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  • 1.
    Anand, Srinivasan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Desieres, Y.
    KTH, School of Engineering Sciences (SCI), Applied Physics. CEA LETI MINATEC, Grenoble, France.
    Visser, D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Chen, D-Y
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Optical Coatings and Films Based on Photonic Semiconductor Nanostructure Assemblies2017In: 2017 19TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Photonic semiconductor nanostructure assemblies offer unique possibilities for light manipulation as well as for tailoring light-matter interaction by appropriate choice of their geometrical and material properties. The material-structure combination offers a variety of options for wavelength specific applications, deriving from the electronic properties of semiconductors and optical properties of individual and assemblies of nanostructures (particles, disks, pillars/wires etc.). We present an overview of our research on optical coatings based on semiconductor nanostructure assemblies focusing on their optical properties, different fabrication technologies and selected application examples. Design and simulations of the optical coatings are performed by finite difference time domain calculations, and are used as a guideline for fabrication. We discuss different routes for fabrication of nanostructured optical films/coatings including directed assembly and patterning of nanoparticles from solution phase, solution synthesis, combination of dry etching and colloidal lithography, transfer printing, and generation of flexible polymer films with embedded nanostructures. The fabricated films are validated by optical measurements and some device specific properties such as omni-directional broad-band anti-reflection in solar cells and efficient light extraction in light emitting diodes are demonstrated.

  • 2.
    Chen, Shula
    et al.
    Linkoping Univ, Dept Phys Chem & Biol, SE-58183 Linkoping, Sweden..
    Huang, Yuqing
    Linkoping Univ, Dept Phys Chem & Biol, SE-58183 Linkoping, Sweden..
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Buyanova, Irina A.
    Linkoping Univ, Dept Phys Chem & Biol, SE-58183 Linkoping, Sweden..
    Chen, Weimin M.
    Linkoping Univ, Dept Phys Chem & Biol, SE-58183 Linkoping, Sweden..
    Room-temperature polarized spin-photon interface based on a semiconductor nanodisk-in-nanopillar structure driven by few defects2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 3575Article in journal (Refereed)
    Abstract [en]

    Owing to their superior optical properties, semiconductor nanopillars/nanowires in one-dimensional (1D) geometry are building blocks for nano-photonics. They also hold potential for efficient polarized spin-light conversion in future spin nano-photonics. Unfortunately, spin generation in 1D systems so far remains inefficient at room temperature. Here we propose an approach that can significantly enhance the radiative efficiency of the electrons with the desired spin while suppressing that with the unwanted spin, which simultaneously ensures strong spin and light polarization. We demonstrate high optical polarization of 20%, inferring high electron spin polarization up to 60% at room temperature in a 1D system based on a GaNAs nanodisk-in-GaAs nanopillar structure, facilitated by spin-dependent recombination via merely 2-3 defects in each nanodisk. Our approach points to a promising direction for realization of an interface for efficient spin-photon quantum information transfer at room temperature-a key element for future spin-photonic applications.

  • 3.
    Desieres, Yohan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Chen, Ding Yuan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Schippers, Casper
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Strong light extraction enhancement using TiO2 nanoparticles-based microcone arrays embossed on III-Nitride light emitting diodes2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 23, article id 231101Article in journal (Refereed)
    Abstract [en]

    Colloidal TiO2 nanoparticles were used for embossing of composite microcone arrays on III-Nitride vertical-thin-film blue light emitting diodes (LEDs) as well as on silicon, glass, gallium arsenide, and gallium nitride surfaces. Ray tracing simulations were performed to optimize the design of microcones for light extraction and to explain the experimental results. An optical power enhancement of similar to 2.08 was measured on III-Nitride blue LEDs embossed with a hexagonal array of TiO2 microcones of similar to 1.35 mu m in height and similar to 2.6 mu m in base width, without epoxy encapsulation. A voltage increase in similar to 70mV at an operating current density of similar to 35 A/cm(2) was measured for the embossed LEDs. The TiO2 microcone arrays were embossed on functioning LEDs, using low pressures (similar to 100 g/cm(2)) and temperatures <= 100 degrees C. 

  • 4.
    Désières, Yohan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Chen, D. Y.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Schippers, C. S.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Vaufrey, D.
    Demars, P.
    Levy, F.
    Largeron, C.
    Lalauze, Q.
    Anand, S.
    Nanoparticle-based microstructures for light extraction enhancement in nitride-based LEDs2018In: Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XXII, SPIE - International Society for Optical Engineering, 2018, article id 105540QConference paper (Refereed)
    Abstract [en]

    TiO2 nanoparticles dispersion was used to fabricate three dimensional (3D) composite structures on the surface of various substrate materials as well as on the surface of nitride light emitting diodes (LEDs). Optical power enhancements in the range of ∼1.4-2.1 were measured.

  • 5. Prajapati, C. S.
    et al.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Semiconductor Materials, HMA.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bhat, N.
    Honeycomb type ZnO nanostructures for sensitive and selective CO detection2017In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 252, p. 764-772Article in journal (Refereed)
    Abstract [en]

    Excellent sensing performance for CO gas is demonstrated using inexpensive sensor devices based on honeycomb type ZnO nanostructures, fabricated by colloidal lithography and lift-off process. This newly proposed method for gas sensors is cost effective and provides significant enhancement of both sensitivity and selectivity of CO detection. Honeycomb type ZnO nano films developed in ∼21 nm ZnO layer consisting of 1 μm period hexagonal lattice of air-holes with diameter varying from ∼600–900 nm are investigated for CO sensing. These structures are fabricated by a combination of self-assembly of polystyrene (PS) spheres, their size reduction by oxygen plasma and magnetron-sputtering of ZnO followed by PS mask removal. The hole diameter and hence the width of ZnO honeycomb walls are determined by size reduction of PS spheres. Fabricated ZnO honeycomb type sensors show superior sensing performance compared to planar ZnO films, and response as high as ∼81.2% at 300 °C for a 3 ppm CO with a detection resolution of 500 ppb and response and recovery times of ∼180 and ∼210 s, respectively, were obtained. The repeatability of the observed results is confirmed and in addition, the CO selectivity is shown for gas mixtures consisting of CH4, H2S, CO2, NO2, SO2 and H2. The developed nanostructuring method is generic and can be adapted for improving performance of other metal-oxide based gas sensors.

  • 6.
    Visser, Dennis
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Dev Choudhury, Bikash
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Krasovska, Inese
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Refractive index sensing in the visible/NIR spectrum using silicon nanopillar arrays2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 11, p. 12171-12181Article in journal (Refereed)
    Abstract [en]

    Si nanopillar (NP) arrays are investigated as refractive index sensors in the visible/NIR wavelength range, suitable for Si photodetector responsivity. The NP arrays are fabricated by nanoimprint lithography and dry etching, and coated with thin dielectric layers. The reflectivity peaks obtained by finite-difference time-domain (FDTD) simulations show a linear shift with coating layer thickness. At 730 nm wavelength, sensitivities of ∼0.3 and ∼0.9 nm/nm of SiO2 and Si3N4, respectively, are obtained; and the optical thicknesses of the deposited surface coatings are determined by comparing the experimental and simulated data. The results show that NP arrays can be used for sensing surface bio-layers. The proposed method could be useful to determine the optical thickness of surface coatings, conformal and non-conformal, in NP-based optical devices.

  • 7.
    Visser, Dennis
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Ye, Z.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Prajapati, C. S.
    Bhat, N.
    Anand, S.
    Investigations of sol-gel ZnO films nanostructured by reactive ion beam etching for broadband anti-reflection2017In: ECS Journal of Solid State Science and Technology, ISSN 2162-8769, E-ISSN 2162-8777, Vol. 6, no 9, p. P653-P659Article in journal (Refereed)
    Abstract [en]

    A novel ZnO dry etching approach is introduced using reactive ion beam etching of thick sol-gel ZnO layers for controlled nanodisk/nanocone array fabrication. In this approach the same system can be used for the colloidal lithography mask (silica particles) size reduction by a fluorine-based chemistry and etching of the ZnO nanostructures by a CH4/H2/Ar chemistry. This resulted in a ZnO:SiO2 etch selectivity of ~3.4 and etch rate of ~56 nm/min. Thick sol-gel ZnO layers, nanodisk arrays and (truncated) nanocone arrays were fabricated and their optical properties analyzed by finite-difference time-domain simulations and spectrally-resolved total/specular reflectivity measurements. The demonstrated broadband omnidirectional anti-reflection, controlled nanostructure period/geometry and low absorption in the visible-NIR spectrum makes these sol-gel ZnO nanostructures very interesting for many optoelectronic applications, including photovoltaics.

1 - 7 of 7
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