Thermoreflectance Imaging Of Sub 100 Ns Pulsed Cooling In High-Speed Thermoelectric Microcoolers,
2013
Birck Nanotechnology Center, Purdue University; University of California - Santa Cruz
Thermoreflectance Imaging Of Sub 100 Ns Pulsed Cooling In High-Speed Thermoelectric Microcoolers, Bjorn Vermeersch, Je-Hyeong Bahk, James Christofferson, Ali Shakouri
Birck and NCN Publications
Miniaturized thin film thermoelectric coolers have received considerable attention as potential means to locally address hot spots in microprocessors. Given the highly dynamic workload in complex integrated circuits, the need arises for a thorough understanding of the high-speed thermal behavior of microcoolers. Although some prior work on transient Peltier cooling in pulsed operation is available, these studies mostly focus on theoretical modeling and typically deal with relatively large modules with time constants well into the millisecond range. In this paper, we present an extensive experimental characterization of 30 x 30 mu m(2) high-speed coplanar SiGe superlattice microcoolers subjected to 300 …
Shape Memory Metamaterials With Tunable Thermo-Mechanical Response Via Hetero-Epitaxial Integration: A Molecular Dynamics Study,
2013
Birck Nanotechnology Center, Purdue University
Shape Memory Metamaterials With Tunable Thermo-Mechanical Response Via Hetero-Epitaxial Integration: A Molecular Dynamics Study, Karthik Guda Vishnu, Alejandro Strachan
Birck and NCN Publications
We show that nanoscale epitaxial superlattices (SLs) can be used to engineer the energy landscape that governs the martensitic transformation in shape memory alloys and tune their thermo-mechanical response. We demonstrate the approach using large-scale molecular dynamics simulations of a SL material consisting of alternate layers of a shape memory Ni-rich NiAl alloy and NiAl B2 alloy. The non-martensitic NiAl alloy was chosen to reduce the energy barrier that separates the martensite and austenite phases of the SL and its incorporation leads to a reduction in the thermal hysteresis of the transition. This is a desirable feature in applications involving …
Effects Of Forming Gas Anneal On Ultrathin Ingaas Nanowire Metal-Oxide-Semiconductor Field-Effect Transistors,
2013
Birck Nanotechnology Center, Purdue University
Effects Of Forming Gas Anneal On Ultrathin Ingaas Nanowire Metal-Oxide-Semiconductor Field-Effect Transistors, Mengwei Si, Jiangjiang Gu, Xinwei Wang, Jiayi Shao, Xuefei Li, Michael J. Manfra, Roy G. Gordon, Peide D. Ye
Birck and NCN Publications
InGaAs gate-all-around metal-oxide-semiconductor field-effect transistors (MOSFETs) with 6 nm nanowire thickness have been experimentally demonstrated at sub-80 nm channel length. The effects of forming gas anneal (FGA) on the performance of these devices have been systematically studied. The 30min 400 degrees C FGA (4% H-2/96% N-2) is found to improve the quality of the Al2O3/InGaAs interface, resulting in a subthreshold slope reduction over 20mV/dec (from 117mV/dec in average to 93mV/dec). Moreover, the improvement of interface quality also has positive impact on the on-state device performance. A scaling metrics study has been carried out for FGA treated devices with channel lengths …
Laser Direct Writing Of Silicon Field Effect Transistor Sensors,
2013
Birck Nanotechnology Center, Purdue University
Laser Direct Writing Of Silicon Field Effect Transistor Sensors, Woongsik Nam, James I. Mitchell, Chookiat Tansarawiput, Minghao Qi, Xianfan Xu
Birck and NCN Publications
We demonstrate a single step technique to fabricate silicon wires for field effect transistor sensors. Boron-doped silicon wires are fabricated using laser direct writing in combination with chemical vapor deposition, which has the advantages of precise control of position, orientation, and length, and in situ doping. The silicon wires can be fabricated to have very rough surfaces by controlling laser operation parameters, and thus, have large surface areas, enabling high sensitivity for sensing. Highly sensitive pH sensing is demonstrated. We expect our method can be expanded to the fabrication of various sensing devices beyond chemical sensors. (C) 2013 American Institute …
Deuterium Uptake In Magnetic-Fusion Devices With Lithium-Conditioned Carbon Walls,
2013
University of Tennessee - Knoxville; Oak Ridge National Laboratory
Deuterium Uptake In Magnetic-Fusion Devices With Lithium-Conditioned Carbon Walls, P. S. Krstic, Jean Paul Allain, C. N. Taylor, J. Dadras, S. Maeda, K. Morokuma, J. Jakowski, A. Allouche, C. H. Skinner
Birck and NCN Publications
Lithium wall conditioning has lowered hydrogenic recycling and dramatically improved plasma performance in many magnetic-fusion devices. In this Letter, we report quantum-classical atomistic simulations and laboratory experiments that elucidate the roles of lithium and oxygen in the uptake of hydrogen in amorphous carbon. Surprisingly, we show that lithium creates a high oxygen concentration on a carbon surface when bombarded by deuterium. Furthermore, surface oxygen, rather than lithium, plays the key role in trapping hydrogen. DOI: 10.1103/PhysRevLett.110.105001
Thermal Transport In Sige Superlattice Thin Films And Nanowires: Effects Of Specimen And Periodic Lengths,
2013
Purdue University
Thermal Transport In Sige Superlattice Thin Films And Nanowires: Effects Of Specimen And Periodic Lengths, Keng-Hua Lin, Alejandro Strachan
Birck and NCN Publications
We compute the thermal conductivity of superlattice (SL) thin films and nanowires for various SL periods and total specimen lengths using nonequilibrium molecular dynamics. Both types of materials exhibit similar behaviors with respect to SL period but the thermal conductivity of the thin films exhibits a significantly higher sensitivity to the specimen length. Notably, the thermal conductivity of SL thin films is smaller than those of the corresponding nanowires for specimen lengths below approximately 35 nm. These results arise from the complex dependence of the conductivities of the interfaces and the SL components on the specimen size and period. These …
A Computational Study Of The Thermoelectric Performance Of Ultrathin Bi2te3 Films,
2013
Birck Nanotechnology Center, Purdue University
A Computational Study Of The Thermoelectric Performance Of Ultrathin Bi2te3 Films, Jesse Maassen, Mark S. Lundstrom
Birck and NCN Publications
The ballistic thermoelectric performance of ultrathin films of Bi2Te3, ranging in thickness from 1 to 6 quintuple layers, is analyzed using density functional theory combined with the Landauer approach. Our results show that the thinnest film, corresponding to a single quintuple layer, has an intrinsic advantage originating from the particular shape of its valence band, leading to a large power factor and figure-of-merit exceeding bulk Bi2Te3. The interaction between the top and bottom topological surface states is key. The thinnest film yields a six-fold increase in power factor compared to bulk. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794534]
Study Of The Growth And Switching Kinetics On Ferroelectric Nanocrystals Of Copolymer Vinylidene Fluoride And Trifluoroethylene On An Atomic Force Microscope,
2013
Institute of Crystallography, Russian Academy of Science, Moscow
Study Of The Growth And Switching Kinetics On Ferroelectric Nanocrystals Of Copolymer Vinylidene Fluoride And Trifluoroethylene On An Atomic Force Microscope, R. V. Gaynutdinov, O. A. Lysova, A. L. Tolstikhina, V. M. Fridkin, S. G. Yudin, Stephen Ducharme
Stephen Ducharme Publications
The growth of nanocrystals obtained from Langmuir-Blodgett films of ferroelectric copolymer consisting of 70% vinylidene fluoride and 30% trifluoroethylene has been investigated by atomic force microscopy (AFM). The radius and concentration of nanocrystals are found to depend on the annealing time of the film. A model for nanocrystal growth is proposed which yields adequate time dependences for nanocrystal size parameters. The switching kinetics of individual ferroelectric nanocrystals with an average diameter of 100–200 nm and a height of 15–20 nm has been investigated in the piezoelectric response mode. It is shown that the switching of nanocrystals has an activation character.
Limitations Of The High-Low C-V Technique For Mos Interfaces With Large Time Constant Dispersion,
2013
Birck Nanotechnology Center, Purdue University
Limitations Of The High-Low C-V Technique For Mos Interfaces With Large Time Constant Dispersion, Ashish Verma Penumatcha, Steven Swandono, James A. Cooper
Birck and NCN Publications
We discuss the limitations of the high-low CV technique in evaluating the interface trap density (D-TT) in MOS samples with a large time constant dispersion, as occurs in silicon carbide (SiC). We show that the high-low technique can seriously underestimate D-IT for samples with large time constant dispersion, even if elevated temperatures are used to extend the range of validity.
Combination And Applications Of Time-Resolved Surface Plasmon Resonance Spectroscopy And Electrochemical Methods,
2013
State Key Laboratory of Electroanalytical Chemistry, Engineering Laboratory for Modern A nalytical Techniques, Changchun Institute of A pplied Chemistry, Changchun 130022, China;
Combination And Applications Of Time-Resolved Surface Plasmon Resonance Spectroscopy And Electrochemical Methods, Yu Bao, Yan Mao, Wei Wang, Zheng-Gang Li, Li Niu
Journal of Electrochemistry
Electrochemical-surface plasmon resonance (EC-SPR) technique, developed in recent years, is a new technology which combines time-resolved surface plasmon resonance spectroscopy and electrochemical methods. Surface plasmon resonance (SPR) is a physical phenomenon generated by optical coupling using a metallic thin film and is very sensitive to optical analysis. The principles of SPR and EC-SPR are briefly introduced and the applications of the combination of SPR spectroscopy with electrochemical techniques are reviewed in this paper. This new technology has been widely used in such research areas as reaction dynamics, biochemical sensors, electrode/electrolyte interfaces, kinetic parameters and bimolecular interactions.
An In Situ Ftir Spectroelectrochemical Study On Methanol Oxidation At Pt-Mo2C/Gc Catalyst,
2013
State Key Laboratory of Optoelectronic Materials and Technologies, Key Laboratory ofLow-carbon Chemistry&: Energy Conservation of Guangdong Province, Sehool of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China
An In Situ Ftir Spectroelectrochemical Study On Methanol Oxidation At Pt-Mo2C/Gc Catalyst, Hai-Ping Huang, Xi-Yu Yao, Pei-Kang Shen
Journal of Electrochemistry
A 40% Pt on Mo2C/GC catalyst has been prepared by ion exchange method. The mechanism of methanol electrooxidation on Pt-Mo2C/GC and commercial Pt/C catalysts in acidic media was studied by cyclic voltammetry, XRD measurements and in-situ Fourier transform infrared spectroelectrochemistry. The results revealed that the Pt nanoparticles were uniformly dispersed on Mo2C/GC with an average particle size of 3 nm. The cyclic voltammetric and chronopotentiometric experiments indicated that Pt-Mo2C/GC catalyst exhibited a better performance for methanol oxidation than that of Pt/C in acid solution. A negative shift over 90 mV of the …
Applications Of Ellipsometry In The Investigations Of Electrode-Solution Interface,
2013
School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400044, China;
Applications Of Ellipsometry In The Investigations Of Electrode-Solution Interface, Jing-Lei Lei, Liang-Liu Wu, Ling-Jie Li, Sheng-Mao Wu, Sheng-Tao Zhang
Journal of Electrochemistry
Ellipsometry is an optical technique with high-sensitivity to quantitatively obtain surface/interface properties such as thickness andrefractive index by analyzing the changes in polarized light reflected from the surface/interface. Its noncontacting and nondestructivenature makes it possible to acquire thein situreal-time information of the change at the surface/interface. Therefore, ellipsometry has been used widely in the electrochemical investigations. In this paper, based on the brief introduction of the measurementprinciple of ellipsometry, the current progress and the future trends of ellipsometry in electrochemistry arediscussed. The applications of ellipsometry in the fields of conversion and storage of electrochemical energy, electrochemistry ofmaterials science,electroanalysisand bioelectrochemistry are …
Sodium Carbonate Catalyzed Photoelectrochemical Water Splitting Over Tio2 Nanotubes Photoanode,
2013
Department of Chemistry, Qufu Normal University, Qufu 273165, Shandong, China;
Sodium Carbonate Catalyzed Photoelectrochemical Water Splitting Over Tio2 Nanotubes Photoanode, De-Sheng Kong, Jing Wang, Xue-Di Zhang, Xi Zhao, Chao Wang, Yuan-Yuan Feng, Wen-Juan Li
Journal of Electrochemistry
Surface recombination of the photogenerated electron-hole pairs at semiconductor/electrolyte interface is one of the most essential reasons responsible for lowering photoconversion efficiency (Φ) of light to chemical energy for photoelectrochemical (PEC) water splitting reaction. In this paper, the catalytic effect of sodium carbonate on the oxygen evolution reaction (OER) over TiO2 nanotubes photoanode during PEC water splitting was investigated by performing photocurrent and ac impedance measurements. It was demonstrated that the addiction of 1 mmol•L-1 Na2CO3 in 0.5 mol•L-1 NaClO4 electrolyte can effectively improve the charge transfer properties for the photogenerated holes across …
High-Resolution Dynamic Atomic Force Microscopy In Liquids With Different Feedback Architectures,
2013
University of Bristol
High-Resolution Dynamic Atomic Force Microscopy In Liquids With Different Feedback Architectures, John Melcher, David Martinez-Martin, Miriam Jaafar, Julio Gomez-Herrero, Arvind Raman
Birck and NCN Publications
The recent achievement of atomic resolution with dynamic atomic force microscopy (dAFM) [Fukuma et al., Appl. Phys. Lett. 2005, 87, 034101], where quality factors of the oscillating probe are inherently low, challenges some accepted beliefs concerning sensitivity and resolution in dAFM imaging modes. Through analysis and experiment we study the performance metrics for high-resolution imaging with dAFM in liquid media with amplitude modulation (AM), frequency modulation (FM) and drive-amplitude modulation (DAM) imaging modes. We find that while the quality factors of dAFM probes may deviate by several orders of magnitude between vacuum and liquid media, their sensitivity to tip-sample forces …
Cross-Plane Thermal Properties Of Transition Metal Dichalcogenides,
2013
University of Dayton; US Air Force Research Laboratory
Cross-Plane Thermal Properties Of Transition Metal Dichalcogenides, C. Muratore, V. Varshney, J. J. Gengler, J. J. Hu, J. E. Bultman, T. M. Smith, P. J. Shamberger, Bo Qiu, Xiulin Ruan, A. K. Roy, A. A. Voevodin
Birck and NCN Publications
In this work, we explore the thermal properties of hexagonal transition metal dichalcogenide compounds with different average atomic masses but equivalent microstructures. Thermal conductivity values of sputtered thin films were compared to bulk crystals. The comparison revealed a > 10 fold reduction in thin film thermal conductivity. Structural analysis of the films revealed a turbostratic structure with domain sizes on the order of 5-10 nm. Estimates of phonon scattering lengths at domain boundaries based on computationally derived group velocities were consistent with the observed film microstructure, and accounted for the reduction in thermal conductivity compared to values for bulk crystals. (C) …
Interfacial Thermal Conductance Limit And Thermal Rectification Across Vertical Carbon Nanotube/Graphene Nanoribbon-Silicon Interfaces,
2013
Purdue University
Interfacial Thermal Conductance Limit And Thermal Rectification Across Vertical Carbon Nanotube/Graphene Nanoribbon-Silicon Interfaces, Ajit K. Vallabhaneni, Bo Qiu, Jiuning Hu, Yong P. Chen, Ajit K. Roy, Xiulin Ruan
Birck and NCN Publications
Various models were previously used to predict interfacial thermal conductance of vertical carbon nanotube (CNT)-silicon interfaces, but the predicted values were several orders of magnitude off the experimental data. In this work, we show that the CNT filling fraction (the ratio of contact area to the surface area of the substrate) is the key to remedy this discrepancy. Using molecular dynamics, we have identified an upper limit of thermal interface conductance for C-Si interface which is around 1.25GW/m(2)K, corresponding to a 100% filling fraction of carbon nanotube or graphene nanoribbon on substrate. By extrapolating to low filling fraction (similar to …
Unidirectional Spaser In Symmetry-Broken Plasmonic Core-Shell Nanocavity,
2013
Birck Nanotechnology Center, Purdue University; Kyoto University
Unidirectional Spaser In Symmetry-Broken Plasmonic Core-Shell Nanocavity, Xiangeng Meng, Urcan Guler, Alexander V. Kildishev, Koji Fujita, Katsuhisa Tanaka, Vladimir M. Shalaev
Birck and NCN Publications
The spaser, a quantum amplifier of surface plasmons by stimulated emission of radiation, is recognized as a coherent light source capable of confining optical fields at subwavelength scale. The control over the directionality of spasing has not been addressed so far, especially for a single-particle spasing nanocavity where optical feedback is solely provided by a plasmon resonance. In this work we numerically examine an asymmetric spaser - a resonant system comprising a dielectric core capped by a metal semishell. The proposed spaser emits unidirectionally along the axis of the semishell; this directionality depends neither on the incident polarization nor on …
Strong Heavy-To-Light Hole Intersubband Absorption In The Valence Band Of Carbon-Doped Gaas/Alas Superlattices,
2013
Purdue University
Strong Heavy-To-Light Hole Intersubband Absorption In The Valence Band Of Carbon-Doped Gaas/Alas Superlattices, M. I. Hossain, Z. Ikonic, J. Watson, J. Shao, P. Harrison, Michael J. Manfra, O. Malis
Birck and NCN Publications
We report strong mid-infrared absorption of in-plane polarized light due to heavy-to-light hole intersubband transitions in the valence band of C-doped GaAs quantum wells with AlAs barriers. The transition energies are well reproduced by theoretical calculations including layer inter-diffusion. The inter-diffusion length was estimated to be 8 +/- 2 angstrom, a value that is consistent with electron microscopy measurements. These results highlight the importance of modeling the nanoscale structure of the semiconductors for accurately reproducing intra-band transition energies of heavy carriers such as the holes. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4790305]
Optical Down-Conversion In Doped Znse:Tb3+ Nanocrystals,
2013
University of South Carolina - Columbia
Optical Down-Conversion In Doped Znse:Tb3+ Nanocrystals, Sandip Das, K. C. Mandal
Faculty Publications
No abstract provided.
Optoelectronic Measurement Of X-Ray Synchrotron Pulses: A Proof Of Concept Demonstration,
2013
Purdue University
Optoelectronic Measurement Of X-Ray Synchrotron Pulses: A Proof Of Concept Demonstration, Stephen M. Durbin, Aamer Mahmood, Marc W. Caffee, Sergei Savikhin, Eric M. Dufresne, Haidan Wen, Yuelin Li
Birck and NCN Publications
Optoelectronic detection using photoconductive coplanar stripline devices has been applied to measuring the time profile of x-ray synchrotron pulses, a proof of concept demonstration that may lead to improved time-resolved x-ray studies. Laser sampling of current vs time delay between 12 keV x-ray and 800 nm laser pulses reveal the similar to 50 ps x-ray pulse width convoluted with the similar to 200 ps lifetime of the conduction band carriers. For GaAs implanted with 8 MeV protons, a time profile closer to the x-ray pulse width is observed. The protons create defects over the entire depth sampled by the x-rays, …
