Materials Science Program

Thompson's Station, TN, United States

Materials Science Program

Thompson's Station, TN, United States
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Rae D.F.,Materials Science Program | Cotts E.J.,Binghamton University State University of New York
JOM | Year: 2011

The influence of processing on filledpolymeric bondline microstructure and thermal performance was examined. Cu/thermal interface material/ Cu trilayers were assembled with a viscously applied, adhesive thermal interface material with Ag filler particles. It was found that decreasing the squeeze rate used for bondline formation from 10 to 0.1 μm/s resulted in a change in the microstructure from fairly homogeneous (homogeneous at 50 μm length scales and above) to one with marked segregation of many filler particles into highly compacted structures spanning the bondline thickness. A three-fold increase in effective thermal conductivity was correlated with this microstructure change. Significant changes in microstructure resulted when the compressive force (300N) used to form the bondline was removed before the bondline structure was stabilized by a cure operation and a four fold increase in the thermal resistance of such bondlines was observed.

Liu Y.,Materials Science Program | Yin L.,Advanced Research Corp. | Cotts E.J.,Materials Science Program | Cotts E.J.,Binghamton University State University of New York
Journal of the Electrochemical Society | Year: 2010

In many electronic devices, a time-dependent degradation of the drop/impact reliability of solder joints with electrodeposited Cu has been an issue to date. This problem has been associated with a sporadic void formation in the interfacial Cu 3 Sn intermetallic compound and has also been found to aggravate with the introduction of Pb-free solders. Recently, incorporation of impurities into the electroplated Cu layer has been demonstrated to promote the voiding in Cu/solder joints. The aim of this work is to quantitatively study the role of key Cu plating parameters in the impurity incorporation process. The reported experiments emphasize the impact of plating temperature on the voiding propensity of galvanostatically deposited Cu layers. Also, a comprehensive analysis combining the findings of this study and current-voltage results for Cu deposition at constant temperature establishes a clear correlation between overpotential changes driven by plating rate or temperature and trends in the voiding propensity of accordingly deposited Cu layers. Based on this correlation, the ranges of overpotentials where either "void-prone" or "void-free" Cu could be deposited are clearly identified in two acidic Cu plating solutions containing different additive combinations. The proposed analysis enables further prediction and control of the voiding in solder joints with electrodeposited Cu layers. © 2009 The Electrochemical Society.

Sackmann E.K.,Materials Science Program | Sackmann E.K.,Wisconsin Institute for Medical Research | Sackmann E.K.,University of Wisconsin - Madison | Berthier E.,Wisconsin Institute for Medical Research | And 16 more authors.
Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012 | Year: 2012

Improvements in neutrophil cliemotaxis assays have enabled significant advances in understanding the mechanisms of neutrophil recruitment, however current methods are still limiting due to high sample volume requirements, low experimental throughput, or complex assay protocols. We report a microfluidic technology that performs neutrophil sorting and cliemotaxis on-chip within minutes using nanoliters of whole blood and only requires a micropipette to operate. The platform was adapted to incorporate an endothelial cell monolayer: perform cliemotaxis on mouse neutrophils; and human neutrophil cliemotaxis in 3D. Finally, the platform was employed in a clinical setting to diagnose asthma in human patients.

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.

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.

Gollub S.L.,Materials Science Program | Harl R.R.,Chemical and Biomolecular Engineering | Rogers B.R.,Chemical and Biomolecular 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.

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