to characterize the tip apex after EB heating. Also, spin-polarized scanning tunneling spectroscopy using an Fe coated W tip on the Cr(001) single crystal surface is performed in order to confirm both the capability of heating a tip up to about 2200 K and the spin sensitivity of the magnetically coated tip.

  4. Time-resolved scanning tunnelling microscopy for molecular science

    Time-resolved scanning tunnelling microscopy (STM) and its application in molecular science are reviewed. STM can image individual atoms and molecules and thus is able to observe the results of molecular processes such as diffusion, desorption, configuration switching, bond-breaking and chemistry, on the atomic scale. This review will introduce time-resolved STM, its experimental limitations and implementations with particular emphasis on thermally activated and tunnelling current induced molecular processes. It will briefly examine the push towards ultrafast imaging. In general, results achieved by time-resolved STM demonstrate the necessity of both space and time resolution for fully characterizing molecular processes on the atomic scale.

  5. Seismic scanning tunneling macroscope - Elastic simulations and Arizona mine test

    Hanafy, Sherif M.

    2012-01-01

    Elastic seismic simulations and field data tests are used to validate the theory of a seismic scanning tunneling macroscope (SSTM). For nearfield elastic simulation, the SSTM results show superresolution to be better than λ/8 if the only scattered data are used as input data. If the direct P and S waves are muted then the resolution of the scatterer locations are within about λ/5. Seismic data collected in an Arizona tunnel showed a superresolution limit of at least λ/19. These test results are consistent with the theory of the SSTM and suggest that the SSTM can be a tool used by geophysicists as a probe for near-field scatterers.

  6. Luminescence from 3,4,9,10-perylenetetracarboxylic dianhydride on Ag(111) surface excited by tunneling electrons in scanning tunneling microscopy.

    Ino, Daisuke; Yamada, Taro; Kawai, Maki

    2008-07-01

    The electronic excitations induced with tunneling electrons into adlayers of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Ag(111) have been investigated by in situ fluorescence spectroscopy in scanning tunneling microscopy (STM). A minute area of the surface is excited by an electron tunneling process in STM. Fluorescence spectra strongly depend on the coverage of PTCDA on Ag(111). The adsorption of the first PTCDA layer quenches the intrinsic surface plasmon originated from the clean Ag(111). When the second layer is formed, fluorescence spectra are dominated by the signals from PTCDA, which are interpreted as the radiative decay from the manifold of first singlet excited state (S(1)) of adsorbed PTCDA. The fluorescence of PTCDA is independent of the bias polarity. In addition, the fluorescence excitation spectrum agrees with that by optical excitation. Both results indicate that S(1) is directly excited by the inelastic impact scattering of electrons tunneling within the PTCDA adlayer. PMID:18624490

  7. Scanning tunneling microscopy of carbon nanotubes: simulation and interpretation

    Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are powerful techniques to investigate electronic and topographical properties of carbon nanotubes. The growing availability of experimental data enables us to study perfect tubules and to probe particular features of nanotubes such as topological (twists) or non-topological (pentagonal and heptagonal rings) modification of the hexagonal lattice and ending caps structures. We have recently proposed a general approach to interpret and predict STM and STS observations. Our formalism, which is based on a tight-binding framework, is sufficiently precise to be used routinely for various carbon sp2 geometries. Confronted with experimental results, our approach reveals to be a useful tool to help in the interpretation and prediction of STM and STS measurements

  8. Scanning tunnelling microscopy: application to field electron emission studies

    The principles of scanning tunnelling microscopy (STM) are extended to the study of field electron emission from metal, semiconducting and semi-insulating materials. A specially designed, high-vacuum STM device called a scanning tunnelling field emission microscope (STFEM) is constructed, and new measuring procedures are developed to examine complex physical properties of emission centres. Providing high bias voltages and fast mapping of large squares, the STFEM allows one to obtain reliable statistical data on surface properties, namely topography, emission intensity, surface potential distribution and local electroconductivity. Results from a study of low-field electron emission from CVD diamond films are described to illustrate the functional capabilities of the new STM device. It was found that the diamond films studied are composed of nanograined phases distinguished by their physical properties. It has also been noted that the low-field electron emission from the studied samples is associated with the interfaces of these phases. (author)

  9. Plasma etching of superconducting Niobium tips for scanning tunneling microscopy

    We have developed a reproducible technique for the fabrication of sharp superconducting Nb tips for scanning tunneling microscopy (STM) and scanning tunneling spectroscopy. Sections of Nb wire with 250 μm diameter are dry etched in an SF6 plasma in a Reactive Ion Etcher. The gas pressure, etching time, and applied power are chosen to control the ratio of isotropic to anisotropic etch rates and produce the desired tip shape. The resulting tips are atomically sharp, with radii of less than 100 nm, mechanically stable, and superconducting. They generate good STM images and spectroscopy on single crystal samples of Au(111), Au(100), and Nb(100), as well as a doped topological insulator Bi2Se3 at temperatures ranging from 30 mK to 9 K.

  10. Scanning tunneling microscopy and spectroscopy studies of graphite edges

    Niimi, Y; Kambara, H; Tagami, K; Tsukada, M; Fukuyama, H; Fukuyama, Hiroshi

    2004-01-01

    We studied experimentally and theoretically the electronic local density of states (LDOS) near single step edges at the surface of exfoliated graphite. In scanning tunneling microscopy measurements, we observed the $(\\sqrt{3} \\times \\sqrt{3}) R 30^{\\circ}$ and honeycomb superstructures both extending over 3$-$4 nm either from the zigzag or armchair edge. Calculations based on a density-functional derived non-orthogonal tight-binding model show that these superstructures can coexist if the two types of edge admix each other in real graphite step edges. Scanning tunneling spectroscopy measurements near the zigzag edge reveal a clear peak in the LDOS at an energy below the Fermi energy by 20 meV. No such a peak was observed near the armchair edge. We concluded that this peak corresponds to the "edge state" theoretically predicted for graphene ribbons, since a similar prominent LDOS peak due to the edge state is obtained by the first principles calculations.

  11. Imaging atoms and molecules on surfaces by scanning tunnelling microscopy

    This review discusses nearly 30 years of scanning tunnelling microscopy (STM) work on high resolution imaging of numerous materials systems, giving a historical perspective on the field through the author's work. After a brief discussion of early STM and atomic force microscope (AFM) instrumentation development, the review discusses high resolution STM imaging on semiconductors, metals on semiconductors, Au(1 1 1), metal on metals including surface alloys, oxygen on metals, molecules adsorbed on metals, and AFM measurements of friction on graphite and mica.

  12. The electroluminescence and scanning tunneling microscopy of single molecules

    Buker, John William

    2009-01-01

    The scanning tunneling microscopy (STM) of single molecules has become a prominent experimental method in the field of molecular electronics. It has been found that in STM experiments, when an electric current flows through a single molecule, the molecule may luminesce. This electroluminescence, in conjunction with traditional STM data, provides a potentially important additional degree of freedom for understanding nanoscale systems. This thesis describes exploratory theoretical work on the n...

  13. Distinction of Nuclear Spin States with the Scanning Tunneling Microscope

    Natterer, Fabian Donat; Patthey, François; Brune, Harald

    2013-01-01

    We demonstrate rotational excitation spectroscopy with the scanning tunneling microscope for physisorbed hydrogen and its isotopes hydrogen-deuterid and deuterium. The observed excitation energies are very close to the gas phase values and show the expected scaling with moment of inertia. Since these energies are characteristic for the molecular nuclear spin states we are able to identify the para and ortho species of hydrogen and deuterium, respectively. We thereby demonstrate nuclear spin s...

  14. Photon scanning tunneling microscope in combination with a force microscope

    Moers, M.H.P.; Tack, R.G.; Hulst, van, N.F.; Bölger, B.

    1994-01-01

    The simultaneous operation of a photon scanning tunneling microscope with an atomic force microscope is presented. The use of standard atomic force silicon nitride cantilevers as near-field optical probes offers the possibility to combine the two methods. Vertical forces and torsion are detected simultaneously with the optical near field, which allows a comparison between topography and the optical signal. Images of an optical thin film (indium tin oxide) and a Langmuir-Blodgett layer (pentac...

  15. Applications of terrestrial laser scanning for tunnels: a review

    Weixing Wang; Weisen Zhao; Lingxiao Huang; Vivian Vimarlund; Zhiwei Wang

    2014-01-01

    In recent years, the use of terrestrial laser scanning (TLS) technique in engineering surveys is gaining an increasing interest due to the advantages of non-contact, rapidity, high accuracy, and large scale. Millions of accurate 3D points (mm level accuracy) can be delivered by this technique with a high point density in a short time (up to 1 million points per second), which makes it a potential technique for large scale applications in engineering environments such as tunnels, bridges, and ...

  16. Construction of silicon nanocolumns with the scanning tunneling microscope

    Ostrom, R. M.; Tanenbaum, D. M.; Gallagher, Alan

    1992-08-01

    Voltage pulses to a scanning tunneling microscope (STM) are used to construct silicon columns of 30-100 Å diameter and up to 200 Å height on a silicon surface and on the end of a tungsten probe. These nanocolumns have excellent conductivity and longevity, and they provide an exceptional new ability to measure the shapes of nanostructures with a STM. This construction methodology and these slender yet robust columns provide a basis for nanoscale physics, lithography, and technology.

  17. Sub-Kelvin scanning tunneling microscopy on magnetic molecules

    Zhang, Lei

    2012-01-01

    Magnetic molecules have attracted lots interest. In this work, an ultra-stable and low noise scanning tunneling microscopy operating at 400 mK using He-3 (930 mK using He-4) has been developed. The magnetic behavior of different magnetic molecules on substrates, especially the exchange interaction between the magnetic ions, the magnetic anisotropy on the surface, the magnetic excitations as well as the Kondo effect, were studied by using STM.

  18. Scanning tunneling microscopy on rough surfaces: quantitative image analysis

    Reiss, Günter; Bruckl, Hubert; Vancea, Johann; Lecheler, R.; Hastreiter, E.

    1991-01-01

    In this communication, the application of scanning tunneling microscopy (STM) for a quantitative evaluation of roughnesses and mean island sizes of polycrystalline thin films is discussed. Provided strong conditions concerning the resolution are satisfied, the results are in good agreement with standard techniques as, for example, transmission electron microscopy. Owing to its high resolution, STM can supply a better characterization of surfaces than established methods, especially concerning...

  19. Molecular Structure of DNA by Scanning Tunneling Microscopy

    Cricenti, A.; Selci, S.; Felici, A. C.; Generosi, R.; Gori, E.; Djaczenko, W.; Chiarotti, G.

    1989-09-01

    Uncoated DNA molecules marked with an activated tris(1-aziridinyl) phosphine oxide (TAPO) solution were deposited on gold substrates and imaged in air with the use of a high-resolution scanning tunneling microscope (STM). Constant-current and gap-modulated STM images show clear evidence of the helicity of the DNA structure: pitch periodicity ranges from 25 and 35 angstroms, whereas the average diameter is 20 angstroms. Molecular structure within a single helix turn was also observed.

  20. Tip preparation for usage in an ultra-low temperature UHV scanning tunneling microscope

    S. Ernst, S. Wirth, M. Rams, V. Dolocan and F. Steglich

    2007-01-01

    Full Text Available This work deals with the preparation and characterization of tungsten tips for the use in UHV low-temperature scanning tunneling microscopy and spectroscopy (STM and STS, respectively. These specific environments require in situ facilities for tip conditioning, for further sharpening of the tips, as well as for reliable tip characterization. The implemented conditioning methods include direct resistive annealing, annealing by electron bombardment, and self-sputtering with noble gas ions. Moreover, results from in situ tip characterization by field emission and STM experiments were compared to ex situ scanning electron microscopy. Using the so-prepared tips, high resolution STM images and tunneling spectra were obtained in a temperature range from ambient down to 350 mK, partially with applied magnetic field, on a variety of materials.

  1. Optical characterication of probes for photon scanning tunnelling microscopy

    Vohnsen, Brian; Bozhevolnyi, Sergey I.

    1999-01-01

    The photon scanning tunnelling microscope is a well-established member of the family of scanning near-field optical microscopes used for optical imaging at the sub-wavelength scale. The quality of the probes, typically pointed uncoated optical fibres, used is however difficult to evaluate in a...... technique. Here we present experimental results obtained for optical characterization of two different probes by imaging of a well-specified near-field intensity distribution at various spatial frequencies. In particular, we observe that a sharply pointed dielectric probe can be highly suitable for imaging...

  2. A scanning tunneling microscope for a dilution refrigerator.

    Marz, M; Goll, G; Löhneysen, H v

    2010-04-01

    We present the main features of a home-built scanning tunneling microscope that has been attached to the mixing chamber of a dilution refrigerator. It allows scanning tunneling microscopy and spectroscopy measurements down to the base temperature of the cryostat, T approximately 30 mK, and in applied magnetic fields up to 13 T. The topography of both highly ordered pyrolytic graphite and the dichalcogenide superconductor NbSe(2) has been imaged with atomic resolution down to T approximately 50 mK as determined from a resistance thermometer adjacent to the sample. As a test for a successful operation in magnetic fields, the flux-line lattice of superconducting NbSe(2) in low magnetic fields has been studied. The lattice constant of the Abrikosov lattice shows the expected field dependence proportional to 1/square root of B and measurements in the scanning tunneling spectroscopy mode clearly show the superconductive density of states with Andreev bound states in the vortex core. PMID:20441363

  3. A study of surfaces using a scanning tunneling microscope (STM

    Alba Graciela Ávila Bernal

    2010-05-01

    Full Text Available Sweeping/scanning microscopes have become an experimental scientist’s hands and eyes in this century; they have become a powerful and necessary tool for nanoscale characterisation in education and research laboratories all around the world. This arti- cle presents the modifications made in the mechanical (isolation or designing an anti-vibration system and electrical (piezoelec- tric and scanning system characterisation implementation of a scanning tunnelling microscope (STM, thereby allowing nanosca- le surfaces to be visualised and modified. A methodology for visualising and characterising surfaces using the aforementioned instrument is described, bidimensional quantification of up to 1,300 nm2, with ~15 nm resolution being reached. This experi- mental methodology took critical parameters for tunnelling current stability into account, such as scanning speed and microscope tip geometry and dimensions. This microscope’s versatility allowed defects in highly oriented pyrolytic graphite (HOPG samples to be modified and visualised by applying a voltage between the tip and the sample. The concepts of topography scanning and lithography can be easily understood by using the instrument implemented here.

  4. Low-current Scanning Tunneling Microscope for Nanoscale Imaging

    R.K. Kale

    2006-10-01

    Full Text Available Advances in the nanotechnology, which is still in its infancy, will depend on our ability todesign, build, replicate, and mass-produce usable nanoscale systems. At sub-nanometer lengthscales, scanning tunneling microscopy (STM and the related techniques, collectively calledscanning probe microscopies, replace the optical microscopy for real-space imaging andmanipulation of materials. STM operation is based on measurement of current due to tunnelingof electrons across a finite potential barrier between the probe and the sample. In conventionalSTM, tunneling current of tens of nA and probe-sample distance of a few Å are maintained.These conditions, while necessary for atomic-scale imaging under ultra high vacuum environment,are not suited to handle nanostructures. Quantum structures deposited on a flat substrate usuallypresent a non-metallic sample, and the roughness levels involved are much too high forconventional STM. STM operation with low tunneling current (few pA and larger tunneling gap(several nm is preferred to overcome these difficulties. This paper presents experimental workand theoretical considerations for developing an atmospheric low-current STM (LC-STM.Researchers from diverse fields can build their own LC-STM for routine imaging and spectroscopy.Several design details are included keeping this aspect in mind.

  5. Bases for time-resolved probing of transient carrier dynamics by optical pump-probe scanning tunneling microscopy

    Yokota, Munenori; Yoshida, Shoji; Mera, Yutaka; Takeuchi, Osamu; Oigawa, Haruhiro; Shigekawa, Hidemi

    2013-09-01

    The tangled mechanism that produces optical pump-probe scanning tunneling microscopy spectra from semiconductors was analyzed by comparing model simulation data with experimental data. The nonlinearities reflected in the spectra, namely, the excitations generated by paired laser pulses with a delay time, the logarithmic relationship between carrier density and surface photovoltage (SPV), and the effect of the change in tunneling barrier height depending on SPV, were examined along with the delay-time-dependent integration process used in measurement. The optimum conditions required to realize reliable measurement, as well as the validity of the microscopy technique, were demonstrated for the first time.

  6. Theory and feasibility tests for a seismic scanning tunnelling macroscope

    Schuster, Gerard T.

    2012-09-01

    We propose a seismic scanning tunnelling macroscope (SSTM) that can detect subwavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the scatterer is in the near-field region. This means that, as the scatterer approaches the source, imaging of the scatterer with super-resolution can be achieved. Acoustic and elastic simulations support this concept, and a seismic experiment in an Arizona tunnel shows a TRM profile with super-resolution adjacent to the fault location. The SSTM is analogous to the optical scanning tunnelling microscopes having subwavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by the imaging of near-field seismic energy.

  7. SPATIAL REPARTITION OF CURRENT FLUCTUATIONS IN A SCANNING TUNNELING MICROSCOPE

    Jerome Lagoute

    2011-05-01

    Full Text Available Scanning Tunneling Microscopy (STM is a technique where the surface topography of a conducting sample is probed by a scanning metallic tip. The tip-to-surface distance is controlled by monitoring the electronic tunneling current between the two metals. The aim of this work is to extend the temporal range of this instrument by characterising the time fluctuations of this current on different surfaces. The current noise power spectral density is dominated by a characteristic 1/f component, the physical origin of which is not yet clearly identified, despite a number of investigations. A new I-V preamplifier was developed in order to characterise these fluctuations of the tunnelling current and to obtain images of their spatial repartition. It is observed that their intensity is correlated with some topographical features. This information can be used to get insights on the physical phenomena involved that are not accessible by the usual STM set-up, which is limited to low frequencies.

  8. Scanning Tunneling Microscopy Studies of Superconductor Proximity Systems

    Scanning tunneling microscopy and spectroscopy are employed in order to investigate with nanometer spatial resolution the superconductor proximity effect. The samples are novel superconducting wires consisting of ordered arrays of sub-micron diameter normal metal (N) filaments, either Cu or Ni, embedded in a superconducting (S) NbTi matrix. Two main issues are addressed: 1) The evolution of the superconductor gap as a function of distance from the N/S boundary. We focus on the extent of penetration of superconductivity into N and on the recovery of the gap in S, which is found to occur on a scale much larger than expected. 2) Effects resulting from multiple Andreev reflections at the boundaries between the different constituents, namely, quasi-particle bound states and Tomasch oscillations. Such effects have not been previously studied in a geometry where tunneling takes place in parallel to the N/S interfaces

  9. Scanning Tunneling Electron Transport into a Kondo Lattice

    Yang, Fu-Bin; Wu, Hua

    2016-05-01

    We theoretically present the results for a scanning tunneling transport between a metallic tip and a Kondo lattice. We calculate the density of states (DOS) and the tunneling current and differential conductance (DC) under different conduction-fermion band hybridization and temperature in the Kondo lattice. It is found that the hybridization strength and temperature give asymmetric coherent peaks in the DOS separated by the Fermi energy. The corresponding current and DC intensity depend on the temperature and quantum interference effect among the c-electron and f-electron states in the Kondo lattice. Supported by the National Natural Science Foundation of China under Grant No. 11547203, and the Research Project of Education Department in Sichuan Province of China under Grant No. 15ZB0457

  10. Optical and Electrical Characterization at the Nanoscale by a Transparent Tip of a Scanning Tunneling Microscope

    Sychugov, Ilya; Omi, Hiroo; Murashita, Toru; KOBAYASHI, Yoshihiro

    2009-01-01

    A new type of scanning probe microscope, combining features of the scanning tunnelling microscope, the scanning tunnelling luminescence microscope with a transparent probe and the aperture scanning near-field optical microscope, is described. Proof-of-concept experiments were performed under ultrahigh vacuum conditions at varying temperature on GaAs/AlAs heterostructures.

  11. Challenges in cross-sectional scanning tunneling microscopy on semiconductors

    Cross sectional scanning tunneling microscopy (X-STM) has now become a well established method for the investigation of the structural and electronic properties of semiconductor nano-structures down to the scale of individual impurity atoms. Nevertheless, some aspects still remain challenging, for example in the sample preparation by cleavage as well as in the quantitative interpretation of the results. We present a brief overview of the techniques and geometries employed to cleave different semiconductors such as the lll-V materials, mainly GaAs, and the elementary semiconductors Si and Ge. Furthermore, we discuss the inevitable impact of the surface on the properties of the addressed impurities. This is mainly an issue when the surface reconstruction creates electronic surface states in the band gap. But also the unreconstructed GaAs(110) surface significantly modifies the symmetry of acceptor wave functions and the binding energy of donors and acceptors in the first few atomic layers. The impact of the tip will be addressed as a third quite important challenge, which is frequently neglected in the analysis of X-STM data. On surfaces with an unpinned Fermi level, the presence of the STM tip and the voltage applied to the tunneling contact significantly modifies the spectral positions of the observed electronic states and bands. Furthermore, different band bending situations open up qualitatively different tunneling paths to address individual electronic states in the sample. Detailed knowledge of the tunneling mechanism and of the tip properties, mainly apex radius and work function, is required in order to correctly extract the energetic levels from the tunneling spectroscopy data

  12. STM beyond vacuum tunneling : scanning tunneling hydrogen microscopy as a route to ultra-high resolution

    Weiss, Christian

    2012-01-01

    Direct imaging is a fast and reliable method for the characterization of surfaces. When it comes to small surface structures in the size of the features e.g. in todays computer processors, classical optical imaging methods fail in resolving these structures. With the invention of the scanning tunnelling microscope (STM) for the first time it became possible to image the structure of surfaces with atomic precision. However, the STM fails in resolving complex chemical structures ...

  13. Reinterpretation of Scanning Tunneling Microscopy on an Adsorbed Magnetic Atom

    Hong, Jongbae

    2009-01-01

    The observation of the Kondo effect in mesoscopic systems under bias$^{1,2}$ has opened a new chapter in the physics of the Kondo phenomenon. Various types of $dI/dV$, where $I$ and $V$ denote current and source-drain (s-d) bias, respectively, line shapes have been measured by scanning tunneling microscopy (STM)$^{1,3-11}$. However, explanation by single Fano line shape$^{1,12-16}$ is not relevant and even misleading. Here, we provide consistent explanations for various asymmetric and symmetr...

  14. Electric field effects in scanning tunneling microscope imaging

    Stokbro, Kurt; Quaade, Ulrich; Grey, Francois

    1998-01-01

    We present a high-voltage extension of the Tersoff-Hamann theory of scanning tunneling microscope (STM) images, which includes the effect of the electric field between the tip and the sample. The theoretical model is based on first-principles electronic structure calculations and has no adjustable...... parameters. We use the method to calculate theoretical STM images of the monohydrate Si(100)-H(2x1) surface with missing hydrogen defects at -2V and find an enhanced corrugation due to the electric field, in good agreement with experimental images....

  15. Scanning tunneling microscopy on rough surfaces-quantitative image analysis

    Reiss, G.; Brückl, H.; Vancea, J.; Lecheler, R.; Hastreiter, E.

    1991-07-01

    In this communication, the application of scanning tunneling microscopy (STM) for a quantitative evaluation of roughnesses and mean island sizes of polycrystalline thin films is discussed. Provided strong conditions concerning the resolution are satisfied, the results are in good agreement with standard techniques as, for example, transmission electron microscopy. Owing to its high resolution, STM can supply a better characterization of surfaces than established methods, especially concerning the roughness. Microscopic interpretations of surface dependent physical properties thus can be considerably improved by a quantitative analysis of STM images.

  16. Synchrotron X-ray Enhanced Scanning Tunneling Microscopy

    Rose, Volker; Freeland, John

    2011-03-01

    Proper understanding of complex phenomena occurring in nanostructures requires tools with both the ability to resolve the nanometer scale as well as provide detailed information about chemical, electronic, and magnetic structure. Scanning tunneling microscopy (STM) achieves the requisite high spatial resolution; however, direct elemental determination is not easily accomplished. X-ray microscopies, on the other hand, provide elemental selectivity, but currently have spatial resolution only of tens of nanometers. We present a novel and radically different concept that employs detection of local synchrotron x-ray interactions utilizing a STM that provides spatial resolution, and x-ray absorption directly yields chemical, electronic, and magnetic sensitivity. If during tunneling the sample is simultaneously illuminated with monochromatic x-rays, characteristic absorption will arise. Electrons that are excited into unoccupied levels close to the Fermi level modulate the tunneling current giving rise to elemental contrast. This work was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract DE-AC02-06CH11357.

  17. From Graphite to Graphene via Scanning Tunneling Microscopy

    Qi, Dejun

    The primary objective of this dissertation is to study both graphene on graphite and pristine freestanding grapheme using scanning tunneling microscopy (STM) and density functional theory (DFT) simulation technique. In the experiment part, good quality tungsten metalic tips for experiment were fabricated using our newly developed tip making setup. Then a series of measurements using a technique called electrostatic-manipulation scanning tunneling microscopy (EM-STM) of our own development were performed on a highly oriented pyrolytic graphite (HOPG) surface. The electrostatic interaction between the STM tip and the sample can be tuned to produce both reversible and irreversible large-scale movement of the graphite surface. Under this influence, atomic-resolution STM images reveal that a continuous electronic transition between two distinct patterns can be systematically controlled. DFT calculations reveal that this transition can be related to vertical displacements of the top layer of graphite relative to the bulk. Evidence for horizontal shifts in the top layer of graphite is also presented. Excellent agreement is found between experimental STM images and those simulated using DFT. In addition, the EM-STM technique was also used to controllably and reversibly pull freestanding graphene membranes up to 35 nm from their equilibrium height. Atomic-scale corrugation amplitudes 20 times larger than the STM electronic corrugation for graphene on a substrate were observed. The freestanding graphene membrane responds to a local attractive force created at the STM tip as a highly conductive yet flexible grounding plane with an elastic restoring force.

  18. Scanning electron and tunneling microscopy of palladium-barium emitters

    The results of study of metal-alloyed palladium-barium emitters' of modern very high frequency high-powered electronic vacuum tubes by scanning electron microscopy (SEM) and scanning tunneling microscopy/spectroscopy (STM/STS) are presented. Since the Pd/Ba foil surface is fairly smooth and is not oxidized in air STM/STS investigations are carried out in air in normal laboratory environment. SEM and STM images show that the emitter surface has a complex porous structure. The cathode surface study by STS in tunneling gap modulation mode allowed to take a map of phase distribution with various work function values and high lateral resolution. Obtained images demonstrate the presence of three phases on the Pd/Ba emitter surface, viz. barium-oxygen compounds, intermetallic, and palladium. As it is seen from presented STS image the phase with a low work function value (barium oxides) is concentrated along boundaries of the substance inclusions with work function corresponding to the intemetallic compound Pd5Ba. This supports the model of low work function areas obtained via Ba segregation from the intermetallic compound and oxidation. The presented methods may be used in the Pd/Ba cathode manufacturing process for increasing the yield of electronic devices in microwave tube production and optimize the emitters' characteristics

  19. Piezoresistive cantilevers utilized for scanning tunneling and scanning force microscope in ultrahigh vacuum

    Giessibl, Franz J.; Trafas, B. M.

    1994-01-01

    Piezoresistive cantilevers have been utilized in a novel ultrahigh vacuum scanning probe microscope which allows in situscanning tunneling microscopy(STM), contact atomic force microscopy(AFM), and noncontact atomic force microscopy. The instrument uses interchangeable tungsten tips (for STM imaging) and piezoresistive cantilevers (for AFM or STM imaging) and is capable of atomic resolution in both STM and AFM modes of operation. In situ tip exchange under vacuum conditions is performed quick...

  20. Measurement of shear strength for HOPG with scanning tunneling microscopy by thermal excitation method

    An experimental observation of force interactions in scanning tunneling microscopy (STM) is presented. A technique for measuring force interactions between a conventional STM probe and a sample by spectra analysis of its thermal fluctuations from tunneling current in STM is developed theoretically and experimentally. Thermally excited fluctuation of the STM probe is exactly discerned in air and then force gradient is determined from its corresponding eigen-frequency with a formula similar to that for a small-amplitude atomic force microscopy (AFM). The observed force interactions are consistent with forces in dynamic AFM. Shear strength of 7 GPa for highly oriented pyrolytic graphite (HOPG) under compressive stress is obtained from the experiment and using the elastic theory. We believe that this technique is of scientific significance as it enables accurate measurement of short-range force interactions at atomic scale under true STM conditions. -- Research highlights: ► An experimental observation of force interactions in conventional STM. ► Thermally excited vibration mode in an STM tip used as a shear force sensor. ► Spectra analysis of the thermal fluctuations of the probe from tunneling current. ► Shear strength of 7 Gpa for HOPG is obtained under compressive stress. ► Stimulating ideas for the measurement of short-range forces at atomic scale.

  1. Scanning tunneling microscopy of atomically precise graphene nanoribbons exfoliated onto H:Si(100)

    Radocea, Adrian; Mehdi Pour, Mohammad; Vo, Timothy; Shekhirev, Mikhail; Sinitskii, Alexander; Lyding, Joseph

    Atomically precise graphene nanoribbons (GNRs) are promising materials for next generation transistors due to their well-controlled bandgaps and the high thermal conductivity of graphene. The solution synthesis of graphene nanoribbons offers a pathway towards scalable manufacturing. While scanning tunneling microscopy (STM) can access size scales required for characterization, solvent residue increases experimental difficulty and precludes band-gap determination via scanning tunneling spectroscopy (STS). Our work addresses this challenge through a dry contact transfer method that cleanly transfers solution-synthesized GNRs onto H:Si(100) under UHV using a fiberglass applicator. The semiconducting silicon surface avoids problems with image charge screening enabling intrinsic bandgap measurements. We characterize the nanoribbons using STM and STS. For chevron GNRs, we find a 1.6 eV bandgap, in agreement with computational modeling, and map the electronic structure spatially with detailed spectra lines and current imaging tunneling spectroscopy. Mapping the electronic structure of graphene nanoribbons is an important step towards taking advantage of the ability to form atomically precise nanoribbons and finely tune their properties.

  2. Design and performance of a beetle-type double-tip scanning tunneling microscope

    Jaschinsky, P.; Coenen, P.; Pirug, G.; Voigtländer, B.

    2006-01-01

    A combination of a double-tip scanning tunneling microscope with a scanning electron microscope in ultrahigh vacuum environment is presented. The compact beetle-type design made it possible to integrate two independently driven scanning tunneling microscopes in a small space. Moreover, an additional level for coarse movement allows the decoupling of the translation and approach of the tunneling tip. The position of the two tips can be controlled from the millimeter scale down to 50 nm with th...

  3. Inelastic electron tunneling spectroscopy with a dilution refrigerator based scanning tunneling microscope

    This paper presents the design and operations of a compact cryogenic scanning tunneling microscope system combined with a dilution refrigerator. We obtained a minimum temperature of 260 mK at the sample position. Taking advantage of low-temperature measurement for the spectroscopy, inelastic electron tunneling spectroscopy (IETS) at 4.4 K was demonstrated for the octanethiol molecules in a self-assembled monolayer. The spectrum showed many vibrational features as in the case of a high-resolution electron energy loss spectroscopy. We discuss the resolution of the IET signals focusing on its changes with the modulation voltage and the sample temperature. IETS at 260 mK is also presented with similar quality as in the case of 4.4 K, indicating that the vibration-dumping methods for the operation of the dilution refrigerator described in this paper are adequate

  4. Fully low voltage and large area searching scanning tunneling microscope

    We present a novel scanning tunneling microscope (STM), which allows the tip to travel a large distance (millimeters) on the sample and take images (to find microscopic targets) anywhere it reaches without losing atomic resolution. This broad range searching capability, together with the coarse approach and scan motion, is all done with only one single piezoelectric tube scanner as well as with only low voltages (<15 V). Simple structure, low interference and high precision are thus achieved. To this end, a pillar and a tube scanner are mounted in parallel on a base with one ball glued on the pillar top and two balls glued on the scanner top. These three balls form a narrow triangle, which supports a triangular slider piece. By inertial stepping, the scanner can move the slider toward the pillar (coarse approach) or rotate the slider about the pillar (travel along sample surface). Since all the stepping motions are driven by the scanner's lateral bending which is large per unit voltage, high voltages are unnecessary. The technology is also applicable to scanning force microscopes (SFM) such as atomic force microscopes (AFM), etc

  5. Molecular tips for scanning tunneling microscopy: intermolecular electron tunneling for single-molecule recognition and electronics.

    Nishino, Tomoaki

    2014-01-01

    This paper reviews the development of molecular tips for scanning tunneling microscopy (STM). Molecular tips offer many advantages: first is their ability to perform chemically selective imaging because of chemical interactions between the sample and the molecular tip, thus improving a major drawback of conventional STM. Rational design of the molecular tip allows sophisticated chemical recognition; e.g., chiral recognition and selective visualization of atomic defects in carbon nanotubes. Another advantage is that they provide a unique method to quantify electron transfer between single molecules. Understanding such electron transfer is mandatory for the realization of molecular electronics. PMID:24420248

  6. Infrared emission from tunneling electrons: The end of the rainbow in scanning tunneling microscopy

    Boyle, Michael; Mitra, Joy; Dawson, Paul

    2009-01-01

    Electromagnetic radiation originating with localized surface plasmons in the metal-tip/metal-sample nanocavity of a scanning tunneling microscope is demonstrated to extend to a wavelength lambda of at least 1.7 mu m. Progressive spectral extension beyond lambda similar to 1.0 mu m occurs for increasing tip radius above similar to 15 nm, reaching lambda similar to 1.7 mu m for tip radius similar to 100 nm; these observations are corroborated by use of a simple physical model that relates the d...

  7. Spin excitations and correlations in scanning tunneling spectroscopy

    Ternes, Markus

    2015-06-01

    In recent years inelastic spin-flip spectroscopy using a low-temperature scanning tunneling microscope has been a very successful tool for studying not only individual spins but also complex coupled systems. When these systems interact with the electrons of the supporting substrate correlated many-particle states can emerge, making them ideal prototypical quantum systems. The spin systems, which can be constructed by arranging individual atoms on appropriate surfaces or embedded in synthesized molecular structures, can reveal very rich spectral features. Up to now the spectral complexity has only been partly described. This manuscript shows that perturbation theory enables one to describe the tunneling transport, reproducing the differential conductance with surprisingly high accuracy. Well established scattering models, which include Kondo-like spin-spin and potential interactions, are expanded to enable calculation of arbitrary complex spin systems in reasonable time scale and the extraction of important physical properties. The emergence of correlations between spins and, in particular, between the localized spins and the supporting bath electrons are discussed and related to experimentally tunable parameters. These results might stimulate new experiments by providing experimentalists with an easily applicable modeling tool.

  8. High-resolution scanning tunneling microscopy for molecules

    Scanning tunneling microscopy (STM) can detect individual molecular configuration with its high spatial resolution ability, but some intrinsical and extrinsic factors result in the complexities of STM imaging of single molecules. By combining STM experimental work and theoretical simulation with the local density approximation based on Bardeen perturbation method, we have explored the atomic-scale configuration of the following molecular systems: C60 molecules adsorbed on Si(1 1 1)-(7x7); alkanethiol self-assembly monolayers on Au(1 1 1); C60 molecule imaged by STM tip adsorbed with another C60 molecule; O2 molecule adsorbed on Ag(1 1 0) and CO molecule adsorbed on Cu(1 1 1) imaged by CO chemically modified STM tip. Some related problems including: molecule-substrate interactions, STM imaging mechanism, chemically modified STM tip, etc., are discussed

  9. Scanning tunneling microscopy and spectroscopy at very low temperatures

    During past decades, an increasing number of laboratories is using cryogenic scanning tunneling microscopy and spectroscopy (STM/S) to probe different kinds of electronic systems. Measurements in a dilution refrigerator are particularly useful to study superconductors, because temperatures of order of 100 mK are well below most critical temperatures and effectively reduce thermally excited quasiparticles. The local electronic density of states is then obtained at atomic level with a resolution in energy of some tens of μeV. Visualizing spatial variations of the local density of states allows characterizing vortex cores and the vortex lattice. Vortex core electronic features provide the anisotropy of the superconducting properties, and help understanding the influence of competing orders such as charge density waves. Here we will review results in dichalcogenide superconductors, in the magnetic borocarbide TmNi2B2C and in thin films, discussing in some detail a few relevant aspects of thermal depinning and melting in thin films

  10. A high stability and repeatability electrochemical scanning tunneling microscope

    Xia, Zhigang; Wang, Jihao; Lu, Qingyou, E-mail: qxl@ustc.edu.cn [High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui 230026 (China); Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Hou, Yubin [High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2014-12-15

    We present a home built electrochemical scanning tunneling microscope (ECSTM) with very high stability and repeatability. Its coarse approach is driven by a closely stacked piezo motor of GeckoDrive type with four rigid clamping points, which enhances the rigidity, compactness, and stability greatly. It can give high clarity atomic resolution images without sound and vibration isolations. Its drifting rates in XY and Z directions in solution are as low as 84 pm/min and 59 pm/min, respectively. In addition, repeatable coarse approaches in solution within 2 mm travel distance show a lateral deviation less than 50 nm. The gas environment can be well controlled to lower the evaporation rate of the cell, thus reducing the contamination and elongating the measurement time. Atomically resolved SO{sub 4}{sup 2−} image on Au (111) work electrode is demonstrated to show the performance of the ECSTM.

  11. A high stability and repeatability electrochemical scanning tunneling microscope

    We present a home built electrochemical scanning tunneling microscope (ECSTM) with very high stability and repeatability. Its coarse approach is driven by a closely stacked piezo motor of GeckoDrive type with four rigid clamping points, which enhances the rigidity, compactness, and stability greatly. It can give high clarity atomic resolution images without sound and vibration isolations. Its drifting rates in XY and Z directions in solution are as low as 84 pm/min and 59 pm/min, respectively. In addition, repeatable coarse approaches in solution within 2 mm travel distance show a lateral deviation less than 50 nm. The gas environment can be well controlled to lower the evaporation rate of the cell, thus reducing the contamination and elongating the measurement time. Atomically resolved SO42− image on Au (111) work electrode is demonstrated to show the performance of the ECSTM

  12. Extracting the Rashba splitting from scanning tunneling microscopy measurements

    The Rashba-type spin-splitting found in many two-dimensional electron systems at surfaces is a band splitting in momentum, which is most easily extracted from angular resolved photoemission data. Scanning tunneling microscopy as a real-space resolving technique relies on quasiparticle interference to extract momentum information about the experimental electronic structure. However, the lifted spin degeneracy in the Rashba split bands imposes a selection rule that makes it impossible to extract the Rashba splitting from single scattering events, e.g. scattering from a point defect in STM data. Nevertheless, going beyond single scattering events, the Rashba-type spin splitting can be extracted from STM data, which will be discussed in this review

  13. Fault detection by surface seismic scanning tunneling macroscope: Field test

    Hanafy, Sherif M.

    2014-08-05

    The seismic scanning tunneling macroscope (SSTM) is proposed for detecting the presence of near-surface impedance anomalies and faults. Results with synthetic data are consistent with theory in that scatterers closer to the surface provide brighter SSTM profiles than those that are deeper. The SSTM profiles show superresolution detection if the scatterers are in the near-field region of the recording line. The field data tests near Gulf of Aqaba, Haql, KSA clearly show the presence of the observable fault scarp, and identify the subsurface presence of the hidden faults indicated in the tomograms. Superresolution detection of the fault is achieved, even when the 35 Hz data are lowpass filtered to the 5-10 Hz band.

  14. Scanning tunneling microscopy of the cleavage surface of bismuth crystals

    The results of in situ studies of the surface structure of the cleavages of bismuth crystals by the method of scanning tunneling microscopy are presented. It is established that cleavage 'opens' the (111) surface with atomically smooth terraces of diatomic steps whose heights are equal to 0.4 nm or a multiple of this value. If the cleavage is made at room temperature, the boundaries of the terraces are usually curved and diffuse owing to the thermal motion with the activation energy of ∼700 K. The cleavage at liquid nitrogen or helium temperatures provides the formation of straight boundaries along the atomic rows on the surface. Twin interlayers of the quantized width of ∼7 nm are revealed. This width value indicates that the atomic planes on both sides of such interlayers intergrow with the interlayer planes inclined to them at a small angle

  15. Scanning tunneling spectroscopy on low- and high-Tc superconductors

    Using some sophisticated modes of scanning tunneling spectroscopy the local density of states on two superconducting compounds in the superconductive state at 4.2 K were analyzed. On NbSe2 which is a type-II low-Tc material, the Abrikosov flux line lattice was imaged for various external magnetic fields up to BC2. The field-induced decrease of the vortex core radius for increasing magnetic field, which was recently predicted by a microscopic theory, could be clearly verified. On sputtered YBa2Cu3O7-δ films the measurements yielded some distinct types of the surface density of states involving gaps, being in accordance to the Bardeen endash Cooper endash Schrieffer theory, unexpectedly large gaps, Coulomb staircases, and zero-bias peaks. copyright 1996 American Vacuum Society

  16. Electrical characterization of ZnO ceramics by scanning tunneling spectroscopy and beam-induced current in the scanning tunneling microscope

    Díaz-Guerra Viejo, Carlos; Piqueras de Noriega, Javier

    1999-01-01

    A correlative study of the electrically active grain boundary structure of ZnO polycrystals has been carried out using a scanning electron microscope/scanning tunneling microscope (SEM/STM) combined instrument. Current imaging tunneling spectroscopy (CITS) measurements reveal reduced surface band gaps, as compared with grain interiors, at the charged boundaries imaged by SEM-based remote electron beam induced current (REBIC). ZnO grain boundaries were also imaged in the STM-REBIC mode with a ...

  17. Josephson Effect in Pb/I/NbSe2 Scanning Tunneling Microscope Junctions

    Naaman, O.; Dynes, R. C.; Bucher, E.

    2003-01-01

    We have developed a method for the reproducible fabrication of superconducting scanning tunneling microscope (STM) tips. We use these tips to form superconductor/insulator/superconductor tunnel junctions with the STM tip as one of the electrodes. We show that such junctions exhibit fluctuation dominated Josephson effects, and describe how the Josephson product IcRn can be inferred from the junctions' tunneling characteristics in this regime. This is first demonstrated for tunneling into Pb fi...

  18. Scanning tunneling microscopy and spectroscopy of sidewall functionalized singlewalled carbon nanotubes

    Vencelova, Andrea

    2007-01-01

    The structural and electronic properties of single walled carbon nanotubes (SWCNTs) were investigated in this thesis via scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Study and estimation of the intrinsic properties of SWCNTs was the most important task. Further, the impact of different purification methods as well as functionalization by Li-organic compounds on carbon nanotubes was analyzed.

  19. Imaging of buried phosphorus nanostructures in silicon using scanning tunneling microscopy

    Oberbeck, L.; Reusch, T. C. G.; Hallam, T.; Schofield, S.R.; Curson, N. J.; Simmons, M. Y.

    2014-01-01

    We demonstrate the locating and imaging of single phosphorus atoms and phosphorus dopant nanostructures, buried beneath the Si(001) surface using scanning tunneling microscopy. The buried dopant nanostructures have been fabricated in a bottom-up approach using scanning tunneling microscope lithography on Si(001). We find that current imaging tunneling spectroscopy is suited to locate and image buried nanostructures at room temperature and with residual surface roughness present. From these st...

  20. Combined scanning force microscopy and scanning tunneling spectroscopy of an electronic nano-circuit at very low temperature

    Senzier, Julien; Luo, Pengshun; Courtois, Hervé

    2007-01-01

    We demonstrate the combination of scanning force microscopy and scanning tunneling spectroscopy in a local probe microscope operating at very low temperature (60 mK). This local probe uses a quartz tuning fork ensuring high tunnel junction stability. We performed the spatially-resolved spectroscopic study of a superconducting nano-circuit patterned on an insulating substrate. Significant deviations from the BCS prediction are observed.

  1. Advances in Atomic Force Microscopy and Scanning Tunneling Microscopy

    Albrecht, Thomas Robert

    The scanning tunneling microscope (STM) and the more recently developed atomic force microscope (AFM) are high resolution scanning probe microscopes capable of three dimensional atomic-scale surface profiling. In the AFM, minute forces acting between the tip of a flexible cantilever stylus and the surface of the sample cause deflections of the cantilever which are detected by a tunneling or optical sensor with subangstrom sensitivity. The AFM work presented here involves surface profiling via repulsive contact forces between 10^{-6} and 10^{-9} N in magnitude. In this contact profiling (repulsive) mode the AFM is capable of atomic resolution on both electrically conducting and insulating surfaces (unlike the STM). AFM instrumentation for room temperature and low temperature operation is discussed. The critical component of the AFM is the cantilever stylus assembly, which should have a small mass. Several microfabrication processes have been developed to produce thin film SiO_2 and Si_3N_4 microcantilevers with integrated sharp tips. Atomic resolution has been achieved with the AFM in air on a number of samples, including graphite, MoS _2, TaSe_2, WTe_2, TaS_2, and BN (the first insulator imaged with atomic resolution by any means). Various organic and molecular samples have been imaged with nanometer resolution. The difference between STM and AFM response is shown in images of TaS _2 (a charge density wave material), and in simultaneous STM/AFM images of lattice defects and adsorbates on graphite and MoS_2. A number of artifacts make STM and AFM image interpretation subtle, such as tip shape effects, frictional effects, and tracking in atomic grooves. STM images of moire patterns near grain boundaries confirm the importance of tip shape effects. Various surface modification and lithography techniques have been demonstrated with the STM and AFM, including an STM voltage pulse technique which reproducibly creates 40 A diameter holes on the surface of graphite, and a

  2. Scanning Tunneling Spectroscopy on InAs-GaSb Esaki Diode Nanowire Devices during Operation.

    Persson, Olof; Webb, James L; Dick, Kimberly A; Thelander, Claes; Mikkelsen, Anders; Timm, Rainer

    2015-06-10

    Using a scanning tunneling and atomic force microscope combined with in-vacuum atomic hydrogen cleaning we demonstrate stable scanning tunneling spectroscopy (STS) with nanoscale resolution on electrically active nanowire devices in the common lateral configuration. We use this method to map out the surface density of states on both the GaSb and InAs segments of GaSb-InAs Esaki diodes as well as the transition region between the two segments. Generally the surface shows small bandgaps centered around the Fermi level, which is attributed to a thin multielement surface layer, except in the diode transition region where we observe a sudden broadening of the bandgap. By applying a bias to the nanowire we find that the STS spectra shift according to the local nanoscale potential drop inside the wire. Importantly, this shows that we have a nanoscale probe with which we can infer both surface electronic structure and the local potential inside the nanowire and we can connect this information directly to the performance of the imaged device. PMID:25927249

  3. Cross-section scanning tunneling spectroscopy on a resonant-tunneling diode structure

    Teichmann, Karen; Wenderoth, Martin; Burbach, Sergej; Ulbrich, Rainer G. [IV. Physikalisches Institut, Georg-August Universitaet Goettingen (Germany); Pierz, Klaus; Schumacher, Hans W. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

    2010-07-01

    We investigated a resonant-tunneling diode structure by cross-sectional scanning tunneling microscopy (STM) and spectroscopy. The diode structure was grown by molecular-beam epitaxy on a n{sup +}-doped GaAs (100) substrate and consists of self-assembled InAs quantum dots embedded in AlAs barriers (both 4 nm) each followed by undoped GaAs prelayers (15 nm). We use a low temperature STM working under UHV conditions at 5 K. The samples are cleaved in UHV to obtain a clean and atomically flat surface perpendicular to the diode-structure. Atomically resolved constant current topography images taken simultaneously at different bias voltages, (both positive and negative voltage) show the high quality of the heterostructure. Local I(V)-spectroscopy resolves the band edge alignment across the heterostructure. On negative bias voltage several peaks in the differential conductivity are observed. The voltage position of these peaks varies with distance from the interface. We attribute the origin of the enhanced differential conductivity peak to an interaction between the potential induced by the tip and the quantum dot layer.

  4. Scanning tunneling microscope with long range lateral motion

    We present our work on a recently built scanning tunneling microscope (STM), with coarse motion in two-dimensions. The tip of this STM can be translated a few millimeters in directions both parallel and perpendicular to the tip. This feature allows sampling of a larger area for experiments such as the study of how the electrical properties of charge density waves evolve between contacts, the proximity effect near a normal metal–superconducting interface, charge transport near the contact of a semiconductor interface, and for finding microscopically small samples like graphene. This STM is based on one of our previous one-dimensional designs. It utilizes orchestrated motion of six piezoelectric tubes in a slip–stick configuration in order to produce long range motion for the walker. This device is a single unit with a compact design making it very stable. It is stable enough to obtain atomic resolution on HOPG. It can operate in either a horizontal or vertical configuration and at cryogenic temperatures. It was designed entirely from non-magnetic materials for potential work in a magnetic field.

  5. Scanning Tunneling Microscopy of DNA-Carbon Nanotube Hybrids

    Yarotski, Dzmitry; Kilina, Svetlana; Talin, Alec; Balatsky, Alexander; Tretiak, Sergei; Taylor, Antoinette

    2009-03-01

    Production of carbon nanotube-based (CNT) devices holds a great promise for bringing the size of electronic circuits down to molecular scales. Recently, yet another step has been made towards achieving this goal by developing a new method for metal-semiconductor CNT separation, which relies on wrapping the CNT with ssDNA molecule[1]. Though it was shown that the outcome of the separation process strongly depends on the DNA sequence, further investigations have to be conducted to determine detailed structure of the hybrids and their electronic properties. Here, we use STM to characterize structural and electronic properties of the CNT-DNA hybrids and compare experimental results to theoretical calculations. STM images reveal 3.3 nm DNA coiling period, which agrees very well with the theoretical predictions. Additional width modulations with characteristic lengths of 1.9 and 2.6 nm are observed along the molecule itself. Although scanning tunneling microscopy confirms the presence of DNA in the hybrid and visualizes its structure, further experimental work is required to reveal the dependence of electronic properties of hybrids on their internal structure. [1] M. Zheng et al., Science 302, 1545 (2004).

  6. Interpretation of scanning tunneling quasiparticle interference and impurity states

    Kreisel, Andreas; Choubey, P.; Berlijn, T.; Andersen, B. M.; Hirschfeld, P. J.

    2015-03-01

    We use a simple method of calculating inhomogeneous, atomic-scale phenomena in superconductors to obtain real-space conductance maps as measured in scanning tunneling spectroscopy (STM). Our approach makes use of first principles Wannier functions in conjunction with self-consistent solutions of the Bogoliubov-de Gennes equations on a lattice to image superconducting phenomena. This method is a powerful tool since it captures correctly local symmetries on the surface that can be lower than the global lattice symmetry; it improves the spatial resolution from one pixel per lattice point to the sub-atomic scale; and simplifies the interpretation of STM data. As an example, we show how the pattern observed around a Zn impurity in BSCCO-2212, can be understood by accounting for the tails of the Cu Wannier functions, and thus compare perfectly to experimental findings. Further applications of this method include the investigation of impurity states in multiorbital systems as well as the study of quasi particle interference phenomena to enable a better understanding of novel phenomena in high temperature superconductors. P.C., A.K., and P.J.H. were supported by DOE DE-FG02-05ER46236, T.B. as a Wigner Fellow at the Oak Ridge National Laboratory, and B.M.A. and A.K. by Lundbeckfond fellowship (Grant A9318).

  7. Scanning Tunneling Microscopy Studies of Diamond Films and Optoelectronic Materials

    Perez, Jose M.

    1996-01-01

    We present a summary of the research, citations of publications resulting from the research and abstracts of such publications. We have made no inventions in the performance of the work in this project. The main goals of the project were to set up a Chemical Vapor Deposition (CVD) diamond growth system attached to an UltraHigh Vacuum (UHV) atomic resolution Scanning Tunneling Microscopy (STM) system and carry out experiments aimed at studying the properties and growth of diamond films using atomic resolution UHV STM. We successfully achieved these goals. We observed, for the first time, the atomic structure of the surface of CVD grown epitaxial diamond (100) films using UHV STM. We studied the effects of atomic hydrogen on the CVD diamond growth process. We studied the electronic properties of the diamond (100) (2x1) surface, and the effect of alkali metal adsorbates such as Cs on the work function of this surface using UHV STM spectroscopy techniques. We also studied, using STM, new electronic materials such as carbon nanotubes and gold nanostructures. This work resulted in four publications in refereed scientific journals and five publications in refereed conference proceedings.

  8. As-rich GaAs(001) surfaces observed during As4-irradition by scanning tunneling microscopy

    Tsukamoto, S; Orr, B G; Ohtake, A; Bell, G R; Koguchi, N; Tsukamoto, Shiro; Pristovsek, Markus; Orr, Bradford G.; Ohtake, Akihiro; Bell, Gavin R.; Koguchi, Nobuyuki

    2002-01-01

    As-rich GaAs (001) surfaces are successfully observed during As4-irradition by a system in which scanning tunneling microscopy (STM) and molecular beam epitaxy can be performed simultaneously. With a substrate temperature of 440 C and an As4 partial pressure of 2x10-6 torr, reflection high energy electron diffraction patterns and reflectance anisotropy spectra confirm a c(4x4) As-stabilized surface. STM images clearly show alteration of the surface reconstructions while scanning. It is postulated that continual attachment / detachment of As molecules to and from the surface produces the observed dynamic behavior.

  9. Scanning tunneling spectroscopy study of erbium doped GaSb crystals

    Hidalgo Alcalde, Pedro; Méndez Martín, Bianchi; Piqueras de Noriega, Javier; Plaza, J.L.; Dieguez, E.

    1999-01-01

    Er doped GaSb single crystals have been studied by scanning tunneling spectroscopy (STS) and cathodoluminescence (CL) in a combined scanning electron microscope-scanning tunnelling microscope system. The surface band gap in doped samples has been found to be about 0.5 eV while in undoped crystals the gap is close to the bulk value. Inhomogeneities in the local electronic properties of the doped crystals are studied by a correlation of the CL images and STS data.

  10. Scanning tunneling spectroscopy of transition-metal-doped GaSb

    Hidalgo Alcalde, Pedro; Méndez Martín, Bianchi; Piqueras de Noriega, Javier; Dutta, P: S.; Dieguez, E.

    1999-01-01

    V- and Ru-doped GaSb crystals have been investigated by scanning tunneling spectroscopy in a combined scanning electron microscope-scanning tunneling microscope system. Local variations of surface band gap have been measured with high spatial resolution. Precipitates in both kinds of doped samples show a nearly metallic behavior. The surface band gaps in the GaSb matrix have been found to depend on the dopant. [S0163-1829(99)06439-5].

  11. Long-range Scanning Tunneling Microscope for the study of nanostructures on insulating substrates

    Molina-Mendoza, Aday; Rodrigo, José Gabriel; Island, Joshua; Burzuri, Enrique; Rubio-Bollinger, Gabino; van der Zant, Herre S J; Agraït, Nicolás

    2013-01-01

    The Scanning Tunneling Microscope is a powerful tool for studying the electronic properties at the atomic level, however it's relatively small scanning range and the fact that it can only operate on conducting samples prevents its application to study heterogeneous samples consisting on conducting and insulating regions. Here we present a long-range scanning tunneling microscope capable of detecting conducting micro and nanostructures on insulating substrates using a technique based on the ca...

  12. Effects of plasmon energetics on light emission induced by scanning tunneling microscopy

    A theoretical model of plasmon and molecular luminescence induced by scanning tunneling microscopy using a molecule-covered tip on clean metal surfaces is developed. The effects of coupling between molecular exciton and interface plasmon on the luminescence spectra are investigated for variable energy of plasmon modes by means of the nonequilibrium Green's function method. It is found that spectral features arising from interference between the processes of energy absorption by the molecule and interface plasmons appear near the energy of the excitonic mode. For the energy of plasmon above (below) the energy of excitonic mode, an additional peak structure appears in the energy range slightly below (above) the energy of the excitonic mode. Prominent peak and dip structures observed in recent luminescence experiments are interpreted by the developed theory whereby its utility in the fields of plasmonics and nanophotonics is demonstrated. (fast track communication)

  13. Electronic Single Molecule Measurements with the Scanning Tunneling Microscope

    Im, Jong One

    Richard Feynman said "There's plenty of room at the bottom". This inspired the techniques to improve the single molecule measurements. Since the first single molecule study was in 1961, it has been developed in various field and evolved into powerful tools to understand chemical and biological property of molecules. This thesis demonstrates electronic single molecule measurement with Scanning Tunneling Microscopy (STM) and two of applications of STM; Break Junction (BJ) and Recognition Tunneling (RT). First, the two series of carotenoid molecules with four different substituents were investigated to show how substituents relate to the conductance and molecular structure. The measured conductance by STM-BJ shows that Nitrogen induces molecular twist of phenyl distal substituents and conductivity increasing rather than Carbon. Also, the conductivity is adjustable by replacing the sort of residues at phenyl substituents. Next, amino acids and peptides were identified through STM-RT. The distribution of the intuitive features (such as amplitude or width) are mostly overlapped and gives only a little bit higher separation probability than random separation. By generating some features in frequency and cepstrum domain, the classification accuracy was dramatically increased. Because of large data size and many features, supporting vector machine (machine learning algorithm for big data) was used to identify the analyte from a data pool of all analytes RT data. The STM-RT opens a possibility of molecular sequencing in single molecule level. Similarly, carbohydrates were studied by STM-RT. Carbohydrates are difficult to read the sequence, due to their huge number of possible isomeric configurations. This study shows that STM-RT can identify not only isomers of mono-saccharides and disaccharides, but also various mono-saccharides from a data pool of eleven analytes. In addition, the binding affinity between recognition molecule and analyte was investigated by comparing with

  14. The atomic force (AFM), scanning tunneling (STM) and scanning force (SFM) microscopies

    This work deals with the atomic force (AFM), scanning tunneling (STM) and scanning force (SFM) microscopies. These analysis methods are based on different physical principles. Nevertheless, in all of them, a probe is situated at a few angstroms or at the direct contact of the studied sample and carries out a controlled scanning of the sample surface. Their physical principles and their running ways are described. Their potentialities and limits are given too. With these analysis methods, and more particularly with the AFM can be observed the crystal structure of isolated biological molecules and the tri dimensional structure of biological molecules which are inserted in artificial membranes. One of the future prospect of the AFM in biology is the direct observation of living cells. Indeed, it will offer the opportunity to follow, with time and in space, the individual cells behaviour and their morphological modifications. Others uses and developments of the AFM concerns the in situ analysis of mechanisms which govern the crystal growth or the direct viewing of a protein enzymatic activity. (O.M.). 37 refs., 7 figs

  15. Scanning tunneling microscopy studies of glucose oxidase on gold surface

    Full text: Three immobilization methods have been used for scanning tunneling microscopy (STM) studies of glucose oxidase (GOD) on gold. They are based on a) physical adsorption from solution, b) microcontact printing and c) covalent bonding onto self-assembled monolayers (SAM) of 3-mercaptopropionic acid (MPA). The STM images are used to provide information about the organization of individual GOD molecules and more densely packed monolayers of GOD on electrode surfaces, thus providing information of the role of interfacial structure on biosensor performance. The use of atomically flat gold substrates enables easy distinction of deposited enzyme features from the flat gold substrate. Microcontact printing is found to be a more reliable method than adsorption from solution for preparing individual GOD molecules on the gold surface STM images of printed samples reveal two different shapes of native GOD molecules. One is a butterfly shape with dimensions of 10 ± 1 nm x 6 ± 1 nm, assigned to the lying position of molecule while the second is an approximately spherical shape with dimensions of 6.5 ± 1 nm x 5 ± 1nm assigned to a standing position. Isolated clusters of 5 to 6 GOD molecules are also observed. With monolayer coverage, GOD molecules exhibit a tendency to organize themselves into a two dimensional array with adequate sample stability to obtain high-resolution STM images. Within these two-dimensional arrays are clearly seen repeating clusters of five to six enzyme molecules in a unit STM imaging of GOD monolayers covalently immobilized onto SAM (MPA) are considerably more difficult than when the enzyme is adsorbed directly onto the metal. Cluster structures are observed both high and low coverage despite the fact that native GOD is a negatively charged molecule. Copyright (2002) Australian Society for Electron Microscopy Inc

  16. Scanning tunnelling microscopy studies of cluster-surface interactions

    The experimental results presented in this thesis explore the interaction of clusters with the graphite surface over three energy regimes of cluster deposition: low (thermal), intermediate and high energy. Thermal evaporation of C60 onto graphite initially results in the nucleation of islands, which subsequently grow to form thin films on the surface. It is demonstrated that the growth of such films is highly dependent upon the cleanliness of the surface and the temperature of the substrate during deposition. It is further suggested that the energetically favoured growth mode is that of an initial bi-layer in preference to a monolayer. Energetic deposition of Ag7- onto graphite is shown to result in the pinning of the cluster to the surface at intermediate energies (∼ 300 eV) and implantation at high energies (> 1000 eV). An oxidative etching technique was used to transform the defects formed through cluster implantation into pits in the surface. Due to the anisotropic reactivity of graphite, these pits grow laterally, yet are known to remain of the same depth as the implanted cluster. Scanning tunnelling microscopy (STM) was used to characterise the depth of the pits and hence allowed the cluster implantation depth to be investigated as a function of the deposition energy. The results demonstrate that, for the case of Ag7-, the implantation depth scales with the velocity of the cluster and not its energy. Additional annealing experiments revealed that the localised damage formed by cluster implantation can be significantly reversed at temperatures substantially lower (923 K) than the melting temperature of graphite (4450 K). (author)

  17. Two-photon Induced Hot Electron Transfer to a Single Molecule in a Scanning Tunneling Microscope

    Wu, Shiwei; Ho, Wilson

    2010-01-01

    The junction of a scanning tunneling microscope (STM) operating in the tunneling regime was irradiated with femtosecond laser pulses. A photo-excited hot electron in the STM tip resonantly tunnels into an excited state of a single molecule on the surface, converting it from the neutral to the anion. The electron transfer rate depends quadratically on the incident laser power, suggesting a two-photon excitation process. This nonlinear optical process is further confirmed by the polarization me...

  18. Surface Relaxations, Current Enhancements, and Absolute Distances in High Resolution Scanning Tunneling Microscopy

    Hofer, W. A.; Fisher, A. J.; Wolkow, R. A.; Gruetter, P.

    2001-01-01

    We have performed the most realistic simulation to date of the operation of a scanning tunneling microscope. Probe-sample distances from beyond tunneling to actual surface contact are covered. We simultaneously calculate forces, atomic displacements, and tunneling currents, allowing quantitative comparison with experimental values. A distance regime below which the probe becomes unstable is identified. It is shown that the real distance differs substantially from previous estimates because of...

  19. The readout of the fullerene-based quantum computing by a scanning tunneling microscope

    Feng, M.; Dong, G. J.; Hu, B.

    2006-01-01

    We consider to detect the electron spin of a doped atom, i.e., a nitrogen or a phosphorus, caged in a fullerene by currently available technique of the scanning tunneling microscope (STM), which actually corresponds to the readout of a qubit in the fullerene-based quantum computing. Under the conditions of polarized STM current and Coulomb blockade, we investigate the tunneling matrix elements involving the exchange coupling between the tunneling polarized electrons and the encapsulated polar...

  20. Light amplification by stimulated emission from an optically pumped molecular junction in a scanning tunneling microscope

    Braun, K; Kern, A. M.; X. Wang; Adler, H.; Peisert, H.; Chasse, T.; Zhang, D.(Department of Physics, The University of Michigan, Ann Arbor, MI, United States of America); Meixner, A.J.

    2013-01-01

    Here, we introduce and experimentally demonstrate optical amplification and stimulated emission from a single optically pumped molecular tunneling junction of a scanning tunneling microscope. The gap between a sharp gold tip and a flat gold substrate covered with a self-assembled monolayer of 5-chloro-2-mercaptobenzothiazole molecules forms an extremely small optical gain medium. When electrons tunnel from the molecules highest occupied molecular orbital to the tip, holes are left behind. The...

  1. Field-Induced Deformation as a Mechanism for Scanning Tunneling Microscopy Based Nanofabrication

    Hansen, Ole; Ravnkilde, Jan Tue; Quaade, Ulrich; Stokbro, Kurt; Grey, Francois

    1998-01-01

    The voltage between tip and sample in a scanning tunneling microscope (STM) results in a large electric field localized near the tip apex. The mechanical stress due to this field can cause appreciable deformation of both tip and sample on the scale of the tunnel gap. We derive an approximate...

  2. Superconducting phonon spectroscopy using a low-temperature scanning tunneling microscope

    LeDuc, H. G.; Kaiser, W J; Hunt, B. D.; Bell, L. D.; Jaklevic, R. C.; Youngquist, M. G.

    1989-01-01

    We report the first observation of phonon density of states effects in a superconductor using a low-temperature scanning tunneling microscope (STM). The phonon effects were observed using a STM spectroscopy method to measure dItunneling /dV vs V for the tunnel junction formed by the Au STM probe and a superconducting Pb sample.

  3. Spectroscopy of surface adsorbed molecules (scanning tunneling microscopy). Progress report, May 1, 1985-April 30, 1986

    A review of the scanning tunneling microscopy program is given. This article contains a description of the design and fabrication of the microscope in addition to description of studies which use the microscope: studies of charge-density waves and studies of tunnel junctions doped with metals and semiconductors. 48 refs., 26 figs

  4. Scanning Tunnelling Spectroscopic Studies of Dirac Fermions in Graphene and Topological Insulators

    wang K.-L.

    2012-03-01

    Full Text Available We report novel properties derived from scanning tunnelling spectroscopic (STS studies of Dirac fermions in graphene and the surface state (SS of a strong topological insulator (STI, Bi2Se3. For mono-layer graphene grown on Cu by chemical vapour deposition (CVD, strain-induced scalar and gauge potentials are manifested by the charging effects and the tunnelling conductance peaks at quantized energies, respectively. Additionally, spontaneous time-reversal symmetry breaking is evidenced by the alternating anti-localization and localization spectra associated with the zero-mode of two sublattices while global time-reversal symmetry is preserved under the presence of pseudo-magnetic fields. For Bi2Se3 epitaxial films grown on Si(111 by molecular beam epitaxy (MBE, spatially localized unitary impurity resonances with sensitive dependence on the energy difference between the Fermi level and the Dirac point are observed for samples thicker than 6 quintuple layers (QL. These findings are characteristic of the SS of a STI and are direct manifestation of strong topological protection against impurities. For samples thinner than 6-QL, STS studies reveal the openup of an energy gap in the SS due to overlaps of wave functions between the surface and interface layers. Additionally, spin-preserving quasiparticle interference wave-vectors are observed, which are consistent with the Rashba-like spin-orbit splitting.

  5. Scanning tunneling microscopy III theory of STM and related scanning probe methods

    Güntherodt, Hans-Joachim

    1993-01-01

    While the first two volumes on Scanning Tunneling Microscopy (STM) and its related scanning probe (SXM) methods have mainly concentrated on intro­ ducing the experimental techniques, as well as their various applications in different research fields, this third volume is exclusively devoted to the theory of STM and related SXM methods. As the experimental techniques including the reproducibility of the experimental results have advanced, more and more theorists have become attracted to focus on issues related to STM and SXM. The increasing effort in the development of theoretical concepts for STM/SXM has led to considerable improvements in understanding the contrast mechanism as well as the experimental conditions necessary to obtain reliable data. Therefore, this third volume on STM/SXM is not written by theorists for theorists, but rather for every scientist who is not satisfied by just obtaining real­ space images of surface structures by STM/SXM. After a brief introduction (Chap. 1), N. D. Lang first co...

  6. Spatio-temporal imaging of voltage pulses with an ultrafast scanning tunneling microscope

    Jensen, Jacob Riis; Keil, Ulrich Dieter Felix; Hvam, Jørn Märcher

    1997-01-01

    Measurements on an ultrafast scanning tunneling microscope with simultaneous spatial and temporal resolution are presented. We show images of picosecond pulses propagating on a coplanar waveguide and resolve their mode structures. The influence of transmission line discontinuities on the mode...

  7. Observation of a Ag protrusion on a Ag2S island using a scanning tunneling microscope

    Takeo Ohno; Tsuyoshi Hasegawa

    2015-01-01

    A silver sulfide (Ag2S) island as an ionic conductor in resistive switching memories was formed and a protrusion of silver from the Ag2S formed by an electrochemical reaction was observed using a scanning tunneling microscope.

  8. Scanning tunneling microscopy of silver containing salt of bis(ethylenedithio)tetrathiafulvalene

    Bai, C.; Dai, C.; Zhu, C. (Changbin); Z. Chen; G Huang; Wu, X; Zhu, D.; Baldeschwieler, John D.

    1990-01-01

    The surface of silver containing salt of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) was studied with the computer-controlled scanning tunneling microscope developed in our laboratory. The crystal surface of the charge-transfer complex is well ordered and a regular array of corrugations is clearly visible. The prominent feature of the experimental scanning tunneling microscopy images is in agreement with the bulk crystal structure obtained by x-ray diffraction method.

  9. The readout of the fullerene-based quantum computing by a scanning tunneling microscope

    Feng, M; Hu, B

    2006-01-01

    We consider to detect the electron spin of a doped atom, i.e., a nitrogen or a phosphorus, caged in a fullerene by currently available technique of the scanning tunneling microscope (STM), which actually corresponds to the readout of a qubit in the fullerene-based quantum computing. Under the conditions of polarized STM current and Coulomb blockade, we investigate the tunneling matrix elements involving the exchange coupling between the tunneling polarized electrons and the encapsulated polarized electron, and calculate the variation of the tunneling current with respect to different orientations of the encapsulated electron spin. The experimental feasibility of our scheme is discussed under the consideration of some imperfect factors.

  10. First-principles theory of inelastic currents in a scanning tunneling microscope

    Stokbro, Kurt; Hu, Ben Yu-Kuang; Thirstrup, C.; Xie, X.C.

    1998-01-01

    the addition of the adsorbate. We use the theory to investigate the vibrational heating of an adsorbate below a scanning tunneling microscopy tip. We calculate the desorption rate of PI from Si(100)-H(2 X 1) as a function of the sample bias and tunnel current, and find excellent a,agreement with......A first-principles theory of inelastic tunneling between a model probe tip and an atom adsorbed on a surface is presented, extending the elastic tunneling theory of Tersoff and Hamann. The inelastic current is proportional to the change in the local density of states at the center of the tip due to...

  11. New approach towards imaging -DNA using scanning tunneling microscopy/spectroscopy (STM/STS)

    Shirshendu Dey; Sushama Pethkar; Suguna D Adyanthaya; Murali Sastry; C V Dharmadhikari

    2008-06-01

    A new methodology to anchor -DNA to silanized -Si(111) surface using Langmuir Blodget trough was developed. The -Si (111) was silanized by treating it with low molecular weight octyltrichlorosilane in toluene. Scanning tunneling microscopy (STM) image of -DNA on octyltrichlorosilane deposited Si substrate shows areas exhibiting arrayed structures of 700 nm length and 40 nm spacing. Scanning tunneling spectroscopy (STS) at different stages depict a broad distribution of defect states in the bandgap region of -Si(111) which presumably facilitates tunneling through otherwise insulating DNA layer.

  12. Imaging of buried phosphorus nanostructures in silicon using scanning tunneling microscopy

    Oberbeck, Lars [Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); TOTAL Marketing Services, New Energies, La Défense 10, 92069 Paris La Défense Cedex (France); Reusch, Thilo C. G.; Hallam, Toby; Simmons, Michelle Y., E-mail: n.curson@ucl.ac.uk, E-mail: michelle.simmons@unsw.edu.au [Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); Schofield, Steven R. [Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); London Centre for Nanotechnology, UCL, London WC1H 0AH (United Kingdom); Department of Physics and Astronomy, UCL, London WC1E 6BT (United Kingdom); Curson, Neil J., E-mail: n.curson@ucl.ac.uk, E-mail: michelle.simmons@unsw.edu.au [Centre for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); London Centre for Nanotechnology, UCL, London WC1H 0AH (United Kingdom); Department of Electronic and Electrical Engineering, UCL, London WC1E 7JE (United Kingdom)

    2014-06-23

    We demonstrate the locating and imaging of single phosphorus atoms and phosphorus dopant nanostructures, buried beneath the Si(001) surface using scanning tunneling microscopy. The buried dopant nanostructures have been fabricated in a bottom-up approach using scanning tunneling microscope lithography on Si(001). We find that current imaging tunneling spectroscopy is suited to locate and image buried nanostructures at room temperature and with residual surface roughness present. From these studies, we can place an upper limit on the lateral diffusion during encapsulation with low-temperature Si molecular beam epitaxy.

  13. Imaging of buried phosphorus nanostructures in silicon using scanning tunneling microscopy

    We demonstrate the locating and imaging of single phosphorus atoms and phosphorus dopant nanostructures, buried beneath the Si(001) surface using scanning tunneling microscopy. The buried dopant nanostructures have been fabricated in a bottom-up approach using scanning tunneling microscope lithography on Si(001). We find that current imaging tunneling spectroscopy is suited to locate and image buried nanostructures at room temperature and with residual surface roughness present. From these studies, we can place an upper limit on the lateral diffusion during encapsulation with low-temperature Si molecular beam epitaxy.

  14. Relationship between the electric performance and the photoluminescence spectra of resonant tunnelling diodes

    Zhang Xiao-Xin; Zeng Yi-Ping; Wang Xiao-Guang; Wang Bao-Qiang; Zhu Zhan-Ping

    2004-01-01

    Resonant tunnelling diodes with different structures were grown. Their photoluminescence spectra were investigated. By contrast, the luminescence in the quantum well is separated from that of other epilayers. The result is obtained that the exciton of the luminescence in the quantum well is partly come from the cap layer in the experiment.So the photoluminescence spectrum is closely related to the electron transport in the resonant tunnelling diode structure.This offers a method by which the important performance of resonant tunnelling diode could be forecast by analysing the integrated photoluminescence intensities.

  15. Apparent Barrier Height in Scanning Tunneling Microscopy Revisited

    Olesen, L.; Brandbyge, Mads; Sørensen, Mads Reinholdt;

    1996-01-01

    reached rather than decreasing at small tunneling gap distances, as previously reported. The findings for phi(ap) can be accounted for theoretically by including the relaxations of the tip-surface junction in an STM due to the strong adhesive forces at close proximity. These relaxation effects are shown...... also to be generally relevant under imaging conditions at metal surfaces....

  16. Note: Long-range scanning tunneling microscope for the study of nanostructures on insulating substrates

    The scanning tunneling microscope (STM) is a powerful tool for studying the electronic properties at the atomic level, however, it is of relatively small scanning range and the fact that it can only operate on conducting samples prevents its application to study heterogeneous samples consisting of conducting and insulating regions. Here we present a long-range scanning tunneling microscope capable of detecting conducting micro and nanostructures on insulating substrates using a technique based on the capacitance between the tip and the sample and performing STM studies

  17. Note: Long-range scanning tunneling microscope for the study of nanostructures on insulating substrates

    Molina-Mendoza, Aday J., E-mail: aday.molina@uam.es [Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Campus de Cantoblanco, E-28049 Madrid (Spain); Rodrigo, José G.; Rubio-Bollinger, Gabino [Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Campus de Cantoblanco, E-28049 Madrid (Spain); Condensed Matter Physics Center (IFIMAC) and Instituto Universitario de Ciencia de Materiales “Nicolás Cabrera,” Universidad Autónoma de Madrid, Campus de Cantoblanco, E-28049 Madrid (Spain); Island, Joshua; Burzuri, Enrique; Zant, Herre S. J. van der [Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Agraït, Nicolás [Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, Campus de Cantoblanco, E-28049 Madrid (Spain); Condensed Matter Physics Center (IFIMAC) and Instituto Universitario de Ciencia de Materiales “Nicolás Cabrera,” Universidad Autónoma de Madrid, Campus de Cantoblanco, E-28049 Madrid (Spain); Instituto Madrileño de Estudios Avanzados en Nanociencia IMDEA-Nanociencia, E-28049 Madrid (Spain)

    2014-02-15

    The scanning tunneling microscope (STM) is a powerful tool for studying the electronic properties at the atomic level, however, it is of relatively small scanning range and the fact that it can only operate on conducting samples prevents its application to study heterogeneous samples consisting of conducting and insulating regions. Here we present a long-range scanning tunneling microscope capable of detecting conducting micro and nanostructures on insulating substrates using a technique based on the capacitance between the tip and the sample and performing STM studies.

  18. Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement

    Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua, E-mail: canhualiu@sjtu.edu.cn, E-mail: jfjia@sjtu.edu.cn; Jia, Jin-Feng, E-mail: canhualiu@sjtu.edu.cn, E-mail: jfjia@sjtu.edu.cn [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)

    2015-05-15

    Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO{sub 3} surface.

  19. Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement.

    Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua; Jia, Jin-Feng

    2015-05-01

    Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO3 surface. PMID:26026532

  20. Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement

    Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO3 surface

  1. Local imaging of high mobility two-dimensional electron systems with virtual scanning tunneling microscopy

    Correlated electron states in high mobility two-dimensional electron systems (2DESs), including charge density waves and microemulsion phases intermediate between a Fermi liquid and Wigner crystal, are predicted to exhibit complex local charge order. Existing experimental studies, however, have mainly probed these systems at micron to millimeter scales rather than directly mapping spatial organization. Scanning probes should be well-suited to study the spatial structure of these states, but high mobility 2DESs are found at buried semiconductor interfaces, beyond the reach of conventional scanning tunneling microscopy. Scanning techniques based on electrostatic coupling to the 2DES deliver important insights, but generally with resolution limited by the depth of the 2DES. In this letter, we present our progress in developing a technique called “virtual scanning tunneling microscopy” that allows local tunneling into a high mobility 2DES. Using a specially designed bilayer GaAs/AlGaAs heterostructure where the tunnel coupling between two separate 2DESs is tunable via electrostatic gating, combined with a scanning gate, we show that the local tunneling can be controlled with sub-250 nm resolution

  2. Local imaging of high mobility two-dimensional electron systems with virtual scanning tunneling microscopy

    Pelliccione, M. [Department of Applied Physics, Stanford University, 348 Via Pueblo Mall, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106 (United States); Bartel, J.; Goldhaber-Gordon, D. [Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305 (United States); Sciambi, A. [Department of Applied Physics, Stanford University, 348 Via Pueblo Mall, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Pfeiffer, L. N.; West, K. W. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

    2014-11-03

    Correlated electron states in high mobility two-dimensional electron systems (2DESs), including charge density waves and microemulsion phases intermediate between a Fermi liquid and Wigner crystal, are predicted to exhibit complex local charge order. Existing experimental studies, however, have mainly probed these systems at micron to millimeter scales rather than directly mapping spatial organization. Scanning probes should be well-suited to study the spatial structure of these states, but high mobility 2DESs are found at buried semiconductor interfaces, beyond the reach of conventional scanning tunneling microscopy. Scanning techniques based on electrostatic coupling to the 2DES deliver important insights, but generally with resolution limited by the depth of the 2DES. In this letter, we present our progress in developing a technique called “virtual scanning tunneling microscopy” that allows local tunneling into a high mobility 2DES. Using a specially designed bilayer GaAs/AlGaAs heterostructure where the tunnel coupling between two separate 2DESs is tunable via electrostatic gating, combined with a scanning gate, we show that the local tunneling can be controlled with sub-250 nm resolution.

  3. Action spectroscopy for single-molecule motion induced by vibrational excitation with a scanning tunneling microscope

    Ueba, H.; Persson, B.N.J.

    2007-01-01

    We propose an action spectroscopy for single-molecule motion induced by vibrational excitation with a scanning tunneling microscope (STM). Calculations of the inelastic tunneling current for excitation of the C-O stretch mode of the CO molecule on metal surfaces are combined with a theory which describes how the energy in the vibrational mode is transferred to a reaction coordinate mode to overcome the activation barrier. The calculated rate for CO hopping on Pd (110) as a function of the bia...

  4. Theory of a Scanning Tunneling Microscope with a Two-Protrusion Tip

    Flatte, Michael E.; Byers, Jeff M.

    1995-01-01

    We consider a scanning tunneling microscope (STM) such that tunneling occurs through two atomically sharp protrusions on its tip. When the two protrusions are separated by at least several atomic spacings, the differential conductance of this STM depends on the electronic transport in the sample between the protrusions. Furthermore two-protrusion tips commonly occur during STM tip preparation. We explore possible applications to probing dynamical impurity potentials on a metallic surface and ...

  5. Screening of a Luttinger liquid wire by a scanning tunneling microscope tip: II. Transport properties

    Guigou, Marine; Martin, Thierry; Crépieux, Adeline

    2009-01-01

    We study the effect of an electrostatic coupling between a scanning tunneling microscope tip and a Luttinger liquid wire on the tunneling current and noise between the two. Solving the Dyson equations non perturbatively for a local interaction potential, we derive the Green's functions associated to the wire and to the tip. Interestingly, the electrostatic coupling leads to the existence of new correlators, which we call mixed Green's functions, which are correlators between the bosonic field...

  6. Scanning Tunneling Microscope Nanolithography on SrRuO3 Thin Film Surfaces

    Liu, Yun; Zhang, Jia

    2009-01-01

    Nanoscale lithography on SrRuO3 (SRO) thin film surfaces has been performed by scanning tunneling microscopy under ambient conditions. The depth of etched lines increases with increasing bias voltage but it does not change significantly by increasing the tunneling current. The dependence of line width on bias voltage from experimental data is in agreement with theoretical calculation based on field-induced evaporation. Moreover, a three-square nanostructure was successfully created, showing t...

  7. Oxidation of a Single Carbon Monoxide Molecule Manipulated and Induced with a Scanning Tunneling Microscope

    A carbon monoxide molecule (CO) was positioned with a scanning tunneling microscope (STM) at various distances from an oxygen atom (O) on the Ag(110) surface at 13K. At the closest separation, carbon dioxide (CO2) production was induced by tunneling electrons. Direct reaction of a CO desorbed from the STM tip with an O atom on Ag(110) illustrates another catalytic oxidation mechanism. Inelastic electron tunneling spectroscopy with the STM was used to monitor the vibrations of CO in its different environment

  8. First-principles theory of inelastic currents in a scanning tunneling microscope

    Stokbro, Kurt; Hu, Ben Yu-Kuang; Thirstrup, C.; Xie, X. C.

    1998-01-01

    A first-principles theory of inelastic tunneling between a model probe tip and an atom adsorbed on a surface is presented, extending the elastic tunneling theory of Tersoff and Hamann. The inelastic current is proportional to the change in the local density of states at the center of the tip due to the addition of the adsorbate. We use the theory to investigate the vibrational heating of an adsorbate below a scanning tunneling microscopy tip. We calculate the desorption rate of PI from Si(100...

  9. Imaging by Electrochemical Scanning Tunneling Microscopy and Deconvolution Resolving More Details of Surfaces Nanomorphology

    Andersen, Jens Enevold Thaulov

    Upon imaging, electrochemical scanning tunneling microscopy (ESTM), scanning electrochemical micro-scopy (SECM) and in situ STM resolve information on electronic structures and on surface topography. At very high resolution, imaging processing is required, as to obtain information that relates to...... crystallographic-surface structures. Within the wide range of new technologies, those images surface features, the electrochemical scanning tunneling microscope (ESTM) provides means of atomic resolution where the tip participates actively in the process of imaging. Two metallic surfaces influence ions trapped in...... smooth features observed in high-resolution images of metallic nanocrystallites may be effectively deconvoluted, as to resolve more details of the crystalline morphology (see figure). Images of surface-crystalline metals indicate that more than a single atomic layer is involved in mediating the tunneling...

  10. Probing Nanoscale Electronic and Magnetic Interaction with Scanning Tunneling Spectroscopy

    Bork, Jakob

    tunneling microscope (STM). Especially at low temperatures the Kondo resonance is used to probe magnetic interaction with ferromagnetic islands and between two atoms. The latter showing a crossover between Kondo screened atoms and antiferromagnetically coupled atoms close to the quantum critical point. This...... is related to research in correlated electron materials such as studies of phase transitions in heavy fermion compounds and magnetic interaction in spintronic research. The capping of cobalt islands on Cu(111) with silver is investigated with STM and photoemission spectroscopy. It is shown that at...

  11. Imaging of subbands in InAs/GaSb double quantum wells by low-temperature scanning tunneling spectroscopy

    Suzuki, K.; Kanisawa, K.; Perraud, S.; Ueki, M.; Takashina, K.; Hirayama, Y.

    2007-04-01

    The spatial distribution of the electron local density of states (LDOS) in InAs/GaSb double quantum wells (DQWs) was investigated by low-temperature scanning tunneling spectroscopy on cleaved surfaces. For DQW with a thick central barrier, clear standing wave patterns corresponding to subbands confined to each InAs single quantum well appeared in the spatial variation of LDOS spectra. In contrast, for the DQW with a thin central barrier, the standing wave patterns extended over both quantum wells. The deviation of the pattern arising from the asymmetry due to a slight difference of the well thickness appeared clearly. The observed spectra are well explained by the calculated LDOS taken to be the sum of LDOS contributed from all energetically accessible subbands.

  12. Scanning Tunneling Microscopy Studies of Crystalline Hydrogenation of Graphene Grown on Cu(111)

    Tjung, Steven J.; Gambrel, Grady A.; Hollen, Shawna M.; Gupta, Jay A.

    Because of the sensitivity of 2D material surfaces, chemical functionalization can be exploited to tune the electronic structure of these materials. For example, hydrogen bonding to carbon atoms in graphene tunes the material from a semi-metal to a wide-gap insulator. We developed a method for a reproducible epitaxial growth of graphene on Cu(111) in the ultra-high vacuum chamber of a scanning tunneling microscope (STM). We find that hydrogen atoms can be bonded to the graphene in a nanoscale region using a novel field-emission process, whereby physisorbed H2 is cracked in situ using the STM tip. This method produced crystalline surfaces of hydrogen-terminated graphene with 4.2Å lattice, which has proven difficult to produce using conventional atomic beam methods which typically produced disordered hydrogenation. Additionally, this hydrogenation process is reversible and we are able to recover the pristine graphene by H desorption during STM imaging at a high bias. STM images after the dehydrogenation process showed the same atomic lattice and Moiré pattern as the pristine graphene, with the exception of additional point defects. STM spectra show the suppression of the Cu surface state on the hydrogenated graphene, but the opening of a wide-gap was not observed. Funded by the Center for Emergent Materials at the Ohio State University, an NSF MRSEC (Grant No. DMR-1420451 and DMR-0820414).

  13. Scanning tunneling spectroscopy study of the electronic structure of Fe3O4 surfaces

    Jordan, K.; Cazacu, A.; Manai, G.; Ceballos, S. F.; Murphy, S.; Shvets, I. V.

    2006-08-01

    Scanning tunneling spectroscopy (STS) experiments were performed on the (001) and (111) surfaces of single crystalline magnetite. Room temperature spectra exhibit a ˜0.2eV gap around Ef . The importance of perfect surface order to the existence of this gap is illustrated. STS is also carried out on the (111) surface, at 140 and 95K , just above and below the Verwey transition temperature (TV˜120K) , respectively. It is confirmed that above TV a ˜0.2eV gap exists in the surface density of states (DOS) around Ef . Furthermore, broad bands are resolved on both sides of Ef , with peaks centered on ˜+0.5eV and ˜-0.45eV . Below TV it is shown that the value of the gap in the surface DOS remains similar, however, the peaks resolved in the conduction and valence bands shift markedly away from Ef . The similarity of the gap value before and after the transition points away from an ionic charge ordering occurring at the magnetite surface below TV . However, the shifting of the bands points to a certain degree of electronic ordering or charge disproportionation playing an integral part in the Verwey transition, at the magnetite surface.

  14. Thin films of metal oxides on metal single crystals: Structure and growth by scanning tunneling microscopy

    Detailed studies of the growth and structure of thin films of metal oxides grown on metal single crystal surfaces using Scanning Tunneling Microscopy (STM) are presented. The oxide overlayer systems studied are iron oxide and titanium oxide on the Pt(III) surface. The complexity of the metal oxides and large lattice mismatches often lead to surface structures with large unit cells. These are particularly suited to a local real space technique such as scanning tunneling microscopy. In particular, the symmetry that is directly observed with the STM elucidates the relationship of the oxide overlayers to the substrate as well as distinguishing, the structures of different oxides

  15. Scanning tunneling microscopy I general principles and applications to clean and adsorbate-covered surfaces

    Wiesendanger, Roland

    1992-01-01

    Scanning Tunneling Microscopy I provides a unique introduction to a novel and fascinating technique that produces beautiful images of nature on an atomic scale. It is the first of three volumes that together offer a comprehensive treatment of scanning tunneling microscopy, its diverse applications, and its theoretical treatment. In this volume the reader will find a detailed description of the technique itself and of its applications to metals, semiconductors, layered materials, adsorbed molecules and superconductors. In addition to the many representative results reviewed, extensive references to original work will help to make accessible the vast body of knowledge already accumulated in this field.

  16. Tip-Dependent Scanning Tunneling Microscopy Imaging of Ultrathin FeO Films on Pt(111)

    Merte, Lindsay Richard; Grabow, Lars C.; Peng, Guowen;

    2011-01-01

    High-resolution scanning tunneling microscope (STM) images of moiré-structured FeO films on Pt(111) were obtained in a number of different tip-dependent imaging modes. For the first time, the STM images are distinguished and interpreted unambiguously with the help of distinct oxygen-vacancy dislo......High-resolution scanning tunneling microscope (STM) images of moiré-structured FeO films on Pt(111) were obtained in a number of different tip-dependent imaging modes. For the first time, the STM images are distinguished and interpreted unambiguously with the help of distinct oxygen...

  17. Scanning tunneling microscopy of initial nitridation processes on oxidized Si(100) surface with radical nitrogen

    We have investigated the initial nitridation processes on oxidized Si(100) with radical nitrogen at a substrate temperature of 850degC using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). It is found that the thin oxide layer suppresses the changes of original Si step structures during nitridation, and this effect critically depends on the growth conditions of the oxide layer. Comparison of the nitride island morphology to the case of the clean surface suggests that the migration of the precursor during nitridation is suppressed by the oxygen in the layer. (author)

  18. Scanning tunneling spectroscopy of CdSe nanocrystals covalently bound to GaAs

    Walzer, K.; Marx, E.; Greenham, N.C.; Stokbro, Kurt

    2003-01-01

    We present scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) measurements of CdSe nanocrystals covalently attached to doped GaAs substrates using monolayers of 1,6-hexanedithiol. STM measurements showed the formation of stable, densely packed, homogeneous monolayers of...... nanocrystals. STS measurements showed rectifying behaviour, with high currents at the opposite sample bias to that previously observed for CdSe nanocrystals adsorbed on Si substrates. We explain the rectifying behaviour by considering the interaction between the electronic states of the nanocrystals and the...

  19. ZnO(0001) surfaces probed by scanning tunneling spectroscopy: Evidence for an inhomogeneous electronic structure

    Dumont, J.; Hackens, B.; Faniel, S.; Mouthuy, P.-O.; Sporken, R.; Melinte, S.

    2009-09-01

    The stability of the polar Zn-terminated ZnO surface is probed by low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy (STS). Surface states in the bandgap of ZnO are evidenced by STS and their presence is correlated with the local surface corrugation. Very defective surface regions are characterized by a bulk electronic structure showing a wide bandgap while nanometer-scale defect free regions exhibit a narrower bandgap and surface states. We also image atomically resolved (√3 ×√3 )R30° reconstructions on the defect-free areas.

  20. Scanning tunneling microscopy of initial nitridation processes on oxidized Si(100) surface with radical nitrogen

    Takahashi, R; Ikeda, H; Sakashita, M; Sakai, A; Yasuda, Y; Nakatsuka, O; Zaima, S

    2003-01-01

    We have investigated the initial nitridation processes on oxidized Si(100) with radical nitrogen at a substrate temperature of 850degC using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). It is found that the thin oxide layer suppresses the changes of original Si step structures during nitridation, and this effect critically depends on the growth conditions of the oxide layer. Comparison of the nitride island morphology to the case of the clean surface suggests that the migration of the precursor during nitridation is suppressed by the oxygen in the layer. (author)

  1. Scanning tunneling spectroscopy of methyl- and ethyl-terminated Si(111) surfaces

    Yu, Hongbin; Webb, Lauren J.; Heath, James R.; Lewis, Nathan S.

    2006-01-01

    Methyl- and ethyl-terminated Si(111) surfaces prepared by a two-step chlorination/alkylation method were characterized by low temperature scanning tunneling spectroscopy (STS). The STS data showed remarkably low levels of midgap states on the CH3- and C2H5-terminated Si surfaces. A large conductance gap relative to the Si band gap was observed for both surfaces as well as for the hydrogen-terminated Si(111) surface. This large gap is ascribed to scanning tunneling microscope tip-induced band ...

  2. Three-dimensional laser scanning for geometry documentation and construction management of highway tunnels during excavation.

    Gikas, Vassilis

    2012-01-01

    Driven by progress in sensor technology, computer software and data processing capabilities, terrestrial laser scanning has recently proved a revolutionary technique for high accuracy, 3D mapping and documentation of physical scenarios and man-made structures. Particularly, this is of great importance in the underground space and tunnel construction environment as surveying engineering operations have a great impact on both technical and economic aspects of a project. This paper discusses the use and explores the potential of laser scanning technology to accurately track excavation and construction activities of highway tunnels. It provides a detailed overview of the static laser scanning method, its principles of operation and applications for tunnel construction operations. Also, it discusses the planning, execution, data processing and analysis phases of laser scanning activities, with emphasis given on geo-referencing, mesh model generation and cross-section extraction. Specific case studies are considered based on two construction sites in Greece. Particularly, the potential of the method is examined for checking the tunnel profile, producing volume computations and validating the smoothness/thickness of shotcrete layers at an excavation stage and during the completion of excavation support and primary lining. An additional example of the use of the method in the geometric documentation of the concrete lining formwork is examined and comparisons against dimensional tolerances are examined. Experimental comparisons and analyses of the laser scanning method against conventional surveying techniques are also considered. PMID:23112655

  3. Three-Dimensional Laser Scanning for Geometry Documentation and Construction Management of Highway Tunnels during Excavation

    Vassilis Gikas

    2012-08-01

    Full Text Available Driven by progress in sensor technology, computer software and data processing capabilities, terrestrial laser scanning has recently proved a revolutionary technique for high accuracy, 3D mapping and documentation of physical scenarios and man-made structures. Particularly, this is of great importance in the underground space and tunnel construction environment as surveying engineering operations have a great impact on both technical and economic aspects of a project. This paper discusses the use and explores the potential of laser scanning technology to accurately track excavation and construction activities of highway tunnels. It provides a detailed overview of the static laser scanning method, its principles of operation and applications for tunnel construction operations. Also, it discusses the planning, execution, data processing and analysis phases of laser scanning activities, with emphasis given on geo-referencing, mesh model generation and cross-section extraction. Specific case studies are considered based on two construction sites in Greece. Particularly, the potential of the method is examined for checking the tunnel profile, producing volume computations and validating the smoothness/thickness of shotcrete layers at an excavation stage and during the completion of excavation support and primary lining. An additional example of the use of the method in the geometric documentation of the concrete lining formwork is examined and comparisons against dimensional tolerances are examined. Experimental comparisons and analyses of the laser scanning method against conventional surveying techniques are also considered.

  4. Scanning-tunneling and atomic-force microscopy

    (STM and AFM) are allowing for in situ (in air and under water) imaging of mineral surfaces at previously unattainable nanometer to atomic scales. The four images, which represent a range of STM/AFM applications, were all taken on [001] surfaces of hematite. Counterclockwise from bottom left, these micrographs are described as follows: (1) An STM image of oxygen sites on terraces separated by steps—imaged under oil at -300-mV sample bias. The difference in tunneling current between terrace (blue) and step-edge (pink) sites can be related to differences in local electronic structure that may affect the reactivity of the different sites Terraces step downward toward the lower left. A kink site is apparent along one step. (2) An AFM image in air showing the molecular-scale structure of the hematite surface.

  5. Local crystallography analysis for atomically resolved scanning tunneling microscopy images

    Scanning probe microscopy has emerged as a powerful and flexible tool for atomically resolved imaging of surface structures. However, due to the amount of information extracted, in many cases the interpretation of such data is limited to being qualitative and semi-quantitative in nature. At the same time, much can be learned from local atom parameters, such as distances and angles, that can be analyzed and interpreted as variations of local chemical bonding, or order parameter fields. Here, we demonstrate an iterative algorithm for indexing and determining atomic positions that allows the analysis of inhomogeneous surfaces. This approach is further illustrated by local crystallographic analysis of several real surfaces, including highly ordered pyrolytic graphite and an Fe-based superconductor FeTe0.55Se0.45. This study provides a new pathway to extract and quantify local properties for scanning probe microscopy images. (paper)

  6. Light amplification by stimulated emission from an optically pumped molecular junction in a scanning tunneling microscope

    Braun, K; Wang, X; Adler, H; Peisert, H; Chasse, T; Zhang, D; Meixner, A J

    2013-01-01

    Here, we introduce and experimentally demonstrate optical amplification and stimulated emission from a single optically pumped molecular tunneling junction of a scanning tunneling microscope. The gap between a sharp gold tip and a flat gold substrate covered with a self-assembled monolayer of 5-chloro-2-mercaptobenzothiazole molecules forms an extremely small optical gain medium. When electrons tunnel from the molecules highest occupied molecular orbital to the tip, holes are left behind. These can be repopulated by hot electrons induced by the laser-driven plasmon oscillation on the metal surfaces enclosing the cavity. Solving the laser-rate equations for this system shows that the repopulation process can be efficiently stimulated by the gap modes near field, TERS scattering from neighboring molecules acting as an optical seed. Our results demonstrate how optical enhancement inside the plasmonic cavity can be further increased by a stronger localization via tunneling through molecules. We anticipate that st...

  7. Note: A simple, convenient, and reliable method to prepare gold scanning tunneling microscope tips

    A simple method to prepare gold tips for scanning tunneling microscopy has been introduced. In this method, electrochemical etching without a hazardous electrolyte was employed. The setup uses basic laboratory instrumentation to control the etching process. This avoids purchasing complicated, expensive, and dedicated equipment for tip preparation. A procedure to optimize the etching parameters by setting the current limit is described. Etched tips were checked with both optical and scanning electron microscopy.

  8. New design of a variable-temperature ultrahigh vacuum scanning tunneling microscope

    Mugele, F.; Rettenberger, A.; Boneberg, J.; Leiderer, P.

    1998-01-01

    We present the design of a variable-temperature ultrahigh vacuum (UHV) scanning tunneling microscope which can be operated between 20 and 400 K. The microscope is mounted directly onto the heat exchanger of a He continuous flow cryostat without vibration isolation inside the UHV chamber. The coarse approach is performed with an inertial slider driven by the same piezo tube that is also used for scanning. The performance of the instrument is demonstrated by two different kinds of measurements:...

  9. A NEW APPROACH FOR SUBWAY TUNNEL DEFORMATION MONITORING: HIGH-RESOLUTION TERRESTRIAL LASER SCANNING

    Li, J.; Wan, Y.; Gao, X.

    2012-01-01

    With the improvement of the accuracy and efficiency of laser scanning technology, high-resolution terrestrial laser scanning (TLS) technology can obtain high precise points-cloud and density distribution and can be applied to high-precision deformation monitoring of subway tunnels and high-speed railway bridges and other fields. In this paper, a new approach using a points-cloud segmentation method based on vectors of neighbor points and surface fitting method based on moving leas...

  10. Correlation of scanning-tunneling-microscope image profiles and charge-density-wave amplitudes

    Scanning-tunneling-microscope (STM) studies of 4Hb-TaS2 and 4Hb-TaSe2 at 4.2 K show systematic correlation between the charge-density-wave (CDW) amplitude and the STM deflection. The 4Hb phases have both weak and strong CDW's in the trigonal prismatic and octahedral sandwiches, respectively. Scans on opposite faces of the same cleave allow a comparison of the STM response to the two types of CDW

  11. Simultaneous topographic and elemental chemical and magnetic contrast in scanning tunneling microscopy

    Rose, Volker; Preissner, Curt A; Hla, Saw-Wai; Wang, Kangkang; Rosenmann, Daniel

    2014-09-30

    A method and system for performing simultaneous topographic and elemental chemical and magnetic contrast analysis in a scanning, tunneling microscope. The method and system also includes nanofabricated coaxial multilayer tips with a nanoscale conducting apex and a programmable in-situ nanomanipulator to fabricate these tips and also to rotate tips controllably.

  12. A development in the preparation of sharp scanning tunneling microscopy tips

    Song, J. P.; Pryds, N. H.; Glejbøl, K.; Mørch, Knud Aage; Thölén, A. R.; Christensen, Lars Nygaard

    1993-01-01

    An improved and reliable method for making sharp scanning tunneling microscopy (STM) tips is described. It is based on the widely used drop-off electrochemical etching procedure, here modified to improve the control of the tip shape. A second etching is applied not only to remove the oxide layer...

  13. Characterization and manipulation of individual defects in insulating hexagonal boron nitride using scanning tunnelling microscopy

    Wong, Dillon; Velasco, Jairo; Ju, Long; Lee, Juwon; Kahn, Salman; Tsai, Hsin-Zon; Germany, Chad; Taniguchi, Takashi; Watanabe, Kenji; Zettl, Alex; Wang, Feng; Crommie, Michael F.

    2015-11-01

    Defects play a key role in determining the properties and technological applications of nanoscale materials and, because they tend to be highly localized, characterizing them at the single-defect level is of particular importance. Scanning tunnelling microscopy has long been used to image the electronic structure of individual point defects in conductors, semiconductors and ultrathin films, but such single-defect electronic characterization remains an elusive goal for intrinsic bulk insulators. Here, we show that individual native defects in an intrinsic bulk hexagonal boron nitride insulator can be characterized and manipulated using a scanning tunnelling microscope. This would typically be impossible due to the lack of a conducting drain path for electrical current. We overcome this problem by using a graphene/boron nitride heterostructure, which exploits the atomically thin nature of graphene to allow the visualization of defect phenomena in the underlying bulk boron nitride. We observe three different defect structures that we attribute to defects within the bulk insulating boron nitride. Using scanning tunnelling spectroscopy we obtain charge and energy-level information for these boron nitride defect structures. We also show that it is possible to manipulate the defects through voltage pulses applied to the scanning tunnelling microscope tip.

  14. Streamlined Inexpensive Integration of a Growth Facility and Scanning Tunneling Microscope for in situ Characterization

    Xu, P.; D. Qi; Barber, S. D.; Cook, C. T.; Ackerman, M. L.; Thibado, P. M.

    2015-01-01

    The integration of a scanning tunneling microscope chamber with a sample growth facility using non-custom, commercially available parts is described. The facility also features a newly-designed magnetic wobble stick to increase the reliability of sample transfer in a cost-effective manner.

  15. Observation of a Ag protrusion on a Ag2S island using a scanning tunneling microscope

    Takeo Ohno

    2015-01-01

    Full Text Available A silver sulfide (Ag2S island as an ionic conductor in resistive switching memories was formed and a protrusion of silver from the Ag2S formed by an electrochemical reaction was observed using a scanning tunneling microscope.

  16. Scanning tunneling microscopy in TTF-TCNQ: Phase and amplitude modulated charge density waves

    Wang, Z.Z.; Gorard, J.C.; Pasquier, C.; Jerome, D.; Bechgaard, K.

    2003-01-01

    Charge density waves (CDWs) have been studied at the surface of a cleaved tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) single crystal using a low temperature scanning tunneling microscope (STM) under ultrahigh-vacuum conditions, between 300 and 33 K with molecular resolution. All CDW...

  17. Visible Light Emission from Atomic Scale Patterns Fabricated by the Scanning Tunneling Microscope

    Thirstrup, C.; Sakurai, M.; Stokbro, Kurt; Aono, M.

    1999-01-01

    Scanning tunneling microscope (STM) induced light emission from artificial atomic scale structures comprising silicon dangling bonds on hydrogen-terminated Si(001) surfaces has been mapped spatially and analyzed spectroscopically in the visible spectral range. The light emission is based on a novel...

  18. DEVELOPMENT OF THE FIELD ION-SCANNING TUNNELING MICROSCOPE AND ITS APPLICATIONS

    Kamiya, I.; Sakurai, T

    1989-01-01

    A scanning tunneling microscope (STM) equipped with a field ion microscope (FIM) which operates at room temperature has been constructed and operated successfully to obtain atomically resolved STM images with 100% reproductibility. This instrument, which we call the FI-STM, has been employed for the quantitative study of the Si(100) "2xn" phase.

  19. Imaging of surface plasmon polariton interference using phase-sensitive photon scanning tunneling microscope

    Jose, J.; Segerink, F.B.; Korterik, J.P.; Herek, J. L.; Offerhaus, H.L.

    2011-01-01

    We report the surface plasmon polariton interference, generated via a ‘buried’ gold grating, and imaged using a phase-sensitive Photon Scanning Tunneling Microscope (PSTM). The phase-resolved PSTM measurement unravels the complex surface plasmon polariton interference fields at the gold-air interface

  20. Transient measurements with an ultrafast scanning tunneling microscope on semiconductor surfaces

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1998-01-01

    We demonstrate: the use of an ultrafast scanning tunneling microscope on a semiconductor surface. Laser-induced transient signals with 1.8 ps rise time are detected, The investigated sample is a low-temperature grown GaAs layer plated on a sapphire substrate with a thin gold layer that serves as st...

  1. Local investigation of magnetic structures in superconductors by a low-temperature scanning tunneling microscope

    A low temperature scanning tunneling microscope device was constructed which allows a simultaneous spectroscopic and morphological measurement up to 4.2 K and 1T. Layers of niobium and NbSe2 were measured and flux lines were determined. (WL)

  2. Adsorption of Cu phthalocyanine on Pt modified Ge(001): A scanning tunneling microscopy study

    Saedi, Amirmehdi; Berkelaar, Robin P.; Kumar, Avijit; Poelsema, Bene; Zandvliet, Harold J.W.

    2010-01-01

    The adsorption configurations of copper phthalocyanine (CuPc) molecules on platinum-modified Ge(001) have been studied using scanning tunneling microscopy. After deposition at room temperature and cooling down to 77 K the CuPc molecules are still dynamic. However, after annealing at 550±50 K, the ad

  3. Covalently Immobilised Cytochrome C Imaged by In Situ Scanning Tunnelling Microscopy

    Andersen, Jens Enevold Thaulov; Olesen, Klaus G.; Danilov, Alexey I.;

    1997-01-01

    In situ scanning tunnelling microscopy (STM) imaging of cytochrome c (cyt c) on polycrystalline Pt surfaces and on Au(lll) was achieved first by covalent immobilisation of 3-aminopropyltriethoxysilane (3-APTS) brought to react with oxide present on the Pt surfaces. Covalently bound 3-APTS forms a...

  4. Measurements with an ultrafast scanning tunnelling microscope on photoexcited semiconductor layers

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1998-01-01

    Summary form only given. We demonstrate the use of a ultrafast scanning tunnelling microscopes (USTM) for detecting laser-induced field transients on semiconductor layers. In principle, the instrument can detect transient field changes thus far observed as far-field THz radiation in the near...

  5. Spectroscopic-imaging scanning tunneling microscopy as a tool to study electronic states. Part 2

    We describe some remarks on analyzing the data of spectroscopic-imaging scanning tunneling microscopy, especially paying attention to the set-point effect which makes a conductance map different from a local-density-of-state map. As a concrete example, we discuss quasiparticle interference effect in a cuprate superconductor. (author)

  6. Hourglass-shaped dendrimers on surfaces : A comparison of different scanning-tunneling-microscopy approaches

    Widmer, I.; Hubler, U; Stöhr, Meike; Merz, L; Guntherodt, HJ; Hermann, BA; Samori, P; Rabe, JP; Rheiner, PB; Greiveldinger, G; Murer, P

    2002-01-01

    Large molecules adsorbed on surfaces can be analyzed by scanning tunneling microscopy (STM) under various environmental conditions: on a dry surface in air or vacuum, and at the solid-liquid interface. However, can measurements under dissimilar conditions be compared, e.g., when sample A was studied

  7. Scanning Tunneling Microscopy Studies of Topological Insulators Grown by Molecular Beam Epitaxy

    Xue Qikun

    2012-03-01

    Full Text Available We summarize our recent scanning tunneling microscopy (STM study of topological insulator thin films grown by molecular beam epitaxy (MBE, which includes the observation of electron standing waves on topological insulator surface and the Landau quantization of topological surface states. The work has provided valuable information to the understanding of intriguing properties of topological insulators, as predicted by theory.

  8. Scanning-tunneling-microscope investigations on Rb exposed TaS2 and light emission from silicon

    Schmidt, Patrick

    2008-01-01

    Two different aspects of surface science were analyzed in this thesis. First, the light emission properties of single crystal silicon with different orientations and doping were studied using the scanning tunneling microscope. Tunneling electrons excite several optical transitions in silicon bulk. The direct interband transitions are well known, but this is the first time these transitions were observed with scanning-tunneling-microscope induced luminescence. For the case of electron tunnelin...

  9. Substrate effects on the surface topography of evaporated gold films—A scanning tunnelling microscopy investigation

    Vancea, J.; Reiss, G.; Schneider, F.; Bauer, K.; Hoffmann, H.

    1989-08-01

    Direct observation of surface roughness on metal films is a longstanding problem in thin film characterization. In this work the high quality of scanning tunnelling microscopy (STM) was used for investigation of evaporated gold films. A scanning tunnelling microscope able to scan areas up to 0.8 × 0.8 micro m with high reproducibility is presented. The topography of 80 nm thick gold films grown under identical evaporation conditions was investigated as a function of the selected substrate material (Corning glass, silicon, NaCl, mica and highly oriented pyrolitic graphite (HOPG)). The incipient growth mechanism on the substrate is the primary reason for the surface roughness. The real space images of the surface topography correlate very well with knowledge achieved from former growth experiments given in the literature. Moreover, very flat gold surfaces on HOPG allowed the observation of atomic corrugations in air environments.

  10. Nanoscale ferroelectric field-effect writing and reading using scanning tunnelling spectroscopy.

    Kuffer, Olivier; Maggio-Aprile, Ivan; Fischer, Øystein

    2005-05-01

    Control of the density of mobile charge carriers using electric fields is widely used in a variety of metal-insulator-semiconductor structures and is the governing principle behind the operation of field-effect transistors. Ferroelectric materials possessing a switchable and non-volatile polarization field can be used as insulating layers, revealing new opportunities for device applications. Advances in material processing and in particular complex oxide thin-film growth mean that high-quality field-effect devices can be based on ferroelectric/metallic oxide heterostructures. In addition, advances in local probe techniques such as atomic force microscopy allow them to be used in the imaging and study of small ferroelectric domain structures in bulk crystals and thin films. Meanwhile, scanning tunnelling microscopy and spectroscopy have established themselves as powerful techniques for atomic manipulation and nanometre-resolution electron tunnelling spectroscopy. Here, a scanning tunnelling microscope is used to investigate the ferroelectric field effect in all-perovskite heterostructures. Scanning tunnelling spectroscopy allows us to probe the local electronic properties of the polarized channel of a ferroelectric field-effect device as a function of the field orientation. This technique can be used to read and write ferroelectric field-induced regions with a size as low as 20 nm. PMID:15834416

  11. Superconducting LiFeAs as seen by scanning tunneling microscopy/spectroscopy

    Among the entire class of iron-based superconductors the material LiFeAs is of particular interest since an absence of nesting between electron and hole pockets suggests an unconventional type of pairing in this material. Using Scanning Tunnelling Microscopy (STM) and Spectroscopy (STS) we investigate topographic properties of the surface as well as the temperature dependency of the superconducting gap. The good agreement of our results with model calculations for the tunnelling conductance allows us to draw conclusions about the low energy properties of the superconducting system. Furthermore, we compare our results with Transport- and NMR-measurements.

  12. A low‐temperature atomic force/scanning tunneling microscope for ultrahigh vacuum

    Giessibl, Franz J.; Gerber, Christoph; Binnig, Gerd

    1991-01-01

    We have built an ultrahigh vacuum atomic force/scanning tunneling microscope that works at 4.2 K. The microscope is incorporated into a very small chamber (100 ml) which can be evacuated and baked to UHV within a few hours by a specially designed valve. The instrument is about 20×20×70 mm3 in size and sturdy enough to operate without vibration isolation. The deflection of a microfabricated cantilever is detected by electron tunneling. Preliminary results show atomic resolution of HOPG in the ...

  13. Fermi surface contours obtained from scanning tunneling microscope images around surface point defects

    We present a theoretical analysis of the standing wave patterns in scanning tunneling microscope (STM) images, which occur around surface point defects. We consider arbitrary dispersion relations for the surface states and calculate the conductance for a system containing a small-size tunnel contact and a surface impurity. We find rigorous theoretical relations between the interference patterns in the real-space STM images, their Fourier transforms and the Fermi contours of two-dimensional electrons. We propose a new method for reconstructing Fermi contours of surface electron states, directly from the real-space STM images around isolated surface defects. (paper)

  14. Transient measurements with an ultrafast scanning tunneling microscope on semiconductor surfaces

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1998-01-01

    We demonstrate: the use of an ultrafast scanning tunneling microscope on a semiconductor surface. Laser-induced transient signals with 1.8 ps rise time are detected, The investigated sample is a low-temperature grown GaAs layer plated on a sapphire substrate with a thin gold layer that serves as st bias contact, For comparison, the measurements are performed with the tip in contact to the sample as well as in tunneling above the surface, In contact and under bias, the transient signals are id...

  15. When scanning tunneling microscopy gets the wrong adsorption site: H on Rh(100)

    At low tunneling resistance, scanning tunneling microscopy (STM) images of a Rh(100) surface with adsorbed hydrogen reproducibly show protrusions in all bridge sites of the surface, leading to a naive interpretation of all bridge sites being occupied with H atoms. Using quantitative low-energy electron diffraction and temperature programmed desorption we find a much lower H coverage, with most H atoms in fourfold hollow sites. Density functional theory calculations show that the STM result is due to the influence of the tip, attracting the mobile H atoms into bridge sites. This demonstrates that STM images of highly mobile adsorbates can be strongly misleading and underlines the importance of additional analysis techniques

  16. A Mechanism for Cutting Carbon Nanotubes with a Scanning Tunneling Microscope

    Rubio, Angel; Apell, S. Peter; Venema, Liesbeth C.; Dekker, Cees

    2000-01-01

    We discuss the local cutting of single-walled carbon nanotubes by a voltage pulse to the tip of a scanning tunneling microscope. The tip voltage ($\\mid V \\mid \\ge $~3.8 eV) is the key physical quantity in the cutting process. After reviewing several possible physical mechanisms we conclude that the cutting process relies on the weakening of the carbon-carbon bonds through a combination of localized particle-hole excitations induced by inelastically tunneling electrons and elastic deformation ...

  17. Scanning tunneling microscopy on rough surfaces: Deconvolution of constant current images

    Reiss, G.; Schneider, F.; Vancea, J.; Hoffmann, H.

    1990-08-01

    This letter critically discusses the topographical information obtained by scanning tunneling microscopy (STM) on surfaces with a mesoscopic roughness, i.e., in the range of some nm's. In a foregoing publication [J. Appl. Phys. 67, 1156 (1990)], we already treated the evaluation of constant current images based on the knowledge of the real surface and the shape of the tunneling tip (``tip shape limited resolution''). Now we deal with the invers problem: the reconstruction of the real surface topography based on the corresponding STM image and the tip shape, using a simple, straightforward formalism.

  18. Scanning tunnelling microscopy of real time defect motion on surfaces

    Full text: The Interface Physics group uses various types of Scanning Probe Microscopy to investigate the structure and dynamic behaviour of surfaces and interfaces. Topics that they are working on at present include surface diffusion, surface phase transitions, gas-surface interactions, nanotribology, and nanobiology. For example, from accurate measurements of the statistics of the observed jump lengths and of the waiting times between successive jumps, it has been deduced that the mobility of indium atoms on a copper surface is caused by the rapid, two-dimensional diffusion of a very low density of monatomic vacancies (missing copper atoms), through the first copper layer. Due to their ultrahigh diffusion rate, these vacancies remain 'invisible' for the STM at room temperature. It is important to realize that the slide-puzzle diffusion mechanism is also active when there is no embedded indium in the copper surface. The indium merely serves as a low density of 'tracer' particles, which enable us to follow the rearrangements continually taking place in the surface. What we learn from these observations is that not only adatoms, but also the atoms in a close-packed terrace of a metal surface are mobile at relatively low temperatures, e.g. room temperature. Copyright (2005) Australian Institute of Physics

  19. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations

  20. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    Morawski, Ireneusz [Peter Grünberg Institut (PGI-3) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich, 52425 Jülich (Germany); Institute of Experimental Physics, University of Wrocław, pl. M. Borna 9, 50-204 Wrocław (Poland); Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert [Peter Grünberg Institut (PGI-3) and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich, 52425 Jülich (Germany)

    2015-12-15

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  1. EDITORIAL: Three decades of scanning tunnelling microscopy that changed the course of surface science Three decades of scanning tunnelling microscopy that changed the course of surface science

    Ramachandra Rao, M. S.; Margaritondo, Giorgio

    2011-11-01

    Three decades ago, with a tiny tip of platinum, the scientific world saw the real space imaging of single atoms with unprecedented spatial resolution. This signalled the birth of one of the most versatile surface probes, based on the physics of quantum mechanical tunnelling: the scanning tunnelling microscope (STM). Invented in 1981 by Gerd Binnig and Heinrich Rohrer of IBM, Zurich, it led to their award of the 1986 Nobel Prize. Atoms, once speculated to be abstract entities used by theoreticians for mere calculations, can be seen to exist for real with the nano-eye of an STM tip that also gives real-space images of molecules and adsorbed complexes on surfaces. From a very fundamental perspective, the STM changed the course of surface science and engineering. STM also emerged as a powerful tool to study various fundamental phenomena relevant to the properties of surfaces in technological applications such as tribology, medical implants, catalysis, sensors and biology—besides elucidating the importance of local bonding geometries and defects, non-periodic structures and the co-existence of nano-scale phases. Atom-level probing, once considered a dream, has seen the light with the evolution of STM. An important off-shoot of STM was the atomic force microscope (AFM) for surface mapping of insulating samples. Then followed the development of a flurry of techniques under the general name of scanning probe microscopy (SPM). These techniques (STM, AFM, MFM, PFM etc) designed for atomic-scale-resolution imaging and spectroscopy, have led to brand new developments in surface analysis. All of these novel methods enabled researchers in recent years to image and analyse complex surfaces on microscopic and nanoscopic scales. All of them utilize a small probe for sensing the surface. The invention of AFM by Gerd Binnig, Calvin Quate and Christopher Gerber opened up new opportunities for characterization of a variety of materials, and various industrial applications could be

  2. Theoretical study of carbon-based tips for scanning tunnelling microscopy

    González, C.; Abad, E.; Dappe, Y. J.; Cuevas, J. C.

    2016-03-01

    Motivated by recent experiments, we present here a detailed theoretical analysis of the use of carbon-based conductive tips in scanning tunnelling microscopy. In particular, we employ ab initio methods based on density functional theory to explore a graphitic, an amorphous carbon and two diamond-like tips for imaging with a scanning tunnelling microscope (STM), and we compare them with standard metallic tips made of gold and tungsten. We investigate the performance of these tips in terms of the corrugation of the STM images acquired when scanning a single graphene sheet. Moreover, we analyse the impact of the tip-sample distance and show that it plays a fundamental role in the resolution and symmetry of the STM images. We also explore in depth how the adsorption of single atoms and molecules in the tip apexes modifies the STM images and demonstrate that, in general, it leads to an improved image resolution. The ensemble of our results provides strong evidence that carbon-based tips can significantly improve the resolution of STM images, as compared to more standard metallic tips, which may open a new line of research in scanning tunnelling microscopy.

  3. Creation of stable molecular junctions with a custom-designed scanning tunneling microscope

    The scanning tunneling microscope break junction (STMBJ) technique is a powerful approach for creating single-molecule junctions and studying electrical transport in them. However, junctions created using the STMBJ technique are usually mechanically stable for relatively short times (<1 s), impeding detailed studies of their charge transport characteristics. Here, we report a custom-designed scanning tunneling microscope that enables the creation of metal–single molecule–metal junctions that are mechanically stable for more than 1 minute at room temperature. This stability is achieved by a design that minimizes thermal drift as well as the effect of environmental perturbations. The utility of this instrument is demonstrated by performing transition voltage spectroscopy—at the single-molecule level—on Au–hexanedithiol–Au, Au–octanedithiol–Au and Au–decanedithiol–Au junctions.

  4. Masking generates contiguous segments of metal-coated and bare DNA for scanning tunneling microscope imaging.

    Dunlap, D D; García, R.; Schabtach, E; Bustamante, C.

    1993-01-01

    To date, no microscopic methods are available to confirm scanning tunneling microscope (STM) images of DNA. The difficulties encountered in repeating these images may be attributed to inadequate distribution of molecules on the substrate, poor adhesion to the substrate, or the low conductivity of the molecules. However, these factors are difficult to assess in an STM experiment where they may act simultaneously. A method to isolate these factors involves partly masking the deposited molecules...

  5. Scanning tunneling microscopy and spectroscopy of functional molecules on metal surfaces

    Ge, Xin

    2007-01-01

    This thesis is committed to the study of functional molecules adsorbed on metal surfaces by means of Low Temperature Scanning Tunneling Microscopy. It includes two main parts. In the first part the adsorption geometry of lander molecule (C90H98) on different metal surfaces is discussed. Three conformations as well as chiral structures of lander molecules on the terrace of Cu(100) are observed by STM. Electron scattering quantum chemical calculated results are compared with our experimental da...

  6. Nuclear and electronic resonance spectroscopy of single molecules by radio-frequency scanning tunnelling microscopy

    Müllegger, Stefan; Tebi, Stefano; Das, Amal K.; Schöfberger, Wolfgang; Faschinger, Felix; Koch, Reinhold

    2014-01-01

    The ongoing miniaturization in nanoscience and -technology challenges the sensitivity and selectivity of experimental analysis methods to the ultimate level of single atoms and molecules. A promising new approach, addressed here, focuses on the combination of two well-established complementary techniques that have proven to be very successful in their own fields: (i) low-temperature scanning tunneling microscopy (STM), offering high spatial resolution for imaging and spectroscopy together wit...

  7. Terthiophene on Au(111): A scanning tunneling microscopy and spectroscopy study

    Berndt Koslowski; Anna Tschetschetkin; Norbert Maurer; Elena Mena-Osteritz; Peter Bäuerle; Paul Ziemann

    2011-01-01

    Terthiophene (3T) molecules adsorbed on herringbone (HB) reconstructed Au(111) surfaces in the low coverage regime were investigated by means of low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) under ultra-high vacuum conditions. The 3T molecules adsorb preferentially in fcc regions of the HB reconstruction with their longer axis oriented perpendicular to the soliton walls of the HB and at maximum mutual separation. The latter observation points to a repulsive intera...

  8. Control led sequential dehydrogenation of single molecules by scanning tunneling microscopy

    Sanvito, Stefano

    2010-01-01

    Scanning tunneling microscopy STM is today the most powerful and versatile tool available for imaging and manipulating single molecules on surfaces. Here, we explore its ultimate limit by demonstrating the possibility of controlling sequential di-dehydrogenation of single Co-Salen molecules sublimated on Cu. In particular, we are able to explore the final products of the H 2 dissociation as well as the intermediate state, in which only one H atom is separated from the ...

  9. Scanning tunneling microscopy theory for an adsorbate: Application to adenine adsorbed on a graphite surface

    Ou-Yang, Hui; Marcus, R. A.; Källebring, Bruno

    1994-01-01

    An expression is obtained for the current in scanning tunneling microscopy (STM) for a single adsorbate molecule. For this purpose the ``Newns–Anderson'' treatment (a ``discrete state in a continuum'' treatment) is used to obtain wave functions and other properties of the adsorbate/substrate system. The current is expressed in terms of the adsorbate–tip matrix elements, and an effective local density of states of the adsorbate/substrate system, at the adsorbate. As an example, the treatment i...

  10. Understanding the electroluminescence emitted by single molecules in scanning tunneling microscopy experiments

    Buker, John; Kirczenow, George

    2008-01-01

    We explore theoretically the electroluminescence of single molecules. We adopt a local-electrode framework that is appropriate for scanning tunneling microscopy (STM) experiments where electroluminescence originates from individual molecules of moderate size on complex substrates: Couplings between the STM tip and molecule and between the molecule and multiple substrate sites are treated on the same footing, as local electrodes contacting the molecule. Electron flow is modelled with the Lippm...