113 research outputs found
Fabrication and subband gap optical properties of silicon supersaturated with chalcogens by ion implantation and pulsed laser melting
Topographically flat, single crystal silicon supersaturated with the chalcogens S, Se, and Te was prepared by ion implantation followed by pulsed laser melting and rapid solidification. The influences of the number of laser shots on the atomic and carrier concentration-depth profiles were measured with secondary ion mass spectrometry and spreading resistance profiling, respectively. We found good agreement between the atomic concentration-depth profiles obtained from experiments and a one-dimensional model for plane-front melting, solidification, liquid-phase diffusion, with kinetic solute trapping, and surface evaporation. Broadband subband gap absorption is exhibited by all dopants over a wavelength range from 1 to 2.5 microns. The absorption did not change appreciably with increasing number of laser shots, despite a measurable loss of chalcogen and of electronic carriers after each shot.One
of the authors M.T. acknowledges the financial support of
the Fulbright Program. This research was supported in part
by the U.S. Army ARDEC under Contract No. W15QKN-07-
P-0092
Analysis of a consumer survey on plug-in hybrid electric vehicles
Plug-in Hybrid Electric Vehicles (PHEVs) show potential to reduce greenhouse gas (GHG) emissions, increase fuel efficiency, and offer driving ranges that are not limited by battery capacity. However, these benefits will not be realized if consumers do not adopt this new technology. Several agent-based models have been developed to model potential market penetration of PHEVs, but gaps in the available data limit the usefulness of these models. To address this, we administered a survey to 1000 stated US residents, using Amazon Mechanical Turk, to better understand factors influencing the potential for PHEV market penetration. Our analysis of the survey results reveals quantitative patterns and correlations that extend the existing literature. For example, respondents who felt most strongly about reducing US transportation energy consumption and cutting greenhouse gas emissions had, respectively, 71 and 44 times greater odds of saying they would consider purchasing a compact PHEV than those who felt least strongly about these issues. However, even the most inclined to consider a compact PHEV were not generally willing to pay more than a few thousand US dollars extra for the sticker price. Consistent with prior research, we found that financial and battery-related concerns remain major obstacles to widespread PHEV market penetration. We discuss how our results help to inform agent-based models of PHEV market penetration, governmental policies, and manufacturer pricing and marketing strategies to promote consumer adoption of PHEVs. © 2014 The Authors
Photocarrier lifetime and transport in silicon supersaturated with sulfur
Doping of silicon-on-insulator layers with sulfur to concentrations far above equilibrium by ion implantation and pulsed laser melting can result in large concentration gradients. Photocarriers generated in and near the impurity gradient can separate into different coplanar transport layers, leading to enhanced photocarrier lifetimes in thin silicon-on-insulator films. The depth from which holes escape the heavily doped region places a lower limit on the minority carrier mobility-lifetime product of 10⁻⁸ cm²/V for heavily sulfur dopedsilicon. We conclude that the cross-section for recombination through S impurities at this concentration is significantly reduced relative to isolated impurities.Research at Rensselaer was supported by the Army
Research Office under Contract No. W911NF0910470 and
by the NSF REU program at Rensselaer. Research at Harvard
was supported by US Army ARDEC under Contract
No. W15QKN-07-P-0092. D.R. was supported in part by a
National Defense Science and Engineering Graduate fellowship
Supersaturating silicon with transition metals by ion implantation and pulsed laser melting
We investigate the possibility of creating an intermediate band semiconductor by supersaturating Si with a range of transition metals (Au, Co, Cr, Cu, Fe, Pd, Pt, W, and Zn) using ion implantation followed by pulsed laser melting (PLM). Structural characterization shows evidence of either surface segregation or cellular breakdown in all transition metals investigated, preventing the formation of high supersaturations. However, concentration-depth profiling reveals that regions of Si supersaturated with Au and Zn are formed below the regions of cellular breakdown. Fits to the concentration-depth profile are used to estimate the diffusive speeds, v D, of Au and Zn, and put lower bounds on v D of the other metals ranging from 10² to 10⁴ m/s. Knowledge of v D is used to tailor the irradiation conditions and synthesize single-crystal Si supersaturated with 10¹⁹ Au/cm³ without cellular breakdown. Values of v D are compared to those for other elements in Si. Two independent thermophysical properties, the solute diffusivity at the melting temperature, D s(T m), and the equilibrium partition coefficient, k e, are shown to simultaneously affect v D. We demonstrate a correlation between v D and the ratio D s(T m)/k e ⁰·⁶⁷, which is exhibited for Group III, IV, and V solutes but not for the transition metals investigated. Nevertheless, comparison with experimental results suggests that D s(T m)/k e ⁰·⁶⁷ might serve as a metric for evaluating the potential to supersaturate Si with transition metals by PLM.Research at Harvard was supported by The U.S. Army
Research Office under contracts W911NF-12-1-0196 and
W911NF-09-1-0118. M.T.W. and T.B.’s work was supported
by the U.S. Army Research Laboratory and the U.S.
Army Research Office under Grant No. W911NF-10-1-0442,
and the National Science Foundation (NSF) Faculty Early
Career Development Program ECCS-1150878 (to T.B.).
M.J.S., J.T.S., M.T.W., T.B., and S.G. acknowledge a generous
gift from the Chesonis Family Foundation and support in
part by the National Science Foundation (NSF) and the
Department of Energy (DOE) under NSF CA No. EEC-
1041895. S.C. and J.S.W.’s work was supported by The
Australian Research Council. J.M. was supported by a
National Research Council Research Associateship
Supersaturating silicon with transition metals by ion implantation and pulsed laser melting
We investigate the possibility of creating an intermediate band semiconductor by supersaturating Si with a range of transition metals (Au, Co, Cr, Cu, Fe, Pd, Pt, W, and Zn) using ion implantation followed by pulsed laser melting (PLM). Structural characterization shows evidence of either surface segregation or cellular breakdown in all transition metals investigated, preventing the formation of high supersaturations. However, concentration-depth profiling reveals that regions of Si supersaturated with Au and Zn are formed below the regions of cellular breakdown. Fits to the concentration-depth profile are used to estimate the diffusive speeds, v [subscript D], of Au and Zn, and put lower bounds on v [subscript D] of the other metals ranging from 10[superscript 2] to 10[superscript 4] m/s. Knowledge of v [subscript D] is used to tailor the irradiation conditions and synthesize single-crystal Si supersaturated with 10[superscript 19] Au/cm[superscript 3] without cellular breakdown. Values of v [subscript D] are compared to those for other elements in Si. Two independent thermophysical properties, the solute diffusivity at the melting temperature, D [subscript s](T [subscript m]), and the equilibrium partition coefficient, k [subscript e], are shown to simultaneously affect v [subscript D]. We demonstrate a correlation between v [subscript D] and the ratio D [subscript s](T [subscript m])/k [subscript e] [superscript 0.67], which is exhibited for Group III, IV, and V solutes but not for the transition metals investigated. Nevertheless, comparison with experimental results suggests that D [subscript s](T [subscript m])/k [subscript e] [superscript 0.67] might serve as a metric for evaluating the potential to supersaturate Si with transition metals by PLM.National Science Foundation (U.S.) (Faculty Early Career Development Program ECCS-1150878)Chesonis Family FoundationUnited States. Army Research Laboratory (United States. Army Research Office Grant W911NF-10-1-0442)National Science Foundation (U.S.) (United States. Dept. of Energy NSF CA EEC-1041895
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Emergence of Very Broad Infrared Absorption Band by Hyperdoping of Silicon with Chalcogens
We report the near through mid-infrared (MIR) optical absorption spectra, over the range 0.05–1.3 eV, of monocrystalline silicon layers hyperdoped with chalcogen atoms synthesized by ion implantation followed by pulsed laser melting. A broad mid-infrared optical absorption band emerges, peaking near 0.5 eV for sulfur and selenium and 0.3 eV for tellurium hyperdoped samples. Its strength and width increase with impurity concentration. Its strength decreases markedly with subsequent thermal annealing. The emergence of a broad MIR absorption band is consistent with the formation of an impurity band from isolated deep donor levels as the concentration of chalcogen atoms in metastable local configurations increases.Engineering and Applied Science
Xyce parallel electronic simulator reference guide, version 6.0.
This document is a reference guide to the Xyce Parallel Electronic Simulator, and is a companion document to the Xyce Users' Guide [1] . The focus of this document is (to the extent possible) exhaustively list device parameters, solver options, parser options, and other usage details of Xyce. This document is not intended to be a tutorial. Users who are new to circuit simulation are better served by the Xyce Users' Guide [1]
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