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  • 1. Abadei, S.
    et al.
    Gevorgian, S.
    Cho, C. R.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Andreasson, J.
    Lindback, T.
    DC field dependent properties of Na0.5K0.5NbO3/SiO2/Si structures at millimeter-wave frequencies2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 13, p. 1900-1902Article in journal (Refereed)
    Abstract [en]

    Dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Omega cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 GHz. For measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of Na0.5K0.5NbO3 films. The slot width between the electrodes is 2 or 4 mum. 13% capacitance change at 40 V dc bias and Q factor more than 15 are observed at 40 GHz, which makes the structure useful for applications in electrically tunable millimeter-wave devices.

  • 2. Aberg, D.
    et al.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pellegrino, P.
    Svensson, B. G.
    Nitrogen deactivation by implantation-induced defects in 4H-SiC epitaxial layers2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 19, p. 2908-2910Article in journal (Refereed)
    Abstract [en]

    Ion implantation causes free charge carrier reduction due to damage in the crystalline structure. Here, nitrogen-doped 4H silicon carbide (n type) epitaxial layers have been investigated using low ion doses in order to resolve the initial stage of the charge carrier reduction. It was found that the reduction of free carriers per ion-induced vacancy increases with increasing nitrogen content. Nitrogen is suggested to be deactivated through reaction with migrating point defects, and silicon vacancies or alternatively interstitials are proposed as the most likely candidates.

  • 3.
    Abergel, David
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Excitonic condensation in spatially separated one-dimensional systems2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 21, article id 213103Article in journal (Refereed)
    Abstract [en]

    We show theoretically that excitons can form from spatially separated one-dimensional ground state populations of electrons and holes, and that the resulting excitons can form a quasicondensate. We describe a mean-field Bardeen-Cooper-Schrieffer theory in the low carrier density regime and then focus on the core-shell nanowire giving estimates of the size of the excitonic gap for InAs/GaSb wires and as a function of all the experimentally relevant parameters. We find that optimal conditions for pairing include small overlap of the electron and hole bands, large effective mass of the carriers, and low dielectric constant of the surrounding media. Therefore, one-dimensional systems provide an attractive platform for the experimental detection of excitonic quasicondensation in zero magnetic field.

  • 4. Achtziger, N
    et al.
    Grillenberger, J
    Witthuhn, W
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Janson, M S
    Svensson, B G
    Hydrogen passivation of silicon carbide by low-energy ion implantation1998In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 73, p. 945-947Article in journal (Refereed)
    Abstract [en]

    implantation of deuterium is performed to investigate the mobility and passivating effect of hydrogen in epitaxial alpha-SiC (polytypes 4H and 6H). To avoid excessive damage and the resulting trapping of hydrogen, the implantation is performed with low energy (600 eV H-2(2)+). The H-2 depth profile is analyzed by secondary ion mass spectrometry. Electrical properties are measured by capacitance-voltage profiling and admittance spectroscopy. In p-type SIG, hydrogen diffuses on a mu m scale even at room temperature and effectively passivates accepters. In n-type SiC, the incorporation of H is suppressed and no passivation is detected. (C) 1998 American Institute of Physics.

  • 5. Ahuja, R.
    et al.
    Eriksson, O.
    Wills, J. M.
    Johansson, Börje
    Electronic structure of Ti3SiC22000In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 76, no 16, p. 2226-2228Article in journal (Refereed)
  • 6. Ali, A.
    et al.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Kaleem Ullah, M.
    Rafique, A.
    Wang, B.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Hubei University, China.
    Alkaline earth metal and samarium co-doped ceria as efficient electrolytes2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 4, article id 043902Article in journal (Refereed)
    Abstract [en]

    Co-doped ceramic electrolytes M0.1Sm0.1Ce0.8O2-δ (M = Ba, Ca, Mg, and Sr) were synthesized via co-precipitation. The focus of this study was to highlight the effects of alkaline earth metals in doped ceria on the microstructure, densification, conductivity, and performance. The ionic conductivity comparisons of prepared electrolytes in the air atmosphere were studied. It has been observed that Ca0.1Sm0.1Ce0.8O2-δ shows the highest conductivity of 0.124 Scm-1 at 650 °C and a lower activation energy of 0.48 eV. The cell shows a maximum power density of 630 mW cm-2 at 650 °C using hydrogen fuel. The enhancement in conductivity and performance was due to increasing the oxygen vacancies in the ceria lattice with the increasing dopant concentration. The bandgap was calculated from UV-Vis data, which shows a red shift when compared with pure ceria. The average crystallite size is in the range of 37-49 nm. DFT was used to analyze the co-doping structure, and the calculated lattice parameter was compared with the experimental lattice parameter.

  • 7.
    Andersson, David A.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Simak, S. I.
    Skorodumova, N. V.
    Abrikosov, I. A.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Redox properties of CeO2-MO2 MO2 (M=Ti, Zr, Hf or Th) solid solutions from first principles calculations2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 3, p. 031909-Article in journal (Refereed)
    Abstract [en]

    The authors have used density functional theory calculations to investigate how the redox thermodynamics and kinetics of CeO2 are influenced by forming solid solutions with TiO2, ZrO2, HfO2, and ThO2. Reduction is facilitated by dissolving TiO2 (largest improvement), HfO2, or ZrO2 (least improvement), while ThO2 makes reduction slightly more difficult. The migration barrier is much lower in the neighborhood of a Ti (largest decrease), Hf, or Zr (least decrease), while the binding energy of solute ions and vacancies increases in the same sequence. They rationalize the properties of ceria solid solutions in terms of defect cluster relaxations.

  • 8. Anversa, Jonas
    et al.
    Chakraborty, Sudip
    Piquini, Paulo
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    High pressure driven superconducting critical temperature tuning in Sb2Se3 topological insulator2016In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, no 21, article id 212601Article in journal (Refereed)
    Abstract [en]

    In this letter, we are reporting the change of superconducting critical temperature in Sb2Se3 topological insulator under the influence of an external hydrostatic pressure based on first principles electronic structure calculations coupled with Migdal-Eliashberg model. Experimentally, it was shown previously that Sb2Se3 was undergoing through a transition to a superconducting phase when subjected to a compressive pressure. Our results show that the critical temperature increases up to 6.15K under the pressure unto 40GPa and, subsequently, drops down until 70 GPa. Throughout this pressure range, the system is preserving the initial Pnma symmetry without any structural transformation. Our results suggest that the possible relevant mechanism behind the superconductivity in Sb2Se3 is primarily the electron-phonon coupling.

  • 9. Ao, X. Y.
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Negative refraction of left-handed behavior in porous alumina with infiltrated silver at an optical wavelength2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 10Article in journal (Refereed)
  • 10. Ao, Xianyu
    et al.
    Liu, Liu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Polarization beam splitter based on a two-dimensional photonic crystal of pillar type2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Applied physics letters, Vol. 89, no 17, p. 171115-Article in journal (Refereed)
    Abstract [en]

    Negatively and positively refractive behaviors are achieved in a two-dimensional photonic crystal of pillar type for TE and TM polarizations, respectively, at the same frequency. The photonic crystal is formed by a triangular lattice of silicon pillars of finite height on a silicon substrate. A polarization beam splitter based on such a photonic-crystal slab is demonstrated. Measurements at near infrared wavelengths indicate that two beams of different polarizations can be split with an extinction ratio of over 10 dB in a wide wavelength range.

  • 11. Ao, Xianyu
    et al.
    Tong, Xili
    Kim, Dong Sik
    Zhang, Lianbing
    Knez, Mato
    Mueller, Frank
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Schmidt, Volker
    Black silicon with controllable macropore array for enhanced photoelectrochemical performance2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 11, p. 111901-Article in journal (Refereed)
    Abstract [en]

    Macroporous silicon with multiscale texture for reflection suppression and light trapping was achieved through a controllable electrochemical etching process. It was coated with TiO2 by atomic layer deposition, and used as the photoanode in photocatalytic water splitting. A conformal pn-junction was also built-in in order to split water without external bias. A 45% enhancement in photocurrent density was observed after black silicon etching. In comparison with nano-structured silicon, the etching process here has neither metal contamination nor requirement of vacuum facilities.

  • 12. Araujo, C. M.
    et al.
    Scheicher, R. H.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermodynamic analysis of hydrogen sorption reactions in Li-Mg-N-H systems2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 2Article in journal (Refereed)
    Abstract [en]

    We report a comprehensive first-principles study of the thermodynamics of the hydrogen release reaction from xLiH-yMg(NH2)(2) mixtures involving the composition ratios (x=2, y=1), (x=8, y=3), and (x=12, y=3), with special emphasis on the effect of the different intermediate steps. For all three mixing ratios of LiH/Mg(NH2)(2) we find that the hydrogen release is initiated by the same reaction with an enthalpy of 46.1 kJ/mol of H-2 in excellent agreement with recent experimental results. Additionally, we also investigated the substitution of LiH by MgH2 as reaction partner of Mg(NH2)(2) in the fully hydrogenated state.

  • 13. Araujo, C. M.
    et al.
    Scheicher, R. H.
    Jena, P.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    On the structural and energetic properties of the hydrogen absorber Li2Mg(NH)(2)2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 9Article in journal (Refereed)
    Abstract [en]

    The authors have performed density functional theory based calculations of several possible conformations for the crystal structure of Li2Mg(NH)(2) and they confirm the alpha phase, resolved from both x-ray and neutron diffraction data, as the ground-state configuration. It is also found that although the N-H bond is stronger in Li2Mg(NH)(2) than in Li2NH, hydrogen release from Li2Mg(NH)(2)/LiH mixture displays more favorable thermodynamics than that from the Li2NH/LiH mixture. The insights gained from this seemingly counterintuitive result should prove helpful in the search for promising hydrogen storage materials.(c) 2007 American Institute of Physics.

  • 14.
    Araujo, C. Moysés
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Kapilashrami, Mukes
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Jun, Xu
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Jayakumar, Onattu D.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Nagar, Sandeep
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Wu, Yan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Århammar, Cecilia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Gehring, Gillian A.
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Room temperature ferromagnetism in pristine MgO thin films2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 23Article in journal (Refereed)
    Abstract [en]

    Robust ferromagnetic ordering at, and well above room temperature is observed in pure transparent MgO thin films (<170 nm thick) deposited by three different techniques. Careful study of the wide scan x-ray photoelectron spectroscopy rule out the possible presence of any magnetic contaminants. In the magnetron sputtered films, we observe magnetic phase transitions as a function of film thickness. The maximum saturation magnetization of 5.7 emu/cm(3) is measured on a 170 nm thick film. The films above 500 nm are found to be diamagnetic. Ab initio calculations suggest that the ferromagnetism is mediated by cation vacancies.

  • 15. Arulkumaran, S.
    et al.
    Ng, G. I.
    Tan, C. L.
    Liu, Z. H.
    Bu, J.
    Radhakrishnan, K.
    Aggerstam, T.
    Sjodin, M.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Enhancement of both direct-current and microwave characteristics of AlGaN/GaN high-electron-mobility transistors by furnace annealing2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 2Article in journal (Refereed)
    Abstract [en]

    The enhancement of both direct-current (dc) and microwave characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) were demonstrated by conventional furnace annealing at 400 degrees C for 5 min. Due to the improvement in Ni/Au Schottky contact properties by furnace annealing, about 17%, 34%, 23%, and 25% of enhancements in maximum drain current density, maximum extrinsic transconductance (g(m max)), cutoff frequency and maximum oscillation frequency were observed, respectively. A positive threshold voltage shift and the increase in g(m max) can also be correlated to the improved Schottky parameters such as ideality factor and barrier height. The annealed devices exhibited low reverse gate-leakage-current by more than three orders of magnitude and low drain-leakage-current by two orders of magnitude. Correspondingly, the devices exhibited 55% of higher breakdown voltage after annealing. The furnace annealing is an effective and viable means to enhance both dc and microwave characteristics of AlGaN/GaN HEMTs.

  • 16. Astrath, N. G. C.
    et al.
    Sato, F.
    Pedrochi, F.
    Medina, A. N.
    Bento, A. C.
    Baesso, M. L.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    da Silva, A. Ferreira
    Band gap energy determination by photoacoustic spectroscopy under continuous light excitation2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 23Article in journal (Refereed)
    Abstract [en]

    In this work the authors used the photoacoustic spectroscopy under continuous light excitation to determine the optical band gap of semiconductors. The experiments were performed in lead iodide PbI2 and hexagonal silicon carbide 4H-SiC samples. The nonradiative relaxation processes are discussed in terms of the generated signal. A mechanism to describe the signal increase/decrease under the continuous excitation is presented. The results showed that the method was useful to locate the band gap directly from the optical absorption spectra.

  • 17. Ayedh, H. M.
    et al.
    Nipoti, R.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Svensson, B. G.
    Elimination of carbon vacancies in 4H-SiC employing thermodynamic equilibrium conditions at moderate temperatures2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 25Article in journal (Refereed)
    Abstract [en]

    The carbon vacancy (VC) is a major point defect in high-purity 4H-SiC epitaxial layers limiting the minority charge carrier lifetime. In layers grown by chemical vapor deposition techniques, the VC concentration is typically in the range of 1012cm-3, and after device processing at temperatures approaching 2000 °C, it can be enhanced by several orders of magnitude. In the present study, both as-grown layers and a high-temperature processed one have been annealed at 1500 °C and the VC concentration is demonstrated to be strongly reduced, exhibiting a value of only a few times 1011cm-3 as determined by deep-level transient spectroscopy measurements. The value is reached already after annealing times on the order of 1 h and is evidenced to reflect thermodynamic equilibrium under C-rich ambient conditions. The physical processes controlling the kinetics for establishment of the VC equilibrium are estimated to have an activation energy below ∼3 eV and both in-diffusion of carbon interstitials and out-diffusion of VC’s are discussed as candidates. This concept of VC elimination is flexible and readily integrated in a materials and device processing sequence.

  • 18. Azarov, Alexander
    et al.
    Rauwel, Protima
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Elektronics, Integrated devices and circuits.
    Monakhov, Edouard
    Svensson, Bengt G.
    Extended defects in ZnO: Efficient sinks for point defects2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 2, article id 022103Article in journal (Refereed)
    Abstract [en]

    Dopant-defect reactions dominate the defect formation in mono-crystalline ZnO samples implanted with Ag and B ions. This is in contrast to most other ion species studied and results in an enhanced concentration of extended defects, such as stacking faults and defect clusters. Using a combination of B and Ag implants and diffusion of residual Li atoms as a tracer, we demonstrate that extended defects in ZnO act as efficient traps for highly mobile Zn interstitials. The results imply that dynamic annealing involving interaction of point defects with extended ones can play a key role in the disorder saturation observed for ZnO and other radiation-hard semiconductors implanted with high doses.

  • 19. Bai, Songang
    et al.
    Li, Qiang
    Zhang, Han
    Chen, Xingxing
    Luo, Si
    Gong, Hanmo
    Yang, Yuanqing
    Zhao, Ding
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Large third-order nonlinear refractive index coefficient based on gold nanoparticle aggregate films2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 14, article id 141111Article in journal (Refereed)
    Abstract [en]

    Au nanoparticles show large third-order nonlinear effect and ultra-fast response. Here a high nonlinear aggregate film based on self-assembled gold nanoparticles is reported and its third-order nonlinear refractive index coefficient is measured by Z-scan experiment. The third-order nonlinear refractive index coefficient of the Au nanoparticle aggregate film (gamma(1) = 9.2 x 10(-9) cm(2)/W) is found to be larger than that of an 8-nm-thick sputtered Au film (gamma(2)= 6.5 x 10(-9) cm(2)/W). This large nonlinear effect can be attributed to the strong field enhancement due to localized plasmon resonances between Au nanoparticles. The result shows that the self-assembled Au nanoparticle aggregate film could be a promising candidate as a third-order nonlinear optical material.

  • 20. Balobaid, Laila
    et al.
    Carville, N. Craig
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Collins, Liam
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Rodriguez, Brian J.
    Photoreduction of metal nanostructures on periodically proton exchanged MgO-doped lithium niobate crystals2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 18, p. 182904-Article in journal (Refereed)
    Abstract [en]

    Local reactivity on periodically proton exchanged lithium niobate (PPE: LN) surfaces is a promising route for the fabrication of regularly spaced nanostructures. Here, using MgO-doped PPE: LN templates, we investigate the influence of the doping on the nanostructure formation as a function of the proton exchange (PE) depth. The deposition is found to occur preferentially along the boundary between MgO-doped LN and the PE region when the PE depth is at least 1.73 mu m, however, for shallower depths, deposition occurs across the entire PE region. The results are found to be consistent with an increased photoconductivity of the MgO-doped LN.

  • 21. Balobaid, Laila
    et al.
    Carville, N. Craig
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Rodriguez, Brian J.
    Direct shape control of photoreduced nanostructures on proton exchanged ferroelectric templates2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 4, p. 042908-Article in journal (Refereed)
    Abstract [en]

    Photoreduction on a periodically proton exchanged ferroelectric crystal leads to the formation of periodic metallic nanostructures on the surface. By varying the depth of the proton exchange (PE) from 0.59 to 3.10 mu m in congruent lithium niobate crystals, the width of the lateral diffusion region formed by protons diffusing under the mask layer can be controlled. The resulting deposition occurs in the PE region with the shallowest PE depth and preferentially in the lateral diffusion region for greater PE depths. PE depth-control provides a route for the fabrication of complex metallic nanostructures with controlled dimensions on chemically patterned ferroelectric templates.

  • 22. Barrios, C. A.
    et al.
    Holgado, M.
    Guarneros, O.
    Gylfason, Kristinn Björgvin
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Sanchez, B.
    Casquel, R.
    Sohlström, Hans
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Reconfiguration of microring resonators by liquid adhesion2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 20, article id 203114Article in journal (Refereed)
    Abstract [en]

    We present a procedure to reconfigure microring resonators based on liquid surface adhesion. Droplets of organic solvents were deposited over Si3N4/SiO2 strip- and slot-waveguide ring resonators, and the transmission spectra were measured several hours after the evaporation of the droplets at room temperature. Our measurements show that the optical properties of the microrings are significantly modified by liquid adhered to the waveguides, persisting even 96 h after bulk evaporation. Liquid-solid interfacial forces slow down liquid evaporation at the nanoscale, enabling permanent photonic configurations. Rewriteability is achieved by removing the adhered liquid with heat.

  • 23.
    Berrier, Audrey
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Shi, Yaocheng
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Siegert, Jörg
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Evidence for accumulated sidewall damage in dry etched photonic crystals2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Article in journal (Other academic)
  • 24.
    Bertilson, Michael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    von Hofsten, Olov
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Lindblom, Magnus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Wilhein, Thomas
    Hertz, Hans M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Compact high-resolution differential interference contrast soft x-ray microscopy2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 064104Article in journal (Refereed)
    Abstract [en]

    We demonstrate high-resolution x-ray differential interference contrast (DIC) in a compact soft x-ray microscope. Phase contrast imaging is enabled by the use of a diffractive optical element objective which is matched to the coherence conditions in the microscope setup. The performance of the diffractive optical element objective is evaluated in comparison with a normal zone plate by imaging of a nickel siemens star pattern and linear grating test objects. Images obtained with the DIC optic exhibit typical DIC enhancement in addition to the normal absorption contrast. Contrast transfer functions based on modulation measurements in the obtained images show that the DIC optic gives a significant increase in contrast without reducing the spatial resolution. The phase contrast operation mode now available for our compact soft x-ray microscope will be a useful tool for future studies of samples with low absorption contrast.

  • 25. Bertulis, K.
    et al.
    Krotkus, A.
    Aleksejenko, G.
    Pacebutas, V.
    Adomavicius, R.
    Molis, G.
    Marcinkevicius, Saulius
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    GaBiAs: A material for optoelectronic terahertz devices2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 20Article in journal (Refereed)
    Abstract [en]

    GaBiAs layers have been grown by molecular beam epitaxy at low (270-330 degrees C) temperatures and were characterized by several experimental techniques. It was shown that the spectral photosensitivity cutoff wavelength reaches similar to 1.4 mu m when the growth temperature is as low as 280 degrees C. Optical pump-terahertz probe measurements made on these layers have evidenced that the electron trapping time decreases with decreasing growth temperature from 20 to about 1 ps. GaBiAs layers were used for manufacturing photoconductive terahertz emitters and detectors, which, when excited with Ti:sapphire laser pulses, have demonstrated a signal bandwidth of 3 THz.

  • 26. Bleskov, I. D.
    et al.
    Smirnova, E. A.
    Vekilov, Y. K.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Katsnelson, M.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Abrikosov, I. A.
    Isaev, E. I.
    Ab initio calculations of elastic properties of Ru1-xNixAl superalloys2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 16Article in journal (Refereed)
    Abstract [en]

    Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1-xNixAl alloys. We have found that the elastic constants C' and C11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design Ru-Ni-Al alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.

  • 27. Bligaard, T.
    et al.
    Johannesson, G. H.
    Ruban, Andrei V.
    Skriver, H. L.
    Jacobsen, K. W.
    Norskov, J. K.
    Pareto-optimal alloys2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 83, no 22, p. 4527-4529Article in journal (Refereed)
    Abstract [en]

    Large databases that can be used in the search for new materials with specific properties remain an elusive goal in materials science. The problem is complicated by the fact that the optimal material for a given application is usually a compromise between a number of materials properties and the cost. In this letter we present a database consisting of the lattice parameters, bulk moduli, and heats of formation for over 64 000 ordered metallic alloys, which has been established by direct first-principles density-functional-theory calculations. Furthermore, we use a concept from economic theory, the Pareto-optimal set, to determine optimal alloy solutions for the compromise between low compressibility, high stability, and cost.

  • 28. Blomqvist, A.
    et al.
    Araujo, C. M.
    Jena, P.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Dehydrogenation from 3d-transition-metal-doped NaAlH4: Prediction of catalysts2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 14Article in journal (Refereed)
    Abstract [en]

    A fundamental understanding of the role of catalysts in improving the kinetics and thermodynamics of hydrogen sorption in NaAlH4 is the key for using this material in hydrogen storage. The authors present a systematic theoretical study of energies needed to desorb hydrogen in 3d transition metal (Sc-Cu)-doped NaAlH4. They show that Cr and Fe atoms can be far more effective catalysts than Ti in desorbing hydrogen. The role of the 3d metal atoms in improving the thermodynamics of dehydrogenation is attributed to a significant shortening of the bond length with neighboring Al atoms.

  • 29.
    Blomqvist, Mats
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Khartsev, Sergiy
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Petraru, Adrian
    Inst. of Thin Films and Interfaces, Section: Ion Technology, Forschungszentrum Jülich.
    Buchal, Christoph
    Inst. of Thin Films and Interfaces, Section: Ion Technology, Forschungszentrum Jülich.
    Optical waveguiding in magnetron-sputtered Na0.5K0.5NbO3 thin films on sapphire substrates2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 3, p. 439-441Article in journal (Refereed)
    Abstract [en]

    Preferentially oriented perovskite-structured Na0.5K0.5NbO3 (NKN) thin films have been deposited on hexagonal Al2O3(01 (1) under bar2) substrates using rf magnetron sputtering of a stoichiometric, high-density, ceramic target. Structural and film surface properties were measured using x-ray diffraction and atomic force microscopy, respectively. Optical and waveguiding properties were characterized using a prism-coupling technique. We observed sharp and distinguishable TM and TE propagation modes and measured the refractive index of NKN thin films of different thicknesses. The ordinary and extraordinary refractive indices were calculated to be n(o)=2.247+/-0.002 and n(e)=2.216+/-0.002 for a 2.0-mum-thick film at 632.8 nm. This implies a birefringence Deltan=n(e)-n(o)=-0.031+/-0.002 in the film. These first results show the potential use of rf-sputtered NKN films as an electro-optical active material.

  • 30.
    Blomqvist, Mats
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Koh, Jung-Hyuk
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Khartsev, Sergiy
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Andréasson, Johanna
    Department of Materials and Manufacturing Engineering, Luleå University of Technology.
    High-performance epitaxial Na0.5K0.5NbO3 thin films by magnetron sputtering2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, no 2, p. 337-339Article in journal (Refereed)
    Abstract [en]

    Epitaxial Na0.5K0.5NbO3 (NKN) thin films have been grown on LaAlO3 substrates by rf magnetron sputtering of a stoichiometric, high-density, ceramic target. X-ray diffraction analysis showed c-axis oriented cube-on-cube growth. Micrometer size interdigital capacitor (IDC) structures were defined on the surface of the NKN film using photolithography. The electrical characterization at 1 MHz showed dissipation factor tan delta of 0.010, tunability 16.5% at 200 kV/cm and dielectric permittivity epsilon(r)=470. The frequency dispersion of epsilon(r) between 1 kHz and 1 MHz was 8.5% and the IDCs showed very good insulating properties with leakage current density on the order of 30 nA/cm(2) at 400 kV/cm. The polarization loop exhibits weak ferroelectric hysteresis with maximum polarization 23.5 muC/cm(2) at 600 kV/cm. These results are promising for tunable microwave devices based on rf sputtered NKN thin films.

  • 31.
    Bonanni, Valentina
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Fang, Yeyu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Dumas, Randy K.
    Department of Physics, University of Gothenburg, Sweden.
    Zha, Chaolin
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Bonetti, Stefano
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nogués, Josep
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    First-order reversal curve analysis of graded anisotropy FePtCu films2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 20, p. 202501-Article in journal (Refereed)
    Abstract [en]

    The reversal mechanisms of graded anisotropy FePtCu films have been investigated by alternating gradient magnetometer (AGM) and magneto-optical Kerr effect (MOKE) measurements with first-order reversal curve (FORC) techniques. The AGM-FORC analysis, which clearly shows the presence of soft and hard components, is unable to resolve how these phases are distributed throughout the film thickness. MOKE-FORC measurements, which preferentially probe the surface of the film, reveal that the soft components are indeed located toward the top surface. Combining AGM-FORC with the inherent surface sensitivity of MOKE-FORC analysis allows for a comprehensive analysis of heterogeneous systems such as graded materials.

  • 32.
    Bonetti, Stefano
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Muduli, Pranaba
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Mancoff, Fred
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Spin torque oscillator frequency versus magnetic field angle: The prospect of operation beyond 65 GHz2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 10Article in journal (Refereed)
    Abstract [en]

    We study the impact of the magnetic field angle on the oscillation frequency of a nanocontact spin torque oscillator (STO) in magnetic fields up to 2.1 T. A model based on a single nonlinear, nonpropagating spin wave mode is found to explain the experimental data. We observe oscillation frequencies as high as 46 GHz in high magnetic fields applied normal to the film plane, and we are able to extrapolate the maximum expected operating frequency to beyond 65 GHz for in-plane magnetic fields. The STO signal remains surprisingly strong at these conditions, which opens up for possible millimeter-wave applications.

  • 33.
    Borgani, Riccardo
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Forchheimer, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Bergqvist, Jonas
    Thorén, Per-Anders
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Inganas, Olle
    Haviland, David B.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Intermodulation electrostatic force microscopy for imaging surface photo-voltage2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 14, p. 143113-Article in journal (Refereed)
    Abstract [en]

    We demonstrate an alternative to Kelvin Probe Force Microscopy for imaging surface potential. The open-loop, single-pass technique applies a low-frequency AC voltage to the atomic force microscopy tip while driving the cantilever near its resonance frequency. Frequency mixing due to the nonlinear capacitance gives intermodulation products of the two drive frequencies near the cantilever resonance, where they are measured with high signal to noise ratio. Analysis of this intermodulation response allows for quantitative reconstruction of the contact potential difference. We derive the theory of the method, validate it with numerical simulation and a control experiment, and we demonstrate its utility for fast imaging of the surface photo-voltage on an organic photovoltaic material.

  • 34. Boström, Mathias
    et al.
    Ninham, Barry W.
    Brevik, Iver
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Parsons, Drew F.
    Sernelius, Bo E.
    Ultrathin metallic coatings can induce quantum levitation between nanosurfaces2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 25, p. 253104-Article in journal (Refereed)
    Abstract [en]

    There is an attractive Casimir-Lifshitz force between two silica surfaces in a liquid (bromobenze or toluene). We demonstrate that adding an ultrathin (5-50 angstrom) metallic nanocoating to one of the surfaces results in repulsive Casimir-Lifshitz forces above a critical separation. The onset of such quantum levitation comes at decreasing separations as the film thickness decreases. Remarkably, the effect of retardation can turn attraction into repulsion. From that we explain how an ultrathin metallic coating may prevent nanoelectromechanical systems from crashing together.

  • 35. Bratkovsky, Alexander
    et al.
    Ponizovskaya, Ekaterina
    Wang, Shih-Yuan
    Holmström, Petter
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    A metal-wire/quantum-dot composite metamaterial with negative epsilon and compensated optical loss2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 19, p. 193106-Article in journal (Refereed)
    Abstract [en]

    Numerical simulations of a binary mixture of quantum dots exhibiting gain with silver nanorods are performed, showing the feasibility of lossless negative epsilon operation for realistic material structures and parameters.

  • 36. Buchholt, Kristina
    et al.
    Ghandi, Reza
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Domeij, Martin
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Lu, J.
    Eklund, Per
    Hultman, Lars
    Lloyd Spetz, Anita
    Ohmic contact properties of magnetron sputtered Ti3SiC2 on n- and p-type 4H-silicon carbide2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 4, p. 042108-Article in journal (Refereed)
    Abstract [en]

    Epitaxial Ti3SiC2 (0001) thin film contacts were grown on doped 4H-SiC (0001) using magnetron sputtering in an ultra high vacuum system. The specific contact resistance was investigated using linear transmission line measurements. Rapid thermal annealing at 950 degrees C for 1 min of as-deposited films yielded ohmic contacts to n-type SiC with contact resistances in the order of 10(-4) Omega cm(2). Transmission electron microscopy shows that the interface between Ti3SiC2 and n-type SiC is atomically sharp with evidence of interfacial ordering after annealing. (c) 2011 American Institute of Physics.

  • 37. Busch, S.
    et al.
    Schnurer, M.
    Kalashnikov, M.
    Schonnagel, H.
    Stiel, H.
    Nickles, P. V.
    Sandner, W.
    Ter-Avetisyan, S.
    Karpov, V.
    Vogt, Ulrich
    Ion acceleration with ultrafast lasers2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 19, p. 3354-3356Article in journal (Refereed)
    Abstract [en]

    Hot-electron confinement can build up fields capable of accelerating ions up to MeV energies when an ultrashort 35-fs laser pulse at similar to2x10(18) W/cm(2) interacts with a small spherical target. Singly charged ions with different masses have similar energies. A simple phenomenological model describes how ultrashort and less-energy-consumptive pulses drive ions to MeV energies. The energetic and spatial-emission characteristics of protons, deuterons and oxygen ions released from water and heavy-water droplets of similar to15 mum in size was determined for this interaction scenario.

  • 38. Butte, Raphael
    et al.
    Lahourcade, Lise
    UŽdavinys, Tomas Kristijonas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Callsen, Gordon
    Mensi, Mounir
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Glauser, Marlene
    Rossbach, Georg
    Martin, Denis
    Carlin, Jean-Francois
    Marcinkevičius, Saulius
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Grandjean, Nicolas
    Optical absorption edge broadening in thick InGaN layers: Random alloy atomic disorder and growth mode induced fluctuations2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 3, article id 032106Article in journal (Refereed)
    Abstract [en]

    To assess the impact of random alloying on the optical properties of the InGaN alloy, high-quality InxGa1-xN (0 < x < 0.18) epilayers grown on c-plane free-standing GaN substrates are characterized both structurally and optically. The thickness (25-100 nm) was adjusted to keep these layers pseudomorphically strained over the whole range of explored indium content as checked by x-ray diffraction measurements. The evolution of the low temperature optical absorption (OA) edge line-width as a function of absorption energy, and hence the indium content, is analyzed in the framework of the random alloy model. The latter shows that the OA edge linewidth should not markedly increase above an indium content of 4%, varying from 17 meV to 30 meV for 20% indium. The experimental data initially follow the same trend with, however, a deviation from this model for indium contents exceeding only similar to 2%. Complementary room temperature near-field photoluminescence measurements carried out using a scanning near-field optical microscope combined with simultaneous surface morphology mappings reveal spatial disorder due to growth meandering. We conclude that for thick high-quality pseudomorphic InGaN layers, a deviation from pure random alloying occurs due to the interplay between indium incorporation and longer range fluctuations induced by the InGaN step-meandering growth mode.

  • 39. Cai, Tao
    et al.
    Liu, Qingkun
    Shi, Yaocheng
    Chen, Pengxin
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    An efficiently tunable microring resonator using a liquid crystal-cladded polymer waveguide2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 12, p. 121109-Article in journal (Refereed)
    Abstract [en]

    An electrically tunable polymer microring resonator of large tunability and low applied voltage is demonstrated using active liquid crystal (LC) cladding. A large tuning range of 0.73 nm is achieved due to more homogenous LC molecular alignment and enhanced interaction of the light with the LC cladding in the simplified polymer waveguide structure. The operating voltage decreases to 10 V with a threshold of only 3 V by the utilization of interdigital electrodes.

  • 40.
    Cai, Yangjian
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Propagation of a partially coherent twisted anisotropic Gaussian Schell-model beam in a turbulent atmosphere2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 4Article in journal (Refereed)
    Abstract [en]

    Analytical formulas are derived for the propagation of a partially coherent twisted anisotropic Gaussian Schell-model (TAGSM) beam in a turbulent atmosphere. Propagation properties of a TAGSM beam in a turbulent atmosphere are investigated in detail. It is found that a TAGSM beam will become a circular beam in a turbulent atmosphere, and low coherence and larger twist have an effect of anticircularization of the beam spot. The beam spot spreads more rapidly for lower coherence, larger twist, or stronger turbulence.

  • 41. Camacho, Miguel
    et al.
    Mitchell-Thomas, Rhiannon C.
    Hibbins, Alastair P.
    Sambles, J. Roy
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mimicking glide symmetry dispersion with coupled slot metasurfaces2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 111, no 12, article id 121603Article in journal (Refereed)
    Abstract [en]

    In this letter, we demonstrate that the dispersion properties associated with glide symmetry can be achieved in systems that only possess reflection symmetry by balancing the influence of two sublattices. We apply this approach to a pair of coupled slots cut into an infinite perfectly conducting plane. Each slot is notched on either edge, with the complete two-slot system having only mirror symmetry. By modifying the relative size of the notches on either side of the slots, we show that a linear dispersion relation with a degeneracy with non-zero group velocity at the Brillouin zone boundary can be achieved. These properties, until now, only found in systems with glide symmetry are numerically and experimentally validated. We also show that these results can be used for the design of ultra-wideband one-dimensional leaky wave antennas in coplanar waveguide technology.

  • 42.
    Canalias, Carlota
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Nordlöf, Mats
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    A KTiOPO4 nonlinear photonic crystal for blue second harmonic generation2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 8Article in journal (Refereed)
    Abstract [en]

    A nonlinear photonic crystal with a rectangular domain lattice of 6.09x6 mu m(2) has been fabricated and characterized in flux-grown KTiOPO4. It was used to demonstrate continuous-wave and multiple beam tunable blue second harmonic generation.

  • 43.
    Canalias, Carlota
    et al.
    KTH, Superseded Departments, Physics.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Clemens, Rosalie
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Submicron periodically poled flux-grown KTiOPO42003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 24, p. 4233-4235Article in journal (Refereed)
    Abstract [en]

    A submicron domain grating has been created in a bulk ferroelectric. Electron-beam lithography and electric-field poling were used to fabricate the 800 nm period grating in a 0.5-mm-thick flux-grown KTiOPO4 sample. The domain structure was characterized with an atomic force microscope and was used to demonstrate electrically amplitude adjustable Bragg reflections.

  • 44.
    Canalias, Carlota
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Fokine, Michael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Backward quasi-phase-matched second-harmonic generation in submicrometer periodically poled flux-grown KTiOPO42005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 18, p. 181105-1-181105-3Article in journal (Refereed)
    Abstract [en]

    A 1 turn thick flux-grown KTiOPO4 sample was poled with a 720 nm domain period by employing deep-UV laser lithography, chemical patterning, and electric field poling. An atomic force microscope was used to characterize the periodic domain structure. The sample was used to demonstrate sixth and seventh order quasi-phase-matched backward second-harmonic generation.

  • 45.
    Canalias, Carlota
    et al.
    KTH, Superseded Departments, Physics.
    Pasiskevicius, Valdas
    KTH, Superseded Departments, Physics.
    Fragemann, Anna
    KTH, Superseded Departments, Physics.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    High-resolution domain imaging on the nonpolar y-face of periodically poled KTiOPO4 by means of atomic force microscopy2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 83, no 4, p. 734-736Article in journal (Refereed)
    Abstract [en]

    The inverse piezoelectric effect is used to produce high-resolution images of ferroelectric domains in periodically poled KTiOPO4 crystals on their nonpolar y-face using atomic force microscopy. We demonstrate that the technique is convenient for studying the nucleation and growth of domains in a periodically poled KTiOPO4 sample.

  • 46.
    Canalias, Carlota
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Grilli, Simonetta
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    De Natale, P.
    Ferraro, P.
    In situ visualization of domain kinetics in flux grown KTiOPO4 by digital holography2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 6, p. 064105-Article in journal (Refereed)
    Abstract [en]

    The fast dynamic evolution of ferroelectric domains during electric field poling in flux grown KTiOPO4 crystals was investigated online by a digital holography based technique. The dependence of the ferroelectric domain kinetics on the electric field temporal wave form and poling history was studied. High-speed imaging by means of a complementary metal-oxide-semiconductor image sensor camera allowed in situ measurement of the domain wall propagation speed under different poling conditions. The results also give evidence of the strong influence of the dielectric surface layer in this material.

  • 47.
    Canalias, Carlota
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Wang, Shunhua
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Nucleation and growth of periodic domains during electric field poling in flux-grown KTiOPO4 observed by atomic force microscopy2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 3, p. 032905-1-032905-3Article in journal (Refereed)
    Abstract [en]

    The domain structure of periodically poled KTiOPO4 crystals were studied on both the polar and nonpolar faces utilizing a voltage-modulated atomic force microscope. The measurements give information of domain nucleation, growth, and merging. Two different kind of overpoling behaviors have been observed depending on the magnitude of the applied field.

  • 48. Carmody, C.
    et al.
    Tan, H. H.
    Jagadish, C.
    Gaarder, A.
    Marcinkevicius, Saulius
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Ion-implanted In0.53Ga0.47As for ultrafast optoelectronic applications2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 22, p. 3913-3915Article in journal (Refereed)
    Abstract [en]

    Undoped In0.53Ga0.47As epilayers were implanted with 2- MeV Fe+ ions at doses of 1x10(15) and 1x10(16) cm(-2) at room temperature and annealed at temperatures between 500 and 800 degreesC. Hall-effect measurements show that after annealing, layers with resistivities on the order of 10(5) Omega/square can be achieved. Carrier lifetimes as short as 300 fs are observed for samples annealed at 500 and 600 degreesC. For higher annealing temperatures, characteristic times of the optical response are on the order of a few picoseconds.

  • 49.
    Cederström, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Lundqvist, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    Ribbing, Carolina
    Uppsala Universitet.
    Multi-prism x-ray lens2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, no 8, p. 1399-1401Article in journal (Refereed)
    Abstract [en]

    Refractive x-ray lenses with a triangular surface profile have been used to focus a synchrotron beam to sub-mum line width. These lenses are free from spherical aberration and work in analogy with one-dimensional focusing parabolic compound refractive lenses. However, the focal length can be easily varied by changing the gap between the two jaws. Silicon lenses were fabricated by wet anisotropic etching, and epoxy replicas were molded from the silicon masters. The lenses provided intensity gains up to a factor of 32 and the smallest focal line width was 0.87 mum. The simplified geometry and associated fabrication technique open possibilities for low-Z materials such as beryllium, which should greatly enhance the performance of refractive x-ray optics. (C) 2002 American Institute of Physics.

  • 50.
    Chacinski, Marek
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Marcks von Würtemberg, Rickard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Mogg, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Sundgren, Petrus
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Single-mode 1.27 μm InGaAs vertical cavity surface-emitting lasers with temperature-tolerant modulation characteristics2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 21, p. 211109-1-211109-3Article in journal (Refereed)
    Abstract [en]

    The dynamic performance of InGaAs/GaAs 1.27 &mu; m single-mode vertical cavity surface emitting lasers (VCSELs) is presented. In order to reach such a long wavelength, the devices utilize highly strained double-quantum wells and a large detuning between the material gain peak and cavity resonance. It is found that the large detuning improves the temperature stability of both static and modulation characteristics. A resonance frequency of 7.8-9.5 GHz and optical power of 0.30 mW in fiber was maintained throughout the investigated temperature range of 20-90 &DEG; C. The intrinsic response of the device suggests that long-wavelength InGaAs/GaAs VCSELs have the potential to be used as low cost uncooled optical transmitters at 10 Gbit/s. &COPY; 2005 American Institute of Physics. &COPY; 2005 American Institute of Physics.

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