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  • 301.
    Khatib, Iyad Al
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Ayani, Rassul
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Forsgren, Daniel
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wireless LAN Access Points as a Queuing System, Performance Analysis and Service Time2002In: The Eighth ACM International Conference on Mobile Computingand Networking (ACM MOBICOM 2002 Conference), Association for Computing Machinery (ACM), 2002Conference paper (Refereed)
  • 302. Kim, H. J.
    et al.
    Ismail, M.
    De Liera Gonzalez, Delia Rodriguez
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A 2.4 GHz concurrent radio transceiver architecture for bluetooth and Wi-Fi2005In: ISIE 2005: Proceedings of the IEEE International Symposium on Industrial Electronics 2005, 2005, p. 1151-1154Conference paper (Refereed)
    Abstract [en]

    A radio transceiver architecture for concurrent processing of Bluetooth and Wi-Fi (IEE 802.11b) radio signals in the 2.4 GHz ISM band is presented. The architecture is tailored for low power implementation in a standard deep sub-micron CMOS process. It adopts an innovative frequency plan exploiting adaptive frequency hopping for the concurrent processing and of Bluetooth and Wi-Fi radio signals. A link budget analysis is performed to map out system level requirements to block level specifications.

  • 303.
    Kim, Jang-Yong
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Novel tantalate-niobate films for microwaves2005Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Microwave materials have been widely used in a variety of applications ranging from communication devices to military satellite services, and the study of materials properties at microwave frequencies and the development of functional microwave materials have always been among the most active areas in solid-state physics, materials science, and electrical and electronic engineering. In recent years, the increasing requirements for the development of high speed, high frequency circuits and systems require complete understanding of the properties of materials function at microwave frequencies.

    Ferroelectric materials usually have high dielectric constants, and their dielectric properties are temperature and electric field dependent. The change in permittivity as a function of electric field is the key to a wide range of applications. Ferroelectric materials can be used in fabrication capacitors for electronic industry because of their high dielectric constants, and this is important in the trend toward miniaturization and high functionality of electronic products. The simple tunable passive component based on ferroelectric films is a varactor which can be made as a planar structure, and electrically tunable microwave integrated circuits using ferroelectric thin films can be developed. Therefore, it is very important to characterize the dielectric constant and tunability of ferroelectric thin films.

    This thesis shows experimental results for growth, crystalline properties and microwave characterization of Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), Ba0.5Sr0.5TiO3 (BST) as well as AgTaO3 (ATO), AgNbO3 (ANO) thin films. The films were grown by Pulsed Laser Deposition (PLD) and rf-magnetron sputtering of a stoichiometric, high density, ceramic NKN, ATN, BST target onto single crystal LaAlO3(LAO), Al2O3 (sapphire), and Nd:YAlO3, and amorphous glass substrates. By x-ray diffractometry, NKN, ATN, BST films on LAO substrates were found to grow epitaxially, whereas films on r-cut sapphire substrates were found to be preferentially (00l) oriented.

    Coplanar waveguide interdigital capacitor (CPWIDC) structures were fabricated by standard photolithography processing and metal lift-off technique. Microwave properties of the NKN/Sapphire and ATN/Sapphire with CPW structures were characterized using on-wafer microwave measurement technique. Measurement setup is composed of network analyzer, probe station, and microwave G-S-G probes. External electric field through the connection between network analyzer and power supply was applied to measure voltage tunability. Measured S-parameter were used for the calculation of capacitance, loss tanδ, tunability and K-factor.

    The NKN films interdigital capacitors with 2 μm finger gap on Nd:YAlO3 showed superior performance compared to ATN in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40V, 200 kV/cm) was about 29%, loss tangent ∼ 0.13, K-factor = tunability/tanδ from 152% @ 10GHz to 46% @ 40GHz.

    The microwave performance of ATN film CPWIDC with 2 μm finger gap on sapphire substrate in the microwave range from 1 to 40 GHz showed that frequency dispersion is about 4.3%, voltage tunability was 4.7% @ 20GHz and 200 kV/cm, loss tangent ∼ 0.068 @ 20GHz, K-factor = tunability/tanδ is ranged from 124% @ 10GHz to 35% @ 40GHz.

    The BST films CPWIDC with 2μmfinger gap on Al2O3 substrate showed frequency dispersion of capacitance in the microwave range from 1 to 40 GHz about 17%, voltage tunability = 1 - C(40V)/C(0) ∼ 22.2%, loss tangent ∼ 0.137 @ 20GHz, and K-factor = tunability/tanδ from 281% @ 10GHz to 95% @ 40GHz.

  • 304.
    Kim, Jang-Yong
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Microwave Ba0.5Sr0.5TiO3 Thin Film Microwave VaractorsManuscript (preprint) (Other academic)
  • 305.
    Kim, Jang-Yong
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Microwave Properties of Niobate-Tantalate Film Coplanar WaveguideInterdigital CapacitorsManuscript (preprint) (Other academic)
  • 306.
    Kim, Jang-Yong
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Preparation of AgTaO3 and AgNbO3 thin films by pulsed laser depositionManuscript (preprint) (Other academic)
  • 307.
    Kim, Joo-Hyung
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Micromachined epitaxial colossal mognetoresistors for uncooled infrared bolometer2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    High quality perovskite manganites, La1-xAxMnO3 (A = Ca, Sr, Ba) are very attractive materials due to their great application potential for magnetic memory, uncooled infrared (IR) microbolometer and spintronics devices. This thesis presents studies of the growth and material characterization (including structural, electrical, magnetic and noise) of epitaxial manganite films on Si and GaAs. Furthermore, investigations about strain effect on structural and electrical properties of manganites, and finally fabrication of self-supported free standing microstructures for uncooled IR bolometer are also demonstrated.

    To obtain high quality epitaxial manganite films on semiconductor substrates at room temperature, using a combination of La0.67Sr0.33MnO3 (LSMO) and La0.67Ca0.33MnO3 (LCMO) compounds, La0.67(Sr,Ca)0.33MnO3 (LSCMO) films were successfully grown on Si substrates with Bi4Ti3O12(BTO)/CeO2/YSZ buffers by pulsed laser deposition (PLD) technique. Crystallographic relations between layers shows cube-on-cube for BTO/CeO2/YSZ/Si and diagonal-on-side for LSCMO films on BTO layer. 4.4 %K-1 maximum temperature coefficient of resistivity (TCR = 1/ρ·dρ/dT) and 2.9 %kOe-1 colossal magnetoresistance (CMR) were obtained at room temperature. Assuming of a prototype of temperature sensor, 1.2 μK/√Hz of noise equivalent temperature difference (NETD) and 2.9×108 cm√Hz/W of detectivity are expected to achieve at 294 K, 30 Hz. For GaAs substrates, using MgO buffer layer, LCMO films shows 9.0 %K-1 of TCR at 223 K while LSMO exhibits 2 %K-1 at 327 K.

    Systematic strain effects on structural and electrical properties of La0.75Sr0.25MnO3 LSMO) films on BTO/CeO2/YSZ-buffered Si, Si1-xGex/Si (compressive strain, x = 0.05-0.20) and Si1-yCy/Si (tensile, y = 0.01) were investigated. The strain induced from Si1-xGex/Si and Si0.99C0.01/Si has a tendency to decrease the roughness of CMR films compared to Si sample. High resistivity and low TCR values are observed for Si0.8Ge0.2/Si and Si0.99C0.01/Si samples due to excessive strains whereas Si0.9Ge0.1/Si and Si0.95Ge0.05/Si show slight improvements of films quality and TCR value.

    To fabricate LSCMO manganite bolometer on Si, wet etching with KOH and BHF and dry etching methods with Ar ion beam etching (IBE) were studied. For KOH wet etching, LSCMO films show high chemical resistance with lower than 0.2 nm/min of etch rate. BHF wet etching shows high etching selectivity over photoresist mask and silicon substrates. The etch rates for LSCMO and BTO layers are 22 and 17 nm/min. For Ar IBE, LSCMO films and oxide buffer layers show similar etch rates, 16-17 nm/min that are lower compared to 24 nm/min for Si.

    Free standing, self-supported heteroepitaxial LSCMO/BTO/CeO2/YSZ membranes for bolometer pixels on Si was successfully fabricated by Ar IBE and ICP etching techniques using a preannealed photoresist. The structural investigation by TEM revealed the sharp interfaces between layers. The electrical property of the free standing membrane was slightly degraded due to strain release and multi-step etching effect. These results demonstrate feasibility to use heteroepitaxial oxide structures as a thermally isolated membrane with conventional photoresist patterning.

  • 308.
    Kim, Joo-Hyung
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Free-standing epitaxial La1-x(Sr,Ca)(x)MnO3 membrane on Si for uncooled infrared microbolometer.2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 3Article in journal (Refereed)
    Abstract [en]

    Ar ion beam etching and inductively coupled SF6 and C4F8 plasma-etching processes have been employed to fabricate free standing membrane from the heteroepitaxial La1-x(Sr,Ca)(x)MnO3(50 nm)/Bi4Ti3O12(100 nm)/CeO2(40 nm)/YSZ(30 nm) film structure pulsed laser deposited on Si(001) wafer. We demonstrate feasibility to use epitaxial colossal magnetoresistive manganite film as thermally isolated self-supporting membrane for uncooled infrared microbolometer applications.

  • 309.
    Kim, Joo-Hyung
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Microfabricated heteroepitaxial oxide structures on silicon for bolometric arrays2005In: 2005 NSTI Nanotechnology Conference and Trade Show - NSTI Nanotech 2005 Technical Proceedings, Anaheim, CA, 2005, p. 521-524Conference paper (Refereed)
    Abstract [en]

    The microfabrication of the free standing perovskite La0.67(Sr, Ca)0.33 MnO3 (LSCMO) thin films on silicon substrates with epitaxial grown oxide buffer layers was investigated for microbolometer application. The Ar ion etching (IBE) rate of LSCMO films was found to be 16 nm/min. Using pre-annealed photoresist patterning, the free standing LSCMO pixels on epitaxial buffer oxide membrane were realized by the IBE and SF 6 inductive coupled plasma (ICP) etching process. These results can be utilized as thermally isolated membrane for heteroepitaxial oxide structures.

  • 310.
    Kim, Joo-Hyung
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Microfabrication of epitaxial La1-x(Sr,Ca)(x)MnO3 IR bolometer on Si2006In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 80, p. 47-54Article in journal (Refereed)
    Abstract [en]

    Self supported free standing heteroepitaxial La1-x(Sr,Ca)(x)MnO3 (LSCMO) membranes grown on Bi4Ti3O12(BTO)/CeO2/YSZ buffered Si substrates have been microfabricated by Ar ion beam etching (IBE) and SF6/C4F8 inductively Coupled plasma (ICP) etching technique. The electrical property of free standing membrane was compared to as-grown sample by four point measurement. These results demonstrate feasibility to use heteroepitaxial oxide film structures with conventional photoresist patterning as thermally isolated membranes for infrared microbolometers.

  • 311.
    Kim, Joo-Hyung
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wet and dry etching of La-0.67(Sr,Ca)(0.33)MnO3 films on Si.2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, p. 587-590Article in journal (Refereed)
    Abstract [en]

    We report etching processes of epitaxial La-0.67(Sr,Ca)(0.33)MnO3 (LSCMO) colossal magnetoresistive (CMR) films grown on Bi4Ti3O12/CeO2/YSZ oxide-buffered Si using buffered HF (BHF), potassium hydroxide (KOH) and Ar ion beam etching (IBE) methods. LSCMO films demonstrate high resistivity against the KOH etchant whereas 22 nm/min etching rate was obtained in the BHF with high selectivity over photoresist and Si. Compared to 24 nm/min for Si, Ar IBE yields 16 nni/min etching rate for the LSCMO film and the oxide-buffer layers.

  • 312.
    Kim, Joo-Hyung
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Ignatova, Velislava Angelova
    Fraunhofer Institute, Center of Nanoelectronic Technologies (CNT).
    Wet etching study of La-0.67(Sr0.5Ca0.5)(0.33)MnO3 films on silicon substrates2008In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 37, no 3, p. 361-367Article in journal (Refereed)
    Abstract [en]

    Wet etching of colossal magnetoresistive (CMR) perovskite La-0.67(Sr0.5Ca0.5)(0.33)MnO3 (LSCMO) films on Bi4Ti3O12/CeO2/yttrium-stabilized zirconia (YSZ)-buffered Si substrates was investigated using potassium hydroxide (KOH) and buffered hydrofluoric acid (BHF) solutions. X-ray diffraction (XRD) and scanning spreading resistance microscopy (SSRM) measurements revealed that the morphological roughness of the LSCMO films increases, while the electrical resistance roughness decreases, with increasing KOH etching time. The LSCMO films are highly chemically resistant to KOH solution; however, in the case of BHF etching, an etch rate of 22 nm/min was obtained with high selectivity over a photoresist mask.

  • 313.
    Kim, Joo-Hyung
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Radamson, Henry
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Properties of La0.75Sr0.25MnO3 films grown on Si substrate with Si1-xGex and Si1-yCy buffer layers2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, p. 411-415Article in journal (Refereed)
    Abstract [en]

    The structural and electrical properties of La0.75Sr0.25MnO3 (LSMO) film on Bi4Ti3O12 (BTO)/CeO2/YSZ buffered Si1-xGex/Si(0.05

  • 314.
    Kim, Joo-Hyung
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    The effect of strained Si1-xGex and Si1-yCy layers for La0.75Sr0.25MnO3 films grown on oxide-buffered Si substrates.2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 1Article in journal (Refereed)
    Abstract [en]

    We report the effect of strain on the structural and electrical properties of colossal magnetoresistive (CMR) La0.75Sr0.25MnO3 (LSMO) films grown on Bi4Ti3O12/CeO2/ yttrium-stabilized-zirconia-buffered Si1-xGex/Si (x=0-0.20) and Si1-yCy/Si (y=0-0.01) substrates. The strain in the buffer layer stack was tailored by varying the Ge and C contents in SiGe and SiC layers. It has been demonstrated that the relaxation of Bi4Ti3O12 layer is dependent on Ge content and this strongly affects the quality of the LSMO film. The surface roughness of LSMO was also strain dependent and samples grown on SiGe and SiC template layers were significantly smoother than that on Si. High resistivity and low values of the temperature coefficient of resistivity were obtained in LSMO films on Si0.8Ge0.2/Si and Si0.99C0.01/Si whereas Si0.9Ge0.1/Si sample shows a slight improvement in the crystalline and electrical LSMO properties compared to the CMR film grown onto the Si substrate.

  • 315. Kim, Yong-Su
    et al.
    Jeong, Youn-Chang
    Sauge, Sebastien
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Makarov, Vadim
    Kim, Yoon-Ho
    Ultra-low noise single-photon detector based on Si avalanche photodiode2011In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 82, no 9, p. 093110-Article in journal (Refereed)
    Abstract [en]

    We report operation and characterization of a lab-assembled single-photon detector based on commercial silicon avalanche photodiodes (PerkinElmer C30902SH, C30921SH). Dark count rate as low as 5Hz was achieved by cooling the photodiodes down to -80 degrees C. While afterpulsing increased as the photodiode temperature was decreased, total afterpulse probability did not become significant due to detector's relatively long deadtime in a passively-quenched scheme. We measured photon detection efficiency >50% at 806 nm.

  • 316.
    Kjebon, Olle
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Akram, Nadeem
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    40 Gb/s transmission experiment using directly modulated 1.55 mu m DBR lasers2003In: Conference Proceedings - International Conference on Indium Phosphide and Related Materials, 2003, p. 495-498Conference paper (Refereed)
    Abstract [en]

    Directly modulated two section 1.55 mum InGaAsP DBR lasers were used for 40 Gb/s error free operation back-to-back and through 1 km of standard single mode fiber.

  • 317.
    Kjebon, Olle
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Transmission at 20 Gb/s with directly modulated DBR lasers over 30 km standard fiber2002In: Optical Communication, 2002. ECOC 2002. 28th European Conference on, 2002, Vol. 1, p. 1-2Conference paper (Refereed)
    Abstract [en]

    Transmission of 20 Gb/s NRZ over 30 km of standard fiber was accomplished with directly modulated DBR lasers at 1.55 mum. Experiments were performed without dispersion compensation and optical amplification and a negative penalty was observed

  • 318.
    Kjebon, Olle
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, S.
    Nilsson, S.
    Stalnacke, B.
    Backbom, L.
    Two-section InGaAsP DBR-lasers at 1.55 mu;m wavelength with 31 GHz direct modulation bandwidth1997In: Indium Phosphide and Related Materials, 1997., International Conference on, 1997, p. 665-668Conference paper (Refereed)
    Abstract [en]

    The small signal modulation response of two-section InGaAsP DBR-lasers at 1.55 mu;m wavelength was investigated. The response was fitted to a general transfer function and it was found that for almost all lasers the response could be described by a three pole model consisting of the laser response from the standard rate equations and an additional first order low pass roll-off. The lasers exhibited reduced damping and increased resonance frequency due to what we believe is detuned loading. This led to a maximum bandwidth of 30 GHz for lasers described by the three pole model. Some lasers exhibited an additional effect which we believe is cavity resonant enhancement of one of the modulation side-bands. This effect increased the maximum -3dB bandwidth to 31 GHz but could not be described by a three pole model

  • 319.
    Kjebon, Olle
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nilsson, Stefan
    KTH, Superseded Departments, Electronics.
    Stålnacke, Björn
    KTH, Superseded Departments, Electronics.
    Modulation response measurements and evaluation of MQW InGaAsP lasers of various designs1996In: Proc. SPIE, Vol. 2684, 1996, p. 138-152Conference paper (Other academic)
    Abstract [en]

    Resultsfrom modulation measurements of 40 high-speed multi quantum well (MQW)lasers ((lambda) equals 1.55 micrometer) of various designs are presented.By fitting the careful calibrated measurements, both magnitude and phase,to an analytical transfer function we were able to determineif a certain laser was limited by thermal effects, parasitic-likeeffects, or nonlinear gain effects. We found that most ofthe devices in the study were limited by thermal effectsand/or contact parasitics. The parasitics were found to be determinedby the width of the high-doped contact layer and claddinglayers below the metallic contact. It was also found thata high doping of the separate confinement heterostructure (SCH) layersdecreases the damping of the relaxation peak since it facilitatesthe carrier transport. Improved contact design and high doped SCH-layersresulted in modulation bandwidths of around 24 GHz.

  • 320. Kjellberg, T.
    et al.
    Nilsson, S.
    Klinga, T.
    Broberg, B.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Investigation on the spectral characteristics of DFB lasers with different grating configurations made by electron-beam lithography1993In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 11, p. 1405-1415Article in journal (Refereed)
    Abstract [en]

    The single-mode stability for distributed-feedback (DFB) lasers with various electron-beam-written grating configurations has been investigated theoretically and experimentally, for both as-cleaved and AR-coated lasers. Other laser properties interesting for coherent and multichannel communications systems, such as linewidth and tunability, have also briefly been investigated. Lasers with more sophisticated grating structures, such as an optimized multiple phase-shifted or a corrugation-pitch-modulated grating, did not exhibit performance significantly superior to that of lambda;/4-shifted DFB lasers with an appropriate coupling coefficient. Antireflection (AR)-coating of the end facets proved indispensable for obtaining a high yield for lasers with single-mode operation at high output power and for reducing the large chip-to-chip variation seen for the as-cleaved lasers. A theoretical investigation of the effect of end reflections on the stopband and of the problem of determining the coupling coefficient was also made

  • 321. Kjellberg, T.
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    The effect of stitching errors on the spectral characteristics of DFB lasers fabricated using electron beam lithography1992In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 10, p. 1256-1266Article in journal (Refereed)
    Abstract [en]

    Field stitching errors and their effect on the single-mode characteristics of distributed feedback (DFB) lasers fabricated using electron beam lithography were investigated. The stitching errors are associated with small-area, high-resolution electron beam exposure, which has the potential advantage of high-speed writing of laser gratings. Measurements show that the errors are composed of a systematic and a stochastic part. Their effect on the gain margin was simulated both for lambda;/4 phase-shifted and optimized multiple-phase-shifted DFB lasers. Simulations show that the lasers are insensitive to the systematic part of the stitching errors if the number of errors is large enough. The stochastic part was found to give rise to a variation in gain margin of the DFB lasers. It is concluded that the field stitching accuracy in the high-resolution mode of a commercial system for electron beam lithography is sufficient to provide a high yield of single-mode lasers. However, it is essential that certain precautions be taken considering exposure conditions and that a fault tolerant laser design be used

  • 322. Kjellberg, Torgil
    et al.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Nilsson, Stefan
    Broberg, Bjoern
    Effect of stitching errors on the performance of DFB lasers fabricated using e-beam lithography (Poster Paper)1992In: Electron-Beam, X-Ray, and Ion-Beam Submicrometer Lithographies for Manufacturing II, Vol. 1671, p. 191-200Article in journal (Refereed)
  • 323.
    Kleinmann, P.
    et al.
    LENAC, Universit́ Claude Bernard Lyon-I, Villeurbanne.
    Badel, Xavier
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Toward the formation of three-dimensional nanostructures by electrochemical etching of silicon2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 18, p. 183108-1-183108-13Article in journal (Refereed)
    Abstract [en]

    We report a simple technique to form various kinds of three-dimensional structures in silicon. The process flow is only composed of two steps: lithography and electrochemical etching ("LEE"). The LEE process is an easy and low-cost solution for the fabrication of high-aspect-ratio structures such as walls, tubes, and pillars. Here we demonstrate the possibility to apply the LEE process on the submicrometer scale, indicating that it is a promising tool for silicon nanomachining.

  • 324. Klimov, A. B.
    et al.
    Romero, J. L.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sanchez-Soto, L. L.
    Discrete phase-space structure of n-qubit mutually unbiased bases2009In: Annals of Physics, ISSN 0003-4916, E-ISSN 1096-035X, Vol. 324, no 1, p. 53-72Article in journal (Refereed)
    Abstract [en]

    We work out the phase-space structure for a system of n qubits. We replace the field of real numbers that label the axes of the continuous phase space by the finite field GF(2(n)) and investigate the geometrical structures compatible with the notion of unbiasedness. These consist of bundles of discrete curves intersecting only at the origin and satisfying certain additional properties. We provide a simple classification of such curves and study in detail the four- and eight-dimensional cases, analyzing also the effect of local transformations. In this way, we provide a comprehensive phase-space approach to the construction of mutually unbiased bases for n qubits.

  • 325.
    Klintskog, Erik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Generic distribution support for programming systems2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This dissertation provides constructive proof, through the implementation of a middleware, that distribution transparency is practical, generic, and extensible. Fault tolerant distributed services can be developed by using the failure detection abilities of the middleware. By generic we mean that the middleware can be used for many different programming languages and paradigms. Distribution for each kind of language entity is done in terms of consistency protocols, which guarantee that the semantics of the entities are preserved in a distributed setting. The middleware allows new consistency protocols to be added easily. The efficiency of the middleware and the ease of integration are shown by coupling the middleware to a programming system, which encompasses the object oriented, the functional, and the concurrent-declarative programming paradigms. Our measurements show that the distribution middleware is competitive with the most popular distributed programming systems (JavaRMI, .NET, IBM CORBA).

  • 326. Koivisto, Tero
    et al.
    Peltonen, Teemu
    Shen, Meigen
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Tjukanoff, Esa
    Paasio, Ari
    Sine wave as a correlating signal for UWB radio2006In: 2006 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS: VOLS 1-11, PROCEEDINGS, NEW YORK, NY: IEEE , 2006, p. 674-677Conference paper (Refereed)
    Abstract [en]

    In this paper, an analog correlator for impulse radio is designed using a sine wave as a correlating signal. The design of the low-power sine wave generation circuitry is demonstrated and the analog multiplier using this waveform is implemented. The overall power consumption of the 8GHz LC-VCO and the divider-by-two circuit is 5mW.

  • 327.
    Kolacz, Katarzyna
    et al.
    Institute of applied optics, Warsaw.
    Burvall, Anna
    National University of Ireland, Galway.
    Goncharov, Alexander
    National University of Galway, Ireland.
    Jaroszewicz, Zbigniew
    Insitute of Applied Optics, Warsaw.
    Dainty, Christopher
    National University of Ireland, Galway.
    Friberg, Ari
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Present design of lens axicons and their history2007In: Photonics Applications In Astronomy, Communications, Industry, And High-Energy Physics Experiments 2007, Pts 1 And 2 / [ed] Ryszard S. Romaniuk, SPIE - International Society for Optical Engineering, 2007, p. 693740-Conference paper (Refereed)
    Abstract [en]

    Lens systems designed to work like axicons can be a simple and cheap way of generating focal lines characteristic for these elements. We present two lens axicons made from ordinary lenses with spherical surfaces which take advantage of their inherent spherical aberration for creation of the focal segment. One of them is composed from two lenses with blocked central part. The second one is a single meniscus lens with appropriate reflective coatings. The results show that both new elements exhibit main axicon properties. Additionally the second lens axicon is resistant to astigmatism and maintains good quality of the focal segment even in the case of oblique illumination.

  • 328. Kolahdouz, M.
    et al.
    Ghandi, R.
    Hållstedt, Julius.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Osling, M.
    Wise, R.
    Wejtmans, Hans
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    The influence of Si coverage in a chip on layer profile of selectively grown Si1-xGex layers using RPCVD technique2008In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 517, no 1, p. 257-258Article in journal (Refereed)
    Abstract [en]

    The influence of chip layout (Si coverage and geometry) on the pattern dependency of selective epitaxy of SiGe layers has been investigated. The variation of Ge content and the growth rate have been investigated from a chip-to-chip (local effect) or wafer-to-wafer. The results are described by transport and diffusion of the reactant molecules over the chips during epitaxy. Our investigations are focused on the origin of pattern dependency of the deposition and also propose methods to control this growth behavior.

  • 329.
    Kolahdouz, Mohammadreza
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hållstedt, Julius
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Khatibi, Ali
    KTH, School of Information and Communication Technology (ICT).
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Wise, Rick
    Riley, Deborah J.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Comprehensive Evaluation and Study of Pattern Dependency Behavior in Selective Epitaxial Growth of B-Doped SiGe Layers2009In: IEEE transactions on nanotechnology, ISSN 1536-125X, E-ISSN 1941-0085, Vol. 8, no 3, p. 291-297Article in journal (Refereed)
    Abstract [en]

    The influence of chip layout and architecture on the pattern dependency of selective epitaxy of B-doped SiGe layers has been studied. The variations of Ge-, B-content, and growth rate have been investigated locally within a wafer and globally from wafer to wafer. The results are described by the gas depletion theory. Methods to control the variation of layer profile are suggested.

  • 330.
    Kolahdouz, Mohammadreza
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hållstedt, Julius
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Wise, R.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Selective Epitaxial Growth with Full Control of Pattern Dependency Behavior for pMOSFET Structures2008In: SIGE, GE, AND RELATED COMPOUNDS 3: MATERIALS, PROCESSING, AND DEVICES / [ed] Harame D; Caymax M; Koester S; Miyazaki S; Rim K; Tillack B; Boquet J; Cressier J; Masini G; Reznicek A; Takagi S, 2008, Vol. 16, no 10, p. 153-158Conference paper (Refereed)
    Abstract [en]

    This study presents a way to design chips to obtain uniform selective epitaxial growth of SiGe layers in pMOSPET structures. The pattern dependency behavior of tile growth has been controlled over different sizes of transistors. It is shown that the exposed Si coverage of the chip is the main parameter in order to maintain control of the layer profile. This has been explained by gas depletion theory of the growth species in tile stationary boundary layer over tile wafer. The control of SiGe layer profile has been obtained over a wide range of device sizes by optimized process parameters in combination with a water pattern design consisting of dummy features causing uniform gas depletion over the chips of the wafer.

  • 331.
    Kolahdouz, Mohammadreza
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hållstedt, Julius
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Wise, R.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Selective Epitaxial Growth with Full Control of Pattern Dependency Behavior for pMOSFET Structures2009In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 156, no 3, p. H169-H171Article in journal (Refereed)
    Abstract [en]

    This study presents a way to design chips to obtain uniform selective epitaxial growth of SiGe layers in p-type metal-oxide-semiconductor field-effect transistor (pMOSFET) structures. The pattern dependency behavior of the growth has been controlled over different sizes of transistors. It is shown that the exposed Si coverage of the chip is the main parameter in order to maintain control of the layer profile. This has been explained by the gas depletion theory of the growth species in the stationary boundary layer over the water. Control of the SiGe layer profile has been obtained over a wide range of device sizes by optimized process parameters in combination with a wafer pattern design consisting of dummy features causing uniform gas depletion over the chips of the wafer.

  • 332.
    Kolahdouz, Mohammadreza
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Maresca, Luca
    KTH, School of Information and Communication Technology (ICT).
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Riley, D.
    Wise, R.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    New method to calibrate the pattern dependency of selective epitaxy of SiGe layers2009In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 53, no 8, p. 858-861Article in journal (Refereed)
    Abstract [en]

    Selective epitaxial growth (SEG) of Si1-xGex layers on patterned substrates containing isolated, grouped and global chips has been investigated. The interaction between chips on a wafer was studied, and the results are explained by kinetic gas theory for CVD techniques. A test pattern was designed with a series of grouped chips to calibrate the pattern dependency of SEG (both growth rate and Ge content). The amount of exposed Si coverage on chips in the test pattern ranged between 0.05 and 37%. The layer profile of the calibration pattern was compared to profiles on wafers having a global chip design. A model was developed to estimate the Ge content on substrates with a global design.

  • 333.
    Kortegaard Nielsen, Hanne
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Capacitance transient measurements on point defects in silicon and silicol carbide2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Electrically active point defects in semiconductor materials are important because they strongly affect material properties like effective doping concentration and charge carrier lifetimes. This thesis presents results on point defects introduced by ion implantation in silicon and silicon carbide. The defects have mainly been studied by deep level transient spectroscopy (DLTS) which is a quantitative, electrical characterization method highly suitable for point defect studies. The method is based on measurements of capacitance transients and both standard DLTS and new applications of the technique have been used.

    In silicon, a fundamental understanding of diffusion phenomena, like room-temperature migration of point defects and transient enhanced diffusion (TED), is still incomplete. This thesis presents new results which brings this understanding a step closer. In the implantation-based experimental method used to measure point defect migration at room temperature, it has been difficult to separate the effects of defect migration and ion channeling. For various reasons, the effect of channeling has so far been disregarded in this type of experiments. Here, a very simple method to assess the amount of channeling is presented, and it is shown that channeling dominates in our experiments. It is therefore recommended that this simple test for channeling is included in all such experiments. This thesis also contains a detailed experimental study on the defect distributions of vacancy and interstitial related damage in ion implanted silicon. Experiments show that interstitial related damage is positioned deeper (0.4 um or more) than vacancy related damage. A physical model to explain this is presented. This study is important to the future modeling of transient enhanced diffusion.

    Furthermore, the point defect evolution in low-fluence implanted 4H-SiC is investigated, and a large number of new defect levels has been observed. Many of these levels change or anneal out at temperatures below 300 C, which is not in accordance with the general belief that point defect diffusion in SiC requires high temperatures. This thesis also includes an extensive study on a metastable defect which we have observed for the first time and labeled the M-center. The defect is characterized with respect to DLTS signatures, reconfiguration barriers, kinetics and temperature interval for annealing, carrier capture cross sections, and charge state identification. A detailed configuration diagram for the M-center is presented.

  • 334.
    Kortegaard Nielsen, Hanne
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Martin, David M
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Svensson, Bengt G
    Department of Physics, Physical Electronics Oslo University,.
    M-center in low-dose proton implanted 4H-SiC; Bistability and change in emission rate2005In: SILICON CARBIDE AND RELATED MATERIALS 2004 / [ed] Nipoti R., Poggi A., Scorzoni A ., 2005, Vol. 483, p. 497-500Conference paper (Refereed)
    Abstract [en]

    4H-SiC schottky diodes have been implanted with 2.5 MeV protons to a dose of 1 x 10(12) cm(-2) and measured by deep level transient spectroscopy (DLTS). Between annealings at 150 ° C and 200 ° C the whole DLTS-spectra shift in temperature, most clearly revealed for the Z and M-center levels. The shift corresponds to a decrease in emission rate at a given temperature by approximately a factor of 5. It is speculated that the reason for this change in emission rate is to be found in the surrounding material rather than in the defects themselves.

  • 335.
    Kortegaard Nielsen, Hanne
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hallén, Anders.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Svensson, Bengt G.
    Department of Physics, Physical Electronics, Oslo University.
    Capacitance transient study of the metastable M center in n-type 4H-SiC.2005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 8Article in journal (Refereed)
    Abstract [en]

    The metastable M center in n-type 4H silicon carbide is studied in detail after it has been introduced by 2.5 MeV proton irradiation with a fluence of 1x10(12) cm(-2). The experimental procedures included deep-level transient spectroscopy, carrier capture coefficient and capacitance versus temperature measurements, and pulse-train measurements. The pulse-train measurements are reproduced by simulations. Three band-gap levels have previously been assigned to the M center: M-1 at E-C-0.42 eV, M-2 at E-C-0.63 eV, and M-3 at E-C-0.83 eV, where E-C is the conduction-band edge. Direct measurements of the majority-carrier capture cross sections show that the cross section values extracted from Arrhenius plots are about two orders of magnitude too large, indicating a large entropy factor. A detailed configuration diagram of the M center is presented, including charge state levels and reconfiguration barriers. Evidence in support of a fourth M center level, not explicitly observed, is presented. Isochronal and isothermal annealing experiments show that the M center anneal out between 310 and 370 degrees C in a process displaying first-order kinetics. The annealing process, which is shown to have an activation energy of 2.0 eV, is identified as dissociation.

  • 336.
    Krenz, René
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Efficient computation of dominators in multiple-output circuit graphs2005In: Proceedings - IEEE International Symposium on Circuits and Systems, 2005, p. 2223-2226Conference paper (Refereed)
    Abstract [en]

    In this paper we present an efficient technique for computing dominators in multiple-output circuit graphs. Dominators provide information about the origin and the end of reconverging paths in a graph. This information is widely used in CAD applications such as satisfiability checking, equivalence checking, ATPG, technology mapping, decomposition of Boolean functions and power optimization. Experiments on a large set of benchmarks show a significant performance improvement of our new technique in comparison to the well-known algorithm for computing dominators in flowgraphs presented by Lengauer and Tarjan. We will demonstrate that in contrast to previous techniques our algorithm obtains performance improvements especially for large benchmarks.

  • 337.
    Krenz, René
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A fast algorithm for finding common multiple-vertex dominators in circuit graphs2005In: ASP-DAC 2005: Proceedings Of The Asia And South Pacific Design Automation Conference, IEEE , 2005, p. 529-532Conference paper (Refereed)
    Abstract [en]

    In this paper we present a fast algorithm for computing common multiple-vertex dominators in circuit graphs. Dominators are widely used in CAD applications such as satisfiability checking, equivalence checking, ATPG, technology mapping, decomposition of Boolean functions and power optimization. State of the art algorithms compute single-vertex dominators in linear time. However, the rare appearance of single-vertex dominators in circuit graphs requires the investigation of a broader type of dominators and the development of algorithms to compute them. We show that our new technique is faster and computes more common multiple-vertex dominators than existing techniques.

  • 338.
    Krenz, René
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dubrova, Elena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Improved Boolean function hashing based on multiple-vertex dominators2005In: ASP-DAC 2005: Proceedings Of The Asia And South Pacific Design Automation Conference, New York: IEEE , 2005, p. 573-578Conference paper (Refereed)
    Abstract [en]

    The growing complexity of today's system designs requires fast and robust verification methods. Existing BDD, SAT or ATPG-based techniques do not provide sufficient solutions for many verification instances. Boolean function hashing is a probabilistic verification approach which can complement existing formal methods in a number of applications such as equivalence checking, biased random simulation, power analysis and power optimization. The proposed hashing technique is based on the arithmetic transform, which maps a Boolean function onto a probabilistic hash value for a given input assignment. The presented algorithm uses multiple-vertex dominators in circuit graphs to progressively simplify intermediate hashing steps. The experimental results on benchmark circuits demonstrate the robustness of our approach.

  • 339. Kreter, A.
    et al.
    Brezinsek, S.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Emmoth, Birger
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Freisinger, M.
    Pelicon, P.
    Philipps, V.
    Schmitz, O.
    Sundelin, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Sergienko, G.
    Deuterium retention in different carbon materials exposed in TEXTOR2007In: 34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts, 2007, no 1, p. 315-318Conference paper (Refereed)
  • 340. Krishnamurthy, S
    et al.
    McGuinness, C
    Dorneles, L S
    Venkatesan, M
    Coey, J M D
    Lunney, J G
    Pattersonb, C H
    Smith, K E
    Learmonth, T
    Glans, P A
    Schmitt, Thorsten
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Guo, J H
    Soft-x-ray spectroscopic investigation of ferromagnetic Co-doped ZnO2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 8, p. 08M111-Article in journal (Refereed)
    Abstract [en]

    The electronic properties of cobalt-doped ZnO were investigated through site-selective and element-sensitive x-ray-absorption spectroscopy in the vicinity of the Co L-2,L-3 edge, the oxygen K edge, and at the Zn L-3 edge. The spectroscopic measurements of the ferromagnetic cobalt-doped ZnO films appear to have additional components in the O K edge x-ray-absorption spectrum not observed in the undoped films. The observed features may derive from both hybridization with unoccupied Co 3d states and also from lattice defects such as oxygen vacancies. Only minor changes in the Zn L-3 edge spectra were observed. These observations are consistent with a polaron percolation model in which the ferromagnetic coupling is mediated by shallow donor electrons trapped in oxygen vacancies and couples the Co atoms substituted on Zn sites in the hexagonal wurtzite ZnO structure.

  • 341.
    Krishnamurthy, Supriya
    et al.
    Swedish Institute of Computer Science.
    El-Ansary, Sameh
    Swedish Institute of Computer Science.
    Aurell, Erik
    KTH, School of Engineering Sciences (SCI), Physics.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A statistical theory of Chord under churn2005In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 3640, p. 93-103Article in journal (Refereed)
    Abstract [en]

    Most earlier studies of DHTs under churn have either depended on simulations as the primary investigation tool, or on establishing bounds for DHTs to function. In this paper, we present a complete analytical study of churn using a master-equation- based approach, used traditionally in non-equilibrium statistical mechanics to describe steady-state or transient phenomena. Simulations are used to verify all theoretical predictions. We demonstrate the application of our methodology to the Chord system. For any rate of churn and stabilization rates, and any system size, we accurately predict the fraction of failed or incorrect successor and finger pointers and show how we can use these quantities to predict the performance and consistency of lookups under churn. We also discuss briefly how churn may actually be of different 'types' and the implications this will have for the functioning of DHTs in general.

  • 342.
    Kristiansen, Joakim
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    QoS Simulation of IP based GSM and EDGE Radio Access Network2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Due to increased popularity and acceptance of mobile communication the data services (i.e., General Packet Radio Services) has become standardized and is now implemented and ready for usage. General Packet Radio Service (GPRS) enables a mobile user to use up to eight time slots in a channel to increase their bitrate during data transmission. Enhanced Data rates for GSM Evolution (EDGE) will increase the bitrate during data transmission even more due to a newer modulation techniques which can be used in a given time slot.

    Both voice calls and data traffic generates signalling to setup and release the sessions for voice calls and data traffic. In an IP based GSM and EDGE Radio Access Network (IP based GERAN) there will be problems to ensure low delay of packets between nodes for voice traffic and signalling traffic. There are different ways to cope with this problem mainly using different scheduling algorithms, like Weighted Fair Queuing (WFQ) and Class Based Queuing (CBQ).

    IP based GERAN using Class Based Queuing was studied using simulation. The first case study different bandwidths for voice traffic and control signalling were examined. In the second case study the voice traffic has higher priority than signalling traffic and in the third case study the voice traffic and control signalling have the same priority. The result is that in the first case the control signalling is affected, but not delayed due to the amount of voice traffic. In the second case the control signalling is affected when voice traffic used more than 60% of the bandwidth and in the third case the control signalling is not affected at all.

    If some of the new protocols (e.g., SIP) are used to carry a voice over IP session from a mobile terminal to a terminal in the Internet it would be desirable to be able to ensure Quality of Service end to end. The ICEBERG project at University of California at Berkeley was examined as an example of a system which is utilizing LAN technology to provide the infrastructure network.

  • 343.
    Kristiansson, Klas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Future Network Management2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this MS. thesis is to examine and propose how a future telecommunications management network can be built in a scalable, cost-efficient manner at the same time as high security is maintained. The project was done for Ki Consulting and Skanova. Skanova’s management networks have been described and the problem areas of the current system have been identified. The problem with the current situation involves complex and complicated communications between existing management networks. This thesis proposes four different solutions for future network management. These solutions are (1) continuing with today’s network management, (2) using only one of Skanova’s networks for network management, (3) building a new IP network for network management, or (4) using an existing IP network for network management. The different management networks are compared with respect to the following parameters: investment costs, operating costs, access security, operating security, flexibility, and scalability. An IP network is suggested for handling all network management in the future.

  • 344. Kumar, R. T. R.
    et al.
    Badel, X.
    Vikor, G.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schuch, R.
    Fabrication of silicon dioxide nanocapillary arrays for guiding highly charged ions2005In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 16, no 9, p. 1697-1700Article in journal (Refereed)
    Abstract [en]

    This paper demonstrates the fabrication of a membrane permeated by a silicon dioxide nanocapillary array for manipulating highly charged ions at the nanoscale. The fabrication method involves (i) the formation of pores at the nanoscale on lithographically patterned, n-type silicon using photo-assisted electrochemical etching, followed by (ii) thermal oxidation, (iii) bulk silicon back etching and (iv) oxide etching using silicon micromachining technology. The electrochemical etching parameters were chosen to form arrays of straight pores with a diameter of about 250 nm, a length of 30 mu m and interpore distances of I and 1.4 mu m. The back side of the pore arrays was etched in potassium hydroxide and tetramethyl ammonium hydroxide. Finally, the inside of the pores was thermally oxidized to yield SiO2 capillary arrays. The present method could allow the fabrication of capillaries with further smaller dimensions by increasing the thermally grown oxide thickness.

  • 345.
    Kundozerova, Tatyana V.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Stefanovich, G. B.
    Velichko, A. A.
    Anodic Nb2O5 Nonvolatile RRAM2012In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 59, no 4, p. 1144-1148Article in journal (Refereed)
    Abstract [en]

    We report nonvolatile resistive switching in anodic niobium pentoxide thin-film memory cells. Highly dielectric Nb2O5 films were prepared at room temperature by the anodic oxidation of submicrometer-thick Nb films sputtered onto an Si wafer. After the electroforming process, Au/Nb2O5/Nb/Si sandwich memory cells demonstrate reproducible direct current and pulse mode switching between two resistance states with a resistance ON-OFF ratio around 10(3). Low and high resististive states show ohmic conductivity and field-assisted Poole-Frenkel-type conductivity, respectively. Nonvolatile resistance storage was traced within 40 days to quantify retention characteristics of the Nb2O5 memristor. The low-temperature anodic oxidation of Nb was found to be feasible to fabricate high-density cross-point memory with 3-D stack structures.

  • 346.
    Kämpe, Andreas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Voltage controlled oscillators for wideband redeivers2005Licentiate thesis, comprehensive summary (Other scientific)
  • 347.
    Kämpe, Andreas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A differentially tuned varactor for high common mode rejection2005Conference paper (Other academic)
  • 348.
    Kämpe, Andreas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    A DVB-H receiver architecture2005In: Norchip 2005, Proceedings, NEW YORK: IEEE , 2005, p. 265-268Conference paper (Refereed)
    Abstract [en]

    This paper proposes an integrated DVB-H receiver architecture. The main focus has been low power consumption, aiming at handheld battery operated devices. The total power consumption for the RF tuner is estimated to be less than 20 in W with a duty cycle of 10%. The receiver uses a low-IF architecture and cover the receive bands from 470 MHz to 702 MHz, with an IF of 4.57 MHz. The proposed receiver meets the DVB-H requirements. The, sensitivity is -88 dBm, the noise figure 5.7 dB and the Adjacent Channel Protection Ratio (ACPR) is -51 dB.

  • 349.
    Kämpe, Andreas
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    An LC-VCO with one octave tuning range2005In: Proceedings of the 2005 European Conference on Circuit Theory and Design, Cork, 2005, Vol. 3, p. 321-324Conference paper (Refereed)
    Abstract [en]

    This paper presents a fully integrated low power and low phase-noise VCO, having a tuning range over one octave (1.2 GHz to 2.5 GHz). The architecture is fully differential and the differential tuning offers a common-mode rejection of 31 dB. The VCO is implemented in a 0.18µm CMOS process using a 1.8 V supply. The circuit, including the bias, consumes only 11.6 mW at 1.2 GHz oscillation frequency, the phase-noise is -129 d Be/Hz at 1 MHz frequency offset.

  • 350.
    Laghaout, Amine
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Feasibility of Bell tests with the W state2010In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 81, no 3Article in journal (Refereed)
    Abstract [en]

    The feasibility of Bell tests depends to a large extent on the tradeoff of difficulty between the preparation and the measurement of entangled systems. Polarization-entangled systems, though easy to measure, pose a relative challenge in their preparation. The opposite holds with entangled energy eigenstates for which the preparation is relatively straightforward. A way to perform measurements using a photodetector along the x, y, and z axes (in a Bloch sphere picture) on such Fock-state qubits shall be worked out, taking the W state as our entangled system. This will, by the same token, allow us to determine the minimum quantum efficiency required to perform a conclusive Bell test with the W energy eigenstate.

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