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Jang G.G.,University of Arkansas | Hawkridge M.E.,Institute for Nanoscience and Engineering | Roper D.K.,University of Arkansas
Journal of Materials Chemistry | Year: 2012

Morphological and physicochemical disposition of silver (Ag) during redox-driven self-assembly of metal films on silica surfaces under equilibrium hydraulic conditions has been examined in real time in a novel electroless (EL) metal deposition cell by transmission UV-vis (T-UV) spectroscopy. Optical features due to localized surface plasmon resonance, surface plasmon polaritons, and photoluminescence from Ag and gold (Au) nanoarchitectures such as particles, clusters, and films were attributed by correlating T-UV with time-resolved scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Silver that deposited onto tin-sensitized surfaces in thin films nucleated nanoparticles when exposed to reductant or broadband light. Kinetic changes in plasmon features suggested four previously unrecognized time-dependent physicochemical regimes occur during consecutive EL deposition of Ag and Au onto tin-sensitized silica surfaces: self-limiting Ag activation; transitory Ag nanoparticle formation; transitional Au-Ag alloy formation during galvanic replacement of Ag by Au; and uniform metal deposition under controlled hydraulic conditions. Growth mechanisms at the surface, interior, and interface of the resulting thin metal films inferred from real time T-UV spectra were characterized by depth profile XPS analysis. © 2012 The Royal Society of Chemistry.

An international group of physicists has discovered a phenomenon of large magnitude in an unexpected class of materials that can lead to a variety of devices used in optical systems. That phenomenon — the elasto-optic effect — characterizes the formation of a periodic variance of light refraction when an acoustic wave propagates in optical materials, says Yurong Yang, a research assistant professor at the University of Arkansas who led the research. “We found a significantly large elasto-optic effect in thin films made of materials called ferroelectrics,” Yang says, “which are usually considered for their changes in mechanical energy into electrical energy and vice versa, as well in multiferroelectric thin films, which are commonly investigated because of the possible control of their magnetic response by electric input, as well as of their electric response by magnetic input.” The research group published its findings in a paper in Physical Review Letters, the journal of the American Physical Society. A second paper describing the research was published in Nature Communications, an online journal published by the journal Nature. “Those discoveries of a large elasto-optic effect in ferroelectrics and multiferroelectrics therefore broaden the potential of these materials since they can now be put in use to also control their optical responses by elastic property,” says Laurent Bellaiche, Distinguished Professor of physics at the U of A, “which suggests exciting device opportunities arising from this overlooked coupling in these classes of materials.” Yang and Bellaiche, who holds the Twenty-First Century Endowed Professorship in Nanotechnology and Science Education, both conduct research in the Institute for Nanoscience and Engineering and physics department at the U of A. The researchers performed calculations on supercomputers at the Arkansas High Performance Computing Center and a U.S. Department of Defense supercomputing resource. The results published in Physical Review Letters were obtained through a collaborative effort with Zhigang Gui, a U of A physics graduate who is now a postdoctoral research associate at the University of Delaware; Lan Chen and X.K. Meng at Nanjing University in China, and Daniel Sando and Manuel Bibes at University of Paris-Sud in France. The results published in Nature Communications were obtained through a collaborative effort with Daniel Sando and Manuel Bibes and Cecile Carretero, Vincent Garcia, Stephane Fusil, and Agnes Barthelemy at the University of Paris-Sud; Eric Bousquet and Philippe Ghosez at the University of Liege in Belgium; and Daniel Dolfi of Thales Research and Technology in France. Source: University of Arkansas

Grant P.C.,University of Arkansas | Fan D.,University of Arkansas | Mosleh A.,University of Arkansas | Yu S.-Q.,University of Arkansas | And 6 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2014

The effect of rapid thermal annealing on the optical and structural properties of GaAsBi/GaAs quantum wells (QWs) is investigated. The photoluminescence (PL) spectra of the samples are measured at 80K and room temperature before and after rapid thermal annealing, to ascertain any improvement in the optical quality of the material. The impact of annealing temperature on QW interface quality, layer composition, and thicknesses are studied with x-ray diffraction. For a 60second annealing time, the low temperature peak PL intensity increases to a maximum of 1.8 times the original intensity at an annealing temperature of 500°C. Validating this optimum annealing temperature, the room temperature PL peak intensity is seen to increase by 2.2 times. The peak position exhibits a minor blueshift of 15meV throughout the 450-700°C temperature range, while annealing at 750°C produces a blue-shift on the order of 100meV, indicating out-diffusion of bismuth from the QW. Degradation of the QW interfaces with annealing temperatures above 550°C is observed. The composition and thickness of the QWs remained constant up to 700°C. Significant out-diffusion of bismuth and QW thinning are observed at an annealing temperature of 750°C. © 2014 American Vacuum Society.

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