The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Paul C Mcintyre - One of the best experts on this subject based on the ideXlab platform.
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lack of correlation between c v hysteresis and capacitance frequency dispersion in accumulation of metal gate high k n ingaas metal oxide semiconductor stacks
Journal of Applied Physics, 2018Co-Authors: Sebastian M Pazos, Paul C Mcintyre, Kechao Tang, Fernando L Aguirre, Felix PalumboAbstract:The correlation between capacitance-voltage hysteresis and accumulation capacitance frequency dispersion of metal gate/high-k/n-InGaAs metal-oxide-semiconductor stacks is experimentally assessed. Samples fabricated employing Forming Gas annealing (FGA) or substrate air exposure to obtain different densities of defects were thoroughly characterized and the results were compared with previous literature on the topic. Results indicate a lack of correlation between capacitance-voltage hysteresis and accumulation capacitance dispersion with frequency, suggesting that defects with remarkably different kinetics are involved in each phenomenon. This is assessed through the dependence of the capacitance-voltage hysteresis with DC bias and stress time, observing that permanent interface defect depassivation under bias has no effect on the hysteresis width after stress. Overall, capacitance-voltage hysteresis probes slow trapping mechanisms throughout the oxide and the bandgap, which are consistent with the negative charge trapping characteristic of the current-time curves for FGA samples at constant voltage stress. Instead, accumulation capacitance frequency dispersion probes defects with short trapping/detrapping characteristic times that can be linked to the stress induced leakage current of air exposed samples under constant DC stress. Experimental results indicate that each effect must be assessed separately due to the large difference in the kinetics of the probed defects.The correlation between capacitance-voltage hysteresis and accumulation capacitance frequency dispersion of metal gate/high-k/n-InGaAs metal-oxide-semiconductor stacks is experimentally assessed. Samples fabricated employing Forming Gas annealing (FGA) or substrate air exposure to obtain different densities of defects were thoroughly characterized and the results were compared with previous literature on the topic. Results indicate a lack of correlation between capacitance-voltage hysteresis and accumulation capacitance dispersion with frequency, suggesting that defects with remarkably different kinetics are involved in each phenomenon. This is assessed through the dependence of the capacitance-voltage hysteresis with DC bias and stress time, observing that permanent interface defect depassivation under bias has no effect on the hysteresis width after stress. Overall, capacitance-voltage hysteresis probes slow trapping mechanisms throughout the oxide and the bandgap, which are consistent with the negative...
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bias temperature stress induced hydrogen depassivation from al2o3 ingaas interface defects
Journal of Applied Physics, 2018Co-Authors: Kechao Tang, R Droopad, Paul C McintyreAbstract:We study the reliability of Al2O3/InGaAs metal-oxide-semiconductor gate stacks by investigating the effect of bias temperature stress on the charge trap density at the Al2O3/InGaAs interface and in the bulk oxide. Under extended negative biasing at 100 °C, the gate stacks display a notable increase in the interface trap density (Dit), but little change in the border trap density. This phenomenon is more prominent for samples exposed to a H2/N2 Forming Gas anneal (FGA) than for the as-deposited samples. Negative gate bias applied during 100 °C thermal stress negates the FGA-induced passivation of interface states and causes convergence of the Dit of the post-FGA and as-deposited gate stacks with increasing biasing time. This appears to be caused by hydrogen depassivation of interface traps under bias temperature stress, which is further supported by an observed hydrogen isotope effect when comparing the rate of Dit increase after annealing in hydrogenated versus deuterated Forming Gas. A N2 anneal control ...
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selective passivation of geo2 ge interface defects in atomic layer deposited high k mos structures
ACS Applied Materials & Interfaces, 2015Co-Authors: Liangliang Zhang, Kechao Tang, Yuzheng Guo, J C Woicik, J Robertson, Paul C McintyreAbstract:Effective passivation of interface defects in high-k metal oxide/Ge gate stacks is a longstanding goal of research on germanium metal-oxide-semiconductor devices. In this paper, we use photoelectron spectroscopy to probe the formation of a GeO2 interface layer between an atomic layer deposited Al2O3 gate dielectric and a Ge(100) substrate during Forming Gas anneal (FGA). Capacitance- and conductance-voltage data were used to extract the interface trap density energy distribution. These results show selective passivation of interface traps with energies in the top half of the Ge band gap under annealing conditions that produce GeO2 interface layer growth. First-principles modeling of Ge/GeO2 and Ge/GeO/GeO2 structures and calculations of the resulting partial density of states (PDOS) are in good agreement with the experiment results.
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the effect of post oxide deposition annealing on the effective work function in metal al2o3 ingaas gate stack
Applied Physics Letters, 2014Co-Authors: Roy Winter, Igor Krylov, Paul C Mcintyre, M EizenbergAbstract:The effect of post oxide deposition annealing on the effective work function in metal/Al2O3/ InGaAs gate stacks was investigated. Using a systematic method for effective work function extraction, a shift of 0.3 ± 0.1 eV was found between the effective work function of Forming Gas annealed samples and vacuum annealed samples. The electrical measurements enabled us to obtain the band alignment of the metal/Al2O3/InGaAs gate stack. This band alignment was confirmed by X-ray photoelectron spectroscopy. The measured shift in the effective work function between different annealing ambient may be attributed to indium out-diffusion during post oxide deposition annealing that is observed in Forming Gas anneal to a much larger extent than in vacuum.
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origin and passivation of fixed charge in atomic layer deposited aluminum oxide gate insulators on chemically treated ingaas substrates
Applied Physics Letters, 2010Co-Authors: Byungha Shin, Paul K Hurley, Justin R Weber, Rathnait D Long, Chris G Van De Walle, Paul C McintyreAbstract:We report experimental and theoretical studies of defects producing fixed charge within Al2O3 layers grown by atomic layer deposition (ALD) on In0.53Ga0.47As(001) substrates and the effects of hydrogen passivation of these defects. Capacitance-voltage measurements of Pt/ALD-Al2O3/n-In0.53Ga0.47As suggested the presence of positive bulk fixed charge and negative interfacial fixed charge within ALD-Al2O3. We identified oxygen and aluminum dangling bonds (DBs) as the origin of the fixed charge. First-principles calculations predicted possible passivation of both O and Al DBs, which would neutralize fixed charge, and this prediction was confirmed experimentally; postmetallization Forming Gas anneal removed most of the fixed charge in ALD-Al2O3.
Chaoling Hung - One of the best experts on this subject based on the ideXlab platform.
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merger signatures in the dynamics of star Forming Gas
The Astrophysical Journal, 2016Co-Authors: Chaoling Hung, Christopher C Hayward, H A Smith, Matthew L N Ashby, Lauranne Lanz, Juan Rafael Martinezgalarza, D B SandersAbstract:The recent advent of integral field spectrographs and millimeter interferometers has revealed the internal dynamics of many hundreds of star-Forming galaxies. Spatially resolved kinematics have been used to determine the dynamical status of star-Forming galaxies with ambiguous morphologies, and constrain the importance of galaxy interactions during the assembly of galaxies. However, measuring the importance of interactions or galaxy merger rates requires knowledge of the systematics in kinematic diagnostics and the visible time with merger indicators. We analyze the dynamics of star-Forming Gas in a set of binary merger hydrodynamic simulations with stellar mass ratios of 1:1 and 1:4. We find that the evolution of kinematic asymmetries traced by star-Forming Gas mirrors morphological asymmetries derived from mock optical images, in which both merger indicators show the largest deviation from isolated disks during strong interaction phases. Based on a series of simulations with various initial disk orientations, orbital parameters, Gas fractions, and mass ratios, we find that the merger signatures are visible for ~0.2–0.4 Gyr with kinematic merger indicators but can be approximately twice as long for equal-mass mergers of massive Gas-rich disk galaxies designed to be analogs of z ~ 2–3 submillimeter galaxies. Merger signatures are most apparent after the second passage and before the black holes coalescence, but in some cases they persist up to several hundred Myr after coalescence. About 20%–60% of the simulated galaxies are not identified as mergers during the strong interaction phase, implying that galaxies undergoing violent merging process do not necessarily exhibit highly asymmetric kinematics in their star-Forming Gas. The lack of identifiable merger signatures in this population can lead to an underestimation of merger abundances in star-Forming galaxies, and including them in samples of star-Forming disks may bias the measurements of disk properties such as intrinsic velocity dispersion.
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merger signatures in the dynamics of star Forming Gas
arXiv: Astrophysics of Galaxies, 2015Co-Authors: Chaoling Hung, Christopher C Hayward, H A Smith, Matthew L N Ashby, Lauranne Lanz, Juan Rafael Martinezgalarza, D B Sanders, Andreas ZezasAbstract:Spatially resolved kinematics have been used to determine the dynamical status of star-Forming galaxies with ambiguous morphologies, and constrain the importance of galaxy interactions during the assembly of galaxies. However, measuring the importance of interactions or galaxy merger rates requires knowledge of the systematics in kinematic diagnostics and the visible time with merger indicators. We analyze the dynamics of star-Forming Gas in a set of binary merger hydrodynamic simulations with stellar mass ratios of 1:1 and 1:4. We find that the evolution of kinematic asymmetries traced by star-Forming Gas mirrors morphological asymmetries derived from mock optical images, in which both merger indicators show the largest deviation from isolated disks during strong interaction phases. Based on a series of simulations with various initial disk orientations, orbital parameters, Gas fractions, and mass ratios, we find that the merger signatures are visible for ~0.2-0.4 Gyr with kinematic merger indicators but can be approximately twice as long for equal-mass mergers of massive Gas-rich disk galaxies designed to be analogs of z~2-3 submillimeter galaxies. Merger signatures are most apparent after the second passage and before the black holes coalescence, but in some cases they persist up to several hundred Myr after coalescence. About 20-60% of the simulated galaxies are not identified as mergers during the strong interaction phase, implying that galaxies undergoing violent merging process do not necessarily exhibit highly asymmetric kinematics in their star-Forming Gas. The lack of identifiable merger signatures in this population can lead to an underestimation of merger abundances in star-Forming galaxies, and including them in samples of star-Forming disks may bias the measurements of disk properties such as intrinsic velocity dispersion.
Sanjay K Banerjee - One of the best experts on this subject based on the ideXlab platform.
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unpinned metal gate high κ gaas capacitors fabrication and characterization
Applied Physics Letters, 2006Co-Authors: Davood Shahrjerdi, Michael M Oye, A L Holmes, Sanjay K BanerjeeAbstract:Fabrication of GaAs metal-oxide-semiconductor capacitors (MOSCAPs) with an unpinned interface is reported. The MOSCAP structure consists of a few monolayers of germanium grown in a molecular beam epitaxy (MBE) system in order to terminate an MBE-grown silicon-doped (100) GaAs layer. An ex situ HfO2 high-κ dielectric with an equivalent oxide thickness of 12A was deposited by using a dc magnetron sputtering system. A midgap interface state density (Dit) of 5×1011eV−1cm−2 was measured using the high-frequency conductance technique. A rapid thermal annealing study was performed in order to examine the integrity of the gate stack at different temperatures. In addition, a Forming Gas anneal at 400°C appears to significantly reduce the midgap Dit revealed by probing the frequency dispersion behavior of the MOSCAPs.
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electrical properties of zro2 gate dielectric on sige
Applied Physics Letters, 2000Co-Authors: T Ngai, J C Lee, R Sharma, J Fretwell, X Chen, Sanjay K BanerjeeAbstract:We report the electrical properties of a high dielectric constant (high-k) material, ZrO2, deposited directly on SiGe, without the use of a Si buffer layer or a passivation barrier. ZrO2 thin films of equivalent oxide thickness (EOT) down to 16.5 A were deposited on strained SiGe layers by reactive sputtering. Results indicate that ZrO2 films on SiGe have good interfacial properties and low leakage currents. Sintering in Forming Gas at 350 °C for 1 h could further improve the film quality. Although threshold voltage stability and dielectric dispersion become a concern for thick ZrO2 films, thin ZrO2 films of EOT less than 20 A exhibit excellent electrical properties making them a good candidate for SiGe applications.
Mordecaimark Mac Low - One of the best experts on this subject based on the ideXlab platform.
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the stellar mass spectrum from non isothermal gravoturbulent fragmentation
Astronomy and Astrophysics, 2005Co-Authors: Ralf S Klessen, Richard B Larson, Mordecaimark Mac Low, Katharina JappsenAbstract:The thermodynamic state of star-Forming Gas determines its fragmentation behavior and thus plays a crucial role in determining the stellar initial mass function (IMF). We address the issue by studying the effects of a piecewise polytropic equation of state (EOS) on the formation of stellar clusters in turbulent, self-gravitating molecular clouds using three-dimensional, smoothed particle hydrodynamics simulations. In these simulations stars form via a process we call gravoturbulent fragmentation, i.e., gravitational fragmentation of turbulent Gas. To approximate the results of published predictions of the thermal behavior of collapsing clouds, we increase the polytropic exponent γ from 0.7 to 1.1 at a critical density n c , which we estimated to be $2.5\times10^5\,\mathrm{cm^{-3}}$. The change of thermodynamic state at n c selects a characteristic mass scale for fragmentation M ch , which we relate to the peak of the observed IMF. A simple scaling argument based on the Jeans mass $M_\mathrm{J}$ at the critical density $n_\mathrm{c}$ leads to $M_{\mathrm{ch}}\propto n_{\mathrm{c}}^{-0.95}$. We perform simulations with $4.3\times10^4\,\mathrm{cm^{-3}} < n_{\mathrm{c}} < 4.3\times10^7\,\mathrm{cm^{-3}}$ to test this scaling argument. Our simulations qualitatively support this hypothesis, but we find a weaker density dependence of $M_{\mathrm{ch}} \propto n_{\mathrm{c}}^{-0.5\pm0.1}$. We also investigate the influence of additional environmental parameters on the IMF. We consider variations in the turbulent driving scheme, and consistently find $M_{\mathrm{J}}$ is decreasing with increasing $n_{\mathrm{c}}$. Our investigation generally supports the idea that the distribution of stellar masses depends mainly on the thermodynamic state of the star-Forming Gas. The thermodynamic state of interstellar Gas is a result of the balance between heating and cooling processes, which in turn are determined by fundamental atomic and molecular physics and by chemical abundances. Given the abundances, the derivation of a characteristic stellar mass can thus be based on universal quantities and constants.
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the stellar mass spectrum from non isothermal gravoturbulent fragmentation
arXiv: Astrophysics, 2004Co-Authors: Annekatharina Jappsen, Ralf S Klessen, Richard B Larson, Mordecaimark Mac LowAbstract:Identifying the processes that determine the initial mass function of stars (IMF) is a fundamental problem in star formation theory. One of the major uncertainties is the exact chemical state of the star Forming Gas and its influence on the dynamical evolution. Most simulations of star Forming clusters use an isothermal equation of state (EOS). However, theoretical predictions and observations suggest that the effective polytropic exponent gamma in the EOS varies with density. We address these issues and study the effect of a piecewise polytropic EOS on the formation of stellar clusters in turbulent, self-gravitating molecular clouds using three-dimensional, smoothed particle hydrodynamics simulations. To approximate the results of published predictions of the thermal behavior of collapsing clouds, we increase the polytropic exponent gamma from 0.7 to 1.1 at some chosen density n_c, which we vary. The change of thermodynamic state at n_c selects a characteristic mass scale for fragmentation M_ch, which we relate to the peak of the observed IMF. Our investigation generally supports the idea that the distribution of stellar masses depends mainly on the thermodynamic state of the star-Forming Gas. The thermodynamic state of interstellar Gas is a result of the balance between heating and cooling processes, which in turn are determined by fundamental atomic and molecular physics and by chemical abundances. Given the abundances, the derivation of a characteristic stellar mass can thus be based on universal quantities and constants.
Christopher C Hayward - One of the best experts on this subject based on the ideXlab platform.
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merger signatures in the dynamics of star Forming Gas
The Astrophysical Journal, 2016Co-Authors: Chaoling Hung, Christopher C Hayward, H A Smith, Matthew L N Ashby, Lauranne Lanz, Juan Rafael Martinezgalarza, D B SandersAbstract:The recent advent of integral field spectrographs and millimeter interferometers has revealed the internal dynamics of many hundreds of star-Forming galaxies. Spatially resolved kinematics have been used to determine the dynamical status of star-Forming galaxies with ambiguous morphologies, and constrain the importance of galaxy interactions during the assembly of galaxies. However, measuring the importance of interactions or galaxy merger rates requires knowledge of the systematics in kinematic diagnostics and the visible time with merger indicators. We analyze the dynamics of star-Forming Gas in a set of binary merger hydrodynamic simulations with stellar mass ratios of 1:1 and 1:4. We find that the evolution of kinematic asymmetries traced by star-Forming Gas mirrors morphological asymmetries derived from mock optical images, in which both merger indicators show the largest deviation from isolated disks during strong interaction phases. Based on a series of simulations with various initial disk orientations, orbital parameters, Gas fractions, and mass ratios, we find that the merger signatures are visible for ~0.2–0.4 Gyr with kinematic merger indicators but can be approximately twice as long for equal-mass mergers of massive Gas-rich disk galaxies designed to be analogs of z ~ 2–3 submillimeter galaxies. Merger signatures are most apparent after the second passage and before the black holes coalescence, but in some cases they persist up to several hundred Myr after coalescence. About 20%–60% of the simulated galaxies are not identified as mergers during the strong interaction phase, implying that galaxies undergoing violent merging process do not necessarily exhibit highly asymmetric kinematics in their star-Forming Gas. The lack of identifiable merger signatures in this population can lead to an underestimation of merger abundances in star-Forming galaxies, and including them in samples of star-Forming disks may bias the measurements of disk properties such as intrinsic velocity dispersion.
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merger signatures in the dynamics of star Forming Gas
arXiv: Astrophysics of Galaxies, 2015Co-Authors: Chaoling Hung, Christopher C Hayward, H A Smith, Matthew L N Ashby, Lauranne Lanz, Juan Rafael Martinezgalarza, D B Sanders, Andreas ZezasAbstract:Spatially resolved kinematics have been used to determine the dynamical status of star-Forming galaxies with ambiguous morphologies, and constrain the importance of galaxy interactions during the assembly of galaxies. However, measuring the importance of interactions or galaxy merger rates requires knowledge of the systematics in kinematic diagnostics and the visible time with merger indicators. We analyze the dynamics of star-Forming Gas in a set of binary merger hydrodynamic simulations with stellar mass ratios of 1:1 and 1:4. We find that the evolution of kinematic asymmetries traced by star-Forming Gas mirrors morphological asymmetries derived from mock optical images, in which both merger indicators show the largest deviation from isolated disks during strong interaction phases. Based on a series of simulations with various initial disk orientations, orbital parameters, Gas fractions, and mass ratios, we find that the merger signatures are visible for ~0.2-0.4 Gyr with kinematic merger indicators but can be approximately twice as long for equal-mass mergers of massive Gas-rich disk galaxies designed to be analogs of z~2-3 submillimeter galaxies. Merger signatures are most apparent after the second passage and before the black holes coalescence, but in some cases they persist up to several hundred Myr after coalescence. About 20-60% of the simulated galaxies are not identified as mergers during the strong interaction phase, implying that galaxies undergoing violent merging process do not necessarily exhibit highly asymmetric kinematics in their star-Forming Gas. The lack of identifiable merger signatures in this population can lead to an underestimation of merger abundances in star-Forming galaxies, and including them in samples of star-Forming disks may bias the measurements of disk properties such as intrinsic velocity dispersion.