Tuning the surface structure and conductivity of niobium-doped rutile TiO2 single crystals via thermal reduction

2017 ◽  
Vol 19 (45) ◽  
pp. 30339-30350 ◽  
Author(s):  
D. Wrana ◽  
C. Rodenbücher ◽  
M. Krawiec ◽  
B. R. Jany ◽  
J. Rysz ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Structural Changes ◽  
High Vacuum ◽  
Thermal Reduction ◽  
Ultra High Vacuum ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Systematic Exploration ◽  
Niobium Doped

We report on the systematic exploration of electronic and structural changes of Nb-doped rutile TiO2(110) single crystal surfaces due to the thermoreduction under ultra-high vacuum conditions (without sputtering), with comparison to undoped TiO2(110) crystals.

Heteroepitaxial Growth of MgO Films on NiO(100) Single Crystal Surfaces

1994 ◽  
Vol 357 ◽  
Author(s):  
S. Imaduddin ◽  
A.M. Davidson ◽  
R.J. Lad
Keyword(s):  
Single Crystal ◽  
Lattice Mismatch ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Heteroepitaxial Growth ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Oxygen Anions ◽  
Mgo Layers

AbstractEpitaxial MgO layers were grown on cleaved NiO(100) single crystal surfaces. The less than 1% lattice mismatch between MgO and NiO allows almost ideal epitaxy of MgO at 100°C. The epitaxial films were created by dosing Mg onto stoichiometric NiO(100) both in ultra-high vacuum (UHV) and in an O2 atmosphere (5×10−7 Torr). Chemical interactions at the resulting interfaces were studied using XPS. When Mg is dosed onto NiO(100) in UHV, MgO forms by interacting with oxygen anions in the NiO substrate thereby reducing the nickel cations. Metallic Mg layers begin to form upon subsequent dosing. When Mg is deposited in O2, epitaxial MgO(100) layers grow to a thickness of at least 50Å as confirmed by in situ RHEED and LEED observations. Negligible intermixing between the MgO and NiO is observed during growth at 100°C and on subsequent annealing in UHV up to 600°C.

CO adsorption on (100) and (211) tungsten single-crystal surfaces: Changes in work function

1968 ◽  
Vol 46 (8) ◽  
pp. 949-958 ◽  
Author(s):  
R. A. Armstrong
Keyword(s):  
Single Crystal ◽  
Work Function ◽  
Single Crystals ◽  
Room Temperature ◽  
Co Adsorption ◽  
Major Effect ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Tungsten Single Crystal ◽  
Adsorption Of Co

The adsorption of CO on two large single crystals of tungsten exposing (100) and (211) surfaces has been studied by measuring changes in the work function [Formula: see text] at 300 °K and above, where some CO remained adsorbed. The results for the two surfaces were quite different.CO adsorbed on the clean W(100) surface at room temperature as β-CO causing [Formula: see text] to increase by 0.48 V. As β adsorption saturated, α-CO adsorption began and caused [Formula: see text] to decrease. The major effect of heating was desorption.CO adsorbed on the clean W(211) surface with a sticking probability near unity and increased [Formula: see text] by 0.68 V. Heating the crystal to temperatures below 1100 °K produced large irreversible changes in [Formula: see text]. These irreversible changes are attributed to the formation and dissociation on the surface of complexes consisting of two CO molecules.

scholarly journals An Affordable Option to Au Single Crystals Through Cathodic Corrosion of a Wire: Fabrication, Electrochemical Behavior, and Applications in Electrocatalysis and Spectroscopy

2020 ◽  
Author(s):  
Mohamed Elnagar ◽  
Johannes M. Hermann ◽  
Timo Jacob ◽  
Ludwig A. Kibler
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Surface Enhanced Raman Spectroscopy ◽  
Acid Oxidation ◽  
Active Surface Area ◽  
Scanning Electron Micrographs ◽  
Crystal Surfaces ◽  
Active Centers ◽  
Single Crystal Surfaces ◽  
Electrode Potentials

Faceting and nanostructuring of polycrystalline gold electrodes by cathodic corrosion in concentrated potassium hydroxide electrolytes has been systematically studied at different electrode potentials. Current-potential curves for the restructured Au electrodes in 0.1 M H2SO4 show characteristic features of Au(111) facets in the double-layer and oxidation region. Thus, the modified Au electrodes adopt properties typically known for well-defined single crystal surfaces. Besides the preferential surface faceting, the electrochemically active surface area (EASA) is enhanced as a function of potential, concentration and time. Scanning electron micrographs show the formation of well-defined triangular pits and nanostructures with a specific orientation confirming the formation of (111)-facets. In this way, the behavior of single crystals is accompanied with the properties of nanoparticles which are of utmost interest in electrocatalysis and surface enhanced Raman spectroscopy (SERS). The electrocatalytic activity of the newly formed “Au(111)” surface from an Au wire has been tested towards the hydrogen evolution reaction (HER) and for the formic acid oxidation reaction (FAOR). The study of electrocatalytic reactions at these nanostructured electrodes allows to identify active centers, which are absent for extended single crystal surfaces. Adsorbed pyridine on the nanostructured Au electrodes directly shows SERS activity, while untreated polycrystalline Au is SERS-inactive. The use of cathodic corrosion of simple wires is a paradigm of SERS-applications in electrochemistry with clean Au electrodes that provide properties of Au(111) single crystals.

The Use of Leed for the Characterization of Surface Damage from Pulsed Laser Irradiation

1985 ◽  
Vol 48 ◽  
Author(s):  
Aubrey L. Helms ◽  
Chin-Chen Cho ◽  
Steven L. Bernasek ◽  
Clifton W. Draper
Keyword(s):  
Thermal Stresses ◽  
Profile Analysis ◽  
High Vacuum ◽  
Surface Damage ◽  
Laser Pulses ◽  
Ultra High Vacuum ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Laser Fluences ◽  
Dislocation Sources

ABSTRACTLow Energy Electron Diffraction (LEED)-Spot Profile Analysis and Auger Electron Spectroscopy (AES) have been used to study the response of Mo(100) single crystal surfaces to Q-switched, frequency doubled Nd:YAG laser pulses. The experiments were conducted in a special ultra-high vacuum (UHV) system which allowed the surfaces to be irradiated under controlled conditions. Laser fluences both above and below the melt threshold were employed. For the melted surfaces, good epitaxial regrowth was observed. The spot profile analysis indicates the formation of random islands on the surfaces. Surfaces which had been previously disordered by 3 KeV Ar+ implantation were laser surface melted and observed to regrow epitaxially as has been observed in the case of ion implanted silicon. The formation of the islands and stepped structures is explained by considering the activation of dislocation sources by the induced thermal stresses resulting in slip.

scholarly journals An Affordable Option to Au Single Crystals Through Cathodic Corrosion of a Wire: Fabrication, Electrochemical Behavior, and Applications in Electrocatalysis and Spectroscopy

2020 ◽  
Author(s):  
Mohamed Elnagar ◽  
Johannes M. Hermann ◽  
Timo Jacob ◽  
Ludwig A. Kibler
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Surface Enhanced Raman Spectroscopy ◽  
Acid Oxidation ◽  
Active Surface Area ◽  
Scanning Electron Micrographs ◽  
Crystal Surfaces ◽  
Active Centers ◽  
Single Crystal Surfaces ◽  
Electrode Potentials

Faceting and nanostructuring of polycrystalline gold electrodes by cathodic corrosion in concentrated potassium hydroxide electrolytes has been systematically studied at different electrode potentials. Current-potential curves for the restructured Au electrodes in 0.1 M H2SO4 show characteristic features of Au(111) facets in the double-layer and oxidation region. Thus, the modified Au electrodes adopt properties typically known for well-defined single crystal surfaces. Besides the preferential surface faceting, the electrochemically active surface area (EASA) is enhanced as a function of potential, concentration and time. Scanning electron micrographs show the formation of well-defined triangular pits and nanostructures with a specific orientation confirming the formation of (111)-facets. In this way, the behavior of single crystals is accompanied with the properties of nanoparticles which are of utmost interest in electrocatalysis and surface enhanced Raman spectroscopy (SERS). The electrocatalytic activity of the newly formed “Au(111)” surface from an Au wire has been tested towards the hydrogen evolution reaction (HER) and for the formic acid oxidation reaction (FAOR). The study of electrocatalytic reactions at these nanostructured electrodes allows to identify active centers, which are absent for extended single crystal surfaces. Adsorbed pyridine on the nanostructured Au electrodes directly shows SERS activity, while untreated polycrystalline Au is SERS-inactive. The use of cathodic corrosion of simple wires is a paradigm of SERS-applications in electrochemistry with clean Au electrodes that provide properties of Au(111) single crystals.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

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