UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
1 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
2 Vardeny, Zeev ValentineElectroabsorption spectroscopy of single walled nanotubesWe have measured the electric field modulated absorption of a sample of single-walled nanotubes (SWNT) suspended in a solid polyvinyl alcohol matrix. The electroabsorption (EA) spectrum roughly follows the first derivative of the absorption with respect to photon energy, scales quadratically with t...Electroabsorption spectroscopy; Single-walled nanotubes; SWNT2005
3 Vardeny, Zeev ValentineInfrared ultrafast optical probes of photoexcitations in ∏-conjugated organic semiconductorsWe measured the ultrafast dynamics of photoexcitations in a variety of semiconductor ∏-conjugated polymer films and solutions, in the spectral range from 0.13 eV to 1.05 eV and time domain from 100 fs to 800 ps. The measurements were made in the low signal regime, where the relative changes in tra...Infrared ultrafast optical probes; Photoexcitations; Ultrafast dynamics; MEH-PPV2005
4 Vardeny, Zeev ValentineLinear and nonlinear optical spectroscopies of PPV/PPE copolymer semiconductorsWe used a variety of picosecond transient and cw spectroscopies to investigate the linear and nonlinear optical properties of films of PPE/PPV copolymer semiconductor. The spectroscopies used include absorption, electroabsorption (EA) and two-photon-absorption (TPA). In addition to the odd parity e...Linear optical spectroscopy; Nonlinear optical spectroscopy; PPV/PPE copolymer; pi-conjugated polymers2005
5 Vardeny, Zeev Valentine; Efros, Alexei L.Optical studies of 2D and 3D metallo-dielectric photonic crystalsWe have fabricated and studied two-dimensional (2D) and three-dimensional (3D) metallo-dielectric photonic crystals (MDPC) in the visible/near ir spectral range using a variety of optical techniques. The 2D MDPC showed anomalous transmission due to surface plasmon polaritons in resonance with the ph...Metallo-dielectric photonic crystals; Organic light emitting diodes; Anomalous transmission; surface plasmon polaritons; Opal photonic crystals; Metal infiltrated opals; Optical reflectivity; Transmission spectra2005
6 Vardeny, Zeev ValentineOptical studies of spin coherence in organic semiconductorsSpin coherence in organic oligomer and polymer semiconductors is a crucial property in determining the performance of organic spin devices. Using the techniques of photo-induced absorption (PA) detected magnetic resonance (PADMR) and photoluminescence (PL) detected magnetic resonance (PLDMR), we ha...Spin coherence; Organic spin devices2005
7 Vardeny, Zeev ValentineOrganic spin-valves: physics and applicationsSpin-valve devices of organic semiconductors in the vertical configuration using a variety of exotic and regular ferromagnetic electrodes were fabricated and studied as a function of applied magnetic field, temperature and applied bias voltage. These devices show that spin polarized carriers can be ...Organic spin-valves; Spin-polarized transport; Spin-polarized carrier injection; Spin polarization2005
8 Bromley, Benjamin C.Periodic standing-wave approximation: nonlinear scalar fields, adapted corrdinates, and the eigenspectral methodThe periodic standing wave (PSW) method for the binary inspiral of black holes and neutron stars computes exact numerical solutions for periodic standing-wave spacetimes and then extracts approximate solutions of the physical problem, with outgoing waves. The method requires solution of a boundary-...Periodic standing wave method; Black holes; Neutron stars2005
9 Boehme, Christoph; Friedrich, FrancesPulsed EDMR study of charge trapping at Pb centersLow temperature pulsed electrically detected magnetic resonance (pEDMR) measurements of charge trapping and recombination transitions involving Pb centers at the c-Si (111) /Si02 interface are presented. The results of these experiments show that when a conduction electron is trapped, it forms a str...Charge trapping; Lande factor2005
10 Williams, Clayton C.Single-electron manipulation to and from a SiO2 surface by electrostatic force microscopyOccupation of individual electron states near the surface of a SiO2 film is controlled by reversible single-electron tunneling to or from a metallic electrostatic force microscope probe. By switching the polarity of an applied dc bias between the probe and the sample to adjust the Fermi energy of ...2005
11 Vardeny, Zeev ValentineSpin and magnetic field effects in organic semiconductor devicesThe authors describe three spin and magnetic field effects in organic semiconductor devices: First, injection, transport and detection of spin-polarised carriers using an organic semiconductor as the spacer layer in a spin-valve structure, yielding low-temperature giant magnetoresistance effects as...Spin effects; Magnetic field effects; MR; OLED; Organic light-emitting diode; Spin-polarised carriers; Spin-dependent exciton formation; Electroluminescent efficiency; pi-conjugated organic semicondutors; OSEC2005
12 Vardeny, Zeev ValentineTransport studies of isolated molecular wires in self-assembled monolayer devicesWe have fabricated a variety of isolated molecule diodes based on self-assembled monolayers (SAM) of solid-state mixture (SSM) of molecular wires [1,4-methane benzene dithiol (Me-BDT)], and molecular insulator spacers [penthane 1-thiol (PT)] with different concentration ratios r of wires/spacers, wh...Transport studies; Molecular wires; Monolayer devices2005
13 Boehme, ChristophTriplet recombination at Pb centers and its implications for capture cross sectionsPulsed electrically detected magnetic resonance measurements are presented showing that Pb centers at the crystalline silicon (c-Sid) (111) to silicon dioxide sSiO2d interface can cause recombination of strongly coupled spin pairs in singlet and triplet configurations. The implication of these find...Silicon interfaces2005
14 Vardeny, Zeev ValentineUltrafast spectroscopy of excitons in semiconducting carbon nanotubesUltrafast relaxation dynamics of photoexcitations in semiconducting single walled carbon nanotubes (S-NTs) were investigated using polarized pump-probe photomodulation (with 150 fs time resolution) and cw polarized photoluminescence (PL). Both annealed and unannealed NT films and D 2 0 solutions of ...Non-linear optical methods; Carbon nanotubes; ultrafast dynamics2005
15 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Apparent phonon side-band modes in π-conjugated systems: polymers, oligomers and crystalsThe emission spectra of many π-conjugated polymers and oligomers contain side-band replicas with apparent frequencies that do not match the Raman active mode frequencies. Using a time dependent model we show that in such many mode systems, the increased damping of the time dependent transition dipo...2005-11
16 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Apparent vibrational side bands in rr-conjugated systems: the case of distyrylbenzeneThe photoluminescence sPLd spectra of dilute solution and single crystals of distyrylbenzene show unique temperature-dependent vibronic structures. The characteristic single frequency progression at high temperatures is modulated by a low-frequency progression series at low temperatures. None of th...pi-conjugated systems; Distyrylbenzene; Vibrational side-bands; Vibronic structures; DSB2005-02
17 Mishchenko, EugeneBreached superfluidity via p-wave couplingAnisotropic pairing between fermion species with different Fermi momenta opens two-dimensional areas of gapless excitations, thus producing a spatially homogeneous state with coexisting superfluid and normal fluids. This breached pairing state is stable and robust for arbitrarily small mismatch and ...Spin-orbit coupling; Gapless excitations; Cooper instability2005-03
18 DeTar, CarletonCharmed-meson decay constants in three-flavor lattice QCDWe present the first lattice QCD calculation with realistic sea quark content of the D+-meson decay constant fD+. We use the MILC Collaboration's publicly available ensembles of lattice gauge fields, which have a quark sea with two flavors (up and down) much lighter than a third (strange). We obtain...Flavor physics; Charmed meson; Staggered fermions2005-09
19 Gondolo, PaoloCompatibility of DAMA dark matter detection with other searchesWe present two examples of velocity distributions for light dark matter particles that reconcile the annual modulation signal observed by DAMA with all other negative results from dark matter searches. They are: (1) a conventional Maxwellian distribution for particle masses around 5 to 9 GeV; (2) ...DAMA; CDMS; Neutralinos; WIMP; Weakly interacting massive particles; Halo models; Dark matter stream2005-06
20 Gondolo, PaoloDetectability of weakly interacting massive particles in the Sagittarius dwarf tidal streamTidal streams of the Sagittarius dwarf spheroidal galaxy (Sgr) may be showering dark matter onto the solar system and contributing ~(0:3-23)% of the local density of our galactic halo. If the Sagittarius galaxy contains dark matter in the form of weakly interacting massive particles (WIMPs), the ext...WIMP; Weakly interacting massive particles; Sagittarius dwarf galaxy; Recoil energy; Sgr stream2005-02
21 Vardeny, Zeev ValentineExciton dynamics in single-walled nanotubes: transient photoinduced dichroism and polarized emissionUltrafast relaxation of photoexcitations in semiconducting single-walled carbon nanotubes (S-NTs) were investigated using polarized pump-probe photomodulation (with 150 fs time resolution) and cw polarized photoluminescence (PL). Both annealed and unannealed thin NT films and D2O solutions of isola...Exciton dynamics; Single-walled carbon nanotubes; SWNT; Transient photoinduced dichroism; Polarized emission; Ultrafast relaxation; Photoexcitations2005-03
22 Wu, Yong-ShiGround states and thermal states of the random field Ising modelThe random field Ising model is studied numerically at both zero and positive temperature. Ground states are mapped out in a region of random field and external field strength. Thermal states and thermodynamic properties are obtained for all temperatures using the Wang-Landau algorithm. The specific...Ground states; Thermal states2005-09
23 DeTar, CarletonHeavy-light decay constants using clover valence quarks and three flavors of dynamical improved staggered quarksStarting in 2001, the MILC Collaboration began a large scale calculation of heavy-light meson decay constants using clover valence quarks on ensembles of three flavor configurations. For the coarse configurations, with a = 0.12 fm, eight combinations of dynamical light and strange quarks have been ...Decay constants; Clover valence quarks; Staggered quarks2005-03
24 Rogachev, AndreyInfluence of high magnetic fields on the superconducting transition of one-dimensional Nb and MoGe nanowiresThe effects of a strong magnetic field on superconducting Nb and MoGe nanowires with diameter ~10 nm have been studied. We have found that the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory of thermally activated phase slips is applicable in a wide range of magnetic fields and describes well the ...Nb; MoGe; Superconducting transition; Langer-Ambegaokar-McCumber-Halperin; LAMH; Phase slips2005-01
25 DeTar, CarletonLeptonic decay constants fDs and fD in three flavor lattice QCDWe determine the leptonic decay constants fDs and fD in three flavor unquenched lattice QCD. We use O(a2)-improved staggered light quarks and O(a)-improved charm quarks in the Fermilab heavy quark formalism. Our preliminary results, based upon an analysis at a single lattice spacing, are fDs = 263+5...Decay constants2005-03
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