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  • 1.
    Akbari, Saeed
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Kostov, Konstantin Stoychev
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Brinkfeldt, Klas
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Bakowski, Mietek
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Andersson, Dag
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Low Inductive SiC Power Electronics Module with Flexible PCB Interconnections and 3D Printed Casing2022In: 2022 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2022, Institute of Electrical and Electronics Engineers Inc. , 2022Conference paper (Refereed)
    Abstract [en]

    Silicon carbide (SiC) power devices are steadily increasing their market share in various power electronics applications. However, they require low-inductive packaging in order to realize their full potential. In this research, low-inductive layouts for half-bridge power modules, using a direct bonded copper (DBC) substrate, that are suitable for SiC power devices, were designed and tested. To reduce the negative effects of the switching transients on the gate voltage, flexible printed circuit boards (PCBs) were used to interconnect the gate and source pins of the module with the corresponding pads of the power chips. In addition, conductive springs were used as low inductive, solder-free contacts for the module power terminals. The module casing and lid were produced using additive manufacturing, also known as 3D printing, to create a compact design. It is shown that the inductance of this module is significantly lower than the commercially available modules.

  • 2.
    Anders, Berntson
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Analysis of coherent and incoherent interactions of amplitude shifted solitons in optical fibres1995In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 52, no 5, p. 544-553Article in journal (Refereed)
    Abstract [en]

    Nonlinear interaction between pulses can severely reduce the bit-rate of an optical communication system. One way of reducing this interaction is amplitude shifting of consequtive pulses. In the present work a detailed analytical and numerical investigation is made of the coherent and incoherent interactions between two soliton pulses of unequal amplitudes. For the case of coherent interaction the obtained expressions for the pulse parameters in terms of initial phase and amplitude differences give a clear and explicit prediction of the reduction of the interaction strength for unequal soliton amplitudes. A comparison with numerical simulation results shows good agreement. For the case of incoherent soliton interaction it is found that the dependence of the interaction strength on the amplitude difference is weak. 

  • 3.
    Anders, Berntson
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Analysis of coherent and incoherent interactions of amplitude shifted solitons in optical fibres1998Report (Other academic)
    Abstract [en]

    Nonlinear interaction between pulses can severely reduce the bit-rate of an optical communication system. One way of reducing this interaction is amplitude shifting of consecutive pulses. In the present work a detailed analytical and numerical investigation is made of the coherent and incoherent interactions between two soliton pulses of unequal amplitudes. For the case of coherent interaction the obtained expressions for the pulse parameters in terms of initial phase and amplitude differences give a clear and explicit prediction of the reduction of the interaction strength for unequal soliton amplitudes. A comparison with numerical simulation results shows good agreement. For the case of incoherent soliton interaction it is found that the dependence of the interaction strength on the amplitude difference is weak.

  • 4.
    Anders, Berntson
    et al.
    Aston University, UK; Chalmers University of Technology, Sweden.
    Doran, N. J.
    Aston University, UK.
    Forysiak, W.
    Aston University, UK.
    Nijhof, J. H. B.
    Aston University, UK.
    Power dependence of dispersion-managed solitons for anomalous, zero, and normal path-average dispersion1998In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 23, no 12, p. 900-902Article in journal (Refereed)
    Abstract [en]

    We determine the power dependence of dispersion-managed solitons on map strength and average dispersion, using a combination of numerical simulations and the variational approach. In particular, we investigate the behavior near zero dispersion and identify the region of existence of dispersion-managed solitons in the average normal-dispersion regime.

  • 5.
    Anders, Berntson
    et al.
    Aston University, UK.
    Doran, N. J.
    Aston University, UK.
    Forysiak, W.
    Aston University, UK.
    Nijhof, J. H. B.
    Aston University, UK.
    Power dependence of dispersion-managed solitons for anomalous, zero, and normal path-average dispersion1998Report (Other academic)
    Abstract [en]

    We determine the power dependence of dispersion-managed solitons on map strength and average dispersion, using a combination of numerical simulations and the variational approach. In particular, we investigate the behavior near zero dispersion and identify the region of existence of dispersion-managed solitons in the average normal-dispersion regime.

  • 6.
    Anders, Berntson
    et al.
    Chalmers University of Technology, Sweden.
    Malomed, Boris A.
    Chalmers University of Technology, Sweden.
    Dispersion management with filtering1998Report (Other academic)
    Abstract [en]

    We present results of analytical and numerical consideration of the pulses in a model of a DM fiber link including the fixed-frequency filters and compensating gain, both taken in the distributed approximation. Combining the variational approximation and perturbative treatment of the filtering and gain terms, we predict stationary propagation regimes. The most important new features are the absence of the minimum DM strength necessary for the existence of the pulses in the case when the average dispersion is nil or normal, and the existence of a minimum necessary normalized power in this case. These features are well corroborated by direct simulations.

  • 7.
    Anderson, D.
    et al.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Exact Schrödinger Solitons in Optical Fibers in the Presence of Space Dependent Damping or Amplification1999In: Physica scripta. T, ISSN 0281-1847, Vol. 82, p. 42-43Article in journal (Refereed)
    Abstract [en]

    It is shown that the nonlinear Schrödinger equation describing pulse propagation in optical fibers in the presence of a properly space-tailored damping or amplification is exactly integrable. A simple transformation of variables is given which transforms the inhomogeneous nonlinear Schrödinger equation into the standard form with constant coefficients, thus generating new explicit bright and dark soliton solutions in the cases of anomalous and normal dispersion, respectively.

  • 8.
    Anderson, D.
    et al.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Quiroga-Teixeiro, M.
    Chalmers University of Technology, Sweden.
    Zamanakos, G.
    Chalmers University of Technology, Sweden; Caltech,USA.
    Fedele, R.
    Università di Napoli Federico II, Italy.
    Miele, G.
    Università di Napoli Federico II, Italy.
    A variational approach to spherical aberrations in the thermal-wave model for beam dynamics in charged particle accelerators1998In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 58, no 6, p. 608-612Article in journal (Refereed)
    Abstract [en]

    A direct variational approach involving trial functions and Ritz optimization, which has previously been found very useful in nonlinear optics, is applied to analyze the effects of spherical aberrations on the focusing properties of charged particle beams in particle colliders. As compared to conventional perturbation theory, the variational approach provides a simple and physically clear analysis. Explicit expressions are given for the transverse particle beam density, the spot size, and the luminosity reduction factor at the interaction point, in good agreement with the perturbative results. 

  • 9.
    Anderson, D.
    et al.
    Chalmers University of Technology, Sweden; INFN, Italy.
    Fedele, R.
    INFN, Italy.
    Vaccaro, V.
    INFN, Italy.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Johanson, S.
    Chalmers University of Technology, Sweden.
    Modulational instabilities within the thermal wave model description of high energy charged particle beam dynamics1999In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 258, no 4-6, p. 244-248Article in journal (Refereed)
    Abstract [en]

    Within the thermal wave model (TWM) description, an investigation was made of the longitudinal instability properties of a coasting high energy charged particle beam, where the interaction between the beam and its surroundings is characterized in terms of a complex impedance. The analysis is shown to correctly reproduce the characteristic features of the coherent instability as obtained previously by conventional techniques based on the Vlasov equation for the beam distribution. The results further validate the TWM approach as a consistent alternative description for analyzing the dynamics of high energy charged particle beams.

  • 10.
    Anderson, D.
    et al.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Ericsson Telcom AB, Sweden.
    A variational approach to nonlinear evolution equations in optics2001In: Pramana (Bangalore), ISSN 0304-4289, E-ISSN 0973-7111, Vol. 57, no 5-6, p. 917-936Article in journal (Refereed)
    Abstract [en]

    The use of direct variational methods based on Rayleigh-Ritz optimization for finding approximate solutions to various nonlinear evolution equations was presented. The main advantage of the approach is that it provides simple and explicit expressions for physically relevant quantities where exact analytical solutions are not available. It is found that the given method is flexible and can be applied to stationary and dynamical problems.

  • 11.
    Anusuyadevi, Prasaanth
    et al.
    KTH Royal Institute of Technology, Sweden.
    Shanker, Ravi
    Linköping University, Sweden.
    Cui, Yuxiao
    KTH Royal Institute of Technology, Sweden.
    Riazanova, Anastasia
    KTH Royal Institute of Technology, Sweden.
    Järn, Mikael
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Jonsson, Magnus
    Linköping University, Sweden.
    Svagan, Anna
    KTH Royal Institute of Technology, Sweden.
    Photoresponsive and Polarization-Sensitive Structural Colors from Cellulose/Liquid Crystal Nanophotonic Structures2021In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 33, no 36, article id 2101519Article in journal (Refereed)
    Abstract [en]

    Cellulose nanocrystals (CNCs) possess the ability to form helical periodic structures that generate structural colors. Due to the helicity, such self-assembled cellulose structures preferentially reflect left-handed circularly polarized light of certain colors, while they remain transparent to right-handed circularly polarized light. This study shows that combination with a liquid crystal enables modulation of the optical response to obtain light reflection of both handedness but with reversed spectral profiles. As a result, the nanophotonic systems provide vibrant structural colors that are tunable via the incident light polarization. The results are attributed to the liquid crystal aligning on the CNC/glucose film, to form a birefringent layer that twists the incident light polarization before interaction with the chiral cellulose nanocomposite. Using a photoresponsive liquid crystal, this effect can further be turned off by exposure to UV light, which switches the nematic liquid crystal into a nonbirefringent isotropic phase. The study highlights the potential of hybrid cellulose systems to create self-assembled yet advanced photoresponsive and polarization-tunable nanophotonics. © 2021 The Authors.

  • 12.
    Axner, Ove
    et al.
    Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    Forssén, Clayton
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Assessment of gas molar density by gas modulation refractometry: A review of its basic operating principles and extraordinary performance2021In: Spectrochimica Acta Part B - Atomic Spectroscopy, ISSN 0584-8547, E-ISSN 1873-3565, Vol. 179, article id 106121Article in journal (Refereed)
    Abstract [en]

    A technique for high-precision and high-accuracy assessment of both gas molar (and number) density and pressure, Gas Modulation Refractometry (GAMOR), is presented. The technique achieves its properties by assessing refractivity as a shift of a directly measurable beat frequency by use of Fabry-Perot cavity (FPC) based refractometry utilizing the Pound-Drever-Hall laser locking technique. Conventional FPC-based refractometry is, however, often limited by fluctuations and drifts of the FPC. GAMOR remedies this by an additional utilization of a gas modulation methodology, built upon a repeated filling and evacuation of the measurement cavity together with an interpolation of the empty cavity responses. The procedure has demonstrated an ability to reduce the influence of drifts in a non-temperature stabilized dual-FPC (DFPC)-based refractometry system, when assessing pressure, by more than three orders of magnitude. When applied to a DFPC system with active temperature stabilization, it has demonstrated, for assessment of pressure of N2 at 4304 Pa at room temperature, which corresponds to a gas molar density of 1.7 × 10−6 mol/cm3, a sub-0.1 ppm precision (i.e. a resolution of 0.34 mPa). It is claimed that the ability to assess gas molar density is at least as good as so far has been demonstrated for pressure (i.e. for the molar density addressed, a resolution of at least 1.2 × 10−13 mol/cm3). It has recently been argued that the methodology should be capable of providing an accuracy that is in the low ppm range. These levels of precision and accuracy are unprecedented among laser-based techniques for detection of atomic and molecular species. Since the molar polarizability of He can be calculated by ab initio quantum mechanical calculations with sub-ppm accuracy, it can also be used as a primary or semi-primary standard of both gas molar (and number) density and pressure. © 2021 The Author(s)

  • 13.
    Bai, Xiaohong
    et al.
    Northwest University, China; Carleton University, Canada.
    Claesson, Åsa
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Laronche, Albane
    Carleton University, Canada.
    Liu, Fu
    Carleton University, Canada.
    Hu, Manli
    Northwest University, China.
    Albert, Jaques
    Carleton University, Canada.
    Sensing applications of fiber Bragg gratings in single mode fibers with as-drawn 25 μm diameter cladding2021In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 144, article id 107451Article in journal (Refereed)
    Abstract [en]

    The sensing properties of fiber Bragg gratings (FBG) inscribed in single mode fiber with a 5 μm diameter core and 25 μm diameter cladding are studied experimentally for temperature, strain, bending, and surrounding refractive index. Compared to normal single mode fiber, the diameter of this fiber is 5 times smaller and it stretches 14.5 times more at the same applied load. Therefore, it is much more flexible and stretchable, while maintaining excellent optical quality at wavelengths near 1550 nm. In addition to a core mode back reflection resonance, strong FBGs inscribed in this fiber show a relatively small number of narrow bandwidth (0.7 nm) cladding mode resonances separated in wavelength by 2.5–6 nm. This relatively coarse spectral comb can then be used to sense many different kinds of perturbations involving core and cladding modes. In particular, unlike cladding-mode based sensors made from tilted FBGs, all resonances are of the same azimuthal order as the core mode (i.e. HE1m). This feature makes these gratings particularly sensitive to bending which causes the appearance of new resonances and reduced amplitudes of the original ones, each by up to 10 dB/mm−1 of curvature. On the other hand, the temperature sensitivities of all modes are similar to that of standard fiber (around 11 pm/oC) while strain sensitivities are somewhat higher (1.6–1.7 pm/μstrain). The surrounding refractive index sensitivity is also increased (by a factor of 3) over normal fiber, mostly due to the increased modal dispersion of the modes of the thinner cladding. Furthermore, it is possible to serially multiplex different gratings at different wavelengths by interleaving their resonance combs and preserving each grating identity in the combined spectrum.

  • 14.
    Basse, Nils Tångefjord
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    The Chimera Revisited: Wall- and Magnetically-Bounded Turbulent Flows2024In: Fluids, E-ISSN 2311-5521, Vol. 9, no 2, p. 34-34Article in journal (Refereed)
    Abstract [en]

    This review is a first attempt at bringing together various concepts from research on wall- and magnetically-bounded turbulent flows. Brief reviews of both fields are provided: The main similarities identified are coherent (turbulent) structures, flow generation, and transport barriers. Examples are provided and discussed.

    Download full text (pdf)
    fulltext
  • 15.
    Battelier, Baptiste
    et al.
    Université de Bordeaux, France.
    Zelan, Martin
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Exploring the foundations of the physical universe with space tests of the equivalence principle2021In: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 51, no 3, p. 1695-1736Article in journal (Refereed)
    Abstract [en]

    We present the scientific motivation for future space tests of the equivalence principle, and in particular the universality of free fall, at the 10− 17 level or better. Two possible mission scenarios, one based on quantum technologies, the other on electrostatic accelerometers, that could reach that goal are briefly discussed. This publication is a White Paper written in the context of the Voyage 2050 ESA Call for White Papers. © 2021, The Author(s).

  • 16.
    Bergstrand, Sten
    et al.
    RISE - Research Institutes of Sweden, Safety and Transport, Measurement Science and Technology.
    Ralf, Schmid
    German Geodetic Research Institute, Germany.
    Activities of the IERS Working Group on Site Survey and Co-location2016In: International VLBI Service for Geodesy and Astrometry 2016 General Meeting Proceedings: "New Horizons with VGOS" / [ed] Dirk Behrend, Karen D. Baver, and Kyla L. Armstrong, Greenbelt, MD: National Aeronautics and Space Administration , 2016, p. 113-117Conference paper (Other academic)
    Abstract [en]

    The objective of the International Earth Rotation and Reference Systems Service (IERS) Working Group on Site Survey and Co-location is to improve local measurements at space geodesy sites. We appointed dedicated Points of Contact (POC) with the four different services of IERS as well as the NASA Space Geodesy Project in order to improve the efficiency of internal communication within the working group. Following the REFAG2014 conference, the POCs agreed on a common and general terminology on local ties that clarifies the communication regarding site surveying and co-location issues between and within the IERS services. We give brief introductions to the different observation techniques and mention some contemporary issues related to site surveying and co-location.

  • 17.
    Burger, Paul
    et al.
    Chalmers University of Technology, Sweden; Johannes Gutenberg University Mainz, Germany.
    Singh, G.
    Chalmers University of Technology, Sweden; Institute of Materials Science of Barcelona , Spain.
    Johansson, Christer
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware. Chalmers University of Technology, Sweden.
    Moya, Carlos
    Université Libre de Bruxelles, Belgium.
    Bruylants, Gilles
    Université Libre de Bruxelles, Belgium.
    Jakob, Gerhard
    Johannes Gutenberg University Mainz, Germany.
    Kalaboukhov, Alexei
    Chalmers University of Technology, Sweden.
    Atomic Force Manipulation of Single Magnetic Nanoparticles for Spin-Based Electronics2022In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 16, no 11, p. 19253-19260Article in journal (Refereed)
    Abstract [en]

    Magnetic nanoparticles (MNPs) are instrumental for fabrication of tailored nanomagnetic structures, especially where top-down lithographic patterning is not feasible. Here, we demonstrate precise and controllable manipulation of individual magnetite MNPs using the tip of an atomic force microscope. We verify our approach by placing a single MNP with a diameter of 50 nm on top of a 100 nm Hall bar fabricated in a quasi-two-dimensional electron gas (q2DEG) at the oxide interface between LaAlO3 and SrTiO3 (LAO/STO). A hysteresis loop due to the magnetic hysteresis properties of the magnetite MNPs was observed in the Hall resistance. Further, the effective coercivity of the Hall resistance hysteresis loop could be changed upon field cooling at different angles of the cooling field with respect to the measuring field. The effect is associated with the alignment of the MNP magnetic moment along the easy axis closest to the external field direction across the Verwey transition in magnetite. Our results can facilitate experimental realization of magnetic proximity devices using single MNPs and two-dimensional materials for spin-based nanoelectronics. © 2022 The Authors. 

  • 18.
    Bybee, Connor
    et al.
    University of California, USA.
    Kleyko, Denis
    RISE Research Institutes of Sweden, Digital Systems, Data Science. University of California, USA.
    Nikonov, Dmitri E
    Intel, USA.
    Khosrowshahi, A.
    University of California, USA; Intel, USA.
    Olshausen, B. A.
    University of California, USA.
    Sommer, F. T.
    University of California, USA; Intel, USA.
    Efficient optimization with higher-order ising machines2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, article id 6033Article in journal (Refereed)
    Abstract [en]

    A prominent approach to solving combinatorial optimization problems on parallel hardware is Ising machines, i.e., hardware implementations of networks of interacting binary spin variables. Most Ising machines leverage second-order interactions although important classes of optimization problems, such as satisfiability problems, map more seamlessly to Ising networks with higher-order interactions. Here, we demonstrate that higher-order Ising machines can solve satisfiability problems more resource-efficiently in terms of the number of spin variables and their connections when compared to traditional second-order Ising machines. Further, our results show on a benchmark dataset of Boolean k-satisfiability problems that higher-order Ising machines implemented with coupled oscillators rapidly find solutions that are better than second-order Ising machines, thus, improving the current state-of-the-art for Ising machines. 

  • 19.
    Cattani, F.
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Effect of self-phase modulation in chirped-pulse-amplification-like schemes1999In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 16, no 11, p. 1874-1879Article in journal (Refereed)
    Abstract [en]

    A detailed analytical investigation is made of the effect of nonlinear self-phase modulation in chirped-pulse-amplification-like schemes. It is demonstrated that self-phase modulation in the amplifier between the stretcher and the compressor breaks the dispersive sign symmetry of the configuration. This implies that, although self-phase modulation is usually considered a deleterious effect, different situations are possible, depending on the parameter regimes considered. In particular, the influence of self-phase modulation on the low-intensity wings of the compressed pulse may be more or less deleterious, depending on the dispersive sign combination of the stretcher and the compressor; in certain parameter regimes, it may in fact even enhance the pulse compression. 

  • 20.
    Chakraborty, Smita
    et al.
    Lund University, Sweden.
    Lönnblad, Leif
    Lund University, Sweden.
    Impact of string interactions on the space–time evolution of hadronic vertices2023In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 83, no 6, article id 464Article in journal (Refereed)
  • 21.
    Coppel, L.G.
    et al.
    RISE, Innventia.
    Andersson, M.
    Edström, P.
    Determination of quantum efficiency in fluorescing turbid media2011In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, no 17, p. 2784-2792Article in journal (Refereed)
  • 22.
    Coppel, L.G.
    et al.
    RISE, Innventia.
    Andersson, M.
    Edström, P.
    Kinnunen, J.
    Limitations in the efficiency of fluorescent whitening agents in uncoated paper2011In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, no 3, p. 319-328Article in journal (Refereed)
  • 23.
    Coppel, L.G.
    et al.
    RISE, Innventia.
    Neuman, M.
    Edström, P.
    Extension of the Stokes equation for layered constructions to fluorescent turbid media2012In: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, no 4, p. 574-578Article in journal (Refereed)
  • 24.
    Coppel, L.G.
    et al.
    RISE, Innventia.
    Neuman, M.
    Edström, P.
    Lateral light scattering in paper: MTF simulation and measurement2011In: Optics Express, E-ISSN 1094-4087, no 25, p. 25181-25187Article in journal (Refereed)
  • 25.
    Coppel, Ludovic Gustafsson
    et al.
    Gjøvik University College, Norway.
    Andersson, Mattias
    Mid Sweden University, Sweden.
    Norberg, Ole
    Mid Sweden University, Sweden.
    Lindberg, Siv
    RISE, Innventia.
    Impact of illumination spectral power distribution on radiance factor of fluorescing materials2013Conference paper (Refereed)
    Abstract [en]

    The spectral radiance factor and thereby the appearance of fluorescing material is known to depend strongly on the spectral power distribution (SPD) of the illumination in the fluorophore's excitation wavelength band. The present work demonstrates the impact of the SPD in the fluorescence emission band on the total radiance factor. The total radiance factor of a fluorescing paper is measured in three different illuminations. The presence of peaks in the SPD of fluorescent light tubes dramatically decreases the luminescent radiance factor. This effect will impact the appearance of fluorescing media under illuminations with large variation in SPD, which includes recent LED illuminations.

  • 26.
    Coronel, Edvin
    et al.
    Universidade Federal de Pernambuco, Brazil.
    Das, Avishek
    Universidade Federal de Pernambuco, Brazil.
    Gonzalez, Ivan
    RISE Research Institutes of Sweden.
    Gomes, Anderson
    KTH Royal Institute of Technology, Sweden.
    Margulis, Walter
    Pontifical Catholic University of Rio de Janeiro, Brazil.
    Von Der Weid, JP
    Universidade Federal de Pernambuco, Brazil.
    Raposo, Ernesto
    Universidade Federal de Pernambuco, Brazil.
    Evaluation of Pearson correlation coefficient and Parisi parameter of replica symmetry breaking in a hybrid electronically addressable random fiber laser2021In: Optics Express, E-ISSN 1094-4087, Vol. 29, no 15, p. 24422-24433Article in journal (Refereed)
    Abstract [en]

    The hybrid electronically addressable random (HEAR) laser is a novel type of random fiber laser that presents the remarkable property of selection of the fiber section with lasing emission. Here we present a joint analysis of the correlations between intensity fluctuations at distinct wavelengths and replica symmetry breaking (RSB) behavior of the HEAR laser. We introduce a modified Pearson coefficient that simultaneously comprises both the Parisi overlap parameter and standard Pearson correlation coefficient. Our results highlight the contrast between the correlations and presence or not of RSB phenomenon in the spontaneous emission behavior well below threshold, replica-symmetric ASE regime slightly below threshold, and RSB phase with random lasing emission above threshold. In particular, in the latter we find that the onset of RSB behavior is accompanied by a stochastic dynamics of the lasing modes, leading to competition for gain intertwined with correlation and anti-correlation between modes in this complex photonic phase. 

  • 27.
    Corpolongo, A.
    et al.
    University of Cincinnati, USA.
    Siljeström, Sandra
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Abbey, W.
    California Institution of Technology, USA.
    SHERLOC Raman Mineral Class Detections of the Mars 2020 Crater Floor Campaign2023In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 128, no 3, article id e2022JE007455Article in journal (Refereed)
    Abstract [en]

    The goals of NASA's Mars 2020 mission include searching for evidence of ancient life on Mars, studying the geology of Jezero crater, understanding Mars' current and past climate, and preparing for human exploration of Mars. During the mission's first science campaign, the Perseverance rover's SHERLOC deep UV Raman and fluorescence instrument collected microscale, two-dimensional Raman and fluorescence images on 10 natural (unabraded) and abraded targets on two different Jezero crater floor units: Séítah and Máaz. We report SHERLOC Raman measurements collected during the Crater Floor Campaign and discuss their implications regarding the origin and history of Séítah and Máaz. The data support the conclusion that Séítah and Máaz are mineralogically distinct igneous units with complex aqueous alteration histories and suggest that the Jezero crater floor once hosted an environment capable of supporting microbial life and preserving evidence of that life, if it existed. 

  • 28.
    Culleton, Lucy
    et al.
    NPL National Physical Laboratory, UK.
    Di Meane, Elena
    NPL National Physical Laboratory, UK.
    Ward, Michael
    NPL National Physical Laboratory, UK.
    Ferracci, Valerio
    NPL National Physical Laboratory, UK.
    Persijn, Stefan
    VSL, Netherlands.
    Holmqvist, Albin
    RISE Research Institutes of Sweden, Safety and Transport, Control and Calibration.
    Arrhenius, Karine
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Murugan, Arul
    NPL National Physical Laboratory, UK.
    Brewer, Paul
    NPL National Physical Laboratory, UK.
    Characterization of Fourier Transform Infrared, Cavity Ring-Down Spectroscopy, and Optical Feedback Cavity-Enhanced Absorption Spectroscopy Instruments for the Analysis of Ammonia in Biogas and Biomethane2022In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 94, no 44, p. 15207-15214Article in journal (Refereed)
    Abstract [en]

    Novel traceable analytical methods and reference gas standards were developed for the detection of trace-level ammonia in biogas and biomethane. This work focused on an ammonia amount fraction at an upper limit level of 10 mg m-3(corresponding to approximately 14 μmol mol-1) specified in EN 16723-1:2016. The application of spectroscopic analytical methods, such as Fourier transform infrared spectroscopy, cavity ring-down spectroscopy, and optical feedback cavity-enhanced absorption spectroscopy, was investigated. These techniques all exhibited the necessary ammonia sensitivity at the required 14 μmol mol-1amount fraction. A 29-month stability study of reference gas mixtures of 10 μmol mol-1ammonia in methane and synthetic biogas is also reported. 

  • 29.
    Dely, H.
    et al.
    CNRS, France.
    Joharifar, M.
    KTH Royal Institute of Technology, Sweden.
    Pang, Xiaodan
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems. KTH Royal Institute of Technology, Sweden.
    Gacemi, D.
    CNRS, France.
    Salgals, T.
    Riga Technical University, Latvia.
    Schatz, R.
    KTH Royal Institute of Technology, Sweden.
    Sun, Y. -T
    KTH Royal Institute of Technology, Sweden.
    Bonazzi, T.
    CNRS, France.
    Rodriguez, E.
    CNRS, France.
    Todorov, Y.
    CNRS, France.
    Vasanelli, A.
    CNRS, France.
    Udalcovs, Aleksejs
    RISE Research Institutes of Sweden.
    Spolitis, S.
    Riga Technical University, Latvia.
    Bobrovs, V.
    Riga Technical University, Latvia.
    Ozolins, Oskars
    RISE Research Institutes of Sweden, Digital Systems, Industrial Systems.
    Popov, Sergei
    KTH Royal Institute of Technology, Sweden.
    Sirtori, C.
    CNRS, France.
    High bitrate data transmission in the 8-14 µm atmospheric window using an external Stark-effect modulator with digital equalization2023In: Optics Express, E-ISSN 1094-4087, Vol. 31, no 5, p. 7259-7264Article in journal (Refereed)
    Abstract [en]

    High bitrate mid-infrared links using simple (NRZ) and multi-level (PAM-4) data coding schemes have been realized in the 8 µm to 14 µm atmospheric transparency window. The free space optics system is composed of unipolar quantum optoelectronic devices, namely a continuous wave quantum cascade laser, an external Stark-effect modulator and a quantum cascade detector, all operating at room-temperature. Pre- and post-processing are implemented to get enhanced bitrates, especially for PAM-4 where inter-symbol interference and noise are particularly detrimental to symbol demodulation. By exploiting these equalization procedures, our system, with a full frequency cutoff of 2 GHz, has reached transmission bitrates of 12 Gbit/s NRZ and 11 Gbit/s PAM-4 fulfilling the 6.25 % overhead hard-decision forward error correction threshold, limited only by the low signal-to-noise ratio of our detector. 

  • 30.
    Demidova, S. I.
    et al.
    Vernadsky Institute of Geochemistry and Analytical Chemistry, Russia.
    Whitehouse, M. J.
    Swedish Museum of Natural History, Sweden.
    Merle, R.
    Uppsala University, Sweden.
    Nemchin, A. A.
    Swedish Museum of Natural History, Sweden; Curtin University, Australia.
    Kenny, G. G.
    Swedish Museum of Natural History, Sweden.
    Brandstätter, F.
    Natural History Museum, Austria.
    Ntaflos, T.
    Vienna University, Austria.
    Dobryden, Illia
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    A micrometeorite from a stony asteroid identified in Luna 16 soil2022In: Nature Astronomy, E-ISSN 2397-3366, Vol. 6, no 5, p. 560-567Article in journal (Refereed)
    Abstract [en]

    Despite the intense cratering history of the Moon, very few traces of meteoritic material have been identified in the more than 380 kg of samples returned to Earth by the Apollo and Luna missions. Here we show that an ~200-µm-sized fragment collected by the Luna 16 mission has extra-lunar origins and probably originates from an LL chondrite with similar properties to near-Earth stony asteroids. The fragment has not experienced temperatures higher than 400 °C since its protolith formed early in the history of the Solar System. It arrived on the Moon, either as a micrometeorite or as the result of the break-up of a bigger impact, no earlier than 3.4 Gyr ago and possibly around 1 Gyr ago, an age that would be consistent with impact ages inferred from basaltic fragments in the Luna 16 sample and of a known dynamic upheaval in the Flora asteroid family, which is thought to be the source of L and LL chondrite meteorites. These results highlight the importance of extra-lunar fragments in constraining the impact history of the Earth–Moon system and suggest that material from LL chondrite asteroids may be an important component. © 2022, The Author(s)

  • 31.
    Deriushkina, Ekaterina
    et al.
    Chalmers University of Technology, Sweden.
    Rebolledo-Salgado, Israel
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology. Chalmers University of Technology, Sweden.
    Mazur, Mikael
    Nokia Bell Labs, USA.
    Torres-Company, Victor
    Chalmers University of Technology, Sweden.
    Andrekson, Peter
    Chalmers University of Technology, Sweden.
    Schroder, Jochen
    Chalmers University of Technology, Sweden.
    Karlsson, Magnus
    Chalmers University of Technology, Sweden.
    Dual-Comb Swept-Wavelength Interferometry: Theory and Experiment2022In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 40, no 19, p. 6508-6516Article in journal (Refereed)
    Abstract [en]

    Much efforts have been put to elaborate and improve different high precision measurement schemes for characterization of advanced photonic devices and optical fibers with increasing bandwidth requirements. In light of this, swept-wavelength interferometry and dual-comb spectroscopy have been extensively applied in characterization procedures. In this paper we present in detail an experimental scheme that combines these two techniques and overcomes their limitations by using a tunable laser source in order to sweep over the frequency comb spacing and capture all intermediate frequencies. We demonstrate full-field broadband measurements over 1.25 THz comb bandwidth with increased frequency resolution, which can be performed in only 5 ms sweep. We also show that the nonlinearity of the laser sweep can be removed without an auxiliary interferometer in the setup. 

  • 32.
    Dimitrevski, K.
    et al.
    Chalmers University of Technology, Sweden.
    Reimhult, E.
    Chalmers University of Technology, Sweden.
    Svensson, E.
    Chalmers University of Technology, Sweden.
    Öhgren, A.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Quiroga-Teixeiro, M. L.
    Chalmers University of Technology, Sweden.
    Analysis of stable self-trapping of laser beams in cubic-quintic nonlinear media1998In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 248, no 5-6, p. 369-376Article in journal (Refereed)
    Abstract [en]

    A numerical and analytical analysis of two-dimensional laser beam propagation in cubic-quintic nonlinear optical media demonstrates the existence of stable stationary radially symmetric modes. By means of a variational method, involving super-Gaussian trial functions and Ritz optimization, approximate stationary solutions are obtained, showing very good agreement with numerical results, even in the strongly non-linear, almost saturated, regime. The stability of the stationary modes are verified by analytical analysis and by direct numerical simulations. 

  • 33.
    Dominguez, Armand
    et al.
    Lund University, Sweden.
    Borggren, Jesper
    Beamonics AB, Sweden.
    Xu, Can
    Beamonics AB, Sweden.
    Otxoterena, Paul
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.
    Försth, Michael
    RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety. Luleå University of Technology, Sweden.
    Leffler, Tomas
    Vattenfall AB, Sweden; Chalmers University of Technology, Sweden.
    Bood, Joakim
    Lund University, Sweden.
    A compact Scheimpflug lidar imaging instrument for industrial diagnostics of flames2023In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 34, no 7, article id 075901Article in journal (Refereed)
    Abstract [en]

    Scheimpflug lidar is a compact alternative to traditional lidar setups. With Scheimpflug lidar it is possible to make continuous range-resolved measurements. In this study we investigate the feasibility of a Scheimpflug lidar instrument for remote sensing in pool flames, which are characterized by strong particle scattering, large temperature gradients, and substantial fluctuations in particle distribution due to turbulence. An extinction coefficient can be extracted using the information about the transmitted laser power and the spatial extent of the flame. The transmitted laser power is manifested by the intensity of the ‘echo’ from a hard-target termination of the beam located behind the flame, while the information of the spatial extent of the flame along the laser beam is provided by the range-resolved scattering signal. Measurements were performed in heptane and diesel flames, respectively. © 2023 The Author(s). 

  • 34.
    Dupuis, Pascal
    et al.
    University of Toulouse, France.
    Silalahi, Zivion O.
    University of Toulouse, France; Bandung Institute of Technology, Indonesia; PLN Perusahaan Listrik Negara, Indonesia.
    Svensson, Ingemar
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Brundin, Johannes
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Sinisuka, Ngapuli I.
    Bandung Institute of Technology, Indonesia.
    Zissis, Georges
    University of Toulouse, France.
    Performance changes of energy saving lamps under lumen maintenance and switching stress test2016In: 2016 IEEE Industry Applications Society Annual Meeting, 2016, article id 7731893Conference paper (Refereed)
    Abstract [en]

    White LED lamp are gaining a lot of popularity both on the residential and street lighting markets. Those devices are advertised with a very long lifetime compared to conventional incandescent lamps. A measurement campaign including accelerated ageing and stress test is ongoing in Sweden; parts of the data are joined to data obtained in France. The aim of this paper is to report and analyze which factors can be correlated to LED performance changes. A few commercial lamps were bought anonymously in retail stores; each type comprised 12 samples. A first group undergo long-term lumen maintenance test; the second was stressed by frequent switching (50 000 cycles, 30 seconds on/30 second off); the third and the fourth by frequent cycling (3 000 cycles, 30 minutes on/30 minutes off) at 25 °C and 75°C respectively. The assesment are made based on the change of the lumen, lamp efficiency, Correlated Color Temperature and Color Rendering index of the produced light before and after the test.

  • 35.
    Duvefelt, Kenneth
    et al.
    KTH Royal Institute of Technology, Sweden.
    Olofsson, Ulf
    KTH Royal Institute of Technology, Sweden.
    Johannesson, Carl Michael
    KTH Royal Institute of Technology, Sweden.
    Skedung, Lisa
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, p. 389-394Article in journal (Refereed)
    Abstract [en]

    One of the main parameters affecting finger friction, friction-induced vibrations in the finger, and consequently tactility is surface topography. Recently Skedung et al. performed finger friction measurements on fine controlled surfaces. These surfaces were sinusoidal with wavelengths from 0.27 to 8.8 μm and amplitudes from 0.007 to 6 μm. Building on those tests an analytical model for the contact was developed to explain the differences in friction coefficient. The contact was modelled as trapezoids in a circular pattern pressed against a sinusoidal plane. Results showed that the calculated contact area and therefore friction coefficient corresponded well with the measurements. This model can be used to see how the different surface parameters influence friction.

  • 36.
    Eneborg, Alexander
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Improvement and Characterization of Aqueous Graphene Dispersions2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Graphene has many outstanding properties which make it a prime candidate for new technology. At the current time it is very difficult and expensive to produce large sheets of graphene, but there are many applications where that is not necessary and smaller flakes of graphene can be used instead. A practical way of handling these graphene flakes is in a dispersion, especially a water-based dispersion have many benefits. Such a stable dispersion of functionalized graphene is produced, improved, and characterized in this project. An aqueous system that was developed in two previous M.Sc. theses, each determining a suitable graphene powder and stabilizer, was used as a starting point with the main purpose being to improve the yield. The method used to produce these dispersions can be described as sonicating graphene powder in a solution of water and stabilizer followed by centrifuging to remove un-dispersed graphene particles. Experiments were carried out examining the possibility of dispersing those previously undispersed graphene flakes, combining the stabilizer with several surfactants, optimizing the centrifuge speed and time, refining the sonication procedure with longer exposure time and cooling, narrowing the size-distribution of the original stabilizer through ultrafiltration, and removing excessive unbound stabilizer through ultrafiltration. Samples were characterized with UV-vis, SEM, TGA, Electrophoretic light scattering, and Laser diffraction spectroscopy. It was discovered that the yield from the graphene powder was heavily dependent on sonication time and centrifugation conditions. The gain from increasing sonication time showed that most, if not all, of the un-dispersed graphene flakes previously considered lost could in fact be dispersed. In an industrial setting any un-dispersed flakes could simply be added to the next batch. Reducing the centrifugation speed as well as time increased the concentration of graphene to more than twice as high, and that gain comes solely from the larger graphene flakes. Thusly the previous problem with a low yield was shown to have been caused by too little sonication and too much centrifugation. The particle size analysis did show a small reduction in flake size as the sonication time was increased, but when those dispersions were characterized in SEM they all formed even films with no discernable difference between them. Purifying the scaled up dispersions by removing excess stabilizer through ultrafiltration was performed to three different degrees, 0 %, 50 % and 95 %, for a total of three dispersions of 100ml. All three dispersions were shown to be highly stable, with no apparent reduction in graphene concentration over 5 weeks and a zeta potential averaging below -50mV. The TGA results reinforce the UV-vis results, proving that the purification worked as intended.

  • 37.
    Fallqvist, Björn
    et al.
    KTH Royal Institute of Technology, Sweden.
    Fielden, Matthew L.
    KTH Royal Institute of Technology, Sweden.
    Pettersson, Torbjörn
    KTH Royal Institute of Technology, Sweden.
    Niklas, Nordgren
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Kroon, Martin
    KTH Royal Institute of Technology, Sweden.
    Gad, Annica K. B.
    Karolinska Institute, Sweden.
    Experimental and computational assessment of F-actin influence in regulating cellular stiffness and relaxation behaviour of fibroblasts2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 59, p. 168-184Article in journal (Refereed)
    Abstract [en]

    In biomechanics, a complete understanding of the structures and mechanisms that regulate cellular stiffness at a molecular level remain elusive. In this paper, we have elucidated the role of filamentous actin (F-actin) in regulating elastic and viscous properties of the cytoplasm and the nucleus. Specifically, we performed colloidal-probe atomic force microscopy (AFM) on BjhTERT fibroblast cells incubated with Latrunculin B (LatB), which results in depolymerisation of F-actin, or DMSO control. We found that the treatment with LatB not only reduced cellular stiffness, but also greatly increased the relaxation rate for the cytoplasm in the peripheral region and in the vicinity of the nucleus. We thus conclude that F-actin is a major determinant in not only providing elastic stiffness to the cell, but also in regulating its viscous behaviour. To further investigate the interdependence of different cytoskeletal networks and cell shape, we provided a computational model in a finite element framework. The computational model is based on a split strain energy function of separate cellular constituents, here assumed to be cytoskeletal components, for which a composite strain energy function was defined. We found a significant influence of cell geometry on the predicted mechanical response. Importantly, the relaxation behaviour of the cell can be characterised by a material model with two time constants that have previously been found to predict mechanical behaviour of actin and intermediate filament networks. By merely tuning two effective stiffness parameters, the model predicts experimental results in cells with a partly depolymerised actin cytoskeleton as well as in untreated control. This indicates that actin and intermediate filament networks are instrumental in providing elastic stiffness in response to applied forces, as well as governing the relaxation behaviour over shorter and longer time-scales, respectively.

  • 38.
    Faraz, S. M.
    et al.
    University of Engineering and Technology, Pakistan.
    Un Nabi Jafri, S. R.
    University of Engineering and Technology, Pakistan.
    Khan, H. R.
    University of Engineering and Technology, Pakistan.
    Shah, W.
    University of Engineering and Technology, Pakistan.
    Ul Hassan Alvi, Naveed
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Ul Wahab, Q.
    Linköping University, Sweden.
    Nur, O.
    Linköping University, Sweden.
    Effect of annealing temperature on the interface state density of n-ZnO nanorod/p-Si heterojunction diodes2021In: Open Physics, ISSN 2391-5471, Vol. 19, no 1, p. 467-476Article in journal (Refereed)
    Abstract [en]

    The effect of post-growth annealing treatment of zinc oxide (ZnO) nanorods on the electrical properties of their heterojunction diodes (HJDs) is investigated. ZnO nanorods are synthesized by the low-temperature aqueous solution growth technique and annealed at temperatures of 400 and 600°C. The as-grown and annealed nanorods are studied by scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Electrical characterization of the ZnO/Si heterojunction diode is done by current–voltage (I–V) and capacitance–voltage (C–V) measurements at room temperature. The barrier height (ϕB), ideality factor (n), doping concentration and density of interface states (NSS) are extracted. All HJDs exhibited a nonlinear behavior with rectification factors of 23, 1,596 and 309 at ±5 V for the as-grown, 400 and 600°C-annealed nanorod HJDs, respectively. Barrier heights of 0.81 and 0.63 V are obtained for HJDs of 400 and 600°C-annealed nanorods, respectively. The energy distribution of the interface state density has been investigated and found to be in the range 0.70 × 1010 to 1.05 × 1012 eV/cm2 below the conduction band from EC = 0.03 to EC = 0.58 eV. The highest density of interface states is observed in HJDs of 600°C-annealed nanorods. Overall improved behavior is observed for the heterojunctions diodes of 400°C-annealed ZnO nanorods. © 2021 Sadia Muniza Faraz et al.

  • 39.
    Faraz, Sadia
    et al.
    NED University of Engineering and Technology, Pakistan.
    Jafri, Syed
    NED University of Engineering and Technology, Pakistan.
    Tajvar, Zarreen
    NED University of Engineering and Technology, Pakistan.
    Ul Hassan Alvi, Naveed
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Wahab, Qamar
    Linkoping University, Sweden.
    Nur, Omer
    Linkoping University, Sweden.
    Effect of annealing atmosphere on the diode behaviourof zno/si heterojunction2021In: Elektronika ir Elektrotechnika, ISSN 1392-1215, Vol. 27, no 4, p. 49-54Article in journal (Refereed)
    Abstract [en]

    The effect of thermal annealing atmosphere on the electrical characteristics of Zinc oxide (ZnO) nanorods/p-Silicon (Si) diodes is investigated. ZnO nanorods are grown by low-temperature aqueous solution growth method and annealed in Nitrogen and Oxygen atmosphere. As-grown and annealed nanorods are studied by scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Electrical characteristics of ZnO/Si heterojunction diodes are studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. Improvements in rectifying behaviour, ideality factor, carrier concentration, and series resistance are observed after annealing. The ideality factor of 4.4 for as-grown improved to 3.8 and for Nitrogen and Oxygen annealed improved to 3.5 nanorods diodes. The series resistances decreased from 1.6 to 1.8 times after annealing. An overall improved behaviour is observed for oxygen annealed heterojunction diodes. The study suggests that by controlling the ZnO nanorods annealing temperatures and atmospheres the electronic and optoelectronic properties of ZnO devices can be improved.

  • 40.
    Fellinger, Joris
    et al.
    Max Planck Institute for Plasma Physics, Germany.
    Richou, M.
    CEA Institute for Magnetic Fusion Research, France.
    Ehrke, G.
    Max Planck Institute for Plasma Physics, Germany.
    Endler, M.
    Max Planck Institute for Plasma Physics, Germany.
    Kunkel, F.
    Max Planck Institute for Plasma Physics, Germany.
    Naujoks, D.
    Max Planck Institute for Plasma Physics, Germany.
    Kremeyer, Th.
    Max Planck Institute for Plasma Physics, Germany.
    Menzel-Barbara, A.
    Max Planck Institute for Plasma Physics, Germany.
    Sieber, Th.
    Max Planck Institute for Plasma Physics, Germany.
    Lobsien, J-F
    Max Planck Institute for Plasma Physics, Germany.
    Neu, R.
    Max Planck Institute for Plasma Physics, Germany.
    Tretter, J.
    Max Planck Institute for Plasma Physics, Germany.
    Wang, Z.
    Max Planck Institute for Plasma Physics, Germany.
    You, J-H
    Max Planck Institute for Plasma Physics, Germany.
    Greuner, H.
    Max Planck Institute for Plasma Physics, Germany.
    Hunger, K.
    Max Planck Institute for Plasma Physics, Germany.
    Junghanns, P.
    Max Planck Institute for Plasma Physics, Germany.
    Schneider, O.
    Max Planck Institute for Plasma Physics, Germany.
    Wirtz, M.
    Forschungszentrum Jülich GmbH, Germany.
    Loewenhoff, Th.
    Forschungszentrum Jülich GmbH, Germany.
    Houben, A.
    Forschungszentrum Jülich GmbH, Germany.
    Litnovsky, A.
    Forschungszentrum Jülich GmbH, Germany.
    Fraysinnes, P-E
    CEA LITEN DTCH LCA, France.
    Emonot, P.
    CEA LITEN DTCH LCA, France.
    Roccella, S.
    ENEA Frascati Research Centre, Itay.
    Widlund, Ola
    RISE Research Institutes of Sweden, Materials and Production, Applied Mechanics.
    Koncar, B.
    Jožef Stefan Institute, Slovenia.
    Tekavčič, M.
    Jožef Stefan Institute, Slovenia.
    Tungsten based divertor development for Wendelstein 7-X2023In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 37, article id 101506Article in journal (Refereed)
    Abstract [en]

    Wendelstein 7-X, the world’s largest superconducting stellarator in Greifswald (Germany), started plasma experiments with a water-cooled plasma-facing wall in 2022, allowing for long pulse operation. In parallel, a project was launched in 2021 to develop a W based divertor, replacing the current CFC divertor, to demonstrate plasma performance of a stellarator with a reactor relevant plasma facing materials with low tritium retention. The project consists of two tasks: Based on experience from the previous experimental campaigns and improved physics modelling, the geometry of the plasma-facing surface of the divertor and baffles is optimized to prevent overloads and to improve exhaust. In parallel, the manufacturing technology for a W based target module is qualified. This paper gives a status update of project. It focusses on the conceptual design of a W based target module, the manufacturing technology and its qualification, which is conducted in the framework of the EUROfusion funded WPDIV program. A flat tile design in which a target module is made of a single target element is pursued. The technology must allow for moderate curvatures of the plasma-facing surface to follow the magnetic field lines. The target element is designed for steady state heat loads of 10 MW/m2 (as for the CFC divertor). Target modules of a similar size and weight as for the CFC divertor are assumed (approx. < 0.25 m2 and < 60 kg) using the existing water cooling infrastructure providing 5 l/s and roughly maximum 15 bar pressure drop per module. The main technology under qualification is based on a CuCrZr heat sink made either by additive manufacturing using laser powder bed fusion (LPBF) or by uniaxial diffusion welding of pre-machined forged CuCrZr plates. After heat treatment, the plasma-facing side of the heat sink is covered by W or if feasible by the more ductile WNiFe, preferably by coating or alternatively by hot isostatic pressing W based tiles with a soft OFE-Cu interlayer. Last step is a final machining of the plasma-exposed surface and the interfaces to the water supply lines and supports to correct manufacturing deformations.

  • 41.
    Forssén, Clayton
    et al.
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Silander, I.
    Umeå University, Sweden.
    Zakrisson, J.
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Axner, O.
    Umeå University, Sweden.
    Fabry-Perot-cavity-based refractometry without influence of mirror penetration depth2021In: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 39, no 6, article id 065001Article in journal (Refereed)
    Abstract [en]

    Assessments of refractivity in a Fabry-Perot (FP) cavity by refractometry often encompass a step in which the penetration depth of the light into the mirrors is estimated to correct for the fraction of the cavity length into which no gas can penetrate. However, as it is currently carried out, this procedure is not always coherently performed. Here, we discuss a common pitfall that can be a reason for this and provide a recipe on how to perform FP-cavity-based refractometry without any influence of mirror penetration depth. © 2021 Author(s).

  • 42.
    Fray, Nicolas
    et al.
    CNRS, France; Paris Diderot University, France.
    Bardyn, Anaïs
    CNRS, France; Paris Diderot University, France; University of Orléans, France.
    Cottin, Hervé
    CNRS, France; Paris Diderot University, France.
    Altwegg, Kathrin
    University of Bern, Switzerland.
    Baklouti, Donia
    CNRS, France; University of Paris-Sud, France.
    Briois, Christelle
    CNRS, France; University of Orléans, France.
    Colangeli, Luigi
    ESTEC European Space Research and Technology Centre, The Netherlands.
    Engrand, Cécile
    CNRS, France; University of Paris-Saclay, France; University of Paris-Sud, France.
    Fischer, Henning
    Max Planck Institute for Solar System Research, Germany.
    Glasmachers, Albrecht
    University of Wuppertal, Germany.
    Grün, Eberhard
    Max Planck Institute for Nuclear Physics, Germany.
    Haerendel, Gerhard
    Max Planck Institute for Extraterrestrial Physics, Germany.
    Henkel, Hartmut
    Von Hoerner und Sulger GmbH, Germany.
    Höfner, Herwig
    Max Planck Institute for Extraterrestrial Physics, Germany.
    Hornung, Klaus
    Universität der Bundeswehr, Germany.
    Jessberger, Elmar K.
    University of Münster, Germany.
    Koch, Andreas
    Von Hoerner und Sulger GmbH, Germany.
    Krüger, Harald
    Max Planck Institute for Solar System Research, Germany.
    Langevin, Yves
    CNRS, France; University of Paris-Sud, France.
    Lehto, Harry
    University of Turku, Finland.
    Lehto, Kirsi
    University of Turku, Finland.
    Le Roy, Léna
    University of Bern, Switzerland.
    Merouane, Sihane
    Max Planck Institute for Solar System Research, Germany.
    Modica, Paola
    CNRS, France; Paris Diderot University, France; University of Orléans, France.
    Orthous-Daunay, François-Régis
    CNRS, France; Université Grenoble Alpes, France.
    Paquette, John
    Max Planck Institute for Solar System Research, Germany.
    Raulin, François
    CNRS, France; Paris Diderot University, France.
    Rynö, Jouni
    Finnish Meteorological Institute, Finland.
    Schulz, Rita
    ESA European Space Agency, The Netherlands.
    Silén, Johan
    Finnish Meteorological Institute, Finland.
    Siljeström, Sandra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Medicinteknik.
    Steiger, Wolfgang
    RC Seibersdorf Research GmbH Business Field Aerospace Technology, Austria.
    Stenzel, Oliver
    Max Planck Institute for Solar System Research, Germany.
    Stephan, Thomas
    University of Chicago, USA.
    Thirkell, Laurent
    CNRS, France; University of Orléans, France.
    Thomas, Roger
    CNRS, France; University of Orléans, France.
    Torkar, Klaus
    Austrian Academy of Sciences, Austria.
    Varmuza, Kurt
    Vienna University of Technology, Austria.
    Wanczek, Karl-Peter
    University of Bremen, Germany.
    Zaprudin, Boris
    University of Turku, Finland.
    Kissel, Jochen
    Max Planck Institute for Solar System Research, Germany.
    Hilchenbach, Martin
    Max Planck Institute for Solar System Research, Germany.
    High-molecular-weight organic matter in the particles of comet 67P/Churyumov–Gerasimenko2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 538, no 7623, p. 72-74Article in journal (Refereed)
    Abstract [en]

    The presence of solid carbonaceous matter in cometary dust was established by the detection of elements such as carbon, hydrogen, oxygen and nitrogen in particles from comet 1P/Halley1, 2. Such matter is generally thought to have originated in the interstellar medium3, but it might have formed in the solar nebula—the cloud of gas and dust that was left over after the Sun formed4. This solid carbonaceous material cannot be observed from Earth, so it has eluded unambiguous characterization5. Many gaseous organic molecules, however, have been observed6, 7, 8, 9; they come mostly from the sublimation of ices at the surface or in the subsurface of cometary nuclei8. These ices could have been formed from material inherited from the interstellar medium that suffered little processing in the solar nebula10. Here we report the in situ detection of solid organic matter in the dust particles emitted by comet 67P/Churyumov–Gerasimenko; the carbon in this organic material is bound in very large macromolecular compounds, analogous to the insoluble organic matter found in the carbonaceous chondrite meteorites11, 12. The organic matter in meteorites might have formed in the interstellar medium and/or the solar nebula, but was almost certainly modified in the meteorites’ parent bodies11. We conclude that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but suffered less modification before and/or after being incorporated into the comet.

  • 43.
    Fries, M. D.
    et al.
    NASA Johnson Space Center, USA.
    Siljeström, Sandra
    RISE Research Institutes of Sweden, Materials and Production, Product Realisation Methodology.
    Aileen Yingst, R.
    Planetary Science Institute, USA.
    The SHERLOC Calibration Target on the Mars 2020 Perseverance Rover: Design, Operations, Outreach, and Future Human Exploration Functions2022In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 218, no 6, article id 46Article in journal (Refereed)
    Abstract [en]

    The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is a robotic arm-mounted instrument onboard NASA’s Perseverance rover. SHERLOC combines imaging via two cameras with both Raman and fluorescence spectroscopy to investigate geological materials at the rover’s Jezero crater field site. SHERLOC requires in situ calibration to monitor the health and performance of the instrument. These calibration data are critically important to ensure the veracity of data interpretation, especially considering the extreme martian environmental conditions where the instrument operates. The SHERLOC Calibration Target (SCT) is located at the front of the rover and is exposed to the same atmospheric conditions as the instrument. The SCT includes 10 individual targets designed to meet all instrument calibration requirements. An additional calibration target is mounted inside the instrument’s dust cover. The targets include polymers, rock, synthetic material, and optical pattern targets. Their primary function is calibration of parameters within the SHERLOC instrument so that the data can be interpreted correctly. The SCT was also designed to take advantage of opportunities for supplemental science investigations and includes targets intended for public engagement. The exposure of materials to martian atmospheric conditions allows for opportunistic science on extravehicular suit (i.e., “spacesuit”) materials. These samples will be used in an extended study to produce direct measurements of the expected service lifetimes of these materials on the martian surface, thus helping NASA facilitate human exploration of the planet. Other targets include a martian meteorite and the first geocache target to reside on another planet, both of which increase the outreach and potential of the mission to foster interest in, and enthusiasm for, planetary exploration. During the first 200 sols (martian days) of operation on Mars, the SCT has been analyzed three times and has proven to be vital in the calibration of the instrument and in assisting the SHERLOC team with interpretation of in situ data. © 2022, The Author(s).

  • 44.
    Fu, Ying
    et al.
    Halmstad University, Sweden.
    Yager, Tom
    University of Latvia, Latvia.
    Chikvaidze, George
    University of Latvia, Latvia.
    Iyer, Srinivasan
    Senseair AB, Sweden.
    Wang, Qin
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Time-Resolved FDTD and Experimental FTIR Study of Gold Micropatch Arrays for Wavelength-Selective Mid-Infrared Optical Coupling2021In: Sensors, E-ISSN 1424-8220, Vol. 21, no 15, article id 5203Article in journal (Refereed)
    Abstract [en]

    Infrared radiation reflection and transmission of a single layer of gold micropatch two-dimensional arrays, of patch length ∼1.0μm and width ∼0.2μm, have been carefully studied by a finite-difference time-domain (FDTD) method, and Fourier-transform infrared spectroscopy (FTIR). Through precision design of the micropatch array structure geometry, we achieve a significantly enhanced reflectance (85%), a substantial diffraction (10%), and a much reduced transmittance (5%) for an array of only 15% surface metal coverage. This results in an efficient far-field optical coupling with promising practical implications for efficient mid-infrared photodetectors. Most importantly we find that the propagating electromagnetic fields are transiently concentrated around the gold micropatch array in a time duration of tens of ns, providing us with a novel efficient near-field optical coupling.

  • 45.
    Gerasimov, Jennifer
    et al.
    Linköping University, Sweden.
    Halder, Arnnab
    Linköping University, Sweden.
    Mousa, Abdelrazek
    University of Gothenburg, Sweden.
    Ghosh, Sarbani
    Birla Institute of Technology and Science, India.
    Harikesh, Pardinhabe
    Linköping University, Sweden.
    Abrahamsson, Tobias
    Linköping University, Sweden.
    Bliman, David
    University of Gothenburg, Sweden.
    Strandberg, Jan
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Massetti, Matteo
    Linköping University, Sweden.
    Zozoulenko, Igor
    Linköping University, Sweden.
    Simon, Daniel
    Linköping University, Sweden.
    Berggren, Magnus
    Linköping University, Sweden.
    Olsson, Roger
    Lund University, Sweden; University of Gothenburg, Sweden.
    Fabiano, Simone
    Linköping University, Sweden.
    Rational Materials Design for In Operando Electropolymerization of Evolvable Organic Electrochemical Transistors2022In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 32, article id 2202292Article in journal (Refereed)
    Abstract [en]

    Organic electrochemical transistors formed by in operando electropolymerization of the semiconducting channel are increasingly becoming recognized as a simple and effective implementation of synapses in neuromorphic hardware. However, very few studies have reported the requirements that must be met to ensure that the polymer spreads along the substrate to form a functional conducting channel. The nature of the interface between the substrate and various monomer precursors of conducting polymers through molecular dynamics simulations is investigated, showing that monomer adsorption to the substrate produces an increase in the effective monomer concentration at the surface. By evaluating combinatorial couples of monomers baring various sidechains with differently functionalized substrates, it is shown that the interactions between the substrate and the monomer precursor control the lateral growth of a polymer film along an inert substrate. This effect has implications for fabricating synaptic systems on inexpensive, flexible substrates. © 2022 The Authors. 

  • 46.
    Goetz, W.
    et al.
    Max Planck Institute for Solar System Research, Germany.
    Brinckerhoff, W. B.
    NASA, US.
    Arevalo, R.
    NASA, US.
    Freissinet, C.
    NASA, US.
    Getty, S.
    NASA, US.
    Glavin, D. P.
    NASA, US.
    Siljeström, Sandra
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Medicinteknik.
    Buch, A.
    Ecole Centrale Paris, France.
    Stalport, F.
    Ecole Centrale Paris, France.
    Grubisic, A.
    LISA Laboratoire Interuniversitaire des Systèmes Atmosphériques, France.
    Li, X.
    NASA, US.
    Pinnick, V.
    NASA, US.
    Danell, R.
    NASA, US.
    Van Amerom, F. H. W.
    LISA Laboratoire Interuniversitaire des Systèmes Atmosphériques, France; Danell Consulting, US.
    Goesmann, F.
    Mini-Mass Consulting, US.
    Steininger, H.
    Max Planck Institute for Solar System Research, Germany.
    Grand, N.
    Max Planck Institute for Solar System Research, Germany.
    Raulin, F.
    LISA Laboratoire Interuniversitaire des Systèmes Atmosphériques, France, France.
    Szopa, C.
    LATMOS, France.
    Meierhenrich, U.
    University of Nice, France.
    Brucato, J. R.
    INAF Astrophysical Observatory of Arcetri, Italy; University of Bremen, Germany.
    MOMA: The challenge to search for organics and biosignatures on Mars2016In: International Journal of Astrobiology, ISSN 1473-5504, E-ISSN 1475-3006, Vol. 15, no 3, p. 239-250Article in journal (Refereed)
    Abstract [en]

    This paper describes strategies to search for, detect, and identify organic material on the surface and subsurface of Mars. The strategies described include those applied by landed missions in the past and those that will be applied in the future. The value and role of ESA's ExoMars rover and of her key science instrument Mars Organic Molecule Analyzer (MOMA) are critically assessed.

  • 47.
    Hall, B.
    et al.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Boyer, G.
    Ecole Polytechnique, France.
    Karlsson, M.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Ericsson Telecom AB, Sweden.
    Pump-probe collision in optical fibers: Four-wave-mixing induced frequency jump2001In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 18, no 11, p. 1652-1658Article in journal (Refereed)
    Abstract [en]

    An investigation is made of ultrafast pump-probe pulse collisions near the zero-dispersion wavelength in an optical single-mode fiber. A steplike probe frequency shift is observed when the pump power is gradually increased. The magnitude of this frequency jump is shown to depend on the phase difference between the pulses. This new effect is investigated numerically and experimentally and is attributed to four-wave mixing.

  • 48.
    He, Hans
    et al.
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Cedergren, Karin
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Shetty, Naveen
    Chalmers University of Technology, Sweden.
    Lara-Avila, Samuel
    Chalmers University of Technology, Sweden; NPL, UK.
    Kubatkin, Sergey
    Chalmers University of Technology, Sweden.
    Bergsten, Tobias
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Eklund, Gunnar
    RISE Research Institutes of Sweden, Safety and Transport, Measurement Technology.
    Accurate graphene quantum Hall arrays for the new International System of Units2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 6933Article in journal (Refereed)
    Abstract [en]

    Graphene quantum Hall effect (QHE) resistance standards have the potential to provide superior realizations of three key units in the new International System of Units (SI): the ohm, the ampere, and the kilogram (Kibble Balance). However, these prospects require different resistance values than practically achievable in single graphene devices (~12.9 kΩ), and they need bias currents two orders of magnitude higher than typical breakdown currents IC ~ 100 μA. Here we present experiments on quantization accuracy of a 236-element quantum Hall array (QHA), demonstrating RK/236 ≈ 109 Ω with 0.2 part-per-billion (nΩ/Ω) accuracy with IC ≥ 5 mA (~1 nΩ/Ω accuracy for IC = 8.5 mA), using epitaxial graphene on silicon carbide (epigraphene). The array accuracy, comparable to the most precise universality tests of QHE, together with the scalability and reliability of this approach, pave the road for wider use of graphene in the new SI and beyond. © 2022, The Author(s).

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  • 49.
    Helczynski, L.
    et al.
    Chalmers University of Technology, Sweden.
    Hall, B.
    Chalmers University of Technology, Sweden.
    Anderson, D.
    Chalmers University of Technology, Sweden.
    Lisak, M.
    Chalmers University of Technology, Sweden.
    Anders, Berntson
    Ericsson Telecom AB, Sweden.
    Desaix, M.
    Cross Phase Modulation Induced Pulse Splitting - The Optical Axe2000In: Physica scripta. T, ISSN 0281-1847, Vol. 84, p. 81-84Article in journal (Refereed)
    Abstract [en]

    An analytical as well as numerical analysis is made of the dynamics induced on a weak signal wave pulse by a co-propagating strong pump wave pulse in a nonlinear Kerr medium. Emphasis is given to the situation where the group velocity dispersion and the non-linearity of the signal pulse have opposite signs. In this defocusing situation, it is demonstrated that the pump splits the signal pulse into two frequency shifted pulse fragments which separate in time, asymptotically with constant separation velocity. Explicit analytical predictions for the velocity of separation are obtained and corroborated by numerical simulations.

  • 50.
    Heydari, Golrokh
    et al.
    KTH Royal Institute of Technology, Sweden.
    Sedighi Moghaddam, Maziar
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. KTH Royal Institute of Technology, Sweden.
    Tuominen, Mikko
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Fielden, Matthew
    KTH Royal Institute of Technology, Sweden.
    Haapanen, Janne
    TUT Tampere University of Technology, Finland.
    Mäkelä, Jyrki M.
    TUT Tampere University of Technology, Finland.
    Claesson, Per M.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. KTH Royal Institute of Technology, Sweden.
    Wetting hysteresis induced by temperature changes: Supercooled water on hydrophobic surfaces2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 468, p. 21-33Article in journal (Refereed)
    Abstract [en]

    The state and stability of supercooled water on (super)hydrophobic surfaces is crucial for low temperature applications and it will affect anti-icing and de-icing properties. Surface characteristics such as topography and chemistry are expected to affect wetting hysteresis during temperature cycling experiments, and also the freezing delay of supercooled water. We utilized stochastically rough wood surfaces that were further modified to render them hydrophobic or superhydrophobic. Liquid flame spraying (LFS) was utilized to create a multi-scale roughness by depositing titanium dioxide nanoparticles. The coating was subsequently made non-polar by applying a thin plasma polymer layer. As flat reference samples modified silica surfaces with similar chemistries were utilized. With these substrates we test the hypothesis that superhydrophobic surfaces also should retard ice formation. Wetting hysteresis was evaluated using contact angle measurements during a freeze-thaw cycle from room temperature to freezing occurrence at -7 °C, and then back to room temperature. Further, the delay in freezing of supercooled water droplets was studied at temperatures of -4 °C and -7 °C. The hysteresis in contact angle observed during a cooling-heating cycle is found to be small on flat hydrophobic surfaces. However, significant changes in contact angles during a cooling-heating cycle are observed on the rough surfaces, with a higher contact angle observed on cooling compared to during the subsequent heating. Condensation and subsequent frost formation at sub-zero temperatures induce the hysteresis. The freezing delay data show that the flat surface is more efficient in enhancing the freezing delay than the rougher surfaces, which can be rationalized considering heterogeneous nucleation theory. Thus, our data suggests that molecular flat surfaces, rather than rough superhydrophobic surfaces, are beneficial for retarding ice formation under conditions that allow condensation and frost formation to occur.

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