| 1. |
- Nyholm, R., et al.
(författare)
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EPITAXIAL SILICIDE FORMATION IN THE MG/SI(111) SYSTEM
- 1993
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 289:3, s. 290-296
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Tidskriftsartikel (refereegranskat)abstract
- The silicide formation has been studied in the Mg/Si(111) system by IOW energy electron diffraction (LEED) and photoelectron spectroscopy. It has been found that an epitaxial Mg2Si silicide is responsible for the (2/3 square-root e x 2/3 square-root 3)R30-degrees reconstruction in this system. The thickness of the silicide is limited due to the very low formation temperature for this silicide. The Fermi level is positioned 0.59 +/- 0.06 eV above the valence band maximum in the Si substrate and the valence band maximum in the epitaxial silicide is positioned 0.3 +/- 0.1 eV below the Fermi level.
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| 2. |
- Nyholm, R., et al.
(författare)
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FORMATION OF SM SILICIDES ON SI(111) - COMPOSITION AND EPITAXY
- 1993
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 293:3, s. 254-259
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Tidskriftsartikel (refereegranskat)abstract
- The formation of Sm silicides on Si(111) by means of solid phase epitaxy has been studied with low energy electron diffraction, Auger electron spectroscopy and photoelectron spectroscopy of the Sm 4f level and Si 2p level. A limited reaction is found to occur already at room temperature whereas at higher temperatures a strongly intermixed Sm/Si layer showing some long range order is formed. The Sm atoms of this intermixed phase are found to be completely trivalent in accordance with expectations. The intermixed layer consists of two silicides with different compositions, one of them being SmSi2-x, the other being tentatively ascribed to SmSi.
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| 3. |
- Sandell, A, et al.
(författare)
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Metalorganic Chemical Vapor Deposition of Anatase Titanium Dioxide on Si: Modifying the Interface by Pre-Oxidation.
- 2003
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 530:1-2, s. 63-70
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Tidskriftsartikel (refereegranskat)abstract
- The formation of TiO2 films on clean and pre-oxidized Si(1 1 1) through chemical vapor deposition of titanium(IV) isopropoxide (TTIP) in ultra-high vacuum has been examined by synchrotron radiation photoelectron spectroscopy, X-ray absorption spectroscopy (XAS) and scanning tunneling microscopy. In both cases, TTIP deposition at 500 °C eventually results in an anatase TiO2 film with a carbon-free surface and the surface morphology of the anatase films is very similar. By using a novel way of combining photoemission and XAS data, it is demonstrated that the two situations have substantially different interfacial properties. Pre-oxidation of the surface at 500 °C passivates the surface so that the thickness of the amorphous TiSixOy interface layer decreases from 30–35 to 15–25 Å and eliminates the formation of interfacial carbon completely.
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| 4. |
- Almqvist, Nils
(författare)
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Fractal analysis of scanning probe microscopy images
- 1996
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 355:1-3, s. 221-228
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Tidskriftsartikel (refereegranskat)abstract
- The accuracy and precision of several algorithms, including newly developed, for calculating the fractal dimension from scanning probe microscopy images of material surfaces are investigated. The algorithms are based on the area-perimeter method, a variance method or versions of the structure function method. The latter two methods show good correspondence to computer simulated images, with known fractal dimensions, and have successfully been applied also on real images. The results show that these two methods give reliable fractal dimensions and are well suited to describe surface roughness quantitatively.
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| 5. |
- Amandusson, Helena, et al.
(författare)
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Methanol induced hydrogen permeation through a Pd membrane
- 1999
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 442:2, s. 199-205
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Tidskriftsartikel (refereegranskat)abstract
- The dehydrogenation of methanol and the subsequent permeation of hydrogen through a 25 μm thick palladium film has been studied in a catalytic membrane reactor. At the temperature studied, 350°C, the decomposition pathway for methanol on clean palladium surfaces is believed to lead to Had and a carbonaceous overlayer. The released hydrogen can either desorb or permeate the palladium membrane. During a continuous supply of methanol hydrogen permeation is reduced and, eventually, totally quenched by the growing carbon monoxide/carbon coverage. Adding oxygen in the methanol supply can balance the increasing carbonaceous coverage through the production of carbon dioxide. In such a case, it is concluded that no CO bond scission occurs. The methanol/oxygen ratio is crucial for the hydrogen permeation rate. Isotope-labelled methanol, CH3OH, CH3OD, CD3OH and CD3OD, shows that it is preferentially the methyl (or methoxy) hydrogen that permeates the membrane.
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| 6. |
- Andersson, C B M, et al.
(författare)
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Bulk and surface electronic structure of InAs(110)
- 1998
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 398:3, s. 395-
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Tidskriftsartikel (refereegranskat)abstract
- The InAs(110) cleavage surface has been investigated by angle-resolved photoelectron spectroscopy. A separation between the In 4d(5/2) bulk component and the valence band maximum of 16.8 eV is found to be consistent with normal emission spectra. Experimental energy band dispersions, E-i(k), for the four bulk valence bands are established along the Sigma-line of the bulk Brillouin zone. A bulk band structure calculation utilizing the augmented plane-wave method is made. The experimental and calculated E-i(k) dispersions are found to be in good agreement with each other. E-i(k(parallel to)) dispersions for two surface-related structures are established along the lines <(Gamma)over bar>-(M) over bar and (Y) over bar-(M) over bar of the surface Brillouin zone. (C) 1998 Elsevier Science B.V.
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| 7. |
- Andersson, C B M, et al.
(författare)
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Surface atomic structure of InAs((111)over-bar)2x2 and InSb((111)over-bar)2x2 studied by core level spectroscopy
- 1996
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 347:1-2, s. 199-206
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Tidskriftsartikel (refereegranskat)abstract
- Surface sensitive high resolution core level spectroscopy has been applied to the molecular beam epitaxy grown InAs((111) over bar)2 x 2 and InSb((111) over bar)2 x 2 surfaces. For both systems the In 4d core level consists of one dominating component while the Group V core levels are deconvoluted into four components. This analysis is consistent with a surface model where the topmost layer consists entirely of arsenic or antimony. In this model, Group V atoms form trimers bound to Group V atoms in the first double layer, leaving a single Group V rest atom per unit cell.
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| 8. |
- ANDERSSON, CBM, et al.
(författare)
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SPUTTERED AND ANNEALED INAS(111)OVER-BAR - AN UNRECONSTRUCTED SURFACE
- 1994
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 307, s. 885-889
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the InAs(111BAR)1 X 1 surface has been investigated by angle resolved photoelectron spectroscopy along the symmetry lines GAMMAKBAR, GAMMAMBAR, and GAMMAMBAR of the surface Brillouin zone. The bulk valence band structure was calculated using a combination of the linear augmented plane-wave method and the relativistic augmented plane-wave method. We have projected the theoretical bulk band structure onto the surface Brillouin zone to separate surface states from surface resonances. Two surface related structures, S1 and S2, have been observed and their E(i)(k(parallel-to)) dispersions are established. Both S1 and S2 show the symmetry of the 1 X 1 surface Brillouin zone, which is consistent with the observed 1 X 1 LEED pattern. We identify S1 as the As-derived dangling bond state, and S2 is associated with the backbonds connecting the As atoms in the surface layer with the underlying In layer.
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| 9. |
- Baudin, Micael, et al.
(författare)
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A molecular dynamics study of MgO(111) slabs
- 1997
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 375:2-3, s. 374-384
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Tidskriftsartikel (refereegranskat)abstract
- Constant stress - constant temperature molecular dynamics simulations are reported for 30 Angstrom thick crystalline MgO (111) slabs with 2-D periodicity in the temperature range 10-1100 K. The 10 K run was 3.75 ps, the 300 K run was 41.25 ps while the others were 11.25 ps. The shell-model potential was used and the long-range interaction was taken into account with the 2-D Ewald summation technique. Two different models have been used in order to achieve the necessary charge compensation for the polar (111) surface. The relaxation of the surface structure and its temperature dependence have been investigated and compared with bulk MgO. The average coordination number in the surface layer and the surface energy are presented. The dynamics in the slab system is presented in terms of atomic mean-square displacements and vibrational density-of-states curves as a function of depth from the surface. (C) 1997 Elsevier Science B.V.
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| 10. |
- Baudin, M., et al.
(författare)
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Dynamics, structure and energetics of the (111), (011) and (001) surfaces of ceria
- 2000
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 468:03-jan, s. 51-61
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations for 20-30 Angstrom thick CeO2 slabs with 2-D periodicity are presented. The three low-index surfaces investigated are(lll), (011) and (001). The simulations were performed within a constant-temperature-constant-pressure ensemble and used the shell-model to describe polarizability. All simulation runs were performed at atmospheric pressure and in the temperature range 10-1100 K. For all three surfaces at both 300 and 1100 K, we find that the surface m.s. displacements are generally larger for the oxide ions than for the cations and that the out-of-plane surface motion is usually larger than the in-plane surface motion. At room temperature, the oxygen m.s. displacements at the (Ill)surface are a factor 1.2 larger than in the bulk, a factor 1.6 for the (011) surface and approximately five times larger at the metastable (001) surface compared to the bulk. The effect of the presence of a surface on the ion dynamics [and on the structure for (011)] persists all the way to the slab centres. even for these rather thick slabs. Our simulations for the polar (001) surface demonstrate that the relative stabilities of different faces and surface terminations can change with temperature, and that it may not always be meaningful to consider one specific user-prepared termination as superior to the others.
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