392 research outputs found
Temperature dependent photoluminescence of single CdS nanowires
Temperature dependent photoluminescence (PL) is used to study the electronic
properties of single CdS nanowires. At low temperatures, both near-band edge
(NBE) photoluminescence (PL) and spatially-localized defect-related PL are
observed in many nanowires. The intensity of the defect states is a sensitive
tool to judge the character and structural uniformity of nanowires. As the
temperature is raised, the defect states rapidly quench at varying rates
leaving the NBE PL which dominates up to room temperature. All PL lines from
nanowires follow closely the temperature-dependent band edge, similar to that
observed in bulk CdS.Comment: 11 pages, 4 figure
Low temperature photoluminescence imaging and time-resolved spectroscopy of single CdS nanowires
Time-resolved photoluminescence (PL) and micro-PL imaging were used to study
single CdS nanowires at 10 K. The low-temperature PL of all CdS nanowires
exhibit spectral features near energies associated with free and bound exciton
transitions, with the transition energies and emission intensities varying
along the length of the nanowire. In addition, several nanowires show spatially
localized PL at lower energies which are associated with morphological
irregularities in the nanowires. Time-resolved PL measurements indicate that
exciton recombination in all CdS nanowires is dominated by non-radiative
recombination at the surface of the nanowires.Comment: 9 pages, 3 figures, to be published in Applied Physics Letter
STM Images and Chemisorption Bond Parameters of Acetylene, Ethynyl, and Dicarbon Chemisorbed on Copper â€
Langevin-like giant magnetoresistance in Co-Cu superlattices
We present evidence for a new type of giant magnetoresistance in (111) cobalt-copper superlattices with atomically smooth interfaces. We propose that the lowered dimensionality of the structure leads to an enhancement of the scattering of conduction electrons from paramagnetic interfaces obeying a Langevin-like saturation at very high fields, well beyond the switching field of the Co layers. The findings help to explain similarities in magnetotransport behavior with recently reported granular systems as well as differences with antiferromagnetically coupled multilayers
Low temperature properties of a quantum particle coupled to dissipative environments
We study the dynamics of a quantum particle coupled to dissipative (ohmic)
environments, such as an electron liquid. For some choices of couplings, the
properties of the particle can be described in terms of an effective mass. A
particular case is the three dimensional dirty electron liquid. In other
environments, like the one described by the Caldeira-Leggett model, the
effective mass diverges at low temperatures, and quantum effects are strongly
suppressed. For interactions within this class, arbitrarily weak potentials
lead to localized solutions. Particles bound to external potentials, or moving
in closed orbits, can show a first order transition, between strongly and
weakly localized regimes.Comment: 10 page
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