132 research outputs found
Influence of electric fields on dielectric properties of GPI ferroelectric
Using modified microscopic model of GPI by taking into account the
piezoelectric coupling with strains in the frames of
two-particle cluster approximation, the components of polarization vector and
static dielectric permittivity tensor of the crystal at applying the external
transverse electric fields and are calculated. An analysis of the
influence of these fields on thermodynamic characteristics of GPI is carried
out. A satisfactory quantitative description of the available experimental data
for these characteristics has been obtained at a proper choice of the model
parameters.Comment: 17 pages, 17 figure
New combined PIC-MCC approach for fast simulation of a radio frequency discharge at low gas pressure
A new combined PIC-MCC approach is developed for accurate and fast simulation
of a radio frequency discharge at low gas pressure and high density of plasma.
Test calculations of transition between different modes of electron heating in
a ccrf discharge in helium and argon show a good agreement with experimental
data.
We demonstrate high efficiency of the combined PIC-MCC algorithm, especially
for the collisionless regime of electron heating.Comment: 6 paged, 8 figure
The effect of discharge chamber geometry on the ignition of low-pressure rf capacitive discharges
This paper reports measured and calculated breakdown curves in several gases of rf capacitive discharges excited at 13.56 MHz in chambers of three different geometries: parallel plates surrounded by a dielectric cylinder (“symmetric parallel plate”), parallel plates surrounded by a
grounded metallic cylinder (“asymmetric parallel plate”), and parallel plates inside a much larger grounded metallic chamber (“large chamber”). The breakdown curves for the symmetric chamber have a multivalued section at low pressure. For the asymmetric chamber the breakdown curves are shifted to lower pressures and rf voltages, but the multivalued feature is still present. At higher pressures the breakdown voltages are much lower than for the symmetric geometry. For the large chamber geometry the multivalued behavior is not observed. The breakdown curves were also calculated using a numerical model based on fluid equations, giving results that are in satisfactory
agreement with the measurements
Dynamics of spin correlations in the spin-1/2 isotropic XY chain in a transverse field
Dynamic xx spin pair correlation functions for the isotropic spin-1/2 XY
chain are calculated numerically for long open chains in the presence of a
transverse magnetic field at finite temperature. As an application we discuss
the temperature dependence of the spin-spin relaxation time in PrCl_3.Comment: 2 pages, latex, 2 figures, abstract of the paper presented at Ampere
Summer School ``Applications of Magnetic Resonance in Novel Materials''
Nafplion, Greece, 3-9 September, 2000, partially published in J. Phys. A:
Math. Gen. 33, 3063 (2000
Modes and the alpha-gamma transition in rf capacitive discharges in N2O at different rf frequencies
This paper reports current-voltage characteristics and pressure-voltage transition curves from the weak-current a-mode to the strong-current g-mode for rf capacitive discharges in N2O at
frequencies of 2 MHz, 13.56 MHz, and 27.12 MHz. At 2 MHz the rf discharge is mostly resistive whereas at 13.56 MHz and 27.12 MHz it is mostly capacitive. The weak-current a-mode was found to exist only above a certain minimum gas pressure for all frequencies studied [N. Yatsenko Sov. Phys. Tech. Phys. 26, 678 (19810] previously proposed that the a−g transition corresponds to
breakdown of the sheaths. However, we show that this is the case only for sufficiently high gas pressures. At lower pressure there is a smooth transition from the weak-current a-mode to a strong-current g-mode, in which the sheaths produce fast electrons but the sheath has not undergone breakdown
Acoustic Response to the Action of Nanosecond Laser Pulses on an In/CdTe Thin-Film Heterostructure
The photothermoacoustic method has been used for diagnostics of thermobarodynamic processes in the metal In(400 nm)/semiconductor (CdTe) thin-film system under nanosecond laser irradiation (7 ns, λ = 532 nm) in natural conditions (in air) and in a liquid medium (water). From the analysis of the data obtained, the dependence of the pressure induced in the energy-release region on the irradiation energy den-sity has been established and the melting threshold of In film has been determined. Under irradiation of In/CdTe in water, the pressure is higher than in air: 17 times higher at the melting threshold of In film and 30 times higher at twice the temperature. It has been found that the laser pulse treatment of In/CdTe/Au samples in water makes it possible to obtain diode structures with better parameters: smaller leak currents and a steeper current-voltage characteristic under the forward bias of the p-n junction
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