UScholar Works
 
Filters: Journal Title: "Applied Physics Letters" Collection: "ir_uspace" Type: "Text"
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CreatorTitleDescriptionSubjectDate
1 Lupton, John MarkAir-induced fluorescence bursts from single semiconductor nanocrystalsWe observe a dramatic enhancement of the fluorescence intensity from single core/shell CdSe/ZnS nanocrystals upon sudden exposure to air from an evacuated surrounding. Both the number of particles contributing to emission increases as well as the average emission intensity from a single particle, le...CdSe; ZnS; Air-induced; Fluorescence bursts2004
2 Vardeny, Zeev Valentine; Gellermann, WernerAmplified resonant Raman scattering in conducting polymer thin filmsUsing picosecond pulsed laser excitation, we investigate the optical emission characteristics of poly(2,5-dioctyloxy-p-phenylenevinylene), (DOO-PPV), thin films at high excitation intensities (~1-90 MW/cm2). We observe the presence of amplified resonance Raman scattering in the emission spectra of c...Amplified resonant Raman scattering; High excitation intensities; pi-conjugated polymers1998
3 Vardeny, Zeev ValentineAmplified spontaneous emission and lasing in conducting polymers and fluorescent dyes in opals as photonic crystalsSpectral narrowing of photoluminescence (PL) and evolution of sharp emission lines upon optical excitation have been observed in opals made of SiO2 spheres infiltrated with conducting polymers such as OOPPV and MDDOPPV and also fluorescent dyes such as rhodamine 6G, NK-3483, and coumarin 120. Their ...Amplified spontaneous emission; Lasing; Fluorescent dyes1999
4 Scarpulla, MichaelBandgap and band offsets determination of semiconductor heterostructures using three-terminal ballistic carrier spectroscopyAmong the most important properties of semiconductors are their bandgaps and how the total bandgap difference distributes between the conduction band offset ΔEC and the valence band offset ΔEV at the heterojunction (HJ) interface between two semiconductors. Understanding such properties is crucial...Bandgaps; Band offsets; Gallium arsenide2009
5 Lupton, John MarkBragg scattering from periodically microstructured light emitting diodesWe present a simple method of generating a periodic wavelength scale structure in the optically active layer of a light emitting diode. This is achieved by solution deposition of a light emitting polymer on top of a corrugated substrate. The periodic structure allows waveguide modes normally trapped...Bragg scattering; Periodic wavelength scale structure2000
6 Lupton, John MarkBright electroluminescence from a conjugated dendrimerPhotoluminescence and electroluminescence (EL) from a conjugated dendrimer consisting of three distyrylbenzene units linked by a central nitrogen atom as core and meta-linked biphenyl units as dendrons were investigated. The conjugated dendrimer emits green light and shows photoluminescence quantum ...Conjugated dendrimer2002
7 Liu, FengConfining P diffusion in Si by an As-doped barrier layerThe miniaturization of Si-based devices requires control of doping profile, which makes the understanding of dopant interaction and diffusion in Si critical. The authors have studied the effect of As doping on P diffusion in Si using first-principles calculations. The authors found a form of As-vaca...P diffusion; Silicon; Arsenic doping; As-doped barrier; Diffusion control2007
8 Tiwari, AshutoshCopper diffusion characteristics in single-crystal and polycrystalline TaNWe have investigated the diffusivity of copper in single-crystal (NaCl-structured) and polycrystalline TaN thin films grown by pulsed-laser deposition. Polycrystalline TaN films were grown directly on Si(100), while single-crystal films were grown with TiN buffer layers. Both poly- and single-crysta...Diffusion barriers; Copper diffusion; Tantalum nitride2002
9 Tiwari, AshutoshCuBO2: a p-type transparent oxideThe authors report the synthesis of CuBO2, a p-type transparent oxide belonging to Cu-delafossite family. High quality thin films of CuBO2 were deposited on c-plane sapphire substrates by pulsed laser deposition technique. Detailed structural, optical, and electrical characterizations on these films...Transparent conducting oxides; Delafossite series; CuBO22007
10 Vardeny, Zeev ValentineCylindrical micolasers and light emitting devices from conducting polymersSubstantially improved, photopumped polymer lasers are demonstrated using microrings and microdisks of various diameters D ranging from 5 to 200 mm. Various cavity-dependent laser modes were observed, which for D,10 mm were dominated by a single longitudinal mode with linewidth of less than 1 Å. Th...Cylindrical micolasers; OLED; Photopumped polymer lasers; Microrings; Microdisks; Microlasers1998
11 Vardeny, Zeev ValentineDirectional emission from asymmetric microlaser resonators of ∏-conjugated polymersA ∏-conjugated polymer film was fabricated into an asymmetric microlaser resonator having a quadrapole deformation with irregular boundaries and a Q factor of 600. At high excitation intensities above the threshold for lasing, we observed multimode laser emission spectra and directional emission a...Directional emission; Asymmetric microlaser resonators; pi-conjugated polymers; DOO-PPV; poly(dioctyloxy) phenylene vinylene2004
12 Scarpulla, MichaelEffect of film thickness on the incorporation of Mn interstitials in Ga1-xMnxAsWe have investigated the effect of film thickness on the distribution of Mn atoms at various lattice sites in Ga1−xMnxAs thin films. We find that the growth surface acts as a sink facilitating the outdiffusion of Mn interstitials sMnId, and thus reducing its concentration in the film. The outdiffu...Interstitials; Gallium arsenide2005
13 Scarpulla, MichaelEffects of pressure on the band structure of highly mismatched Zn1-yMnyOxTe1-x alloysWe report photomodulation spectroscopy measurements of the pressure dependence of the optical transition in Zn12yMnyOxTe1-x alloys that is associated with the lowest Ѓ conduction band (termed E2 subband). The pressure-induced energy shift of the E2 transition is nonlinear and much weaker as compare...Highly mismatched alloys; Zinc telluride; Anticrossing2004
14 Vardeny, Zeev ValentineEfficiency enhancement of an organic light-emitting diode with a cathode forming two-dimensional periodic hole arrayWe fabricated an organic light-emitting diode using a ∏-conjugated polymer emissive layer sandwiched between two semitransparent electrodes: an optically thin gold film anode, whereas the cathode was in the form of an optically thick aluminum (Al) film with patterned periodic subwavelength two-dim...pi-conjugated polymers; Organic light-emitting diode; OLED2005
15 Lupton, John MarkEnergetic disorder limits energy transfer in semiconductor nanocrystal-DNA-dye conjugatesWe demonstrate the influence of spectral linewidths of individual donor-acceptor couples on energy transfer efficiency in semiconductor nanocrystal-DNA-organic dye conjugates. Temperature-dependent single molecule and ensemble spectroscopy data are analyzed using the Förster theory within the mac...2009
16 Scarpulla, MichaelEnhanced nitrogen incorporation by pulsed laser annealing of GaNxAs1-x formed by N ion implantationWe demonstrate that pulsed laser annealing followed by rapid thermal annealing greatly enhances incorporation of substitutional N in N1-implanted GaAs. Films implanted to 1.8% N exhibit a fundamental band gap of 1.26 eV (a band gap reduction of 160 meV), corresponding to an N activation efficiency ...Highly mismatched alloys; Gallium arsenide2002
17 Tiwari, AshutoshEpitaxial growth and properties of Zn1-xVxO diluted magnetic semiconductor thin filmsHere we report systematic studies on the epitaxial growth and properties of Zn1−xVxO[x=0.001-0.2] thin films deposited onto sapphire c-plane single crystals. The thin films were deposited using pulsed laser deposition technique and were found to be epitaxial in nature. X-ray diffraction and high ...ZnO; Vanadium2005
18 Vardeny, Zeev Valentine; Raikh, Mikhail E.Evidence for braggoriton excitations in opal photonic crystals infiltrated with highly polarizable dyesWe studied angle-dependent reflectivity spectra of opal photonic crystals infiltrated with cyanine dye aggregates, which are highly polarizable media with very large Rabi frequency. We show that, at resonance condition between the exciton-polariton of the dye aggregate and the Bragg gap, the Bragg s...Braggoriton excitations; Opal photonic crystals; Cyanine dye aggregates; Bragg; Photonic band-gap; PBG; Polarizable dyes2002
19 Liu, FengFabricating artificial nanowells with tunable size and shape by using scanning tunneling microscopyThe authors report a method of precisely fabricating the large-scale nanocrystals with well-defined shape and size. The (111) oriented Pb islands deposited on Si(111)-7x7 substrate were investigated with a manipulation technique based on scanning tunneling microscopy. By applying a series of voltage...Artificial nanowells2006
20 Vardeny, Zeev ValentineFemtosecond dynamics of the nonlinear optical response in polydiethynylsilaneWe have measured the femtosecond dynamics of the nonlinear optical response xc3' in polydiethynylsilane ( C4H2SiBu2)x, a novel class of r-conjugated polymers incorporating Si, using degenerate four-wave mixing and photoinduced absorption techniques. In resonance conditions at 620 nm we found x (3) ...Polydiethynylsilane; Femtosecond dynamics; Nonlinear optical response; Pi-conjugated polymers1991
21 Scarpulla, MichaelFerromagnetic Ga1-xMnxAs produced by ion implantation and pulsed-laser meltingWe demonstrate the formation of ferromagnetic Ga1-xMnxAs films by Mn ion implantation into GaAs followed by pulsed-laser melting. Irradiation with a single excimer laser pulse results in the epitaxial regrowth of the implanted layer with Mn substitutional fraction up to 80% and effective Curie tempe...Gallium arsenide; Ferromagnetic semiconductors; Remanent magnetization2003
22 Tiwari, AshutoshFerromagnetism in Co doped CeO2: observation of giant magnetic moment with a high Curie temperatureWe report room temperature ferromagnetism in single crystal Ce1−xCoxO2−δ (x≤0.05) films deposited on a LaAlO3(001) substrate. Films were grown by a pulsed laser deposition technique and were thoroughly characterized using x-ray diffraction, high-resolution transmission electron microscopy cou...CeO2; Cobalt2006
23 Tiwari, AshutoshFerromagnetism in Cu-doped ZnO films: role of charge carriersWe report the observation of room temperature ferromagnetism in Cu-doped (5%) ZnO films grown on c-plane sapphire substrates. Films were prepared by pulsed laser deposition technique and were thoroughly characterized using several state-of-the-art characterization techniques. Hall measurements sho...Charge carriers2008
24 Symko, Orest GeorgeFormation of AlCuFe quasicrystalline thin films by solid state diffusionWe show that thin films 3000 A in thickness of the icosahedral AlCuFe phase can be formed by solid state diffusion of sputtered Al, Cu, and Fe layers. As for bulk materials, we propose that the icosahedral phase grows by diffusion of the 0.1 in the A13Fe layer previously formed by interdiffusion of...AlCuFe; Quasicrystalline thin films; Solid state diffusion; Icosahedral phase1994
25 Lupton, John MarkFrequency up-conversion as a temperature probe of organic opto-electronic devicesFrequency up-conversion is demonstrated in a polyfluorene-based conjugated polymer. Up-converted emission is observed upon excitation to the red of the 0-0 luminescence band. The emission intensity depends strongly on temperature and provides an accurate probe of the operating temperature of organic...Frequency up-conversion; Organic opto-electronic devices2002
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