Optical doping of nitrides by ion implantation

A series of rare earth elements (RE) were implanted in GaN epilayers to study the lattice site location and optical activity. Rutherford backscattering spectrometry in the channeling mode(RBS/C) was used to follow the damage behavior in the Ga sublattice and the site location of the RE. For all the implanted elements (Ce, Pr, Dy, Er, and Lu) the results indicate the complete substitutionality on Ga sites after rapid thermal annealing at 1000°C for 2 min. The only exception occurs for Eu, which occupies a Ga displaced site. Annealing at 1200°C in nitrogen atmosphere at a pressure of IGPa is necessary to achieve the complete recovery of the damage in the samples. After annealing the recombination processes of the implanted samples were studied by above and below band gap excitation. For Er implanted samples besides the 1.54 μm emission green and red emissions are also observed. Red emissions from 5D0→7F2 and 3P0→3F2 transitions were found in Eu and Pr implanted samples even at room temperature

p-type GaN grown by phase shift epitaxy

Phase shift epitaxy (PSE) is a periodic growth scheme, which desynchronizes host material growth process from dopant incorporation, allowing independent optimization. p-type doping of GaN with Mg by PSE is accomplished with molecular beam epitaxy by periodic shutter action (in order to iterate between Ga-and N-rich surface conditions) and by adjusting time delays between dopant and Ga shutters. Optimum PSE growth was obtained by turning on the Mg flux in the N-rich condition. This suppresses Mg self-compensation at high Mg concentration and produces fairly high hole concentrations (2.4 Â 10 18 cm À

DNA-Controlled Excitonic Switches

Fluorescence resonance energy transfer (FRET) is a promising means of enabling information processing in nanoscale devices, but dynamic control over exciton pathways is required. Here, we demonstrate the operation of two complementary switches consisting of diffusive FRET transmission lines in which exciton flow is controlled by DNA. Repeatable switching is accomplished by the removal or addition of fluorophores through toehold-mediated strand invasion. In principle, these switches can be networked to implement any Boolean function

Focused ion beam micromilling of GaN and related substrate materials "sapphire, SiC, and Si…

Micromilling of GaN films has been obtained using a Ga ϩ focused ion beam ͑FIB͒. The GaN micromilling has been investigated over a range of energies ͑15-70 keV͒, incident angles (0°-30°), and number of scans ͑10-50͒. At normal incidence, increasing the Ga ϩ energy up to 50 keV increases the milling rate, while higher energies produce the same ͑or a slightly decreased͒ milling rate. Increasing the angle of incidence increases the milling rate at all energies. The highest GaN milling rate of 0.6 m 3 /nA s ͑corresponding to an average yield of 6.6 atoms/ion͒ has been obtained at 50 keV, 30°incidence, and 50 scans. The milling rate of current substrate materials ͑sapphire, Si and SiC͒ for GaN thin film growth is shown to be 2-5 times lower. The sputtering yield is found to vary inversely with the strength of the chemical bond in the materials investigated. Distributed Bragg reflection air/GaN gratings for short cavity lasers were fabricated to show the capability of FIB micromilling to produce optoelectronic devices based on GaN

Electrowetting on paper for electronic paper display

ABSTRACT The use of paper as a material for various device applications (such as microfluidics and energy storage) is very attractive given its flexibility, versatility, and low cost. Here we demonstrate that electrowetting (EW) devices can be readily fabricated on paper substrates. Several categories of paper have been investigated for this purpose, with the surface coating, roughness, thickness, and water uptake, among the most important properties. The critical parameter for EW devices is the water contact angle (CA) change with applied voltage. EW devices on paper exhibit characteristics very close to those of conventional EW devices on glass substrates. This includes a large CA change in oil ambient (90-95°), negligible hysteresis (∼2°), and fast switching times of ∼20 ms. These results indicate the promise of low-cost paper-based EW devices for video rate flexible e-paper on paper