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  • 251.
    Mbairi, Felix D.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Some Aspects of Advanced Technologies and Signal Integrity Issues in High Frequency PCBs, with Emphasis on Planar Transmission Lines and RF/Microwave Filters2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The main focus of this thesis is placed on high frequency PCB signal Integrity Is-sues and RF/Microwave filters using EBG structures.

    From the signal Integrity aspect, two topics were mainly discussed. On one hand, the effect of increasing frequency on classical design rules for crosstalk reduction in PCBs was investigated experimentally and by full-wave simulations. An emphasis was placed on the 3×W spacing rule and the use of guard traces. Single-ended and differential transmission lines were considered. S-parameter measurements and simu-lations were carried out at high-frequency (up to 20 GHz). The results emphasize the necessity to reevaluate traditional design rules for their suitability in high frequency applications. Also, the impacts of using guard traces for high frequency crosstalk re-duction were clearly pointed out. On the other hand, the effect of high loss PCB ma-terials on the signal transmission characteristics of microstrip lines at high frequency (up to 20 GHz) was treated. Comparative studies were carried out on different micro-strip configurations using standard FR4 substrate and a high frequency dielectric ma-terial from Rogers, Corporation. The experimental results highlight the dramatic im-pact of high dielectric loss materials (FR4 and solder mask) and magnetic plating metal (nickel) on the high frequency signal attenuation and loss of microstrip trans-mission lines.

    Besides, the epoxy-based SU8 photoresist was characterized at high frequency (up to 50 GHz) using on-wafer conductor-backed coplanar waveguide transmission lines. A relative dielectric constant of 3.2 was obtained at 30 GHz. Some issues related to the processing of this material, such as cracks, hard-skin, etc, were also discussed.

    Regarding RF/Microwave filters, the concept of Electromagnetic Band Gap (EBG) was used to design and fabricate novel microstrip bandstop filters using periodically modified substrate. The proposed EBG structures, which don’t suffer conductor backing issues, exhibit interesting frequency response characteristics.

    The limitations of modeling and simulation tools in terms of speed and accuracy are also examined in this thesis. Experiments and simulations were carried out show-ing the inadequacies of the Spice diode model for the simulations in power electronics. Also, an Artificial Neural Network (ANN) model was proposed as an alternative and a complement to full-wave solvers, for a quick and sufficiently accurate simulation of interconnects. A software implementation of this model using Matlab’s ANN toolbox was shown to considerably reduce (by over 800 times) the simulation time of microstrip lines using full-wave solvers such as Ansoft’s HFSS and CST’s MWS.

    Finally, a novel cooling structure using a double heatsink for high performance electronics was presented. Methods for optimizing this structure were also discussed.

  • 252.
    Mbairi, Felix D.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Hesselbom, Hjalmar
    Department of Electronic Production, Mid Sweden University, ITM, Campus Östersund.
    Microwave bandstop filters using novel artificial periodic substrate electromagnetic band gap structures2009Inngår i: IEEE transactions on components and packaging technologies (Print), ISSN 1521-3331, E-ISSN 1557-9972, Vol. 32, nr 2, s. 273-282Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Novel microwave and millimeterwave (mm-wave) bandstop filters using artificial periodic substrate electromagnetic bandgap (EBG) are investigated in this paper. Three types of microstrip structures using periodically modified trace width, patterned dielectric substrate, and periodically modified ground plane are treated, respectively. By periodically modifying either the width of the conductor trace, the substrate height, or the dielectric constant of a standard microstrip transmission line, it has been possible to design microwave bandstop filter functions with wide stopband characteristics and reduced size, compared to conventional microwave/RF filter structures. Commercial electronic design automation (EDA) and computational electromagnetic tools such as Agilent's advanced design system (ADS) and CST Microwave Studio are used in the design and simulations of these filter structures. The effects of the physical parameters of the structures on the filter characteristic are studied. The design procedure and simulation results are described and possible applications of these filter structures are discussed in this paper. A particularly wide stopband is achieved by the circuits presented in this paper, which use only a few cell elements. A significant performance improvement of microstrip patch antenna has been observed by implementing one of the presented EBG periodic substrate structures.

  • 253.
    Mbairi, Felix
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Siebert, Peter W.
    Department of Electronic Production, Mid Sweden University, ITM, Östersund.
    Hesselbom, Hjalmar
    Department of Electronic Production, Mid Sweden University, ITM, Östersund.
    High frequency transmission lines crosstalk reduction using spacing rules2008Inngår i: IEEE transactions on components and packaging technologies, ISSN 1521-3331, Vol. 31, nr 3, s. 601-610Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-frequency transmission lines crosstalk reduction using spacing rules is treated in this paper. Two of the most popular planar transmission line configurations, namely microstrip and stripline, commonly used in printed circuit boards and radio frequency/microwave integrated circuits, are considered in this work. The trace separation between two adjacent transmission lines of each type is stepwise increased as function of the trace width. The single-ended transmission line structures are numerically investigated by a frequency-based 3-D full-wave electromagnetic analysis tool. A particular case using coated microstrip transmission lines has been fabricated, along with some calibration structures, to allow direct measurement and experimental analysis of crosstalk between the single-ended transmission lines. The test structures are characterized at high-frequency (up to 20 GHz) with scattering parameters using a vector network analyzer. The experimental results are compared with the simulation data, and some conclusions and suggestions on the impact and use of spacing rules for high-frequency crosstalk reduction between single-ended transmission lines are presented. These investigations emphasize the necessity of reevaluating classical design rules for their suitability in high-frequency applications.

  • 254. McDonald, David
    et al.
    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. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Spano, Paolo
    O’Gorman, James
    Measurement and parameter extraction of semiconductor lasers: experiences of the pan-European action COST 2401998Inngår i: Laser Diodes and Applications III, Vol. 3415, s. 152-163Artikkel i tidsskrift (Fagfellevurdert)
  • 255. Miller, Casey W.
    et al.
    Li, Zhi-Pan
    Schuller, Ivan K.
    Dave, R. W.
    Slaughter, J. M.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Dynamic spin-polarized resonant tunneling in magnetic tunnel junctions2007Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 99, nr 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Precisely engineered tunnel junctions exhibit a long sought effect that occurs when the energy of the electron is comparable to the potential energy of the tunneling barrier. The resistance of metal-insulator-metal tunnel junctions oscillates with an applied voltage when electrons that tunnel directly into the barrier's conduction band interfere upon reflection at the classical turning points: the insulator-metal interface and the dynamic point where the incident electron energy equals the potential barrier inside the insulator. A model of tunneling between free electron bands using the exact solution of the Schrodinger equation for a trapezoidal tunnel barrier qualitatively agrees with experiment.

  • 256. Miller, Casey W.
    et al.
    Li, Zhi-Pan
    Schuller, Ivan K.
    Dave, R. W.
    Slaughter, J. M.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Origin of the breakdown of Wentzel-Kramers-Brillouin-based tunneling models2006Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, nr 21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The tunneling conductance of three varieties of CoFeB/MgO/CoFeB magnetic tunnel junctions depends quadratically on the applied voltage to anomalously high biases. Within the framework traditional of WKB models, this implies unphysical tunnel barrier parameters: heights near 20 eV, or widths corresponding to fewer than two MgO lattice constants. We demonstrate that the failure of such models to yield physically reasonable parameters originates from an experimentally unavoidable distribution of barrier thicknesses, possibly acting synergistically with the band structure of the barrier material. This implies that existing WKB models may lead to physically incorrect barrier parameters for contemporary tunnel junctions, magnetic or otherwise.

  • 257. Miller, Casey W.
    et al.
    Li, Zhi-Pan
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Schuller, Ivan K.
    Impact of interfacial roughness on tunneling conductance and extracted barrier parameters2007Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, nr 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The net tunneling conductance of metal-insulator-metal tunnel junctions is studied using a distribution of barrier thicknesses consistent with interfacial roughness typical of state-of-the-art tunnel junctions. Moderate amounts of roughness cause the conductance to resemble that of much thinner and taller barriers. Fitting numerically generated conductance data that include roughness with models that assume a single-thickness barrier leads to erroneous results for both the barrier height and width. Rules of thumb are given that connect the roughness to the real space mean thickness and the thickness inferred from fitting the net conductance with traditional tunneling models.

  • 258. Miller, Casey W.
    et al.
    Schuller, Ivan K.
    Dave, R. W.
    Slaughter, J. M.
    Zhou, Yan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Temperature and angular dependences of dynamic spin-polarized resonant tunneling in CoFeB/MgO/NiFe junctions2008Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 7, s. 07A904-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The bias dependence of tunneling magnetoresistance oscillations due to dynamic resonant tunneling in CoFeB/MgO/NiFe magnetic tunnel junctions was studied as functions of temperature and the relative magnetization angle of the two magnetic layers. The effect of temperature is consistent with thermal smearing, while that of the relative magnetic orientation was typical of a spin valve. A model of tunneling between spin-split free electron bands using the exact solution of the Schrodinger equation for a trapezoidal tunnel barrier agrees with experiment, underscoring the simplicity of dynamic resonant tunneling.

  • 259.
    Mogg, Sebastian
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Plaine, G.
    Asplund, C.
    Sundgren, P.
    Baskar, K.
    Mulot, M.
    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.
    Hammar, Mattias
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    High-performance 1.2- mu;m highly strained InGaAs/GaAs quantum well lasers2002Inngår i: Indium Phosphide and Related Materials Conference, 2002. IPRM. 14th, 2002, s. 107-110Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The growth and characterisation of high-performance 1.2- mu;m highly strained InGaAs/GaAs single quantum well (SQW) laser diodes is reported. High output power in excess of 200 mW per facet was obtained from ridge-waveguide (RWG) lasers at an emission wavelength of 1230 nm. These lasers operate CW to at least 145 deg;C and show a high characteristic temperature of 150 K. The net modal gain was measured using the method described by Hakki and Paoli (1975).

  • 260. Monakhov, E. V.
    et al.
    Svensson, B. G.
    Linnarsson, Margareta K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    La Magna, A.
    Italia, M.
    Privitera, V.
    Fortunato, G.
    Cuscuna, M.
    Mariucci, L.
    Boron distribution in silicon after excimer laser annealing with multiple pulses2005Inngår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 124, s. 228-231Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied B re-distribution in Si after excimer laser annealing (ELA) with multiple laser pulses. B was implanted using both B and BF2 ions with energies from 1 to 20 keV and doses of 1 x 10(14) and 1 x 10(15) cm(-2). ELA with the number of pulses from 1 to 100 was performed in vacuum with the sample kept at room temperature and 450 degrees C. Independently of the implantation parameters and the ELA conditions used, a peak in the B concentration is observed near the maximum melting depth after 10 pulses of ELA. A detailed study has revealed that B accumulates at the maximum melt depth gradually with the number of ELA pulses. An increase in the carrier concentration at the maximum melt depth is observed after ELA with 100 pulses. No structural defects have been detected by transmission electron microscopy in the region of the B accumulation.

  • 261. Monakhov, E. V.
    et al.
    Svensson, B. G.
    Linnarsson, Margareta K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    La Magna, A.
    Italia, M.
    Privitera, V.
    Fortunato, G.
    Cuscuna, M.
    Mariucci, L.
    Boron distribution in silicon after multiple pulse excimer laser annealing2005Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, nr 8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied B redistribution in Si after excimer laser annealing (ELA) with multiple laser pulses. B was implanted with energies of 1 and 10 keV and doses of 1x10(14) and 1x10(15) cm(-2). ELA with the number of pulses from 1 to 100 was performed at room temperature and 450 degrees C in vacuum. Irrespective of the implantation parameters and the ELA conditions used, a pile-up in the B concentration is observed near the maximum melting depth after ten pulses of ELA. Moreover, a detailed study has revealed that B accumulates at the maximum melt depth gradually with the number of ELA pulses. Besides, an increase in the carrier concentration is observed at the maximum melt depth, suggesting electrical activity of the accumulated B. Formation of Si-B complexes and vacancy accumulation during multiple ELA are discussed as possible mechanisms for the B build-up.

  • 262. Monakhov, E. V.
    et al.
    Svensson, B. G.
    Linnarsson, Margareta K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    La Magna, A.
    Italia, M.
    Privitera, V.
    Fortunato, G.
    Cuscuna, M.
    Mariucci, L.
    Excimer laser annealing of B and BF2 implanted Si2005Inngår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 124, s. 232-234Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have performed a comparative study of B re-distribution and electrical activation after excimer laser annealing (ELA) of B and BF2 implanted Si. Chemical B concentration and electrical activation profiles were measured by secondary ion mass spectrometry (SIMS) and spreading resistance profiling (SRP), respectively. SIMS data demonstrate that the presence of F does not influence significantly the re-distribution of B during ELA. A dramatic contrast, however, can be observed in the electrical activation of the dopant in the B and BF2 implanted samples. While almost 100% electrical activation of B occurs in the B implanted samples, only 20-50% of the dopant can be activated by ELA in the BF2 implanted sample. Possible mechanisms causing the deactivation of B in the BF2 implanted samples after ELA are discussed.

  • 263. Monakhov, E. V.
    et al.
    Svensson, B. G.
    Linnarsson, Margareta K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    La Magna, A.
    Italia, M.
    Privitera, V.
    Fortunato, G.
    Cuscuna, M.
    Mariucci, L.
    The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon2005Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, nr 19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the effect of excimer laser annealing (ELA) on transient enhanced diffusion (TED) and activation of boron implanted in Si during subsequent rapid thermal annealing (RTA). It is observed that ELA with partial melting of the implanted region causes reduction of TED in the region that remains solid during ELA, where the diffusion length of boron is reduced by a factor of similar to 4 as compared to the as-implanted sample. This is attributed to several mechanisms such as liquid-state annealing of a fraction of the implantation induced defects, introduction of excess vacancies during ELA, and solid-state annealing of the defects beyond the maximum melting depth by the heat wave propagating into the Si wafer. The ELA pretreatment provides a substantially improved electrical activation of boron during subsequent RTA.

  • 264. Monakhov, E. V.
    et al.
    Svensson, B. G.
    Linnarsson, Margareta K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    La Magna, A.
    Spinella, C.
    Bongiorno, C.
    Privitera, V.
    Fortunato, G.
    Mariucci, L.
    Enhanced boron diffusion in excimer laser preannealed Si2005Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, nr 15Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated boron diffusion during rapid thermal annealing in Si implanted with boron using an energy of 1 keV and a dose of 1 x 10(16) cm(-2). Two types of samples have been studied: As-implanted and pretreated with excimer laser annealing. For both types an enhanced diffusion of boron has been observed with an enhancement by a factor of 3-5 over the standard diffusion. It is suggested that the high concentration of implanted boron is a dominant factor for the diffusion enhancement as compared to the effect of implantation-induced damage. The data indicate that the proximity of the surface can also affect the boron diffusion enhancement.

  • 265. Morthier, G.
    et al.
    Baets, R.
    Tsang, C. F.
    Caroll, J. E.
    Wenzel, H.
    Mecozzi, A.
    Sapia, A.
    Correc, P.
    Hansmann, S.
    Burkhardt, H.
    Bonello, R.
    Montrosset, I.
    Lassen, H. E.
    Olesen, H.
    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. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Bissessur, H.
    Vey, J-L
    Duan, G.
    Comparison of different DFB laser models within the European COST 240 collaboration1993Inngår i: Integrated Photonics Research (IPR) Palm Springs, California March 22, 1993    Semiconductor Device Modeling 1 (IWB), 1993Konferansepaper (Fagfellevurdert)
  • 266. Morthier, G.
    et al.
    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.
    Kjebon, Olle
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Extended modulation bandwidth of DBR and external cavity lasers by utilizing a cavity resonance for equalization2000Inngår i: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 36, nr 12, s. 1468-1475Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the occurence of a second resonance frequency in distributed Bragg reflector laser diodes and the high modulation bandwidth resulting from it. The influence of different laser parameters has been theoretically investigated. It is also shown that a similar behavior can be obtained in laser diodes with a passive, low-loss, and gratingless external cavity, The possibilities of large-signal digital modulation are also investigated.

  • 267. Morthier, G.
    et al.
    Verhoeve, P.
    Baets, R.
    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.
    Extraction of a large set of laser parameters from different measurements1996Inngår i: Semiconductor Laser Conference, 1996., 15th IEEE International, 1996, s. 175-176Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We show how most of the parameters of a DFB laser can be extracted from a limited number of relatively simple measurements. These measurements include the ASE spectra at different currents below threshold, the RIN spectra above threshold and the P-I relation. We have performed curve-fitting on different characteristics such as the ASE spectrum, the RIN spectrum and the P-I curve. From the ASE spectrum measured in the vicinity of the lasing wavelength we can extract grating parameters, facet phases, refractive index and gain as well as the wavelength and current dependence of the last two parameters

  • 268. Morthier, Geert
    et al.
    Baets, Roel
    TSIGOPOULOS, A
    SPHICOPOULOS, T
    TSANG, CF
    CARROLL, JE
    WENZEL, H
    MECOZZI, A
    SAPIA, A
    CORREC, P
    HANSMANN, S
    BURKHARD, H
    PARADISI, A
    MONTROSSET, I
    OLESEN, H
    LASSEN, HE
    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. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    BISSESSUR, H
    COMPARISON OF DIFFERENT DFB LASER MODELS WITHIN THE EUROPEAN COST-240 COLLABORATION.1994Inngår i: IEE Proceedings - Optoelectronics, ISSN 1350-2433, E-ISSN 1359-7078, Vol. 141, s. 82-88Artikkel i tidsskrift (Fagfellevurdert)
  • 269. Moschetti, G.
    et al.
    Abbasi, M.
    Nilsson, P. -Å
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Desplanque, L.
    Wallart, X.
    Grahn, J.
    True planar InAs/AlSb HEMTs with ion-implantation technique for low-power cryogenic applications2013Inngår i: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 79, s. 268-273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we report the room-temperature and cryogenic properties of true planar 110 nm InAs/AlSb HEMTs fabricated with Ar-ion isolation technology. Device isolation is generally improved and is in particular increased by four orders of magnitude at 6 K compared to 300 K. This results in improved drain current saturation, lower gate leakage current and 23% higher peak transconductance. The RF performance is significantly improved as well, with 47% higher fT (162 GHz) and 72% higher fmax (155 GHz) at the low drain voltage of 0.1 V, compared to room temperature. The overall performance of the fabricated devices shows the suitability of ion implantation for the device isolation at cryogenic temperature. Furthermore, the excellent stability against oxidation and truly planar structure of these devices demonstrate great potential for highly integrated cryogenic millimeter-wave circuits in InAs/AlSb technology with ultra-low power consumption.

  • 270. Moschetti, G.
    et al.
    Nilsson, P. -A
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Desplanque, L.
    Wallart, X.
    Grahn, J.
    Source-drain scaling of ion-implanted InAs/AlSb HEMTs2012Inngår i: Indium Phosphide and Related Materials (IPRM), 2012 International Conference on, IEEE , 2012, s. 57-60Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We report on the lateral scaling of true planar InAs/AlSb high electron mobility transistors (HEMTs) based on ion implantation for device isolation. When reducing the source drain distance, dsd, from 2.5 μm to 1 μm, the HEMTs showed up to 56% higher maximum drain current, 23% higher peak transconductance and T of 185 GHz (+32%). A trade-off in the lateral scaling is needed due to increased gate leakage current and pinch-off degradation for dsd below 1.5 μm. The ability to withstand oxidation of the InAs/AlSb heterostructure makes the planar technology based on ion implantation extremely promising for MMIC integration of InAs/AlSb HEMTs.

  • 271. Moschetti, Giuseppe
    et al.
    Nilsson, Per-Åke
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Desplanque, Ludovic
    Wallart, Xavier
    Grahn, Jan
    Planar InAs/AlSb HEMTs With Ion-Implanted Isolation2012Inngår i: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 33, nr 4, s. 510-512Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fabrication and performance of planar InAs/AlSb high-electron-mobility transistors (HEMTs) based on ion-implantation isolation technology are reported. Ar atoms have been implanted at an energy of 100 keV and with a dose of 2 x 10(15) cm(-2) in order to induce device isolation. The InAs/AlSb HEMT exhibited a maximum drain current of 900 mA/mm, a peak transconductance of 1180 mS/mm, and an f(T)/f(max) ratio of 210 GHz/180 GHz at a low drain bias of 0.3 V. The combination of excellent stability against oxidation with the high device isolation demonstrated by the implantation technique can dramatically improve the suitability of InAs/AlSb HEMTs for high-frequency and ultralow-power MMIC applications.

  • 272.
    Muduli, Pranaba
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Rice, W. C.
    He, L.
    Collins, B. A.
    Chu, Y. S.
    Tsui, F.
    Study of magnetic anisotropy and magnetization reversal using the quadratic magnetooptical effect in epitaxial CoxMnyGez(111) films2009Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 21, nr 29, s. 296005-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Magnetic anisotropy, magnetization reversal and the magnetooptic Kerr effect in CoxMnyGez have been studied over a range of compositions between 0 and 50 at.% of Ge and between 1 and 3 in the Co to Mn atomic ratio, including the Heusler alloy Co2MnGe. A strong quadratic magnetooptic Kerr effect has been observed within a narrow region of composition centered around the Co to Mn atomic ratio of 2, which has been used to probe and quantify the magnetic anisotropy and magnetization reversal of the system. The anisotropy is sixfold with a weak uniaxial component, and it exhibits sensitive dependence on composition, especially on the atomic ratio between Co and Mn. The magnetization reversal process is consistent with the single-domain Stoner-Wohlfarth model.

  • 273.
    Månsson, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Quantum mechanics as "space-time statistical mechanics"?Manuskript (Annet vitenskapelig)
    Abstract [en]

    In this paper we discuss and analyse the idea of trying to see (non-relativistic) quantum mechanics as a ``space-time statistical mechanics'', by using the classical statistical mechanical method on objective microscopic space-time configurations. It is argued that this could perhaps be accomplished by giving up the assumption that the objective ``state'' of a system is independent of a future measurement performed on the system. This idea is then applied in an example of quantum state estimation on a qubit system.

  • 274.
    Månsson, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Quantum State Analysis: Probability theory as logic in Quantum mechanics2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Quantum mechanics is basically a mathematical recipe on how to construct physical models. Historically its origin and main domain of application has been in the microscopic regime, although it strictly seen constitutes a general mathematical framework not limited to this regime. Since it is a statistical theory, the meaning and role of probabilities in it need to be defined and understood in order to gain an understanding of the predictions and validity of quantum mechanics. The interpretational problems of quantum mechanics are also connected with the interpretation of the concept of probability. In this thesis the use of probability theory as extended logic, in particular in the way it was presented by E. T. Jaynes, will be central. With this interpretation of probabilities they become a subjective notion, always dependent on one's state of knowledge or the context in which they are assigned, which has consequences on how things are to be viewed, understood and tackled in quantum mechanics. For instance, the statistical operator or density operator, is usually defined in terms of probabilities and therefore also needs to be updated when the probabilities are updated by acquisition of additional data. Furthermore, it is a context dependent notion, meaning, e.g., that two observers will in general assign different statistical operators to the same phenomenon, which is demonstrated in the papers of the thesis. It is also presented an alternative and conceptually clear approach to the problematic notion of "probabilities of probabilities", which is related to such things as probability distributions on statistical operators. In connection to this, we consider concrete numerical applications of Bayesian quantum state assignment methods to a three-level quantum system, where prior knowledge and various kinds of measurement data are encoded into a statistical operator, which can then be used for deriving probabilities of other measurements. The thesis also offers examples of an alternative quantum state assignment technique, using maximum entropy methods, which in some cases are compared with the Bayesian quantum state assignment methods. Finally, the interesting and important problem whether the statistical operator, or more generally quantum mechanics, gives a complete description of "objective physical reality" is considered. A related concern is here the possibility of finding a "local hidden-variable theory" underlying the quantum mechanical description. There have been attempts to prove that such a theory cannot be constructed, where the most well-known impossibility proof claiming to show this was given by J. S. Bell. In connection to this, the thesis presents an idea for an interpretation or alternative approach to quantum mechanics based on the concept of space-time.

  • 275.
    Månsson, Anders
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Porta Mana, Piero G. Luca
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Numerical Bayesian quantum-state assignment for a three-level quantum system: II. Average-value data with a constant, a Gaussian-like, and a Slater priorManuskript (Annet vitenskapelig)
    Abstract [en]

    This paper offers examples of concrete numerical applications of Bayesian quantum-state assignment methods to a three-level quantum system. The statistical operator assigned on the evidence of various measurement data and kinds of prior knowledge is computed partly analytically, partly through numerical integration (in eight dimensions) on a computer. The measurement data consist in the average of outcome values of N identical von Neumann projective measurements performed on N identically prepared three-level systems. In particular the large-N limit will be considered. Three kinds of prior knowledge are used: one represented by a plausibility distribution constant in respect of the convex structure of the set of statistical operators; another one represented by a prior studied by Slater, which has been proposed as the natural measure on the set of statistical operators; the last prior is represented by a Gaussian-like distribution centred on a pure statistical operator, and thus reflecting a situation in which one has useful prior knowledge about the likely preparation of the system. The assigned statistical operators obtained with the first two kinds of priors are compared with the one obtained by Jaynes' maximum entropy method for the same measurement situation. In the companion paper the case of measurement data consisting in absolute frequencies is considered.

  • 276.
    Månsson, Anders
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Porta Mana, Piero Giovanni Luca
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Numerical Bayesian state assignment for a three-level quantum system: I. Absolute-frequency data; constant and Gaussian-like priorsManuskript (Annet vitenskapelig)
    Abstract [en]

    This paper offers examples of concrete numerical applications of Bayesian quantum-state-assignment methods to a three-level quantum system. The statistical operator assigned on the evidence of various measurement data and kinds of prior knowledge is computed partly analytically, partly through numerical integration (in eight dimensions) on a computer. The measurement data consist in absolute frequencies of the outcomes of N identical von Neumann projective measurements performed on N identically prepared three-level systems. Various small values of N as well as the large-N limit are considered. Two kinds of prior knowledge are used: one represented by a plausibility distribution constant in respect of the convex structure of the set of statistical operators; the other represented by a Gaussian-like distribution centred on a pure statistical operator, and thus reflecting a situation in which one has useful prior knowledge about the likely preparation of the system. In a companion paper the case of measurement data consisting in average values, and an additional prior studied by Slater, are considered.

  • 277.
    Månsson, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Adatoms, Quasiparticles & Photons: The Multifaceted World of Photoelectron Spectroscopy2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The experimental work presented in this thesis is based on a wide assortment of very advanced and highly sophisticated photoelectron spectroscopy (PES) techniques. The objective of the present study has been to reveal and understand the electronic structure and electron dynamics in a broad spectrum of materials, ranging from wide band gap oxides, via semiconductors along with metals, and finally high-temperature superconductors.

    The first part of the thesis concerns laser-based pump-and-probe PES. This unique experimental technique has permitted a study of the excited electronic structure and the electron dynamics of several semiconductor surfaces. An insight into details of the adatom to restatom charge-transfer of the Ge(111)c(2x8) surface is presented, as well as an estimate for the timescale in which the dynamic adatoms of the Ge(111):Sn(sqrt3xsqrt3)R30deg surface operate. Further results comprise a novel unoccupied surface state at the GaSb(001) surface as well as a time-resolved study of the charge accumulation layer at the InAs(111)A/B surfaces.

    In the second part, high-resolution synchrotron based angle-resolved PES (ARPES) data from the cuprate high-temperature superconductor La(2-x)Sr(x)CuO(4) (LSCO) is presented. This extensive study, reveals detailed information about how the Fermi surface and electronic excitations evolve with doping in the superconducting state. The results comprise support for a connection between high- and low-energy electronic responses, the characteristics of the superconducting gap, and indication of a quantum phase transition between two different superconducting phases.

    In the third group of experiments we move away from the two-dimensional systems and concentrate on fully three-dimensional compounds. By the use of soft x-ray ARPES it is possible to extract the three-dimensional electronic structure in a straightforward manner with increased k(perpendicular)-resolution. As a result the first high-quality ARPES data from Cu2O is presented, as well as a novel method for extracting the (real space) electron density by ARPES. These experiments clearly display the advantages of using soft x-ray ARPES. If the material and type of experiment is chosen wisely, the benefit of the increased k||-window and the free electron final state, surpass the drawbacks of decreased count-rate and inferior energy resolution. Finally we return to the high-temperature superconductors (NCCO & Nd-LSCO) and make use of the increased bulk-sensitivity. From an evident change in the shape of the Fermi surface when moving from low to high photon energies, the durface to bulk difference in electronic structure is highlighted.

  • 278.
    Månsson, Martin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Claesson, Thomas
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Finazzi, Marco
    Dallera, Claudia
    De Nadaï, Celine
    Brookes, Nicholas B.
    Tjernberg, Oscar
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Revealing the charge density in solidsManuskript (Annet vitenskapelig)
  • 279.
    Månsson, Martin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Claesson, Thomas
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Hayden, S. M.
    Tjernberg, Oscar
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Chang, Johan
    Pailhés, Stephane
    Shi, Ming
    Mesot, Joël
    Patthey, Luc
    Momono, Naoki
    Oda, Migaku
    Ido, Masayuki
    Experimental evidence of a quantum phase transition in La(2-x)Sr(x)CuO4()Manuskript (Annet vitenskapelig)
  • 280.
    Månsson, Martin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Michael A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101).
    Tjernberg, Oscar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101).
    Claesson, Thomas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101).
    Karlsson, Henrik S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101).
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101).
    Electronic structure and electron dynamics at the GaSb(001) surface studied by femtosecond pump-and-probe pulsed laser photoemission spectroscopy2006Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, nr 15, s. 5308-5311Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 281.
    Månsson, Martin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Tjernberg, Oscar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Michael A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Claesson, Thomas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Ultrafast electron dynamics and recombination at the Ge(111): Sn(root 3 X root 3)R30 degrees surface2008Inngår i: Surface Science Letters, ISSN 0039-6028, Vol. 602, nr 5, s. L33-L37Artikkel i tidsskrift (Fagfellevurdert)
    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].

  • 282.
    Månsson, Martin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Tjernberg, Oscar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Michael A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Karlsson, Henrik S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Le Lay, Guy
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Claesson, Thomas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Electronic structure and electron dynamics of delocalized adatom states at the Ge(111)c(2 x 8) surfaceInngår i: Physical Review B, ISSN 1098-0121Artikkel i tidsskrift (Fagfellevurdert)
  • 283. Neff, Curtis W.
    et al.
    Andersson, L. Mauritz
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Coupled resonator optical waveguide structures with highly dispersive media2007Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 15, nr 16, s. 10362-10369Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Analysis of photonic crystal coupled resonator optical waveguide (CROW) structures with a highly dispersive background medium is presented. A finite-difference time-domain algorithm was employed which contains an exact representation of the permittivity of a three-level atomic system which exhibits electromagnetically induced transparency (EIT). We find that the coupling strength between nearest-neighbor cavities in the CROW decreases with increasing steepness of the background dispersion, which is continuously tunable as it is directly related to the control field Rabi frequency. The weaker coupling decreases the speed of pulse propagation through the waveguide. In addition, due to the dispersive nature of the EIT background, the CROW band shape is tuned around a fixed k-point. Thus, the EIT background enables dynamic tunability of the CROW band shape and the group velocity in the structure at a fixed operating point in momentum space.

  • 284. Neff, Curtis W.
    et al.
    Andersson, L. Mauritz
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Modelling electromagnetically induced transparency media using the finite-difference time-domain method2007Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Time-domain electromagnetic modelling of complex structures which include both non-dispersive media and media exhibiting electromagnetically induced transparency (EIT) require a general, robust calculation method such as finite-difference time-domain (FDTD). We propose a complex-valued, exact two-pole representation of the permittivity of a three-level system which is suitable for integration into the FDTD algorithm via the auxiliary differential equation method. Our calculation model confirmed reported results which were calculated with an approximate representation of the EIT permittivity. Additionally, propagation calculations which mimic slow light experiments were performed. A major advantage of our representation is the ease with which changes in the control field Rabi frequency can be implemented by using a time-dependent permittivity.

  • 285. Neuvonen, P. T.
    et al.
    Vines, L.
    Johansen, K. M.
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Svensson, B. G.
    Kuznetsov, A.Yu.
    Transportation of Na and Li in hydrothermally grown ZnO2010Inngår i: Zinc oxide and related materials 2009, Materials Research Society, 2010, s. 29-34Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Secondary ion mass spectrometry has been applied to study the transportation of Na and Li in hydrothermally grown ZnO. A dose of 10 15 cm-2 of Na+ was implanted into ZnO to act as a diffusion source. A clear trap limited diffusion is observed at temperatures above 550 °C. From these profiles, an activation energy for the transport of Na of 7 ∼1.7 eV has been extracted. The prefactor for the diffusion constant and the solid solubility of Na cannot be deduced independently from the present data but their product estimated to be ∼ 3 × 1016 cm-1 s-1. A dissociation energy of ∼2.4 eV is extracted for the trapped Na. The measured Na and Li profiles show that Li and Na compete for the same traps and interact in a way that Li is depleted from Na-rich regions. This is attributed to a lower formation energy of Na-on-zinc-site than that for Li-on-zinc-site defects and the zinc vacancy is considered as a major trap for migrating Na and Li atoms. Consequently, the diffasivity of Li is difficult to extract accurately from the present data, but in its interstitial configuration Li is indeed highly mobile having a diffasivity in excess of 10-11 cm2 s-1 at 500 °C .

  • 286. Neuvonen, Pekka T.
    et al.
    Vines, Lasse
    Kuznetsov, Andrej Yu
    Svensson, Bengt G.
    Du, Xiaolong
    Tuomisto, Filip
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Interaction between Na and Li in ZnO2009Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, nr 24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interaction between group-Ia elements in ZnO have been studied by implanting Na into hydrothermally grown ZnO samples containing similar to 4x10(17) Li/cm(3) and employing secondary ion mass spectrometry for sample analysis. Postimplantation annealing above 500 degrees C results in a diffusion of Na and concurrently Li is efficiently depleted from the regions occupied by Na. The data show unambiguously that Na and Li compete for the same trapping site and the results provide strong experimental evidence for that the formation energies of Na on Zn site together with that of interstitial Li are lower than those of Li on Zn site and interstitial Na in highly resistive ZnO. This conclusion is also supported by recent theoretical estimates of the formation energies of these species as a function of the Fermi-level position in ZnO.

  • 287.
    Nilson, K.
    et al.
    Department of Physics, Uppsala University.
    Palmgren, Pål
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åhlund, J.
    Department of Physics, Uppsala University.
    Schiessling, J.
    MAX-laboratory, University of Lund.
    Göthelid, E.
    Department of Physics, Uppsala University.
    Mårtensson, N.
    Department of Physics, Uppsala University.
    Puglia, C.
    Department of Physics, Uppsala University.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    STM and XPS characterization of Zinc Phthalocyanine on InSb(001)2008Inngår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 602, nr 2, s. 452-459Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Zinc phthalocyanine (ZnPc) adsorbed on the InSb(0 0 1)-c(8 x 2) surface has been studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Coverages from sub-monolayer to monolayer (ML) have been investigated. The molecules form ordered structures on the reconstructed rows of the surface with the molecular plane parallel to the surface. A change in the electronic structure between the sub-ML and higher coverages has been observed. Moreover, in order to study the influence of annealing on the electronic and geometric structures, the samples have been heated to elevated temperatures (about 640 K). In addition, multi-layer ZnPc films have been characterized by XPS measurements.

  • 288.
    Nilsson, Lars-Erik
    et al.
    Acreo.
    Yu, Zhangwei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Tarasenko, Oleksandr
    Acreo.
    Knape, Harald
    Fonjallaz, Pierre-Yves
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Margulis, Walter
    Acreo.
    High-speed switching in fibres with electrodes2007Inngår i: ICTON 2007: Proceedings of the 9th International Conference on Transparent Optical Networks, Vol 1, 2007, s. 232-233Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fibres with holes are provided with metal electrodes that fill the entire cross-section of the holes. Refractive index change and birefringence result from applying high current pulses for time intervals in the nanosecond range. High-speed polarization rotation and fibre Bragg grating wavelength tuning can be accomplished. Such electrically driven components are totally spliced with low insertion loss. They have no moving parts, are < 10 cm long and can be used in fibre laser cavities for Q-switching.

  • 289. Nilsson, S.
    et al.
    Kjellberg, T.
    Klinga, T.
    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.
    Wallin, J.
    Streubel, K.
    Improved spectral characteristics of MQW-DFB lasers by incorporation of multiple phase-shifts1995Inngår i: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 13, s. 434-441Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The single-mode stability of strained-layer MQW-DFB lasers with electron-beam written gratings containing zero, one and three phase-shifts, and with a relatively large coupling strength, has been investigated theoretically and experimentally. The fabricated lasers with the multiple phase-shifted (MPS) structure exhibited a higher degree of stability than the lambda;/4-shifted lasers, and a considerably improved stability for both categories with phase-shifts compared to the nonshifted lasers was obtained. These results were in good agreement with our simulations. An investigation of the linewidths of the phase-shifted lasers is also presented. The MPS lasers had a significantly lower linewidth floor (down to 600 kHz) than those with one phase-shift. There was no degradation of the side-mode suppression-ratio correlated to the linewidth floor or rebroadening. A possible explanation for the lower linewidth floors obtained for the MPS lasers is that this structure is less sensitive to inhomogeneous carrier fluctuations. Longitudinal fluctuations in the shape of the photon density distribution will thereby be suppressed

  • 290.
    Nilsson, S.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Kjellberg, T.
    Klinga, T.
    Wallin, J.
    Streubel, K.
    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.
    DFB laser with nonuniform coupling coefficient realized by double-layer buried grating1993Inngår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 5, s. 1128-1131Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A technique for the realization of a nonuniform grating coupling coefficient kappa , and its implementation in distributed-feedback (DFB) lasers is presented. This technique, which is an extension of the buried-grating concept, offers precise control of the coupling coefficient and enables a kappa -ratio greater than 10. DFB lasers with an asymmetric kappa -variation have been fabricated using this method. A front-to-rear facet output power ratio close to five was obtained, qualitatively in agreement with simulations.<>

  • 291. Nipoti, R.
    et al.
    Nath, A.
    Rao, M.V.
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Mancarella, F.
    Zampolli, S.
    Tian, Y.L.
    High dose Al + implanted and microwave annealed 4H-SiC2012Inngår i: Silicon Carbide and Related Materials 2011, Trans Tech Publications Inc., 2012, s. 817-820Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A post implantation microwave annealing technique has been used for the electrical activation of Al + implanted ions in semi-insulating 4H-SiC. The annealing temperatures have been 2000-2100°C. The implanted Al concentration has been varied from 5 × 10 19 to 8 × 10 20 cm -3. A minimum resistivity of 2 × 10 -2 Ω·cm and about 70% electrical activation of the implanted Al has been measured at room temperature for an implanted Al concentration of 8 × 10 20 cm -3 and a microwave annealing at 2100°C for 30s.

  • 292. Nisbet-Jones, P. B. R.
    et al.
    Dilley, Jerome
    Ljunggren, Daniel
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. Clarendon Laboratory, University of Oxford, United Kingdom .
    Kuhn, Axel
    Highly efficient source for indistinguishable single photons of controlled shape2011Inngår i: New Journal of Physics, ISSN 1367-2630, Vol. 13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate a straightforward implementation of a push-button like single-photon source, which is based on a strongly coupled atom-cavity system. The device operates intermittently for periods of up to 100μs, with single-photon repetition rates of 1.0MHz and an efficiency of 60%. Atoms are loaded into the cavity using an atomic fountain, with the upper turning point near the cavity's mode centre. This ensures long interaction times without any disturbances induced by trapping potentials. The latter is the key to reaching deterministic efficiencies as high as obtained in probabilistic photon-heralding schemes. The price to pay is the random loading of atoms into the cavity and the resulting intermittency. However, for all practical purposes, this has a negligible impact as an individual atom may emit up to 100 successive photons.

  • 293. Norrman, A.
    et al.
    Setälä, T.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Partial spatial coherence and polarization properties of surface plasmon fields2011Inngår i: Proc SPIE Int Soc Opt Eng, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We analyze theoretically the (spectral) spatial coherence and polarization properties in fluctuating surface plasmon fields generated at a lossy, thin metal film surrounded on both sides by air. Using rigorous electromagnetic interactions at the interfaces and the theory of optical coherence in 3D fields, we show that new coherence and polarization effects may occur in such plasmon fields. In particular, coherence lengths extending over several thousands of wavelengths, or coherence lengths significantly shorter than the wavelength of light in vacuum, can be found at certain frequencies. Using a recent 3D formulation, we also examine the degree of polarization in such random surface plasmon fields. We show that the field may be partially polarized in the immediate vicinity of the excitation of the surface plasmon modes, even though it is fully polarized farther away. In addition, we demonstrate that an increasing number of modes leads to a more polarized field above the plasmon excitation region, with the degree of polarization effectively independent of the height. 

  • 294. Olsen, U. L.
    et al.
    Schmidt, S.
    Poulsen, H. F.
    Linnros, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Yun, Sang Ho
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Di Michiel, M.
    Martin, T.
    Structured scintillators for X-ray imaging with micrometre resolution2009Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 607, nr 1, s. 141-144Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A 3D X-ray detector for imaging of 30-200keV photons is described. It comprises a stack of semitransparent structured scintillators, where each scintillator is a regular array of waveguides in silicon, and with pores filled with CsI. The performance of the detector is described theoretically and explored in detail through simulations. The resolution of a single screen is shown to be determined only by the pitch, at least up to 100 keV. In comparison to conventional homogenous screens an improvement in efficiency by a factor 5-15 is obtainable. The cross-talk between screens in the 3D detector is shown to be negligible. The concept of such a 3D detector enables ray tracing and super resolution algorithms to be applied. Realized pore geometries have a lower aspect ratio than used in simulations and the roughness of the pore walls gives a 13% decrease in waveguide efficiency. Compared to currently used regular scintillators with similar resolution an efficiency increase by a factor 4 has been found for the structured scintillator.

  • 295.
    Ougazzaden, A.
    et al.
    Georgia Inst Technol, Georgia Tech, Metz, France.
    Rogers, D. J.
    Nanovat SARL, Orsay, France; Univ Technol Troyes, France.
    Teherani, F. Hosseini
    Nanovat SARL, Orsay; Univ Technol Troyes.
    Moudakir, T.
    Univ Metz.
    Gautier, S.
    Univ Metz.
    Aggerstam, Thomas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Saad, S. Ould
    Georgia Tech, Metz, France.
    Martin, J.
    Univ Metz.
    Djebbour, Z.
    Univ Paris.
    Durand, O.
    Thales Res & Technol France.
    Garry, G.
    Thales Res & Technol France.
    Lusson, A.
    Univ Versailles.
    McGrouther, D.
    Univ Glasgow.
    Chapman, J. N.
    Univ Glasgow.
    Growth of GaN by metal organic vapor phase epitaxy on ZnO-buffered c-sapphire substrates2008Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 310, nr 5, s. 944-947Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The materials quality and availability of large-area bulk GaN substrates is currently considered a key problem for the continuing development of improved GaN-based devices. Since industrial fabrication of bulk GaN substrates with suitable materials quality has proven very difficult, the opto-GaN industry is currently based on heteroepitaxy using either c-sapphire or 6H SiC substrates. ZnO is promising as a substrate material for GaN because it has the same wurtzite structure and a relatively small lattice mismatch (similar to 1.8%). In this study, we have successfully grown GaN by MOVPE on ZnO-buffered c-sapphire. The growth conditions required to both prevent ZnO degradation and grow monocrystal thin film of GaN have been obtained. SEM, HRXRD and micro-Raman characterizations underlined the presence of the two layers GaN and ZnO with high structural quality.

  • 296. Ozkaya, T.
    et al.
    Baykal, A.
    Kavas, H.
    Koseoglu, Y.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    A novel synthetic route to Mn3O4 nanoparticles and their magnetic evaluation2008Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 403, nr 19-20, s. 3760-3764Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Manganese oxide (Mn3O4) nanoparticles were successfully prepared by a novel oxidation-precipitation method based on oxidation of manganese sulfate to manganese salts and hydrolyzing with NaOH and concentrated NH3. X-ray diffraction (XRD) analysis confirmed the tetragonal haussmanite structure with average crystallite size of similar to 14 and similar to 11 nm: transmission electron microscopy (TEM) analysis showed crystallite size of 14 5 and 12 3 nm for NaOH- and NH3-hydrolyzed samples, respectively. The ferromagnetic transition temperatures are 38 and 40 K for NaOH- and NH3-hydrolyzed samples, respectively. These values are lower than that of bulk Mn3O4. Both samples show superparamagnetic behavior at room temperature, with no apparent saturation magnetization and hysteresis in the region of measured field strength, and they also exhibit relatively large coercivity below the ferromagnetic transition temperature. Below the transition, marked differences are observed in temperature dependence of magnetization, hysteresis loop shape, and type of the samples from the bulk values. The particles are considered as single magnetic domains with random orientations of magnetic moments and thermal fluctuations of anisotropic axes. These results are attributed to the smaller size (increase in surface to volume ratio) of the samples, which cause an increase of effective magnetic surface anisotropy.

  • 297. Ozkaya, Tevhide
    et al.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Baykal, Abdulhadi
    Kavas, Hueseyin
    Koseoglu, Yuksel
    Aktas, Bekir
    Synthesis of Fe3O4 nanoparticles at 100 degrees C and its magnetic characterization2009Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 472, nr 1-2, s. 18-23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Superparamagnetic iron oxide nanoparticles were synthesized by a novel, simple and cost-effective gel-to-crystalline method by alkalizing ferrous chloride with ammonium hydroxide at 80-100 degrees C under refluxing conditions. Average crystallite size is determined as 11 nm from XRD and 11.4 nm from TEM: magnetic domain size is 9.7 nm. The saturation magnetization is 390 emu/cm(3) at 300 K, and TB is 134 K. The reduction of magnetic particle size and M-s is attributed to the presence of non-magnetic (dead) surface layer, compositional variations, superparamagnet relaxation and spin canting because of the ultrafine nature of the material. The maximization in magnetization near the blocking temperature, T-B, is attributed to a large degree of inversion of the Fe3O4 particles. Results also indicated the existence of interparticle interactions in the thermomagnetic characteristics of spinels at lower field strengths.

  • 298.
    Palmgren, Pål
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Initial stages of metal- and organic-semiconductor interface formation2006Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This licentiate thesis deals with the electronic and geometrical properties of metal-semiconductor and organic-semiconductor interfaces investigated by photoelectron spectroscopy and scanning tunneling microscopy.

    First in line is the Co-InAs interface (metal-semiconductor) where it is found that Co is reactive and upon adsorption and thermal treatment it alloys with the indium of the substrate to form metallic islands, about 20 nm in diameter. The resulting broken bonds causes As entities to form which are loosely bond to the surface and evaporate upon thermal treatment. Thus, the adsorption of Co results in a rough interface.

    Secondly the metal-free phthalocyanine (H2PC) - titanium dioxide interface (organic-semiconductor) is investigated. Here it is found that the organic molecules arrange themselves along the substrate rows upon thermal treatment. The interaction with the TiO2 is mainly with the valence Π-electrons in the molecule causing a relatively strong bond, but this interaction is short range as the second layer of molecules retains their molecular character. This results in an ordered adsorption but limited mobility of the molecules on the surface prohibiting well ordered close packed layers. Furthermore, the hydrogen atoms inside the cyclic molecule leave the central void upon thermal treatment.

    The third case is the H2PC-InAs/InSb interface (organic-semiconductor). Here ordered overlayer growth is found on both substrates where the molecules are preferentially adsorbed on the In rows in the [110] direction forming one-dimensional chains. The InSb-H2PC interface is found to be weakly interacting and the bulk-like molecular character is retained upon both adsorption and thermal treatment. On the InAs-H2PC interface, however, the interaction is stronger. The molecules are more affected by the surface bond and this effect stretches up a few monolayers in the film after annealing.

  • 299.
    Palmgren, Pål
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Angot, T.
    Nlebedim, Cajetan Ikenna
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Layet, J. -M
    Le Lay, G.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Ordered phthalocyanine superstructures on Ag(110)2008Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, nr 6, s. 064702-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Organic-metal interfaces, in particular, self-assembling systems, are interesting in the field of molecular electronics. In this study, we have investigated the formation of the Ag(110)-iron phthalocyanine (FePc) interface in a coverage range of less than 1 and up to 2 ML using synchrotron based photoelectron spectroscopy and low energy electron diffraction. As-deposited FePc forms a densely packed first layer exhibiting a 3x2/c(6x2) symmetry. Upon thermal treatment the order at the interface is modified depending on the initial FePc coverage, resulting in less densely packed but still ordered superstructures. The first monolayer is relatively strongly bound to the substrate, leading to the formation of an interface state just below the Fermi level. The highest occupied molecular orbital of FePc in the second layer is found at 1 eV higher binding energy compared to the interface state.

  • 300.
    Palmgren, Pål
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Angot, T.
    Nlebedim, Cajetan Ikenna
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Layet, J.-M.
    Le Lay, G.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Ordered phthalocyanine structures on Ag(110)2007Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690Artikkel i tidsskrift (Annet vitenskapelig)
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