15,845 research outputs found
Radiation damage and defect behavior in ion-implanted, lithium counterdoped silicon solar cells
Boron doped silicon n+p solar cells were counterdoped with lithium by ion implanation and the resultant n+p cells irradiated by 1 MeV electrons. The function of fluence and a Deep Level Transient Spectroscopy (DLTS) was studied to correlate defect behavior with cell performance. It was found that the lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. It is concluded that the annealing behavior is controlled by dissociation and recombination of defects. The DLTS studies show that counterdoping with lithium eliminates at least three deep level defects and results in three new defects. It is speculated that the increased radiation resistance of the counterdoped cells is due primarily to the interaction of lithium with oxygen, single vacancies and divacancies and that the lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance
Chaotic quantum dots with strongly correlated electrons
Quantum dots pose a problem where one must confront three obstacles:
randomness, interactions and finite size. Yet it is this confluence that allows
one to make some theoretical advances by invoking three theoretical tools:
Random Matrix theory (RMT), the Renormalization Group (RG) and the 1/N
expansion. Here the reader is introduced to these techniques and shown how they
may be combined to answer a set of questions pertaining to quantum dotsComment: latex file 16 pages 8 figures, to appear in Reviews of Modern Physic
Effects of processing and dopant on radiation damage removal in silicon solar cells
Gallium and boron doped silicon solar cells, processed by ion-implantation followed by either laser or furnace anneal were irradiated by 1 MeV electrons and their post-irradiation recovery by thermal annealing determined. During the post-irradiation anneal, gallium-doped cells prepared by both processes recovered more rapidly and exhibited none of the severe reverse annealing observed for similarly processed 2 ohm-cm boron doped cells. Ion-implanted furnace annealed 0.1 ohm-cm boron doped cells exhibited the lowest post-irradiation annealing temperatures (200 C) after irradiation to 5 x 10 to the 13th e(-)/sq cm. The drastically lowered recovery temperature is attributed to the reduced oxygen and carbon content of the 0.1 ohm-cm cells. Analysis based on defect properties and annealing kinetics indicates that further reduction in annealing temperature should be attainable with further reduction in the silicon's carbon and/or divacancy content after irradiation
Limiting Laws of Linear Eigenvalue Statistics for Unitary Invariant Matrix Models
We study the variance and the Laplace transform of the probability law of
linear eigenvalue statistics of unitary invariant Matrix Models of
n-dimentional Hermitian matrices as n tends to infinity. Assuming that the test
function of statistics is smooth enough and using the asymptotic formulas by
Deift et al for orthogonal polynomials with varying weights, we show first that
if the support of the Density of States of the model consists of two or more
intervals, then in the global regime the variance of statistics is a
quasiperiodic function of n generically in the potential, determining the
model. We show next that the exponent of the Laplace transform of the
probability law is not in general 1/2variance, as it should be if the Central
Limit Theorem would be valid, and we find the asymptotic form of the Laplace
transform of the probability law in certain cases
The effects of lithium counterdoping on radiation damage and annealing in n(+)p silicon solar cells
Boron-doped silicon n(+)p solar cells were counterdoped with lithium by ion implantation and the resultant n(+)p cells irradiated by 1 MeV electrons. Performance parameters were determined as a function of fluence and a deep level transient spectroscopy (DLTS) study was conducted. The lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. Isochronal annealing studies of cell performance indicate that significant annealing occurs at 100 C. Isochronal annealing of the deep level defects showed a correlation between a single defect at E sub v + 0.43 eV and the annealing behavior of short circuit current in the counterdoped cells. The annealing behavior was controlled by dissociation and recombination of this defect. The DLTS studies showed that counterdoping with lithium eliminated three deep level defects and resulted in three new defects. The increased radiation resistance of the counterdoped cells is due to the interaction of lithium with oxygen, single vacancies and divacancies. The lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance
Solitons in the Calogero model for distinguishable particles
We consider a large two-family Calogero model in the Hamiltonian,
collective-field approach. The Bogomol'nyi limit appears and the corresponding
solutions are given by the static-soliton configurations. Solitons from
different families are localized at the same place. They behave like a paired
hole and lump on the top of the uniform vacuum condensates, depending on the
values of the coupling strengths. When the number of particles in the first
family is much larger than that of the second family, the hole solution goes to
the vortex profile already found in the one-family Calogero model.Comment: 14 pages, no figures, late
Exact coherent states of a harmonically confined Tonks-Girardeau gas
Using a scaling transformation we exactly determine the dynamics of an
harmonically confined Tonks-Girardeau gas under arbitrary time variations of
the trap frequency. We show how during a one-dimensional expansion a
``dynamical fermionization'' occurs as the momentum distribution rapidly
approaches an ideal Fermi gas distribution, and that under a sudden change of
the trap frequency the gas undergoes undamped breathing oscillations displaying
alternating bosonic and fermionic character in momentum space. The absence of
damping in the oscillations is a peculiarity of the truly Tonks regime.Comment: 4 pages, 2 figures, published versio
Ground-state energy of the electron liquid in ultrathin wires
The ground-state energy and the density correlation function of the electron
liquid in a thin one-dimensional wire are computed. The calculation is based on
an approximate mapping of the problem with a realistic Coulomb interaction law
onto exactly solvable models of mathematical physics. This approach becomes
asymptotically exact in the limit of small wire radius but remains numerically
accurate even for modestly thin wires.Comment: (v3) Replaced with the published version. 4 pages, 1 figur
Energy localization in two chaotically coupled systems
We set up and analyze a random matrix model to study energy localization and
its time behavior in two chaotically coupled systems. This investigation is
prompted by a recent experimental and theoretical study of Weaver and Lobkis on
coupled elastomechanical systems. Our random matrix model properly describes
the main features of the findings by Weaver and Lobkis. Due to its general
character, our model is also applicable to similar systems in other areas of
physics -- for example, to chaotically coupled quantum dots.Comment: 20 pages, 15 figure
Spectral fluctuations of tridiagonal random matrices from the beta-Hermite ensemble
A time series delta(n), the fluctuation of the nth unfolded eigenvalue was
recently characterized for the classical Gaussian ensembles of NxN random
matrices (GOE, GUE, GSE). It is investigated here for the beta-Hermite ensemble
as a function of beta (zero or positive) by Monte Carlo simulations. The
fluctuation of delta(n) and the autocorrelation function vary logarithmically
with n for any beta>0 (1<<n<<N). The simple logarithmic behavior reported for
the higher-order moments of delta(n) for the GOE (beta=1) and the GUE (beta=2)
is valid for any positive beta and is accounted for by Gaussian distributions
whose variances depend linearly on ln(n). The 1/f noise previously demonstrated
for delta(n) series of the three Gaussian ensembles, is characterized by
wavelet analysis both as a function of beta and of N. When beta decreases from
1 to 0, for a given and large enough N, the evolution from a 1/f noise at
beta=1 to a 1/f^2 noise at beta=0 is heterogeneous with a ~1/f^2 noise at the
finest scales and a ~1/f noise at the coarsest ones. The range of scales in
which a ~1/f^2 noise predominates grows progressively when beta decreases.
Asymptotically, a 1/f^2 noise is found for beta=0 while a 1/f noise is the rule
for beta positive.Comment: 35 pages, 10 figures, corresponding author: G. Le Cae
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