bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of 4Hb‐TaS2 and graphite intercalation compound by STM/STS
Authors: Tanaka M. , Mizutani W. , Nakashizu T. , Morita N. , Yamazaki S. , Bando H. , Ono M. , Kajimura K. 
Published: August 2011

SUMMARYInvestigations of charge‐density waves (CDW) in 4Hb‐TaS2 and the shifted Fermi level in a CoCl2 graphite intercalation compound (GIC) were performed by scanning tunnelling microscopy (STM) and scanning tunnelling spectroscopy (STS) A discrimination of the surface electronic structure of the octahedral structure and of the trigonal‐prismatic structure in 4Hb‐TaS2 was made successfully in terms of the electronic properties. The measured value of the charge‐density‐wave gap in 4Hb‐TaS2 at room temperature was about 85 meV. The shifted Fermi level in CoCl2‐GIC was measured to be about 400 meV.
Observation of very thin gold island films vacuum‐deposited onto MoS2 surface by STM
Authors: Uozumi Kiyohiko 
Published: August 2011

SUMMARYA gold film of about half a monolayer in thickness was vacuum‐deposited onto air‐cleaved MoS2 surface at room temperature at a pressure of 10−5 Pa. Quasi‐two‐dimensionally grown gold islands made of several atomic layers were observed by scanning an area of 40×30 nm2. The shape of them was oblate and about 20 nm in diameter. Atomic corrugations which reflect the Au(111) surface were observed. The islands were found to move and changed their shape during the microscopy.
Observation and manipulation of polymers by scanning tunnelling and atomic force microscopy
Authors: Dovek M. M. , Albrecht T. R. , Kuan S. W. J. , Lang C. A. , Emch R. , Grütter P. , Frank C. W. , Pease R. F. W. , Quate C. F. 
Published: August 2011

SUMMARYThe properties of monolayer films of organic materials are important for a variety of technologies. We have employed STM and AFM to study Langmuir‐Blodgett films of a variety of polymers on substrates of graphite, MoS2, and Au(111) on mica. The polymers were poly(octadecyl acrylate) (PODA), atactic and syndiotactic poly(methyl methacrylate) (PMMA) and poly(2‐methyl‐1‐pentene sulphone) (PMPS). One striking feature was the degree of order observed; a second was the morphological difference between films of submonolayer thickness (long, thin fibrils) and those of at least monolayer thickness (lumpy structures arranged in domains). By pulsing the STM bias voltage to values in excess of 4V, we were able to bring about local modification of the polymer morphology.
STM imaging of the complete bacterial cell sheath of Methanospirillum hungatei
Authors: Blackford B. L. , Watanabe M. O. , Jericho M. H. , Dahn D. C. 
Published: August 2011

SUMMARYUsing a large range scanning tunnelling microscope (STM) we have obtained images of the complete outer cell wall of the archaebacterium Methanospirillum hungatei, deposited on a graphite substrate and over‐coated with an Au or Pt evaporated film. The width of the collapsed cylindrical sheath structure was found to be 5000 Å ± ***10%, which agrees closely with the value from previously published electron microscope (EM) studies. The double thickness of the collapsed sheath was found to be 160 Å ± 10%, which is about 20% smaller than that from the EM results. Higher resolution STM images taken on top of the collapsed sheaths show corrugations running perpendicular to the cylinder axis and having widths which are multiples of ∼ 30 Å, the minimum period expected from EM studies. The height of the corrugations have a minimum value of about 4 Å. The expected 2‐D crystalline structure was not seen in the STM images.
Effects of sputtering on the surface of graphite
Authors: Nakagiri Nobuyuki , Koga Yasunori , Miyazaki Yasumichi 
Published: August 2011

SUMMARYWe present STM images of the sputtered surfaces of graphite after different sputtering times. The roughness (r.m.s.) and the peak‐to‐valley distance were calculated from the digitized STM signals. The roughness versus etching time graph shows that the roughness increases with etching time initially, but does not change with increased sputtering later. The peak‐to‐valley distance is proportional to the roughness with a coefficient of 8·7. The Fourier transform shows peaks corresponding to the size of mountains created on the sputtered surfaces.
Calculation of the Bloch wall contrast in magnetic force microscopy
Authors: Hartmann U. , Heiden C. 
Published: August 2011

SUMMARYThe magnetic force microscope (MFM) is a promising analytical tool for the mapping of magnetic microfield distributions on a nanometre scale. The detailed interpretation of experimentally obtained data requires a rigorous micromagnetic analysis of the underlying magnetostatic tip‐sample interactions. We have performed model calculations yielding the MFM image contrast obtained for 180° Bloch walls using ferromagnetic microscope tips. The actually observed wall image is shown to depend critically upon the mesoscopic tip design. The spatial resolution and also values for the resulting interaction forces and tip‐sample compliances are derived.
STM imaging of noble metal electrodes in solution under potentiostatic control
Authors: Otsuka I. , Iwasaki T. 
Published: August 2011

SUMMARYWe have combined a three‐electrode cell arrangement with a scanning tunnelling microscope (STM) to image the surfaces of polycrystalline noble metal electrodes under potentiostatic conditions. STM imaging was made in the potential range where a tip and the electrodes are ideally polarized. We have observed on a submicron scale that the electrochemically roughened Ag electrode surface relaxed over times of 40 min at −0·16 V versus SCE in 0·1 m KCl. We have also imaged a dynamic process (formation and dissociation) of the submicron‐scale reconstruction of the Au electrode subjected to electrochemical oxidation‐reduction cycles. The results can be explained by the absorption of Cl− ions and the surface diffusion of adatoms or clusters. STM imaging under potentiostatic control leads to the discovery of phenomena occurring at solid metal/electrolyte interfaces.
Photon emission experiments with the scanning tunnelling microscope
Authors: Coombs J. H. , Gimzewski J. K. , Reihl B. , Sass J. K. , Schlittler R. R. 
Published: August 2011

SUMMARYWe have detected the light emitted from an STM at both ultraviolet (9·5 eV) and optical (1–4 eV) energies. We show that this light contains spectroscopic information on the sample surface comparable to conventional inverse photoelectric spectroscopy, but with nearly atomic spatial resolution. At optical energies we found sufficiently high intensities to allow spatial imaging of the emission probability. We propose that the high quantum efficiency is due to resonance phenomena, and present fluorescence spectra of the emitted light that support this view. We believe that atomic resolution inverse photoemission microscopy and spectroscopy will provide an important new dimension to surface studies.
STM study of the effects of pulsed laser irradiation on semiconductor surfaces
Authors: Tomitori Masahiko , Katsuki Futoshi , Nishikawa Osamu 
Published: August 2011

SUMMARYA clean Si(111) flat surface was irradiated by pulsed Nd‐YAG laser beams. STM observation of the irradiated surfaces indicates that the laser irradiation generates two kinds of corrugations: rounded hills 100 Å high and 600 Å wide and small spikes 20 Å high and 35 Å wide. The corrugations grew and spread with repeated irradiation and increased laser power. The heating of the irradiated surface at 1200°C for 5 s smoothed the surface atomically, but no ordered structure was observed, possibly due to the covering contaminants released from the surfaces surrounding the specimen by laser irradiation and heating.
STM and AFM investigations of high‐Tc superconductors
Authors: Heinzelmann H. , Anselmetti D. , Wiesendanger R. , Hidber H.‐R. , Güntherodt H.‐J. , Düggelin M. , Guggenheim R. , Schmidt H. , Güntherodt G. 
Published: August 2011

SUMMARYWe have studied the (001) surface of single crystal YBa2Cu3O7‐x high‐Tc superconductors using scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) at room temperature at ambient pressure. Both methods show flat terraces with steps which are multiples of the c‐axis lattice constant (of 1·17 nm) high. Our results show that the bulk crystal structure extends to the surface and that the crystals were formed by island growth. Only occasionally tunnelling was possible with sample bias voltages below +1·0 V. We interpret the observed voltage dependence and the difficulty to get good STM images to be due to the presence of a less‐conducting surface layer. Auger spectroscopy indicates that carbon is present at the surface, which is probably related to a contamination layer.
Surface structures of YBa2Cu3O7‐x, BiCa1·7Sr0·7Cu2Ox and TlCaBaCuO4·5±x investigated by scanning tunnelling microscopy
Authors: Laiho R. , Aarnio M. , Heikkilä L. , Snellman H. , Kirschner I. , Halász I. 
Published: August 2011

SUMMARYSurface structures of the high‐Tc superconductors YBa2Cu3O7‐x, BiCa1·7Sr0·7Cu2Ox and TlCaBaCuO4·5±x have been investigated with scanning tunnelling microscopy. The observed features include well‐organized stripe corrugations in Y‐Ba‐Cu‐O as well as orientated flake‐like structures and steps with various heights in the Bi‐ and Tl‐compounds. These observations suggest strong local variations of the elastic and electronic properties of the investigated materials.
Nucleation and growth of Cu and Ag on Si(111)7×7
Authors: Tosch St. , Neddermeyer H. 
Published: August 2011

SUMMARYBy using scanning tunnelling microscopy and spectroscopy we have studied condensation of Cu and Ag on Si(111)7×7 between room temperature and 130°C in the submonolayer and monolayer range. For submonolayer coverage, both metals develop regular clusters on top of the inner adatoms of 7×7 unit cell halves, which we assign to the initial nuclei of metal condensation. The metal film growth continues by adding further metal atoms to these clusters until one half of the 7×7 unit cell is covered completely with a triangular 2‐D metal island. For a coverage of three monolayers neither Cu nor Ag grows in a layer‐by‐layer mode. Characteristic differences observed for both metals may be explained by the more reactive nature of Cu.
Imaging of individual atoms on an Al(111) surface by scanning tunnelling microscopy
Authors: Wintterlin J. , Wiechers J. , Gritsch Th. , Höfer H. , Behm R. J. 
Published: August 2011

SUMMARYDue to the delocalized character of metal valence electrons the atomic corrugation of metal surfaces observed in Scanning Tunnelling Microscopy (STM) is found to be much smaller than in the case of semiconductor surfaces. In fact, there is only a single study in the literature which reports the resolution of the individual atoms on a metal surface (Hallmark et al., 1987). The present paper demonstrates the resolution of individual atoms on a close packed surface of a nearly free electron metal, Al(111), and presents systematic experiments on the physical origin of this phenomenon. A more detailed discussion will be given elsewhere (Wintterlin et al., 1988).
STM study of the structure of the sulphur (1×2) overlayer on molybdenum (001) in air: ordered domains, phase boundaries and defects
Authors: Marchon B. , Ogletree D. F. , Bussell M. E. , Somorjai G. A. , Salmeron M. , Siekhaus W. 
Published: August 2011

SUMMARYA (001) surface of molybdenum, covered by one monolayer of sulphur was prepared in UHV and characterized by LEED, Auger and XPS. This surface was found to be stable in air for periods of several days. STM images of the surface, obtained in air in the topographic and local barrier height modes, revealed the atomic arrangement of sulphur atoms in domains with 1×2 and 2×1 periodicities. Boundaries between domains, adsorbate and substrate defect structures and crystallites formed during the initial oxidation of the Mo substrate were observed.
Electric field‐induced changes of W(110) and W(111) tips
Authors: Neddermeyer H. , Drechsler M. 
Published: August 2011

SUMMARYUsing field emission and scanning electron microscopy we have studied the influence of strong electric fields on the thermally induced growth behaviour of field emission tips. For smaller fields (i.e. smaller than needed for a satisfactory field emission image) we observe an enlargement of low‐index faces, which for higher fields develops into a building‐up of micro‐structures and roughening on the initially spherical part of the tip surface. In an intermediate state only the region near the (111) directions contributes to the field emission pattern. For the highest fields employed the results indicate the growth of local protrusions preferentially near (100) faces. Our results show that in scanning tunnelling microscopy W(111) tips should be superior to the commonly used W(110) tips.
Comparison of LEED and STM measurements of vicinal Si(111)
Authors: Wang X.‐S. , Phaneuf R. J. , Williams E. D. 
Published: August 2011

SUMMARYLEED beam‐profile and STM measurements have been used in combination to study the ordering of stepped Si(111) surfaces misoriented by 4° toward the [***211] direction. LEED measurements show that ordering of the surface steps is dependent on the thermal history of the sample, but give little clue about the reasons. An initial cleaning at 1250°C followed by slow cooling is required to obtain a well‐ordered step structure. STM measurements show that cleaning at a lower temperature (850°C) results in a surface containing highly disordered patches which are possibly correlated with residual carbon. These disordered regions evidently inhibit step order. STM images of rapidly quenched surfaces show a very different sort of disorder consisting of long wavelength (5–10 nm) corrugations of rms vertical amplitude 2 nm.
Scanning tunnelling microscopy of 1‐D and 2‐D charge‐density wave systems
Authors: Gammie G. , Skala S. , Hubacek J. S. , Brockenbrough R. , Lyons W. G. , Tucker J. R. , Lyding J. W. 
Published: August 2011

SUMMARYWe have used a new variable temperature scanning tunnelling microscope (STM) to study quasi‐1D and 2‐D charge‐density wave (CDW) systems. The 1‐D systems, typified by NbSe3 and TaS3, are of special interest since they exhibit unusual transport phenomena associated with moving CDW above a threshold electric field. In the case of NbSe3, room temperature STM images show both major and subtle details of the lattice structure. At present, however, images taken below the Peierls transition temperature of TP=144 K resolve major lattice details but are not sufficiently clear to resolve the CDW. On the other hand, for the fully gapped CDW system orthorhombic‐TaS3, the CDW modulation superimposed on the lattice structure and having the correct period of four times the S‐S spacing of 3·3 Å, is observed below TP=215 K. Above TP, the main observable feature is the S‐S spacing along the chains. STM measurements have also been performed on the 2‐D CDW system 1T‐TaS2 in its incommensurate, nearly commensurate, fully commensurate and trigonal phases. For the nearly commensurate phase, STM images show uniform commensurability with a relatively low concentration of small, time‐varying discommensurations in contrast to models pradicting a regular domain structure. In the trigonal phase, however, evidence is seen for the striped phase composed of long, nearly parallel discommensurations.
Donor graphite intercalation compounds studied with a high stability STM
Authors: Anselmetti D. , Wiesendanger R. , Geiser V. , Hidber H. R. , Güntherodt H.‐J. 
Published: August 2011

SUMMARYWe have designed a small, rigid and easy operable scanning tunnelling microscope (STM) which shows low thermal drift rates due to its compact construction and the chosen materials. Using this instrument we have studied stage 1 donor graphite intercalation compounds (C6Li and C8K) with atomic resolution either in the current imaging, constant current or local tunnelling barrier height mode of operation. Ordered superlattices commensurate as well as incommensurate with the graphite lattice have been observed on the C6Li surface. STM images on C8K revealed a graphitic surface structure.
Anomalous voltage dependence of tunnelling microscopy in WSe2
Authors: Akari S. , Stachel M. , Birk H. , Schreck E. , Lux M. , Dransfeld K. 
Published: August 2011

SUMMARYWe present scanning tunnelling microscopy (STM) investigations of the layered semiconductor WSe2. The tunnelling experiments were performed in air and under silicone oil with markedly different results. In air, atomic resolution images of the hexagonally structured surface could be obtained for sample‐to‐tip voltages of both negative and positive polarities, from −1·5 to −0·3 V for negative sample and from +0·6 to +1·6 V for positive sample, respectively. Under silicone oil, however, good atomic images could be seen for negative sample biases down to at least −14 V, while for positive sample biases no difference with respect to the tunnelling in air was found.
Scanning tunnelling engineering
Authors: Schneiker Conrad , Hameroff Stuart , Voelker Mark , He Jackson , Dereniak Eustace , McCuskey Robert 
Published: August 2011

SUMMARYThe great potential for building molecular scale machines and other structures was first noted by Richard Feynman (1960). He also proposed the development of tools to construct nanoscale mechanisms and devices. The range of technology that he proposed is now called nanotechnology, a term coined by Taniguchi (1974). Emergence of STM and related technology should greatly facilitate the development of nanotechnology in the decades to come. Franks' (1987b) review of nanotechnology notes the tremendous potential of STM‐derived tools for what he terms ‘scanning tunneling engineering’. However, STM technology can also augment the ‘bottom up’ approaches to nanotechnology, exemplified for example by Forrest Carter's (1979, 1980, 1982, 1983) proposals for building molecular electronic devices (nanocomputers) using synthetic ‘modular chemistry’ and related techniques of supramolecular chemistry (Kuhn & Mobius, 1971; Kuhn, 1983; Lehn, 1980, 1988). A multi‐tip STM system integrated with an optical microscope was proposed in 1986 as a ‘nanotechnology workstation’ suitable for scanning tunnelling engineering (Schneiker & Hameroff, 1988). In this paper, we describe an overview of scanning tunnelling engineering, present concepts for nanosensors and nanoswitches, and discuss design considerations for dual tip STM. Finally, we repeat an announcement of a series of ‘Feynman’ prizes for miniature STM.
Limits of topographic measurement by the scanning tunnelling and atomic force microscopes
Authors: Stedman M. 
Published: August 2011

SUMMARYParameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface‐measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude‐wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first‐order analysis the STM and AFM are considered as equivalent to contact‐stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.
Arrangement and stability of atoms at the apex of a scanning tip
Authors: Nishikawa Osamu , Tomitori Masahiko , Katsuki Futoshi 
Published: August 2011

SUMMARYA field ion microscope was used to examine the stability of the atomic arrangement at tip apexes. Although a single W atom at the top layer of a [111]‐orientated tip apex protrudes from the underneath layer by only 0·91 Å, the present study suggests that the (111)‐orientated W tip is the most desirable tip for scanning tunnelling microscopes because a large activation energy for surface diffusion on the (111) plane immobilizes the apex atom while the tip scans over a specimen surface and the tip apex can be resharpened by simply heating the tip.
A fully automated, ‘thimble‐size’ scanning tunnelling microscope
Authors: Lægsgaard E. , Besenbacher F. , Mortensen K. , Stensgaard I. 
Published: August 2011

SUMMARYA novel, fully automated high‐stability, high‐eigenfrequency scanning tunnelling microscope (STM) has been developed. Its key design feature is the application of two piezoelectric ceramic tubes, one for the x‐y‐z motion of the tip and one for a linear motor (‘nano‐worm’) used for the coarse positioning of the tip relative to the specimen. By means of the nano‐worm, the tip can be advanced in steps between 16 and 0·2 nm. The walking distance is >2 mm, with a maximum speed of 2000 steps/s. The nano‐worm positioning implies that this STM is fully controlled by electronic means, and that no mechanical coupling is needed, which makes operation of the STM extremely convenient. The axial‐symmetry construction is rigid, small and temperature‐compensated, yielding reduced sensitivity to mechanical and acoustic vibrations and temperature variations. The sample is simply placed on a piece of invar which surrounds the scanner tube and the nano‐worm and is held by gravity alone. This allows for easy sample mounting. The performance of the microscope has been tested in air by imaging a variety of surfaces, including graphite and biological samples.
A scanning tunnelling microscope for operation in air
Authors: Yao I. E. , Shang G. Y. , Jiao Y. K. , Yi Y. , Bai C. L. , He J. , Zhong J. C. , Rong D. N. 
Published: August 2011

SUMMARYIn this paper a scanning tunnelling microscope for operation in air is described with emphasis on the coarse and fine sample positioning mechanism, piezoelectric scanner and vibration isolation. Line scan (amplitude modulation), top view (brightness modulation) and combined shaded topographical images of the surface of highly orientated pyrolitic graphite are shown.
Influence of adsorbed oxygen on the tunnel current from an Al(111) surface
Authors: Kopatzki E. , Doyen G. , Drakova D. , Behm R. J. 
Published: August 2011

SUMMARYThe tunnel current from an Al(111) surface with an adsorbed oxygen atom into a tungsten tip has been calculated. The tip is represented by a single tungsten atom adsorbed on a flat W(110) surface. The evaluation of the tunnel current is based on the generalized Ehrenfest theorem. The wave functions are obtained as self‐consistent solutions of a model Hamiltonian. The lines of constant tunnel current are similar to those of constant charge density at the Fermi level, but the latter shows fine details which are not discernible in the tunnel current. The main feature is an oxygen induced protrusion of about 0·3 Å height and 5 Å width. The height of the protrusion is nearly unchanged over the investigated range of tip‐sample separations. This contrasts the behaviour of the tunnel current found in a former investigation of the system O/Ni(100), where the oxygen‐induced feature in the contours of constant tunnel current revealed a strong distance dependence. This difference is discussed in terms of the closer equilibrium distance and different screening behaviour for oxygen on Al(111).