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Metropolitan Government of Nashville-Davidson (balance), TN, United States

Gollub S.L.,Materials Science Program | Harl R.R.,Chemical and Biomolecular Engineering | Rogers B.R.,Chemical and Biomolecular Engineering | Walker D.G.,Mechanical Engineering
Journal of Luminescence | Year: 2014

This study investigates whether particle irradiation of yttrium borate doped with cerium(III) (YBO3:1%Ce3+) and yttrium borate doped with europium(III) (YBO3:6%Eu3+) can cause displacement damage and whether photoluminescent emission changes with the radiation dose. Although phosphors scintillate upon irradiation, of more interest in this study are the permanent changes caused by non-ionizing energy absorption, which alters the environment of the luminescent centers and thus the luminescence. Photoluminescence spectroscopy indicates that the emission intensity of both YBO3:1%Ce3+ and YBO3: 6%Eu3+ decreases with increasing proton fluence. The sensitivity of changes in the emission intensity to proton fluence is 5 times more in the europium-doped samples than in the cerium-doped samples. © 2013 Elsevier B.V. Source


Kim J.-H.,University of California at San Diego | Chen Z.C.Y.,University of California at San Diego | Kwon S.,Materials Science Program | Xiang J.,University of California at San Diego
2013 3rd Berkeley Symposium on Energy Efficient Electronic Systems, E3S 2013 - Proceedings | Year: 2013

Significant physical challenges remain for CMOS technology to decrease Ioff as transistor dimension and power supply voltages continue downscaling. However, a fundamental thermodynamic limit in the subthreshold slope SS = (∂Vg)/(∂lnId) = ln10 · k BT/q at >60 mV/dec exists at room temperature. We have designed and demonstrated the first semiconductor nanowires (NWs) and nanoelectromechanical system (NEMS) field effect transistor structure (NW-NEMFET). We have previously demonstrated 0.5 ps intrinsic delay and near ballistic operation in quantum confined semiconductor heterostructure NWFETs with diameters less than 15 nm.[1] The current design uses high performance suspended semiconductor NWs as the conduction channel, while the electrostatic pull-in of the NW towards the gate stack enables abrupt switching to the off-state leading to high frequency, low power nanoelectronics. Simulation shows that compared to planar suspended-gate FET (SGFET) design [2], NW-NEMFET allows zero SS with 1015 on-off ratio and near 1V pull-in voltage due to enhanced 3D capacitive coupling, as well as operation at very-high-frequency (VHF) and even ultra-high-frequency (UHF) due to the NW beams high aspect ratio and small dimensions. [3] © 2013 IEEE. Source


Hong K.-S.,Materials Science Program | Xu H.,Materials Science Program | Konishi H.,Materials Science Program | Li X.,University of Wisconsin - Madison
Journal of Physical Chemistry Letters | Year: 2010

We propose a mechanism, a piezoelectrochemical effect for the direct conversion of mechanical energy to chemical energy. This phenomenon is further applied for generating hydrogen and oxygen via direct water decomposition by means of as-synthesized piezoelectric ZnO microfibers and BaTiO3 microdendrites. Fibers and dendrites are vibrated with ultrasonic waves leading to a strain-induced electric charge development on their surface. With sufficient electric potential, strained piezoelectric fibers (and dendrites) in water triggered the redox reaction of water to produce hydrogen and oxygen gases. ZnO fibers under ultrasonic vibrations showed a stoichiometric ratio of H2/O2 (2:1) Initial gas production from pure water. This study provides a simple and cost-effective technology for direct water splitting that may generate hydrogen fuels by scavenging energy wastes such as noise or stray vibrations from the environment. This new discovery may have potential implications in solving the challenging energy and environmental issues that we are facing today and in the future. © 2010 American Chemical Society. Source

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