Optical control of capacitance in a metal-insulator-semiconductor diode with embedded metal nanoparticles.

This paper describes a metal-insulator-semiconductor (MIS) capacitor with flat capacitance voltage characteristics and a small quadratic voltage capacitance coefficient. The device characteristics resemble a metal-insulator-metal diode except that here the capacitance depends on illumination and exhibits a strong frequency dispersion. The device incorporates Fe nanoparticles (NPs), mixed with SrF2, which are embedded in an insulator stack of SiO2 and HfO2. Positively charged Fe ions induce dipole type traps with an electronic polarization that is enhanced by photogenerated carriers injected from the substrate and/or by inter nanoparticle exchange of carriers. The obtained characteristics are compared with those of five other MIS structures: two based on Fe NPs, one with and the other without SrF2 sublayers. Additionally, devices contain Co NPs embedded in SrF2 sublayers, and finally, two structures have no NPs, with one based on a stack of SiO2 and HfO2 and the other which also includes SrF2. Only structures containing Fe NPs, which are incorporated into SrF2, yield a voltage independent capacitance, the level of which can be changed by illumination. These properties are essential in radio frequency/analog mixed signal applications.

[Relationship between intravitreal anti-VEGF therapy and subretinal hemorrhage in patients with exudative age-related macular degeneration]. / Relation entre injection intravitréenne d'anti-VEGF et hématome sous-rétinien chez des patients atteints de dégénérescence maculaire liée à l'âge exsudative.

PURPOSE: To assess and compare frequencies and incidence rates of subretinal hemorrhage (SRH) after intravitreal anti-VEGF injections and spontaneous SRH in patients with exudative age-related macular degeneration (AMD). PATIENTS AND METHODS: This retrospective monocentric study included 1079 patients followed for exudative AMD in the ophthalmology department of the university hospital of Dijon from January 2007 to July 2012. For each SRH occuring during this period, the number of previous treatments with intravitreal anti-VEGF was determined, as well as the time between the last injection and the hemorrhage. The SRH was considered as an adverse effect of the anti-VEGF injection if it occurred within 2 months after the last IVT (post-IVT SRH). Frequencies and incidence rates of post-IVT SRH and spontaneous SRH were calculated. RESULTS: Sixty-six SRH's occurred during the study period with a total frequency of 6.12% (CI95% [4.69-7.55]). Frequencies of spontaneous and post-IVT SRH were respectively 5.65% (CI95% [4.28-7.03]) and 0.46% (CI95% [0.06-0.87]), representing a 12.2 ratio. Post-IVT SRH incidence was 8.3/1000 patient-years (CI95% [1.0-15.5]) and the spontaneous SRH incidence rate was 11.6/1000 patient-years (CI95% [8.3-14.8]), (P=0.472). The incidence rate ratio was 0.72 (CI95% [0.29-1.78]). CONCLUSION: This study did not show a statistically significant change in the incidence of SRH after intravitreal anti-VEGF therapy. The benefit/risk ratio of intravitreal anti-VEGF injections for exudative AMD remains high.

Shape-controlled nanopores in single crystals.

Nanometer length-scale holes (nanopores) are often formed in amorphous materials for fundamental studies of molecular mass transport. In the current study, electron beam irradiation in the transmission electron microscope was used to form nanopores in a crystalline material (Si). Analysis of the nanopores showed that they are formed by knock-on of atoms by the high energy incident electron beam, and surface diffusion is partially responsible for the hour-glass shapes that are found for some nanopores. Energetically favorable three-dimensional shapes of nanopores were simulated, and the nanopores simulated in the model crystalline material were found to be more stable than the nanopores simulated in the amorphous material. The nanopore shape was also found to depend on the nanopore diameter-to-length ratio. Based on the above, we demonstrate the advantage in using a crystalline material for nanopore formation and show that control of the three-dimensional shape of nanopores formed by electron beam irradiation is possible.

An experimental method for calibration of the plasmon mean free path.

Transmission electron microscopy specimens in the form of elongated, conical needles were made using a dual-beam focused ion beam system, allowing the specimen thickness to be geometrically determined for a range of thickness values. From the same samples electron energy loss maps were acquired and the plasmon mean free path (lambda) for inelastic scattering was determined experimentally from the measured values of specimen thickness. To test the method lambda was determined for Ni (174 +/- 17 nm), alpha-Al(2)O(3) (143 +/- 14 nm), Si (199 +/- 20 nm) and amorphous SiO(2) (238 +/- 12 nm), and compared both to experimental values of lambda taken from the literature and to calculated values. The calculated values of lambda significantly underestimate the true sample thickness for high accelerating voltages (300 kV) and large collection angles. A linear dependence of lambda on thickness was confirmed for t/lambda < 0.5-0.6, but this method also provides an approach for calibrating lambda at sample thicknesses for which multiple scattering occurs, thus expanding the thickness range over which electron energy loss spectroscopy can be used to determine the absolute sample thickness (t/lambda > 0.6). The experimental method proposed in this contribution offers a means to calibrate lambda for any type of material or phase that can be milled using a focused ion beam system.

Ordered liquid aluminum at the interface with sapphire.

Understanding the nature of solid-liquid interfaces is important for many processes of technological interest, such as solidification, liquid-phase epitaxial growth, wetting, liquid-phase joining, crystal growth, and lubrication. Recent studies have reported on indirect evidence of density fluctuations at solid-liquid interfaces on the basis of x-ray scattering methods that have been complemented by atomistic simulations. We provide evidence for ordering of liquid atoms adjacent to an interface with a crystal, based on real-time high-temperature observations of alumina-aluminum solid-liquid interfaces at the atomic-length scale. In addition, crystal growth of alumina into liquid aluminum, facilitated by interfacial transport of oxygen from the microscope column, was observed in situ with the use of high-resolution transmission electron microscopy.