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  • 1
    Electronic Resource
    Electronic Resource
    A variable pressure/temperature scanning tunneling microscope for surface science and catalysis studies (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 687-691 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design and construction of a scanning tunneling microscope (STM), which is contained in a reactor cell and allows in situ operation throughout a wide range of pressures and temperatures. This STM is capable of imaging in pressures ranging from ultrahigh vacuum up to several atmospheres. Samples can also be easily moved in and out of the STM cell in a small separate vacuum transfer chamber for external characterization and treatment. The equilibration time and stability of the microscope after temperature changes was determined at atmospheric pressures, by monitoring the evolution of atomically resolved images of highly oriented pyrolytic graphite at temperatures ranging from 300 to 425 K. We have also examined the stability when flowing gases are used instead of stationary pressures. In preliminary experiments using Pt(111) and (110) crystals, we have observed the effect of atmospheres of H2 and O2 on the structure of these surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144198
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Coadsorbate induced compression of sulfur overlayers on Re(0001) and Pt(111) by CO (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6092-6097 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Low coverages of sulfur chemisorbed on the rhenium(0001) and platinum(111) surfaces were studied in UHV by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). On both of these surfaces of triangular symmetry the lowest coverage (≈0.25 monolayers) ordered structure is p(2×2). Exposure of this ordered sulfur overlayer on either surface to low pressures (10−9 Torr) of CO induces compression of the sulfur layer to a structure associated with a higher local coverage and CO chemisorbs in the holes created in the sulfur layer. The reordering was observed by both a change in the LEED pattern and by real space STM imaging of the surface. On the Re surface the new overlayer has (3(square root of)3×3(square root of)3)R30° symmetry, while on the Pt surface it has ((square root of)3×(square root of)3)R30° symmetry. There was no increase in the amount of sulfur on the surface during this reordering. On both surfaces the overlayers could be returned to the original p(2×2) by annealing for several seconds at 600 °C, during which CO desorbs and sulfur atoms reoccupy the vacant metal sites. This phenomenon of the compression of atoms in a strongly chemisorbed layer upon coadsorption of another molecule provides a mechanism for carrying out catalytic reactions on metal surfaces that are covered with strongly chemisorbed layers that do not participate in the reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467121
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A scanning tunneling microscope that operates at high pressures and high temperatures (430 K) and during catalytic reactions (1992)
    Springer
    Catalysis letters 14 (1992), S. 263-269 
    Details
    ISSN: 1572-879X
    Keywords: Scanning tunneling microscopy ; STM ; in situ ; platinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We describe the construction and operation of a scanning tunneling microscope (STM) designed in our laboratory that is contained in a reaction cell and allows operation throughout a wide range of pressures (ultra-high vacuum-atmospheric) and temperatures (300–425 K). This thermally compensated, double piezo tube design is entirely mechanically clamped. Samples are inertially translated and can be easily transferred in and out of the STM. With this microscope, we have investigated the stability of Pt(110) as a function of oxygen and hydrogen pressure and temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769663
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Monitoring surfaces on the molecular level during catalytic reactions at high pressure by sum frequency generation vibrational spectroscopy and scanning tunneling microscopy (1995)
    Springer
    Catalysis letters 34 (1995), S. 11-18 
    Details
    ISSN: 1572-879X
    Keywords: in situ catalysis ; propylene hydrogenation ; STM ; SFG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sum frequency generation (SFG), using non-linear laser optics, detects vibrational spectra of submonolayer amounts of adsorbates with excellent energy and time resolution. Scanning tunneling spectroscopy (STM) is sensitive to the atomic surface structure; readily imaging defects, steps and kinks as well as stationary adsorbed species. Both of these techniques can be used during reactions at high pressures and temperatures to obtain molecular information in situ. We report studies of propylene hydrogenation over Pt(111) crystal surfaces at atmospheric pressures and 300 K using SFG and STM. Four surface species (2-propyl, π-bonded propylene, di σ-bonded propylene, and propylidyne) were identified; the first two being implicated as reaction intermediates. The platinum surface structure remains unchanged during the reaction, consistent with the structure insensitive nature of olefin hydrogénation. Propylene decomposition induced substantial surface reconstruction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808316
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Spatially (nanometer) controlled hydrogenation and oxidation of carbonaceous clusters by the platinum tip of a scanning tunneling microscope operating inside a reactor cell (1996)
    Springer
    Catalysis letters 39 (1996), S. 5-17 
    Details
    ISSN: 1572-879X
    Keywords: catalysis ; nanofabrication ; STM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrocarbon clusters formed by the thermal decomposition of propylene on Pt(111) were rehydrogenated or oxidized with nanometer spatial resolution using the platinum tip of a scanning tunneling microscope (STM) at 300 K in atmospheric pressures of H2 or O2. The reaction rate shows a strong dependence on the oxygen or hydrogen pressures and on the tip-surface separation. The reaction stops when the Pt tip becomes contaminated with carbon, after the removal of ∼107–108 carbon atoms, but can be regenerated by removing material from the tip by application of a voltage pulse. Dissociative adsorption of H2 and O2 on the tip, followed by transfer of atoms to the surface is the proposed mechanism of these tip-catalyzed reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813723
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    Paper (German National Licenses)
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