Udo Linke

An in-situ STM study of anion adsorption on Pt(111) from sulfuric acid solutions

Abstract Electrochemical in-situ STM under clean conditions has been applied to monitor the anion adlattice on Pt(111) in sulfuric acid solution at atomic scale resolution. The maxima observed in the STM images are arranged in a centered ( 2 1 1 2 ) structure. This structure was found in the potential range between 0.5 V and 0.7 V RHE. The structure is interpreted as a coadsorbate of anions and a solvent species which both form a primitive ) 2 1 1 2 ) adlattice with a coverage of 20% of a monolayer.

Adsorbate-induced surface stress: sulfur, oxygen and carbon on Ni(100)

Abstract We have determined the surface stress induced by the adsorption of sulfur, oxygen and carbon on Ni(100). As a result of a strong adsorbate-substrate interaction of these strongly chemisorbed systems, all adsorbates induce a considerable compressive surface stress on Ni(100). The c(2 × 2)-structures of sulfur, oxygen and carbon cause a surface stress of -6600 ± 924dyn/cm, -7500 ± 1050dyn/cmand -8500 ± 1190dyn/cm, respectively. The magnitude of the oxygen- and carbon-induced surface stress is in agreement with total-energy.calculations, whereas the stress induced by sulfur is surprisingly high. Our results on C/Ni(100) support the concept of surface stress as the driving force surface reconstruction.

Restructuring of the vicinal Cu(997) surface

Abstract We have investigated the surface structure of Cu(111) vicinal surfaces with (111)- and (100)-steps using scanning tunneling microscopy and scanning electron microscopy. While the vicinal surface with (100)-steps displays the expected typical step arrays after ultra-high vacuum (UHV) preparation, the surface with (111)-steps becomes macroscopically rough. Scanning tunneling microscope (STM) images of this surface reveal the presence of {212} facets and triangular tiling structures with a {445} mean orientation. The {212} facets consist of (111) double steps and (111) terraces. The triangular tiling structure consists of triangular shaped (111) terraces which are separated by straight (100) and zigzag shaped (111)-steps in alternate sequence. It is proposed that the observed structures represent local minima in the free energy of the surface which are more easily accessible than the true equilibrium structure under the kinetic constraints of a large Schwoebel—Ehrlich barrier.

Preparation of bead metal single crystals by electron beam heating

For the fabrication of small metal bead crystals a gas flame is used to melt a wire forming a liquid droplet which solidifies upon cooling into a single crystal metal bead. Due to oxidation under ambient conditions bead crystals can be formed only from noble metals using this method. Here we describe a method how to fabricate bead crystals from a wide variety of metals and metal alloys (Cu, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, Pt, Au, PtPd, Pd80Pt20, PtRh, AuAg, and PtIr) by electron beam heating under vacuum conditions. Narrow x-ray diffraction peaks confirm a high crystal quality of the bead crystals.

Metal bead crystals for easy heating by direct current

The preparation of metal bead crystals with two wires attached to the crystal is described. These crystals allow for a very easy and efficient method to heat metal single crystals by direct current heating through the connecting wires of the bead crystal. This heating of the bead crystal is sufficient to clean metal surfaces such as the surfaces of Pt and Au as confirmed by Auger spectroscopy and scanning tunneling microscopy (STM). There is no need for any ion sputtering which is conventionally used to clean metal single crystal surfaces. The bead crystals with two leads fabricated from a wide range metals and metal alloys such as Cu, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, Pt, Au, PtPd, PtRh, AuAg, and PtIr can be used as general purpose metal substrates for surface science studies and other applications. Additionally, these bead crystals can be used to reshape STM tips by indentation of the tip into the soft metal in order to recover atomic resolution imaging on hard substrates.