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Transition metal oxides with insulator-metal transitions (IMTs) are uniquely suited for volatile memristor devices that mimic the spiking of biological neurons. Unlike most non-volatile memristors, which often operate via ion migration into filaments, volatile devices utilize a reversible phase change that returns to a ground state in the absence of applied stimulus. In these devices, Joule heating triggers the IMT and changes the bulk resistivity rather than influencing conduction through defects, as in previous studies. This volatile resistive switching behavior has previous been leveraged in niobium and vanadium oxides, but not in rare-earth nickelates, despite their tunable transition temperatures. This study demonstrates an electrically driven IMT in the prototypical rare-earth nickelate, NdNiO3, in large area devices. While previous work examining the electrically-driven IMT in NdNiO3 suggests defect-dominated conduction, this study shows clear s-type negative differential resistance (NDR) consistent with temperature-dependent resistivity measurements. The NDR peak-to-valley voltage scales linearly with temperature as expected for conductivity pathways dominated by bulk IMT behavior. Unlike other transition metal oxides, which are modeled using the insulator-metal phase fraction as the internal state variable, a thermoelectric model with temperature as the internal state variable is found to more accurately describe the current–voltage characteristic of NdNiO3 volatile memristors. Overall, we report the synthesis, fabrication, and characterization of NdNiO3 volatile memristors with resistivity dominated by bulk-like IMT behavior which is scalable and not dependent upon oxygen vacancy migration or defect mediated conduction pathways. [ABSTRACT FROM AUTHOR]

The low-frequency power spectrum has been measured for ErAs:InAlGaAs diodes and shows at least a ten-times reduction of 1/f noise compared to traditional Al Schottky diodes on the same semiconductor material. These junctions are grown by molecular beam epitaxy, preventing oxidation and other contamination at the junction. The major noise source for these devices is attributed to the sidewalls and not the junction itself. Low-frequency oscillations have also been observed and associated with a deep trap level estimated to be similar to 200 meV below the conduction band edge by the comparison of diodes with different InAlGaAs compositions and confirmed by deep level transient spectroscopy. This deep level could be associated to erbium incorporation in the depletion region.

We demonstrate a molecular beam epitaxy growth technique to create intentionally textured interfaces between semimetallic ErAs and GaAs that result in interface orientations that are different from the substrate. To grow the textured interfaces, ErAs is deposited on (100) GaAs and islands form in an island growth mode. Enough GaAs is then deposited to fill the space between islands with semiconductor. More ErAs is deposited on the ErAs/GaAs surface and the new ErAs islands are thought to nucleate on the exposed top surface of the partially covered islands. The process is repeated to "stack" the islands. By quadratically increasing the amount of ErAs deposited in each repetition, the islands form into cones/pyramids that coalesce into a complete film with an intentionally roughened interface. Compared to a smooth interface between ErAs and GaAs, the Schottky barrier height between textured ErAs and n-GaAs can be reduced from similar to 0.81 to similar to 0.52 eV, and the Schottky barrier height between ErAs and p-GaAs can be increased from similar to 0.38 to similar to 0.63 eV. (c) 2006 American Vacuum Society.

In contrast to traditional metal-semiconductor (i.e., Schottky) junctions, molecular beam epitaxy (MBE)-grown ErAs:InAlGaAs heterojunctions have recently been shown to provide highly "engineerable" electrical rectification characteristics through the tuning of the Schottky barrier height, while maintaining the very low specific capacitance. This letter reports an approximate 10x improvement in the low-frequency noise performance by using MBE-grown ErAs as the Schottky contact instead of evaporated aluminum. The low-frequency noise power spectrum of ErAs devices has been observed to have a 1/f(1.0) frequency dependence. Constant-current bias-dependent measurements have shown a 1.8 power law dependence of the noise spectral density on dc current. (c) 2006 American Institute of Physics.

We demonstrate subpicosecond photocarrier lifetimes at 1.55 mum in GaSb/ErSb nanoparticle superlattices grown by molecular beam epitaxy. Pump-probe measurements were made with a 1.55 mum mode-locked laser in transmission geometry to determine the photocarrier lifetime. The lifetime is found to be dependent on the size of the ErSb particles, amount of ErSb, and the distance between layers of particles. Through manipulation of these three parameters the photocarrier lifetime can be tuned down to less than 300 fs, the temporal limit of our experiment. (C) 2004 American Institute of Physics.

We report the first experimental results for noise-equivalent power (NEP) and noise-equivalent temperature difference (NETD) of single-crystal ErAs:InAlGaAs, zero-bias rectifier diodes coupled to free space quasi-optically in the THz region. At a frequency of 639 GHz, an optical NEP of 4.0×10−12W/Hz1/2 is measured with the rectifier coupled to a quasi-plane-wave coherent source through a single-turn square spiral antenna. With a broadband thermal (hot water) source, an NETD of 120 mK is measured from the same device. Antenna radiation patterns at 100 GHz and 639 GHz are also presented. [ABSTRACT FROM AUTHOR]

We demonstrate subpicosecond photocarrier lifetimes at 1.55 μm in GaSb/ErSb nanoparticle superlattices grown by molecular beam epitaxy. Pump–probe measurements were made with a 1.55 μm mode-locked laser in transmission geometry to determine the photocarrier lifetime. The lifetime is found to be dependent on the size of the ErSb particles, amount of ErSb, and the distance between layers of particles. Through manipulation of these three parameters the photocarrier lifetime can be tuned down to less than 300 fs, the temporal limit of our experiment. [ABSTRACT FROM AUTHOR]

There are many preventive programs and interventions designed to address the complex problems of youth violence. However, research that examines the effectiveness of such programs is scarce. This article describes the evaluation of a media communications strategy, Choose to De-Fuse, developed for at-risk inner-city youth, and provides a case study of how qualitative data can be used to inform public policy.

The role of television in encouraging youth violence, and its potential as a prosocial teaching tool are examined. A media strategy developed by New York City in collaboration with inner-city youth exposed to violence, which focused on positive peer pressure for choosing nonviolent solutions to conflict is then delineated, along with the community and media coverage that followed. The effectiveness of the televised public service announcements appeared to be associated with the use of emotionally charged, real-life situations, speech, and body language by characters culturally appropriate to the target audience of at-risk youth.

Although alcoholism is often regarded as an intractable disorder that requires intensive treatment, studies of the natural history of alcoholism indicate that unaided, spontaneous recovery may be the most common pathway to remission from alcoholism. Negative environmental consequences of alcoholic drinking have been invoked to explain spontaneous recovery, but a more compelling reason for sudden changes in drinking behavior concerns shifts in the personal meanings surrounding alcohol use. Extensive interviews in a multimodal format were conducted with two groups of alcoholics: one group comprised of 7 subjects who spontaneously recovered without treatment and the other group comprised of 9 people who believed formal treatment was necessary to abstain from drinking. Spontaneously recovered alcoholics reported experiencing vivid sensations and images at the time they decided to quit drinking, and they reported subsequent transformations of their personal identities. Active alcoholics reported no comparable experiences in imaginal, sensory, and cognitive modalities. Implications of the results for current alcoholism treatments are discussed.