Details
| Original language | English |
|---|---|
| Pages (from-to) | 71-85 |
| Number of pages | 15 |
| Journal | Surface Science |
| Volume | 473 |
| Issue number | 1-2 |
| Publication status | Published - 9 Feb 2001 |
Abstract
Using LEED spot profile analysis (SPA-LEED) and thermal programmed desorption spectroscopy (TDS), the pure Kr/NaCl(1 0 0) system and its mixture with Xe has been studied. As substrate thin epitaxial NaCl films on a Ge(1 0 0) substrate have been used. Kr in the monolayer (MC) regime forms a faint (2×1)pmg structure with glide plane symmetry, whereas the second layer forms a quadratic lattice with a lattice constant close to the Kr bulk value. From the phase diagram for Kr condensation into the first and second monolayer heats of condensation of 9.5±2 and 9.0±2 kJ/mol have been derived, respectively. These are significantly lower than those obtained from TDS. Mixtures of Kr with preadsorbed Xe have been studied for preadsorbed Xe coverages 0≤ΘXe≤3 ML under isobaric Kr pressures between 10-7≤pKr≤10-6 mbar and at surface temperatures between 35≤T≤60 K. Emphasis is put on investigations of the first monolayer. The phase transition of Kr condensation into the first monolayer is shifted to higher transition temperature and broadens for the mixtures. Whereas no new ordered structures have been observed compared with the pure Xe and Kr systems, atomic mixture in the first layer is confirmed by the observation of a continuously varying average lattice constant in one direction between the (2×1)pmg and the distorted hexagonal structure of Xe. A miscibility gap depending on T, pKr and ΘXe is found. At Tc of Kr condensation in the first layer, the solubilities are sKr to approximately 0.25 and sXe to approximately 0.3. For pKr>5×10-7 mbar the miscibility gap closes prior to the transition to a Kr three-dimensional layer. The mixture of Kr into the first layer of Xe is even observed for preadsorbed Xe coverages above one monolayer.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Condensed Matter Physics
- Physics and Astronomy(all)
- Surfaces and Interfaces
- Materials Science(all)
- Surfaces, Coatings and Films
- Materials Science(all)
- Materials Chemistry
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In: Surface Science, Vol. 473, No. 1-2, 09.02.2001, p. 71-85.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Kr and Xe on NaCl(1 0 0)
T2 - Pure phases and their miscibility
AU - Budde, K.
AU - Schimmelpfennig, J.
AU - Eichmann, M.
AU - Ernst, W.
AU - Pfnür, Herbert
N1 - Funding information: This work was supported by the Deutsche Forschungsgemeinschaft through Forschergruppe “Adsorbatwechselwirkungen an Ionenkristallen und Metallen”.
PY - 2001/2/9
Y1 - 2001/2/9
N2 - Using LEED spot profile analysis (SPA-LEED) and thermal programmed desorption spectroscopy (TDS), the pure Kr/NaCl(1 0 0) system and its mixture with Xe has been studied. As substrate thin epitaxial NaCl films on a Ge(1 0 0) substrate have been used. Kr in the monolayer (MC) regime forms a faint (2×1)pmg structure with glide plane symmetry, whereas the second layer forms a quadratic lattice with a lattice constant close to the Kr bulk value. From the phase diagram for Kr condensation into the first and second monolayer heats of condensation of 9.5±2 and 9.0±2 kJ/mol have been derived, respectively. These are significantly lower than those obtained from TDS. Mixtures of Kr with preadsorbed Xe have been studied for preadsorbed Xe coverages 0≤ΘXe≤3 ML under isobaric Kr pressures between 10-7≤pKr≤10-6 mbar and at surface temperatures between 35≤T≤60 K. Emphasis is put on investigations of the first monolayer. The phase transition of Kr condensation into the first monolayer is shifted to higher transition temperature and broadens for the mixtures. Whereas no new ordered structures have been observed compared with the pure Xe and Kr systems, atomic mixture in the first layer is confirmed by the observation of a continuously varying average lattice constant in one direction between the (2×1)pmg and the distorted hexagonal structure of Xe. A miscibility gap depending on T, pKr and ΘXe is found. At Tc of Kr condensation in the first layer, the solubilities are sKr to approximately 0.25 and sXe to approximately 0.3. For pKr>5×10-7 mbar the miscibility gap closes prior to the transition to a Kr three-dimensional layer. The mixture of Kr into the first layer of Xe is even observed for preadsorbed Xe coverages above one monolayer.
AB - Using LEED spot profile analysis (SPA-LEED) and thermal programmed desorption spectroscopy (TDS), the pure Kr/NaCl(1 0 0) system and its mixture with Xe has been studied. As substrate thin epitaxial NaCl films on a Ge(1 0 0) substrate have been used. Kr in the monolayer (MC) regime forms a faint (2×1)pmg structure with glide plane symmetry, whereas the second layer forms a quadratic lattice with a lattice constant close to the Kr bulk value. From the phase diagram for Kr condensation into the first and second monolayer heats of condensation of 9.5±2 and 9.0±2 kJ/mol have been derived, respectively. These are significantly lower than those obtained from TDS. Mixtures of Kr with preadsorbed Xe have been studied for preadsorbed Xe coverages 0≤ΘXe≤3 ML under isobaric Kr pressures between 10-7≤pKr≤10-6 mbar and at surface temperatures between 35≤T≤60 K. Emphasis is put on investigations of the first monolayer. The phase transition of Kr condensation into the first monolayer is shifted to higher transition temperature and broadens for the mixtures. Whereas no new ordered structures have been observed compared with the pure Xe and Kr systems, atomic mixture in the first layer is confirmed by the observation of a continuously varying average lattice constant in one direction between the (2×1)pmg and the distorted hexagonal structure of Xe. A miscibility gap depending on T, pKr and ΘXe is found. At Tc of Kr condensation in the first layer, the solubilities are sKr to approximately 0.25 and sXe to approximately 0.3. For pKr>5×10-7 mbar the miscibility gap closes prior to the transition to a Kr three-dimensional layer. The mixture of Kr into the first layer of Xe is even observed for preadsorbed Xe coverages above one monolayer.
UR - http://www.scopus.com/inward/record.url?scp=0035250957&partnerID=8YFLogxK
U2 - 10.1016/S0039-6028(00)00955-9
DO - 10.1016/S0039-6028(00)00955-9
M3 - Article
AN - SCOPUS:0035250957
VL - 473
SP - 71
EP - 85
JO - Surface Science
JF - Surface Science
SN - 0039-6028
IS - 1-2
ER -