| 1. |
- Babonas, G. J., et al.
(författare)
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Optical properties of Fe-doped silica films on Si
- 2006
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 252:15, s. 5391-5394
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Tidskriftsartikel (refereegranskat)abstract
- Optical properties of Fe-doped silica films on Si were investigated by ellipsometric technique in the region 1-5 eV. Samples were produced by sol-gel method. Precursors were prepared by mixing tetraethoxysilane (TEOS) solution in ethanol and water with aqueous solution of Fe-chloride or Fe-acetate. The coating solution was deposited on Si substrates by spin on technique. The size of Fe-containing nanometric-sized particles depended on technology and varied from 20 to 100 nm. Optical response of complex hybrid samples SiO2:Fe/Si was interpreted in a multi-layer model. In the inverse problem, the Maxwell equations were solved by transfer matrix technique. Dielectric function of Fe-doped silica layers was calculated in the model of effective media. Analysis of optical data has shown that various Fe-oxides formed. Experimental data for films obtained from precursors with Fe-acetate and annealed in hydrogen were well described by the model calculations taking into account a small contribution 1-5% of metal Fe imbedded in silica. The Fe/Fe-O contribution to optical response increased for samples grown from FeCl3-precursor. Ellipsometric data for Fe-doped silica films on Si were interpreted taking into account the structural AFM studies as well as the results of magnetic measurements.
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| 2. |
- Davila, M. E., et al.
(författare)
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Surface phase transitions at metal-semiconductor interfaces : a revisit is needed
- 2004
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 234:04-jan, s. 274-285
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we review some of the most recent progress and understanding in the low temperature surface phase transitions at prototypical metal-semiconductor interfaces. We essentially focus on quantitative surface structural information obtained by using a significant variety of specialised techniques for the individual phases of a model system, namely, tin on Ge(1 1 1) substrates. The strengths and limitations of the structural results obtained by using scanning tunnelling microscopy, photoelectron diffraction and surface X-ray diffraction are discussed in relation to their support with respect to possible mechanisms recently invoked in the literature as being at the origin of the phase transition. These investigations show that a large progress has been made in this field, taking into account the very valuable experimental and theoretical contributions provided by different groups. There remain, however, essential unresolved problems, which will be analysed in the light of the limitations of these structural methods and the difficulty presented by the complex adsorbate systems studied.
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| 3. |
- Gothelid, M, et al.
(författare)
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Etching and a disordered overlayer on the Ge(100)-S surface
- 1997
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 115:1, s. 87-95
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Tidskriftsartikel (refereegranskat)abstract
- High resolution core level photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM) have been used to study the adsorption and desorption of S on and off the Ge(100) surface. The previously proposed bridge adsorption site of S is consistent with our results at low coverage. At saturation the substrate contains several GeSx species, with x = 0.5 to 4. Both photoemission and STM reveals a non-ideal surface, with a saturation coverage above one monolayer. Furthermore, S is found to etch the substrate. The reaction products forms a disordered overlayer on top of the interface. This overlayer is transparent in the filled state STM images.
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| 4. |
- Gothelid, M, et al.
(författare)
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Ge/(111)3x1:K/Sn; On the influence of tin substitution in a metal induced 3x1 reconstruction
- 1996
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 104, s. 113-117
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Tidskriftsartikel (refereegranskat)abstract
- Go-adsorption of tin and potassium is found to induce a 3x1 reconstruction on the Ge(lll) surface. A very small amount of tin influences the Ge 3d core level spectra substantially compared to the Ge(111)3x1:K reconstruction. This is interpreted as resulting from a relaxation of the strain in the rows Ge atoms running along the surface, as proposed for this structure.
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| 5. |
- He, Z Q, et al.
(författare)
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Band structure evolution in InAs overlayers on GaAs(110)
- 1996
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 104, s. 608-614
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Tidskriftsartikel (refereegranskat)abstract
- An angle-resolved photoemission study of MBE grown InAs/GaAs(110) hetero-structures was carried out to investigate the establishment of valence bands as a function of overlayer thickness. The valence band spectra were found to change gradually up to thicknesses well above 10 nm. The data are interpreted in terms of excitations within the overlayer from a combination of substrate and overlayer initial states, the former tailing into the overlayer.
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| 6. |
- Hirschauer, B, et al.
(författare)
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CeO2 on Si(111) 7 X 7 and Si(111)-H 1 X 1, an interface study by high-resolution photoelectron spectroscopy
- 1999
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 148:3-4, s. 164-170
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Tidskriftsartikel (refereegranskat)abstract
- The formation of the CeO2-Si(111) interface was studied by high-resolution photoelectron spectroscopy. It is shown that CeO2 and Si(111) forms a highly reactive: interface with a strong interdiffusion of Si into the CeO2. A passive silicon surface formed by saturating the Si dangling bonds with hydrogen is considerably less reactive. Defects on the surface, however, act as nucleations centres for reactions of a Si:Ce:O matrix. Oxygen leaves the surface at about 800 degrees C and at 1000 degrees C a surface reconstruction of Si(111)-Ce 2 X 2/root 3 X root 3 is formed. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 7. |
- Janin, E, et al.
(författare)
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Hydrogen adsorption on the Pt(111)(root 3x root 5)R30 degrees-Sn surface alloy studied by high resolution core level photoelectron spectroscopy
- 1996
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 99:4, s. 371-378
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Tidskriftsartikel (refereegranskat)abstract
- Investigation of the clean and atomic hydrogen covered Pt(111)(root 3 x root 3)R30 degrees-Sn surface alloy has been carried out using high resolution core level photoelectron spectroscopy, The Pt 4(7/2) spectrum recorded from the clean surface alloy shows a single surface peak shifted - 0.25 eV relative to the bulk. Its interpretation by means of a thermodynamical model using Born-Haber cycles confirms the surface alloy model. Adsorption of H does not change the line shape of the Sn 4d core level while a new surface component shifted by 0.59 eV compared to the bulk peak appears in the Pt 4(7/2) spectrum. These results are discussed in the light of the thermodynamical calculations, H atoms are believed to bind only to Pt atoms, and their adsorption site seems to be influenced by the tin present in the surface layer.
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| 8. |
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| 9. |
- Karpus, V., et al.
(författare)
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Mg 2p shallow core-level and local atomic structure of i-ZnMgRE quasicrystals
- 2006
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 252:15, s. 5411-5414
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed analysis of the Mg 2p shallow core-levels measured on icosahedral single-grain ZnMgY, ZnMgHo, and ZnMgEr quasicrystals during a photoelectron microscopy study. The synchrotron radiation photoemission measurements were performed on in situ cleaved samples at a pressure of 10(-10) mbar and at low temperature, typically 90-150 K. The Mg 2p photoemission lines are essentially broadened as compared to those of the Mg 2p spin-orbit doublet recorded on the Zn2Mg crystalline Laves phase. The broadening is associated to the coordination shifts of the Mg 2p level due to the inequivalent magnesium sites in the quasicrystalline lattice. The coordination shifts are calculated on the basis of i-ZnMg(Ho, Y) atomic structure data, recently determined from the pair distribution function analysis. The coordination shifts obtained are up to 0.2 eV. The Mg 2p experimental spectral intensity is nicely reproduced by a superposition of coordination-shifted Mg 2p spin-orbit doublets.
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| 10. |
- Le Lay, G., et al.
(författare)
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Nature of the root 3 alpha to 3 x 3 reversible phase transition at low temperature in Sn/Ge (111)
- 2001
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 175, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- Metal-induced superstructures on semiconductors at sub-monolayer coverages have been mostly studied at, or above, room temperature. Yet, recently, several reversible phase transitions, like, e.g. the root3 x root3 alpha to 3 x 3 transition in the Pb, Sn/Ge (111) prototypical systems, have been discovered below RT. The origin of these new reconstructions is very intriguing and is a matter of strong debate. Some groups privilege electronic instabilities leading to charge ordered states at low temperature (LT), while other favor dynamical effects and the formation a kind of bond density waves (BDW's) at LT. Besides these intrinsic behaviors, the role played by inevitable defects has also been emphasized by several authors. Focussing especially on the Sn/Ge (111) system, we present a detailed analysis of the spectroscopic signatures of each phase in photoemission measurements. We show that static models are impossible to reconcile with these measurements.
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