17 research outputs found

    Felony sentencing statutes

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    Title from PDF p. [1] (viewed on May 18, 2010).; "May 2008."; Harvested from the web on 5/19/1

    Teaching law through movies

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    Title from title PDF caption (viewed on May 20, 2010).; "In a slightly different form, these materials were prepared for [a] June 2007 seminar sponsored by the Ohio Supreme Court and The Columbus Dispatch."; "October 2007."; Harvested from the web on 5/20/1

    Monitoring sentencing reform survey of judges, prosecutors, & defense attorneys and code simplification

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    Title PDF p. [1] (viewed on May 18, 2010).; "January 2009."; Harvested from the web on 5/19/1

    Low-Frequency (1/<i>f</i>) Noise in Nanocrystal Field-Effect Transistors

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    We investigate the origins and magnitude of low-frequency noise in high-mobility nanocrystal field-effect transistors and show the noise is of 1/<i>f</i>-type. Sub-band gap states, in particular, those introduced by nanocrystal surfaces, have a significant influence on the 1/<i>f</i> noise. By engineering the device geometry and passivating nanocrystal surfaces, we show that in the linear and saturation regimes the 1/<i>f</i> noise obeys Hooge’s model of mobility fluctuations, consistent with transport of a high density of accumulated carriers in extended electronic states of the NC thin films. In the subthreshold regime, the Fermi energy moves deeper into the mobility gap and sub-band gap trap states give rise to a transition to noise dominated by carrier number fluctuations as described in McWhorter’s model. CdSe nanocrystal field-effect transistors have a Hooge parameter of 3 × 10<sup>–2</sup>, comparable to other solution-deposited, thin-film devices, promising high-performance, low-cost, low-noise integrated circuitry

    Solution-Based Stoichiometric Control over Charge Transport in Nanocrystalline CdSe Devices

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    Using colloidal CdSe nanowire (NW) field-effect transistors (FETs), we demonstrated the dependence of carrier transport on surface stoichiometry by chemically manipulating the atomic composition of the NW surface. A mild, room-temperature, wet-chemical process was devised to introduce cadmium, selenium, or sulfur adatoms at the surface of the NWs in completed devices. Changes in surface composition were tested for by energy dispersive spectroscopy and inductively coupled plasma-atomic emission spectroscopy and through the use of the vibrational reporter thiocyanate. We found that treatment with cadmium acetate enhances electron currents, while treatment with sodium selenide or sodium sulfide suppressed them. The efficacy of doping CdSe NWs through subsequent thermal diffusion of indium was highly dependent on the surface composition. While selenium-enriched CdSe NW FETs were characterized by little to no electron currents, when combined with indium, they yielded semimetallic devices. Sulfur-enriched, indium-doped devices also displayed dramatically enhanced electron currents, but to a lesser extent than selenium and formed FETs with desirable <i>I</i><sub>ON</sub>/<i>I</i><sub>OFF</sub> >10<sup>6</sup>. The atomic specificity of the electronic behavior with different surface chalcogens suggested indium was bound to chalcogens at the NW surface, indicating commonalities with and implications for indium-containing CdSe nanocrystal films. Low temperature measurements of indium-doped CdSe NW FETs showed no evidence of impurity scattering, further supporting the existence of an indium–chalcogen interaction at the surface rather than in the core of the NW

    Size-Dependent Biexciton Quantum Yields and Carrier Dynamics of Quasi-Two-Dimensional Core/Shell Nanoplatelets

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    Quasi-two-dimensional nanoplatelets (NPLs) possess fundamentally different excitonic properties from zero-dimensional quantum dots. We study lateral size-dependent photon emission statistics and carrier dynamics of individual NPLs using second-order photon correlation (g<sup>(2)</sup>(τ)) spectroscopy and photoluminescence (PL) intensity-dependent lifetime analysis. Room-temperature radiative lifetimes of NPLs can be derived from maximum PL intensity periods in PL time traces. It first decreases with NPL lateral size and then stays constant, deviating from the electric dipole approximation. Analysis of the PL time traces further reveals that the single exciton quantum yield in NPLs decreases with NPL lateral size and increases with protecting shell thickness, indicating the importance of surface passivation on NPL emission quality. Second-order photon correlation (g<sup>(2)</sup>(τ)) studies of single NPLs show that the biexciton quantum yield is strongly dependent on the lateral size and single exciton quantum yield of the NPLs. In large NPLs with unity single exciton quantum yield, the corresponding biexciton quantum yield can reach unity. These findings reveal that by careful growth control and core–shell material engineering, NPLs can be of great potential for light amplification and integrated quantum photonic applications

    <i>In Situ</i> Repair of High-Performance, Flexible Nanocrystal Electronics for Large-Area Fabrication and Operation in Air

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    Colloidal semiconductor nanocrystal (NC) thin films have been integrated in light-emitting diodes, solar cells, field-effect transistors (FETs), and flexible, electronic circuits. However, NC devices are typically fabricated and operated in an inert environment since the reactive surface and high surface-to-volume ratio of NC materials render them sensitive to oxygen, water, and many solvents. This sensitivity has limited device scaling and large-scale device integration achievable by conventional fabrication technologies, which generally require ambient air and wet-chemical processing. Here, we present a simple, effective route to reverse the detrimental effects of chemical and environmental exposure, by incorporating, <i>in situ</i>, a chemical agent, namely, indium metal, which is thermally triggered to diffuse and repair the damage. Taking advantage of the recovery process, CdSe NC FETs are processed in air, patterned using the solvents of lithography, and packaged by atomic layer deposition to form large-area and flexible high-performance NC devices that operate stably in air

    Bandlike Transport in Strongly Coupled and Doped Quantum Dot Solids: A Route to High-Performance Thin-Film Electronics

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    We report bandlike transport in solution-deposited, CdSe QD thin-films with room temperature field-effect mobilities for electrons of 27 cm<sup>2</sup>/(V s). A concomitant shift and broadening in the QD solid optical absorption compared to that of dispersed samples is consistent with electron delocalization and measured electron mobilities. Annealing indium contacts allows for thermal diffusion and doping of the QD thin-films, shifting the Fermi energy, filling traps, and providing access to the bands. Temperature-dependent measurements show bandlike transport to 220 K on a SiO<sub>2</sub> gate insulator that is extended to 140 K by reducing the interface trap density using an Al<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> gate insulator. The use of compact ligands and doping provides a pathway to high performance, solution-deposited QD electronics and optoelectronics
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