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Full-Text Articles in Engineering
Feature-Based Calibration Of Distributed Smart Stereo Camera Networks, Aaron Mavrinac, Xiang Chen, Kemal Tepe
Feature-Based Calibration Of Distributed Smart Stereo Camera Networks, Aaron Mavrinac, Xiang Chen, Kemal Tepe
Electrical and Computer Engineering Publications
A distributed smart camera network is a collective of vision-capable devices with enough processing power to execute algorithms for collaborative vision tasks. A true 3D sensing network applies to a broad range of applications, and local stereo vision capabilities at each node offer the potential for a particularly robust implementation. A novel spatial calibration method for such a network is presented, which obtains pose estimates suitable for collaborative 3D vision in a distributed fashion using two stages of registration on robust 3D features. The method is initially described in a geometrical sense, then presented in a practical implementation using existing …
Single Spin Toffoli-Fredkin Logic Gate, Amit Ranjan Trivedi, S. Bandyopadhyay
Single Spin Toffoli-Fredkin Logic Gate, Amit Ranjan Trivedi, S. Bandyopadhyay
Electrical and Computer Engineering Publications
The Toffoli–Fredkin (TF) gate is a universal reversible logic gate capable of performing logic operations without dissipating energy. Here, we show that a linear array of three quantum dots, each hosting a single electron, can realize the TF gate, if we encode logic bits in the spin polarization of the electrons and allow nearest neighbor exchange coupling. The dynamics of the TF gate is realized by selectively driving spin resonances in the coupled spin system with an acmagnetic field. The conditions for gate operation are established, and an estimate of the switching speed and gate error are provided.
Field Emission From Self-Assembled Arrays Of Lanthanum Monosulfide Nanoprotrusions, V. Semet, Vu Thien Binh, M. Cahay, K. Garre, S. Fairchild, L. Grazulis, J. W. Fraser, D. J. Lockwood, S. Pramanik, B. Kanchibotla, Supriyo Bandyopadhyay
Field Emission From Self-Assembled Arrays Of Lanthanum Monosulfide Nanoprotrusions, V. Semet, Vu Thien Binh, M. Cahay, K. Garre, S. Fairchild, L. Grazulis, J. W. Fraser, D. J. Lockwood, S. Pramanik, B. Kanchibotla, Supriyo Bandyopadhyay
Electrical and Computer Engineering Publications
The field emission properties of LaS nanoprotrusions called nanodomes, formed by pulsed laser deposition on porous anodic alumina films, have been analyzed with scanning anode field emission microscopy. The voltage necessary to produce a given field emission current is 3.5 times less for nanodomes than for thin films. Assuming the same work function for LaS thin films and nanoprotrusions, that is, 1 eV, a field enhancement factor of 5.8 is extracted for the nanodome emitters from Fowler-Nordheim plots of the field emission data. This correlates well with the aspect ratio of the tallest nanodomes observed in atomic force micrograph measurements.
Reduction Of Efficiency Droop In Ingan Light Emitting Diodes By Coupled Quantum Wells, Xianfeng Ni, Qian Fan, Ryoko Shimada, Ü. Özgür, Hadis Morkoç
Reduction Of Efficiency Droop In Ingan Light Emitting Diodes By Coupled Quantum Wells, Xianfeng Ni, Qian Fan, Ryoko Shimada, Ü. Özgür, Hadis Morkoç
Electrical and Computer Engineering Publications
Light emitting diodes(LEDs) based on InGaN suffer from efficiency droop at current injection levels as low as 50 A cm−2. We investigated multiple quantum wellInGaNLEDs with varying InGaN barrier thicknesses (3–12 nm) emitting at ∼400–410 nm to investigate the effect of hole mass and also to find out possible solutions to prevent the efficiency droop. In LEDs with electron blocking layers, when we reduced the InGaN barriers from 12 to 3 nm, the current density for the peak or saturation of external quantum efficiency increased from 200 to 1100 A cm−2 under pulsed injection conditions, which eliminates the heating effects …
Large Pyroelectric Effect In Undoped Epitaxial Pb(Zr,Ti)O3 Thin Films On Srtio3 Substrates, Bo Xiao, Vitaliy Avrutin, Huiyong Liu, Ü. Özgür, Hadis Morkoç, Changzhi Lu
Large Pyroelectric Effect In Undoped Epitaxial Pb(Zr,Ti)O3 Thin Films On Srtio3 Substrates, Bo Xiao, Vitaliy Avrutin, Huiyong Liu, Ü. Özgür, Hadis Morkoç, Changzhi Lu
Electrical and Computer Engineering Publications
We have studied pyroelectric and ferroelectric properties of Pb(Zr,Ti)O3thin filmsgrown epitaxially on SrTiO3(001) substrates by rf magnetron sputtering. The pyroelectric coefficient was measured in the temperature range from 280 to 370 K using the Byer–Roundy method. Values as high as 48 nC/cm2 K have been obtained at 300 K. The PZTthin films exhibited a remanent polarization of 45–58 μC/cm2. The improved pyroelectric coefficient was attributed to a high crystalline quality of the films, as revealed by x-ray diffraction that showed only (001)-oriented perovskitePZT phase and a ω-rocking curve full width at half maximum value as low as 4.2 arc min …
On The Efficiency Droop In Ingan Multiple Quantum Well Blue Light Emitting Diodes And Its Reduction With P-Doped Quantum Well Barriers, Jinqiao Xie, Xianfeng Ni, Qian Fan, Ryoko Shimada, Ü. Özgür, Hadis Morkoç
On The Efficiency Droop In Ingan Multiple Quantum Well Blue Light Emitting Diodes And Its Reduction With P-Doped Quantum Well Barriers, Jinqiao Xie, Xianfeng Ni, Qian Fan, Ryoko Shimada, Ü. Özgür, Hadis Morkoç
Electrical and Computer Engineering Publications
Multiple quantum well(MQW) InGaN light emitting diodes with and without electron blocking layers, with relatively small and large barriers, with and without p-type doping in the MQW region emitting at ∼420nm were used to determine the genesis of efficiency droop observed at injection levels of approximately ⩾50A/cm2. Pulsed electroluminescence measurements, to avoid heating effects, revealed that the efficiency peak occurs at ∼900A/cm2current density for the Mg-doped barrier, near 550A/cm2 for the lightly dopedn-GaN injection layer, meant to bring the electron injection level closer to that of holes, and below 220A/cm2 for the undoped InGaN barrier cases. For samples with GaN …
Cavity Polaritons In Zno-Based Hybrid Microcavities, R. Shimada, J. Xie, Vitaliy Avrutin, Ü. Özgür, Hadis Morkoç
Cavity Polaritons In Zno-Based Hybrid Microcavities, R. Shimada, J. Xie, Vitaliy Avrutin, Ü. Özgür, Hadis Morkoç
Electrical and Computer Engineering Publications
Among wide-bandgap semiconductors, ZnO is a very attractive candidate for blue-ultraviolet lasers operating at room temperature owing to its large exciton binding energy and oscillator strength. Especially, ZnO-based microcavity structures are most conducive for polariton lasing at room temperature. We report the observation of cavitypolaritons in bulk ZnO-based hybrid microcavities at room temperature. The bulk ZnO-based hybrid microcavities are composed of 29 pairs of Al0.5Ga0.5N∕GaNdistributed Bragg reflector (DBR) at the bottom of the λ-thick cavity layer and eight pairs of SiO2∕Si3N4 DBR as the top mirror, which provided cavityQvalues of ∼100. Anticrossing behavior between the lower and upper polariton branches …
Self-Assembled Deoxyguanosine Based Molecular Electronic Device On Gan Substrates, H. Liddar, J. Li, A. Neogi, P. B. Neogi, A. Sarkar, S. Cho, Hadis Morkoç
Self-Assembled Deoxyguanosine Based Molecular Electronic Device On Gan Substrates, H. Liddar, J. Li, A. Neogi, P. B. Neogi, A. Sarkar, S. Cho, Hadis Morkoç
Electrical and Computer Engineering Publications
Nanoscale hybrid molecular organic photodetectors based on self-assembled guanosine molecules conjugated to wide-bandgap GaNsemiconductors has been realized in the ultraviolet wavelength regime. Metal-semiconductor-metal based photodetector is fabricated using ordering of modified guanosine based semiconductor nanowires which exhibit I-Vcharacteristics with high current response and higher rectification ratio compared to Si based hybrid photodetectors. Photocurrent response of a two-terminal device shows the typical characteristics of a semiconductorphotodiode with a cutoff wavelength at ∼325nm. The I-Vcharacteristics have been elucidated using the induced polarization properties of self-assembled guanosine semiconductor.
Transverse Spin Relaxation Time In Organic Molecules, B. Kanchibotla, S. Pramanik, S. Bandyopadhyay, M. Cahay
Transverse Spin Relaxation Time In Organic Molecules, B. Kanchibotla, S. Pramanik, S. Bandyopadhyay, M. Cahay
Electrical and Computer Engineering Publications
We report a measurement of the ensemble-averaged transverse spin relaxation time (T∗2) in bulk and few molecules of the organic semiconductor tris-(8-hydroxyquinolinolato aluminum) or Alq3. This system exhibits two characteristic T∗2 times: the longer of which is temperature independent and the shorter is temperature dependent, indicating that the latter is most likely limited by spin-phonon interaction. Based on the measured data, we infer that the single-particle T2 time is probably long enough to meet Knill’s criterion for fault-tolerant quantum computing even at room temperature. Alq3 is also an optically active organic, and we propose a simple …
Magnetic Field Effects On Spin Texturing In A Quantum Wire With Rashba Spin-Orbit Interaction, P. Upadhyaya, S. Pramanik, S. Bandyopadhyay, M. Cahay
Magnetic Field Effects On Spin Texturing In A Quantum Wire With Rashba Spin-Orbit Interaction, P. Upadhyaya, S. Pramanik, S. Bandyopadhyay, M. Cahay
Electrical and Computer Engineering Publications
A quantum wire with strong Rashba spin-orbit interaction is known to exhibit spatial modulation of spin density along its width owing to coupling between subbands caused by the Rashba interaction. This is known as spin texturing. Here, we show that a transverse external magnetic field introduces additional complex features in spin texturing, some of which reflect the intricate details of the underlying energy dispersion relations of the spin-split subbands. One particularly intriguing feature is a 90° phase shift between the spatial modulations of two orthogonal components of the spin density, which is observed at moderate field strengths and when only …
Optical Transitions In A Quantum Wire With Spin-Orbit Interaction And Its Applications In Terahertz Electronics: Beyond Zeroth-Order Theory, P. Upadhyaya, S. Pramanik, S. Bandyopadhyay
Optical Transitions In A Quantum Wire With Spin-Orbit Interaction And Its Applications In Terahertz Electronics: Beyond Zeroth-Order Theory, P. Upadhyaya, S. Pramanik, S. Bandyopadhyay
Electrical and Computer Engineering Publications
We calculate the terahertz absorption spectra associated with intersubband transitions in a semiconductor quantum wire in the presence of spin-orbit interaction and a transverse magnetic field. The frequencies and intensities of the absorption peaks are found to depend strongly on the spin-orbit coupling strength, which can be varied with an external electric field. This feature can be exploited to realize reconfigurable multispectral terahertz detectors and amplitude and/or frequency modulators. We also show that electric dipole transitions between spin-split levels in the same subband (which are normally deemed forbidden) become allowed because of spin texturing effects. The absorption associated with these …
The Inequality Of Charge And Spin Diffusion Coefficients, Sandipan Pramanik, Supriyo Bandyopadhyay, Marc Cahay
The Inequality Of Charge And Spin Diffusion Coefficients, Sandipan Pramanik, Supriyo Bandyopadhyay, Marc Cahay
Electrical and Computer Engineering Publications
Since spin and charge are both carried by electrons (or holes) in a solid, it is natural to assume that charge and spin diffusion coefficients will be the same. Drift-diffusion models of spin transport typically assume so. Here, we show analytically that the two diffusion coefficients can be vastly different in quantum wires. Although we do not consider quantum wells or bulk systems, it is likely that the two coefficients will be different in those systems as well. Thus, it is important to distinguish between them in transportmodels, particularly those applied to quantum wire based devices.
Current Versus Voltage Characteristics Of Gan/Algan/Gan Double Heterostructures With Varying Algan Thickness And Composition Under Hydrostatic Pressure, I. P. Steinke, P. P. Ruden, X. Ni, H. Morkoç, K.-A. Son
Current Versus Voltage Characteristics Of Gan/Algan/Gan Double Heterostructures With Varying Algan Thickness And Composition Under Hydrostatic Pressure, I. P. Steinke, P. P. Ruden, X. Ni, H. Morkoç, K.-A. Son
Electrical and Computer Engineering Publications
We have studied current versus voltage characteristics of n-GaN∕u-AlGaN∕n-GaN double heterostructure devices under hydrostatic pressure up to 500MPa. Devices were grown on c-plane sapphire substrates by organometallic vapor phase epitaxy using epitaxial layer overgrowth. The effect of AlGaN layer thickness and composition on the pressure sensitivity was investigated. For a fixed applied bias, we found that the current decreases approximately linearly in magnitude with increasing hydrostatic pressure over the range of voltages and pressures applied. The decrease in current magnitude can be attributed to piezoelectric effects and is consistent with model calculations. The polarizationcharge densities at the GaN∕AlGaN interfaces change …