4,525 research outputs found
Observation of a uniform temperature dependence in the electrical resistance across the structural phase transition in thin film vanadium oxide ()
An electrical study of thin films in the vicinity of the structural
phase transition at shows (a) that the electrical resistance
follows over the -range,
covering both sides of the structural transition, and (b) a history dependent
hysteresis loop in upon thermal cycling. These features are attributed here
to transport through a granular network.Comment: 3 pages, 3 color figure
Transport study of Berry's phase, the resistivity rule, and quantum Hall effect in graphite
Transport measurements indicate strong oscillations in the Hall-,,
and the diagonal-, , resistances and exhibit Hall plateaus at the
lowest temperatures, in three-dimensional Highly Oriented Pyrolytic Graphite
(HOPG). At the same time, a comparative Shubnikov-de Haas-oscillations-based
Berry's phase analysis indicates that graphite is unlike the GaAs/AlGaAs 2D
electron system, the 3D n-GaAs epilayer, semiconducting ,
and some other systems. Finally, we observe the transport data to follow
. This feature is consistent with
the observed relative phases of the oscillatory and .Comment: 5 pages, 4 figure
Demonstration of a 1/4 cycle phase shift in the radiation-induced oscillatory-magnetoresistance in GaAs/AlGaAs devices
We examine the phase and the period of the radiation-induced
oscillatory-magnetoresistance in GaAs/AlGaAs devices utilizing in-situ magnetic
field calibration by Electron Spin Resonance of DiPhenyl-Picryl-Hydrazal. The
results confirm a -independent 1/4 cycle phase shift with respect to the condition for , and they also suggest a small
( 2%) reduction in the effective mass ratio, , with respect
to the standard value for GaAs/AlGaAs devices.Comment: 4 pages, 4 color figure
Radiation-induced magnetoresistance oscillations in two-dimensional electron systems under bichromatic irradiation
We analyze the magnetoresistance oscillations in high-mobility
two-dimensional electron systems induced by the combined driving of two
radiation fields of frequency and , based on the
balance-equation approach to magnetotransport for high-carrier-density systems
in Faraday geometry. It is shown that under bichromatic irradiation of
, most of the characterstic peak-valley pairs in the
curve of versus magnetic field in the case of monochromatic
irradiation of either or disappear, except the one around
or . oscillations
show up mainly as new peak-valley structures around other positions related to
multiple photon processes of mixing frequencies ,
, etc. Many minima of these resistance peak-valley pairs can
descend down to negative with enhancing radiation strength, indicating the
possible bichromaticzero-resistance states.Comment: 5 pages, 3 figures. Accepted for publication in Phys. Rev.
Phase study of oscillatory resistances in microwave-irradiated- and dark- GaAs/AlGaAs devices: Indications of a new class of integral quantum Hall effect
We report the experimental results from a dark study and a photo-excited
study of the high mobility GaAs/AlGaAs system at large filling factors, .
At large-, the dark study indicates several distinct phase relations
("Type-1", "Type-2", and "Type-3") between the oscillatory diagonal- and Hall-
resistances, as the canonical Integral Quantum Hall Effect (IQHE) is manifested
in the "Type-1" case of approximately orthogonal diagonal- and Hall resistance-
oscillations. Surprisingly, the investigation indicates quantum Hall plateaus
also in the "Type-3" case characterized by approximately "anti-phase" Hall- and
diagonal- resistance oscillations, suggesting a new class of IQHE.
Transport studies under microwave photo-excitation exhibit radiation-induced
magneto-resistance oscillations in both the diagonal, , and
off-diagonal, , resistances. Further, when the radiation-induced
magneto-resistance oscillations extend into the quantum Hall regime, there
occurs a radiation-induced non-monotonic variation in the amplitude of
Shubnikov-de Haas (SdH) oscillations in \textit{vs}. B, and a
non-monotonic variation in the width of the quantum Hall plateaus in .
The latter effect leads into the vanishing of IQHE at the minima of the
radiation-induced oscillations with increased photo-excitation. We
reason that the mechanism which is responsible for producing the non-monotonic
variation in the amplitude of SdH oscillations in under
photo-excitation is also responsible for eliminating, under photo-excitation,
the novel "Type-3" IQHE in the high mobility specimen.Comment: 11 pages, 12 color figure
Effect of Neat Sardine Oil with Varies Blends on the Performance and Emission Characteristics of Diesel Engine
This study investigates the performance and emission characteristics of a diesel engine which is fuelled with neat sardine oil and diesel. A single cylinder four stroke diesel engine was used for the experiments at various load and speed of 1500 rpm. An AVL5 gas analyzer and a smoke meter were used for the measurements of exhaust gas emission. The results showed that break thermal efficiency is decreased and CO (Carbon-monoxide), HC (Hydro-Carbon) in the exhaust is increased when fuelled with neat sardine oil compared to diesel except NOx (Nitrogen Oxide). The future scope of the work is to do some modification (e.g may be engine, piston or values) in the engine to get better performance in same blending ratio
Spray Deposition and Characterization of p-type Li doped NiO Thin Films
Undoped and lithium doped nickel oxide (Li doped NiO) thin films have been prepared onto glass substrates at 450 Β°C by chemical spray pyrolysis technique. The effect of lithium (Li) concentrations on the structural, optical, photoluminescence and electrical properties of the Li doped NiO films were studied by X-ray diffraction (XRD), UV-vis- NIR spectrophotometer, Photoluminescence (PL) spectrophotometer, Hot probe and Hall effect measurement system. The PL results confirmed that the band gap reduces when the lithium concentration increases. The structural properties of undoped and Li doped NiO films showed polycrystalline cubic structure. The optical transmittance and band gap values of the films decreases, while the absorption values increases with the increase in Li concentration. Moreover, it has been observed that the resistivity of the above films decreases with the increase in Li concentration
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