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  • 201.
    Duo, Xinzhong
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Torikka, Tommi
    Zheng, Li-Rong
    KTH, Superseded Departments, Electronic Systems Design.
    Ismail, Muhammed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu
    KTH, Superseded Departments, Electronic Systems Design.
    Tjukanoff, Esa
    A DC-13GHz LNA for UWB RFID applications2004In: 22ND NORCHIP CONFERENCE, PROCEEDINGS, 2004, p. 241-244Conference paper (Refereed)
    Abstract [en]

    In this paper, we present a 4-stage traveling wave lownoise amplifier for UWB RFID (ultra-wideband radiofrequency identification). This LNA covers a frequencyrange of DC - 13 CHz. The circuit is implemented with0.I5pm GaAs PHEMT chips embedded in flexible LCP(liquid crystal polymer) substrate. In the frequency range,the gain of the LNA is better than IO dB, fluctuation of thegain is less than 3dB, its noise figure is less than 4dB, SI 1and S22 are around -10 dB.

  • 202.
    Duo, Xinzhong
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Zheng, Li-Rong
    KTH, Superseded Departments, Electronic Systems Design.
    Ismail, Muhammad
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu
    KTH, Superseded Departments, Electronic Systems Design.
    On-chip versus Off-chip Passives Trade-offs in Radio and Mixed-Signal System-on- PackageManuscript (preprint) (Other academic)
  • 203.
    Duo, Xinzhong
    et al.
    KTH, Superseded Departments, Electronic Systems Design.
    Zheng, Li-Rong
    KTH, Superseded Departments, Electronic Systems Design.
    Ismail, Muhammed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu
    KTH, Superseded Departments, Electronic Systems Design.
    Analysis of lossy packaging parasitics for common emitter LNA in system-on-package2004In: ELECTRICAL PERFORMANCE OF ELECTRONIC PACKAGING, NEW YORK: IEEE , 2004, p. 75-78Conference paper (Refereed)
    Abstract [en]

    Advances of VLSI and packaging technologies enable condensed integration of an RF system in a single module, known as SoC and SoP. In order to find a better solution between SoC and SoP for RF systems and their sub-systems, it is needed to predict and estimate performance of each solution. In this paper, analytical equations for noise figure and gain of inductively degenerated common-emitter low-noise amplifiers in SoP/SoC are deduced as functions of passives and packaging parasitics. They hence enable designers to evaluate overall performance of each solution quantitatively. As well, influence of lossy packaging parasitics on LNA is also analyzed.

  • 204.
    Duo, Xinzhong
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zheng, Li-Rong
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu R.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A study of packaging Requirements Multi-Band/Multi-Standard Wireless Chips2002In: Proc. IEEE 20th Norship Conference, 2002, p. 285-290Conference paper (Refereed)
  • 205.
    Duo, Xinzhong
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zheng, Li-Rong
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu R.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Chip-package co-design of common emitter LNA in system-on-package with on-chip versus off-chip passive component analysis2003In: ELECTRICAL PERFORMANCE OF ELECTRONIC PACKAGING, NEW YORK: IEEE , 2003, p. 55-58Conference paper (Refereed)
    Abstract [en]

    In this paper, we present common emitter LNAs (low noise amplifiers) in system-on-package for 5GHz WLAN application. Innovation of this module is that it is chip-package co-designed and co-simulated with performance trade-offs for on-chip versus off-chip passive component integration. It thus provides an optimal total solution for embedded RF electronics in system-level integration. Analytical equations for key performance parameters, noise figure and gain, of these LNAs are developed as functions of quality factors of passive components and the package parasitics. They hence provide designers a quantitative trade-off for on-chip versus off-chip passive components integration in SoP design. The final module is composed of on-chip active components in 0.5mum SiGe BiCMOS technology and off-chip passive components integrated in MCM-D substrate. Significant improvement in performance is found in these co-designed LNAs than those in single-chip LNAs.

  • 206.
    Duo, Xinzhong
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zheng, Li-Rong
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu R.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Modeling and simulation of spiral inductors in wafer level packaged RF/wireless chips2003In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 34, no 1, p. 39-47Article in journal (Refereed)
    Abstract [en]

    In this paper, embedded rectangular spiral inductors on Wafer-Level Packaged (WLP) RF/wireless chips were studied with 3D (three-dimensional) EM (electromagnetic) simulations. The performance of spiral inductors fabricated with various geometrical and technological parameters was analyzed. It is shown that Q (the quality factor) and f(res) (the self-resonance frequency) could be improved by using the thick insulator layer and thick/wide metal line, which are fabricated by WLP technology. The value of Q could be over 60 at 20 GHz for such embedded components, attesting a significant improvement compared to the conventional on-chip counterparts in CMOS. Through this study, optimal structures for such components are identified and guidelines for design and fabrications are derived. Finally, a method to estimate the inductance of rectangle spiral inductors is developed. It is useful to determine the approximate structure of an inductor quickly before detailed 3D EM simulation, which may cost a long time.

  • 207.
    Duo, Xinzhong
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zheng, Li-Rong
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Tenhunen, Hannu R.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Chen, Liu
    Zou, Gang
    Liu, Johan
    Design and implementation of a 5GHz RF receiver front-end in LCP based system-on-package module with embedded chip technology2003In: ELECTRICAL PERFORMANCE OF ELECTRONIC PACKAGING, 2003, p. 51-54Conference paper (Refereed)
    Abstract [en]

    In this paper, we present a receiver front-end for 5 GHz wireless LAN in novel LCP (liquid crystal polymer) based system-on-package module. The module is based on embedded chip technologies for system-on-package, which eliminates the constraints of off-chip pad drive capability and hence improves electrical performance. Furthermore, the novel LCP material shows excellent RF and microwave performance. The quality factors of key passive components such as inductors integrated in LCP substrate with thin film technologies is as high as 60. The insertion loss of the bandpass filter is 3dB. The conversion gain of the receiver front-end is 20 dB and occupies 8.7mm by 3.6mm area.

  • 208.
    Dán, György
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Traffic Control for VBR Video in Packet Switched Networks2004Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The best effort service offered by the Internet is notsatisfactory for the transmission of loss and delay sensitivedata, such as real-time voice and video. In order to provideservice guarantees at reasonably high load levels, additionalcontrol functions haveto be employed in the network. Theintroduction of these functions is a critical issue, as severalaspects have to be taken into account, like scalability,economic feasibility and compliance with the end-to-endargument, one of the basic principles underlying the currentInternet architecture. To fulfill these requirements controlfunctions should be put at the network edge, while the core ofthe network should be kept simple to maintain the flexibilityof the network.

    The endpoint measurement-based admission control schemesproposed recently follow this principle. Most of theseadmission control schemes, however, suffer from limitedgranularity, namely, the QoS guarantees (packet loss, delay anddelay jitter) within a service class are the same for allstreams. Quality differentiation thus either requires qualityspecific service classes, which is in contradiction to theend-to-end argument, or the use of additional traffic controlfunctions at the network edge.

    Such additional control functions can decrease the packetloss probability given by the admission control to a levelrequired by the application by introducing additional delay.Delay limited shaping can be used to decrease the burstiness ofthe streams and thus their packet loss probability at the priceof increased delay. Forward error correction can be used torecover from losses within the network while incurringincreased delay and some overhead.

    This thesis gives an evaluation of how the different controlfunctions can work together to improve transmission quality,and thus the perceived visual quality. The effects of the jointuse of the control functions shaping and forward errorcorrection are evaluated, and the optimal allocation of thedelay is investigated. An exact mathematical model of thepacket loss process for multimedia traffic is presented, andits applicability is evaluated.

  • 209.
    Dán, György
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fodor, Viktoria
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    On the efficiency of shaping live video streams2002In: Proceedings of the 2002  international symposium on performance evaluation of computer and telecommunications systems, 2002Conference paper (Refereed)
    Abstract [en]

    In this work the efficiency of shaping live video streams is considered. We propose low complexity shaping algorithms adequate for real-time operation and supporting applications with a wide range of delay tolerance. The effect of shaping is investigated considering video streams multiplexed at an output link with a small buffer to absorb packet scale congestion. The advantage of using small buffers when transmitting video streams is the limited delay and delay variation. Consequently, we concentrate on the loss characteristics to evaluate the performance of the proposed solutions. We present mathematical analysis based on fluid flow modeling and the theory of large deviations and confirm the results with simulation.

  • 210.
    Dán, György
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fodor, Viktoria
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Quality differentiation with source shaping and forward error correction2003In: Interactive Multimedia On Next Generation Networks / [ed] Ventre, G; Canonico, R, 2003, p. 222-233Conference paper (Refereed)
    Abstract [en]

    The transmission of video traffic over the Internet is a fundamental issue of network design. Video applications require quality of service guarantees from the network in terms of limited packet loss, end-to-end delay, and delay variation. The question of today's research and development is how to provide these guarantees considering the architecture of the present Internet. In the last years a variety of admission control schemes based on per-hop or end-to-end measurements has been suggested to control delay and loss sensitive streams with very little or no support at the routers. Most of these solutions, however, have to apply the same acceptance threshold for all streams, a significant limitation considering the diverse quality requirements of the applications. In this work we investigate how source shaping and forward error correction (FEC) can be used together to achieve application specific quality differentiation in terms of end-to-end delay and packet loss probability. While source shaping and FEC have been proposed independently to decrease the probability of packet loss due to buffer overflow, their joint use has not been studied before. As the two control functions use the same scarce resource, end-node delay, and their efficiency to decrease loss probability is proportional to the introduced delay but with a decreasing marginal gain, combining the two a better performance can be achieved than by using only one of them. The performance evaluation focuses on the optimal delay allocation for shaping and FEC, such that the loss probability is minimized. We investigate how shaping can be used to substitute FEC redundancy and the sensitivity of the quality differentiation to the background traffic characteristics.

  • 211.
    Dán, György
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fodor, Viktoria
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Analysis of the Packet Loss Process for Multimedia Traffic2004In: Intl. Conference on Telecommunication Systems Modeling and Analysis, 2004Conference paper (Refereed)
    Abstract [en]

    In the case of multimedia traffic, like VBR video, the average loss probability is not sufficient to investigate the effects of loss on perceived visual quality, but it is difficult to analytically model the queuing behavior for such traffic. It has been shown that in the case of realtime communications, for which small buffers are used for delay reasons, short range dependence dominates the loss process and so the Markovmodulated Poisson process (MMPP) might be a reasonable source model. In this paper we present an exact mathematical model for the loss process of an MMPP+M/D/1/K queue; we validate it via simulations and compare it to other mathematical models, like the MMPP+M/M/1/K and the Gilbert model, and to simulations with real MPEG-4 video traces. We conclude that the other models give accurate results only in a small set of network scenarios, while our model can capture the loss process of VBR video sufficiently well in most cases. This makes it possible to analyze the effects of forward error correction on transmission quality in various network scenarios.

  • 212.
    Düring, Morgan
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Lindvall, Stefan
    Mehlqvist, Dan
    Öberg, Johnny
    The ProGram Compiler2003In: University Booth, DATE 2003 conference, 2003Conference paper (Refereed)
  • 213.
    Düring, Morgan
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Öberg, Johnny
    Implementation of Revolver Type Processor Using Grammar-based Methodology2002In: Proceedings of the 2nd Swedish System on Chip conference, 2002Conference paper (Refereed)
  • 214. Edmonds, K. W.
    et al.
    Binns, C.
    Baker, S. H.
    Maher, M. J.
    Thornton, S. C.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Brookes, N. B.
    Magnetism of exposed and Co-capped Fe nanoparticles2000In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 220, no 1, p. 25-30Article in journal (Refereed)
    Abstract [en]

    The effect of capping a dilute assembly of nanoscale mass-selected Fe clusters with a Co thin film has been studied using X-ray magnetic circular dichroism (XMCD). The clusters, containing around 400 atoms, were deposited in situ from a gas-aggregation source onto highly oriented pyrolytic graphite. The exposed clusters possess magnetic moments that are enhanced compared to the bulk, by around 4% for m(spin) and around 75% for m(orb). In addition, a surface core level shifted component is observed in the L-3.2 XMCD spectrum. Upon adding the Co layer, the surface component disappears, m(orb) is decreased for the Fe clusters, and m(spin) increases. The exposed clusters are magnetically isotropic but a strong in-plans anisotropy is observed after depositing the Co overlayer. We attribute this to the shape of the Co islands in which the Fe clusters are embedded.

  • 215. Edmonds, K. W.
    et al.
    Binns, C.
    Baker, S. H.
    Maher, M. J.
    Thornton, S. C.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Brookes, N. B.
    Size dependence of the magnetic moments of exposed nanoscale iron particles2001In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 231, no 1, p. 113-119Article in journal (Refereed)
    Abstract [en]

    The magnetic moments in exposed, mass-selected, nanoscale Fe clusters in the size range 1.89-2.20 nm (300-475 atoms), deposited onto graphic in situ have been measured by X-ray magnetic circular dichroism. The smallest clusters possess moments that are enhanced by around 4% for m(spin) and 80% for m(orb) and decrease towards the bulk value with increasing size. The larger clusters show an in-plane anisotropy that is consistent with the anisotropy in the orbital moment. The smallest clusters are, within experimental error, magnetically isotropic. The anisotropy constant in the 475-atom clusters is significantly higher than the bulk value.

  • 216. Eklöf, Martin
    et al.
    Sparf, Magnus
    Moradi, Farshad
    Ayani, Rassul
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Peer-to-peer-based resource management in support of HLA-based distributed simulations2004In: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 80, no 4-5, p. 181-190Article in journal (Refereed)
    Abstract [en]

    In recent years, the concept of peer-to-peer computing has gained renewed interest for sharing resources within and between organizations or individuals. This article describes a decentralized resource management system (DRMS) that uses a network of workstations for the execution and storage of high-level architecture (HLA) federations/federates in a peer-to-peer environment. The implementation of DRMS is based on the open-source project JXTA, which represents an attempt to standardize the peer-to-peer domain. DRMS is part of a Web-based simulation environment supporting collaborative design, development, and execution of HLA federations. This study evaluates the possibilities of using peer-to-peer technology for increasing the reuse and availability of simulation components within the defense modelling and simulation community. More specifically, it addresses the necessary adjustments of simulation components to conform to the requirements of the DRMS and shows that JXTA could provide the foundation for a distributed system that increases the possibilities for reusing simulation components.

  • 217.
    El-Ansary, Sameh
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A framework for the understanding, optimization and design of structured peer-to-peer systems2003Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Peer-to-Peer (P2P) computing is a recent hot topic in theareas of networking and distributed systems. Work on P2Pcomputing was triggered by a number of ad-hoc systems that madethe concept popular. Later, academic research e orts started toinvestigate P2P computing issues based on scientificprinciples. Some of that research produced a number ofstructured P2P systems that were collectively referred to bythe term"Distributed Hash Tables" (DHTs). However, theresearch occurred in a diversified way leading to theappearance of similar concepts yet lacking a commonperspective.

    In this thesis we present a number of papers representingour reseach results in in the area of DHT systems as thestate-of-theart P2P systems. The contribution of this thesis isthreefold. (i) We present the principle of distributed k-arysearch (DKS) and argue that it serves as a framework for mostof the recent P2P systems known as DHTs. That is, given the DKSframework, understanding existing DHT systems is done simply byseeing how they are instances of that framework. (ii) We arguethat by perceiving systems as instances of the DKS framework,one can optimize some of them. We illustrate that by applyingthe framework to the Chord system, one of the most establishedDHT systems. (iii) We show how the DKS framework helps in thedesign of P2P algorithms by two examples: (a) A broadcastalgorithm that takes advantage of the distributed k-ary searchtree (b) The DKS(n; k; f) system which is a system designedfrom the beginning on the principles of distributed k-arysearch.

  • 218.
    El-Ansary, Sameh
    et al.
    Distributed Systems Lab, SICS-Swedish Institute of Computer Science.
    Aurell, Erik
    KTH, Superseded Departments, Physics.
    Brand, Per
    Distributed Systems Lab, SICS-Swedish Institute of Computer Science.
    Haridi, Seif
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Experience with a physics-style approach for the study of self properties in structured overlay networks2004In: SELF-STAR: International Workshop on Self-* Properties in Complex Information Systems, May 2004, Bertinoro, Italy, 2004Conference paper (Other academic)
    Abstract [en]

    This paper gives a brief summary of our experience in applying a physics-style approach for analyzing the behavior of structured overlay networks that deploy self-organization and self-repair policies. Such systems are not always simple to model analytically and simulation of scales of interest can be prohibitive. Physicists deal with scale by characterizing a system using intensive variables, i.e. variables that are size independent. The approach proved its substantial usefulness when applied to satisfiability theory and it is the hope that it can be as useful in the field of large-scale distributed systems. We report here our finding of one simple self-organization-related intensive variable, and a more complex self-repair-related intensive variable.

  • 219.
    El-Ansary, Sameh
    et al.
    Distributed Systems Laboratory, SICS Swedish Institute of Computer Science.
    Krishnamurthy, Supriya
    Distributed Systems Laboratory, SICS Swedish Institute of Computer Science.
    Aurell, Erik
    KTH, Superseded Departments, Physics.
    Haridi, Seif
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    An Analytical Study of Consistency and Performance of DHTs under Churn2004Report (Other academic)
    Abstract [en]

    In this paper, we present a complete analytical study of dynamic membership (aka churn) in structured peer-to-peer networks. We use a master-equation-based approach, which is used traditionally in non-equilibrium statistical mechanics to describe steady-state or transient phenomena. We demonstrate that this methodology is infact also well suited to describing structured overlay networks by an application to the Chord system. For any rate of churn and stabilization rates, and any system size, we accurately account for the functional form of: the distribution of inter-node distances, the probability of network disconnection, the fraction of failed or incorrect successor and finger pointers and show how we can use these quantities to predict both the performance and consistency of lookups under churn. Additionally, we also discuss how churn may actually be of different 'types' and the implications this will have for structured overlays in general. All theoretical predictions match simulation results to a high extent. The analysis includes details that are applicable to a generic structured overlay deploying a ring as well as Chord-specific details that can act as guidelines for analyzing other systems.

  • 220.
    El-Ansary, Sameh
    et al.
    Swedish Institute of Computer Science.
    Onana Alima, Luc
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Brand, Per
    Swedish Institute of Computer Science.
    Haridi, Seif
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A Framework for Peer-To-Peer Lookup Services based on k-ary search2002Report (Other academic)
    Abstract [en]

    Locating entities in peer-to-peer environments is a fundamentaloperation. Recent studies show that the concept of distributed hash table can be used to design scalable lookup schemes with good performance (i.e. small routing table and lookup length). In this paper, we propose a simple framework for deriving decentralized lookup algorithms. The proposed framework is simple in that it is based on the well-known concept of k-ary search. To demonstrate the applicability of our framework, we show how it can be used to instantiate Chord. When deriving a generalized Chord from our framework, we obtain better performance in terms of the routing table size (38% smaller than the generalization suggested by the Chord authors).

  • 221.
    El-Ansary, Sameh
    et al.
    Swedish Institute of Computer Science.
    Onana Alima, Luc
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Brand, Per
    Swedish Institute of Computer Science.
    Haridi, Seif
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Efficient broadcast in structured P2P networks2003In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 2735, p. 304-314Article in journal (Refereed)
    Abstract [en]

    In this position paper, we present an efficient algorithm for performing a broadcast operation with minimal cost in structured DHT-based P2P networks. In a system of N nodes, a broadcast message originating at an arbitrary node reaches all other nodes after exactly N - 1 messages. We emphasize the perception of a class of DHT systems as a form of distributed k-ary search and we take advantage of that perception in constructing a spanning tree that is utilized for efficient broadcasting. We consider broadcasting as a basic service that adds to existing DHTs the ability to search using arbitrary queries as well as dissiminate/collect global information.

  • 222.
    Elek, Viktoria
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fumagalli, A.
    Wedzinga, G.
    Photonic slot routing: A cost-effective approach to designing all-optical access and metro networks2001In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 39, no 11, p. 164-172Article in journal (Refereed)
    Abstract [en]

    In the backbone network, the high level of traffic aggregation achieved by numerous users is efficiently served by means of optical circuit switched solutions - the so-called wavelength routing approach. In the access and metro networks, on the contrary, the reduced level of traffic aggregation makes wavelength routing solutions inadequate. The finer and more dynamic bandwidth allocation provided by packet-interleaved optical time-division multiplexing is thus advocated in these network areas. This article presents a survey of an OTDM approach, known as photonic slot routing, or PSR for short. It will be illustrated how this approach may provide a cost-effective solution to deploying all-optical access and metro networks with today's technology.

  • 223. Ellervee, P.
    et al.
    Miranda, M.
    Catthoor, F.
    Hemani, Ahmed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    System-level data-format exploration for dynamically allocated data structures2001In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, ISSN 0278-0070, E-ISSN 1937-4151, Vol. 20, no 12, p. 1469-1472Article in journal (Refereed)
    Abstract [en]

    System-level exploration of memory organizations is a key issue in successful implementation of data dominated applications based on dynamically allocated data structures involving records and access keys. This paper presents a formalized technique for exploring different memory data-format alternatives when only the system level functional behavior of the application has been defined. Our data-format exploration approach allows to substantially minimize the number of accessed bits by rearranging the format of the data records. The technique exploits parallelism in the data transfer by analyzing the dependencies between data-record accesses. As a result, significant reduction in memory size, bandwidth, and power are obtained. We have validated our techniques using several real-life asynchronous transfer mode cell processing applications, where we have obtained reductions in memory size (up to 20%), power (up to a 60%), and bandwidth.

  • 224.
    Ellervee, Peeter
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Miranda, Miguel
    IMEC.
    Catthoor, Francky
    IMEC, Katholieke Universiteit.
    Hemani, Ahmed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    System-level data format exploration for dynamically allocated data structures2000In: Design Automation Conference, 2000. Proceedings 2000. 37th, 2000, p. 556-559Conference paper (Refereed)
    Abstract [en]

    Not available

  • 225.
    Ellervee, Peeter
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Miranda, Miguel
    IMEC.
    Catthoor, Francky
    IMEC, Katholieke Universiteit.
    Hemani, Ahmed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    System-level data-format exploration for dynamically allocated data structures2001In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, ISSN 0278-0070, E-ISSN 1937-4151, Vol. 20, p. 1469-1472Article in journal (Refereed)
  • 226.
    Emmoth, Birger
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Wienhold, P.
    Rubel, Marek J.
    KTH, Superseded Departments, Alfvén Laboratory.
    Schweer, B.
    Zagorski, R.
    Particle collection at the plasma edge by a fast reciprocating probe at the TEXTOR tokamak2003In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 313, p. 729-733Article in journal (Refereed)
    Abstract [en]

    A fast reciprocating probe system capable of transferring different types of heads has been constructed and implemented at the TEXTOR tokamak for diagnosing the plasma edge. It gives the possibility of using a particle collector technique to extend studies of material transport from the scrape-off layer to the near plasma edge. For the first time, the system was used for exposures of graphite samples (pure and coated with a-C:H or W) at positions both within and outside the last closed flux surface. Various surface analysis methods were applied to investigate the probe morphology and, by this, to determine radial deposition profiles of boron impurities and deuterium. The profiles for boron are remarkably flat whilst those for deuterium are characterised by a steep decay with the e-folding length of approximately 15 mm. On tungsten-coated samples almost no deuterium was found, most likely because of little carbon co-deposition, shallow implantation and low trapping coefficient of deuterons in the tungsten layer. Reconstruction of experimental results by means of a multifluid TECXY code helped to identify the contribution of impurity sources (limiters, wall) to the observed radial distribution of species.

  • 227.
    Erdal, Suvar
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Haralson, Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Radamson, Henry H.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Wang, Yong-Bin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Malm, B. Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    High frequency performance of SiGeCHBTs with selectively & non-selectively grown collector2004In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T114, p. 138-141Article in journal (Refereed)
    Abstract [en]

    Two high-frequency heterojunction bipolar transistor (HBT) architectures based on SiGeC have been fabricated and characterized. Different collector designs were applied either by using selective epitaxial growth doped with phosphorous or by non-selective epitaxial growth doped with arsenic. Both designs have a non-selectively deposited SiGeC base doped with boron and a poly-crystalline emitter doped with phosphorous. Both HBT designs exhibit similar electrical characteristics with a peak DC current gain of around 1600 and a BVCEO of 1.8V. The cut-off frequency (f(T)) and maximum frequency of oscillation (f(max)) vary from 40-80 GHz and 15-30 GHz, respectively, depending on lateral design relations. Good high frequency performance for a device with a selectively grown collector is demonstrated for the first time.

  • 228.
    Escudero Pascual, Alberto
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Anonymous and untraceable communications: location privacy in mobile internetworking2001Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Data protection and privacy is rapidly becoming one of themost important issues on the Internet today. Larger number ofInternet sites are collecting personal information from usersthrough forms, cookies, online registrations, or surveys thanever before. New commercial services are springing up that canexploit the ability of mobile communication service providersto determine the geographic location of their users. The newwireless technologies offer mobility; at the same time theyofferlocation informationthat is being used to provide newlocation-aware services.

    This licentiate thesis concerns our experience building anew innovative network environment at the IT-University (RoyalInstitute of Technology). It explains how we present the newsecurity challenges that a wireless network raises togetherwith how we confronte and investigate a new form of problemthis type of network presents, namely location privacy.

    The focus of this work has been on trying to provideunlinkability between the location of wireless users and theiractivities in the Internet. The thesis includes a protocolextension to a pseudonymous IP network architecture developedby the Canadian company Zero Knowledge Systems Inc. called theFreedom System. The proposed extension to Freedom Systempermits a mobile client to seamlessly roam among IP subnetworksand media types whilst being untraceable. By untraceable in thecontext of this thesis we mean the capability of a mobile nodeto concealthe relation between location and personal identifiableinformationfrom third parties whilst the user is on themove. This thesis is composed of four published papers wherethe main results are presented.

  • 229.
    Escudero-Pascual, Alberto
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Privacy in the next generation Internet. Data proection in the context of European Union policy2002Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    With the growth in social, political and economic importanceof the Internet, it has been recognized that the underlyingtechnology of the next generation Internet must not only meetthe many technical challenges but must also meet the socialexpectations of such a pervasive technology. As evidence ofthe strategic importance of the development of the Internet,the European Union has adopted a communication to the Counciland the European Parliament focusing on the next generationInternet and the priorities for action in migrating to the newInternet protocol IPv6 andalso a new Directive (2002/58/EC) on'processing of personal data and protection of privacy in theelectronic communication sector'. The Data Protection Directiveis part of a package of proposals for initiatives which willform the future regulatory framework for electroniccommunications networks and services. The new Directive aims toadapt and update the existing Data ProtectionTelecommunications Directive (97/66/EC) to take account oftechnological developments. However, it is not well undersoodhow this policy and the underlying Internet technology can bebrought into alignment.

    This dissertation builds upon the results of my earlierlicentiate thesis by identifying three specific, timely, andimportant privacy areas in the next generation Internet: uniqueidentifiers and observability, privacy enhanced location basedservices, and legal aspects of data traffic.

    Each of the three areas identified are explored in the eightpublished papers that form this dissertation. The paperspresent recommendations to technical standarization bodies andregulators concerning the next generation Internet so that thistechnology and its deployment can meet the specific legalobligations of the new European Union data protectiondirective.

  • 230.
    Escudero-Pascual, Alberto
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hosein, I.
    Questioning lawful access to traffic data2004In: Communications of the ACM, ISSN 0001-0782, E-ISSN 1557-7317, Vol. 47, no 3, p. 77-82Article in journal (Refereed)
    Abstract [en]

    The debate and issues concerning access to traffic data is discussed. The access to traffic data for law enforcement is a traditional tool for investigation and intelligence gathering. The regulatory environment surrounding technology is transforming after few successes and many missteps. The content, copyright, and cryptography policy processes results in the emergence of technology policy innovations. The concept of Internationalization of policy making, and technology-neural policies are the new innovations along with the involvement of some risk factors.

  • 231.
    Escudero-Pascual, Alberto
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Wireless at KTH. KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Role(s) of a proxy in location based services2002In: 13TH IEEE INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOL 1-5, PROCEEDINGS: SAILING THE WAVES OF THE WIRELESS OCEANS, IEEE , 2002, p. 1252-1256Conference paper (Refereed)
    Abstract [en]

    We examine a number of roles that a proxy server can play in location based services and how it can be used to provide protection of personal identifiable information. Location data, service requests, and privacy policies are encoded in XML by the mobile terminal and forwarded to a proxy server placed between the mobile terminal and the location based service(s). By a suitable architecture in the mobile terminal and in the proxy, we can hide the mobile device's network location, hide the identity of its user, and, in some cases, provide misleading physical location(s). We have applied our privacy model to location information obtained from a GPS receiver. The GPS-based method was chosen as being the only available method where the positioning calculation function (PCF) is fully under the user's control, since the position is calculated within the mobile terminal; other technologies rely on the network infrastructure, and hence some or all of the position data is outside the user's control. A proof of concept was implemented using Fastrax's iTrax02 small, ultra-low power consumption GPS receiver. We illustrate a number of different functions which can be provided by examining some scenarios.

  • 232.
    Espinosa Arronte, Beatriz
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Scaling of the vortex-liquid resistivity in high temperature superconducturs2004Licentiate thesis, comprehensive summary (Other scientific)
  • 233.
    Espinosa-Arronte, Beatriz
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Rapp, Östen
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Andersson, Magnus
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Scaling of the vortex liquid c-axis resistivity in underdoped YBa2Cu3O7-[delta]2004In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 408, p. 583-584Article in journal (Refereed)
    Abstract [en]

     The c-axis resistivity was measured in a twinned, underdoped YBa2Cu3O7-delta (YBCO) single crystal with T-c = 82.2 K. Resistive transition curves for fields Lip to 12 T applied along the c-axis were scaled to one function giving a good scaling. The scaling variable is the same as for the ab resistivity in optimally doped and underdoped YBCO single crystals [Phys. Rev. B 63 (2001) 184511]. This result provides further support to a coherent description of the vortex-liquid resistivity.

  • 234. Fernando, H. N. J.
    et al.
    Canning, J.
    Wosinski, Lech
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jaskorzynska, Bozena
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Dainese, M.
    Characterization of ultra-violet-induced changes in planar waveguides2003In: Journal of Optics. A, Pure and applied optics, ISSN 1464-4258, E-ISSN 1741-3567, Vol. 5, no 4, p. 335-340Article in journal (Refereed)
    Abstract [en]

    A simple, low-cost spectrophotometer system operating in reflection absorption mode is used to characterize changes in refractive index and thickness of thin films under 193 nm irradiation. The results indicate overall dilation of the glass and are confirmed by additional surface topographic measurements. We also show that in addition to the net relaxation from laser annealing of the interface, in germanosilicate samples local compaction takes place. Since the net relaxation is triggered by remote interactions, it is not spatially confined to the laser-irradiated area. However, a local positive index change is observed. These results are in agreement with previous hypotheses put forward to explain planar waveguide negative index changes. They also bring to attention the great care necessary in both conducting and interpreting measurements that do not take into account spatial variations arising from the combination of remote and local triggers of both index and thickness changes.

  • 235.
    Fernando, Harendra
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Fabrication and Charaterisation of Photonic Integrated Circuits2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The past few decades have seen an explosive increase ininformation transfer, fuelled by the enormous growth of theInternet, telecommunication applications, and mass mediasystems in general. Because of the very high bandwidthpotential promised by optical fibre communication technology,the area of all-optical networking has received a great amountof attention. However such systems require very expensiveoptical components for tasks such as (de)multiplexing,switching, and routing. A promising and exciting solution tohandle the ever-increasing demand for capacity with lower costsis to integrate optical elements into one common platform inorder to realize photonic integrated circuits (PICs), or planarlightwave circuits (PLCs). More versatile devices with greaterfunctionality for future all-optical networks are feasible withmonolithic integration of opto-electronic and semiconductorcomponents, which require very specialised low-temperatureprocessing techniques.

    This thesis presents the development of new techniques andmethodologies utilized in low temperature photonic devicefabrication, which can be used to facilitate integration oftemperature sensitive elements. The three-fold contributions tothe thesis are as follows. First, a low temperature plasmaenhanced chemical vapour deposition (PECVD) technology for therealization of silica-on-silicon photonic devices is developed.This technique readily lends itself to the monolithicintegration of devices such as planar optical amplifiers, lightsources, detectors and modulators. Absorption bands around1.48-mm and 1.51-mm wavelengths caused by N-H and Si-H bonds,respectively, had previously been thought to be intrinsic tothe PECVD deposition method when using N2O as the oxidant ofSiH4 and other dopings. The traditional method to eliminatethese absorption bands was high temperature (>10000C)annealing that seriously hinders device integration. Animportant achievement in this thesis is the completeelimination of these two absorption peaks while keeping thewhole fabrication process below 3000 C, and yet maintaining ahigh deposition rate.

    Second, optimisation of techniques in the device fabricationprocess flow and reports on the fabrication of state-of-the artdevices are presented. Important process steps in thefabrication of optical integrated devices such asphotolithography for patterning and reactive ion etching (RIE)in an inductively coupled plasma (ICP) reactor were alsodeveloped. These technologies were then applied to fabricatecomponents that implemented various concepts, such asMMI-couplers and -splitters, or state-of-the-art arrayedwaveguide gratings (AWG) based optical (de)multiplexers.

    Finally, applications of UV-processing on planar technologyare examined. Investigations of the UV-response on PECVDdeposited silica-on-silicon and germanosilicate systems arereported. UV-trimming was shown to be a versatile method toselectively control polarisation birefringence of devices. Atransmission dip of 47dB in a Bragg-grating imprinted on astraight channel waveguide was achieved without hydrogenloading, which led to a record for this simplified processflow. With the Bragg-grating inscription techniques, a novelconcept of a MMI based planar optical Add-Drop (de)multiplexerwas realised.

    The investigations carried out in this thesis show thatPECVD technology can provide low-loss and UV-sensitive materialsuitable for realising a variety of low-cost integrated devicesfor future all-optical networks.

    Keywords:Photonic integrated circuits,silica-on-silicon technology, plasma process, PECVD deposition,reactive ion etching, inductively coupled plasma (ICP),photolithography, planar devices, UV-photosensitivity, arrayedwaveguide gratings, multi-mode interference couplers, opticalAdd-Drop multiplexers

  • 236.
    Fernando, Harendra
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Canning, J.
    Wosinski, Lech
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jaskorzynska, Bozena
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Engineering UV-photosensitivity in planar lightwave circuits by plasma enhanced chemical vapour deposition2004In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 37, no 20, p. 2804-2809Article in journal (Refereed)
    Abstract [en]

    Ion bombarding conditions were used to modify glass properties in silica-on-silicon systems during plasma enhanced chemical vapour deposition (PECVD). The induced structural modifications in the SiO2/Si system resulted in different photosensitive responses when irradiated by ArF pulsed laser operating at 193 nm wavelength. Fourier transform infrared spectroscopy was used to study the structural modifications triggered by ion bombarding conditions during film growth. The results were further confirmed by additional characterizations with regard to density (etch rate), refractive index and surface topographic measurements. The demonstrated method could be used not only to engineer UV-photosensitivity but also to control and compensate birefringence in planar lightwave devices.

  • 237.
    Ferrini, R.
    et al.
    Ecole Polytech Fed Lausanne, Int Photon & Elect Quant.
    Berrier, Audrey
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Dunbar, L. A.
    Ecole Polytech Fed Lausanne, Int Photon & Elect Quant.
    Houdré, R.
    Ecole Polytech Fed Lausanne, Int Photon & Elect Quant.
    Mulot, Mikaël
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Anand, Srinivasan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    de Rossi, S.
    CNRS, Lab Photon & Nanostruct.
    Talneau, A.
    CNRS, Lab Photon & Nanostruct.
    Minimization of out-of-plane losses in planar photonic crystals by optimizing the vertical waveguide2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 18, p. 3998-4000Article in journal (Refereed)
    Abstract [en]

    A two-dimensional phenomenological approach previously developed for the modeling of out-of-plane losses in low refractive index contrast planar photonic crystals (PPhCs) is used to study the dependence of the different loss terms on the planar waveguide parameters. It is demonstrated that: (i) Losses can be minimized by designing vertical heterostructures optimized for a given technological process and/or for a given hole shape; and (ii) any small reduction of the loss value has a strong impact on the optical performances of PPhC structures.

  • 238. Ferrini, R.
    et al.
    Houdre, R.
    Benisty, H.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Moosburger, J.
    Radiation losses in planar photonic crystals: two-dimensional representation of hole depth and shape by an imaginary dielectric constant2003In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 20, no 3, p. 469-478Article in journal (Refereed)
    Abstract [en]

    Waveguide modes in two-dimensional (2-D) photonic crystals (PhCs) deeply etched through monomode slab waveguides, e.g., AlGaAs/GaAs, GaAs/AlOx, or InP/GaInAsP, suffer from radiation losses that are strongly affected by the air hole depth and shape. The issue of three-dimensional (3-D) out-of-plane losses is addressed analytically by means of an incoherent approximation. Assuming separability both for the dielectric map and for the electric field, this approach is valid for defects such as in-plane microcavities, PhC-based waveguides, bends and couplers. Out-of-plane scattering is translated into an effective imaginary index in the air holes, so that 3-D losses can be cast in a simple 2-D calculation. The case of cylindroconical holes is treated, and the validity of this approach is experimentally confirmed by transmission measurements through simple PhC slabs.

  • 239. Ferrini, R.
    et al.
    Leuenberger, D.
    Mulot, M.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Moosburger, J.
    Kamp, M.
    Forchel, A.
    Anand, Srinivasan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Houdre, R.
    Optical study of two-dimensional InP-based photonic crystals by internal light source technique2002In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 38, no 7, p. 786-799Article in journal (Refereed)
    Abstract [en]

    We present the first optical study of 2-D photonic crystals (PCs) deeply etched in an InP/GaInAsP step-index waveguide. Following the same internal light source approach proposed by Labilloy and coworkers for the investigation of GaAs-based 2-D PCs, transmission measurements through simple PC slabs and 1-D Fabry-Perot (FP) cavities between PC mirrors were performed. Details are given on the experimental setup which has been implemented with respect to the original scheme and adapted to InP-based systems working at 1.5-mum. 2-D plane-wave expansion and finite difference time-domain (FDTD) methods are used to fit the experimental data. Out-of-plane losses were evaluated according to a recently introduced phenomenological model. In spite of the complex hole morphology in the measured samples, preliminary results are presented which indicate the possibility of separating different loss contributions from finite etch depth and hole shape. As for 1-D cavities, both FDTD and classical theory for planar resonators are applied in order to deduce the optical properties of the PC mirrors. The origin of an anomalously high transmission observed inside the stopgap is discussed and arguments are given to demonstrate the need for further modeling efforts when working in the bandgap regime.

  • 240. Finazzi, M.
    et al.
    Ghiringhelli, G.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Brookes, N. B.
    Photon energy dependence of the perpendicular geometry magnetic circular dichroism in the 2p3p3p resonant photoemission from Ni2000In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 12, no 9, p. 2123-2133Article in journal (Refereed)
    Abstract [en]

    The magnetic circular dichroism in the perpendicular geometry of the resonant 2p3p3p photoemission (PE) spectroscopy has been investigated in metallic Ni as a function of the photon energy across the Ni Lj absorption edge. Within the experimental error bars, the photon energy dependence of the PE dichroism signal is the same as the one shown by the magnetic circular dichroism of the corresponding x-ray absorption (XMCD), obtained in the collinear geometry. This is attributed to the fact that, in metal Ni, the orbital [L-z] and dipolar [T-z] moments are smaller than the spin angular moment [S-z]. The latter is the dominating term in both the expressions that give the integrated values of the PE dichroism or XMCD intensities, Although the respective photon energy dependence is very similar, the normalized PE dichroism intensity is a factor similar to 5.6 smaller than the normalized XMCD signal, while only a factor similar to 1.6 is expected from theoretical considerations. This factor is observed even below the L-3 threshold, thus we exclude that the small intensity of the perpendicular geometry dichroism in the Ni 2p3p3p resonant photoemission is due to fast relaxation processes in the intermediate state.

  • 241. Finazzi, M.
    et al.
    Ghiringhelli, G.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Duo, L.
    Tagliaferri, A.
    Ohresser, P.
    Brookes, N. B.
    Multiatomic resonant photoemission spectroscopy on CuO and NiO: Observation of antiresonant behavior2000In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 62, no 24, p. R16215-R16218Article in journal (Refereed)
    Abstract [en]

    The intensity of the O 1s core photoemission peak has been measured for CuO and NiO as the photon energy is scanned across the L-3 absorption edge of the metal ion. In CuO, the O 1s peak shows a typical antiresonant behavior, with a sizable decrease of its cross section at photon energies below the Cu L-3 threshold. No detectable effect is observed for NiO. The CuO data are well reproduced by a multiatom resonant photoemission model based on resonant light scattering.

  • 242. Finazzi, M.
    et al.
    Ghiringhelli, G.
    Tjernberg, Oscar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Ohresser, P.
    Brookes, N. B.
    Radiationless Raman versus Anger behavior at the Cu L-3 resonance of CuO and Cu2O2000In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 61, no 7, p. 4629-4635Article in journal (Refereed)
    Abstract [en]

    We have investigated the behavior of the 2p3p3p and 2p3s3p Anger lines of CuO and Cu2O scanning the photon energy across the Cu L-3 resonance. For both samples, when the excitation energy is below the L-3 resonance, we observe the 2p3p3p and 2p3s3p peaks at constant binding energy. This behavior is typical of nonradiative resonant Raman scattering. If the photon energy is raised above the L-3 maximum, the two samples behave in different ways. In CuO, the Auger peaks are always observed at constant binding energy, while in Cu2O their kinetic energy first reaches a maximum at correspondence with the absorption threshold, and then stabilizes at a value slightly higher than the off-resonance Auger peaks. These differences are interpreted in terms of the different electronic structure of the Auger intermediate state at resonance. In CuO, the intermediate state corresponds to a single 2p(3/2) core hole, with the Cu 3d band completely filled. On the contrary, in Cu2O the intermediate state is represented by the combination of a 2p(3/2) hole with a 4sp electron in strong interaction with the O-2sp valence band. In CuO, for photon energies higher than 1.5 eV above the L-3-edge maximum, the constant binding energy radiationless Raman peaks are accompanied by constant kinetic energy replicas. These are attributed to the relaxation of the Auger intermediate state through electron-hole pair generation across the band gap of the material. Satellites that could be associated to relaxation precesses involving energies smaller than the band gap are not resolved. No variation of the lineshape of the Anger peaks is observed as a function of the sample temperature, indicating that different densities of thermally accessible excitations do not have a strong influence on the recombination process of the core hole.

  • 243.
    Fokine, Michael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Photosensitivity, chemical composition gratings and optical fiber based components2002Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The different topics of this thesis include high-temperaturestable fiber Bragg gratings, photosensitivity and fiber basedcomponents.

    Fiber Bragg gratings (FBG) are wavelength dispersiverefractive index structures manufactured through UV exposure ofoptical fibers. Their applications range from WDM filters,dispersion compensators and fiber laser resonators fortelecommunication applications to different types of point ordistributed sensors for a variety of applications.

    One aim of this thesis has been to study a new type of FBGreferred to as chemical composition grating. These gratingsdiffer from other types of FBG in that their refractive indexstructure is attributed to a change in the chemicalcomposition. Chemical composition gratings have shown to beextremely temperature stable surviving temperatures in excessof 1000 oC. Photosensitivity of pure silica and germanium-dopedcore fibers in the presence of hydroxyl groups has also beenstudied and different types of fiber based components have beendeveloped.

    The main result of the thesis is a better understanding ofthe underlying mechanism of the formation of chemicalcomposition gratings and their decay behavior at elevatedtemperatures. The refractive index modulation is caused by aperiodic change in the fluorine concentration, which has beenverified through time-of-flight secondary-ion-mass spectrometryand through studies of the decay behavior of chemicalcomposition gratings. A model based on diffusion of dopants hasbeen developed, which successfully predicts the thermal decayat elevated temperatures. Studies of the dynamics of chemicalcomposition grating formation have resulted in a manufacturingtechnique that allows for reproducible gratingfabrication.

    The main results regarding photosensitivity is a method tosignificantly increase the effect of UV radiation on standardtelecommunications fiber. The method, referred to asOH-flooding, has also been applied to pure-silica core fibersresulting in the first report of strong grating formation insuch fibers.

    Finally, research into different schemes for developingfiber-based components has resulted in two types of singlefiber integrated Mach-Zehnder interferometers; one passiveinterferometer that can be used as an optical filter and oneactive interferometer controlled with internal metalelectrodes.

    Keywords:optical fibers, fiber Bragg gratings,photosensitivity, thermal stability, fiber sensors, chemicalcomposition gratings, fiber components, Mach-Zehnderinterferometer, optical switch, optical modulator.

  • 244.
    Fors, Rickard
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Khartsev, Sergiy
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pohl, A.
    Westin, G.
    Sol-gel derived versus pulsed laser deposited epitaxial La0.67Ca0.33MnO3 films: structure, transport and effects of post-annealing2004In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 467, no 02-jan, p. 112-116Article in journal (Refereed)
    Abstract [en]

    Epitaxial La0.67Ca0.33MnO3 films have been prepared on LaAlO3 crystals by pulsed laser deposition (PLD) and by a novel all-alkoxide sol-gel technique. Different out-of-plane lattice parameters are found for the as-prepared films, and scanning electron microscopy shows a more porous structure for sol-gel films as compared to PLD films. These differences are largely removed by post annealing at 1000 degreesC. Transport measurements show maximum temperature coefficient of resistivity of 8.2% K-1 at 258 K (PLD) and 6.1% K-1 at 241 K (sol-gel) and colossal magnetoresistance at 560 kA/m of 35% at 263 K (PLD) and 32% at 246 K (sol-gel).

  • 245.
    Fors, Rickard
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pohl, A.
    Khartsev, Sergey
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Westin, G.
    Comparison of sol-gel derived and pulsed laser deposited epitaxial La0.67Ca0.33MnO3 films for IR bolometer2004In: Integration Of Advanced Micro-And Nanoelectronic Devices-Critical Issues And Solutions / [ed] Morais, J; Kumar, D; Houssa, M; Singh, RK; Landheer, D; Ramesh, R; Wallace, RM; Guha, S; Koinuma, H, 2004, Vol. 811, p. 379-384Conference paper (Refereed)
    Abstract [en]

    Epitaxial La0.67Ca0.33MnO3 films have been prepared on LaAlO3 crystals by pulsed laser deposition (PLD) and by a novel all-alkoxide sol-gel technique. Different out-of-plane lattice parameters are found for the as-prepared films, and scanning electron microscopy shows a more porous structure for sol-gel films as compared to PLD films. These differences are largely removed by post-annealing at 1000 degreesC. Transport measurements show maximum temperature coefficient of resistivity of 8.2 % K-1 at 258 K (PLD) and 6.1% K-1 at 241 K (sol-gel) and colossal magnetoresistance at 7 kOe of 35% at 263 K (PLD) and 32% at 246 K (sol-gel).

  • 246.
    Forsberg, Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Electronic and Photonic Quantum Devices2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In this thesis various subjects at the crossroads of quantummechanics and device physics are treated, spanning from afundamental study on quantum measurements to fabricationtechniques of controlling gates for nanoelectroniccomponents.

    Electron waveguide components, i.e. electronic componentswith a size such that the wave nature of the electron dominatesthe device characteristics, are treated both experimentally andtheoretically. On the experimental side, evidence of partialballistic transport at room-temperature has been found anddevices controlled by in-plane Pt/GaAs gates have beenfabricated exhibiting an order of magnitude improvedgate-efficiency as compared to an earlier gate-technology. Onthe theoretical side, a novel numerical method forself-consistent simulations of electron waveguide devices hasbeen developed. The method is unique as it incorporates anenergy resolved charge density calculation allowing for e.g.calculations of electron waveguide devices to which a finitebias is applied. The method has then been used in discussionson the influence of space-charge on gate-control of electronwaveguide Y-branch switches.

    Electron waveguides were also used in a proposal for a novelscheme of carrierinjection in low-dimensional semiconductorlasers, a scheme which altogether by- passes the problem ofslow carrier relaxation in suchstructures. By studying aquantum mechanical two-level system serving as a model forelectroabsorption modulators, the ultimate limits of possiblemodulation rates of such modulators have been assessed andfound to largely be determined by the adiabatic response of thesystem. The possibility of using a microwave field to controlRabi oscillations in two-level systems such that a large numberof states can be engineered has also been explored.

    A more fundamental study on quantum mechanical measurementshas been done, in which the transition from a classical to aquantum "interaction free" measurement was studied, making aconnection with quantum non-demolition measurements.

  • 247.
    Forsberg, Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Reversible logic based on electron waveguide Y-branch switches2004In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 15, no 4, p. S298-S302Article in journal (Refereed)
    Abstract [en]

    The lower bound of the energy required to change the state of an electron waveguide Y-branch switch is not thermally limited, and the theoretical limit is orders of magnitude lower than the energy cost of information erasure. Thus as the power dissipation due to information erasure can be avoided by the use of logically reversible gates, such gates based on electron waveguide Y-branch switches promise circuits with extremely low power dissipation. In this paper, reversible logic based on electron waveguide Y-branch switches is proposed and discussed.

  • 248.
    Forsberg, Erik
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hessmo, Björn
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Limits to modulation rates of electroabsorption modulators2004In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 40, no 4, p. 400-405Article in journal (Refereed)
    Abstract [en]

    We analyze the speed limitations of optical electroabsorption modulators. We argue that modulation rate limits are closely related to quantum mechanical adiabaticity. By analyzing the breakdown of the adiabatic approximation, analytical expressions for modulation limits are found. These expressions are numerically validated. Furthermore, we discuss the constraints on the allowable modulation rate set by losses from the quantum well and transition linewidth.

  • 249.
    Forsberg, Erik
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Wesström, Jan Olof
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Self-consistent simulations of mesoscopic devices operating under a finite bias2004In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 48, no 7, p. 1147-1154Article in journal (Refereed)
    Abstract [en]

    A novel numerical algorithm based on the solution of the two-dimensional effective mass equation for current-carrying scattering states in mesoscopic devices is developed. Using this while allowing for an energy dependent transmission matrix, the total charge density distribution based on all electrons injected into the device is calculated through integration over energy. By coupling this energy-resolved calculation of charge density distribution iteratively with a potential calculation a fully self-consistent calculation, which allows for accurate simulations of mesoscopic devices with arbitrary complex device geometries operating under a finite bias, is achieved. Thus it is possible to self-consistently study space charge effects in mesoscopic devices. The developed method is described and tested on a number of sample geometries.

  • 250. Forsberg, U.
    et al.
    Danielsson, O.
    Henry, A.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Janzen, E.
    Aluminum doping of epitaxial silicon carbide2003In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 253, no 04-jan, p. 340-350Article in journal (Refereed)
    Abstract [en]

    Intentional doping of aluminum in 4H and 6H SiC has been performed using a hot-wall CVD reactor. The dependence of aluminum incorporation on temperature, pressure, C/Si ratio, growth rate, and TMA flow has been investigated. The aluminum incorporation showed to be polarity dependent. The high aluminum incorporation on the Si-face is closely related to the carbon coverage on the SiC surface. Changes in process parameters changes the effective C/Si ratio close to the SiC surface. Increased growth rate and C/Si ratio increases the aluminum incorporation on the Si-face. Diffusion limited incorporation occurs at high growth rate. Reduced pressure increases the effective C/Si ratio, and at low growth rate, the aluminum incorporation increases initially, levels off at a critical pressure, and continues to decrease below the critical pressure. The aluminum incorporation showed to be constant in a temperature range of 50degreesC. The highest atomic concentration of aluminum observed in this study was 3 x 10(17) and 8 x 10(18) cm(-3) in Si and C-face, respectively.

2345678 201 - 250 of 1065
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