A. C. Abeyta

University of Illinois Urbana-Champaign

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Igor V. Roshchin

Texas A&M University

L. H. Greene

University of Illinois Urbana-Champaign

Paul W. Bohn

University of Notre Dame

J. F. Dorsten

University of Illinois Urbana-Champaign

T. A. Tanzer

University of Illinois Urbana-Champaign

G Küchler

Klinik Sonnenhof

W. L. Feldmann

University of Illinois Urbana-Champaign

J. F. Klem

Sandia National Laboratories

P. F. Miceli

University of Missouri

Michael C. Tringides

Ames National Laboratory

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University of Illinois Urbana-Champaign

Ames National Laboratory

Iowa State University

United States Department of Energy

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University of Washington

University of Wisconsin–Madison

Moscow Institute of Physics and Technology

Seattle University

University of Maryland, College Park

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Observation of the superconducting proximity effect in Nb/InAs andNbNx/InAsby Raman scattering

Physical review. B, Condensed matter (2002)

Igor V. Roshchin A. C. Abeyta L. H. Greene T. A. Tanzer J. F. Dorsten

High-quality thin Nb and NbN films (60-100 \AA{}) are grown on (100) ${n}^{+}\ensuremath{-}\mathrm{InAs}$ ${(n=10}^{19}{\mathrm{cm}}^{\ensuremath{-}3})$ substrates by dc-magnetron sputter deposition. Studies of the electronic properties of interfaces between the superconductor and the semiconductor are done by Raman scattering measurements. The superconducting proximity effect at superconductor-semiconductor interfaces is observed through its impact on inelastic light scattering intensities originating from the near-interface region of InAs. The InAs longitudinal optical phonon LO mode $(237{\mathrm{cm}}^{\ensuremath{-}1})$ and the plasmon-phonon coupled modes ${L}_{\ensuremath{-}}$ $(221{\mathrm{cm}}^{\ensuremath{-}1})$ and ${L}_{+}$ (1100 to $1350{\mathrm{cm}}^{\ensuremath{-}1}),$ for ${n}^{+}=1\ifmmode\times\else\texttimes\fi{}{10}^{19}\ensuremath{-}2\ifmmode\times\else\texttimes\fi{}{10}^{19}{\mathrm{cm}}^{\ensuremath{-}3}$ are measured. The intensity ratio of the LO mode (associated with the near-surface charge accumulation region, in InAs) to that of the ${L}_{\ensuremath{-}}$ mode (associated with bulk InAs), is observed to increase by up to 40% below the superconducting transition temperature. This temperature-dependent change in light scattering properties is only observed with high quality superconducting films and when the superconductor and the semiconductor are in good electrical contact. A few possible mechanisms of the observed effect are proposed.

10.1103/physrevb.66.134530

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<title>Optical detection of the superconducting proximity effect</title>

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1996)

L. H. Greene A. C. Abeyta Igor V. Roshchin Ian Robinson J. F. Dorsten

We present the first detection of a superconducting proximity effect by optical techniques. Raman scattering on n⁺-InAs is performed through very thin, high-quality, superconducting Nb films grown directly on the (100)InAs surface. The 6 to 10 nm thick Nb films exhibit T_cs of 2.5 to 5.5 K, as measured by electronic transport, and are flat to approximately 0.5 nm, as measured by x-ray reflectivity. As the Nb/InAs structure is cooled below the superconducting transition temperature, the magnitude of the unscreened LO phonon mode, associated with the surface charge accumulation layer in the InAs, is observed to be enhanced by more than 40%. This reversible change is observed only when the Nb is in good electrical contact with the InAs.

Superconducting transition temperature

Transition temperature

10.1117/12.241775

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Studies of the Proximity Effect in Superconductor/Semiconductor Interfaces using Raman Spectroscopy.

APS March Meeting Abstracts (1998)

Igor V. Roshchin A. C. Abeyta William L. Murphy L. H. Greene T. A. Tanzer

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Measurement of a three-dimensional photonic band gap in a crystal structure made of dielectric rods

Physical review. B, Condensed matter (1994)

Ekmel Özbay A. C. Abeyta G. Tuttle Michael C. Tringides R. Biswas

We have designed, fabricated, and tested a three-dimensional photonic-band-gap structure. The structure is built by an orderly stacking of dielectric rods. A network analyzer is used to measure the transmission and dispersion relations of electromagnetic waves along several crystal directions. The experimental results are in good agreement with the theoretical calculations. The structure is different from that previously suggested, as it is already used to improve the midgap frequency by almost two orders of magnitude, and it offers a viable geometry to extend the photonic band gap to optical regimes.

Rod

Yablonovite

Dispersion relation

10.1103/physrevb.50.1945

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Optical detection of the superconducting proximity effect: Raman scattering on Nb/InAs

Czechoslovak Journal of Physics (1996)

L. H. Greene J. F. Dorsten Igor V. Roshchin A. C. Abeyta T. A. Tanzer

10.1007/bf02583678

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Citations (3)

Proximity-Effect Studies of Superconductor/Semiconductor Interfaces with Raman Scattering.

APS March Meeting Abstracts (1997)

Igor V. Roshchin A. C. Abeyta G Küchler L. H. Greene T. A. Tanzer

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The Superconducting Proximity Effect in Thin Nb Films on InAs.

APS March Meeting Abstracts (1996)

A. C. Abeyta Igor V. Roshchin L. H. Greene J. F. Dorsten T. A. Tanzer

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Characterizing Gas Flow in the Build Chamber of Laser Powder Bed Fusion Systems Utilizing Particle Image Velocimetry: A Path to Improvements

A. C. Abeyta Cole Nouwens Andrew Jones Troy A. Haworth A. Montelione

Velocimetry

Particle (ecology)

Particle tracking velocimetry

10.2139/ssrn.5125860

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Electronic and vibrational Raman studies of the superconducting proximity effect in Nb:InAs heterojunctions

J. F. Dorsten A. C. Abeyta Igor V. Roshchin L. H. Greene

Electronic Raman scattering from coupled phonon-plasmon model and vibrational scattering from LO phonon modes confined to that near-surface region of InAs have been used to probe the change electron density, n, associated with transition through T. of a thin Nb film electrode. In contrast to the vast majority of other III-V surfaces, InAs displays an electron charge accumulation region (CAR). At the doping densities used in these experiments the width of the CAR is of the order 50A. Confining electrons to such a small region of space gives rise to quantum size effects, and the result in the Raman spectrum is large-q contributions to the scattering mechanism for LO phonons. Because the LO phonon is effectively screened in the bulk of the InAs the relative magnitudes of the phonon and coupled phonon-plasmon bands can be used to monitor relative changes in the n in the near-surface region. Experiments with Nb:InAs heterojunctions make use of direct excitation through the Nb overlayer and demonstrate that cooling the superconductor through its transition temperature, can have a dramatic effect on n near the interface.

Overlayer

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Planar tunneling spectroscopy of thin-film Nb, Nb/normal metal and Nb/semiconductor structures

A. C. Abeyta

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