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1.	Sandell, A, et al. (författare) Metalorganic Chemical Vapor Deposition of Anatase Titanium Dioxide on Si: Modifying the Interface by Pre-Oxidation. 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 530:1-2, s. 63-70 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.
2.	Baudin, M., et al. (författare) Dynamics, structure and energetics of the (111), (011) and (001) surfaces of ceria 2000 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 468:03-jan, s. 51-61 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.
3.	Baudin, M., et al. (författare) Metal oxide surface dynamics from molecular dynamics simulations : the alpha-Al2O3(0001) surface 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 474:03-jan, s. 107-113 Tidskriftsartikel (refereegranskat)abstract Constant-stress, constant-temperature (10, 300 and 700 K) molecular dynamics simulations were carried out with shell-model potentials for an infinite crystalline A-terminated alpha -Al2O3(000 1) slab of similar to 25 Angstrom thickness. The surface undergoes considerable relaxation at 10 K, but exhibits ordered surface structures at all three temperatures. The relaxation causes the (0 0 0 1) surface at 10 K to appear oxygen-terminated. The ionic motion within the central and surface regions of the slab system has been analysed in terms of mean-square displacements. At room temperature the (u(2))(surface)/(u(2))(bulk) ratio for the Al ions is approximate to2.5 and when only the out-of-plane surface motion is considered the ratio is as large as approximate to3.5. The O ion motion at the surface is slightly smaller than that of the cations.
4.	Edwards, NV, et al. (författare) Real-time assessment of selected surface preparation regimens for 4H-SiC surfaces using spectroscopic ellipsometry 2000 Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 464:1, s. L703-L707 Tidskriftsartikel (refereegranskat)abstract Spectroscopic ellipsometry (SE) was used to assess the removal of overlayer material from 4H-SiC (0001) and (0001) [Si- and C-face] surfaces in real time and, in particular, the critical final step of an otherwise standard RCA cleaning regimen commonly used to prepare SiC surfaces for contact formation. The treatments selected [buffered hydrofluoric acid (HF), concentrated HF, and dilute HF] removed 4-40 Angstrom of effective SiO2 overlayer thickness from these surfaces. The concentrated HF treatment yielded the best surface, i.e. that with the most abrupt transition region between bulk and surface and with the most oxide material removed. A fourth treatment regimen (sequential application of methanol, water, and 5% HF in methanol) was also developed for comparison with the full RCA clean. (C) 2000 Elsevier Science B.V. All rights reserved.
5.	Fahlman, Mats, et al. (författare) Surfaces and interfaces in polymer-based electronics 2002 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 500:1-3, s. 904-922 Tidskriftsartikel (refereegranskat)abstract Research on electronics applications such as light-emitting devices for flat-panel displays, transistors, sensors and even solid state lasers based on conducting polymers is presently under way and in some cases has reached the stage of prototype production. The mechanisms for charge injection and conduction in these materials are being studied, as are the physics of luminescence and its quenching. Lately, research into controlling film morphology through self-organizing techniques also has gained interest. Though the present interest in conducting polymers mainly concerns the pristine semiconducting state, doped conducting polymers are also studied for potential use in many applications. In this paper, we present an overview of some of the central issues in surface and interface science in the field, as well as provide our view on what may lie ahead in the future. Specifically, the importance of metal/polymer, polymer/metal and polymer/polymer interfaces is addressed. We illustrate these using polymer-based light-emitting devices, though the same type of issues appear in other polymer-based applications such as transistors and solar cells. © 2001 Elsevier Science B.V. All rights reserved.
6.	Giovanelli, L., et al. (författare) Synchrotron radiation photoelectron spectroscopy study of Pb-Pc thin films on InSb(100)-(4x2)/c(8x2) 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 486:02-jan, s. 55-64 Tidskriftsartikel (refereegranskat)abstract The electronic properties and the thermal stability of a thin film of lead-phthalocyanine deposited on the InSb(100)-(4 x 2)/c(8 x 2) surface were studied by synchrotron radiation core level and valence band photoelectron spectroscopy. The interaction between the overlayer and the substrate was determined by analyzing the photoemission spectra of a thin film and of a single monolayer of adsorbed molecules. Subsequently the monolayer was annealed at increasing temperatures, leading first to a gradual change of the oxidation state of the central lead atom, then to a fragmentation of the macrocycle itself.
7.	Glans, P.-A., et al. (författare) Core level and valence band photoemission study of the (1 1 1) and (1¯ 1¯ 1¯) surfaces of 3C-SiC 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 470:3, s. 284-292 Tidskriftsartikel (refereegranskat)abstract A core level and valence band photoemission study of thick 3C-SiC(1 1 1) and 3C-SiC(1¯ 1¯ 1¯) epilayers grown by sublimation epitaxy is reported. The as introduced samples show threefold 1×1 low-energy electron diffraction patterns. For the Si face v3 and 6v3 reconstructed surfaces develop after in situ heating to 1100 °C and 1300 °C, respectively. For the C face a 3×3 reconstruction form after heating to 980 °C. A semiconducting behavior is observed for the v3 and 3×3 reconstructed surfaces while the 6v3 reconstruction show a Fermi edge and thus a metallic-like behavior. The surface state on the v3 surface is investigated and found to have ?1 symmetry and a total band width of 0.10 eV within the first surface Brillouin zone. For the Si2p and C 1s core levels binding energies and surface shifted components are extracted and compared to earlier reported results for 6H- and 4H-SiC.
8.	Habermehl-Cwirzen, Karin, et al. (författare) An experimental study on adsorption of benzene on Co(0001) 2002 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 507, s. 57-61 Tidskriftsartikel (refereegranskat)abstract The adsorption of benzene on Co(0 0 0 1) was studied by X-ray photoelectron spectroscopy, temperature programmed desorption, low energy electron diffraction (LEED) and work function measurements. The adsorption was found to be molecular at room temperature and to saturate at a fractional coverage of 0.125 ML. With LEED a c(2root3 x 4) overlayer structure was seen. Below 220 K at high exposures a p(root7 x root7)R19degrees LEED pattern was observed corresponding to a coverage of 0.143 ML. Temperature programmed desorption measurements stated that benzene starts to decompose around 340 K to hydrogen and a hydrocarbon fragment, most likely C6H5. While the hydrogen desorbed, the hydrocarbon stayed at the surface. The desorption of molecular benzene was negligible. The activation energy for the dehydrogenation was calculated to be about 102 kJ/mol. The work function of Co(0 0 0 1) decreased by 1.3 eV upon saturation with benzene. The induced dipole moment was calculated to be 1.9 Debye/molecule.
9.	Hirschauer, B., et al. (författare) Oxidation of Ce on Si(111) studied by high-resolution photoelectron spectroscopy 2000 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 464:03-feb, s. 117-122 Tidskriftsartikel (refereegranskat)abstract The Si(lll)-Ce (2x2) surface was studied by photoelectron spectroscopy during oxidation and annealing. Detailed analysis of the Si 2p core-level spectra and the Ce valence band levels shows that Ce is first oxidised and then promotes oxidation of Si at room temperature by improving the oxygen uptake of the surface. Initially, no oxidation of Si can be recorded, but at exposures of 3 L O-2 or more, SiOx and higher silicon oxides are formed. After annealing to 750 degreesC, a temperature that is generally used to oxidise Si, almost all O leaves the surface. At 1045 degreesC, the Si 2p and the Ce valence band spectra of the sample show almost the same shape as for the original Si(lll)-Ce 2x2 surface. This means that oxidation/reduction of the Si(lll)-Ce 2x2 surface is reversible.
10.	Janin, Emmanuelle, et al. (författare) Adsorption and bonding of propene and 2-butenal on Pt(111) 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 482, s. 83-89 Tidskriftsartikel (refereegranskat)abstract The adsorption of propene and 2-butenal on the Pt(1 1 1) surface has been studied by high resolution photoelectron spectroscopy, both in the mono-and multi-layer regime. The results obtained indicate an involvement of both aliphatic and carbonyl groups in the bonding of 2-butenal with the platinum surface in the sub-monolayer regime.
11.	Janin, E., et al. (författare) Corrosive adsorption of Sn on the Pt(110)(1 x 2) surface 2002 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 515:03-feb, s. 462-470 Tidskriftsartikel (refereegranskat)abstract Room temperature deposition of Sn on the Pt(110)(1 x 2) surface has been studied by scanning tunnelling microscopy and core level photoelectron spectroscopy. At low coverage Sri is found in three different configurations; as mobile adatoms in the valley of the missing-row reconstruction, as 1D-Pt-Sn-Pt- alloy chains forming local Pt3Sn(110)2 x 2 regions and finally as 3D alloy islands. At higher coverage these islands form a platinum rich alloy film, which is dissolved in the crystal upon annealing to 600 degreesC.
12.	Jemander, S.T., et al. (författare) STM study of the surface defects of the (v3×v3)-Sn/Si(1 1 1) surface 2001 Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 475:1-3, s. 181-193 Tidskriftsartikel (refereegranskat)abstract The (v3×v3)-Sn/Si(1 1 1) surface has been studied with scanning tunneling microscopy (STM) and Auger electron spectroscopy, and it is found that it contains basically five different types of defects originating from substitutional atoms and vacancies. The influence the defects have on their immediate neighbourhood is investigated and found to extend to the third nearest (v3×v3) adatom neighbour. Close to some defect constellations, a very local (3×3) periodicity in the apparent height in the STM images is found. This periodicity is shown to be a linear superposition of the perturbations generated by the individual defects in the constellations. The superposition of the height modulation is accurate and linear for a wide range of tip biases, as for combinations of different types of defects. Its linearity is explained in terms of small perturbations in the surface electronic structure. We also provide an explanation why the linearity breaks down when large perturbations are probed with small tip biases.
13.	Johansson, Leif, et al. (författare) Properties of the SiO2/SiC interface investigated by angle resolved studies of the Si 2p and Si 1s levels and the Si KLL Auger transitions 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 529:3, s. 515-526 Tidskriftsartikel (refereegranskat)abstract Angle resolved photoemission studies of the Si 2p and Si 1s core levels and the Si KL2,3L2,3 Auger transitions from SiO2/SiC samples are reported. Most samples investigated were grown in situ on initially clean and well ordered v3 × v3 reconstructed 4H-SiC(0 0 0 1) surfaces but some samples were grown ex situ using a standard dry oxidation procedure. The results presented cover samples with total oxide thicknesses from about 5 to 118 Å. The angle resolved data show that two oxidation states only, Si+1 and Si+4, are required to explain and model recorded Si 2p, Si 1s and Si KLL spectra. The intensity variations observed in the core level components versus electron emission angle are found to be well described by a layer attenuation model for all samples when assuming a sub-oxide (Si2O) at the interface with a thickness ranging from 2.5 to 4 Å. We conclude that the sub-oxide is located at the interface and that the thickness of this layer does not increase much when the total oxide thickness is increased from about 5 to 118 Å. The SiO2 chemical shift is found to be larger in the Si 1s level than in the Si 2p level and to depend on the thickness of the oxide layer. The SiO2 shift is found to be fairly constant for oxides less than about 10 Å thick, to increase by 0.5 eV when increasing the oxide thickness to around 25 Å and then to be fairly constant for thicker oxides. An even more pronounced dependence is observed in the Si KLL transitions where a relative energy shift of 0.9 eV is determined. The relative final state relaxation energy dR(2p) is determined from the modified Auger parameter. This yields a value of dR(2p) = -1.7 eV and implies, for SiO2/SiC, a "true" chemical shift in the Si 2p level of only ˜0.4 eV for oxide layers of up to 10 Å thick. © 2003 Elsevier Science B.V. All rights reserved.
14.	Karlsson, Fredrik, 1974-, et al. (författare) Effective tuning of the charge-state of single In(Ga)As/GaAs quantum dots by below barrier band gap excitation 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 532-535, s. 843-847 Tidskriftsartikel (refereegranskat)abstract The existence of a well-defined threshold energy, crucial for the charging of quantum dots (QDs), positioned between the barrier band gap and the wetting layer ground state is demonstrated. Optical excitation with energies above this threshold populates the QDs with extra electrons. The origin of the threshold is discussed in terms of acceptors in the GaAs barrier. ⌐ 2003 Elsevier Science B.V. All rights reserved.
15.	Larsson, Mats, 1976-, et al. (författare) Photoluminescence study of Si/Ge quantum dots 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 532-535, s. 832-836 Tidskriftsartikel (refereegranskat)abstract Ge quantum dots embedded in Si are studied by means of photoluminescence (PL). The temperature dependent PL measurements show two different types of recombination processes related to the quantum dots. We ascribe a peak near 0.80 eV to the spatially indirect recombination in the type-II band lineup where the electron is located in the surrounding Si close to the interface and the hole in the Ge dot. Furthermore, a peak near 0.85 eV is attributed to the spatially direct recombination. We observe a transition from the spatially indirect to the spatially direct recombination as the temperature is increased. The measurements also show an up-shift of the Ge quantum dot emission energy with increasing excitation power density. The blueshift is primarily ascribed to an enhanced confinement of the electron associated with the increased band bending at the type-II Si/Ge interface at high carrier densities. Comparison is made with results, derived from measurements on uncapped samples. For these uncapped samples, no energy shifts due to excitation power or temperatures are observed in contrast to the capped samples. ⌐ 2003 Elsevier Science B.V. All rights reserved.
16.	Münger, Peter, et al. (författare) Adatom/vacancy interactions and interlayer mass transport in small two-dimensional Pt clusters on Pt(1 1 1) 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 539:1-3 Tidskriftsartikel (refereegranskat)abstract We use embedded-atom molecular dynamics simulations to follow the dynamics of adatoms, vacancies, and adatom/vacancy pairs on two-dimensional hexagonal Pt19 clusters on Pt(1 1 1) surfaces at 1000 K. All configurations are found to be quite stable and have essentially the same migration mobilities as compact hexagonal clusters. However, the presence of a single vacancy dramatically decreases the lifetime of an adatom on the cluster by a factor of three. This occurs primarily through an enhancement of the rate of push-out/exchange reactions at the outer cluster edge resulting from vacancy-induced softening of edge atom bonds. Overall, adatoms in the presence of vacancies descend to the terrace via vacancy filling 10% of the time, and through reactions with outer cluster edges the remaining 90%. Direct vacancy filling mechanisms are analogous to, and have similar activation energies with, those at outer cluster edges: adatom hopping over descending steps and push-out/exchange reactions. © 2003 Elsevier B.V. All rights reserved.
17.	O'Shea, J. N., et al. (författare) Hydrogen-bond induced surface core-level shift in pyridine carboxylic acids 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 486:3, s. 157-166 Tidskriftsartikel (refereegranskat)abstract Intermolecular hydrogen bonding in thick films of pyridine carboxylic acids (isonicotinic; picolinic and bi-isonicotinic acid) evaporated onto rutile TiO2(1 1 0) has been investigated with X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. These molecules are shown to be strongly H-bonded in the condensed phase, and a surface core-level shift is observed due to the presence of non-H-bonded nitrogen atoms in the surface layer. Density functional theory calculations are used to relate the experimental data to the proposed bonding configurations based on the surface termination of the known equilibrium solid-state structure. A kinetic barrier, attributed to the high degree of molecular orientation required for the formation of extended H-bonding networks, has also been investigated.
18.	Papageorgiou, N., et al. (författare) Lead phthalocyanine thin films on InAs(100)-(4 x 2)/c(8 x 2) studied by synchrotron radiation photoelectron spectroscopy 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 482, s. 1199-1204 Tidskriftsartikel (refereegranskat)abstract We used synchrotron radiation photoelectron spectroscopy to study the interface between a thin film and an ordered single monolayer of lead phthalocyanine (PbPc) deposited on the clean InAs(1 0 0)-(4 x 2)/c(8 x 2) reconstructed surface. Analysis of the core level and valence band spectra gave information about the electronic properties of the interface, the interaction between the molecule and the substrate and the valence band offset of the heterojunction.
19.	Paul, Jan, et al. (författare) Carbon dioxide activation and alkali compound formation. I : Vibrational characterization of oxalate intermediates 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 531:3, s. 244-264 Tidskriftsartikel (refereegranskat)abstract The activation of CO2 in thin potassium layers adsorbed on Cu(1 1 1) has been studied with time-evolved Fourier transform-infrared reflection absorption spectroscopy. The growth of thin layers by reactive evaporation of potassium in a CO2 atmosphere permits control of the K:CO2 stoichiometry, which strongly affects the selectivity in the formation of intermediates and the decomposition pathways of the layer. Layers grown in a CO2 rich atmosphere exhibit the preferential growth of stoichiometric potassium oxalate K2C2O4 (D2h). The molecular identity of oxalate with D2h symmetry is confirmed by vibrational spectra utilizing isotopic substitution methods (13CO2 and C18O2) and by the use of isotopic mixtures of CO2/C18O2 and CO2/13CO2. A comparison of the isotope data with theoretical calculations gives an estimated OCO bond angle in oxalate of 132°. Far-IR spectra obtained with synchrotron radiation indicate the equivalent interaction of all oxygen atoms with the potassium. A comparison of the vibrational data with theoretical ab initio calculations confirms the structural model of an oxalate species that is bulk coordinated with no strong directional bonding and all oxygen atoms equally interacting with potassium. At medium and low CO2:K ratios, very complex vibrational spectra are observed, indicating the formation of an oxalate surface species with C2v symmetry in addition to D2h- oxalate, CO2- and CO22- species.
20.	Sakamoto, K., et al. (författare) High-resolution Si2p core-level and low-energy electron diffraction studies of the Ca/Si(1 1 1)-(3 × 2) surface 2003 Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 532-535, s. 628-632 Tidskriftsartikel (refereegranskat)abstract We have investigated the surface structure of the Ca/Si(1 1 1)-(3 × 2) surface using low-energy electron diffraction (LEED) and high-resolution core-level photoelectron spectroscopy. Weak ×2 streaks were observed in LEED at 300 K. After cooling the sample to 100 K, ×2 spots, which originate from both (3 × 2) and c(6 × 2) periodicities, appeared. By considering the energy shift and intensity of each surface component observed in the Si2p core-level spectra, we conclude that the structure of the (3 × 2) surface is basically the same as that of the honeycomb-chain-channel model with a Ca coverage of 1/6 ML. Further, we propose that the weak ×2 streaks at 300 K result from thermally induced disorder. © 2003 Elsevier Science B.V. All rights reserved.
21.	Sinner-Hettenbach, M., et al. (författare) Electronic structure of SnO2(110)-4 x 1 and sputtered SnO2(110) revealed by resonant photoemission 2002 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 499:1, s. 85-93 Tidskriftsartikel (refereegranskat)abstract The surface properties of SnO2(1 1 0)-4 x 1 and sputtered SnO2(1 1 0) were studied comparatively by resonant photoemission of the valence band states in a photon energy range of 60-130 eV. Resonating energetic levels could be observed on the 4 x I reconstructed surface and the resonance behavior could be switched off by sputter treatment. Additionally, the Sn 4d core-levels were recorded at two photon energies in order to allow a statement about the surface's stoichiometry. A tentative explanation of the observed resonance and of the discrepancy between ordered and sputtered surface is given with regard to recent STM results on similar prepared surfaces.
22.	Sinner-Hettenbach, M., et al. (författare) Oxygen-deficient SnO2(110) : a STM, LEED and XPS study 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 477:1, s. 50-58 Tidskriftsartikel (refereegranskat)abstract The reconstruction process of SnO2(110) was investigated by scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). The high-temperature 1 x 1 reconstruction could be identified as an intermediate face, transferable either to the 1 x 2 surface by annealing to higher temperature or back to the 4 x 1 reconstruction by annealing again at lower temperature. In this way, a new method to prepare well-ordered 4 x 1 terminated surfaces is introduced and the O/Sn ratio as well as the core-level positions of Sn 3d and O 1s were traced by XPS over a temperature range of 700-1200 K on freshly sputtered and on low-temperature long-time annealed SnO2(110). STM images of the 1 x 1 surface show a new structure of in-plane oxygen, ordered locally in zigzag rows that contribute to the LEED pattern as a very diffuse 2 x 1 intensity.
23.	Tarre, A, et al. (författare) Nanoepitaxy of SnO2 on á-Al2O3(0 1 2) 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 532-535:SI, s. 514-518 Tidskriftsartikel (refereegranskat)
24.	Virojanadara, Chariya, et al. (författare) Effects of nitrogenmonoxide on 4H-SiC(0 0 0 1) 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 530:1-2, s. 17-25 Tidskriftsartikel (refereegranskat)abstract Effects induced by nitrogenmonoxide (NO) exposures on the v3 × v3 R30° reconstructed 4H-SiC(0 0 0 1) surface are reported. NO exposures from 0.3 to 1 × 106 L at a substrate temperature of 800 °C are investigated. Recorded Si2p spectra show three shifted components, besides the bulk SiC peak. These are assigned to originate from SiO2, N-Si-O and Si3N4/Si+1 (since we cannot distinguish between Si3N4 and an Si+1 oxidation state). It can be concluded that SiO2 does grow on top of N-Si-O and that Si3N4/Si+1 is located at the interface. Two N1s components are observed after NO exposures. A main one, located at around 398.05 eV, assigned to originate from Si3N4 and a weaker one suggested to correspond to N-Si-O bonding. The assignments are made using Si2p and N1s spectra collected after NH3 and O2 exposures under similar conditions. No graphite like carbon or carbon by-product at the interface can be detected after large NO or O2 exposures. © 2003 Elsevier Science B.V. All rights reserved.
25.	Virojanadara, Chariya, et al. (författare) Letter: Interfacial investigation of in situ oxidation of 4H-SiC 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 472:1-2 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract An in situ oxidation study of v3 × v3 R30° reconstructed 4H-SiC(001) surfaces is reported. An intermediate oxidation state (interpreted to be Si+1) is revealed in core level photoemission spectra recorded from the in situ prepared SiO2/4H-SiC samples. Oxidation was made at a pressure of ~10-3 Torr in flowing oxygen and at substrate temperatures from 600°C to 950°C. The highest oxidation rate was obtained at 800°C when ˜25 Å thick SiO2 layers were prepared. The surface related C 1s components observed on the clean reconstructed 4H-SiC(0001) surfaces were found to disappear after oxidation. No carbon or carbon containing by-product at the interface or in the oxide were possible to observe for the films grown.
26.	Virojanadara, Chariya, et al. (författare) Metastable oxygen adsorption on SiC(0 0 0 1)-v3 × v3 R30° 2002 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 519:1-2, s. 73-78 Tidskriftsartikel (refereegranskat)abstract Initial oxygen adsorption at different temperatures on the SiC(0 0 0 1)- v3 × v3 R30° surface has been studied using photoemission. Oxygen exposures with the sample at 800 °C results in formation of stable oxides. However, after small exposures (0.1-10 L) with the sample at room temperature or cooled to ˜100 K additional structures appear in the O 1s spectrum that are identified to originate from metastable oxygen. Similar additional structures were recently revealed on Si(111)-7 × 7 and suggested to originate from adsorption of metastable molecular oxygen in an ins-paul configuration. © 2002 Elsevier Science B.V. All rights reserved.
27.	Virojanadara, Chariya, et al. (författare) Oxidation studies of 4H-SiC(0001) and (0001) 2002 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 505:1-3, s. 358-366 Tidskriftsartikel (refereegranskat)abstract The results of a photoemission study of Si- and C-terminated 4H SiC surfaces after different oxygen exposures are presented and discussed. The surfaces were oxidized gradually from 1 to 1.2 x 10(6) L at both room temperature and at 800 degreesC. Recorded Si 2p and C 1s spectra show at both temperatures only two oxidations states, Si1- and Si4- for the Si-terminated surface and Si2+ and Si4+ for the C-terminated surface, For the Si-terminated surface, no carbon containing by-product can be detected at the interface or at the surface after the largest exposure investigated. For the C-terminated surface, oxygen exposures are shown to affect the surface related carbon components quite strongly and the Si2+ oxidation state is interpreted to originate from a mixture of Si-O-C bonding, The surface/interface related carbon decreases dramatically after the largest exposure investigated but is not eliminated as on the Si-terminated surface. For the latter, a clean and well ordered root3 surface is shown to be possible to re-create by in situ heating even after the largest oxygen exposures made. (C) 2002 Elsevier Science B.V. All rights reserved.
28.	von Schenck, H., et al. (författare) CO bonding on tin modified Pt(110)-(1 x 2) 2003 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 526:02-jan, s. 184-192 Tidskriftsartikel (refereegranskat)abstract The influence of tin on the bonding of CO to Pt(l 10) has been studied using high-resolution electron energy loss spectroscopy, density functional theory and photoelectron spectroscopy. CO binds on-top to platinum at all investigated tin and CO coverages. Bonding of CO in Sn-Pt alloy rows is weakened compared to clean Pt(l 10). However, several different adsorption sites in Pt-only rows, inequivalent with regard to their coordination environment, show very similar characteristics with respect to CO adsorption.
29.	Wadsak, M., et al. (författare) Combined in-situ investigations of atmospheric corrosion of copper with SFM and IRAS coupled with QCM 2000 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 454, s. 246-250 Tidskriftsartikel (refereegranskat)abstract Scanning force microscopy (SFM) and infrared reflection absorption spectroscopy (IRAS) coupled with quartz crystal microbalance (QCM) were used for in-situ investigations of the atmospheric corrosion of pure copper. Based on chemical and kinetic studies obtained by IRAS/QCM, tapping mode atomic force microscopy (TM-AFM) and phase detection imaging (PDI) were applied to gain information about the topography changes of the sample surface with emphasis on the shape and lateral distribution of the corrosion products. Investigations were carried out in synthetic air with 60 and 80% relative humidity (RI-I). At 60% RH, small features partly covering the surface could be observed with TM-AFM. These features were identified as cuprous oxide with IRAS. Contrary to these results, a fast formation of a layer of cuprous oxide entirely covering the sample surface was observed at 80% RH with TM-AFM. QCM investigations showed a higher formation rate of cuprous oxide at 80% than at 60% RH but in both cases, a high corrosion rate at the beginning of the exposure, which decreases with progressing time.
30.	Weissenrieder, Jonas, et al. (författare) Investigation of the surface phase diagram of Fe(110)-S 2002 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 515:1, s. 135-142 Tidskriftsartikel (refereegranskat)abstract Reconstructions and overlayer structures of the Fe(110) surface at different sulfur (S) coverage are presented by atomically resolved scanning tunneling microscopy combined with Auger electron spectroscopy and low energy electron diffraction investigations. S overlayers were obtained by annealing a Fe(110) single crystal to 700 degreesC in order to induce S segregation from the bulk. Fe(110)c(6 x 4), (3 x 1) and (1 x 1) reconstructions were found at sub or monolayer S coverage. At S coverage above one monolayer a (2 x 1) super structure was formed on top of the Fe(110)(1 x 1)-S structure. When increasing the coverage further, S grow in a zigzag formation from step edges across the terraces. These zigzag rows grow in the [1 (1) over bar1] and [001] directions and form a quasi-ordered parallelogram structure.
31.	Weissenrieder, Jonas, et al. (författare) Oxygen structures on Fe(110) 2003 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 527:03-jan, s. 163-172 Tidskriftsartikel (refereegranskat)abstract The adsorption of oxygen on a Fe(110) single crystal has been studied by means of high resolution photoelectron spectroscopy (HRPES) and scanning tunneling microscopy (STM). Core level spectra were analyzed in detail on both clean and adsorbate covered surfaces. A shoulder on the high binding energy side of the Fe 2p core level indicates a structure comprising multiple components interpreted as an exchange split of the final state due to interaction between the 2p and 3d electrons. After adsorption of oxygen, (2 x 5), (2 x 2) and (3 x 1) reconstructions were observed with atomically resolved STM. The iron surface was further exposed to gradually higher doses of oxygen. Deconvolution of the O 1s HRPES spectra revealed two components separated approximately by 0.4 eV. The component at lower binding energy dominates at low coverage, while the high binding energy component increases in intensity with increasing O coverage. The formation of oxides was observed in the Fe 2p spectrum in the region between 708 and 710 eV. Further, well ordered iron oxides were grown by exposure to oxygen at 250 degreesC. The O 1s core level contained a single component with a binding energy similar to that of the high energy component in the just discussed O 1s spectrum. Low energy electron diffraction and STM images of this structure showed a large moire pattern with a 22.1 Angstrom x 30.9 Angstrom unit cell.
32.	Wirtz, L., et al. (författare) Curve-Crossing Analysis for Potential Sputtering of Insulators 2000 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 451:1-3, s. 197-202 Tidskriftsartikel (refereegranskat)abstract We develop a theoretical model for the recently observed threshold for potential sputtering of LiF by slow singly and doubly charged ions. The threshold coincides with the potential energy to create a cold hole in the valence band of LiF by resonant neutralization. We calculate the level shift of the incident ion and the deformation of the valence band under the influence of the projectile. Resonant neutralization becomes possible for ions with recombination energies larger than 10 eV in agreement with the experimental findings.
33.	Zhang, Hanmin, et al. (författare) Origin of 3 × 3 diffraction on the Sn1-xSix/Si(1 1 1) v3 × v3 surface 2003 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 531:1, s. 21-28 Tidskriftsartikel (refereegranskat)abstract An evolution of an apparent 3 × 3 low-energy electron diffraction (LEED) pattern has been observed for the Sn1-xSix/Si(1 1 1) v3 × v3 surface alloy. The origin of this additional diffraction has been investigated in detail by scanning tunneling microscopy (STM). The 3 × 3 diffraction, which appears after annealing, is associated with the arrangement of the Sn and substitutional Si atoms in the surface layer, forming many local structures such as honeycombs, hexagons, and atomic lines. As revealed by Fourier-transforms of the STM-images, these local structures are the origins of the 3 × 3 diffraction and a weak 23×3 streaky background superposed on the 3 × 3 LEED pattern. © 2003 Elsevier Science B.V. All rights reserved.
34.	Zhang, Hanmin, 1966-, et al. (författare) Origin of 3x3 diffraction on the Sn1-xSix /Si(111)sqrt3xsqrt3 surface 2003 Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 531:1, s. 21-28 Tidskriftsartikel (refereegranskat)
35.	Zhang, Hanmin, et al. (författare) Surface electronic structures of Au-induced reconstructions on the Ag/Ge(1 1 1) v3 × v3 surface 2003 Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 532-535, s. 934-939 Tidskriftsartikel (refereegranskat)abstract A small amount of Au atoms deposited at room temperature transforms the Ag/Ge(1 1 1)v3 × v3 surface into a v 39 × v39 surface. The presence of the Au atoms leads to downward shifts and modifications of the surface state bands compared to the initial v3 × v3 surface. Further deposition of Au on the v39 × v39 surface changes it into a 6 × 6 periodicity. At the same time the surface electronic structure changes from a metallic to a semiconducting phase with a gap of around 0.2 eV with respect to the Fermi-level. Finally, the 6 × 6 phase transforms into a new 2v3 × 2v3 phase when more Au is added, and the surface switches back to a metallic state. © 2003 Elsevier Science B.V. All rights reserved.
36.	Zhukovskii, Y. F., et al. (författare) The adhesion properties of the Ag/alpha-Al2O3(0001) interface : an ab initio study 2002 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 513:2, s. 343-358 Tidskriftsartikel (refereegranskat)abstract Ab initio computer simulations of the atomic and electronic structure of the Ag/alpha-Al2O3(0 0 0 1) (corundum) interface have been performed for a periodic two-dimensional slab model using the Hartree-Fock method and a posteriori electron correlation corrections. We have considered both Al- and O-terminated corundum substrate surfaces. The dependence of the adhesion energy on the interfacial distance has been analyzed for the two most favorable Ag adsorption positions over corundum and for two different metal coverages (a 1/3 monolayer (NIL) of the Ag(l 1 1) crystallographic plane and a full Ag(I 1 1) monolayer). The two different terminations (Al- and O-) give rise to qualitatively different results. The former case corresponds to the most stable termination of the pure corundum (0 0 0 1) substrate where small adhesion energies per Ag atom (0.15-0.25 eV for I ML and 0.40-0.55 eV for 1/3 NIL) are accompanied by minor interfacial charge transfer, indicating physisorption, which may be explained by a weak atomic polarization. In contrast, for O-terminated corundum, substantial adhesion energies (3-5 eV per Ag atom at I ML coverage and 6-11 eV for 1/3 ML) combined with noticeable charge transfer from silver atoms towards the substrate (0.5e to 0.9e) are clear indications of a strong interfacial ion bonding. For both terminations, the observed difference in Ag adhesion energies for 1/3 NIL and I NIL coverages arises from a transition from directed Ag-O bonding towards a more delocalized electron density distribution in the complete monolayer. The results of our calculations are compared with available experimental studies and theoretical simulations for various Me/Al2O3 interfaces.
37.	Andrae, Johan C. G., et al. (författare) OH desorption energies for a palladium catalyst characterised by kinetic modelling and laser-induced fluorescence 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 563:03-jan, s. 145-158 Tidskriftsartikel (refereegranskat)abstract A kinetic model for the H-2/O-2 reaction on a polycrystalline palladium catalyst has been constructed using CHEMKIN in order to understand the coverage-dependent OH desorption energy. Each adsorbed oxygen atom was modelled to cover four I'd surface sites. The yield of OH and the water production were measured with laser-induced fluorescence (LIF) and microcalorimetry respectively as a function of the relative hydrogen concentration, alpha(H2). The temperature of the catalyst was 1300 K, the total pressure was 13 Pa and the flow was set to 100 SCCM. In fitting the model to the experimental data, the OH desorption energy E-OH(d) was found to have a first-order coverage dependence according to: E-OH(d)(theta) = E-OH(d)(0) - Btheta, where B is a constant set to 92 kJ/mol. The desorption energy at zero coverage E-OH(d)(0) was determined to be 226 kJ/mol. The model could also qualitatively and quantitatively reproduce the apparent desorption energy as a function of alpha(H2); therefore it is believed that the coverage could be predicted by the model. The values for E-OH(d)(theta) were calculated as a function of alpha(H2). From the results of a sensitivity analysis and rate of production calculations' there are strong reasons to believe that the main water-forming reaction on Pd at 1300 K is the hydrogen addition reaction, H + OH reversible arrow H2O. Enthalpy diagrams for the water-forming reactions are also presented.
38.	Delin, Anna, et al. (författare) Emerging magnetism in platinum nanowires 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 566, s. 262-267 Tidskriftsartikel (refereegranskat)abstract We have investigated infinitely long, monostrand Pt nanowires theoretically, and found that they exhibit Hund's rule magnetism. We find a spin moment of 0.6 mu(B) per atom, at the equilibrium bond length. Its magnetic moment increases with stretching. The origin of the wire magnetism is analyzed and its effect on the conductance through the wire is discussed.
39.	Gotte, Anders, et al. (författare) Molecular dynamics simulations of reduced CeO2 : bulk and surfaces 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 552:03-jan, s. 273-280 Tidskriftsartikel (refereegranskat)abstract Results from molecular dynamics simulations for bulk and the (0 1 1) surface of reduced and unreduced CeO2 at 300 K are reported. The presence of vacancies in reduced ceria is found to give rise to many different local structural arrangements, and to a significant broadening of the peaks in the pair-distribution function. This broadening is mainly due to the appearance of these new structural arrangements, and it is not due to the increased ionic motions in the reduced systems.
40.	Göthelid, Mats, et al. (författare) An ordered layer of molecular iodine on Ge(100) 2x1 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 556:03-feb, s. 203-212 Tidskriftsartikel (refereegranskat)abstract Adsorption of iodine on the Ge(1 0 0) (2 x 1) surface has been investigated by core level and valence band photoelectron spectroscopy and scanning tunnelling microscopy. Iodine binds to dimer atom dangling bonds without disrupting the dimers at all coverages. At saturation a c(2 x 2) ordered layer of molecular iodine develops on top of a (2 x 2) ordered structure of atomic iodine binding to asymmetric Ge-dimers. Annealing destroys the molecular character and etches the surface by Ge dimer bond breaking and attachment of additional iodine to these Ge atoms to form GeI2, which desorbs from the surface.
41.	Habermehl-Cwirzen, Karin, et al. (författare) Sulfur poisoning of the CO adsorption on Co(0001) 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 573:2, s. 183-190 Tidskriftsartikel (refereegranskat)abstract CO adsorption on a sulfur covered cobalt surface at 185 K has been studied using XPS, TDS, LEED, and WF measurements. As in the case of CO adsorption on the clean Co(0001) surface, CO adsorbs and desorbs molecularly and no dissociation was observed. The saturation coverage of CO decreases linearly from 0.54 ML to 0.27 ML when the S pre-coverage increases to 0.25 ML. The WF increased during CO adsorption, but did not reach the value obtained for CO adsorption on the clean surface. The smaller work function change is explained by the reduced adsorption of CO on the sulfur-precovered surface. A reduction in the activation energy of desorption for CO from 113 kJ/mol to 88 kJ/mol was observed indicating weaker bonding of the CO molecules to the surface. The behavior of the CO/S/Co(0001) system was explained by a combination of steric and electronic effects.
42.	Hugosson, Håkan Wilhelm, et al. (författare) Surface energies and work functions of the transition metal carbides 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 557:03-jan, s. 243-254 Tidskriftsartikel (refereegranskat)abstract We have performed an ab initio study of the surface energies, surface electronic structures and work functions for the (10 0) surface of the, existent and hypothetical, cubic 3d (Sc-Cu), 4d (Zr-Ag) and 5d (La-Au) transition metal carbides. The calculated surface energies have been compared to predictions using a so-called bond-cutting model and a model based on the so-called bonding energies. The absolute values and rough trends of the surface energies are fairly well predicted within the simple bond-cutting model, as compared to fully self-consistent calculations, while both trends and absolute values are well reproduced within the bonding energy model. The electronic structure (densities of states) of the transition metal carbides at the surface and in the bulk have been calculated. The trends are discussed in relation to the behavior of the surface energy and the work function across the series.
43.	Johansson, Leif, 1945-, et al. (författare) A comparative photoemission study of polar and nonpolar SiC surfaces oxidized in N2O 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 552:1-3, s. 251-259 Tidskriftsartikel (refereegranskat)abstract Photoemission studies of oxidized SiC samples grown ex situ in N 2O, at a temperature of 900 °C, on the (0001), (0001̄), (112̄0) and (101̄0) surfaces are reported. Angle resolved data from the Si 1s and Si 2p core levels and the Si KL2,3L2,3 Auger transitions are analyzed and compared to data from a sample grown in O2 on the (0001) surface. The results show oxide growth and no oxy-nitride formation. The growth rate is found to be smallest for the Si-terminated (0001) surface and highest for the nonpolar (101̄0) surface. The presence of two oxidation states, Si+4 and a suboxide, are required to explain and model recorded Si 1s, Si 2p and Si KLL spectra. The SiO2 shift is found to be smaller on the (0001) surface than on the other three surfaces, which is attributed to an oxide thickness dependence of the shift. A layer attenuation model describes satisfactorily the intensity variations observed in the core level components versus electron emission angle when assuming the suboxide at the interface. Estimates made of the thickness of the oxide layers show that the oxidation rate for the (0001) surfaces is about half of that for the (101̄0) surface and that the oxidation rate for the (112̄0) and (0001̄) surfaces are similar but somewhat smaller than for the (101̄0) surface. The amount of suboxide is found to be smaller on the nonpolar than on the polar surfaces. © 2004 Elsevier B.V. All rights reserved.
44.	Neidhardt, Jörg, 1976-, et al. (författare) Arrhenius-type temperature dependence of the chemical desorption processes active during deposition of fullerene-like carbon nitride thin films 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 569:1-3 Tidskriftsartikel (refereegranskat)abstract The chemical desorption of carbon and nitrogen-containing species from the growth surface was investigated for the deposition of fullerene-like carbon nitride (FL CNx) thin solid films by reactive magnetron sputtering of a carbon target in a N2-containing atmosphere. The desorption of mainly C2N2 was suppressed by decreasing the substrate temperature for various N2 fractions in the discharge stepwise from 873 K down to cryogenic temperatures of 153 K. This approach enabled us to quantify the film-forming flux by determining the carbon and nitrogen incorporation rates by elastic recoil detection. The incorporation of both, carbon and nitrogen, was found to increase substantially at lower substrate temperatures, whereas this effect is most pronounced for the higher N 2 fractions. In turn, a modified Arrhenius-type rate equation was applied to extrapolate the total flux of the elements as well as their respective activation energies of desorption for the series at higher N 2 fractions. The reasonable fit indicates that the desorption process is mainly determined by the surface diffusion rate of adsorbed C xNy species as well as their structure and total number. The extrapolated fluxes of carbon and nitrogen atoms arriving as preformed species at the growth surface scaled strongly with the availability of N 2 in the discharge, while the obtained activation energies of 0.05-0.17 eV point towards a saturation of the process at elevated temperatures. Furthermore, the constant C/N ratio found in the film-forming flux leads to the notion that most of the nitrogen incorporated originates from preformed species instead of N atoms or ions. The FL structure evolution has to be seen as a sensitive interplay between the type and magnitude of preformed C xNy species in the deposition flux and the selectiveness of the preferential etching by means of the chemical desorption. © 2004 Elsevier B.V. All rights reserved.
45.	Nokbin, S., et al. (författare) DFT plane-wave calculations of the Rh/MgO(001) interface 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 566, s. 977-982 Tidskriftsartikel (refereegranskat)abstract The Rh/MgO(001) system has been studied by periodic plane-wave density functional calculations using the VASP code and PAW potentials. Four different adsorption sites (which were reduced to three after optimization) and three different surface coverages were investigated. For the most stable site, above O, the adhesion energy was found to decrease as a function of coverage (from 2.0 to 1.1 eV as the coverage increases from 1/8 to I ML), while the adsorption energy was found to increase with surface coverage. Electron density difference plots were calculated to display some of the electron rearrangement responsible for the Rh-oxide adhesion energy, and the features of the Mg and O adsorption sites were compared.
46.	Pussi, Katariina, et al. (författare) The (√7 × √7)R19.1°-C6H6 adsorption structure on Co{0001} : A combined tensor LEED and DFT study 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 572:1, s. 1-10 Tidskriftsartikel (refereegranskat)abstract The geometric structure of a Co{0001}-(√7 × √7)R19.1°-C6H6 surface formed by adsorption of benzene to the saturation coverage at 170 K has been determined by low energy electron diffraction (LEED). The favored model consists of a flat laying, nearly undisturbed benzene molecule, with the hydrogen-carbon bonds bent away from the substrate by 0.3 ± 0.2 Å. The carbon ring lies at a hcp-site with the two parallel C-C bonds aligned with [1̄100] direction. Buckling between the inequivalent carbon atoms in the molecular ring is within the experimental uncertainty (0.01 ± 0.11 Å). The experimental results are supported by density functional calculations
47.	Rad, Goshtasbi, et al. (författare) Cerium-induced reconstructions on the Si(111) surface 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 558:03-jan, s. 49-56 Tidskriftsartikel (refereegranskat)abstract Scanning tunnelling microscopy has been used to investigate cerium-induced reconstructions on Si(1 1 1). Room temperature deposition of submonolayers of Ce is reactive and produces an intricate two layer silicide structure: a root7 x root7 phase on top of a 2root3 x 2root3 reconstruction, co-existing with the bare Si(1 1 1)-7x7 surface. Annealing the submonolayer-covered surface at 600degreesC generates a one-dimensional (5x2) structure comprising both Cc and Si adatoms. This structure coexists with the bare 7x7 and a 2x3 structure with cerium adatoms in alternating H-3 and T-4 positions.
48.	Rad, M. G., et al. (författare) Influence of charged impurities on the surface phases of Sn/Ge(111) 2001 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 477:03-feb, s. 227-234 Tidskriftsartikel (refereegranskat)abstract The root3 alpha and 3 x 3 reconstructions on the Ge(111)-Sn surface have been perturbed by small amounts of iodine and potassium to test the spectral response in the course of a synchrotron radiation photoemission study. We demonstrate the inadequacy of the static model of the root3 alpha phase at room temperature and of the surface charge density wave model of the 3 x 3 phase at low temperature. Instead, the influence of the charged impurities is consistently explained when considering that dynamical fluctuations in the tin adatom positions are frozen in upon passing the phase transition temperature.
49.	Vincent, Jonathan, et al. (författare) Dissociative chemisorption of H 2 on Pt(111) : isotope effect and effects of the rotational distribution and energy dispersion 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 573:3, s. 433-445 Tidskriftsartikel (refereegranskat)abstract Six-dimensional quantum dynamics calculations on dissociative scattering of H2 and D2 from Pt(111) are performed.The six-dimensional potential energy surface used was generated using density functional theory employingthe generalized gradient approximation. The isotope effect, the effect of widening the rotational distribution on the dissociationprobability and the effect of the energy dispersion are investigated, as they are possible reasons for a discrepancybetween previous theoretical work and molecular beam experiments. It was found that these effects cannot explainthe differences between the theoretical and experimental results.
50.	Widstrand, Susanna, et al. (författare) Preparation of stoichiometric GaN(0001)1x1 studied with spectromicroscopy 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 572:2-3, s. 409-417 Tidskriftsartikel (refereegranskat)

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