SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "swepub ;pers:(Johansson Börje);conttype:(refereed);srt2:(2010-2011)"

Sökning: swepub > Johansson Börje > Refereegranskat > (2010-2011)

  • Resultat 1-10 av 61
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Laukkanen, P., et al. (författare)
  • Bismuth-stabilized c(2X6) reconstruction on a InSb(100) substrate Violation of the electron counting model
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 81:3
  • Tidskriftsartikel (refereegranskat)abstract
    • By means of scanning tunneling microscopy/spectroscopy (STM/STS), photoelectron spectroscopy, and first-principles calculations, we have studied the bismuth (Bi) adsorbate-stabilized InSb(100) substrate surface which shows a c(2X6) low-energy electron diffraction pattern [thus labeled Bi/InSb(100)c(2X6) surface] and which includes areas with metallic STS curves as well as areas with semiconducting STS curves. The first-principles phase diagram of the Bi/InSb(100) surface demonstrates the presence of the Bi-stabilized metallic c(2X6) reconstruction and semiconducting (4X3) reconstruction depending on the chemical potentials, in good agreement with STS results. The existence of the metallic c(2X6) phase, which does not obey the electron counting model, is attributed to the partial prohibition of the relaxation in the direction perpendicular to dimer rows in the competing reconstructions and the peculiar stability of the Bi-stabilized dimer rows. Based on (i) first-principles phase diagram, (ii) STS results, and (iii) comparison of the measured and calculated STM and photoemission data, we show that the measured Bi/InSb(100)c(2X6) surface includes metallic areas with the stable c(2X6) atomic structure and semiconducting areas with the stable (4X3) atomic structure.
2.
  • Laukkanen, P., et al. (författare)
  • Core-level shifts of the c(8 x 2)-reconstructed InAs(100) and InSb(100) surfaces
  • 2010
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 177:1, s. 52-57
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied In-stabilized c(8 2)-reconstructed InAs(1 0 0) and InSb(1 0 0) semiconductor surfaces, which play a key role in growing improved III-V interfaces for electronics devices, by core-level photoelectron spectroscopy and first-principles calculations. The calculated surface core-level shifts (SCLSs) for the zeta and zeta a models, which have been previously established to describe the atomic structures of the III-V(1 00)c(8 x 2) surfaces, yield hitherto not reported interpretation for the As 3d, In 4d, and Sb 4d core-level spectra of the III-V(1 00)c(8 x 2) surfaces, concerning the number and origins of SCLSs. The fitting analysis of the measured spectra with the calculated zeta and zeta a SCLS values shows that the InSb spectra are reproduced by the zeta SCLSs better than by the zeta a SCLSs. Interestingly, the zeta a fits agree better with the InAs spectra than the zeta fits do, indicating that the zeta a model describes the InAs surface better than the InSb surface. These results are in agreement with previous X-ray diffraction data. Furthermore, an introduction of the complete-screening model, which includes both the initial and final state effects, does not improve the fitting of the InSb spectra, proposing the suitability of the initial-state model for the SCLSs of the III-V(1 0 0)c(8 x 2) surfaces. The found SCLSs are discussed with the ab initio on-site charges.
  •  
3.
  • Lang, J. J. K., et al. (författare)
  • Tin-stabilized (1 x 2) and (1 x 4) reconstructions on GaAs(100) and InAs(100) studied by scanning tunneling microscopy, photoelectron spectroscopy, and ab initio calculations
  • 2011
  • Ingår i: Surface Science. - 0039-6028. ; 605:9-10, s. 883-888
  • Tidskriftsartikel (refereegranskat)abstract
    • Tin (Sn) induced (1 x 2) reconstructions on GaAs(100) and InAs(100) substrates have been studied by low energy electron diffraction (LEED), photoelectron spectroscopy, scanning tunneling microscopy/spectroscopy (STM/STS) and ab initio calculations. The comparison of measured and calculated STM images and surface core-level shifts shows that these surfaces can be well described with the energetically stable building blocks that consist of Sn-III dimers. Furthermore, a new Sn-induced (1 x 4) reconstruction was found. In this reconstruction the occupied dangling bonds are closer to each other than in the more symmetric (1 x 2) reconstruction, and it is shown that the (1 x 4) reconstruction is stabilized as the adatom size increases.
  •  
4.
  • Olovsson, Weine, et al. (författare)
  • First principle calculations of core-level binding energy and Auger kinetic energy shifts in metallic solids
  • 2010
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - Elsevier Science B.V., Amsterdam.. - 0368-2048. ; 178:Sp. Iss. SI, s. 88-99
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a brief overview of recent theoretical studies of the core-level binding energy shift (CLS) in solid metallic materials. The focus is on first principles calculations using the complete screening picture, which incorporates the initial (ground state) and final (core-ionized) state contributions of the electron photoemission process in X-ray photoelectron spectroscopy (XPS), all within density functional theory (DFT). Considering substitutionally disordered binary alloys, we demonstrate that on the one hand CLS depend on average conditions, such as volume and overall composition, while on the other hand they are sensitive to the specific local atomic environment. The possibility of employing layer resolved shifts as a tool for characterizing interface quality in fully embedded thin films is also discussed, with examples for CuNi systems. An extension of the complete screening picture to core-core-core Auger transitions is given, and new results for the influence of local environment effects on Auger kinetic energy shifts in fcc AgPd are presented.
5.
  • Kuzmin, M., et al. (författare)
  • Atomic structure of Yb/Si(100)(2X6) : Interrelation between the silicon dimer arrangement and Si 2p photoemission line shape
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 82:11, s. 113302
  • Tidskriftsartikel (refereegranskat)abstract
    • Combining photoelectron spectroscopy and density-functional theory calculations, we have studied the atomic geometry of Yb/Si(100)(2 X 6) reconstruction and the mechanisms responsible for its stabilization as well as the influence of this reconstruction on Si 2p core-level photoemission. The analysis of measured and calculated surface core-level shifts supports the recently proposed model of the Yb/Si(100)(2 X 6). It involves, in agreement with valence-band measurements, unbuckled (symmetrical) silicon dimers, leading to unusually narrowed Si 2p line shape as compared to those of related systems. The origin of the symmetrical dimers in the (2 X 6) structure is discussed in the context of previous results in literature.
  •  
6.
  • Kuzmin, M., et al. (författare)
  • Surface core-level shifts on Ge(111)c(2 x 8) : Experiment and theory
  • 2011
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 83:24, s. 245319
  • Tidskriftsartikel (refereegranskat)abstract
    • Combining high-resolution photoelectron spectroscopy and density functional theory (DFT) calculations, 3d photoemission line shape and surface core-level shifts have been reinvestigated on the Ge(111)c(2 x 8) surface. It is found that 3d spectra include, in addition to the bulk and three surface-shifted components reported in literature, a component that was not identified in earlier measurements with a lower resolution. The detailed interpretation of these spectra and their line shape is made on the basis of DFT calculations. It is shown that the lowest binding energy component is due to the rest atoms. The higher binding energy emission is caused by the adatoms and the third-layer atoms that are below the adatoms. Finally, the two other surface components originate from the first- and second-layer atoms. The screening effects in the Ge(111)c(2 x 8) are discussed.
  •  
7.
  • Punkkinen, Marko Patrick John, et al. (författare)
  • Oxidized In-containing III-V(100) surfaces : Formation of crystalline oxide films and semiconductor-oxide interfaces
  • 2011
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 83:19, s. 195329
  • Tidskriftsartikel (refereegranskat)abstract
    • Previously found oxidized III-V semiconductor surfaces have been generally structurally disordered and useless for applications. We disclose a family of well-ordered oxidized InAs, InGaAs, InP, and InSb surfaces found by experiments. The found epitaxial oxide-III-V interface is insulating and free of defects related to the harmful Fermi-level pinning, which opens up new possibilities to develop long-sought III-V metal-oxide-semiconductor transistors. Calculations reveal that the early stages in the oxidation process include only O-III bonds due to the geometry of the III-V(100)c(8 x 2) substrate, which is responsible for the formation of the ordered interface. The found surfaces provide a different platform to study the oxidation and properties of oxides, e. g., the origins of the photoemission shifts and electronic structures, using surface science methods.
  •  
8.
  • Århammar, Cecilia, et al. (författare)
  • Unveiling the complex electronic structure of amorphous metal oxides
  • 2011
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 108:16, s. 6355-6360
  • Tidskriftsartikel (refereegranskat)abstract
    • Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.
  •  
9.
  • Airiskallio, E., et al. (författare)
  • High temperature oxidation of Fe-Al and Fe-Cr-Al alloys : The role of Cr as a chemically active element
  • 2010
  • Ingår i: Corrosion Science. - 0010-938X. ; 52:10, s. 3394-3404
  • Tidskriftsartikel (refereegranskat)abstract
    • Good high-temperature corrosion resistance of Fe-Al alloys in oxidizing environments is due to the alpha-Al2O3 film which is formed on the surface provided temperature is above 900 degrees C and the Al-content of the alloy exceeds the critical value. Ab initio calculations combined with experiments on Fe-13Al, Fe-18Al, Fe-23Al and Fe-10Cr-10Al alloys show that the beneficial effect of Cr on the oxidation resistance is significantly related to bulk effects. The comparison of experimental and calculated results indicates a clear correlation between the Fe-Cr chemical potential difference and the formation of the protective oxide scales. (C) 2010 Elsevier Ltd. All rights reserved.
  •  
10.
  • Airiskallio, E., et al. (författare)
  • Third element effect in the surface zone of Fe-Cr-Al alloys
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 81:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that helps to maintain a sufficient Al content in the depleted zone. Several previous experiments related to our study support that conditions for such a mechanism to be functional prevail in real oxidation processes of Fe-Cr-Al alloys.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 61
 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy