Engineering Commons^™

Nanoscale Contacts Between Semiconducting Nanowires And Metallic Graphenes, Seongmin Kim, David B. Janes, Sung-Yool Choi, Sanghyun Ju

Birck and NCN Publications

Metal–semiconductor (M–S) junctions are important components in many semiconductor devices, and there is growing interest in realizing high quality M–S contacts that are optically transparent. In this paper, we present our investigations into the characteristics of M–S junction in a semiconducting ZnO nanowire that was directly grown on a multilayer graphene film (MGF). The synthesized nanowires were fabricated into two-terminal devices with MGF as one contact and Al as the other contact. By comparison with devices employing Al contacts at both ends, the nanowire resistivity and specific contact resistivity of the MGF–nanowire contact can be extracted. The extracted specific contact …

A Comparative Study Of Three Sorting Techniques In Performing Cognitive Tasks On A Tabular Representation, Inkyoung Hur, Sung-Hee Kim, Anya Samak, Ji Soo Yi

Hive Lab Publications Archive

We investigated the impacts of three sorting techniques on various cognitive tasks performed on a tabular representation. The tasks under study were a multi-attribute object selection task and selected low-level analytic tasks. Three sorting techniques, including sorting by a column (Typical Sort: TS), sorting by all columns simultaneously (SimulSort: SS), and sorting by all columns with faithful vertical locations (ParallelTable: PT), were compared with a static table without the sorting feature (Baseline: B). An incentivized controlled laboratory study with 80 participants and a preliminary eye-tracker study were conducted to better understand the strengths and weaknesses of the four different approaches. …

Near Field Enhancement In Silver Nanoantenna-Superlens Systems, Zhengtong Liu, Erping Li, Vladimir M. Shalaev, Alexander V. Kildishev

Birck and NCN Publications

We demonstrate near field enhancement generation in silver nanoantenna-superlens systems via numerical modeling. Using near-field interference and global optimization algorithms, we can design nanoantenna-superlens systems with mismatched permittivities, whose performance can match those with matched permittivities. The systems studied here may find broad applications in the fields of sensing, such as field-enhanced fluorescence and surface-enhanced Raman scattering, and the methodology used here can be applied to the designing and optimization of other devices, such as two-dimensional near field focusing lens. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4732793]

A Thermophone On Porous Polymeric Substrate, Girish Chitnis, Albert Kim, Seung Hyun Song, A. M. Jessop, J. S. Bolton, Babak Ziaie

Birck and NCN Publications

In this Letter, we present a simple, low-temperature method for fabricating a wide-band (>80 kHz) thermo-acoustic sound generator on a porous polymeric substrate. We were able to achieve up to 80 dB of sound pressure level with an input power of 0.511 W. No significant surface temperature increase was observed in the device even at an input power level of 2.5 W. Wide-band ultrasonic performance, simplicity of structure, and scalability of the fabrication process make this device suitable for many ranging and imaging applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737005]

Cooling Of Photoexcited Carriers In Graphene By Internal And Substrate Phonons, Tony Low, Vasili Perebeinos, Raseong Kim, Marcus Freitag, Phaedon Avouris

Birck and NCN Publications

We investigate the energy relaxation of hot carriers produced by photoexcitation of graphene through coupling to both intrinsic and remote ( substrate) surface polar phonons using the Boltzmann equation approach. We find that the energy relaxation of hot photocarriers in graphene on commonly used polar substrates, under most conditions, is dominated by remote surface polar phonons. We also calculate key characteristics of the energy relaxation process, such as the transient cooling time and steady-state carrier temperatures and photocarrier densities, which determine the thermoelectric and photovoltaic photoresponse, respectively. Substrate engineering can be a promising route to efficient optoelectronic devices driven by …

A Comparative Study Of User Preferences Of A Personalized Academic Website, Dipti U. Desai

Purdue Polytechnic Masters Theses

ABSTRACT

There has been a growing concern over the enrollment by American students into Science, Technology, Engineering and Mathematic (STEM) fields of study. Following globalization there is a direct competition for jobs in the United States with lower-wage workers around the globe and the US, thereby, is on the verge of losing its global technological competitiveness (Committee on Prospering in the Global Economy of the 21st Century: An Agenda for American Science and Technology, National Academy of Sciences, National Academy of Engineering, Institute of Medicine, 2007). Governmental as well as non-profit organizations are constantly searching for ideas, programs and initiatives …

Does The Low Hole Transport Mass In <110> And <111> Si Nanowires Lead To Mobility Enhancements At High Field And Stress: A Self-Consistent Tight-Binding Study, R. L. Kotlyar, T. D. Linton, R. Rios, M. D. Giles, S. M. Cea, K. J. Kuhn, Michael Povolotskyi, Tillmann Kubis, Gerhard Klimeck

Birck and NCN Publications

The hole surface roughness and phonon limited mobility in the silicon h100i, h110i, and h111i square nanowires under the technologically important conditions of applied gate bias and stress are studied with the self-consistent Poisson-sp3d5s*-SO tight-binding bandstructure method. Under an applied gate field, the hole carriers in a wire undergo a volume to surface inversion transition diminishing the positive effects of the high h110i and h111i valence band nonparabolicities, which are known to lead to the large gains of the phonon limited mobility at a zero field in narrow wires. Nonetheless, the hole mobility in the unstressed wires down to the …

Repeatable Low-Temperature Negative-Differential Resistance From Al0.18ga0.82n/Gan Resonant Tunneling Diodes Grown By Molecular-Beam Epitaxy On Free-Standing Gan Substrates, D. Li, L. Tang, C. Edmunds, J. Shao, G. Gardner, Michael J. Manfra, O. Malis

Birck and NCN Publications

Low-aluminum composition AlGaN/GaN double-barrier resonant tunneling structures were grown by plasma-assisted molecular-beam-epitaxy on free-standing c-plane GaN substrates grown by hydride-vapor phase epitaxy. Clear, exactly reproducible, negative-differential resistance signatures were observed from 4 x 4 mu m(2) devices at 1.5V and 1.7V at 77K. The relatively small value of the maximum peak-to-valley ratio (1.03) and the area dependence of the electrical characteristics suggest that charge transport is affected by leakage paths through dislocations. However, the reproducibility of the data indicates that electrical traps play no significant role in the charge transport in resonant tunneling diodes grown by molecular-beam-epitaxy under Ga-rich conditions …

Single-Molecule Tools Elucidate H2a.Z Nucleosome Composition, Jiji Chen, Andrew Miller, Ann L. Kirchmaier, Joseph M.K. Irudayaraj

Birck and NCN Publications

Although distinct epigenetic marks correlate with different chromatin states, how they are integrated within single nucleosomes to generate combinatorial signals remains largely unknown. We report the successful implementation of single molecule tools constituting fluorescence correlation spectroscopy (FCS), pulse interleave excitation-based Forster resonance energy transfer (PIE-FRET) and fluorescence lifetime imaging-based FRET (FLIM-FRET) to elucidate the composition of single nucleosomes containing histone variant H2A.Z (Htz1p in yeast) in vitro and in vivo. We demonstrate that yeast nucleosomes containing Htz1p are primarily composed of H4 K12ac and H3 K4me3 but not H3 K36me3 and that these patterns are conserved in mammalian cells. Quantification …

Analysis Of Thermal Conductance Of Ballistic Point Contacts, Changwook Jeong, Mark S. Lundstrom

Birck and NCN Publications

Substantial reduction of thermal conductance (K-ph) was recently reported for air gap heterostructures (AGHs) in which two bulk layers were connected by low-density nanopillars. We analyze K-ph using a full phonon dispersion and including important phonon scattering. We find a transition from ballistic at low temperatures to quasi-ballistic transport near room temperature and explain the slow roll-off in K-ph that occurs near room temperature. We show that the density of nanopillars deduced from the analysis depends strongly on the phonon dispersion assumed. Our model provides a good agreement with experiment that will be necessary to design AGHs for thermoelectric applications. …

The Effects Of Diameter And Chirality On The Thermal Transport In Free-Standing And Supported Carbon-Nanotubes, Bo Qiu, Yan Wang, Xiulin Ruan, Qing Zhao

Birck and NCN Publications

We use molecular dynamics simulations to explore the lattice thermal transport in free-standing and supported single-wall carbon-nanotube (SWCNT) in comparison to that in graphene nanoribbon and graphene sheet. For free-standing SWCNT, the lattice thermal conductivity increases with diameter and approaches that of graphene, partly due to the curvature. Supported SWCNT thermal conductivity is reduced by 34%-41% compared to the free-standing case, which is less than that in supported graphene. Also, it shows an evident chirality dependence by varying about 10%, which we attribute to chirality-dependent interfacial phonon scattering. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4725194]

On The Best Bandstructure For Thermoelectric Performance: A Landauer Perspective, Changwook Jeong, Raseong Kim, Mark S. Lundstrom

Birck and NCN Publications

The question of what bandstructure produces the best thermoelectric device performance is revisited from a Landauer perspective. We find that a delta-function transport distribution function (TDF) results in operation at the Mahan-Sofo upper limit for the thermoelectric figure-of-merit, ZT. We show, however, the Mahan-Sofo upper limit itself depends on the bandwidth (BW) of the dispersion, and therefore, a finite BW dispersion produces a higher ZT when the lattice thermal conductivity is finite. Including a realistic model for scattering profoundly changes the results. Instead of a narrow band, we find that a broad BW is best. The prospects of increasing ZT …

Parametric Noise Squeezing And Parametric Resonance Of Microcantilevers In Air And Liquid Environments, Gyan Prakash, Arvind Raman, Jeff F. Rhoads, Ronald G. Reifenberger

Birck and NCN Publications

In this work, parametric noise squeezing and parametric resonance are realized through the use of an electronic feedback circuit to excite a microcantilever with a signal proportional to the product of the microcantilever's displacement and a harmonic signal. The cantilever's displacement is monitored using an optical lever technique. By adjusting the gain of an amplifier in the feedback circuit, regimes of parametric noise squeezing/amplification and the principal and secondary parametric resonances of fundamental and higher order eigenmodes can be easily accessed. The exceptionally symmetric amplitude response of the microcantilever in the narrow frequency bandwidth is traced to a nonlinear parametric …

Documenting The Construction Of A Plain Concrete Bridge Deck And An Internally Cured Bridge Deck, Carmelo Di Bella, John Schlitter, Neal Carboneau, Jason Weiss

Indiana Local Technical Assistance Program (LTAP) Technical Reports

Durable and long lasting concrete is important, especially for bridge decks, which are susceptible to premature cracking and corrosion of the reinforcing steel. To increase the durability of the concrete and its service life, many transportation agencies use high-strength concretes. However, high-strength concretes often have problems with early age cracking due to shrinkage. These cracks can then open a path for chloride ions (found in road salts) to reach the reinforcing steel. The results of this research, which compared bridge installations on two structures in Monroe County, Indiana, confirm that internally cured concrete presents a better alternative to traditional plain …

Flexure-Fet Biosensor To Break The Fundamental Sensitivity Limits Of Nanobiosensors Using Nonlinear Electromechanical Coupling, Ankit Jain, Pradeep Nair, Muhammad A. Alam

Birck and NCN Publications

In this article, we propose a Flexure-FET (flexure sensitive field effect transistor) ultrasensitive biosensor that utilizes the nonlinear electromechanical coupling to overcome the fundamental sensitivity limits of classical electrical or mechanical nanoscale biosensors. The stiffness of the suspended gate of Flexure-FET changes with the capture of the target biomolecules, and the corresponding change in the gate shape or deflection is reflected in the drain current of FET. The Flexure-FET is configured to operate such that the gate is biased near pull-in instability, and the FET-channel is biased in the subthreshold regime. In this coupled nonlinear operating mode, the sensitivity of …

Quantized Hall Effect And Shubnikov-De Haas Oscillations In Highly Doped Bi2se3: Evidence For Layered Transport Of Bulk Carriers, Helin Cao, Jifa Tian, Ireneusz Miotkowski, Tian Shen, Jiuning Hu, Shan Qiao, Yong P. Chen

Birck and NCN Publications

Bi2Se3 is an important semiconductor thermoelectric material and a prototype topological insulator. Here we report observation of Shubnikov-de Hass oscillations accompanied by quantized Hall resistances (R-xy) in highly doped n-type Bi2Se3 with bulk carrier concentrations of few 10(19) cm(-3). Measurements under tilted magnetic fields show that the magnetotransport is 2D-like, where only the c-axis component of the magnetic field controls the Landau level formation. The quantized step size in 1/R-xy is found to scale with the sample thickness, and average similar to e(2)/h per quintuple layer. We show that the observed magnetotransport features do not come from the sample surface, …

Amorphous Ni/Al Nanoscale Laminates As High-Energy Intermolecular Reactive Composites, Karthik Guda Vishnu, Mathew Cherukara, Hojin Kim, Alejandro Strachan

Birck and NCN Publications

We use molecular dynamics simulations to explore the potential use of amorphous metals in intermolecular reactive composites. Our simulations show that amorphous Ni/Al nanolaminates lead to an increase in temperature of up to 260 K over their crystalline counterparts; this increase corresponds to over 20% of the heat of fusion and can be explained in terms of the amorphization energy. The reactions are diffusion controlled and crystallization is observed in laminates with relatively long periods where high temperatures are experienced for sufficiently long times prior to intermixing; the effect of this process on the energetics and time involved in the …

Two-Temperature Nonequilibrium Molecular Dynamics Simulation Of Thermal Transport Across Metal-Nonmetal Interfaces, Yan Wang, Xiulin Ruan, Ajit K. Roy

Birck and NCN Publications

We have used a two-temperature nonequilibrium molecular dynamics method for predicting interfacial thermal resistance across metal-nonmetal interfaces. This method is an extension of the conventional nonequilibrium molecular dynamics for the dielectric-dielectric interface, where a temperature bias is imposed and the heat current is derived. We have included the electron degree of freedom for the interfacial thermal transport problem by treating the electron-phonon coupling with the two-temperature model. The method is demonstrated on two model systems, that is, silicon-copper interface and carbon-nanotube-copper interface. Temperature nonequilibrium between electrons and phonons in the metal side is quantitatively predicted, and a temperature drop across …

Reduction Of Spectral Phonon Relaxation Times From Suspended To Supported Graphene, Bo Qiu, Xiulin Ruan

Birck and NCN Publications

We have performed molecular dynamics simulations with phonon spectral analysis to predict the mode-wise phonon relaxation times (RT) of suspended and supported graphene at room temperature, and the findings are consistent with recent optical measurements. For acoustic phonons, RTs reduce from up to 50 ps to less than 5 ps when graphene is put on silicon dioxide substrate. Similarly, optical phonon RTs reduce by half when supported. Stronger interfacial bonding is found to result in more RT reduction. Our results provide a fundamental understanding at the spectral phonon property level for the observed thermal conductivity reduction in supported graphene. (C) …

Bivariate Drought Analysis Using Entropy Theory, Zengchao Hao, Vijay P. Singh

2011 Symposium on Data-Driven Approaches to Droughts

Drought duration and severity are two properties that are usually needed for drought analysis. To characterize the correlation between the two drought properties, a bivariate distribution is needed. A new method based on entropy theory is proposed for constructing the bivariate distribution that is capable of modeling drought duration and severity with different marginal distributions. Parameters of the joint distribution are estimated with Newton’s method. Monthly streamflow data from Brazos River at Waco, Texas, are employed to illustrate the application of the proposed method to model drought duration and severity for drought analysis.

Properties Of Metal-Graphene Contacts, Joachim Knoch, Zhihong Chen, Joerg Appenzeller

Birck and NCN Publications

We present a study on the metal-graphene contact properties. Utilizing a dual-gate field-effect transistor device, an energetic separation between the Fermi level and the Dirac point in the contact areas can be adjusted deliberately by applying an appropriate front-gate voltage that acts only on the channel. This front-gate voltage is compensated by an opposite large-area back-gate voltage, thereby mimicking the metal induced doping effect. A back-gate voltage sweep enables identifying two distinct resistance peaks-a result of the combined impact of the graphene cones in the contact and in the channel region. Comparing our experimental data with simulations allows extracting the …

Electric Field Tuning Of Spin Splitting In A Quantum Dot Coupled To A Semimagnetic Quantum Dot, Yuli Lyanda-Geller, T.L. Reinecke, G. Bacher

Birck and NCN Publications

We develop an approach for tuning the spin splitting and g-factor of a quantum dot by coupling it to semi-magnetic quantum dot and tuning the electric field. We show that spin splittings and g-factors of the states of a non-magnetic quantum dot coupled to semi-magnetic quantum dot can be enhanced orders of magnitude. Evaluations are made for coupled CdTe/CdMnTe quantum dots. These effects are caused by electric field control of repulsion of spin sublevels in the non-magnetic dot due to tunnel coupling of quantum dots. Electric field control of spin splittings in quantum dots is of potential interest in connection …

Thermal Conductivity Of Bulk And Thin-Film Silicon: A Landauer Approach, Changwook Jeong, Supriyo Datta, Mark S. Lundstrom

Birck and NCN Publications

The question of what fraction of the total heat flow is transported by phonons with different mean-free-paths is addressed using a Landauer approach with a full dispersion description of phonons to evaluate the thermal conductivities of bulk and thin film silicon. For bulk Si, the results reproduce those of a recent molecular dynamic treatment showing that about 50% of the heat conduction is carried by phonons with a mean-free-path greater than about 1 mu m. For the in-plane thermal conductivity of thin Si films, we find that about 50% of the heat is carried by phonons with mean-free-paths shorter than …

Spectroscopy Of A Deterministic Single-Donor Device In Silicon, M. Fuechsle, J. A. Miwa, S. Mahapatra, H. Ryu, S. Lee, O. Warschkow, L. C. L. Hollenberg, G. Klimeck, M. Y. Simmons

Birck and NCN Publications

We present a single electron transistor (SET) based on an individual phosphorus dopant atom in an epitaxial silicon environment. Using scanning tunneling microscope (STM) hydrogen lithography, the single impurity is deterministically placed with a spatial accuracy of ±1 lattice site within a donor-based transport device. Low temperature transport measurements confirm the presence of the single donor and show that the donor charge state can be precisely controlled via gate voltages. We observe a charging energy that is remarkably similar to the value expected for isolated P donors in bulk silicon, which is in sharp contrast to previous experiments on single-dopant …

Assessing The Engineering Performance Of Affordable Net-Zero Energy Housing, Jordan P. Wallpe

Purdue Polytechnic Masters Theses

The purpose of this research was to evaluate affordable technologies that are capable of providing attractive, cost-effective energy savings to the housing industry. The research did so by investigating the 2011 Solar Decathlon competition, with additional insight from the Purdue INhome. Insight from the Purdue INhome verified the importance of using a three step design process to design a net-zero energy building. In addition, energy consumption values of the INhome were used to compare and contrast different systems used in other houses.

Evaluation of unbiased competition contests gave a better understanding of how a house can realistically reach net-zero. Upon …

Broadband Purcell Effect: Radiative Decay Engineering With Metamaterials, Zubin Jacob, Igor I. Smolyaninov, Evgenii E. Narimanov

Birck and NCN Publications

We show that metamaterials with hyperbolic dispersion support a large number of electromagnetic states that can couple to quantum emitters leading to a broadband Purcell effect. The proposed approach of radiative decay engineering, useful for applications such as single photon sources, fluorescence imaging, biosensing, and single molecule detection, also opens up the possibility of using hyperbolic metamaterials to probe the spontaneous emission properties of atoms and artificial atoms such as quantum dots. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4710548]

Defining Industry Expectations And Misconceptions Of Art And Technology Co-Creativity, Vanessa C. Brasfield

Department of Computer Graphics Technology Degree Theses

The primary purpose of this study was to establish whether or not students and industry professionals share the same views about what students should be learning in animation education, what skills are necessary, and whether or not students graduating with a bachelor’s degree would be adequately prepared for an entry level position. To establish where misconceptions lie, surveys were issued to three groups: undergraduate students, post-graduate students, and industry professionals. These surveys were then analyzed using paired t-test for validation and question relevance, and ANOVA models to establish whether or not groups shared viewpoints. These data established significance within the …

Sustainable Purchasing Practices: An Investigation Into Current Industry Awareness And Practice., Francis X. Palisi

Purdue Polytechnic Masters Theses

This research study illustrates the growing importance of sustainable purchasing practices and answers two important questions: what is the current awareness of U.S. organizations on sustainable purchasing practices with regards to evaluating, selecting, and retaining suppliers and to what extent are these practices being implemented? The research conducted is based upon an in-depth literature review of green purchasing and sustainability initiatives. With an ever increasing global economy with no intention of slowing down it is ever important to look towards sustainability practices and the biggest impact organizations can make is in the purchasing department. The researcher begins by explaining their …

Improving Manufacturing Processes Through Energy Monitoring, Andrew Grzelak

Purdue Polytechnic Masters Theses

Energy efficiency and sustainability are very popular topics in the current field of manufacturing. With the increase in use of automation technology as well as the recent growth in the area of energy management, there is much focus on the overall improvement of manufacturing processes. For this research a project was completed to create a system that could improve both process efficiency as well as decrease energy consumption. By taking a look at the machine level energy consumption of an automated piece of manufacturing equipment, by eliminating waste in process, both energy efficiency and operational efficiency can be improved.

Using …

Network Resilience In Disasters: An Interdisciplinary, International Perspective, Satish Ukkusuri

Changing World Conference

No abstract provided.