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  • 1.
    Abbasi, Mazhar Ali
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Hussain Ibupoto, Zafar
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Hussain, Mushtaque
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    The fabrication of white light-emitting diodes using the n-ZnO/NiO/p-GaN heterojunction with enhanced luminescence2013In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 8, no 320Article in journal (Refereed)
    Abstract [en]

    Cheap and efficient white light-emitting diodes (LEDs) are of great interest due to the energy crisis all over the world. Herein, we have developed heterojunction LEDs based on the well-aligned ZnO nanorods and nanotubes on the p-type GaN with the insertion of the NiO buffer layer that showed enhancement in the light emission. Scanning electron microscopy have well demonstrated the arrays of the ZnO nanorods and the proper etching into the nanotubes. X-ray diffraction study describes the wurtzite crystal structure array of ZnO nanorods with the involvement of GaN at the (002) peak. The cathodoluminescence spectra represent strong and broad visible emission peaks compared to the UV emission and a weak peak at 425 nm which is originated from GaN. Electroluminescence study has shown highly improved luminescence response for the LEDs fabricated with NiO buffer layer compared to that without NiO layer. Introducing a sandwich-thin layer of NiO between the n-type ZnO and the p-type GaN will possibly block the injection of electrons from the ZnO to the GaN. Moreover, the presence of NiO buffer layer might create the confinement effect.

  • 2.
    Alvi, Naveed ul Hassan
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Hussain, S.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nour, Omer
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Influence of helium-ion bombardment on the optical properties of ZnO nanorods/p-GaN light emitting diodes2011In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 6, no 628Article in journal (Refereed)
    Abstract [en]

    Light emitting diodes (LEDs) based on zinc oxide (ZnO) nanorods grown by vapor-liquid-solid (VLS) catalytic growth method were irradiated with 2 MeV helium (He+) ions. The fabricated LEDs were irradiated with fluencies of ~ 2×1013 ions/cm2 and ~ 4×1013 ions/cm2. Scanning electron microscopy (SEM) images showed that the morphology of the irradiated samples is not changed. The as-grown and He+ irradiated LEDs showed rectifying behaviour with the same I-V characteristics. Photoluminescence (PL) measurements showed that there is a blue shift of approximately 0.0347 eV and 0.082 eV in the near band emission (free exciton) and green emission of the irradiated ZnO nanorods, respectively. It was also observed that the PL intensity of the near band emission was decreased after irradiation of the samples. The electroluminescence (EL) measurements of the fabricated LEDs showed that there is a blue shift of 0.125 eV in the broad green emission after irradiation and the EL intensity of violet emission approximately centred at 398 nm was nearly disappeared after irradiations. The color rendering properties shows a small decrease in the color rendering indices of 3% after 2 MeV He+ ions irradiation.

  • 3.
    Dobrovolsky, Alexander
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kuang, Y. J.
    Department of Physics, University of California, La Jolla, California, USA.
    Sukrittanon, S.
    Graduate Program of Materials Science and Engineering, La Jolla, California, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Optical properties of GaP/GaNP core/shell nanowires: a temperature-dependent study2013In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 8, no 1, p. 239-Article in journal (Refereed)
    Abstract [en]

    Recombination processes in GaP/GaNP core/shell nanowires (NWs) grown on Si are studied by employing temperature-dependent continuous wave and time-resolved photoluminescence (PL) spectroscopies. The NWs exhibit bright PL emissions due to radiative carrier recombination in the GaNP shell. Though the radiative efficiency of the NWs is found to decrease with increasing temperature, the PL emission remains intense even at room temperature. Two thermal quenching processes of the PL emission are found to be responsible for the degradation of the PL intensity at elevated temperatures: (a) thermal activation of the localized excitons from the N-related localized states and (b) activation of a competing non-radiative recombination (NRR) process. The activation energy of the latter process is determined as being around 180 meV. NRR is also found to cause a significant decrease of carrier lifetime.

  • 4.
    Nour, Eiman
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Bondarevs, Andrejs
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Huss, Patrik
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Sandberg, Mats
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. Acreo AB, Sweden.
    Gong, Shaofang
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Nour, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Low-Frequency Self-Powered Footstep Sensor Based on ZnO Nanowires on Paper Substrate2016In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 11, no 156Article in journal (Refereed)
    Abstract [en]

    In this work, we design and fabricate a wireless system with the main operating device based on zinc oxide (ZnO) nanowires. The main operating device is based on piezoelectric nanogenerator (NG) achieved using ZnO nanowires grown hydrothermally on paper substrate. The fabricated NG is capable of harvesting ambient mechanical energy from various kinds of human motion, e.g., footsteps. The harvested electric output has been used to serve as a self-powered pressure sensor. Without any storage device, the signal from a single footstep has successfully triggered a wireless sensor node circuit. This study demonstrates the feasibility of using ZnO nanowire piezoelectric NG as a low-frequency self-powered sensor, with potential applications in wireless sensor networks.

  • 5.
    Rudko, Galyna
    et al.
    National Academic Science Ukraine, Ukraine.
    Kovalchuk, Andrii
    National Academic Science Ukraine, Ukraine.
    Fediv, Volodymyr
    Bukovinian State Medical University, Ukraine.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Enhancement of polymer endurance to UV light by incorporation of semiconductor nanoparticles2015In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 10, no 81, p. 1-6Article in journal (Refereed)
    Abstract [en]

    Improvement of polyvinyl alcohol stability against ultraviolet (UV) illumination is achieved by introducing cadmium sulfide (CdS) nanoparticles into the polymeric matrix. Enhancement of stability is analyzed by optical characterization methods. UV protection is achieved by diminishing the probability of photo-activated formation of defects in polymer. The sources of polymer protection are the lowering of the efficiency of polymer excitation via partial absorption of incident light by the embedded nanoparticles as well as the de-excitation of the macromolecules that have already absorbed UV quanta via energy drain to nanoparticles. Within the nanoparticles, the energy is either dissipated by conversion to the thermal energy or reemitted as visible-range photoluminescence quanta.

  • 6.
    Rudko, Galyna Yu.
    et al.
    National Academic Science Ukraine, Ukraine.
    Vorona, Igor P.
    National Academic Science Ukraine, Ukraine.
    Fediv, Volodymyr I.
    Bukovinian State Medical University, Ukraine.
    Kovalchuk, Andrii
    National Academic Science Ukraine, Ukraine.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Shanina, Bela D.
    National Academic Science Ukraine, Ukraine.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Luminescent and Optically Detected Magnetic Resonance Studies of CdS/PVA Nanocomposite2017In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 12, article id 130Article in journal (Refereed)
    Abstract [en]

    A series of solid nanocomposites containing CdS nanoparticles in polymeric matrix with varied conditions on the interface particle/polymer was fabricated and studied by photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. The results revealed interface-related features in both PL and ODMR spectra. The revealed paramagnetic centers are concluded to be involved in the processes of photo-excited carriers relaxation.

  • 7.
    Sadaf, Jamil R
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Israr, Muhammad Q
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Ding, Yong
    Georgia Institute Technology.
    Wang, Zhong L
    Georgia Institute Technology.
    The correlation between radiative surface defect states and high color rendering index from ZnO nanotubes2011In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 6, no 513Article in journal (Refereed)
    Abstract [en]

    Combined surface, structural and opto-electrical investigations are drawn from the chemically fashioned ZnO nanotubes and its heterostructure with p-GaN film. A strong correlation has been found between the formation of radiative surface defect states in the nanotubes and the pure cool white light possessing averaged eight color rendering index value of 96 with appropriate color temperature. Highly important deep-red color index value has been realized andgt; 95 which has the capability to render and reproduce natural and vivid colors accurately. Diverse types of deep defect states and their relative contribution to the corresponding wavelengths in the broad emission band is suggested.

  • 8.
    Sen Karaman, Didem
    et al.
    Abo Akad University, Finland .
    Desai, Diti
    Abo Akad University, Finland Maharaja Sayajirao University of Baroda, India .
    Senthilkumar, Rajendran
    Abo Akad University, Finland .
    Johansson, Emma
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Ratts, Natalie
    Abo Akad University, Finland Abo Akad University, Finland Abo Akad University, Finland University of Turku, Finland .
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    E Eriksson, John
    Abo Akad University, Finland .
    Sahlgren, Cecilia
    Abo Akad University, Finland Abo Akad University, Finland University of Turku, Finland .
    Toivola, Diana M.
    Abo Akad University, Finland Turku Centre Disease Modeling, Finland .
    Rosenholm, Jessica M.
    Abo Akad University, Finland .
    Shape engineering vs organic modification of inorganic nanoparticles as a tool for enhancing cellular internalization2012In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 7, no 358Article in journal (Refereed)
    Abstract [en]

    In nanomedicine, physicochemical properties of the nanocarrier affect the nanoparticles pharmacokinetics and biodistribution, which are also decisive for the passive targeting and nonspecific cellular uptake of nanoparticles. Size and surface charge are, consequently, two main determining factors in nanomedicine applications. Another important parameter which has received much less attention is the morphology (shape) of the nanocarrier. In order to investigate the morphology effect on the extent of cellular internalization, two similarly sized but differently shaped rod-like and spherical mesoporous silica nanoparticles were synthesized, characterized and functionalized to yield different surface charges. The uptake in two different cancer cell lines was investigated as a function of particle shape, coating (organic modification), surface charge and dose. According to the presented results, particle morphology is a decisive property regardless of both the different surface charges and doses tested, whereby rod-like particles internalized more efficiently in both cell lines. At lower doses whereby the shape-induced advantage is less dominant, charge-induced effects can, however, be used to fine-tune the cellular uptake as a prospective secondary uptake regulator for tight dose control in nanoparticle-based drug formulations.

  • 9.
    Soomro, Muhammad Yousuf
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Hussain, Ijaz
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Bano, Nargis
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Nanoscale elastic modulus of single horizontal ZnO nanorod using nanoindentation experiment2012In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 7, p. 146-148Article in journal (Refereed)
    Abstract [en]

    We measure the elastic modulus of a single horizontal ZnO nanorod [NR] grown by a low-temperature hydrothermal chemical process on silicon substrates by performing room-temperature, direct load-controlled nanoindentation measurements. The configuration of the experiment for the single ZnO NR was achieved using a focused ion beam/scanning electron microscope dual-beam instrument. The single ZnO NR was positioned horizontally over a hole on a silicon wafer using a nanomanipulator, and both ends were bonded with platinum, defining a three-point bending configuration. The elastic modulus of the ZnO NR, extracted from the unloading curve using the well-known Oliver-Pharr method, resulted in a value of approximately 800 GPa. Also, we discuss the NR creep mechanism observed under indentation. The mechanical behavior reported in this paper will be a useful reference for the design and applications of future nanodevices.

  • 10.
    Strelchuk, V.
    et al.
    National Academic Science Ukraine, Ukraine.
    Kolomys, O.
    National Academic Science Ukraine, Ukraine.
    Rarata, S.
    National Academic Science Ukraine, Ukraine; Kyiv National Taras Shevchenko University, Ukraine.
    Lytvyn, P.
    National Academic Science Ukraine, Ukraine.
    Khyzhun, O.
    NASU, Ukraine.
    Chey, Chan Oeurn
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Raman Submicron Spatial Mapping of Individual Mn-doped ZnO Nanorods2017In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 12, article id 351Article in journal (Refereed)
    Abstract [en]

    ZnO nanorods (NRs) arrays doped with a large concentration of Mn synthesized by aqueous chemical growth and were characterized by SEM, photoluminescence, Raman scattering, magnetic force microscopy (MFM). By comparison of spectra taken on pure and Mn-doped ZnO NRs, a few new Raman impurity-related phonon modes, resulting from the presence of Mn in the investigated samples. We also present a vibrational and magnetic characterization of individual lying nanorods using Raman and MFM imaging. Confocal scanning micro-Raman mapping of the spatial distribution of intensity and frequency of phonon modes in single Mn-doped ZnO NRs nanorods is presented and analyzed for the first time. Mn-related local vibrational modes are also registered in Raman spectra of the single nanorod, confirming the incorporation of Mn into the ZnO host matrix. At higher Mn concentration the structural transformation toward the spinel phase ZnMn2O4 and Mn3O4 is observed mainly in 2D bottom layers. MFM images of Mn-doped ZnO NR arrays and single nanorod were studied in nanoscale at room temperature and demonstrate magnetic behavior. The circular domain magnetic pattern on top of single nanorod originated to superposition of some separate domains inside rod. This demonstrates that long-range ferromagnetic order is present at room temperature. Aligned Mn-doped ZnO NRs demonstrates that long-range ferromagnetic order and may be applied to future spintronic applications.

  • 11.
    Ul Hasan, Kamran
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Sandberg, Mats O
    Acreo AB.
    Nur, Omer
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Polycation stabilization of graphene suspensions2011In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 6, no 493Article in journal (Refereed)
    Abstract [en]

    Graphene is a leading contender for the next-generation electronic devices. We report a method to produce graphene membranes in the solution phase using polymeric imidazolium salts as a transferring medium. Graphene membranes were reduced from graphene oxides by hydrazine in the presence of the polyelectrolyte which is found to be a stable and homogeneous dispersion for the resulting graphene in the aqueous solution. A simple device with gold contacts on both sides was fabricated in order to observe the electronic properties.

  • 12.
    Ul Hasan, Kamran
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Ul Hassan Alvi, Naveed
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Single nanowire-based UV photodetectors for fast switching2011In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 6, no 348Article in journal (Refereed)
    Abstract [en]

    Relatively long (30 mu m) high quality ZnO nanowires (NWs) were grown by the vapor-liquid-solid (VLS) technique. Schottky diodes of single NW were fabricated by putting single ZnO NW across Au and Pt electrodes. A device with ohmic contacts at both the sides was also fabricated for comparison. The current-voltage (I-V) measurements for the Schottky diode show clear rectifying behavior and no reverse breakdown was seen down to -5 V. High current was observed in the forward bias and the device was found to be stable up to 12 V applied bias. The Schottky barrier device shows more sensitivity, lower dark current, and much faster switching under pulsed UV illumination. Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs. The NW was treated with oxygen plasma to improve the switching. The photodetector shows high stability, reversibility, and sensitivity to UV light. The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors.

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