Bulletin of the American Physical Society
80th Annual Meeting of the APS Southeastern Section
Volume 58, Number 17
Wednesday–Saturday, November 20–23, 2013; Bowling Green, Kentucky
Session CB: Condensed Matter and Nanoscience II |
Hide Abstracts |
Chair: David Hilton, University of Alabama at Birmingham Room: 1 |
Thursday, November 21, 2013 11:00AM - 11:12AM |
CB.00001: All-Optical Silicon-Based Modulators Driven by an Ultrafast Phase-Change Material Kent Hallman, Judson Ryckman, Robert Marvel, Sharon Weiss, Richard Haglund With increasing demand for higher-speed telecommunications, there is a need for optical modulators (OMs) designed to operate at the telecommunications wavelength. Although switching speeds of OMs compatible with current Si-based CMOS technology have increased recently, most devices are limited by the weak electro-optic effect in Si. We incorporated a phase-change material, vanadium dioxide (VO$_{2}$), into the model Si-based OM geometry, the silicon ring resonator (SRR). VO$_{2}$ thin films irradiated with ultrafast pulses can switch from their insulating ground state to an excited metallic state exhibiting different optical constants in a fraction of a picosecond. Capitalizing on this large, reversible refractive index change, VO$_{2}$ films with footprints $<$1 $\mu$m$^{2}$ have induced record phase modulations as high as $\pi$/5 rad/$\mu$m in these VO$_{2}$-enhanced SRRs. The resulting resonance shifts of almost 3 nm are $\sim$60 times larger than their silicon-only analogues. Using these devices, we have demonstrated both thermal switching induced with a cw laser and switching with $\sim$20 ns laser pulses. Since the VO$_{2}$ phase transition occurs in $<$100 fs, harnessing this light-induced ultrafast transition could be the key to designing ultrafast OMs. [Preview Abstract] |
Thursday, November 21, 2013 11:12AM - 11:24AM |
CB.00002: High resolution ion milling of single layer graphene for electronic devices Adam Rondinone, Edward Kintzel, Allison Linn, Brad Matola Graphene is a potential replacement for silicon in microelectronics but still faces significant hurdles in implementation. The helium-ion microscope is a potential route to the fabrication of graphene-based electronic circuits. Here we will discuss the recent commissioning of a third-generation helium-ion microscope at the Center for Nanophase Materials Sciences and recent results in high-resolution ion milling of electronic structures from single-layer graphene on insulating SiO$_{\mathrm{2}}$. Scattered ions during the milling process create a damage margin around ion-milled areas, which impact electrical conductivity and place a lower limit on the width of conducting graphene structures. [Preview Abstract] |
Thursday, November 21, 2013 11:24AM - 11:36AM |
CB.00003: Low Temperature Magnetometry Measurements of the Heavy Fermion Superconductor Nd1$-x$Ce$x$CoIn5 with x $=$ 0.98, 0.95, and 0.90 Kenneth Purcell, Sarah Schwartz, Cedomir Petrovic, Kevin Storr The Nd1$-x$Ce$x$CoIn5 alloys evolve from local moment magnetism $x=$0 to heavy fermion superconductivity $x=$1, as the Nd substitution alters the level of 4f-conduction electron coupling. Superconductivity has been shown to exist in Nd concentrations between x $=$ 0 and x $=$ 0.22. We report the temperature and angular dependence of the critical field of the superconducting state of the x $=$ 0.98, 0.95, and 0.90 doping levels at temperatures ranging from 20 -- 500 mK, investigating the evolution of the phase diagram for different concentrations of Nd at these previously unexplored low temperatures. No evidence of a low temperature mixed superconducting and magnetic mixed state was observed such that as that seen in CeCoIn5. The suppression of the critical field is more dramatic than the application of pressure and was observed to be rather anisotropic in line with the higher temperature measurements. [Preview Abstract] |
Thursday, November 21, 2013 11:36AM - 11:48AM |
CB.00004: Time-Resolved Pump-Probe Spectroscopy of Bulk GaAs at 25 T Nicholas Nolan, Jeremy Curtis, Takahisa Tokumoto, Judy Cherian, Stephen McGill, David Hilton We have performed time-resolved pump-probe spectroscopy on bulk GaAs in fields as high as 25 T. The results show oscillations in the differential reflection from coherent acoustic phonons (CAP) with frequencies that are proportional to B. A magnetic field dependent shift to the CAP frequency is attributed to Zeeman splitting of the conduction and valence subbands. [Preview Abstract] |
Thursday, November 21, 2013 11:48AM - 12:00PM |
CB.00005: Split-off band infrared detectors with Graded Barriers P.K.D.D.P. Pitigala, Y.F. Lao, A.G.U. Perera, L.H. Li, E.H. Linfield, H.C. Liu One approach to develop uncooed infrared detectors is to use the light/heavy hole and the split-off band transitions to produce an enhanced response [1]. These detectors are called split-off band detectors. We demonstrate results of GaAs/AlGaAs based split-off band detector with a graded barrier replacing the traditional flat barrier. Devices are tested with graded barrier grown by digital alloying techniques [2], and graded barrier grown with gradually varying the aluminum fractions. The device with digital alloyed graded barrier had a responsivity 80 $\mu $A/W with a D*$=$1.4x10$^{8}$ Jones at 78 K under 1V bias, at peak response wavelength 2.7 $\mu$m. This is an improvement of 25 times in responsivity over the device without graded barrier, and 2 times improvement than the device with gradually increasing graded barrier. The enhancement is due to improved carrier transport by digital alloying, and the low recapture rate enabled by reduced distance to image-forces-potential peak due the barrier's gradient. The device performance could be further improved by implementing modifications to the digital alloying growth formula. [1] Jayaweera et. al., Infrared Phys. {\&} Technol., 50, 279, 2007. [2] Mathine et. al., J. Appl. Phys. 75, 4551, 1994. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700