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  • 1.
    Agnarsson, Björn
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Olafsson, S.
    Gislason, H. P.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Influence of initial surface reconstruction on nitridation of Al2O3 (0001) using low pressure ammonia2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 1, p. 013519-Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to investigate the effect of initial surface reconstruction on the nitridation process of Al2O3 (0001). This was done by exposing differently reconstructed sapphire substrates at different temperatures to low pressure ammonia (NH3). Structural and chemical analysis were carried out using low-electron energy diffraction and x-ray photoelectron spectroscopy. The experiments revealed that using low pressure ammonia (P-NH3 < 1 X 10(-5) Torr), no nitridation takes place on (1x1) unreconstructed surfaces. However, when the unreconstructed surface starts to change to a (root 31 x root 31) R +/- 9 degrees reconstructed surface, with increasing substrate temperature, the nitridation becomes successful. When using the initially reconstructed surface, the nitridation is successful even from the lowest temperature used. These results suggest that the initial surface reconstruction has a major effect on the nitridation process. This kinetic behavior has not been reported before, with most nitridation studies mainly focusing on the effect of surface temperature on the resulting surface morphology, rather than the actual kinetics of the process itself.

  • 2. Babonas, G. J.
    et al.
    Reza, A.
    Simkiene, I.
    Sabataityte, J.
    Baran, M.
    Szymczak, R.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Suchodolski, Arturas
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Optical properties of Fe-doped silica films on Si2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5391-5394Article in journal (Refereed)
    Abstract [en]

    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.

  • 3. Davila, M. E.
    et al.
    Avila, J.
    Ascolani, H.
    Le Lay, G.
    Göthelid, Mats
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Asensio, M. C.
    Surface phase transitions at metal-semiconductor interfaces: a revisit is needed2004In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 234, no 04-jan, p. 274-285Article in journal (Refereed)
    Abstract [en]

    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.

  • 4. Davila, Maria E.
    et al.
    Avila, Jose
    Asensio, Maria Carmen
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Le Lay, Guy
    Perturbation of Ge(111) and Si(111)root 3 alpha-Sn surfaces by adsorption of dopants2006In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 600, no 16, p. 3154-3159Article in journal (Refereed)
    Abstract [en]

    We test the response of the root 3 x root 3 alpha reconstructions formed by 1/3 monolayer of tin adatoms on silicon and germanium (111) surfaces upon doping with electrons or holes, using potassium or iodine as probes/perturbers of the initial electronic structures. From detailed synchrotron radiation photoelectron spectroscopy studies we show that doping with either electrons or holes plays a complimentary role on the Si and Ge surfaces and, especially, leads to complete conversion of the Sn 4d two-component spectra into single line shapes. We find that the low binding energy component of the Sn core level for both Si and Ge surfaces corresponds to Sn adatoms with higher electronic charge, than the Sn adatoms that contribute to the core level high binding energy signal. This could be analyzed as Sn adatoms with different valence state.

  • 5.
    Emmoth, Birger
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Khartsev, Sergiy
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Pisarev, A.
    Grishin, Alexander
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Litnovsky, A.
    Rubel, Marek J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Wienhold, P.
    Fuel removal from bumper limiter tiles by using a pulsed excimer laser2005In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 337-39, no 1-3, p. 639-643Article in journal (Refereed)
    Abstract [en]

    Samples of a limiter tile from the TEXTOR tokamak were investigated by scanning electron microscopy and nuclear reaction analysis both before and after laser heating. SEM images showed spheres and thin flakes covering the surface which are the areas modified by plasma particles striking under grazing angles. Due to roughness of the surface there are shadowed regions between the 'flakes'. Laser pulses did not lead to expected common ablation of the surface. Features that looked like 'melting' of thin surface layers were rather observed. The initial deuterium content in the surface layer of tiles was of the order of 10(18) D atoms per cm(2). After the laser light impact the content decreased with 60-70%; by reducing the deposited power by a factor four, the deuterium content was decreased by 40-50%. We make the interpretation that we approach a threshold of the laser detritiation method in fusion devices.

  • 6. Grehk, T. M.
    et al.
    Göthelid, Mats
    KTH, Superseded Departments, Materials Science and Engineering.
    Bjorkqvist, M.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Physics.
    Li-induced phase transition from the Ge(111)3X1: Li surface reconstruction to the Ge(111)root 3X root 3 : Li lithium germanide2000In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 61, no 7, p. 4963-4967Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Grishin, Michael A.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Khartsev, Sergiy
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    High performance films of binary system SrTiO3-PbZr0.52Ti0.48O3 on sapphire2001In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 39, no 1-4, p. 351-358Article in journal (Refereed)
    Abstract [en]

    Continuous series of solid solutions x.SrTiO3-(1-x).PbZr0.52Ti0.48O3 (SPZT) have been grown by pulsed laser deposition technique onto La0.7Sr0.3CoO3/Al2O3(01 (1) under bar2) single crystal. Films properties have been characterized in Au/SPZT/La0.7Sr0.3CoO3(LSCO)/Al2O3 vertical capacitive cell. X-ray diffraction shows SPZT/LSCO bilayer grows in strict epitaxial relationship with sapphire substrate: (001) SPZT parallel to (001) LSCO parallel to (01 (1) under bar2) Al2O3; [010] SPZT parallel to [010] LSCO parallel to [421] Al2O3. LSCO layer was found to be tensile strained, while SPZT film experiences tetragonal distortions c/a -1 approximate to 0.86% which are much lower than 2.73% in pure PZT ceramics. Curie temperature in SPZT film has been tailored continuously in the explored temperature range 77 K to 400 K by controlling SrTiO3:PZT ratio. Processing parameters have been optimized to get the highest tunability factor K = epsilon'(0) - epsilon'(V)/epsilon'(0) x 1/tandelta . SrTiO3:PZT=83:17 film exhibits superior properties: at I kHz maximum dielectric perinittivity and minimum loss tandelta were found to be 870 and 0.005, respectively; while K-factor exceeds value of 60 in the temperature range 280 to 350 degreesC reaching the maximum value of 64 at 325 degreesC. SPZT films can withstand prolonged pre-breakdown electric field and has resistivity as high as 3.5 10(12) Omega cm at 186 kV/cm.

  • 8.
    Grishin, Michael A.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Henrik S.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Månsson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Electron structure and electron dynamics at InSb(111)2×2 semiconductor surface2003In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 76, no 3, p. 299-302Article in journal (Refereed)
    Abstract [en]

    The conduction band electronic structure and the electron dynamics of the clean InSb(111)2 x 2 surface have been studied by laser based pump-and-probe photoemission. The results are compared to earlier studies of the InSb(110) surface. It is found that both the energy location and the time dependence of the photoexcited structures are very similar for the two surfaces. This indicates that the dominant part of the photoemission signal in the conduction band region is due to excitations of electrons in the bulk region and that the surface electronic states play a minor role. The fast decay of the excited state, tau similar to 12 ps, indicates that diffusion of hot electrons into the bulk is an important mechanism.

  • 9.
    Grishin, Michael A.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Månsson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Claesson, Thomas
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Henrik S.
    Optillion AB.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A bandgap surface state at the GaSb(001) surface observed by femtosecond laser pump-and-probe photoemission spectroscopyManuscript (Other academic)
  • 10.
    Grishin, Michael A.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Månsson, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Henrik S.
    Optillion AB.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A new two-dimensional angle-resolving multi-anode electron detector for femtosecond photoemission spectroscopyArticle in journal (Other academic)
  • 11.
    Grishin, Michael A.
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Månsson, Martin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Karlsson, Henrik S.
    Optillion AB, Stockholm.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Anisotropy of electron structure at InAs(111) surfaces by laser pump-and-probe photoemission spectroscopy2005In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 574, no 1, p. 89-94Article in journal (Refereed)
    Abstract [en]

    The electronic structure and the electron dynamics of the clean InAs(111)A 2 x 2 and the InAs(111)B 1 x 1 surfaces have been studied by laser pump-and-probe photoemission spectroscopy. Normally unpopulated electron states above the valence band maximum (VBM) are filled on the InAs(111)A surface due to the conduction band pinning above the Fermi level (E-F). Accompanied by the downward band banding alignment, a charge accumulation layer is confined to the surface region creating a two dimensional electron gas (2DEG). The decay of the photoexcited carriers above the conduction band minimum (CBM) is originated by bulk states affected by the presence of the surface. No occupied states were found on the InAs(111)B 1 x 1 surface. This fact is suggested to be due to the surface stabilisation by the charge removal from the surface into the bulk. The weak photoemission intensity above the VBM on the (111)B surface is attributed to electron states trapped by surface defects. The fast decay of the photoexcited electron states on the (111)A and the (111)B surfaces was found to be tau(111A) less than or equal to 5 ps and tau(111B) less than or equal to 4ps, respectively. We suggest the diffusion of the hot electrons into the bulk is the decay mechanism. (

  • 12.
    Göthelid, Mats
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    An ordered layer of molecular iodine on Ge(100) 2x12004In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 556, no 03-feb, p. 203-212Article in journal (Refereed)
    Abstract [en]

    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.

  • 13. Janin, E.
    et al.
    von Schenck, H.
    Hellden, S.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Göthelid, Mats
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Corrosive adsorption of Sn on the Pt(110)(1 x 2) surface2002In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 515, no 03-feb, p. 462-470Article in journal (Refereed)
    Abstract [en]

    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.

  • 14.
    Janin, Emmanuelle
    et al.
    KTH, Superseded Departments, Physics.
    Ringler, Sandrine
    KTH, Superseded Departments, Physics.
    Weissenrieder, Jonas
    KTH, Superseded Departments, Physics.
    Åkermark, Torbjörn
    KTH, Superseded Departments, Physics.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Physics.
    Göthelid, Mats
    KTH, Superseded Departments, Physics.
    Nordlund, D.
    Ogasawara, H.
    Adsorption and bonding of propene and 2-butenal on Pt(111)2001In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 482, p. 83-89Article in journal (Refereed)
    Abstract [en]

    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.

  • 15.
    Karlsson, Ulf
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    MAX IV : An ultrabrilliant synchrotron radiation facility2010Conference paper (Refereed)
  • 16. Karlsson, Ulf O
    Preface: Proceedings of the Eighth International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures and the Thirteenth International Congress on Thin Films, Stockholm, Sweden, June 20-23, 20052006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, p. 381-Article in journal (Refereed)
  • 17.
    Karlsson, Ulf O.
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Wäppling, Roger
    Preface: ACSIN8/ICTF13 - Proceedings of the Eighth International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures and the Thirteenth International Congress on Thin Films - Stockholm, Sweden, June 20-23, 20052006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5243-Article in journal (Refereed)
  • 18. Karpus, V.
    et al.
    Suchodolskis, A.
    Taulavicius, J.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Le Lay, G.
    Assmus, W.
    Bruehne, S.
    Coordination-induced structure of the Mg 2p core level in i-ZnMgR quasicrystals2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 76, no 15Article in journal (Refereed)
    Abstract [en]

    We present a detailed analysis of Mg 2p photoemission (PE) spectra in icosahedral ZnMgR (R=Y, Ho, Er) quasicrystals and in the crystalline Zn2Mg Laves phase. Synchrotron-radiation PE measurements were performed on in situ cleaved single-grain samples at 10(-10) mbar pressure and low, 90-150 K, temperature. The analysis of Mg 2p PE spectra in Zn2Mg reveals a surface shift of the core level of -0.12 eV. The Mg 2p PE spectra in i-ZnMgR quasicrystals are essentially broadened as compared to spectra in Zn2Mg Laves phase. The effect is due to the coordination-induced structure of the Mg 2p levels. Different local surroundings of Mg atoms in quasicrystals induce both different shifts of the Mg 2p level and splittings of its spin-orbit components. The local coordination potential at different Mg sites in the quasicrystalline lattice is calculated on the basis of the face-centered icosahedral ZnMgY atomic structure data, recently determined from the pair distribution function analysis. The coordination shifts calculated are spread within an interval of about 0.3 eV, while the splittings of the 2p(3/2) component are of the order of 1-10 meV. The simulated theoretical Mg 2p PE spectra of fci-ZnMgR quasicrystals perfectly fit the experimental data.

  • 19. Karpus, V.
    et al.
    Suchodolskis, Arturas
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Lay, G.
    Giovanelli, L.
    Assmus, W.
    Bruhne, S.
    Uhrig, E.
    Mg 2p shallow core-level and local atomic structure of i-ZnMgRE quasicrystals2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5411-5414Article in journal (Refereed)
    Abstract [en]

    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.

  • 20. Karpus, V.
    et al.
    Suchodolskis, Arturas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Taulavicius, J.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Assmus, W.
    Bruehne, S.
    Uhrig, E.
    Photoemission spectroscopy study of si-ZnMgHo quasicrystals2008In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 30, no 5, p. 690-692Article in journal (Refereed)
    Abstract [en]

    The results of photoemission spectroscopy of the simple-icosahedral single-grain ZnMgHo quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10(-10) mbar pressure and low, 160 K, temperature. The valence band photoemission spectra measured reveal a simple metal type valence band with a distinct Fermi edge and a sharp pseudogap feature, which originates from the van Hove singularities in the density of states. The photoemission spectra of the Mg 2p core level show the coordination shifts of Mg 2p, spin-orbit doublet due to inequivalent Mg sites in the quasicrystalline lattice.

  • 21.
    Khartsev, Sergiy
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Michael A.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Heteroepitaxial Na0.5K0.5NbO3/La0.5Sr0.5CoO3 electro-optical cell2006In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 80, p. 133-143Article in journal (Refereed)
    Abstract [en]

    We report electro-optic performance of heteroepitaxial Na0.5K0.5NbO3(1.5 mu m)/La0.5Sr0.5CoO3 (0.5 mu m) (NKN/LSCO) films grown on Al2O3(01 (1) under bar2) single crystal (r-cut sapphire) by rf-magnetron sputtering (NKN) and pulsed laser deposition (LSCO) techniques. Vertical capacitive electro-optical cells were defined by a thermal evaporation of 2 x 8 mm(2) Au electrodes through the contact mask on top the NKN film. Processing parameters have been specially optimized to obtain electrosoftNKN films with a non-linear fatigue-free P-E characteristics: low remnant P-r = 7.7 mu C/cm(2) high induced polarization P = 23 mu C/cm(2) @ 400 km/cm , and the coercive field E-c = 70 kV/cm. Electro-optical characterization of NKN films has been performed using waveguide refractometry: a prism coupling of a light beam into the thin-film waveguide modes. Intensity of TM- and TE-polarized light of 655 nm laser diode reflected from the free surface of NKN film and Au-clad NKN/LSCO waveguide was recorded at zero and 15 V (100 kV/cm) bias electric field. Fitting reflectivity spectra to Fresnel formulas yields extraordinary and ordinary refractive indices n(c) = 2.232 and n(o) = 2.234 as well as electro-optic coefficient r(13) = 17.4 pm/V. Dispersion of the refraction index follows Sellmeier formula n(2) = 1+ 3.46/[1 + (244 nm/lambda)(2)] in the range from 400 nm to 850 nm.

  • 22. Le Lay, G.
    et al.
    Rad, M. G.
    Göthelid, Mats
    KTH, Superseded Departments, Materials Science and Engineering.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Physics.
    Avila, J.
    Asensio, M. C.
    Nature of the root 3 alpha to 3 x 3 reversible phase transition at low temperature in Sn/Ge (111)2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 175, p. 201-206Article in journal (Refereed)
    Abstract [en]

    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.

  • 23.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Pailhés, Stephane
    Laboratory for Neutron Scattering, ETH Zürich.
    Chang, Johan
    Laboratory for Neutron Scattering, ETH Zürich.
    Mesot, Joël
    Laboratory for Neutron Scattering, ETH Zürich.
    Shi, Ming
    Swiss Light Source, Paul Scherrer Institut, Villigen.
    Patthey, Luc
    Swiss Light Source, Paul Scherrer Institut, Villigen.
    Momono, Naoki
    Department of Physics, Hokkaido University, Sapporo.
    Oda, Migaku
    Department of Physics, Hokkaido University, Sapporo.
    Ido, Masayuki
    Department of Physics, Hokkaido University, Sapporo.
    On-board sample cleaver2007In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 78, no 7, p. 076103-Article in journal (Refereed)
    Abstract [en]

    An on-board sample cleaver has been developed in order to cleave small and hard-to-cleave samples. To acquire good cleaves from rigid samples the alignment of the cleaving blade with respect to the internal crystallographic planes is crucial. To have the opportunity to mount the sample and align it to the blade ex situ has many advantages. The design presented has allowed us to cleave very tiny and rigid samples, e.g., the high-temperature superconductor La(2-x)SrxCuO4. Further, in this design the sample and the cleaver will have the same temperature, allowing us to cleave and keep the sample at low temperature. This is a big advantage over prior cleaver systems. As a result, better surfaces and alignments can be realized, which considerably simplifies and improves the experiments.

  • 24.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Grishin, Michael A.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Karlsson, Henrik S.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Electronic structure and electron dynamics at the GaSb(001) surface studied by femtosecond pump-and-probe pulsed laser photoemission spectroscopy2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5308-5311Article in journal (Refereed)
    Abstract [en]

    Transiently excited electron states at the GaSb(001) surface have been studied by means of time- and angle-resolved photoemission spectroscopy based on a femtosecond laser system. A normally unpopulated surface electron state has been found at similar to 250 meV above the valence band maximum with a strong confinement at the center of the surface Brillouin zone. The lifetime of transiently excited carriers at the intergap surface states has been found to be similar to 11 ps, associated with rapid carrier diffusion.

  • 25.
    Månsson, Martin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Grishin, Michael A.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Ultrafast electron dynamics and recombination at the Ge(111): Sn(root 3 X root 3)R30 degrees surface2008In: Surface Science Letters, ISSN 0039-6028, Vol. 602, no 5, p. L33-L37Article in journal (Refereed)
    Abstract [en]

    We present the first study revealing the electronic structure and electron dynamics of the excited adatom state at the Ge(111): Sn(root 3 x root 3)R30 degrees surface. By the use of time- and angle-resolved photoemission spectroscopy, the normally unoccupied electronic structure of the partly empty Sn adatom can be probed. From the angle-resolved data we conclude that the adatom electrons at the Ge:Sn surface are more delocalized than at the clean Ge(111)c(2 x 8) surface. A unique pump-and-probe technique, based on a pulsed femtosecond laser-system, has also allowed us to study the recombination process of the excited state. We connect the recombination process of the excited electrons to the coherent fluctuations of the Sn adatoms. As a result we present an estimate for the time between each collective and coherent adatom flip Delta t = 9 ps, i.e. an adatom switching frequency nu(SW) approximate to 0.1 THz. We find that our results, contrary to scanning tunneling microscopy measurements [F. Ronci, S. Colonna, S.D. Thorpe, A. Cricenti, G. Le Lay, Phys. Rev. Lett. 95 (2005) 156101], agree very well with values extracted from molecular dynamics simulations found in the literature [J. Avila, A. Mascaraque, E.G. Michel, M.C. Asensio, G. Le Lay, J. Ortega, R. Perez, F. Flores, Phys. Rev. Lett. 82 (1999) 442; D. Farias, W. Kaminski, J. Lobo, J. Ortega, E. Hulpke, R. Perez, F. Flores, E.G. Michel, Phys. Rev. Lett. 91 (2003) 16103].

  • 26.
    Palmgren, Pål
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Szamota-Leandersson, Katolina
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Claesson, Thomas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Chemical reaction and interface formation on InAs(111)-Co surfaces2005In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 574, no 2-3, p. 181-192Article in journal (Refereed)
    Abstract [en]

    We report a study of the initial interface formation of Co on InAs(1 1 1)A and B surfaces using high resolution photoelectron spectroscopy and scanning tunneling microscopy. We observe a strong chemical interaction between Co and, in particular, surface indium forming a metallic overlayer already below monolayer coverage. On annealed surfaces this overlayer agglomerates into islands, with a narrow size distribution. Furthermore, no two-dimensional electron gas is formed on InAs(1 1 1)A-Co in contrast to the clean surface.

  • 27.
    Rad, Goshtasbi
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Göthelid, Mats
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Cerium-induced reconstructions on the Si(111) surface2004In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 558, no 03-jan, p. 49-56Article in journal (Refereed)
    Abstract [en]

    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.

  • 28.
    Stoltz, Dunja
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    High resolution spectroscopic and microscopic signatures of ordered growth of ferrous sulfate in SO2 assisted corrosion of Fe3O4(100)2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 9Article in journal (Refereed)
    Abstract [en]

    The authors present a high-resolution core-level photoemission study of a Fe3O4(100) surface exposed to 50 L (1 L=10(-6) mbar s) of H2O and 50 L of SO2. S 2p core-level spectra reveal the presence of SO3 and SO4 species. An additional peak in the Fe 3p core-level spectrum shows that they bond with iron from the substrate. Complementary scanning tunneling microscopy of the same surface demonstrates formation of a long-range ordered sulfate locked in the (root 2x root 2)R45 degrees-surface potential.

  • 29.
    Stoltz, Dunja
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Scanning tunneling microscopy of Fe- and O-sublattices on Fe3O4(100)2008In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 108, no 6, p. 540-544Article in journal (Refereed)
    Abstract [en]

    We present scanning tunneling microscopy of an octahedral (B) plane terminated (root 2 x root 2)R45 degrees-reconstructed surface of a natural magnetite (10 0) crystal. Implementing a W-tip we achieve the same resolution on Fe rows as was reported in the past either with the use of antiferromagnetic tips or on magnetite (Fe3O4) films. We show images of Fe or O sublattices of Fe3O4 with atomic resolution.

  • 30. Suchodolskis, A.
    et al.
    Assmus, W.
    Babonas, G. J.
    Giovanelli, L.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karpus, V.
    Le Lay, G.
    Reza, A.
    Uhrig, E.
    Photoemission and optical spectroscopy of i-ZnMgEr quasicrystal2005In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 107, no 2, p. 412-419Article in journal (Refereed)
    Abstract [en]

    The results of photoemission and optical studies of icosahedral single-grain ZnMgEr quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10(-10) mbar pressure and low, 140-150 K temperature. The valence band photoemission spectra measured reveal a simple metal-type valence band of icosahedral ZnMgEr with a distinct Fermi edge cut-off and with a sharp pseudogap feature. The photoemission spectra of shallow Mg 2p and Zn 3d core levels indicate a coordination shift of Mg 2p spin-orbit doublet and an oscillating dependence of Zn 3d photoemission line components on the photon energy within the hv = 20-160 eV range investigated. The optical response of icosahedral ZnMgEr, a dispersion of the dielectric function, was measured by the spectroscopic ellipsometry technique in the 0.5-5.0 eV spectral range. The optical spectra of the quasicrystal indicate the Drude-type optical response superimposed with a peak of interband optical transitions. The interband optical transitions can be modelled with the pseudogap parameters which agree with those deduced in an analysis of the photoemission valence band spectra.

  • 31. Suchodolskis, A.
    et al.
    Assmus, W.
    Cechavicius, B.
    Dalmas, J.
    Giovanelli, L.
    Göthelid, Mats
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karpus, V.
    Le Lay, G.
    Sterzel, R.
    Uhrig, E.
    Pseudogap structure in icosahedral ZnMgY and ZnMgHo quasicrystals2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 212, p. 485-490Article in journal (Refereed)
    Abstract [en]

    The results of a photoemission study of icosahedral single-grain ZnMg(Y, Ho) quasicrystals and their crystalline approximant Zn2Mg are presented. Synchrotron radiation photoemission measurements have been performed on in situ cleaved samples at low temperature of approximate to90 K and 10(-10) mbar pressure. The spectra obtained indicate simple metal-type valence bands (VB) with distinct Fermi edge cutoff. Analysis of the Fermi edge spectra reveals the presence of a pseudogap in i-ZnMg(Y, Ho) quasicrystals. The pseudogap corresponds to a rather sharp DOS dip at the Fermi level with th approximate to50% (of the normal DOS) depth and the approximate to0.8 eV width. The values of i-ZnMg(Y, Ho) pseudogap parameters are comparable with those of other quasicrystals.

  • 32. Suchodolskis, A.
    et al.
    Assmus, W.
    Giovanelli, L.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karpus, V.
    Le Lay, G.
    Sterzel, R.
    Uhrig, E.
    Indication of van Hove singularities in the density of states of ZnMg(Y,Ho) quasicrystals2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 5Article in journal (Refereed)
    Abstract [en]

    We present a low-temperature synchrotron-radiation photoelectron microspectroscopy study of the valence bands of single-grain icosahedral ZnMgY and ZnMgHo quasicrystals. Their valence band photoemission spectra reveal in both cases a simple metal-type behavior with a clear metallic Fermi edge and a sharp pseudogap feature: the spectral intensity exhibits a maximum at approximate to0.7 eV below the chemical potential and a subsequent decrease as the Fermi level is approached. The analysis of the pseudogap feature, based on the band-structure hypothesis, shows that it corresponds to the van Hove singularities in the density of states (DOS), which originate from the intersections of the isoenergetic surface with the 222100 and 311111 Bragg planes. The reconstructed density of states agrees in general trends with the theoretical first-principles DOS of hexagonal ZnMgY approximants, and correctly reproduces the experimental value of i-ZnMgY electronic specific-heat coefficient.

  • 33. Suchodolskis, A.
    et al.
    Assmus, W.
    Giovanelli, L.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karpus, V.
    Le Lay, G.
    Uhrig, E.
    Valence band structure of i-ZnMgEr quasicrystal: photoemission study2004In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 16, no 50, p. 9137-9142Article in journal (Refereed)
    Abstract [en]

    The results of photoemission study of icosahedral single-grain ZnMgEr quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10(-10) mbar pressure and low, 140-150 K, temperature. The valence band photoemission spectra measured reveal a simple-metal type valence band of i-ZnMgEr with a distinct Fermi edge cutoff and a spectral feature at 0.7 eV below epsilon(F). Analysis of the PE spectra shows that the spectral feature observed corresponds to the van Hove singularities in the density of states, which are due to intersections of the Fermi surface with the 222100 and 311111 Bragg planes.

  • 34. Suchodolskis, A.
    et al.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Linnarsson, Margareta K
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Österman, John
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Ion implantation damage annealing in 4H-SiC monitored by scanning spreading resistance microscopy2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, p. 611-614Article in journal (Refereed)
    Abstract [en]

    To obtain a better understanding of the damage annealing process and dopant defect incorporation and activation we have implanted epitaxially grown 4H-SiC layers with high doses of Al+ ions. Cross-sections of the samples are investigated by scanning spreading resistance microscopy (SSRM) using a commercial atomic force microscopy (AFM). The defects caused by the implanted ions compensate for the doping and decrease the charge carrier mobility. This causes the resistivity to increase in the as-implanted regions. The calculated profile of implanted ions is in good agreement with the measured ones and shows a skewed Gaussian shape. Implanted samples are annealed up to 400 degrees C. Despite these low annealing temperatures we observe a clear improvement of the sample conductivity in the asimplanted region.

  • 35.
    Suchodolskis, Arturas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Gran, J.
    Hansen, T. E.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Scanning spreading resistance microscopy of shallow doping profiles in silicon2006In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 253, no 02-jan, p. 141-144Article in journal (Refereed)
    Abstract [en]

    We demonstrate the application of scanning spreading resistance microscopy (SSRM) for characterization of shallow highly-conductive layers formed by boron implantation of lowly doped n-type silicon substrate followed by a post-implantation annealing. The electrically active dopant concentration versus depth was obtained from a cross-section of freshly cleaved samples where the Si-surface could be clearly distinguished by depositing a SiO2-layer before cleavage. To quantify free carrier concentration we calibrated our data against samples with implanted/annealed boron profiles established by secondary ion mass spectrometry (SIMS). A good fit of SSRM and SIMS data is possible for free carrier concentrations lower than 10(20) cm(-3), but for higher concentrations there is a discrepancy indicating an incomplete activation of the boron.

  • 36.
    Suchodolskis, Arturas
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Karpus, V.
    Kanski, J.
    Ilver, L.
    Göthelid, Mats
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Photoemission studies of Mg and Rb layers on Zn(0001)2004In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 137-40, p. 189-192Article in journal (Refereed)
    Abstract [en]

    The electronic structure of the clean Zn(0 0 0 1) surface is studied by angle resolved photoemission. An earlier detected surface state at the surface Brillouin zone centre is confirmed and a new surface state is found at the surface Brilluoin zone boundary. The surface electronic structure of Zn is found to be similar to the that of Cd. Evaporation of thin films of Mg and Rb onto the Zn(0 0 0 1) surface quenches the emission from both surface states and reduces the intensity of the bulk related structures.

  • 37.
    Szamota Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Göthelid, Mats
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Interaction between oxygen and InAs(111) surfaces, influence of the electron accumulation layer2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 212, p. 589-594Article in journal (Refereed)
    Abstract [en]

    The oxidation of InAs(1 1 1) surfaces has been studied by photoelectron spectroscopy. Both the InAs(1 1 1)A and the InAs(1 1 1)B surfaces are studied and it. is found that the initial oxidation follows different paths for the two surfaces. At low oxygen exposures of the A face the Fermi level structure, which is due to the electron accumulation layer, increases in intensity. On the B-side the intensity of the lone pair surface state decreases with increasing oxygen exposure. For larger exposures significant changes can be observed in the line shape of the In 4d and the As 3d core levels.

  • 38.
    Szamota-Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Bugoi, R.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Pb induced charge accumulation on InAs(111)B2007In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 601, no 15, p. 3246-3252Article in journal (Refereed)
    Abstract [en]

    The Pb/InAs(111)B interface has been studied by synchrotron radiation photoelectron spectroscopy (SR-PES) of valence band and ln4d, As3d and Pb5d core levels. Room temperature deposition of similar to 1 ML of Pb on InAs(I I I)B leads to an ordered overlayer that induces a metallic channel at the surface, as seen through a weak emission in the vicinity of the Fermi level. Its narrow localization in reciprocal space supports the formation of a two-dimensional free electron gas (2DEG) in the surface region. It is proposed that the adsorbed metal layer swaps the initial polarisation of the surface and thus pulls electrons back to the surface. This charge re-arrangement increases the charge density in the accumulation layer and reduces the screening length and thus the depth of the potential well at the surface.

  • 39.
    Szamota-Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Kanski, J.
    Ilver, L.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Creation of a metallic channel at the Sn/InAs(111)B surface studied using synchrotron-radiation photoelectron spectroscopy2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 205406Article in journal (Refereed)
    Abstract [en]

    The properties of a Sn-induced two-dimensional electron gas at the As-terminated InAs(111)B(1x1) surface was studied by synchrotron radiation photoelectron spectroscopy. The two-dimensional electron gas reveals itself via a narrow structure at the Fermi level, visible close to normal emission for tin coverage in the range 0.5 to 2 monolayers. Although this electron gas exhibits properties that in several respects resemble those of intrinsic charge accumulation layers on free InAs surfaces, our observations suggest that the present electron gas is much more linked to the Sn adlayer.

  • 40.
    Szamota-Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Leandersson, M.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Adsorption of Cs on InAs(111) surfaces2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5267-5270Article in journal (Refereed)
    Abstract [en]

    Caesiated InAs(111)B (1 x 1) and InAs(111)A (2 x 2) surfaces have been studied by photoelectron spectroscopy. On the InAs(111)B a new (root 3 x root 3)R30 degrees reconstruction was observed. During Cs evaporation remarkably small changes are observed in the lone pair states, and no sign of an accumulation layer at the surface can be observed. Instead, the additional charge provided by Cs is rapidly transported towards the bulk. On the InAs(111)A cesium behaves as a typical electropositive alkali metal donator that enhances the already existing accumulation layer.

  • 41.
    Szamota-Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Leandersson, Mats
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Correlated development of a (2x2) reconstruction and acharge accumulation layer on the InAs(111)-Bi surface2011In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 605, no 1-2, p. 12-17Article in journal (Refereed)
    Abstract [en]

    We have studied the formation of a Bi induced (2x2) reconstruction on the InAs(111)Bsurface. In connection to the development of the (2x2) reconstruction, a two dimensionalcharge accumulation layer located in the bottom of the InAs conduction band appears as seenthrough a photoemission structure at the Fermi level. Not well ordered Bi layers do not inducea charge accumulation. The Bi induced reconstruction reduces the polarisation of the pristinesurface and changes the initial charge distribution. InAsBi alloying occurs below the surfacewhere Bi act as charge donor leading to the charge accumulation layer.

  • 42.
    Szamota-Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Leandersson, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Palmgren, Pål
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Electronic structure of bismuth terminated InAs(100)2009In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 603, no 1, p. 190-196Article in journal (Refereed)
    Abstract [en]

    Deposition of Bi onto (4 x 2)/c(8 x 2)-InAs(1 0 0) and subsequent annealing results in a (2 x 6) surface reconstruction as seen by low electron energy diffraction. The Bi condensation eliminates the original (4 x 2) Surface reconstruction and creates a new Structure including Bi-dimers. This Surface is metallic and hosts a charge accumulation layer seen through photoemission intensity near the Fermi level. The accumulation layer is located in the bulk region below the surface, but the intensity of the Fermi level structure is strongly dependent oil the Surface order.

  • 43. Uhrberg, R I G
    et al.
    Hansson, G V
    Karlsson, Ulf O
    KTH, School of Information and Communication Technology (ICT).
    Nicholls, J M
    Persson, P E S
    Flodström, S Anders
    Engelhardt, R
    Koch, EE
    Well-Known "Surface State" on Si(111)2×1 Identified as a Bulk Contribution1984In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 52, no 25, p. 2265-2268Article in journal (Refereed)
    Abstract [en]

    Using polarization-dependent angle-resolved photoemission we show that two dominating structures in the photoemission spectra are due to direct transitions from the uppermost two valence bands in silicon. The final-state band for these transitions at photon energies 10.2-21.2 eV is found to have free-electron-like dispersion. Our results imply that that threefold-symmetry emission often assigned to back-bond surface states on Si(111)2×1 is really due to bulk photoemission.

  • 44.
    Weissenrieder, Jonas
    et al.
    KTH, Superseded Departments, Physics.
    Göthelid, Mats
    KTH, Superseded Departments, Physics.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Physics.
    Investigation of the surface phase diagram of Fe(110)-S2002In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 515, no 1, p. 135-142Article in journal (Refereed)
    Abstract [en]

    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.

  • 45.
    Weissenrieder, Jonas
    et al.
    KTH, Superseded Departments, Physics.
    Göthelid, Mats
    KTH, Superseded Departments, Physics.
    Månsson, Martin
    KTH, Superseded Departments, Physics.
    von Schenck, Henrik
    KTH, Superseded Departments, Physics.
    Tjernberg, Oscar
    KTH, Superseded Departments, Physics.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Physics.
    Oxygen structures on Fe(110)2003In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 527, no 03-jan, p. 163-172Article in journal (Refereed)
    Abstract [en]

    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.

  • 46.
    Weissenrieder, Jonas
    et al.
    KTH, Superseded Departments, Physics. KTH, Superseded Departments, Materials Science and Engineering.
    Leygraf, Christofer
    KTH, Superseded Departments, Materials Science and Engineering.
    Göthelid, Mats
    KTH, Superseded Departments, Physics.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Physics.
    Photoelectron microscopy of filiform corrosion of aluminum2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 218, no 1-4, p. 154-161Article in journal (Refereed)
    Abstract [en]

    Aluminum samples have been investigated during and after exposure to well-controlled amounts of NaCl and humidified air. With infrared reflection absorption spectroscopy the deliquescence of NaCl crystallites could be followed in situ at high relative humidity (RH), as well as the growth of different aluminum oxide, hydroxide and chloride corrosion products. Investigations with scanning electron microscopy and energy dispersive X-ray analysis after exposure revealed the growth of filaments representative of filiform corrosion and chlorine enrichment in the filament heads. The exposed samples were further investigated with synchrotron based photoelectron microscopy/spectroscopy. Spectra taken of the Al 2p core level showed an intricate structure with multiple components in the core level. By means of mapping the intensity of the different chemical states within the core level the distribution of compounds over the surface could be determined. An enrichment of aluminum chloride containing compounds was found in the heads of the filaments, whereas aluminum oxides or hydroxides were observed both inside and outside the filaments.

  • 47.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dibos, A.
    Lee, Hyung-Seok
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wu, J. Z.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Growth of boron nano-junctions2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5587-5589Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate the synthesis of various types of boron nanowire junctions in a self-assembled manner by simple closed-tube thermal vapor transfer method. The Y-type boron nano-junctions and lateral boron-silicon alloy nano-junctions were grown on Si substrates, based on the oxide assisted VLS growth mode at a relatively low processing temperature regime and the VLS growth mode at the high processing temperature regime, respectively.

  • 48.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Lee, Hyung-Seok
    Kwon, Young Ha
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Koo, Sang Mo
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Multifunctional silicon inspired by a wing of male Papilio ulysse2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 3, p. 033109-Article in journal (Refereed)
    Abstract [en]

    Effective entrapment of air and light is a key element for maintaining stable superhydrophobicity and enhancing anti-reflection or absorption. Inspired by a wing of male Papilio ulysse having a unique structure for enabling effective trapping of air and light, we demonstrate that the structure consisting of well-defined multilayer decorated by nanostructures can be obtained on a silicon wafer by a simple microelectromechanical process, consequently resulted in stable superhydrophobocity under static and dynamic conditions, and strong wideband optical absorption.

  • 49.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wu, J. I.
    Dibos, A.
    Zou, X. D.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Self-assembled boron nanowire Y-junctions2006In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 6, no 3, p. 385-389Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate that boron nanowire Y-junctions can be synthesized in a self-assembled manner by fusing two individual boron nanowires grown inclined toward each other. We show that the presence of a second liquid, in addition to the liquid Au catalyst, is critical to the inclination of the boron nanowire. The structure of the BNYJ arrays that we report here may allow construction of three- or multiple-terminal nanowire devices directly on Si-based readout circuits through controlled nanowire growth.

  • 50.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wu, J. Z.
    Dibos, A.
    Gao, X.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Growth of inclined boron nanowire bundle arrays in an oxide-assisted vapor-liquid-solid process2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 11, p. 113109-Article in journal (Refereed)
    Abstract [en]

    In the vapor-liquid-solid process typically employed for semiconductor nanowire growth, nucleation and anisotropic crystal growth of single nanowires are achieved with generation of a solid/liquid alloy interface using metal catalysts. The nucleation and growth mechanism of nanowires may be greatly altered when a second liquid is introduced into the solid/liquid alloy interface. In this work, we demonstrate bundled boron nanowire (BNW) array growth on Au coated Si substrates by introducing a second liquid of B2O3 onto the solid (B)/liquid alloy (Au-B) interface. The BNWs in each bundle are straight but highly inclined with respect to the normal of the substrate. A study of BNW morphology and chemical elemental distribution using electron microscopy and energy dispersive x-ray spectroscopy suggested that the catalyst Au provided the nucleation site for BNW bundles while the liquid B2O3 modified the initiation of BNWs from each nucleation site, resulting in multiple initiation of the BNWs from each site.

12 1 - 50 of 57
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