H.-J. Güntherodt

Universität Basel, Bâle, Basel-City, Switzerland

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Publications (331)707.61 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this note we report the first observation of salient features of the Si(111)(7×7) reconstructed surface across monatomic steps by dynamic atomic force microscopy (AFM) in ultrahigh vacuum (UHV). Simultaneous measurements of the resonance frequency shift Δf of the Si cantilever and of the mean tunneling current from the cleaned Si tip indicate a restricted range for stable imaging with true atomic resolution. The corresponding characteristics vs. distance reveal why feedback control via Δf is problematic, whereas it is as successful as in conventional STM via . Furthermore, local dissipation (energy loss of 10-14 W) through individual atoms is observed and explained by the coupling of the surface atoms to phonons.
    Surface Review and Letters 01/2012; 04(05). · 0.28 Impact Factor
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    ABSTRACT: Some examples are selected to demonstrate the variety of possible scanning probe microscopy application in industry. Magnetic and magneto-optical storage media can be investigated by magnetic force microscopy, whereas a conventional scanning force microscope is used to examine surface features of many different materials, such as technical glasses, photosensitive materials, new superconductors, and biomolecules. Some other examples include the modification as well as the observation of liquid crystal devices, and the impact that scanning probe microscopy has on other techniques such as high precision stepping motors and high quality electron beam sources.
    Scanning 08/2011; 15(5):257 - 264. · 1.29 Impact Factor
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    ABSTRACT: The atomic force microscope (AFM) offers the possibility to image the topography of insulating as well as conductive surfaces. Highly oriented pyrolytic graphite (HOPG) was chosen as an example for a layered material and compared to single crystalline lithium fluoride (LiF). Both materials are easily prepared and inert at ambient pressure. Furthermore they are well characterized by Helium atom scattering experiments and other techniques.On HOPG atomic resolution has been achieved. Distortions can be observed which we interpret as a frictional effect. In addition we performed large area scans where we seldomly observed dislocations. For the first time we present measurements on LiF, showing steps of one unit cell height. On larger areas the surface of LiF showed terraces, separated by steps of variable heights, ranging from a few ångströms to 100 Å.We used a static method to get information about the distance dependence of the force between lever and sample. By slowly expanding and retracting the sample piezo and simultaneous measurement of the lever deflection, plots were recorded, showing the force as a function of sample position. The results were compared with theoretical calculations. We could determine the tip radius and found differences between LiF and HOPG being characteristic for the samples.
    Journal of Microscopy 08/2011; 152(1):269 - 280. · 1.63 Impact Factor
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    ABSTRACT: We 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.
    Journal of Microscopy 08/2011; 152(2):509 - 514. · 1.63 Impact Factor
  • U. D. SCHWARZ, H. HAEFKE, P. REIMANN, H.‐J. GÜNTHERODT
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    ABSTRACT: Since its invention in 1986, scanning force microscopy (SFM) has experienced great success as a characterization method for topography on small scales. In spite of the enormous potential of the method, it is limited by the quality of the tip used for probing the surface topography. Convolutions of non-ideal tip shapes with the real topography and tip bending, flexing and jumping effects produce artefacts in the resulting images.A brief description of the preparation and characteristics of the most commonly used SFM tips is given. A variety of different artefacts originating from tip properties is presented and illustrated with selected scanning force micrographs. Methods to minimize tip artefacts in SFM images are described.
    Journal of Microscopy 08/2011; 173(3):183 - 197. · 1.63 Impact Factor
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    ABSTRACT: We 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.
    Journal of Microscopy 08/2011; 152(2):399 - 405. · 1.63 Impact Factor
  • Th. Lacoste, Th. Huser, H. Heinzelmann, H.-J. Güntherodt
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    ABSTRACT: We have constructed two scanning near-field optical microscopes (SNOM) for optical imaging with resolutions exceeding Rayleigh’s diffraction limit. One instrument is of the aperture-SNOM type and is equipped with shear-force feedback for probe to sample distance control. Combined with a conventional light microscope for easy sample location, this instrument is well suited for the investigation of biological materials. The second instrument relies on optical tunneling (STOM) from a light beam totally reflected at the sample/air interface into a conventional force microscope probe tip. The combination of near-field optical microscopy with force microscopy allows correlation of optical sample properties with surface structure. Microfabricated test structures have been imaged.
    07/2011: pages 123-132;
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    ABSTRACT: Rubbed polymer layers are commonly used for the fabrication of liquid crystal devices. The rubbing process creates an anisotropic surface morphology, aligning liquid crystal molecules. A similar anisotropy can be created by scratching the surface using a scanning force microscope operating at high loads (10-7 to 10-5N). We have found that these scratched areas show an orientational effect on liquid crystals similar to the rubbing process. This method allows the fabrication of arbitrarily shaped retractive index patterns in the liquid crystal in the µm regime. A variety of prototypes of optically relevant structures such as waveguides, optical gratings and the basic structure for a Mach-Zehnder interferometer have been fabricated by this method.
    02/2011: pages 319-324;
  • MRS Online Proceeding Library 01/2011; 270.
  • H.‐J. Güntherodt
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    ABSTRACT: The magnetic susceptibility of liquid metals and their alloys is reviewed and discussed in terms of current theories. For liquid simple metals the susceptibility is interpreted in terms of the free-electron model. The magnetic properties of transition and rare earth metals can be explained by taking into account the itinerant d-electrons and the localized f-electrons, respectively. The present state of the magnetic properties of non-metallic fluids having metallic constituents is reported. In such systems the magnetic susceptibility gives information on the pseudogap or helps to elucidate the ionic character.Es wird über Messungen der magnetischen Suszeptibilität flüssiger Metalle und Legierungen berichtet und die Ergebnisse im Rahmen neuerer Theorien diskutiert. Einfache flüssige Metalle erfüllen das Modell für Elektronen gut. Die magnetischen Eigenschaften der Übergangsmetalle und der Metalle der Seltenen Erden werden ganz wesentlich durch die d- und f-Elektronen bestimmt. Der gegenwärtige Stand der magnetischen Eigenschaften nichtmetallischer Flüssigkeiten, die metallische Komponenten enthalten, wird beleuchtet. In diesen Systemen kann die magnetische Suszeptibilität Aufschluß über das Pseudogap oder den ionischen Charakter der Schmelze geben.
    Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 80(8):753 - 757.
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    ABSTRACT: A scanning force microscope was used to measure the frequency shift above various atomic sites on a NaCl(001) surface at 7 K. The data was converted to force and compared to the results of atomistic simulations using model NaCl and MgO tips. We find that the NaCl tip demonstrates better agreement in the magnitude of the forces in experiments, supporting the observation that the tip first came into contact with the sample. Using the MgO tip as a model of the originally oxidized silicon tip, we further demonstrate a possible mechanism for tip contamination at low temperatures.
    Physical Review B 07/2008; 74(24). · 3.66 Impact Factor
  • E. Meyer, H.-J. Güntherodt, H. Haefke, G. Gerth, M. Krohn
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    ABSTRACT: Surfaces of epitaxially grown AgBr(001) films have been examined by atomic force microscopy. Terraced-growth hills and pits as well as screw dislocations are observed and typical step heights are found to be 2.9 Å, which correspond to one atomic layer. At higher magnification, atomic resolution is achieved. The protrusions are regularly arranged in a square lattice having a spacing of 4.1 Å. Comparison with the contact hard-sphere model and theoretical calculations indicate that the protrusions can be attributed to the bromine ions, whereas the smaller silver ions are not observed. The results are discussed in relation to other techniques such as the noble-metal decoration.
    EPL (Europhysics Letters) 07/2007; 15(3):319. · 2.26 Impact Factor
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    ABSTRACT: Superconductivity with an onset temperature of 27.5 K has been found in samples of a nominal composition (RbTl1.5)3C60. Investigations of the d.c. magnetization, the a.c. susceptibility as well as preliminary results of 13C NMR and STM studies are reported.
    EPL (Europhysics Letters) 07/2007; 17(5):419. · 2.26 Impact Factor
  • R. Wiesendanger, G. Tarrach, D. Bürgler, H.-J. Güntherodt
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    ABSTRACT: We have used scanning tunnelling microscopy to investigate the Si(111) 7×7 reconstruction on narrow terraces separated by multiple-step edges as high as several nanometers. Atomic resolution with a corrugation of up to 2.5 Å could be achieved on both sides of these multiple step edges indicating a remarkable stability of the scanning tip. Besides the alignment of the step direction, we have studied defects in the vicinity of the step edges. Such defects occur preferentially on the lower terrace adjacent to a step edge, which can be explained by the growth behaviour of the 7×7 phase upon cooling.
    EPL (Europhysics Letters) 07/2007; 12(1):57. · 2.26 Impact Factor
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    ABSTRACT: Atomic resolution has been obtained on a magnetite (Fe3O4(001)) surface using a scanning tunnelling microscope with nonmagnetic tungsten and ferromagnetic iron tips. Selective imaging of Fe2 + and Fe3 + on B-sites is achieved by using the ferromagnetic Fe probe tip, reflecting the different spin configurations of the two magnetic ions. Local order in the distribution of Fe2 + and Fe3 + on the (001) surface is found at room temperature, well above the bulk order-disorder (Verwey) transition.
    EPL (Europhysics Letters) 07/2007; 19(2):141. · 2.26 Impact Factor
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    ABSTRACT: We present scanning tunnelling micrographs of C60 molecules deposited on polycrystalline platinum, a substrate which enables stable imaging in contrast to other investigated substrate materials. On a submicron scale, we observe layers of C60 molecules separated by monomolecular steps. Individual C60 molecules can be imaged with submolecular resolution. These submolecular features can possibly be attributed to carbon atoms or to bonds of the C60 molecule.
    EPL (Europhysics Letters) 07/2007; 18(1):29. · 2.26 Impact Factor
  • H. P. Lang, T. Frey, H.-J. Güntherodt
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    ABSTRACT: Scanning tunnelling microscopy (STM) is applied to investigate the surface structure of high-quality c-axis oriented laser-ablated thin YBa2Cu3O7-δ-films. The main features of the surface are steps of one-unit cell height documenting the two-dimensional growth process of the epitaxial film. For the first time atomic resolution with STM is achieved, indicating a 3.8 Å square lattice on YBa2Cu3O7-δ laser-ablated films, as expected from diffraction techniques. Screw dislocations and holes of different sizes are the most frequently observed types of lattice defects in these films.
    EPL (Europhysics Letters) 07/2007; 15(6):667. · 2.26 Impact Factor
  • T. M. Schaub, D. E. Bürgler, H.-J. Güntherodt
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    ABSTRACT: Amorphous Pd81Si19 is studied by scanning tunneling microscopy before and after crystallization, and after additional laser-quenching. Distances between structural units on the amorphous surface are comparable to lattice spacings on the crystallized sample indicating partial preservation of the local structure during the phase transformation. After laser-quenching the crystallized sample, the surface structure is similar to that of the initial amorphous state proving on the nm scale the successful transformation of the surface layers back into the amorphous state.
    EPL (Europhysics Letters) 01/2007; 36(8):601. · 2.26 Impact Factor
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    ABSTRACT: Copper-Octaethyl Porphyrin self-assembly has been studied on NaCl islands, 1–3 monolayers thick, grown on metal substrates. Extended ordered molecular monolayers are observed for the first time on ultrathin insulator films. The assembly occurs in hierarchical fashion, starting on the metal substrate, then followed by assembly on the first and second NaCl layers, clearly demonstrating a decrease in adsorption energy for increasing insulator layer thickness. The underlying mechanisms are discussed on the basis of molecule–sub-strate interactions. Voltage-dependent STM images reveal differences of the electronic structure for molecules adsorbed on metal and NaCl/metal areas.
    Chemical Physics Letters 11/2005; 417(1). · 2.15 Impact Factor
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    ABSTRACT: We present a fully remote controllable AFM, featuring a motorized four-axis sample stage. The low cost robotics allows a fast and accurate change of pre-defined positions. Due to the software interface the instrument can be programmed to perform sequences of measurements. This allows the automated acquisition of large scale high resolution images. The instrument can be controlled and monitored from various locations using a standard network interface.
    12/2003;

Publication Stats

4k Citations
707.61 Total Impact Points

Institutions

  • 1975–2012
    • Universität Basel
      • • Institut für Physiologie
      • • Department of Physics
      Bâle, Basel-City, Switzerland
    • University of Bristol
      Bristol, England, United Kingdom
  • 1998–2005
    • Paul Scherrer Institut
      • Laboratory of Micro and Nanotechnology (LMN)
      Aargau, Switzerland
    • Technische Universität Clausthal
      • Department of Physical Chemistry
      Bergstadt-Clausthal-Zellerfeld, Lower Saxony, Germany
  • 1990–1994
    • Freie Universität Berlin
      • Institute of Experimental Physics
      Berlin, Land Berlin, Germany
  • 1993
    • Johannes Gutenberg-Universität Mainz
      • Institute of Organic Chemistry
      Mayence, Rheinland-Pfalz, Germany
  • 1966–1973
    • ETH Zurich
      • Laboratory for Solid State Physics
      Zürich, ZH, Switzerland