| 1. |
- Laegsgaard, E, et al.
(author)
-
A high-pressure scanning tunneling microscope
- 2001
-
In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 72:9, s. 3537-3542
-
Journal article (peer-reviewed)abstract
- We present the design and performance of a high-pressure scanning tunneling microscope (HP-STM), which allows atom-resolved imaging of metal surfaces at pressures ranging from ultrahigh vacuum (UHV) to atmospheric pressures (1 x 10(-10)-1000 mbar) on a routine basis. The HP-STM is integrated in a gold-plated high-pressure cell with a volume of only similar to0.5 l, which is attached directly to an UHV preparation/analysis chamber. The latter facilitates quick sample transfer between the UHV chamber and the high-pressure cell, and allows for in situ chemical and structural analysis by a number of analytical UHV techniques incorporated in the UHV chamber. Reactant gases are admitted to the high-pressure cell via a dedicated gas handling system, which includes several stages of gas purification. The use of ultrapure gasses is essential when working at high pressures in order to achieve well-defined experimental conditions. The latter is demonstrated in the case of H/Cu(110) at atmospheric H-2 pressures where impurity-related structures were observed. (C) 2001 American Institute of Physics.
|
|
| 2. |
- Li, W X, et al.
(author)
-
Oxidation of Pt(110)
- 2004
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:14, s. 146104-
-
Journal article (peer-reviewed)abstract
- Using scanning tunneling microscopy and temperature programed desorption we investigate the Pt(110) surface under strongly oxidizing conditions involving either high-pressure O-2 or atomic oxygen exposure. At low temperatures, only disordered Pt oxide structures are observed. After annealing ordered surface oxide islands are observed to coexist with a highly stable reconstructed (12x2)-O chemisorption structure. From density functional theory calculations a model for the surface oxide phase is revealed. The phase is found to be metastable, and its presence is explained in terms of stabilizing defects in the chemisorption layer and reduced Pt mobility.
|
|
| 3. |
- Pedersen, M O, et al.
(author)
-
Diffusion of N adatoms on the Fe(100) surface
- 2000
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 84:21, s. 4898-4901
-
Journal article (peer-reviewed)abstract
- The diffusion of individual N adatoms on Fe(100) has been studied using scanning tunneling microscopy and ab initio density functional theory (DFT) calculations. The measured diffusion barrier for isolated N adatoms is E-d = (0.92 +/- 0.04) eV, with a prefactor of nu(0) = 4.3 x 10(12) s(-1), which is in quantitative agreement with the DFT calculations. Thr; diffusion is strongly coupled to lattice distortions. and. as a consequence, the presence of other N adatoms introduces an anisotropy in the diffusion. Based on experimentally determined values of the diffusion barriers and adsorbate-adsorbate: interactions, the potential energy surface experienced by a N adatom is determined.
|
|
| 4. |
- Österlund, Lars, 1967-, et al.
(author)
-
Bridging the pressure gap in surface science at the atomic level : H/Cu(110)
- 2001
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 86:3, s. 460-463
-
Journal article (peer-reviewed)abstract
- The structural response of the Cu(110) surface to H-2 gas pressures ranging from 10(-13) to 1 bar is studied using a novel high-pressure scanning tunneling microscope (HP-STM). We find that at H-2 pressures larger than 2 mbar the Cu(110) surface reconstructs into the (1 X 2) "missing-row" structure. From a quantitative analysis of the pressure dependence of the surface reconstruction, we conclude that Cu(110) responds identically to hydrogen at ultrahigh vacuum conditions and at atmospheric pressures. From the HP-STM data, we extract refined values for the adsorption and desorption rate constants.
|
|
