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Your search keyword '"Frost, J. E. F."' showing total 176 results
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176 results on '"Frost, J. E. F."'

1. Experimental studies of T--shaped quantum dot transistors: phase-coherent electron transport

Author

Liang, C. -T., Frost, J. E. F., Pepper, M., Ritchie, D. A., and Jones, G. A. C.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We have measured the low-temperature transport properties of a T-shaped quantum dot. Replicated oscillations superimposed on one-dimensional conductance steps are observed. These structures are consistent with electron phase-coherent length resonance effects in the ballistic regime. Using a simple model, we suggest that both one-dimensional and two-dimensional electron-electron scattering gives rise to electron phase-breaking in our system., Comment: 9 pages, TeX, to be published in Solid State Communications

Published
1997
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2. Resonant transmission through an open quantum dot

Author

Liang, C. -T., Castleton, I. M., Frost, J. E. F., Barnes, C. H. W., Smith, C. G., Ford, C. J. B., Ritchie, D. A., and Pepper, M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We have measured the low-temperature transport properties of a quantum dot formed in a one-dimensional channel. In zero magnetic field this device shows quantized ballistic conductance plateaus with resonant tunneling peaks in each transition region between plateaus. Studies of this structure as a function of applied perpendicular magnetic field and source-drain bias indicate that resonant structure deriving from tightly bound states is split by Coulomb charging at zero magnetic field., Comment: To be published in Phys. Rev. B (1997). 8 LaTex pages with 5 figures

Published
1997
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3. Experimental evidence of a metal-insulator transition in a half-filled Landau level

Author

Liang, C. -T., Frost, J. E. F., Simmons, M. Y., Ritchie, D. A., and Pepper, M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We have measured the low-temperature transport properties of a high-mobility front-gated GaAs/Al_{0.33}Ga_{0.67}As heterostructure. By changing the applied gate voltage, we can vary the amount of disorder within the system. At a Landau level filling factor $\nu =1/2$, where the system can be described by the composite fermion picture, we observe a crossover from metallic to insulating behaviour as the disorder is increased. Experimental results and theoretical prediction are compared., Comment: To be published in Solid State Communications. 4 figures

Published
1997
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4. Distribution Function Analysis of Mesoscopic Hopping Conductance Fluctuations

Author

Hughes, R. J. F., Savchenko, A. K., Frost, J. E. F., Linfield, E. H., Nicholls, J. T., Pepper, M., Kogan, E., and Kaveh, M.

Subjects
Condensed Matter
Abstract

Variable-range hopping (VRH) conductance fluctuations in the gate-voltage characteristics of mesoscopic GaAs and Si transistors are analyzed by means of their full distribution functions (DFs). The forms of the DF predicted by the theory of Raikh and Ruzin have been verified under controlled conditions for both the long, narrow wire and the short, wide channel geometries. The variation of the mean square fluctuation size with temperature in wires fabricated from both materials is found to be described quantitatively by Lee's model of VRH along a 1D chain. Armed with this quantitative validation of the VRH model, the DF method is applied to the problem of magnetoconductance in the insulating regime. Here a non-monotonic variation of the magnetoconductance is observed in Si MOSFETS whose sign at low magnetic fields is dependent on the channel geometry. The origin of this defect is discussed within the framework of the interference model of VRH magnetoconductance in terms of narrowing of the DF in a magnetic field., Comment: Revtex, 24 pages, 9 figures, figures are added

Published
1996
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5. Ballistic Composite Fermions in Semiconductor Nanostructures

Author

Frost, J. E. F., Liang, C. -T., Mace, D. R., Simmons, M. Y., Ritchie, D. A., and Pepper, M.

Subjects
Condensed Matter
Abstract

We report the results of two fundamental transport measurements at a Landau level filling factor $\nu$ of 1/2. The well known ballistic electron transport phenomena of quenching of the Hall effect in a mesoscopic cross-junction and negative magnetoresistance of a constriction are observed close to B~=~0 and $\nu~=~ 1/2$. The experimental results demonstrate semi-classical charge transport by composite fermions, which consist of electrons bound to an even number of flux quanta., Comment: 9 pages TeX 3.1415 C version 6.1, 3 PostScript figures

Published
1996
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6. The Aharonov-Bohm Effect in the Fractional Quantum Hall Regime

Author

Franklin, J. D. F., Zailer, I., Ford, C. J. B., Simpson, P. J., Frost, J. E. F., Ritchie, D. A., Simmons, M. Y., and Pepper, M.

Subjects
Condensed Matter
Abstract

We have investigated experimentally resonant tunnelling through single-particle states formed around an antidot by a magnetic field, in the fractional quantum Hall regime. For 1/3 filling factor around the antidot, Aharonov-Bohm oscillations are observed with the same magnetic field period as in the integer quantum Hall regime. All our measurements are consistent with quasiparticles of fractional charge e*. However, the results are also consistent with particles of any charge (>= e*) as the system must rearrange every time the flux enclosed increases by h/e., Comment: Postscript, 4 pages, gzipped (350 kB)

Published
1995
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8. Thermal Transport in Free-Standing GaAs Wires in a High Magnetic Field

Author

Potts, A., Singleton, J., Janssen, T. J. B. M., Kelly, M. J., Smith, C. G., Hasko, D. G., Peacock, D. C., Frost, J. E. F., Ritchie, D. A., Jones, G. A. C., Cleaver, J. R., Ahmed, H., Cardona, Manuel, editor, Fulde, Peter, editor, von Klitzing, Klaus, editor, Queisser, Hans-Joachim, editor, Lotsch, Helmut K. V., editor, and Landwehr, Gottfried, editor

Published
1992
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9. Far-Infrared Transmission of Voltage-Tunable GaAs-(Ga,Al)As Quantum Dots in High Magnetic Fields

Author

Patel, N. K., Janssen, T. J. B. M., Singleton, J., Pepper, M., Ahmed, H., Hasko, D. G., Brown, R. J., Perenboom, J. A. A. J., Jones, G. A. C., Frost, J. E. F., Peacock, B. C., Jones, D. A., Cardona, Manuel, editor, Fulde, Peter, editor, von Klitzing, Klaus, editor, Queisser, Hans-Joachim, editor, Lotsch, Helmut K. V., editor, and Landwehr, Gottfried, editor

Published
1992
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10. Photoconductive Response of a Quasi-One Dimensional Channel

Author

Janssen, T. J. B. M., Patel, N. K., Singleton, J., Pepper, M., Ahmed, H., Hasko, D. G., Brown, R. J., Perenboom, J. A. A. J., Jones, G. A. C., Frost, J. E. F., Peacock, D. C., Ritchie, D. A., Ferry, David K., editor, Barker, John R., editor, and Jacoboni, Carlo, editor

Published
1991
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14. Photoconductive Response of a Quasi-One Dimensional Channel

Author

Janssen, T. J. B. M., primary, Patel, N. K., additional, Singleton, J., additional, Pepper, M., additional, Ahmed, H., additional, Hasko, D. G., additional, Brown, R. J., additional, Perenboom, J. A. A. J., additional, Jones, G. A. C., additional, Frost, J. E. F., additional, Peacock, D. C., additional, and Ritchie, D. A., additional

Published
1991
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18. Quantisation of Resistance in One-Dimensional Ballistic Transport

Author

Wharam, D. A., Thornton, T. J., Newbury, R., Pepper, M., Ahmed, H., Frost, J. E. F., Hasko, D. G., Peacock, D. C., Ritchie, D. A., Jones, G. A. C., Cardona, Manuel, editor, Fulde, Peter, editor, von Klitzing, Klaus, editor, Queisser, Hans-Joachim, editor, Lotsch, Helmut K. V., editor, and Landwehr, Gottfried, editor

Published
1989
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20. Plasmon excitation and self-coupling in a bi-periodically modulated two-dimensional electron gas.

Author

Wilkinson, R. J., Ager, C. D., Duffield, T., Hughes, H. P., Hasko, D. G., Ahmed, H., Frost, J. E. F., Peacock, D. C., Ritchie, D. A., Jones, G. A. C., Whitehouse, C. R., and Apsley, N.

Subjects
PLASMONS (Physics), INFRARED spectroscopy, HETEROSTRUCTURES
Abstract

Reports on far infrared (FIR) studies of plasmons in spatially modulated two-dimensional electron gases in AlGaAs/GaAs heterostructures using biased overlaid metal gratings. Sample structure, characterization and optical measurements; Scattering matrix calculations; FIR spectroscopic studies and analysis.

Published
1992
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21. Sulfur doping behavior of gallium antimonide grown by molecular-beam epitaxy.

Author

Poole, I., Lee, M. E., Singer, K. E., Frost, J. E. F., Kerr, T. M., Wood, C. E. C., Andrews, D. A., Rothwell, W. J. M., and Davies, G. J.

Subjects
SEMICONDUCTOR doping, GALLIUM compounds, MOLECULAR beam epitaxy
Abstract

Investigates the sulphur doping behavior of gallium antimonide (GaSb) grown by molecular-beam epitaxy. Challenges in doping of MBE-grown GaSb; Methodology of the study; Discussion on the result of the study.

Published
1988
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24. Low temperature operation of Ge-Ag ohmic contacts to a high mobility two dimensional electron gas.

Author

Chabasseur-Molyneux, V., Frost, J. E. F., Tribble, M. J., Grimshaw, M. P., Ritchie, D. A., Churchill, A. C., Jones, G. A. C., Pepper, M., and Burroughes, J. H.

Subjects
*OHMIC contacts, *GERMANIUM, *SILVER, *SECONDARY ion mass spectrometry
Abstract

Presents a study which demonstrated germanium-silver ohmic contacts with good dimensional control to a two dimensional electron gas operating at low temperatures. Result of secondary ion mass spectroscopy for the annealed sample; Factor that contributed to the contact resistance; Potential applications of the ohmic contacts to back-gated structures.

Published
1993

25. Low-frequency measurements of cyclotron resonance in a high-mobility 2D electron gas in GaAs/AlGaAs heterostructures.

Author

Polisskii, A. V., Talyanskii, V. I., Cole, J., Smith, C. G., Pepper, M., Ritchie, D. A., Frost, J. E. F., and Jones, G. A. C.

Subjects
CYCLOTRON resonance, HETEROSTRUCTURES, ELECTRON gas
Abstract

Presents information on a study which investigated the cyclotron resonance in gallium heterostructures containing a high-mobility two-dimensional electron gas. Background of the study; Methodology of the study; Results and discussion.

Published
1992
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26. Weak localization and electron-electron interactions in a two-dimensional grid lateral surface superlattice

Author

LIANG, C T, SMITH, C G, NICHOLLS, J T, HUGHES, R J F, PEPPER, M, FROST, J E F, RITCHIE, D A, GRIMSHAW, M P, and JONES, G A C

Subjects
MAGNETORESISTANCE OSCILLATIONS, Research Groups and Centres\Physics\Low Temperature Physics, BALLISTIC TRANSPORT, NEGATIVE DIFFERENTIAL CONDUCTIVITY, GAS, SYSTEMS, Faculty of Science\Physics, SCATTERING, METALS, FLUCTUATIONS, FIELD, LOW-TEMPERATURES
Abstract

Low-field magnetoresistance measurements were performed on a two-dimensional grid lateral surface superlattice (LSSL) fabricated on a GaAs/AlxGa1-xAs heterojunction. From a one-parameter fit to the two-dimensional weak-localization theory we have obtained the effective inelastic scattering length at different temperatures. By subtracting the weak-localization term, we have also investigated the electron-electron interactions in this system. Both localization and interaction effects saturate at low temperatures when the inelastic scattering length and thermal diffusion length are longer than the period of the LSSL. At higher temperatures, when the thermal diffusion length becomes comparable to the period of the LSSL, the electron-electron interaction term causes the conductivity to decrease logarithmically with temperature. These results can be explained in terms of coherent backscattering of the electrons in a fraction of the electron puddles formed below the superlattice gate. Disorder ensures that the cells showing these results are not neighbors, so that this effect is an ensemble average of many unit cells several periods apart.

Published
1995
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27. Phase coherence, interference, and conductance quantization in a confined two-dimensional hole gas

Author

ZAILER, I, FROST, J E F, FORD, C J B, PEPPER, M, SIMMONS, M Y, RITCHIE, D A, NICHOLLS, J T, and JONES, G A C

Subjects
Research Groups and Centres\Physics\Low Temperature Physics, CHANNEL, Faculty of Science\Physics, Quantitative Biology::Tissues and Organs, RESISTANCE FLUCTUATIONS, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, POINT CONTACTS, TRANSPORT, RINGS, WIRES
Abstract

A system of two parallel constrictions in a two-dimensional hole gas has been studied. At zero magnetic-field conductance quantization is observed through the individual constrictions. At high magnetic fields Aharonov-Bohm oscillations result from resonant tunneling through states encircling the repulsive potential between the constrictions. The oscillations demonstrate directly phase-coherent transport of holes.

Published
1995
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28. Single-electron tunneling and Coulomb charging effects in aysmmetric double-barrier resonant-tunneling diodes

Author

TEWORDT, M, MARTINMORENO, L, NICHOLLS, J T, PEPPER, M, KELLY, M J, LAW, V J, RITCHIE, D A, FROST, J E F, and JONES, G A C

Subjects
Research Groups and Centres\Physics\Low Temperature Physics, STATES, Faculty of Science\Physics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect
Abstract

Resonant tunneling is studied in an ultrasmall asymmetric GaAs-AlxGa1-xAs double-barrier diode at low temperatures. In reverse bias, spikelike current-voltage characteristics are observed and assigned to electrons tunneling from zero-dimensional (OD) states in the accumulation layer to OD states in the well. The OD-OD tunneling reflects the single-electron spectrum without Coulomb charging effects. In forward bias, steplike current-voltage characteristics are observed and ascribed to tunneling from one-dimensional subbands in the emitter contacts through OD states in the well, accompanied by Coulomb charging effects. A moderate magnetic field (B almost-equal-to 4 T) parallel to the current improves the flatness of the plateaus.

Published
1993
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29. Properties of a ballistic quasi-one-dimensional constriction in a parallel high magnetic field

Author

PATEL, N K, NICHOLLS, J T, MARTINMORENO, L, PEPPER, M, FROST, J E F, RITCHIE, D A, and JONES, G A C

Subjects
Research Groups and Centres\Physics\Low Temperature Physics, 2D ELECTRON-GAS, SUBBANDS, TRANSMISSION, Faculty of Science\Physics, HETEROJUNCTION, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, POINT CONTACTS, TRANSPORT, QUANTIZED CONDUCTANCE
Abstract

We have investigated the magnetic properties of a ballistic quasi-one-dimensional channel, in a GaAs-AlxGa1-xAs heterojunction, when the magnetic field is applied in the plane of the two-dimensional electron gas. At high magnetic fields, and high applied source-drain voltage, the devices show differential conductance plateaus quantized in units of e2/2h. This is a consequence of the combined effect of the electric field, which causes the number of conducting subbands to be different in the two current directions, and the Zeeman splitting of the one-dimensional subbands. When the magnetic field is parallel to the current direction, the g factor is 1.1 +/- 0.1; and when the field is perpendicular to the current, the g factor is reduced.

Published
1992

39. Measurements of a composite fermion split-gate device

Author

Liang, C. -T., primary, Smith, C. G., additional, Mace, D. R., additional, Nicholls, J. T., additional, Frost, J. E. F., additional, Simmons, M. Y., additional, Hamilton, A. R., additional, Ritchie, D. A., additional, and Pepper, M., additional

Published
1996
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