| 1. |
- Giovanelli, L., et al.
(författare)
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Electronic structure of self-assembled organic/inorganic semiconductor interfaces : lead phthalocyanine on InSb and InAs(100)-4X2/c(8 X2)
- 2001
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048 .- 1873-2526. ; 114, s. 375-381
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial properties of ultra thin films of lead-phthalocyanine deposited in situ onto InSb and InAs(100)-4X2/c(8X2) clean surfaces have been studied by synchrotron radiation core level and valence band photoelectron spectroscopy. The interaction between the overlayers and the substrates was determined upon analyzing the changes in the photoemission spectra between room and higher annealing temperatures, leading to ordered monolayer films. While weaker than on other substrates, a reactivity is nevertheless present: the organic macrocycle preserves its integrity up to 320 degreesC but the Pb central atom first leaves the molecules most probably to be incorporated in the substrate surface, before being desorbed at higher temperatures.
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| 2. |
- 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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| 3. |
- Papageorgiou, N., et al.
(författare)
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High resolution synchrotron radiation PES study of PbPc deposited on Pt(111)
- 2000
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 162, s. 178-183
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Tidskriftsartikel (refereegranskat)abstract
- We studied lead phthalocyanine (PbPc) films sublimated under UHV conditions on a clean Pt(111) substrate. We report results from high resolution photoelectron spectra of the Pb 5d, Ph 4f, C 1s, N 1s and Pt 4f core level using synchrotron radiation. Comparison between ultra thin films and thicker films shows that the first molecular adlayer interacts strongly with the substrate and we report evidence of Pb-Pt alloy formation on the surface. For the thick films, the C Is and N Is core level spectra show usual characteristics, however in the case of ultra thin films, we note important differences with respect to some previous results.
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| 4. |
- Rad, M. G., et al.
(författare)
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Influence of charged impurities on the surface phases of Sn/Ge(111)
- 2001
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 477:03-feb, s. 227-234
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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.
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| 5. |
- 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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| 6. |
- Giovanelli, L., et al.
(författare)
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Synchrotron radiation photoelectron spectroscopy study of Pb-Pc thin films on InSb(100)-(4x2)/c(8x2)
- 2001
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 486:02-jan, s. 55-64
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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.
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| 7. |
- Grehk, T. M., et al.
(författare)
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Li-induced phase transition from the Ge(111)3X1 : Li surface reconstruction to the Ge(111)root 3X root 3 : Li lithium germanide
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:7, s. 4963-4967
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the Li-induced phase transition from the Ge(111)3X1:Li to the Ge(111)root 3X root 3:Li reconstruction with photoemission. The Ge(111)3X1:Li reconstruction can be described as parallel rows of Ge atoms separated by single rows of Li atoms. The Ge(111)root 3X root 3:Li reconstruction, on the other hands, has to be described in terms of a Li-germanide phase extending over at least two atomic layers.
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| 8. |
- Göthelid, Mats, et al.
(författare)
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An ordered layer of molecular iodine on Ge(100) 2x1
- 2004
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 556:03-feb, s. 203-212
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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.
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| 9. |
- Papageorgiou, N., et al.
(författare)
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Lead phthalocyanine thin films on InAs(100)-(4 x 2)/c(8 x 2) studied by synchrotron radiation photoelectron spectroscopy
- 2001
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 482, s. 1199-1204
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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.
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| 10. |
- Rad, Goshtasbi, et al.
(författare)
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Cerium-induced reconstructions on the Si(111) surface
- 2004
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 558:03-jan, s. 49-56
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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.
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