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  • 1.
    Abbasiasl, Taher
    et al.
    Sabanci University.
    Niazi, Soroush
    Sabanci University.
    Sheibani Aghdam, Araz
    Sabanci University.
    Chen, Hongjian
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging.
    Cebeci, Fevzi Cakmak
    Sabanci University.
    Ghorbani, Morteza
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging. 1 Sabanci University Nanote.
    Grishenkov, Dmitry
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging.
    Kosar, Ali
    Sabanci University.
    Effect of intensified cavitation using poly (vinyl alcohol) microbubbles on spray atomization characteristics in microscale2020In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 10, no 2Article in journal (Refereed)
    Abstract [en]

    In this study, cavitating flows inside a transparent cylindrical nozzle with an inner diameter of 0.9 mm were visualized, and the effect of cavitation on atomization characteristics of emerging sprays was investigated. Different patterns of cavitating flows inside the nozzle were visualized using a high-speed camera. In-house codes were developed to process the captured images to study the droplet size distribution and droplet velocity in different flow regimes. The results show that cavitating flows at the microscale have significant effects on atomization characteristics of the spray. Two working fluids, namely, water and poly(vinyl alcohol) microbubble (PVA MB) suspension, were employed. Accordingly, the injection pressures were detected as 690 kPa, 1035 kPa, and 1725 kPa for cavitation inception, supercavitation, and hydraulic flip flow regimes in the case of water, respectively. The corresponding pressures for the aforementioned patterns for PVA MB suspension were 590 kPa, 760 kPa, and 1070 kPa, respectively. At the microscale, as a result of a higher volume fraction of cavitation bubbles inside the nozzle, there is no large difference between the cavitation numbers corresponding to cavitating and hydraulic flip flows. Although the percentage of droplets with diameters smaller than 200 μm was roughly the same for both cases of water and PVA MB suspension, the Sauter mean diameter was considerably lower in the case of PVA MBs. Moreover, higher droplet velocities were achieved in the case of PVA MBs at lower injection pressures.

  • 2.
    Bondarenko, Artem
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Holmgren, Erik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Koop, Björn C.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Descamps, Thomas
    KTH.
    Ivanov, B. A.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Stochastic dynamics of strongly-bound magnetic vortex pairs2017In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 5, article id 056007Article in journal (Refereed)
    Abstract [en]

    We demonstrate that strongly-bound spin-vortex pairs exhibit pronounced stochastic behaviour. Such dynamics is due to collective magnetization states originating from purely dipolar interactions between the vortices. The resulting thermal noise exhibits telegraph-like behaviour, with random switching between different oscillation regimes observable at room temperature. The noise in the system is further studied by varying the external field and observing the related changes in the frequency of switching and the probability for different magnetic states and regimes. Monte Carlo simulations are used to replicate and explain the experimental observations.

  • 3. Dhaka, Veer
    et al.
    Perros, Alexander
    Naureen, Shagufta
    Shahid, Naeem
    Jiang, Hua
    Kakko, Joona-Pekko
    Haggren, Tuomas
    Kauppinen, Esko
    Srinivasan, Anand
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
    Lipsanen, Harri
    Protective capping and surface passivation of III-V nanowires by atomic layer deposition2016In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 6, no 1, article id 015016Article in journal (Refereed)
    Abstract [en]

    Low temperature (similar to 200 degrees C) grown atomic layer deposition (ALD) films of AlN, TiN, Al2O3, GaN, and TiO2 were tested for protective capping and surface passivation of bottom-up grown III-V (GaAs and InP) nanowires (NWs), and top-down fabricated InP nanopillars. For as-grown GaAs NWs, only the AlN material passivated the GaAs surface as measured by photoluminescence (PL) at low temperatures (15K), and the best passivation was achieved with a few monolayer thick (2 angstrom) film. For InP NWs, the best passivation (similar to 2x enhancement in room-temperature PL) was achieved with a capping of 2nm thick Al2O3. All other ALD capping layers resulted in a de-passivation effect and possible damage to the InP surface. Top-down fabricated InP nanopillars show similar passivation effects as InP NWs. In particular, capping with a 2 nm thick Al2O3 layer increased the carrier decay time from 251 ps (as-etched nanopillars) to about 525 ps. Tests after six months ageing reveal that the capped nanostructures retain their optical properties. Overall, capping of GaAs and InP NWs with high-k dielectrics AlN and Al2O3 provides moderate surface passivation as well as long term protection from oxidation and environmental attack.

  • 4. Fan, W.
    et al.
    Fu, Q.
    Qian, Q.
    Chen, Q.
    Liu, W.
    Zhou, X.
    Yuan, H.
    Yue, J.
    Huang, Z.
    Jiang, Sheng
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. Southeast University, China.
    Kou, Z.
    Zhai, Y.
    Investigation of magnetization dynamics damping in Ni80Fe20/Nd-Cu bilayer at room temperature2018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 5, article id 056325Article in journal (Refereed)
    Abstract [en]

    Focusing on the Ni80Fe20 (Py)/Nd-Cu bilayers, the magnetization dynamic damping from spin pumping effect is investigated systematically by doping itinerant Cu in rear earth metal Nd. Various Ta/Py/Nd1-xCux/Ta/Si films with x = 0%, 16%, 38%, 46% and 58% are prepared by magnetron sputtering. For every content of Cu, the thickness of Nd-Cu layer is changed from 1 nm to 32 nm. The damping coefficient increases with increasing the thickness of Nd-Cu layer, which shows the trend of the spin pumping behavior. Also, with increasing Cu concentration in the Nd-Cu layer, the damping coefficient decreases, implying that the spin-orbit coupling in Nd-Cu layer is indeed cut down by high itinerant of Cu dopants. It is interesting that the spin diffusion length (λSD) in the Nd-Cu layer for different Cu dopants is not found to increase monotonously.

  • 5.
    Fu, Jie
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory. Ningbo Univ, Peoples R China; Dalian Univ Technol, Peoples R China.
    Zhao, Jijun
    Plyasunov, Andrey V.
    Belonoshko, Anatoly
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory.
    Ab initio molecular dynamics study of fluid H2O-CO2 mixture in broad pressure-temperature range2017In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 11, article id 115217Article in journal (Refereed)
    Abstract [en]

    Properties of H2O and CO2 fluid and their mixtures under extreme pressures and temperatures are poorly known yet critically important in a number of applications. Several hundreds of first-principles molecular dynamics (FPMD) runs have been performed to obtain the pressure-volume-temperature (P-V-T) data on supercritical H2O, CO2, and H2O-CO2 mixtures. The pressure-temperature (P-T) range are from 0.5 GPa to 104 GPa (48.5 GPa for CO2) and from 600 K to 4000 K. Based on these data, we evaluate several existing equations of state (EOS) for the fluid H2O, CO2, and H2O-CO2 mixture. The results show that the EOS for H2O from Belonoshko et al. [Geochim. Cosmochim. Acta 55, 381-387; Geochim. Cosmochim. Acta 55, 3191-3208; Geochim. Cosmochim. Acta 56, 3611-3626; Comput. Geosci. 18, 1267-1269] not only can be used in the studied P-T range but also is accurate enough to be used for prediction of P-V-T data. In addition, IAPWS-95 EOS for H2O shows excellent extrapolation behavior beyond 1.0 GPa and 1273 K. However, for the case of CO2, none of the existing EOS produces data in agreement with the FPMD results. We created new EOS for CO2. The precision of the new EOS is tested by comparison to the calculated P-V-T data, fugacity coefficient of the CO2 fluid derived from high P-T experimental data as well as to the (very scarce) experimental volumetric data in the high P-T range. On the basis of our FPMD data we created a new EOS for H2O-CO2 mixture. The new EOS for the mixture is in reasonable agreement with experimental data.

  • 6.
    Grishin, Alexander M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits. Petrozavodsk State University, Russian Federation .
    Jalalian, Abolfazl
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits. INMATECH Intelligent Materials Technology, Sweden.
    Tsindlekht, M. I.
    Gadolinia nanofibers as a multimodal bioimaging and potential radiation therapy agent2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 5, article id 057104Article in journal (Refereed)
    Abstract [en]

    Continuous bead-free C-type cubic gadolinium oxide (Gd2O3) nanofibers 20-30 mu m long and 40-100 nm in diameter were sintered by sol-gel calcination assisted electrospinning technique. Dipole-dipole interaction of neighboring Gd3+ ions in nanofibers with large length-to-diameter aspect ratio results in some kind of superparamagnetic behavior: fibers are magnetized twice stronger than Gd2O3 powder. Being compared with commercial Gd-DTPA/Magnevist (R), Gd2O3 diethyleneglycol-coated (Gd2O3-DEG) fibers show high 1/T-1 and 1/T-2 proton relaxivities. Intense room temperature photoluminescence, high NMR relaxivity and high neutron scattering cross-section of Gd-157 nucleus promise to integrate Gd2O3 fibers for multimodal bioimaging and neutron capture therapy.

  • 7.
    Guo, Tingbiao
    et al.
    Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Sun, Yaoran
    Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Evans, Julian
    Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Wang, Nan
    Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Fu, Yang
    Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China.
    Thermal management with a highly emissive and thermally conductive graphite absorber2019In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 9, no 2, article id 025224Article in journal (Refereed)
    Abstract [en]

    Thermal management on a variety of length scales is essential for many industrial, solar and computational systems. Here we explore the thermal properties of a nearly perfect graphite absorber with both high emissivity and thermal conductivity which is fabricated by simple one-step etching. The hemispherical reflectance of the absorber is around 1% in the visible range and the normal specular reflectance is less than 1% from 1.5 mu m to 10 mu m. The thermal conductivity of the absorber is measured above 630 Wm(-1) K-1, which is 2.5 times larger than the aluminum used in commercial heat sinks. Heat dissipation testing indicates that a device is 3.7 +/- 2 degrees cooler with the graphite absorber as the heat spreader than a pristine graphite sheet and 9.1 +/- 2 degrees cooler than an Au-coated graphite sheet, primarily due to improved radiation cooling. A theoretical analysis accounts for the results. Further analysis suggests that the radiative heat dissipation is more prominent in the low-convection environment, especially for a convection coefficient below 10 Wm(-2) K-1. 

  • 8. Huang, Z.
    et al.
    Chen, Q.
    Jiang, Sheng
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. School of Physics, Southeast University, Nanjing 211189, P. R. China.
    Dong, S.
    Zhai, Y.
    Ab initio understanding of magnetic properties in Zn2+ substitution of Fe3O4 ultra-thin film with dilute Zn substitution2018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 5, article id 055807Article in journal (Refereed)
    Abstract [en]

    The mechanism of the magnetic properties on the Zn2+ substituted Fe3O4 film have been investigated based on first principle calculations. It is found that the surface effect plays an important role in the occupation of Zn ion, and in turn changes the magnetic moment. It may also destroy the half metallic behavior of Fe3O4 film even if the Zn2+ concentration only is one Zn2+ per unit cell (4%), which is different from that in bulk material.

  • 9. Hussain, Tanveer
    et al.
    Maark, Tuhina Adit
    Pathak, Biswarup
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Department of Physics and Astronomy, Uppsala University, SE-751 20 Uppsala, Sweden .
    Improvement in the hydrogen desorption from MgH2 upon transition metals doping: A hybrid density functional calculations2013In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 3, no 10, p. 102117-Article in journal (Refereed)
    Abstract [en]

    This study deals with the investigations of structural, electronic and thermodynamic properties of MgH2 doped with selected transition metals (TMs) by means of hybrid density functional theory (PBE0). On the structural side, the calculated lattice parameters and equilibrium volumes increase in case of Sc, Zr and Y opposite to all the other dopants indicating volumetrically increased hydrogen density. Except Fe, all the dopants improve the kinetics of MgH2 by reducing the heat of adsorption with Cu, Nb, Ni and V proving more efficient than others studied TM's. The electronic properties have been studied by density of states and correlated with hydrogen adsorption energies.

  • 10.
    Jiang, Sheng
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. NanOsc AB, S-16440 Kista, Sweden..
    Chung, Sunjae
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Diez, Liza Herrera
    Univ Paris Saclay, Univ Paris Sud, CNRS, Inst Elect Fondamentale, F-91405 Orsay, France..
    Le, Quang Tuan
    KTH, School of Engineering Sciences (SCI), Applied Physics. Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden.
    Magnusson, Fredrik
    NanOsc AB, S-16440 Kista, Sweden..
    Ravelosona, Dafine
    Univ Paris Saclay, Univ Paris Sud, CNRS, Inst Elect Fondamentale, F-91405 Orsay, France.;Spin Ion Technol, 28 Rue Gen Leclerc, F-78000 Versailles, France..
    Åkerman, Johan
    KTH, School of Engineering Sciences (SCI), Applied Physics. NanOsc AB, S-16440 Kista, Sweden.;Univ Gothenburg, Dept Phys, S-41296 Gothenburg, Sweden..
    Tuning the magnetodynamic properties of all-perpendicular spin valves using He+ irradiation2018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 6, article id 065309Article in journal (Refereed)
    Abstract [en]

    Using He+ ion irradiation, we demonstrate how the magnetodynamic properties of both ferromagnetic layers in all-perpendicular [Co/Pd]/Cu/[Co/Ni] spin valves can be tuned by varying the He+ ion fluence. As the perpendicular magnetic anisotropy of both layers is gradually reduced by the irradiation, different magnetic configurations can be achieved from all-perpendicular (up arrow up arrow), through orthogonal (->up arrow), to all in-plane (paired right arrows). In addition, both the magnetic damping (alpha) and the inhomogeneous broadening (Delta H-0) of the Co/Ni layer improve substantially with increasing fluence. While the GMR of the spin valve is negatively affected, decreasing linearly from an original value of 1.14% to 0.4% at the maximum fluence of 50x10(14) He+/cm(2), most of the Co/Ni layer improvement is achieved already at a fluence of 10x10(14) He+/cm(2), for which GMR only reduces to 0.9%.

  • 11.
    Kateb, Movaffaq
    et al.
    Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Ingvarsson, Snorri
    Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe202019In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 9, no 3, article id 035308Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of atomic ordering on the magnetic anisotropy of Ni80Fe20 at.% (Py). To this end, Py films were grown epitaxially on MgO(001) using dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS). Aside from twin boundaries observed in the latter case, both methods present high quality single crystals with cube-on-cube epitaxial relationship as verified by the polar mapping of important crystal planes. However, X-ray diffraction results indicate higher order for the dcMS deposited film towards L1(2) Ni3Fe superlattice. This difference can be understood by the very high deposition rate of HiPIMS during each pulse which suppresses adatom mobility and ordering. We show that the dcMS deposited film presents biaxial anisotropy while HiPIMS deposition gives well defined uniaxial anisotropy. Thus, higher order achieved in the dcMS deposition behaves as predicted by magnetocrystalline anisotropy i.e. easy axis along the [111] direction that forced in the plane along the [110] direction due to shape anisotropy. The uniaxial behaviour in HiPIMS deposited film then can be explained by pair ordering or more recent localized composition non-uniformity theories. Further, we studied magnetoresistance of the films along the [100] directions using an extended van der Pauw method. We find that the electrical resistivities of the dcMS deposited film are lower than in their HiPIMS counterparts verifying the higher order in the dcMS case.

  • 12.
    Koop, Björn C.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Gruschke, M.
    KTH.
    Descamps, Thomas
    KTH.
    Bondarenko, Artem
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Ivanov, B. A.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Static and dynamic properties of vortex pairs in asymmetric nanomagnets2016In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 6, no 5, article id 056406Article in journal (Refereed)
    Abstract [en]

    Stacked spin-vortex pairs in magnetic multilayered nanopillars, with vertical separation between the vortices small compared to the vortex core size and pure magnetostatic coupling, exhibit spin dynamics absent in individual vortices. This dynamics is nonlinear and is due to the strong direct core-core coupling in the system, dominating energetically for small-signal excitation. We observe and explain the appearance of spin resonance modes, forbidden within linear dynamics, and discuss how they depend on the magnetic and morphological asymmetries in the samples.

  • 13.
    Kravets, Anatolii
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Gomonay, O. V.
    Polishchuk, Dmytr
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tykhonenko-Polishchuk, Yu.O.
    Polek, T. I.
    Tovstolytkin, A. I.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Effect of nanostructure layout on spin pumping phenomena in antiferromagnet/nonmagnetic metal/ferromagnet multilayered stacks2017In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 5, article id 056312Article in journal (Refereed)
    Abstract [en]

    In this work we focus on magnetic relaxation in Mn80Ir20(12 nm)/Cu(6 nm)/Py(dF) antiferromagnet/Cu/ferromagnet (AFM/Cu/FM) multilayers with different thickness of the ferromagnetic permalloy layer. An effective FM-AFM interaction mediated via the conduction electrons in the nonmagnetic Cu spacer - the spin-pumping effect - is detected as an increase in the linewidth of the ferromagnetic resonance (FMR) spectra and a shift of the resonant magnetic field. We further find experimentally that the spin-pumping-induced contribution to the linewidth is inversely proportional to the thickness of the Py layer. We show that this thickness dependence likely originates from the dissipative dynamics of the free and localized spins in the AFM layer. The results obtained could be used for tailoring the dissipative properties of spintronic devices incorporating antiferromagnetic layers.

  • 14.
    Kudryavtsev, Daniil
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Kutcherov, Vladimir G.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Dubrovinsky, Leonid
    University of Bayreuth (Bayreth's geological institute) .
    Raman high-pressure study of butane isomers up to 40 GPa2018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 11, article id 115104Article in journal (Refereed)
    Abstract [en]

    Raman spectroscopy studies on n and i-butane were performed at pressures of up to 40 GPa at ambient temperatures using the DAC technique. Normal butane undergoes two phase transitions at 1.9(5) GPa and 2.9(5) GPa and isobutane at 2.7(5) GPa and 3.5(5) GPa. These phase transitions were identified based on observations of the splitting Raman modes and the appearance or disappearance of particular Raman peaks. Our results demonstrate the complex, high-pressure behavior of butane isomers.

  • 15. Kyaw, Htet Htet
    et al.
    Boonruang, Sakoolkan
    Mohammed, Waleed S.
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Design of electric-field assisted surface plasmon resonance system for the detection of heavy metal ions in water2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 10, article id 107226Article in journal (Refereed)
    Abstract [en]

    Surface Plasmon Resonance (SPR) sensors are widely used in diverse applications. For detecting heavy metal ions in water, surface functionalization of the metal surface is typically used to adsorb target molecules, where the ionic concentration is detected via a resonance shift (resonance angle, resonance wavelength or intensity). This paper studies the potential of a possible alternative approach that could eliminate the need of using surface functionalization by the application of an external electric field in the flow channel. The exerted electrical force on the ions pushes them against the surface for enhanced adsorption; hence it is referred to as “Electric-Field assisted SPR system”. High system sensitivity is achieved by monitoring the time dynamics of the signal shift. The ion deposition dynamics are discussed using a derived theoretical model based on ion mobility in water. On the application of an appropriate force, the target ions stack onto the sensor surface depending on the ionic concentration of target solution, ion mass, and flow rate. In the experimental part, a broad detection range of target cadmium ions (Cd 2+) in water from several parts per million (ppm) down to a few parts per billion (ppb) can be detected.

  • 16. Lansåker, Pia C.
    et al.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Niklasson, Gunnar A.
    Granqvist, Claes G.
    Characterization of gold nanoparticle films: Rutherford backscattering spectroscopy, scanning electron microscopy with image analysis, and atomic force microscopy2014In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 4, no 10, p. 107101-Article in journal (Refereed)
    Abstract [en]

    Gold nanoparticle films are of interest in several branches of science and technology, and accurate sample characterization is needed but technically demanding. We prepared such films by DC magnetron sputtering and recorded their mass thickness by Rutherford backscattering spectroscopy. The geometric thickness d(g)-from the substrate to the tops of the nanoparticles-was obtained by scanning electron microscopy (SEM) combined with image analysis as well as by atomic force microscopy (AFM). The various techniques yielded an internally consistent characterization of the films. In particular, very similar results for d(g) were obtained by SEM with image analysis and by AFM.

  • 17.
    Lindgren, G.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Conductive atomic force microscopy studies of charged domain walls in KTiOPO42018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 8, article id 085214Article in journal (Refereed)
    Abstract [en]

    We study the conductive properties of charged domain walls in KTiOPO4 using conductive atomic force microscopy. We show that the region of increased conductivity at the domain wall broadens when the wall is in motion, extending from the initial wall position to the final wall position. When wall motion stops, the conductive region attains a narrow width. The magnitude of the conductivity of charged domain walls is four times larger than that of the surrounding domains, as is the case at stationary wall. We investigate

  • 18. Moskalenko, Mariia
    et al.
    Bessarab, Pavel F.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. St. Petersburg State University, Russian Federation.
    Uzdin, Valery M.
    Jonsson, Hannes
    Qualitative insight and quantitative analysis of the effect of temperature on the coercivity of a magnetic system2016In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 6, no 2, article id 025213Article in journal (Refereed)
    Abstract [en]

    The temperature dependence of the response of a magnetic system to an applied field can be understood qualitatively by considering variations in the energy surface characterizing the system and estimated quantitatively with rate theory. In the system analysed here, Fe/Sm-Co spring magnet, the width of the hysteresis loop is reduced to a half when temperature is raised from 25 K to 300 K. This narrowing can be explained and reproduced quantitatively without invoking temperature dependence of model parameters as has typically been done in previous data analysis. The applied magnetic field lowers the energy barrier for reorientation of the magnetization but thermal activation brings the system over the barrier. A 2-dimensional representation of the energy surface is developed and used to gain insight into the transition mechanism and to demonstrate how the applied field alters the transition path. Our results show the importance of explicitly including the effect of thermal activation when interpreting experiments involving the manipulation of magnetic systems at finite temperature.

  • 19. Pogorily, A. N.
    et al.
    Kravets, Anatolii
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Nevdacha, V. V.
    Podyalovskiy, D. Y.
    Ryabchenko, S. M.
    Kalita, V. M.
    Kulik, M. M.
    Lozenko, A. F.
    Vovk, A.Ya.
    Godinho, M.
    Maurel, L.
    Pardo, J. A.
    Magen, C.
    Korenivski, V.
    Magnetic anisotropy of epitaxial Co2Fe-Ge Heusler alloy films on MgO (100) substrates2017In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 5, article id 055831Article in journal (Refereed)
    Abstract [en]

    Films of Co2Fe-Ge Heusler alloy with variable Ge concentration deposited on monocrystalline MgO (100) substrates by magnetron co-sputtering are investigated using microstructural, morphological, magnetometric, and magnetic resonance methods. The films were found to grow epitaxially, with island-like or continuous-layer morphology depending the Ge-content. The ferromagnetic resonance data versus out-of-plane and in-plane angle indicate the presence of easy plane and 4-fold in-plane anisotropy. The magnetometry data indicate additional weak 2-fold in-plane anisotropy and pronounced at low fields rotatable anisotropy. The observed magnetic anisotropy properties discussed in correlation with the microstructure and morphology of the films.

  • 20.
    Polishchuk, Dmytro M.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. NAS of Ukraine, Ukraine.
    Kravets, Anatolii F.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. NAS of Ukraine, Ukraine.
    Tykhonenko-Polishchuk, Yu.O.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tovstolytkin, A. I.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Ferromagnetic resonance and interlayer exchange coupling in magnetic multilayers with compositional gradients2017In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 5, article id 056307Article in journal (Refereed)
    Abstract [en]

    Ferromagnetic resonance (FMR) in magnetic multilayers of type F1/f/F2, where two strongly ferromagnetic layers F1 and F2 are separated by a weakly magnetic spacer f with a compositional gradient along its thickness, is investigated. The method allows to detect the weak signal from the spacer in additional to the more pronounced and readily measured signal from the outer strongly-magnetic layers, and thereby study the properties of the spacer as well as the interlayer exchange interaction it mediates. Variable temperature FMR measurements, especially near the relevant Curie points, reveal a rich set of properties of the exchange interactions in the system. The obtained results are useful for designing and optimizing nanostructures with thermally-controlled magnetic properties.

  • 21.
    Shahid, Naeem
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Amin, Muhammad
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Naureen, Shagufta
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
    Mini-stop bands in single heterojunction photonic crystal waveguides2013In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 3, no 3, p. 032136-Article in journal (Refereed)
    Abstract [en]

    Spectral characteristics of mini-stop bands (MSB) in line-defect photonic crystal (PhC) waveguides and in heterostructure PhC waveguides having one abrupt interface are investigated. Tunability of the MSB position by air-fill factor heterostructure PhC waveguides is utilized to demonstrate different filter functions, at optical communication wavelengths, ranging from resonance-like to wide band pass filters with high transmission. The narrowest filter realized has a resonance-like transmission peak with a full width at half maximum of 3.4 nm. These devices could be attractive for coarse wavelength selection (pass and drop) and for sensing applications.

  • 22. Sun, Fei
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Superposition of DC magnetic fields by cascading multiple magnets in magnetic loops2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 9, article id 097208Article in journal (Refereed)
    Abstract [en]

    A novel method that can effectively collect the DC magnetic field produced by multiple separated magnets is proposed. With the proposed idea of a magnetic loop, the DC magnetic field produced by these separated magnets can be effectively superimposed together. The separated magnets can be cascaded in series or in parallel. A novel nested magnetic loop is also proposed to achieve a higher DC magnetic field in the common air region without increasing the DC magnetic field in each magnetic loop. The magnetic loop can be made by a magnetic hose, which is designed by transformation optics and can be realized by the combination of super-conductors and ferromagnetic materials.

  • 23. Sun, Yaoran
    et al.
    Evans, Julian
    Ding, Fei
    Wang, Shaowei
    Mo, Lei
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Centre for Optical and Electromagnetic Research, Zhejiang Provincial Key Laboratory for Sensing Technologies, Zhejiang University, Hangzhou, China.
    Patterning of graphite nanocones for broadband solar spectrum absorption2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 6, article id 067139Article in journal (Refereed)
    Abstract [en]

    We experimentally demonstrate a broadband vis-NIR absorber consisting of 300-400 nm nanocone structures on highly oriented pyrolytic graphite. The nanocone structures are fabricated through simple nanoparticle lithography process and analyzed with three-dimensional finite-difference time-domain methods. The measured absorption reaches an average level of above 95% over almost the entire solar spectrum and agrees well with the simulation. Our simple process offers a promising material for solar-thermal devices.

  • 24. Talebian Gevari, Moein
    et al.
    Ghorbani, Morteza
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging.
    J. Svagan, Anna
    Grishenkov, Dmitry
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Kosar, Ali
    Energy harvesting with micro scale hydrodynamic cavitation-thermoelectric generation coupling2019In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226Article in journal (Refereed)
  • 25. Talebian Gevari, Moein
    et al.
    Ghorbani, Morteza
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging.
    Svagan, Anna Justina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Grishenkov, Dmitry
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Kosar, Ali
    Energy harvesting with micro scale hydrodynamic cavitation-thermoelectric generation coupling2019In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 9, article id 105012Article in journal (Refereed)
    Abstract [en]

    In this study, energy harvesting with micro scale hydrodynamic cavitation-thermoelectric generation coupling is investigated. For this, three micro orifices with different geometrical dimensions are fabricated. The hydraulic diameter of the micro orifices are 66.6 mu m, 75.2 mu m, and 80 mu m, while their length is the same (2000 mu m). Two different working fluids, namely water and Perfluoropentane droplet-water suspension, are utilized for cavitating flows in the fabricated micro orifices. The flow patterns at different upstream pressures are recorded using the high-speed camera system, and the experimental results are analyzed and compared. Thereafter, energy harvesting perspectives of cavitating flows are considered. The released heat from collapsing bubbles and the subsequent temperature rise on the end wall of the microchannel, which can be used as the source for the power generation, is calculated over time. Finally, a miniature energy harvesting system with cavitation system and thermoelectric generator coupling is presented. The maximum power corresponding to two different thermoelectric generators is estimated for with both working fluids and is compared with the required power to run miniature daily used electronics components.

  • 26. Thorsteinsson, D. O.
    et al.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland.
    Growth of HfN thin films by reactive high power impulse magnetron sputtering2018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 3, article id 035124Article in journal (Refereed)
    Abstract [en]

    Thin hafnium nitride films were grown on SiO2 by reactive high power impulse magnetron sputtering (HiPIMS) and reactive direct current magnetron sputtering (dcMS). The conditions during growth were kept similar and the film properties were compared as growth temperature, nitrogen flow rate, and in the case of HiPIMS, duty cycle were independently varied. The films were characterized with grazing incidence X-ray diffraction (GIXRD), X-ray reflection (XRR) and X-ray stress analysis (XSA). HiPIMS growth had a lower growth rate for all grown films, but the films surfaces were smoother. The film density of HiPIMS deposited films grown at low duty cycle was comparable to dcMS grown films. Increasing the duty cycle increased the density of the HiPIMS grown films almost to the bulk density of HfN as well as increasing the growth rate, while the surface roughness did not change significantly. The HiPIMS grown films had large compressive stress while the dcMS grown films had some tensile stress. The dcMS grown films exhibit larger grains than HiPIMS grown films. The grain size of HiPIMS grown films decreases with increasing nitrogen flow rate, while the dcMS grain size increased with increasing nitrogen flow rate. This work shows that duty cycle during HiPIMS growth of HfN films has a significant effect on the film density and growth rate while other film properties seem mostly unaffected.

  • 27.
    Vernet, Julie A
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. Scania CV AB, Sodertalje, Sweden..
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Alfredsson, P. Henrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Flow separation control by dielectric barrier discharge plasma actuation via pulsed momentum injection2018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 7, article id 075229Article in journal (Refereed)
    Abstract [en]

    Control of a turbulent boundary layer separating on a half-cylinder mounted on a flat plate has been investigated using a Dielectric Barrier Discharge (DBD) plasma actuator placed along the apex of a cylinder. The main focus of the study has been to evaluate if the control ability of the actuator can be improved through pulsed actuation compared to its steady counterpart. Investigations of the electric wind induced by the DBD plasma actuator in still air, when mounted on the flat plate, revealed that while the steady actuation produces an electric wind similar to a wall jet, the pulsed actuation creates a train of co-rotating vortices. The vortices are the result of a starting vortex produced by the actuator at each actuation pulse. A parametric study showed a dependence of the size, shape and propagation velocity of the vortices on the pulse frequency and duty cycle. With the actuator mounted along the apex of the cylinder, Particle Image Velocimetry measurements of the uncontrolled and controlled flow with a free-stream velocity of 5 m/s showed a clear reduction of the recirculation region downstream the cylinder when using plasma actuation. An even higher control effect could be achieved with pulsed actuation compared to the steady actuation. Phase-locked measurements of the unsteady actuation showed that pulsed actuation periodically shifted the flow separation location resulting in the propagation of vortical structures in the recirculation region. The size of the vortical structures showed a dependence on the pulsed actuation timing parameters.

  • 28. Wang, C.
    et al.
    Xiao, D.
    Zhou, Y.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Liu, Y.
    Phase-locking of multiple magnetic droplets by a microwave magnetic field2017In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 5, article id 056019Article in journal (Refereed)
    Abstract [en]

    Manipulating dissipative magnetic droplet is of great interest for both the fundamental and technological reasons due to its potential applications in the high frequency spin-torque nano-oscillators. In this paper, a magnetic droplet pair localized in two identical or non-identical nano-contacts in a magnetic thin film with perpendicular anisotropy can phase-lock into a single resonance state by using an oscillating microwave magnetic field. This resonance state is a little away from the intrinsic precession frequency of the magnetic droplets. We found that the phase-locking frequency range increases with the increase of the microwave field strength. Furthermore, multiple droplets with a random initial phase can also be synchronized by a microwave field.

1 - 28 of 28
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