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Numrering	Referens	Omslagsbild	Hitta
1.	Nyholm, R., et al. (författare) EPITAXIAL SILICIDE FORMATION IN THE MG/SI(111) SYSTEM 1993 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 289:3, s. 290-296 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.
2.	Nyholm, R., et al. (författare) FORMATION OF SM SILICIDES ON SI(111) - COMPOSITION AND EPITAXY 1993 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 293:3, s. 254-259 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.
3.	ANDERSSON, CBM, et al. (författare) SPUTTERED AND ANNEALED INAS(111)OVER-BAR - AN UNRECONSTRUCTED SURFACE 1994 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 307, s. 885-889 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.
4.	CHAKARIAN, V, et al. (författare) THE ADSORPTION OF I2 ON SI(111)-7X7 STUDIED BY SOFT-X-RAY PHOTOEMISSION 1993 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 296:3, s. 383-392 Tidskriftsartikel (refereegranskat)abstract The adsorption Of I2 on Si(111)-7 x 7 at room temperature is studied with soft X-ray photoelectron spectroscopy. I2 adsorbs dissociatively, forming a mixture of SiI, SiI2 and SiI3 moieties, of which SiI dominates. The Fermi level is pinned near mid-gap, moving slightly towards the conduction band as the I coverage increases. The surface work function increases monotonically with I coverage. The I 4d core-level displays a single chemical state, which decreases in binding energy with increasing coverage. Analysis of the Si 2p core-level spectra shows that the adsorption proceeds first by attachment of I to the dangling bonds of the 7 x 7 unit cell and that, at saturation, 1.57 +/- 0.05 ML of I atoms are adsorbed in 1.10 +/- 0.02 ML of SiI(x) groups. These results indicate that substrate Si-Si bonds are broken by reaction with I2. The total I coverage is limited, however, by the availability Of surface dangling bonds that are required to initiate the dissociation Of I2 molecules.
5.	CHAKAROV, DV, et al. (författare) PHOTOSTIMULATED DESORPTION OF METAL ADATOMS - POTASSIUM ON GRAPHITE 1994 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 311:3, s. L724-L730 Tidskriftsartikel (refereegranskat)abstract Photodesorption is observed of single K atoms from a graphite surface covered with less than 1 monolayer of potassium. The desorption cross section has a threshold at homegaBAR almost-equal-to 3 eV and a maximum at homega(max)BAR almost-equal-to 4.9 eV. Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photoactive. The proposed mechanism includes attachment of hot electrons, photoexcited in the bulk, to the K4s adsorbate resonance of energy E(res). The band structure of graphite causes a narrow energy distribution of hot electrons, which yields homega(max)BAR almost-equal-to 2E(res).
6.	Eriksson, Mats, 1963-, et al. (författare) Spillover of hydrogen, oxygen and carbon monoxide in oxidation reactions on SiO2 supported Pd 1994 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 311:1-2, s. 139-152 Tidskriftsartikel (refereegranskat)abstract Oxidation of H2 and CO on large, oxygen preexposed Pd islands supported on SiO2, has been investigated in the temperature range 323 ⩽, T ⩽ 523 K. The results have been compared with the corresponding reactions on a polycrystalline Pd film. A maximum reactive sticking coefficient of 0.9 for H2 and an initial sticking coefficient for O2 of 0.8 on both structures is concluded. The maximum reactive sticking coefficient for CO is 0.85 on the film and apparently larger than unity on the island structure. The results obtained from the island structure can be rationalized if O2 and H2 dissociate on the Pd islands and have the possibility to spillover onto the oxide, while CO adsorbs and reacts both on the Pd islands and on the oxide. Spillover of oxygen occurs in a precursor state and is irreversible with an apparent activation energy of 0.1 eV for the forward reaction.
7.	GOTHELID, M, et al. (författare) SN-INDUCED SURFACE RECONSTRUCTIONS ON THE GE(111) SURFACE STUDIED WITH SCANNING TUNNELING MICROSCOPY 1992 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 271:3, s. L357-L361 Tidskriftsartikel (refereegranskat)abstract Scanning tunneling microscopy (STM) has been used to study different Sn induced reconstructions on the Ge(111) surface; namely the (7 x 7), (5 x 5) and (square-root 3 x square-root 3)R30-degrees structures. The first two have been confirmed to be of the dimer adatom stacking fault (DAS) type with adatoms mainly being Sn. The (square-root 3 x square-root 3)R30-degrees superstructure was found at different Sn depositions. At 0.4 monolayer (ML) Sn coverage a homogeneous Sn adatom layer is adsorbed on the (1 x 1) surface in threefold sites directly over second-layer atoms (T4), while at low coverage, 0.1 ML, the top layer is a mixture of Sn and Ge atoms. We also propose the chemical identities of the different atoms seen in the STM images as related to their apparent height.
8.	HAKANSSON, MC, et al. (författare) DIMER FORMATION AND ELECTRONIC-STRUCTURE ON THE GE(100)(2X1)-SB SURFACE 1992 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 278:1-2, s. L131-L134 Tidskriftsartikel (refereegranskat)abstract Deposition of antimony on Ge(100)2 X 1 results in a well-ordered, highly passivated surface. From a comparison between core-level data and angle-resolved photoemission data, we conclude that the observed 2 x 1 reconstruction is caused by the formation of symmetric Sb-Sb dimers on the Ge surface.
9.	Hoffmann, F.M., et al. (författare) The activation of CO2 by potassium-promoted Ru(001) I. FT-IRAS and TDMS study of oxalate and carbonate intermediates 1994 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 316:3, s. 277-293 Tidskriftsartikel (refereegranskat)abstract The interaction of CO2 with the clean and alkali promoted Ru(001) surface has been studied with time-evolved Fourier transform-infrared reflection absorption spectroscopy (FT-IRAS) and thermal desorption mass spectrometry (TDMS). CO2 adsorbs on the clean Ru(001) surface at 85 K in a physisorbed CO2 monolayer, which desorbs undissociated at 100 K. The interaction of CO2 with a √3 × √3-R30° monolayer of potassium on Ru(001) results in the facile formation of oxalate at 85 K. Oxalate decomposes to carbonate after heating above 150 K, i.e. C2O4 → CO3 + CO. Vibrational spectra suggest, in agreement with theoretical calculations, an ionic carbonate species with D3h symmetry and the molecular plane oriented perpendicular to the surface, although alternate coordinations cannot be completely ruled out. Decomposition of the carbonate starts at 700 K and results in the simultaneous desorption of K and CO2 as major decompositions products, suggesting a reaction pathway of CO3 → CO2 + O and a K:CO3 stoichiometry of ≈1:1. The interaction of CO2 with a multilayer of potassium adsorbed on Ru(001), exhibits similar intermediates as observed for the monolayer, i.e. oxalate and carbonate. However, the overall reaction behavior is more complex and controlled by the penetration of CO2 into the potassium layer, which limits the reaction to only a few (4-5) of the topmost potassium layers. Reaction at 85 K reveals the formation of oxalate, CO2-2 and possibly CO-2 species. Annealing of the multilayer to 425 K results in the formation of carbonate, and the desorption of unreacted potassium. Vibrational spectra characterize an essentially ionic carbonate species with a preferential orientation of the molecular plane perpendicular to the surface, although the vibrational linewidths suggest imperfect ordering of the layer. Further annealing to 550 K results in a well-ordered "bilayer", containing two carbonate species with the molecular plane perpendicular (C2v, first layer) and parallel (C3v, second layer) to the surface, respectively. Decomposition of this layer at 700 K leaves a carbonate monolayer which subsequently decomposes at 750 K. The overall decomposition behavior of the multilayer is complex and is sensitive to the preparation and thickness of the potassium multilayer.
10.	JOHANSSON, LI, et al. (författare) CORE LEVEL PHOTOEMISSION-STUDY OF CR3SI(100) 1991 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 251, s. 101-107 Tidskriftsartikel (refereegranskat)abstract High resolution photoemission studies of the core levels in Cr3Si have been carried out using synchrotron radiation. Investigations were performed both on the clean surface, cleaned in situ by sputter and annealing cycles, and after oxygen exposures. A surface shifted Si 2p component was observed on the annealed surface but no surface shifted component could be identified in the Cr 3p spectrum. The surface shift was extracted using a curve fitting procedure and found to be -0.30(5) eV. The shift expected due to the loss of coordination at the surface is found to be negative but of about half the size of the observed shift. Upon oxygen adsorption at room temperature a chemically shifted Si 2p component appeared already after an exposure of < 1 L, indicating rapid silicon oxidation, while a chemically shifted Cr 3p component could be resolved only after exposures of about 10 L. These findings are presented and discussed.
11.	LELAY, G, et al. (författare) STM AND SYNCHROTRON-RADIATION STUDIES OF PROTOTYPICAL METAL-SEMICONDUCTOR SYSTEMS 1994 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 307, s. 280-294 Tidskriftsartikel (refereegranskat)abstract Since the origin of surface science noble metal/elemental semiconductor couples have been considered as ''prototypical'' systems. After three decades of research their structural and electronic properties remain an intriguing maze despite recent advances made, especially thanks to the development of the near-field microscopies and the ''tensive use of synchrotron radiation in surface crystallography and in high-resolution photoelectron spectroscopy. In the last few years, lead, as a replacement inert metal, has nearly gained the pole position in the display of exotic behaviour. This paper gives a flavour of this mystery story and highlights some puzzling questions.
12.	QU, H, et al. (författare) SURFACE ELECTRON-STRUCTURE OF INP(110) STUDIED WITH ANGLE-RESOLVED PHOTOELECTRON-SPECTROSCOPY 1991 Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 255:3, s. 237-244 Tidskriftsartikel (refereegranskat)abstract The surface electron structure of InP(110) has been studied by means of synchrotron radiation excited angle-resolved photoelectron spectroscopy. After identifying the bulk-related spectral structures, the surface-induced energy bands have been mapped along symmetry directions. The polarization dependence of the surface-related structures is discussed.
13.	TORNEVIK, C, et al. (författare) ADSORPTION OF SN ON SI(111)7X7 - RECONSTRUCTIONS IN THE MONOLAYER REGIME 1994 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 314:2, s. 179-187 Tidskriftsartikel (refereegranskat)abstract Different monolayer phases of Sn on Si(111)7 x 7 have been studied by means of scanning tunneling microscopy (STM), core-level photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS). The STM results show that square-root 3 x square-root 3 reconstructions are obtained for room-temperature deposition of 1/3 ML of Sn followed by sample annealing in a broad temperature range. A T4 Sn adatom square-root 3 x square-root 3 phase is formed for temperatures between 500 and 800-degrees-C, with a concentration of defects that is strongly dependent on the temperature and which is as high as 25% for the lowest temperatures. Above 825-degrees-C a second square-root 3 x square-root 3 adatom reconstruction is formed, a mosaic-like phase with a 1: 1 mixture of Si and Sn atoms in T4 positions. The results from investigations of the higher coverage 2 square-root 3 x 2 square-root 3 reconstruction by XPS and RBS support the theory that this phase is a two-layer epitaxial Sn structure with all Si(111) dangling bonds saturated. The Sn coverage for this phase was determined to be between 1 and 1.2 ML.
14.	Ågren, H., et al. (författare) On the vibrational and orientational probing of surface-adsorbates by direct and resonance photoemission 1994 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 311:3, s. 375-384 Tidskriftsartikel (refereegranskat)abstract Vibrationally resolved direct photoemission spectra of physisorbed molecules separated from the substrate by spacer layers, show remarkable splittings of vibronic progressions. The corresponding resonant photoemission spectra have recently confirmed these splittings and also revealed their strong dependence on the polarization of the exciting radiation. We apply a self-consistent mirror image model on the physisorbed nitrogen and oxygen molecules to explore the origin of these shifts and their dependence on the orientation of the adsorbate molecule with respect to the surface. The symmetry character and orientational probing of autoionization is analyzed for the resonant cases by a decomposition of the interacting matrix elements.
15.	Andersen, J. N., et al. (författare) Alkali metal adsorption on Al(111) 1993 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 289:3, s. 307-334 Tidskriftsartikel (refereegranskat)abstract The submonolayer adsorption of Na, K, Rb, and Cs on the Al(111) surface at 100 K and at room temperature is investigated by high resolution core level spectroscopy and low energy electron diffraction. It is found that the first alkali atoms on the surface adsorb at surface defects. At higher coverages, up to approximately one third of the maximum submonolayer coverage, alkali atoms adsorbed at defects coexist with a dispersed phase. At higher coverages island formation is found to occur for the majority of the systems. It is argued that all of the ordered structures formed at room temperature involve a disruption of the Al(111) surface in contrast to the situation at 100 K where the alkali atoms adsorb as adatoms.
16.	Heskett, D., et al. (författare) Alkali-alkali interactions on Al(111) : segregation and islanding in Na-Rb mixtures 1994 Ingår i: Surface Science. - 0039-6028. ; 316:3, s. 303-308 Tidskriftsartikel (refereegranskat)abstract The low temperature coadsorption of Na and Rb on an Al(111) surface is examined with a combination of LEED and core level photoemission spectroscopy. We observe LEED pattern sequences and alkali core level binding energies which are consistent with a net total alkali coverage and can be explained by Na-Rb repulsion, segregation, and islanding, though other models cannot be definitely excluded.
17.	Johansson, L. I., et al. (författare) Surface core level shift on Be( 112̄0) 1994 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 321:3 Tidskriftsartikel (refereegranskat)abstract A photoemission study of the Be(112̄0) surface carried out at a sample temperature of 100 K is reported. A surface shifted Be 1s component, having a shift of - 410 meV, is resolved on this surface. The extracted surface to bulk intensity ratio indicate that this component originates from atoms in the surface layer only. This is opposite to previous observations on both the close-packed Be(0001) surface and the Be(101̄0) surface where sub-surface shifted Be 1s levels were unambiguously identified. Among these three surfaces a surface layer atom is expected to have the lowest coordination on the (112̄0) surface but the surface layer shift is found to be smallest on this surface. Compared to findings on other metals this is unusual and reasons contributing to this behaviour are suggested and discussed.
18.	Lundgren, E., et al. (författare) Layer dependent core level binding energy shifts : Na, K, Rb and Cs on Al(111) 1993 Ingår i: Surface Science. - 0039-6028. ; 281:1-2, s. 83-90 Tidskriftsartikel (refereegranskat)abstract Layer resolved core level spectra are presented for Na, K, Rb and Cs films on Al(111). From the development of the spectra, it is possible to distinguish emission from alkali atoms at the interface, in the bulk, and at the surface of the adsorbed layers. The core level binding energy shifts are discussed in terms of adhesion and interface segregation energies. It is found experimentally that the Al induced core level binding energy shifts of the alkalis are increasing with increasing atomic number of the alkali metal. This trend is qualitatively reproduced by semi-empirical calculations.
19.	Göthelid, M., et al. (författare) Sn-induced surface reconstructions on the Ge(111) surface studied with scanning tunneling microscopy 1992 Ingår i: Surface Science. - 0039-6028. ; 271:3, s. L357-L361 Tidskriftsartikel (refereegranskat)abstract Scanning tunneling microscopy (STM) has been used to study different Sn induced reconstructions on the Ge(111) surface; namely the (7 Ã— 7), (5 Ã— 5) and ( 3 Ã— 3) R30Â° structures. The first two have been confirmed to be of the dimer adatom stacking faults (DAS) type with adatoms mainly being Sn. The ( 3 Ã— 3)R30Â° superstructure was found at different Sn depositions. At 0.4 monolayer (ML) Sn coverage a homogeneous Sn adatom layer is adsorbed on the(1 Ã— 1) surface in threefold sites directly over second-layer atoms (T4), while at low coverage, 0.1 ML, the top layer is a mixture of Sn and Ge atoms. We also propose the chemical identities of the different atoms seen in the STM images as related to their apparent height. Â© 1992.
20.	Le Lay, G., et al. (författare) STM and synchrotron radiation studies of "prototypical" metal{plus 45 degree rule}semiconductor systems 1994 Ingår i: Surface Science. - 0039-6028. ; 307-309:PART A, s. 280-294 Tidskriftsartikel (refereegranskat)abstract Since the origin of surface science noble metal{plus 45 degree rule}elemental semiconductor couples have been considered as "prototypical" systems. After three decades of research their structural and electronic properties remain an intriguing maze despite recent advances made, especially thanks to the development of the near-field microscopies and the extensive use of synchrotron radiation in surface crystallography and in high-resolution photoelectron spectroscopy. In the last few years, lead, as a replacement inert metal, has nearly gained the pole position in the display of exotic behaviour. This paper gives a flavour of this mystery story and highlights some puzzling questions. Â© 1994.
21.	Siegbahn, Per E.M., et al. (författare) A THEORETICAL-STUDY OF CHX CHEMISORPTION ON THE NI(100) AND NI(111) SURFACES 1990 Ingår i: Surface Science. - 0039-6028. ; 240:1-3, s. 37-49 Tidskriftsartikel (refereegranskat)abstract Cluster model calculations have been performed for CH(x), x = 0-3, chemisorbed on Ni(100) and Ni(111). The predicted chemisorption energies, at the present level of theory, based on bond-prepared clusters for Ni(100) are for carbon 150 kcal/mol, for CH 136 kcal/mol, for CH2 91 kcal/mol and for CH3 46 kcal/mol. The corresponding energies for Ni(111) are for CH 120 kcal/mol, for CH2 88 kcal/mol and for CH3 49 kcal/mol. These chemisorption energies lead to similar stabilities for all CH(x) fragments on both Ni(100) and Ni(111). Large basis sets multi-reference correlation treatments are found to be very important in particular for the multiply bonded species. The vibrational C-H stretching frequencies predicted for CH(x) on Ni(111) are for CH 3054 cm-1 (2980 cm-1), for CH2 3204 cm-1 and for CH3 2709 cm-1 (2680 cm-1), where the available experimental values are given in parenthesis. The predicted ionization spectra of adsorbed CH(x) are also in general agreement with experimental findings.
22.	Snis, Anders, et al. (författare) Abstraction of preadsorbed oxygen from CaO(100) by carbon monoxide 1994 Ingår i: Surf Sci Lett. - 0039-6028. ; 310:1-3 Tidskriftsartikel (refereegranskat)abstract The mechanism for abstraction of preadsorbed oxygen from CaO(100) by CO(g) to form CO2(g) is investigated by electronic structure calculations. The reaction mechanism is assumed to be the reverse of the one obtained for the decomposition of N2O(g) at CaO(100) [Surf. Sci 292 (1993) 317]. A 32 kcal/mol barrier for reaction is calculated. Adsorbed oxygen, Oads, to surface vibration frequencies in the range 840–930 cm−1 are calculated. These values are in qualitative agreement with experiment.
23.	Snis, Anders, et al. (författare) N2O adsorption and decomposition at a CaO (100) surface studied by means of theory 1993 Ingår i: Surf Sci. - 0039-6028. ; 292:3, s. 317-324 Tidskriftsartikel (refereegranskat)abstract The adsorption and decomposition of an N2O molecule at different sites on a CaO(s) surface are investigated by means of ab initio quantum chemistry. The calcium, Ca2+, and oxygen, Os2−, sites at a perfect (100) surface and at a corner position, Oc2−, are considered. Adsorption energies at different sites are calculated and the largest value, 6 kcal/mol, is obtained for a corner site. The barrier for dissociation is calculated to 26 and 27 kcal/mol at the Oc2− and Os2− sites, respectively. These values are some 10 kcal/mol lower than the experimental estimate, and the discrepancy is understood from methodological difficulties to describe the free N2O molecule. A mechanism for the dissociation over an O2− site is proposed, whereby the transfer of the O atom goes via a linear N-N … O … O2− transition state.
24.	Strömberg, Dan, 1959 (författare) The bonding and migration of an O atom on a CaO (100) surface. A theoretical study 1992 Ingår i: Surf Sci. - 0039-6028. ; 275:3, s. 473-481 Tidskriftsartikel (refereegranskat)abstract Ab initio quantum calculations of the dissociation energies and bond distances for the bond between an O atom situated at different sites on a CaO(100) surface have been performed, using surface clusters imbedded in an array of point charges. The point charges were evaluated by a modified Ewald technique. The calculations were carried out using the CASSCF and CCI methods. Different clusters were tested. The “peroxy” bond between the O atom and a surface O2− site was found to be the strongest, ≈ 50 kcal/mol at the CCI level compared to a triplet oxygen atom far away from the surface ( 100 kcal/mol compared to a singlet oxygen atom). The bond on top of a surface Ca2+ ion was very weak, 5 kcal/mol. The surface migration of an O atom from one O2− site to another O2− was investigated. The barrier for the migration was calculated to 66 kcal/mol.
25.	Törnevik, C., et al. (författare) Adsorption of Sn onSi(111)7 Ã— 7 : reconstructions in the monolayer regime 1994 Ingår i: Surface Science. - 0039-6028. ; 314:2, s. 179-187 Tidskriftsartikel (refereegranskat)abstract Different monolayer phases of Sn on Si(111)7 Ã— 7 have been studied by means of scanning tunneling microscopy (STM), core-level photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS). The STM results show that 3 Ã— 3 reconstructions are obtained for room-temperature deposition of 1 3 ML of Sn followed by sample annealing in a broad temperature range. A T4 Sn adatom 3 Ã—3 phase is formed for temperatures between 500 and 800Â°C, with a concentration of defects that is strongly dependent on the temperature and which is as high as 25% for the lowest temperatures. Above 825Â°C a second 3Ã—3 adatom reconstruction is formed, a mosaic-like phase with a 1:1 mixture of Si and Sn atoms in T4 positions. The results from investigations of the higher coverage 2 3 Ã— 2 3 reconstruction by XPS and RBS support the theory that this phase is a two-layer epitaxial Sn structure with all Si(111) dangling bonds saturated. The Sn coverage for this phase was determined to be between 1 and 1.2 ML. Â© 1994.

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