UScholar Works
 
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601 - 625 of 924
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CreatorTitleDescriptionSubjectDate
601 Vardeny, Zeev ValentinePhotoresponse and electroresponse of polymers light emitting diodesWe have studied the photoresponse and electroresponse of light emitting diodes (LEDs ) made from a variety of soluble conducting polymers sandwiched between indium tin oxide (ITO) and metals including calcium, aluminum and copper. Under illumination all freshly prepared LEDs exhibit relatively large...Photoresponse; Electroresponse; Photovoltage; I-V curves1995
602 Gondolo, PaoloPhysics of the very early universe: what can we learn from cosmological observations?Cosmological observations are starting to probe the evolution of the Universe before nucleosynthesis. The observed fluctuations in the cosmic microwave background and in the distribution of matter can be traced back to their origin during inflation, and the inflaton potential has begun to be unrave...Neutralinos; Inflatons; Moduli fields2006
603 Vardeny, Zeev ValentinePicosecond dynamics of carriers in amorphous semiconductorsUsing time resolved photoinduced absorption with subpicosecond resolution we studied hot carrier thermalization followed by deep trapping and recombination in a-Si, a-Si:H, a-Si:F, a-Si:H:F and a-As2Se3. In a-Se and a-As2S3_xSex (0.25 < x < 0.75) the observed relaxations were attributed to geminat...Excess carriers; Thermalization1981-10
604 Vardeny, Zeev ValentinePicosecond dynamics of photoexcitations in amorphous multilayer structuresWe report on measurements of ultrafast relaxation processes in transmission and reflection in amorphous multilayer structures consisting of a-Si:H, a-SiNx:H, a-SiOx:H, and a-Ge:H. The decays recorded in transmission in the a-Si:H/a-SiNx :H and a-Si:H/a-SiOx :H multilayers depend strongly on the sili...Photoexcitations1986
605 Vardeny, Zeev ValentinePicosecond optical generation and detection of phonon waves in a-As2Te3Using the pump and probe technique we have observed oscillations of photoinduced transmission in thin films of a-As2Te3. The oscillations have periods of 70-240 ps, depending on sample thickness. We ascribe these to phonon propagation in the films. Thermal expansion and carrier deformation potenti...Picosecond optical generation; a-As2Te3; Pump and probe technique1984
606 Vardeny, Zeev ValentinePicosecond optical time-of-flight studies of carrier transport in α-Si:H/α-SiNx:H multilayersWe report time-of-flight experiments in the time range from 0.2 psec to 1.8 nsec in 0-Si:H-a-SiNx:H multilayer structures using a purely optical technique. The transport mechanism of photoexcited carriers is shown to be dispersive and its characteristic parameters are determined in the temperature r...Time-of-flight; Amorphous silicon; Carrier transport; Photoexcited carriers1987-09
607 Vardeny, Zeev ValentinePicosecond photoinduced dichroism in trans-(CH)x: direct measurement of soliton diffusionPhotoinduced dichroism caused by bleaching of the interband transition in tran s-(CH)x was observed in the picosecond time domain,, The bleaching is induced instantaneously and decays with time as £~1 / / 2 , changing to a lower power after ~50 psec. Although the photoinduced bleaching persists to...Photoinduced dichroism; Trans-(CH)x1982-11
608 Vardeny, Zeev ValentinePicosecond photoinduced optical anisotropy in trans-(CH)x : direct measurement of soliton diffusionPhotoinduced dichroism caused by bleaching of the interband transition in trans - (CH)X was observed in the picosecond time domain. The bleaching is induced instantaneously and decays with time as t - 1 / 2 , changing to a lower power after ~ 50 ps. Although the photoinduced bleaching persists to l...Trans-(CH)x; Soliton diffusion; Bleaching; Photoinduced dichroism1983-06
609 Vardeny, Zeev ValentinePicosecond photoinduced transmission associated with deep traps in phosphorous doped α-Si:HPhotoinduced transmission was observed in the picosecond time domain in phosphorusdoped a-Si:H and connected with deep hole traps produced by doping. The hole transport was found to be dispersive starting before 5 ps and temperature dependent. This shows that the energy distribution of shallow traps...Photoinduced transmission; Deep traps; Amorphous silicon; Phosphorous doped a-Si:H; Electronic relaxation response1982-04
610 Vardeny, Zeev ValentinePicosecond photomodulation spectroscopy in amorphous semiconductorsPicosecond trapping of photogenerated carriers in gap states of doped, compensated and undoped amorphous hydrogenated silicon (a-Si:H) and of a-Si:H based superlattices was studied by the pump and probe photomodulation technique. In undoped a-Si:H the photogenerated carries are trapped in band-tail ...Picosecond spectroscopy1987
611 Vardeny, Zeev ValentinePicosecond photomodulation study of nanocrystalline hydrogenated siliconWe have extended our photomodulation studies of nc-Si:H to the picosecond time domain. We measured the decays of photoinduced reflectivity with lOOfs temporal resolution as a function of. light intensity. Comparison with the data obtained on a-Si:H and c-Si indicates that ultrafast trapping and reco...Picosecond photomodulation; Nanocrystalline silicon1990
612 Lupton, John MarkPicosecond time-resolved photoluminescence spectroscopy of a tetracene film on highly oriented pyrolytic graphite: dynamical relaxation, trap emission and superradianceA detailed time resolved investigation of the photoluminescence of a thin tetracene film deposited on highly oriented pyrolytic graphite is presented. In agreement with Lim et al. [Phys. Rev. Lett. 92, 107402 (2004)], we find strong evidence for superradiance: an increase of the relative intensity...Tetracene film; Pyrolytic graphite Photoluminescence spectroscopy; pi-conjugated polymers; Dynamical relaxation; Trap emission; Superradiance2007
613 Vardeny, Zeev ValentinePicosecond trapping of photocarriers in amorphous siliconTrapping of photoexcited carriers in the picosecond and subnanosecond time domains was studied by measuring the decay of photoinduced absorption (PA) in a-Si, a-Si:F, a-Si:H, and a-Si:H:F. We found that when the midgap density of states decreases, both the trapping time and its temperature dependenc...Photocarriers; Amorphous silicon; Picosecond trapping; Photoinduced absorption1983
614 Mishchenko, Eugene; Raikh, Mikhail E.Planar array of semiconducting nanotubes in an external electric field: collective screening and polarizabilityWe study theoretically the charge separation in a planar array of semiconducting nanotubes (NTs) of length, 2h, placed in an external electric field, F, parallel to their axes. By employing the conformal mapping, we find analytically the exact distribution of the induced charge density for the arb...Planar array2006-12
615 Mishchenko, EugenePlasmon attenuation and optical conductivity of a two-dimensional electron gasIn a ballistic two-dimensional electron gas, the Landau damping does not lead to plasmon attenuation in a broad interval of wave vectors q≤kF . Similarly, it does not contribute to the optical conductivity σ(ω,q) in a wide domain of its arguments, EF>ω>qvF , where EF , kF , and vF are, respec...Optical conductivity; Plasmon-phonon conversion; Landau damping2004-05
616 Vardeny, Zeev ValentinePlastic microring lasers on fibers and wiresPhotopumped, pulsed, narrow line laser emission is demonstrated using cylindrical microcavities formed by p-conjugated polymer thin films wrapped around thin glass optical fibers and metal wires with various diameters D. A variety of cavity-dependent resonant laser mode structures were observed, whi...Microring lasers; pi-conjugated polymers; pi-conjugated polymer thin films; Microcavities1998
617 Vardeny, Zeev ValentinePolarization memory decay spectroscopy of photoexcitations in ∏-conjugated polymers: evidence for excimersWe used the technique of ultrafast transient polarized photomodulation in the visible/near-infrared range and polarization memory decay (PMD) spectroscopy to study the primary photoexcitations in films and solutions of two poly(phenylene-vinylene) (PPV) derivatives, namely, 2-methoxy-5-(2'-ethylhex...Photoexcitations; pi-conjugated polymers; Polarization memory decay spectroscopy; PMD; DOO-PPV; MEH-PPV; Ultrafast transient polarized photomodulation; Intrachain singlet excitons; Excimers; Interchain charge transfer exciton2008-05
618 Mishchenko, EugenePolarized electric current in semiclassical transport with spin-orbit interactionSemiclassical solutions of two-dimensional Schrödinger equation with spin-orbit interaction and smooth potential are considered. In the leading order, spin polarization is in-plane and follows the evolution of the electron momentum for a given subband. Out-of-plane spin polarization appears as a ...Spin-polarized current; Sharvin conductance; Spin-orbit coupling2006-10
619 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Polaron spin-lattice relaxation time in ∏-conjugated polymers from optically detected magnetic resonanceWe describe a method for obtaining the polaron spin-lattice relaxation time TSL in ∏-conjugated polymers by measuring the optically detected magnetic resonance (ODMR) dynamics as a function of microwave power and laser intensity. The peculiar ODMR dynamics is well described by a spin dependent re...pi-conjugated polymers; Optically detected magnetic resonance; ODMR; MEH-PPV2007-10
620 DeTar, CarletonPotts flux tube model at nonzero chemical potentialWe model the deconfinement phase transition in quantum chromodynamics at nonzero baryon number density and large quark mass by extending the flux tube model ~three-state, three-dimensional Potts model! to nonzero chemical potential. In a direct numerical simulation we confirm mean-field-theory pre...Phase transitions; Quark-gluon plasma; Chemical potential; Potts model2000-03
621 Bromley, Benjamin C.Predicted space motions for hypervelocity and runaway stars: proper motions and radial velocities for the GAIA EraWe predict the distinctive three dimensional space motions of hypervelocity stars (HVSs) and runaway stars moving in a realistic Galactic potential. For nearby stars with distances less than 10 kpc, unbound stars are rare; proper motions alone rarely isolate bound HVSs and runaways from indigenous h...2014-01-01
622 Mattis, Daniel C.PrefaceIt was the early 1960s. Elliott H. Lieb and the present author were colleagues at the IBM Research Laboratories in Yorktown Heights, occupying neighboring cubicles. We collaborated in the study, creation and solution of mathematical models of many-body phenomena. In the course of this work we ultima...2012-01-01
623 DeTar, CarletonPreliminary heavy-light decay constants from the MILC collaborationPreliminary results from the MILC collaboration for fβ, / fβs, /fD, /fD„ and their ratios are presented. We compute in the quenched approximation at β = 6.3, 6.0 and 5.7 with Wilson light quarks and static and Wilson heavy quarks. We attempt to quantify all systematic errors other than quenchin...Decay constants; Wilson quarks1995-04
624 Lupton, John MarkProbing the electrode-polymer interface in conjugated polymer devices with surface-enhanced Raman scatteringA crucial consideration in organic devices is the role of the interface between a metal electrode and the active polymer material. Here, we use the conjugated polymer poly[2-methoxy-5-(2-ethylhexyl-oxy)-1,4-phenylene-vinylene] (MEH-PPV) with model gold and silver electrodes to perform surface-enhanc...2012-01-01
625 Gondolo, PaoloPrompt atmospheric neutrinos and muons: dependence on the gluon distribution functionWe compute the next-to-leading order QCD predictions for the vertical flux of atmospheric muons and neutrinos from decays of charmed particles, for different PDF's (MRS-R1, MRS-R2, CTEQ-4M and MRST) and different extrapolations of these at a small partonic momentum fraction x. We find that the predi...Neutrino telescopes; Charm; Atmospheric flux; Prompt flux2000-02
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