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  • 1. Arimoto, M.
    et al.
    Kanai, Y.
    Ueno, M.
    Kataoka, J.
    Kawai, N.
    Tanaka, T.
    Yamamoto, K.
    Takahashi, H.
    Mizuno, T.
    Fukazawa, Y.
    Axelsson, Magnus
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Kiss, Mózsi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Marini Bettolo, Cecilia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Carlson, Per
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Klamra, Wlodzimierz
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Chen, P.
    Craig, B.
    Kamae, T.
    Madejski, G.
    Ng, J. S. T.
    Rogers, R.
    Tajima, H.
    Thurston, T. S.
    Saito, Y.
    Takahashi, T.
    Gunji, S.
    Bjornsson, Ca.
    Larsson, S.
    Ryde, Felix
    Bogaert, G.
    Varner, G.
    Performance assessment study of the balloon-borne astronomical soft gamma-ray polarimeter PoGOLite2007In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 40, no 2, p. 438-441Article in journal (Refereed)
    Abstract [en]

    Measurements of polarization play a crucial role in the understanding of the dominant emission mechanism of astronomical sources. Polarized Gamma-ray Observer-Light version (PoGOLite) is a balloon-borne astronomical soft gamma-ray polarimeter at the 25-80 keV band. The PoGOLite detector consists of a hexagonal close-packed array of 217 Phoswich detector cells (PDCs) and side anti-coincidence shields (SASs) made of BGO crystals surrounding PDCs. Each PDC consists of a slow hollow scintillator, a fast scintillator and a BGO crystal that connects to a photomultiplier tube at the end. To examine the PoGOLite's capability and estimate the performance, we conducted experiments with the PDC using radioisotope 241Am. In addition, we compared this result with performance expected by Monte Carlo simulation with Geant4. As a result, we found that the actual PDC has the capability to detect a 100 m Crab source until 80 keV.

  • 2. Borman, V. D.
    et al.
    Tronin, I. V.
    Tronin, V. N.
    Troyan, V. I.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Skorodumova, N. V.
    Formation of high- and low-density clusters in a 1D system2008In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 40, no 3, p. 643-648Article in journal (Refereed)
    Abstract [en]

    The properties of monoatomic chains have been studied theoretically by means of statistical mechanics methods. The applied approach can be used to evaluate the interatomic distances and lifetimes of one-dimensional (1D) and quasi-1D systems. In particular, we show that the 1D clusters of gold atoms can exist in two states with different lattice parameters (similar to 3.6 and similar to 2.8 angstrom) that can explain the whole variety of experimental observations on monoatomic gold chains without assuming any wire contamination.

  • 3.
    Chandar, Nagamuthu Krishna
    et al.
    Centre for Nanoscience and Technology, Anna University, Chennai 600025, India .
    Jayavel, R.
    Synthesis and characterization of C(14)TAB passivated cerium oxide nanoparticles prepared by co-precipitation route2014In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 58, p. 48-51Article in journal (Refereed)
    Abstract [en]

    A facile co-precipitation route has been employed to synthesize cerium oxide (CeO2) nanoparticles using cationic surfactant (tetradecyltrimethyl ammonium bromide, C(14)TAB) and cerium nitrate hexahydrate at room temperature. X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), selected area electron diffraction (SAED), fourier transform infrared spectroscopy (FT-IR), UV-vis spectrophotometer and photoluminescence spectroscopy (PL) were employed to characterize the as-prepared sample. The XRD pattern showed cubic fluorite structure of CeO2 without any impurity peaks, revealing high purity of the sample. The lattice strain experienced by the sample was analyzed using Williamson-Hall plot. FTIR studies confirmed the presence of C(14)TAB on the CeO2 nanoparticles. TEM revealed that the as-prepared CeO2 sample consists of uniform particles with particle size of 10 nm. The red shift phenomenon was observed in UV-vis spectrum, which was further supported by PL studies.

  • 4. Dumanov, E. V.
    et al.
    Podlesny, I. V.
    Moskalenko, S. A.
    Liberman, Mikhail A.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Interaction of two-dimensional magnetoexcitons2017In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 88, p. 77-86Article in journal (Refereed)
    Abstract [en]

    We study interaction of the two-dimensional magnetoexcitons with in-plane wave vector k→∥=0, taking into account the influence of the excited Landau levels (ELLs) and of the external electric field perpendicular to the surface of the quantum well and parallel to the external magnetic field. It is shown that the account of the ELLs gives rise to the repulsion between the spinless magnetoexcitons with k→∥=0 in the Fock approximation, with the interaction constant g decreasing inverse proportional to the magnetic field strength B (g(0)∼1/B). In the presence of the perpendicular electric field the Rashba spin-orbit coupling (RSOC), Zeeman splitting (ZS) and nonparabolicity of the heavy-hole dispersion law affect the Landau quantization of the electrons and holes. They move along the new cyclotron orbits, change their Coulomb interactions and cause the interaction between 2D magnetoexcitons with k→∥=0. The changes of the Coulomb interactions caused by the electrons and by the holes moving with new cyclotron orbits are characterized by some coefficients, which in the absence of the electric field turn to be unity. The differences between these coefficients of the electron-hole pairs forming the magnetoexcitons determine their affinities to the interactions. The interactions between the homogeneous, semihomogeneous and heterogeneous magnetoexcitons forming the symmetric states with the same signs of their affinities are attractive whereas in the case of different sign affinities are repulsive. In the heterogeneous asymmetric states the interactions have opposite signs in comparison with the symmetric states. In all these cases the interaction constant g have the dependence g(0)~1/B.

  • 5.
    Ekenberg, Ulf
    et al.
    KTH, Superseded Departments, Physics.
    Mauritz, O.
    Control of spontaneous spin splitting in an asymmetric quantum well with the use of strain and/or magnetic field2001In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 10, no 03-jan, p. 81-85Article in journal (Refereed)
    Abstract [en]

    Spin-orbit coupling combined with inversion asymmetry gives rise to spin splitting even in the absence of an applied magnetic field. The size of this spin splitting can be controlled by changing the degree of asymmetry using a gate voltage. We present here other less obvious ways of controlling the spontaneous spin splitting in a two-dimensional hole gas, where these effects are particularly large. Applying moderate stress can easily decrease the spin splitting by an order of magnitude. The mechanism is the strain-induced energy shift of the heavy-hole and light-hole subbands, which diminishes the degree of band mixing, which is found to be strongly correlated to the spin splitting. An applied magnetic field causes an additional Zeeman splitting, but we find that a magnetic field of 1T can be sufficient to practically erase the difference between a symmetric quantum well (without subband splitting) and an asymmetric quantum well. We have simulated Shubnikov-de Haas oscillations and found that two periodicities in 1/B can occur even for one filled spin-degenerate hole subband.

  • 6.
    Gvozdic, Dejan M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Beyond the Rashba model2006In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 32, no 02-jan, p. 458-461Article in journal (Refereed)
    Abstract [en]

    We analyze some common approximations made in connection with the Rashba effect, where a macroscopic electric field gives rise to a spin splitting. We demonstrate that the size of the Rashba splitting is not given by the expectation value of the electric field or some other average electric field, as is commonly assumed. Instead we find that the local electric field near an interface of a wide asymmetric modulation-doped quantum well can give rise to a Rashba splitting that is an order of magnitude larger than expected from the average electric field. The localization of the wave functions of the spin subbands can be quite sensitive to the parallel wave vector. Clear deviations from an energy-independent wave vector splitting occur when nonparabolicity is taken into account.

  • 7.
    Gvozdic, Dejan M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Investigation of the super-efficient Rashba effect by simulation of Shubnikov-de Haas oscillations in a two-dimensional hole gas2006In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 34, no 02-jan, p. 377-380Article in journal (Refereed)
    Abstract [en]

    The Shubnikov-de Haas effect is frequently used for two-dimensional systems to determine individual subband populations, e.g. when the subbands are split by the Rashba effect. We have previously shown that the Rashba effect can give a wave vector splitting for holes that is up to three orders of magnitude larger than for electrons at the same electric field. To reach the optimum we have made a careful design of a modulation-doped quantum well with a top gate in which the negative differential Rashba effect is utilized. From the calculated hole Landau levels we determine the density of states at the Fermi energy and demonstrate a clear difference between the symmetric case without bias and the asymmetric case with a gate voltage of 100 meV, where the spin subband populations differ by a factor 3.

  • 8. Gvozdic, Dejan M.
    et al.
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Rapid spin flip in a spin subband at an anticrossing region in a slightly asymmetric modulation-doped quantum well2008In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 40, no 6, p. 2081-2083Article in journal (Refereed)
    Abstract [en]

    The spin splitting due to structure and bulk inversion asymmetry is calculated for electron subbands in wide slightly asymmetric InGaSb quantum wells. At anticrossings, rapid spin flips in two steps are found as the in-plane wave vector along the [1 1] direction is increased by 0.002 nm(-1). First the y-component and then the x-component is flipped. A change of bias of about 1 meV across the quantum well is sufficient move the Fermi level across the anticrossing region.

  • 9. Kamp, M.
    et al.
    Happ, T.
    Mahnkopf, S.
    Duan, G.
    Anand, Srinivasan
    KTH, Superseded Departments, Electronics.
    Forchel, A.
    Semiconductor photonic crystals for optoelectronics2004In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 21, no 2-4, p. 802-808Article in journal (Refereed)
    Abstract [en]

    We present a number of designs for the integration of photonic crystals (PC) with active semiconductor devices. As a first step, the use of PC blocks as laser mirrors is demonstrated. Ridge-waveguide lasers with a length of 100 mum and two PC mirrors achieve threshold currents below 8 mA. In order to obtain single-mode operation, an intracavity PC mirror can be used, which effectively separates the laser into two coupled cavities. Lasing occurs where two modes of the cavities coincide, leading to single-mode operation with a side-mode suppression ratio (SMSR) of over 35 dB. We also present two full PC devices: a single-mode laser with a coupled resonant cavity waveguide (CROW) and a tunable laser. The CROW device consists of a chain of 40 hexagonal cavities formed in a block of PC, with a total length of 140 mum. Low threshold, single-mode operation with over 40 dB SMSR is demonstrated. Coupled cavities are used for the tunable PC laser, which covers a tuning range of over 30 nm.

  • 10.
    Lin, Lili
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Jiang, Jun
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Elastic and inelastic electron transport in metal-molecule(s)-metal junctions2013In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 47, p. 167-187Article, review/survey (Refereed)
    Abstract [en]

    An overview of studies on-elastic and inelastic electron transport properties of molecular junction devices is presented. The development of the experimental fabrication and characterization of molecular junctions as well as the corresponding theoretical modeling is briefly summarized. The functions of molecular devices are generally governed by the intrinsic structure-property relationships, and strongly affected by various environment factors including temperature, solvent and intermolecular interactions. Those detailed structural and environmental information could be probed by a powerful tool of inelastic electron tunneling spectroscopy, for which the theoretical modeling becomes particularly important. With many successful examples, it is demonstrated that the combination of theoretical simulations and experimental measurements can help not only to understand the electron-phonon interaction, but more importantly also to accurately determine the real configurations of molecules inside the junctions.

  • 11. Mauritz, O.
    et al.
    Ekenberg, Ulf
    KTH, Superseded Departments, Physics.
    Magnetic-field-induced suppression of spontaneous spin-splitting of hole subbands2000In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 6, no 04-jan, p. 779-782Article in journal (Refereed)
    Abstract [en]

    The spin-splitting in the valence band in an InxGa1-xAs/InxGa1-xAsyP1-y quantum well is investigated theoretically using a 6 x 6 Luttinger-Kohn Hamiltonian. We compare the Landau levels in a perpendicular magnetic field with the corresponding results for the subband dispersion;. It is shown that the asymmetry of the quantum well has a very small impact on the Landau level splitting for B > 1 T in sharp contrast to the subbands in the absence of a magnetic field. The significance of our findings on the interpretation of Shubnikov-de Haas experiments is discussed.

  • 12. Moskalenko, S. A.
    et al.
    Liberman, M. A.
    Snoke, D. W.
    Botan, V. V.
    Johansson, Börje
    Bose-Einstein condensation of excitons in ideal two-dimensional system in a strong magnetic field2003In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 19, no 3, p. 278-288Article in journal (Refereed)
  • 13.
    Olsson, Fredrik
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mion, Gaël
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sun, YanTing
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sundgren, Petrus
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Baskar, Krishnan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Armani, N.
    Hammar, Mattias
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Selective area growth of GaInNAs/GaAs by MOVPE2004In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 23, no 04-mar, p. 347-351Article in journal (Refereed)
    Abstract [en]

    Selective area growth (SAG) of GaInNAs/GaAs systems has been studied by metalorganic vapor-phase epitaxy (MOVPE) for the first time. This also includes a comparative study of SAG of the GaInAs/GaAs. The patterns consisted of various filling factors (F). The band gap changes and the growth morphology have been investigated. A red-shift observed for SAG GaInAs is similar to100 nm with respect to the planar GaInAs which can be attributed to both In enrichment and quantum well (QW) thickness enhancement. Selectively grown GaInNAs structures exhibit a maximum wavelength of 1.3 mum, corresponding to a red-shift of similar to80 nm with respect to the planar GaInNAs. Atomic force microscopy (AFM) scans reveal a three-dimensional growth behaviour for SAG GaInNAs unlike SAG GaInAs. This can be related to a certain amount of phase separation or strain that are often the signatures of N incorporation. The cathodoluminescence (CL) intensities (spectral line width) for SAG GaInNAs are larger (smaller) than those for SAG GaInAs at low F's but smaller (larger) at high F's. This indicates that at low F's, GaInAs has degraded due to very high strain but certain amount of strain compensation occurs in GaInNAs.

  • 14.
    Podlesny, I. V.
    et al.
    Institute of Applied Physics, Academic Str. 5, Chisinau, MD-2028, Moldova.
    Zubac, I. A.
    Institute of Applied Physics, Academic Str. 5, Chisinau, MD-2028, Moldova.
    Hoang, C. N.
    Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Ba Dinh, Hanoi, Viet Nam.
    Liberman, Michael A.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Metastable bound states of the quasi–bimagnetoexcitons in the lowest Landau levels approximation2020In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 115, article id 113638Article in journal (Refereed)
    Abstract [en]

    Four different spin structures of two electrons and of two holes situated on the lowest Landau levels (LLLs) are taken into account to investigate possible bound states of the two-dimensional magnetic biexciton formed of two magnetoexcitons with opposite wave vectors and antiparallel dipole moments. The singlet and triplet states of the spins of two electrons and of two holes separately, as well as of two para- and two ortho-magnetoexcitons are considered. The general expressions describing the binding energy of the bound states and the normalization conditions characterized by the effective spin parameter η=±1,±1/2 for the corresponding wave functions are derived. The most favorable of the four considered spin configurations happened to be the triplet-triplet spin structure of two electrons and of two holes. In its frame a metastable bound state with activation barrier comparable with two ionization potentials of the magnetoexciton is revealed.

  • 15. Promnimit, S.
    et al.
    Cavelius, C.
    Mathur, S.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Growth of gold/zinc sulphide multilayer films using layer-by-layer assembly of colloidal nanoparticles2008In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 41, no 2, p. 285-291Article in journal (Refereed)
    Abstract [en]

    Fabrication of multilayer thin films through layer-by-layer (lbl) deposition of charged nanoparticles on tin-doped indium oxide (ITO) coated and uncoated glass substrates are reported. The thin films were constructed by alternately dipping a substrate into a colloidal suspension of chitosan capped zinc sulphide (ZnS) nanoparticles (∼30 nm) and citrate stabilized colloidal gold (Au) nanoparticles (∼20 nm) leading to electrostatic interactions between the oppositely charged nanoparticle layers. Thin films consisting of up to 200 deposition cycles by multiple dipping have been studied and surface morphology, changes in the optical absorption characteristics, thickness, uniformity, roughness and electrical characteristics are reported. The multilayered assemblies, attached to the surface by strong ionic bonds, were highly stable and could not be removed by moderate scratching. The current-voltage characteristics in the forward and reverse bias conditions demonstrated rectifying behaviors in the onset of conduction voltage which makes these films attractive for future electronic devices

  • 16.
    Siegert, Jörg
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Gaarder, Andreas
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Marcinkevičius, Saulius
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Leon, Rosa
    Chaparro, S.
    Johnson, S.R.
    Sadofyev, Y.
    Zhang, Y.H.
    Photoexcited carrier dynamics in aligned InAs/GaAs quantum dots grown on strain-relaxed InGaAs layers2003In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 18, no 4, p. 541-Article in journal (Refereed)
    Abstract [en]

    Carrier dynamics in aligned InAs/GaAs quantum dots (QDs) grown on cross-batched patterns induced by metastable InxGa1-xAs layers have been studied by time-resolved photoluminescence. The low-temperature carrier lifetimes were found to be of the order of 100-200 ps and determined by carrier trapping and nonradiative recombination. Comparisons with control "nonaligned" InAs QDs show remarkable differences in dependence of peak PL intensities on excitation power, and in PL decay times dependences on both temperature and excitation intensities. Possible origin of traps, which determine the carrier lifetimes, is discussed.

  • 17. Wu, Yanrui
    et al.
    Chen, Xiaoshuang
    Zeng, Yong
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Lu, Wei
    Light coupling for single-mode photonic crystal waveguides2006In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 35, no 1, p. 93-98Article in journal (Refereed)
    Abstract [en]

    We use a transfer-matrix method (TMM) to investigate light coupling into and out of single-end single-mode photonic crystal waveguides. Without multi-reflection complexity, we give clearly the unambiguous quantitative determination of the coupling efficiency of external light into guided mode and the transition among guided modes. It is shown that the waveguide with a line defect along Gamma J direction exhibits a much better coupling efficiency than that with a line-defect orientation along Gamma M direction.

1 - 17 of 17
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