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  • 101.
    Goobar, E.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Gillner, L.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Broberg, B.
    Tanbun-Ek, T.
    Nilsson, S.
    Measurement of a VPE-transported DFB laser with blue-shifted frequency modulation response from DC to 2 GHz1988Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 24, s. 746-747Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The frequency modulation characteristics of a VPE-transported 1.53 mu;m wavelength GaInAsP-InP DFB semiconductor diode laser was measured. Below approximately 0.7 mW optical output power per facet, it exhibited a smooth, blue-shifted, frequency modulation response from DC to 2 GHz. In the modulation frequency range of 10 MHz to 100 MHz it exhibited a | Delta;f/ Delta;I| of 0.5-1.8 GHz/mA, depending on the biasing level

  • 102.
    Goobar, E.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Broadband measurements of frequency noise spectrum in two section DBR laser1991Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 27, s. 289-291Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dependence of the frequency noise on the output power, the tuning current and the current modulation has been measured in a two electrode DBR laser from 30 MHz to 8 GHz. The frequency noise spectrum was fairly flat and decreased with increased output power at a rate faster than 1/P. At certain biasing levels, the noise increased and the relaxation peak was shifted towards lower frequencies when current was injected into the passive waveguide. Furthermore, the frequency noise was not affected by the current modulation.

  • 103.
    Goobar, E.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Broberg, B.
    Nilsson, S.
    Pure frequency modulation or intensity modulation with suppressed frequency chirp using active Bragg reflector integrated laser1989Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 25, s. 304-305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The modulation properties of a laser structure which consists of an active Bragg reflector (300 mu m) integrated with an uncorrugated gain region (600 mu m) have been measured. The laser exhibited a flat FM response and very low spurious intensity modulation when modulating the current in the Bragg reflector. Furthermore, broadband intensity modulation with suppressed frequency chirp could also be achieved. An inhomogeneous linewidth enhancement factor alpha caused by the uneven carrier density distribution between the two sections gives a qualitative explanation to our results.

  • 104.
    Goobar, Edgard
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Rigole, P.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Cross-correlation measurements of intensity noise from the two facets of DFB lasers during linewidth rebroadening1992Inngår i: Semiconductor Laser Conference , 1992. Conference Digest. 13th IEEE International, 1992, s. 266-267Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Not available

  • 105.
    Goobar, Edgard
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Possibilities of large modulation bandwidth of a directly frequency modulated laser with suppressed intensity modulation1989Inngår i: Proceedings of 15th European Conference of Optical Communication, 1989Konferansepaper (Fagfellevurdert)
  • 106.
    Grishin, Alexander
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Khartsev, Sergey
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Dzibrou, Dzmitry
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Enhanced photoluminescence in [Er2O3/TiO2]m photonic crystals2009Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 105, nr 11, s. 113122-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We survey optical properties of [Er2O3/TiO 2]6/Er2O32/[TiO 2/Er2O3]6 photonic crystals (PCs) pulsed laser deposited on to the glass substrates. The dispersion relations of refractive indexes and extinction coefficients of the constituent materials were obtained from the comparison of experimental and simulated transmission spectra of single layer Er2O3 and TiO2 reference films. Based on these data several PCs have been designed and grown to match stop band and cavity mode resonance at wavelengths close to the 523 nm Er 3+-ion Fraunhofer 4S3/2 absorption line. Precise control of chemical composition and uniform multilayer thickness enable achievement of superior optical performance of sintered PCs. Obtained dispersion relations were combined with the 2×2 transfer matrix formalism to compute PC transmittance that appeared to be in a good agreement with the experimental spectra. Pumping PCs with 514 nm light source we observed a strong photoluminescence (PL) at 1535 nm. In PC specially designed for the resonance wavelength λres =514 nm, C-band PL intensity experiences fivefold enhancement compared to a single layer Er2 O3 film of equivalent thickness.

  • 107.
    Grishin, Alexander
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Khartsev, Sergiy
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    All-garnet magneto-optical photonic crystals2008Inngår i: Journal of the Magnetics Society of Japan, ISSN 1882-2924, Vol. 32, nr 2, s. 140-145Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We survey the properties of all-garnet magneto-optical (MO) heteroepitaxial film structures grown by pulsed laser deposition and rf-magnetron sputtering. 1D MO-photonic crystals (MOPCs) were composed of /4 garnet layers alternating highly gyrotropic B13Fe5O12 (BIG) and MO-passive rare earth gallium garnets. As designed, MOPCs' spectra exhibit optical stop band with the transmittance central peak caused by light localization in /2 thick BIG cavity. The first all-garnet BIG/YIG MOPC showed 140% enhancement of the Faraday rotation (FR) compared to a single layer BIG film [APL 84, 1438 (2004)]. Further improvement of MO-performance has been achieved due to the replacement of optically dense YIG by transparent Gd- (GGG), Sm- and novel La-Ga-garnets [APL 86, 141108 (2005); 87, 122504 (2005); 90, 191113 (2007); JAP 101, 053906 (2007)]. At the resonance wavelengths 750 (980) nm, specific FR F=-20.5 (-7.3) deg/m and MO-quality factor Q = 2 |F| /absorption = 66 (43.6) deg represent the highest MOPC performance achieved so far. Respectively, this is 470 (810) % and 31 (190)% enhancement compared to a single layer BIG. MO-remanence (latching capability) has been engineered in the series of BIG:GGG(n:m) superlattices. Regular alternating of lattice mismatched garnet layers impedes the nucleation of misfit dislocations, preserves a long range coherent compressive strain through the whole multilayer thickness thus results in a strong uniaxial magnetic anisotropy. 2.5 m thick BIG:GGG(3:2) film at 678 nm shows FR=1.4 deg, transmittance 82%, 92% squareness of magnetization loop, saturation and coercive fields as low as 56 and 25 Oe, respectively. Nanostructured garnets were used to build MO-visualizer and current driven MO-display [APL 88, 242504 (2006)].

  • 108.
    Grishin, Michael A.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Månsson, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Tjernberg, Oscar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Karlsson, Henrik S.
    Optillion AB, Stockholm.
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Anisotropy of electron structure at InAs(111) surfaces by laser pump-and-probe photoemission spectroscopy2005Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 574, nr 1, s. 89-94Artikkel i tidsskrift (Fagfellevurdert)
    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. (

  • 109. Grivickas, V.
    et al.
    Bikbajevas, V.
    Allakhverdiev, K.
    Linnros, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Two-photon indirect absorption in GaSe2008Inngår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Two-photon absorption (TPA) in GaSe is detected in the narrow (about kT) spectral range above the indirect exciton energy for E⊥c light polarization. The appearance of TPA enhancement within narrow spectral region links to the resonant Raman scattering and anti-Stockes photoluminescence previously identified in GaSe. Extracted TPA coefficient is of the order of 10 cm/W and 5-10 times exceeds ones obtained previously for lower quanta energies.

  • 110. Grivickas, V.
    et al.
    Bikbajevas, V.
    Gavryushin, V.
    Linnros, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Strong photoacoustic pulses generated in TlGaSe2 layered crystals2008Inngår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, 2008, Vol. 100, nr PART 4Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Periodic deflections of infrared probe beam in TlGaSe2 crystal after its lateral excitation by laser pulse with photon energy near the band gap are observed. Such deflections arise from travelling of the acoustic pulse within sample which, in turn, is produced by optical pump pulse through photoacoustic effect. The photoacoustic pulse is generated within thin region near the crystal excited face, much shorter then the light penetration depth. In the case of volume excitation photoacoustic pulse is also generated in the region near back face as well. Tentative explanation of the generation mechanism is discussed.

  • 111. Grivickas, Vytautas
    et al.
    Bikbajevas, Vitalijus
    Gulbinas, Karolis
    Gavryushin, Vladimir
    Linnros, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Strong photoacoustic oscillations in layered TlGaSe2 semiconductor2007Inngår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 244, nr 12, s. 4624-4628Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Periodic deflections of infrared probe are observed in TlGaSe2 after lateral excitation with optical pulse. The effect is explained by generation of photoacoustic dilatational wave, which propagates within the crystal. Low pulse fluence (0.01 mJ/cm(2)) is needed to induce such wave when the layer plane is excited. Acoustic wave is generated within a mu m-distance near the excited face, much shorter then the light penetration depth, 1/alpha, where alpha is the absorption coefficient. In the temperature range 105-120 K, where ferroelectric-paraelectric phase transition occur in TlGaSe2, discontinuous changes of the longitudinal sound velocity have been detected.

  • 112.
    Gudmundsson, Valur
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Hellström, Per-Erik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zhang, Shi-Li
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Direct measurement of sidewall roughness on Si, poly-Si and poly-SiGe by AFM2008Inngår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY / [ed] Johansson LSO, Andersen JN, Gothelid M, Helmersson U, Montelius L, Rubel M, Setina J, Wernersson LE, Bristol: IOP PUBLISHING LTD , 2008, Vol. 100Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper the effect of the commonly used HBr/Cl-2 chemistry for dry etching on the line-edge roughness (LER) of photoresist patterned single crystalline Si (sc-Si), polycrystalline Si (poly-Si) and poly-Si0.2Ge0.8 sidewalls was characterized. Measurements were done by means of atomic force microscopy in combination with an elaborated sample preparation technique that allowed the LER at different depths of the sidewall to be measured. Samples were patterned by I-line lithography and etching was performed at an RF power of 200 W using HBr/Cl-2 (30/10 sccm) plasma. For sc-Si the photoresist and Si sidewalls had an LER of 0.8-1.4 nm and 1.5-2 nm, respectively. For poly-Si and poly-SiGe the photoresist sidewall roughness was, respectively, increased to 1.5-3 nm and 2-3.5 nm due to light scattering from the rough surface of the polycrystalline materials. The poly-Si film had a sidewall roughness of 3-4 nm. Poly-SiGe sidewall exhibited larger roughness with an LER of 5-12 nm which was not transferred from the photoresist. The results show that for sc-Si and poly-Si the sidewall roughness mainly originates from the photoresist process and little additional roughening is caused by the HBr/Cl-2 etching. However, for poly-Si0.2Ge0.8 the LER is considerably increased from that of the photoresist indicating that the HBr/Cl-2 etching is the main contributor to the LER.

  • 113.
    Gustafsson, Oscar
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Höglund, L.
    Berggren, Jespe
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Hammar, Mattias
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    GaSb/Ga0.51In0.49P self assembled quantum dots grown by MOVPE2009Inngår i: Proceedings from EW-MOVPE XIII, 2009, Vol. 7298, s. 273-276Konferansepaper (Fagfellevurdert)
  • 114. Gvozdic, D. M.
    et al.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Efficient switching of Rashba spin splitting in wide modulation-doped quantum wells2007Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The authors demonstrate that the size of the electric-field-induced Rashba spin splitting in an 80 nm wide modulation-doped InGaSb quantum well can depend strongly on the spatial variation of the electric field. In a slightly asymmetric quantum well it can be an order of magnitude stronger than for the average uniform electric field. For even smaller asymmetry spin subbands can have wave functions and/or expectation values of the spin direction that are completely changed as the in-plane wave vector varies. The Dresselhaus effect [Phys. Rev. 100, 580 (1955)] can give an anticrossing at which the spin rapidly flips.

  • 115. Gvozdic, D. M.
    et al.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Superefficient electric-field-induced spin-orbit splitting in strained p-type quantum wells2006Inngår i: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 73, nr 6, s. 927-933Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate theoretically the efficiency of the Rashba effect, i.e. the spin-orbit splitting resulting from an electric field. In contrast to previous studies, where the carriers have usually been taken to be electrons, we focus on holes and are able to demonstrate remarkable improvements of the effect by several orders of magnitude. We also show that the frequently-neglected lattice-mismatch between GaAs and AlGaAs can be used to further enhance the efficiency of the wave vector splitting mechanism. The Rashba effect is the fundamental mechanism behind the Datta-Das spin transistor and we find that for a small electric field of 2 kV/cm the spin precession length becomes only 36nm.

  • 116. Gvozdic, D. M.
    et al.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Superiority of p-type spin transistors2006Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T126, s. 21-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The spintronic device that has probably stimulated the most research interest is the Datta-Das spin transistor. The mechanism behind it, called the Rashba effect, is that an applied voltage gives rise to a spin splitting. We demonstrate that the relevant spin splitting in k-space can be made more than three orders of magnitude larger for holes than for electrons at the same electric field. This is partly achieved by utilizing the frequently neglected lattice-mismatch between GaAs and AlGaAs. We design heterostructures where this efficient Rashba effect should show up. Compared to present transistors, we conclude that electron-based spin transistors will have problems in becoming competitive but hole-based ones are much more promising.

  • 117. Gvozdic, D. M.
    et al.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik.
    Comparison of performance of n- and p-type spin transistors with conventional transistors2005Inngår i: Journal of Superconductivity, ISSN 0896-1107, E-ISSN 1572-9605, Vol. 18, nr 3, s. 349-356Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A spintronic device that has stimulated much research interest is the Datta-Das spin transistor. The mechanism behind it called the Rashba effect is that an applied voltage gives rise to a spin splitting. We propose ways to optimize this effect. The relevant spin splitting in k-space is predicted to increase with electric field at a rate that is more than two orders of magnitude larger for holes than for electrons. Furthermore, the almost negligible lattice-mismatch between GaAs and AlGaAs can be used to further enhance the advantage of hole-based spin transistors. Compared to present transistors we conclude that electron-based spin transistors will have problems to become competitive but hole-based ones are much more promising.

  • 118.
    Gvozdic, Dejan M.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Beyond the Rashba model2006Inngår i: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 32, nr 02-jan, s. 458-461Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 119.
    Gvozdic, Dejan M.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Investigation of the super-efficient Rashba effect by simulation of Shubnikov-de Haas oscillations in a two-dimensional hole gas2006Inngår i: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 34, nr 02-jan, s. 377-380Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 120.
    Göthelid, Mats
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Palmgren, Pål
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Yu, S.
    Agnarsson, B.
    Önsten, A.
    Månsson, M.
    Brena, B.
    Charge transfer and band alignment at the InSb(111)B-TiOPc interfaceManuskript (Annet vitenskapelig)
  • 121.
    Göthelid, Mats
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    von Schenck, Henrik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Weissenrieder, Jonas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åkermark, B.
    Tkatchenko, A.
    Galvan, M.
    Adsorption site, core level shifts and charge transfer on the Pd(111)-I(root 3 x root 3) surface2006Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 600, nr 15, s. 3093-3098Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use core level photoelectron spectroscopy and density functional theory (DFT) to investigate the iodine-induced Pd(1 1 1)-I(root 3 x root 3) structure formed at 1/3 NIL coverage. From the calculations we find that iodine adsorbs preferentially in the fcc hollow site. The calculated equilibrium distance is 2.06 angstrom and the adsorption energy is 68 kcal/mol, compared to 2.45 angstrom and 54 kcal/mol in the atop position. The adsorption energy difference between fcc and hcp hollows is 1.7 kcal/mol. Calculated Pd 3d surface core level shift on clean Pd(1 1 1) is 0.30 eV to lower binding energy, in excellent agreement with our experimental findings (0.28-0.29 eV). On the Pd(1 1 1)-I(root 3 x root 3) we find no Pd 3d surface core level shift, neither experimentally nor, theoretically. Calculated charge transfer for the fcc site, determined from the Hirshfeld partitioning method, suggests that the iodine atom remains almost neutral upon adsorption.

  • 122. Hakkarainen, T.
    et al.
    Setala, T.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Near-field imaging of interacting nano objects with metal and metamaterial superlenses2012Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, s. 043019-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Employing rigorous electromagnetic theory we investigate optical the near-field imaging of two interacting dipole-like objects with metal and slightly lossy metamaterial nanoslab superlenses. Our analysis indicates that the dipole emission is suppressed by near-field interactions when the objects are close to the lens or each other. This strongly influences the image quality, in particular with objects of small size and high polarizability. The interference from two nearby objects also affects the resolution and subwavelength definition can only be obtained for objects with dipole moments predominantly orthogonal to the slab. Such an optimal imaging condition is achieved with excitation by total internal reflection. With simulations we show that in these circumstances, subwavelength resolutions of about lambda/5 for silver superlens and lambda/10 for metamaterial slab are reached.

  • 123. Hakkarainen, T.
    et al.
    Setälä, T.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Imaging of interacting nano-objects with superlenses2012Inngår i: Biomedical Optics, BIOMED 2012, Optical Society of America, 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Employing rigorous electromagnetic theory we show that near-field imaging of point-like objects with subwavelength resolution is achieveable with nanoslab superlenses. For a metallic lens the resolution is »λ/5, whereas for a metamaterial lens λ/10 is obtained. We also illustrate how the near-field interactions among the objects and the lens affect the imaging.

  • 124. Hakkarainen, Timo
    et al.
    Setala, Tero
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Electromagnetic near-field interactions of a dipolar emitter with metal and metamaterial nanoslabs2011Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 84, nr 3, s. 033849-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the emission properties of a polarizable point dipole placed within a subwavelength distance from a silver or a slightly absorbing, negative-index metamaterial nanoslab. Using electromagnetic theory we show that in the immediate vicinity of the slab the dipole-slab interaction prevents the dipole from radiating. For the metamaterial slab close to the perfect-lens arrangement, the interaction is relatively weak and of short range. In particular, a region exists in the near zone of the metamaterial slab where the dipole emission is not disturbed by the interaction, and a bright intensity distribution of subwavelength width is created on the opposite side of the slab. This suggests that a low-loss metamaterial slab can act as a near-field imaging device which does not disturb the object. For the silver slab the interaction is stronger and it reaches over the near-field zone, adversely influencing the imaging capabilities in terms of brightness and resolution. The results are important for the development of metal and metamaterial superlenses.

  • 125.
    Hallén, Anders
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Nawaz, Muhammad
    Zaring, Carina
    Usman, Muhammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Low-Temperature Annealing of Radiation-Induced Degradation in 4H-SiC Bipolar Junction Transistors2010Inngår i: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 31, nr 7, s. 707-709Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radiation hardness is tested for 4H-SiC n-p-n bipolar junction transistors designed for 1200-V breakdown voltage by implanting MeV protons and carbon ions at different doses and energies. The current gain is found to be a very sensitive parameter, and a fluence as low as 1 x 107 cm(-2) of 10 MeV C-12 can be clearly detected in the forward-output characteristics, I-C(V-CE). At this low dose, no influence of ion radiation is seen in the open-collector characteristics, I-B(V-EB), or the reverse bias leakage and breakdown properties. Moreover, by annealing the implanted devices at 420 degrees C for 30 min, a complete recovery of the electrical characteristics is accomplished.

  • 126.
    Hao, Jiaming
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Ren, Qijun
    An, Zhenghua
    Huang, Xueqin
    Chen, Zhanghai
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zhou, Lei
    Optical metamaterial for polarization control2009Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 80, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the design, characterization, and modeling of a specific optical metamaterial, and employ it to manipulate the light polarizations at optical frequencies. Experimental results reveal that the maximum polarization conversion efficiency, i.e., the energy portion converted from s to p polarization after reflection, can be as high as 96% at the wavelength of similar to 685 nm. Simulations and analytical results, which are in reasonable agreements with the experimental results, reveal that the underlying physics are governed by the particular electric and magnetic resonances in the optical metamaterial.

  • 127.
    Hao, Jiaming
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Ren, Qijun
    An, Zhenghua
    Yuan, Yu
    Ran, Lixin
    Chen, Zhanghai
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zhou, Lei
    Manipulate light polarizations by metamaterials: From microwave to optics2008Inngår i: PROCEEDINGS OF THE 2008 INTERNATIONAL WORKSHOP ON METAMATERIALS / [ed] Cui T.J., Smith D.R., NEW YORK: IEEE , 2008, s. 89-89Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recently, artificially designed metamaterials have become of considerable interests, because they exhibit extraordinary optical characteristics that do not exist in nature and promise many potential applications, such as negative refraction, subwavelength imaging, and electromagnetic invisibility cloaking. Although creating metamaterials at the optical frequency range faces numerous technological challenges, such materials with particular properties have been realized gradually based on new device concepts. In this talk, we present our efforts to employ specific metamaterials to manipulate the polarization states of incident lights, in both microwave [1, 2] and optical frequency regimes [3]. Experimental results reveal that the maximum polarization conversion ratio (PGR) value can reach 100% in microwave regime (see left figure below) and 92% in optical frequency (see right figure blow) under certain conditions. Theoretical studies combined with numerical simulations show that the governing physics is dominated by the unique reflection properties of the metamaterials

  • 128.
    Hao, Jiaming
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik.
    Yan, Wei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Super-reflection and cloaking based on zero index metamaterial2010Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, nr 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A zero index metamaterial (ZIM) can be utilized to block wave (super-reflection) or conceal objects completely (cloaking). The "super-reflection" device can be realized by a Mu zero (Epsilon zero) metamaterial with a perfect electric (magnetic) conductor inclusion of arbitrary shape and size for a transverse electric (magnetic) incident wave. In contrast, a Mu zero (Epsilon zero) metamaterial with a perfect magnetic (electric) conductor inclusion for a transverse electric (magnetic) incident wave can be used to conceal objects of arbitrary shape. The underlying physics here is determined by the intrinsic properties of the ZIM.

  • 129. Hassinen, T.
    et al.
    Tervo, J.
    Setälä, T.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Electromagnetic Hanbury Brown-Twiss phenomenon2011Inngår i: Proc SPIE Int Soc Opt Eng, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We analyze the classic Hanbury Brown-Twiss effect for thermal electromagnetic fields in space-frequency domain. We compare two different approaches and show that the normalized correlation of intensity fluctuations is fully characterized by the spectral electromagnetic degree of coherence, a result analogous to scalar analysis of the effect. Differences between the two approaches are discussed.

  • 130. He, Zeming
    et al.
    Stiewe, Christian
    Platzek, Dieter
    Karpinski, Gabriele
    Mueller, Eckhard
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Effect of ceramic dispersion on thermoelectric properties of nano ZrO2/CoSb3 composites2007Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 4, s. 043707-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, nano- ZrO2 CoSb3 composites were fabricated by milling ZrO2 and CoSb3 powders and hot pressing at different sintering temperatures. For the prepared compacts, the phase purity, microstructure, and temperature-dependent thermoelectric properties were characterized. The effect of nano- ZrO2 dispersion on composite electrical conductivity and thermal conductivity is strictly clarified by comparing the transport properties of the nondispersed and dispersed CoSb3 at identical porosity, so that the effect of porosity on thermoelectric parameters could be eliminated. The effect of the insulating inclusion itself on transport properties is also considered and eliminated using effective media theories. It is clearly verified that charge carrier scattering and phonon scattering occur simultaneously to lower the electrical conductivity and the thermal conductivity of CoSb3 due to the introduction of nano- ZrO2 inclusions. The investigated composites show higher electrical conductivity due to existence of metallic Sb and lower thermal conductivity because of nanodispersion. At the ranges of high measuring temperature (673-723 K) and low porosity (6%-9%), the ratio of electrical conductivity to thermal conductivity of the dispersed CoSb3 is higher than that of nondispersed CoSb3, and the dimensionless figure of merit (ZT) of the composite could probably be improved at these ranges with the enhanced ratio of electrical conductivity to thermal conductivity and Seebeck coefficient, which is assumed to be increased by a potential barrier scattering.

  • 131. He, Zeming
    et al.
    Stiewe, Christian
    Platzek, Dieter
    Karpinski, Gabriele
    Mueller, Eckhard
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Nano ZrO2/CoSb3 composites with improved thermoelectric figure of merit2007Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, nr 23, s. 235602-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nano ZrO2/CoSb3 composites with different ZrO 2 contents were prepared using hot pressing. The phase purity, the microstructure and the temperature-dependent transport parameters of the composites were investigated. The dimensionless figure of merit (ZT) of 0.18 of the non-dispersed CoSb3 preponderates the maximal value (0.17) of pure CoSb3 reported in the literature, which is attributed to the prepared sample having higher electrical conductivity due to the existence of a small amount of metallic Sb and lower thermal conductivity due to the fine-grained structure. Compared to non-dispersed CoSb3, a further improvement of 11% on ZT (0.20) was achieved in the composite with 0.05ZrO 2 inclusions, which resulted from the enhanced ratio of electrical conductivity to thermal conductivity and the Seebeck coefficient. The nanodispersion method provides an effective approach to improving a material's thermoelectric properties and performance.

  • 132.
    He, Zeming
    et al.
    Institute of Materials Research, German Aerospace Center (DLR).
    Stiewe, Christian
    Institute of Materials Research, German Aerospace Center (DLR).
    Platzek, Dieter
    Institute of Materials Research, German Aerospace Center (DLR).
    Karpinski, Gabriele
    Institute of Materials Research, German Aerospace Center (DLR).
    Müller, Eckhard
    Institute of Materials Research, German Aerospace Center (DLR).
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Toprak, Muhammet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Thermoelectric properties of hot-pressed skutterudite CoSb32007Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 5, s. 053713-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, skutterudite CoSb3 were fabricated by hot pressing at different sintering temperatures under vacuum and argon. For the prepared compacts, the phase, the microstructure, and the temperature dependent thermoelectric properties were characterized. The correlation of the materials factors: density, grain size, Sb content, with the thermoelectric variables: Seebeck coefficient, electrical conductivity, thermal conductivity, and dimensionless figure of merit (ZT), is presented. The achieved ZT values are also compared with those reported in the literature. The investigated samples show larger electrical conductivity due to existence of metallic Sb and smaller thermal conductivity because of fine-grained structure. A maximal ZT of 0.11 was achieved for the samples sintered at 853 K under vacuum and at 773 K under argon. A moderate improvement on ZT for pure CoSb3 is shown in the present work.

  • 133. Heydari, H.
    et al.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Complex multi-projective variety and entanglement2005Inngår i: Journal of Physics A: Mathematical and General, ISSN 0305-4470, E-ISSN 1361-6447, Vol. 38, nr 14, s. 3203-3211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we will show that a vanishing generalized concurrence of a separable state can be seen as an algebraic variety called the Segre variety. This variety defines a quadric space which gives a geometric picture of separable states. For pure, bi- and three-partite states the variety equals the generalized concurrence. Moreover, we generalize the Segre variety to a general multipartite state by relating to a quadric space defined by two-by-two subdeterminants.

  • 134. Heydari, Hoshang
    et al.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Concurrence and the Schwarz inequality2006Inngår i: Quantum information & computation, ISSN 1533-7146, Vol. 6, nr 05-apr, s. 455-460Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that generalized concurrence is closely related to, and can be derived from, the Schwarz inequality. This connection places concurrence in a geometrical and functional-analytical setting.

  • 135.
    Heydari, Hoshang
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Entanglement tensor for a general pure multipartite quantum state2005Inngår i: Quantum information & computation, ISSN 1533-7146, Vol. 5, nr 2, s. 146-155Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose an entanglement tensor to quantitatively compute the entanglement of a general pure multipartite quantum state. We compare the ensuing tensor with the concurrence for bipartite state and apply the tensor measure to some interesting examples of entangled three-qubit and four-qubit states. It is shown that in defining the degree of entanglement of a multi-partite state, one needs to make assumptions about the willingness of the parties to cooperate. For such states our tensor becomes a measure of generalized entanglement of assistance. We also discuss the degree of entanglement and the concurrence of assistance of two generic multi-qubit states.

  • 136.
    Holmström, Petter
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Electroabsorption modulator using intersubband transitions in GaN-AlGaN-AlN step quantum wells2006Inngår i: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 42, nr 7-8, s. 810-819Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We calculate the high-speed modulation properties of an electroabsorption modulator for lambda = 1.55 mu m based on Stark shifting an intersubband resonance in GaN-AlGaN-AlN step quantum wells. In a realistic simulation assuming an absorption linewidth Gamma = 100 meV we obtain an RC-limited electrical f(3dB) similar to 60 GHz at an applied voltage swing V-pp = 2.8 V. We also show that a small negative effective chirp parameter suitable for standard single-mode fiber is obtained and that the absorption is virtually unsaturable. The waveguide is proposed to be based on the plasma effect in order to simultaneously achieve a strong confinement of the optical mode, a low series resistance, and lattice-matched cladding and core waveguide layers. Extrapolated results reflecting the decisive dependence of the high-speed performance on the intersubband absorption linewidth Gamma are also given. At the assumed linewidth the modulation speed versus signal power ratio is on a par with existing lumped interband modulators based on the quantum confined Stark effect.

  • 137.
    Holmström, Petter
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Jänes, Peter
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Efficient infrared electroabsorption with 1 V applied voltage swing using intersubband transitions2008Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, nr 19, artikkel-id 191101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have demonstrated efficient intersubband electroabsorption in InGaAs/InAlGaAs/InAlAs step quantum wells grown by metal-organic vapor-phase epitaxy. An absorption modulation of 6 dB (Delta alpha=2300 cm(-1)) at lambda similar to 5.7 mu m due to Stark shift of the intersubband resonance was achieved at a low applied voltage swing of +/- 0.5 V in a multipass waveguide structure. The interface intermixing was estimated by comparing experimental and theoretical Stark shifts. It is predicted that the present material in a strongly confining surface plasmon waveguide can yield an electroabsorption modulator with a peak-to-peak voltage of V-pp=0.9 V and modulation speed of f(3dB)approximate to 130 GHz.

  • 138.
    Holmström, Petter
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Jänes, Peter
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Strong electroabsorption using intersubb and transitions in InGaAs/InAlGaAs/InAlAs step quantum wells2006Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Artikkel i tidsskrift (Annet vitenskapelig)
  • 139.
    Holmström, Petter
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Liu, X. Y.
    Uchida, H.
    Aggerstam, Thomas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Kikuchi, A.
    Kishino, K.
    Lourdudoss, Sebastian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Andersson, T.G.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Intersubband photonic devices by group-III nitrides2007Inngår i: Optoelectronic Materials And Devices II / [ed] Nakano, Y, 2007, Vol. 6782, s. N7821-N7821Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The characteristics of intersubband transitions in III-nitride quantum wells are promising for detectors and all-optical switches through a high intrinsic speed (similar to 1 THz), and can also provide a high optical saturation power and a desired small negative chirp parameter in electroabsorption modulators. The high LO-phonon energy allows to improve the operating temperature of THz emitters. Recent achievements and prospects for intersubband III-nitride photonic devices, mainly for lambda=1.55 mu m, are briefly reviewed. Further, means to enhance material quality by achieving crack-free growth of GaN/AlN multiple-quantum-well (MQW) structures, and by employing intersubband transitions in multiple-quantum-disk (MQD) structures incorporated into dislocation free GaN nanocolumns are discussed. We investigate the occurrence of cracks in MBE-grown GaN/AlN MQWs on GaN MOVPE templates with respect to the buffer layer, the number of QWs and the temperature reduction rate after growth. Intersubband absorption in GaN/AlN MQDs in the wavelength range 1.38-1.72 mu m is demonstrated in three samples grown on Si(111).

  • 140.
    Holmström, Petter
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Matsui, Satoshi
    Sophia University.
    Uchida, Hiroyuki
    Sophia University.
    Nakazato, Takuya
    Sophia University.
    Jänes, Peter
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Aggerstam, Tomas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Kikuchi, Akihiko
    Sophia University.
    Kishino, Katsumi
    Sophia University.
    Electroabsorption modulator based on intersubband transitions in (Al)(Ga)N step quantum wells considering intermixing2005Konferansepaper (Fagfellevurdert)
  • 141.
    Hu, Xin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Zhang, Qiali
    Lin, Zhili
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Equivalent Circuit of Complementary Split-Ring Resonator Loaded Transmission Line2009Inngår i: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 51, nr 10, s. 2432-2434Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this article, a circuit model is proposed for the complementary split-ring resonators (CSRRs) loaded transmission line, and comparisons between the results derived from the equivalent circuit model and the experimental results are given and a good agreement between them over a wide frequency band supports the effectiveness of F the proposed modeling methodology. Both the results show the negative f permittivity at the vicinity of the resonance frequency of CSRR. By comparing the results of different periodic length (i.e., the capacitance per-unit-cell of the host microstrip line is changed), the validity of the equivalent circuit is further confirmed.

  • 142.
    Hållstedt, Julius
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Integration of epitaxial SiGe(C) layers in advanced CMOS devices2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Heteroepitaxial SiGe(C) layers have attracted immense attention as a material for performance boost in state of the art electronic devices during recent years. Alloying silicon with germanium and carbon add exclusive opportunities for strain and bandgap engineering. This work presents details of epitaxial growth using chemical vapor deposition (CVD), material characterization and integration of SiGeC layers in MOS devices.

    Non-selective and selective epitaxial growth of Si1-x-yGexCy (0≤x≤0.30, 0≤y≤0.02) layers have been performed and optimized aimed for various metal oxide semiconductor field effect transistor (MOSFET) applications. A comprehensive experimental study was performed to investigate the growth of SiGeC layers. The incorporation of C into the SiGe matrix was shown to be strongly sensitive to the growth parameters. As a consequence, a much smaller epitaxial process window compared to SiGe epitaxy was obtained.

    Incorporation of high boron concentrations (up to 1×1021 atoms/cm3) in SiGe layers aimed for recessed and/or elevated source/drain (S/D) junctions in pMOSFETs was also studied. HCl was used as Si etchant in the CVD reactor to create the recesses which was followed (in a single run) by selective epitaxy of B-doped SiGe.

    The issue of pattern dependency behavior of selective epitaxial growth was studied in detail. It was shown that a complete removal of pattern dependency in selective SiGe growth using reduced pressure CVD is not likely. However, it was shown that the pattern dependency can be predicted since it is highly dependent on the local Si coverage of the substrate. The pattern dependency was most sensitive for Si coverage in the range 1-10%. In this range drastic changes in growth rate and composition was observed. The pattern dependency was explained by gas depletion inside the low velocity boundary layer.

    Ni silicide is commonly used to reduce access resistance in S/D and gate areas of MOSFET devices. Therefore, the effect of carbon and germanium on the formation of NiSiGe(C) was studied. An improved thermal stability of Ni silicide was obtained when C is present in the SiGe layer.

    Integration of SiGe(C) layers in various MOSFET devices was performed. In order to perform a relevant device research the dimensions of the investigated devices have to be in-line with the current technology nodes. A robust spacer gate technology was developed which enabled stable processing of transistors with gate lengths down to 45 nm.

    SiGe(C) channels in ultra thin body (UTB) silicon on insulator (SOI) MOSFETs, with excellent performance down to 100 nm gate length was demonstrated. The integration of C in the channel of a MOSFET is interesting for future generations of ultra scaled devices where issues such as short channel effects (SCE), temperature budget, dopant diffusion and mobility will be extremely critical. A clear performance enhancement was obtained for both SiGe and SiGeC channels, which point out the potential of SiGe or SiGeC materials for UTB SOI devices.

    Biaxially strained-Si (sSi) on SiGe virtual substrates (VS) as mobility boosters in nMOSFETs with gate length down to 80 nm was demonstrated. This concept was thoroughly investigated in terms of performance and leakage of the devices. In-situ doping of the relaxed SiGe was shown to be superior over implantation to suppress the junction leakage. A high channel doping could effectively suppress the source to drain leakage.

  • 143.
    Hållstedt, Julius
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    von Haartman, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Hellström, Per-Erik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Radamson, Henry
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Hole mobility in ultrathin body SOI pMOSFETs with SiGe or SiGeC channels2006Inngår i: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 27, nr 6, s. 466-468Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hole mobilities of SiGe and SiGeC channel pMOSFETs fabricated on ultrathin silicon-on-insulator substrates are investigated and compared with reference Si channel devices. The total thickness of the fully depleted Si/SiGe(C)/Si body structure is similar to 25 nm. All devices demonstrated a near ideal subthreshold behavior, and the drive current and mobility were increased with more than 60% for SiGe and SiGeC channels. When comparing SIMOX and UNIBOND substrates, no significant difference could be detected.

  • 144. Iacocca, Ezio
    et al.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Analytical investigation of modulated spin-torque oscillators in the framework of coupled differential equations with variable coefficients2012Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, nr 18, s. 184420-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modulation of spin torque oscillators (STOs) is investigated by analytically solving the time-dependent coupled equations of an auto-oscillator. A Fourier-series solution is proposed, leading to the coefficients being determined with a linear set of equations, from which a nonlinear amplitude and frequency modulation (NFAM) scheme is obtained. In this framework, the NFAM features are related to the intrinsic STO parameters, revealing a frequency dependence of the harmonic-dependent modulation index that allows a modulation bandwidth to be defined for these devices. The presented results expose a rich parameter space, where the modulation and the STO's operation conditions define the observed modulation features. The Fourier-series representation of the time signal is suitable for studying periodic perturbations on the auto-oscillator equation.

  • 145. Iacocca, Ezio
    et al.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. University of Gothenburg, Sweden.
    Resonant excitation of injection-locked spin-torque oscillators2013Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, nr 21, s. 214428-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Theory predicts that a strongly injection-locked spin-torque oscillator (STO) should show a characteristic ringing frequency both on its approach to the locked state and under the influence of thermal noise. While experiments have so far failed to detect such ringing, we here show numerically and analytically how current modulation of injection-locked STOs can excite the ringing frequency in a resonant manner, and hence increase the experimental sensitivity. The complexity of such dynamics leads to a nonlinear resonance, which can even unlock the STO as a function of the modulation strength. The results presented here offer a plausible method for experimentally measuring the ringing frequency of STOs. Moreover, the onset of unlocking also provides a measure for the maximum modulation strength that can be applied to phase-locked STOs.

  • 146.
    Innocenti, Nicolas
    KTH, Skolan för datavetenskap och kommunikation (CSC), Beräkningsbiologi, CB. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    What microcavities can do in photonics : coupling resonances and optical gain2009Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The present master's thesis deals with numerical modeling of solid-state micrometrical-sized polymeric dye lasers, commonly denoted as microcavities. It is part of a large research initiative carried out in the optics group, at the MAP (Microelectronics and Applied Physics) department in KTH (Kungliga Tekniska Högskolan - Royal Technical School) and targeted towards the design and manufacturing of micro- and nano-scaled polymeric components for nano-photonics, primarily lasers. The finite element method (FEM) in frequency domain is used as a primary modeling tool through the simulation software COMSOL Multiphysics. Models for spontaneous emission, optical losses and gain are developed and demonstrated. A specic layout is studied: the double hexagonal microcavity. While it was expected to be a good candidate for a laser, the design shows unexpected properties making it useful for sensing applications. Finally, the transposition of models to time domain is initiated : a replacement solution for the lacking perfectly matched layer (PML) in Comsol is developed and demonstrated. Methods for modeling materials parameters in time domain are investigated, together with the possible use of a more suitable algorithm : finite dierences in time domain (FDTD) or Yee's scheme.

  • 147.
    Innocenti, Nicolas
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Sergeyev, Sergey
    Waterford Institute of Technology.
    Friberg, Ari
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    External field enhancement in coupled polymer microcavities - New options for integrated photonic components2009Inngår i: European Conference on Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009, 2009Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Microcavities are key components for integrated optical devices and systems. In this paper, enhancement of the resonance electric field outside a pair of coupled polymeric microcavities of hexagonal shape is investigated. Using numerical simulation, enhancement of outside-cavity field has been demonstrated in different sections of the coupled cavity system depending on particular design. Resonance frequencies are in visible part of electromagnetic spectrum. In reported simulations rigorous models based on solving Maxwell equations for propagating electromagnetic field in polymeric materials commonly used in nano-imprinting lithography is demonstrated.

  • 148.
    Iyer, Srinivasan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Dong, Lin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Physical reason behind far-field transmission resonances from U-shaped metallic structures2010Inngår i: 2010 Asia Communications and Photonics Conference and Exhibition, ACP 2010, 2010, s. 326-327Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The far-field transmission spectrum of crescent-like metallic nanostructures on a glass substrate at normal incidence is studied numerically. The interpretation of transmission resonances arising from a periodic subwavelength U-shaped metal nanostructure in terms of plasmonic eigen modes is revisited.

  • 149.
    Iyer, Srinivasan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Dong, Lin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. Aalto University, Finland .
    Refractive index sensor performance based on enhanced transmission of light through perforated metallic films2010Inngår i: 2010 Asia Communications and Photonics Conference and Exhibition, ACP 2010, 2010, s. 328-329Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The transmission of light through a thin Au film with periodic subwavelength double nanoholes at normal incidence is analyzed numerically and compared to other conventional hole shapes. The performance of such perforated metallic films as a potential refractive index sensor is discussed.

  • 150.
    Iyer, Srinivasan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. Aalto University, Finland.
    Double nanoholes in a metal film as refractive index sensors2010Inngår i: Frontiers in Optics, FiO 2010, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The transmission of light through a thin Au film with subwavelength double nanoholes is modeled using vectorial three-dimensional finite element method. The performance of such perforated films as a potential refractive index sensor is discussed.

1234567 101 - 150 of 615
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