Optimum deposition conditions of ultrasmooth silver nanolayers

Reduction of surface plasmon-polariton losses due to their scattering on metal surface roughness still remains a challenge in the fabrication of plasmonic devices for nanooptics. To achieve smooth silver films, we study the dependence of surface roughness on the evaporation temperature in a physical vapor deposition process. At the deposition temperature range 90 to 500 K, the mismatch of thermal expansion coefficients of Ag, Ge wetting layer, and sapphire substrate does not deteriorate the metal surface. To avoid ice crystal formation on substrates, the working temperature of the whole physical vapor deposition process should exceed that of the sublimation at the evaporation pressure range. At optimum room temperature, the root-mean-square (RMS) surface roughness was successfully reduced to 0.2 nm for a 10-nm Ag layer on sapphire substrate with a 1-nm germanium wetting interlayer. Silver layers of 10- and 30-nm thickness were examined using an atomic force microscope (AFM), X-ray reflectometry (XRR), and two-dimensional X-ray diffraction (XRD2).

PACS

63.22.Np Layered systems; 68. Surfaces and interfaces; thin films and nanosystems (structure and nonelectronic properties); 81.07.-b Nanoscale materials and structures: fabrication and characterization     

Recalcitrant tumor of the fifth metacarpal bone in a hemodialyzed patient

The article presents a case report about a 38‐year‐old hemodialyzed woman who presented to our department with a painful, expansile, lytic bone lesion of the fifth metacarpal epiphysis. The lesion was resected and replaced by corticocancellous bone graft. At 3 months, imaging suggested signs of graft resorption and local recurrence which necessitated repeat excision and grafting. Because of secondary parathyroidism subsequent subtotal parathyroidectomy was performed. This procedure leads to appropriate bone remodeling by 8 weeks postoperatively, and recurrence has not been observed at 2 years of follow up.     

Reputation as optimality measure in Wireless Sensor Network-based monitoring systems

In this paper we propose a new optimality measure for Wireless Sensor Network-based structural monitoring systems. First, we present the results of experiments showing the reasons for random effects in Wireless Sensor Network (WSN) functioning. Then, the formulas for calculating a network’s reputation measure are given. Finally, we conclude with arguments for the application of the reputation-based optimality measure in WSNs. We propose significantly new recommendations for the design and usage of WSNs.     

Monolithic ZnTe-based pillar microcavities containing CdTe quantum dots

Micropillars of different diameters have been prepared by focused ion beam milling out of a planar ZnTe-based cavity. The monolithic epitaxial structure, deposited on a GaAs substrate, contains CdTe quantum dots embedded in a ZnTe λ-cavity delimited by two distributed Bragg reflectors (DBRs). The high refractive index material of the DBR structure is ZnTe, while for the low index material a short-period triple MgTe/ZnTe/MgSe superlattice is used. The CdTe quantum dots are formed by a novel Zn-induced formation process and are investigated by scanning transmission electron microscopy. Micro-photoluminescence measurements show discrete optical modes for the pillars, in good agreement with calculations based on a vectorial transfer matrix method. The measured quality factor reaches a value of 3100.     

Ultra-fast vapour-liquid-solid synthesis of Si nanowires using ion-beam implanted gallium as catalyst

The feasibility of gallium as a catalyst for vapour-liquid-solid (VLS) nanowire (NW) growth deriving from an implantation process in silicon by a focused ion beam (FIB) is investigated. Si(100) substrates are subjected to FIB implantation of gallium ions with various ion fluence rates. NW growth is performed in a hot wall chemical vapour deposition (CVD) reactor at temperatures between 400 and 500?°C with 2% SiH(4)/He as precursor gas. This process results in ultra-fast growth of (112)- and (110)-oriented Si-NWs with a length of several tens of micrometres. Further investigation by transmission electron microscopy indicates the presence of a NW core-shell structure: while the NW core yields crystalline structuring, the shell consists entirely of amorphous material.     

Determination of electrical and mechanical parameters in capacitive MEMS accelerometers using electrical measurements

This paper describes a simple technique for characterization of capacitive MEMS accelerometers. The method is based on electrical impedance (admittance) measurements of capacitive MEMS accelerometers treated as electrostatically-driven microelectromechanical resonators. By using this method, it is possible to determine some electrical and mechanical parameters including the shunt capacitance, the mechanical resonance frequency and quality factor. These parameters may serve as measures of structural integrity of the tested structures and their packages during reliability testing, for instance.     

Compound prism design principles, I

Prisms have been needlessly neglected as components used in modern optical design. In optical throughput, stray light, flexibility, and in their ability to be used in direct-view geometry, they excel over gratings. Here we show that even their well-known weak dispersion relative to gratings has been overrated by designing doublet and double Amici direct-vision compound prisms that have 14° and 23° of dispersion across the visible spectrum, equivalent to 800 and 1300 lines/mm gratings. By taking advantage of the multiple degrees of freedom available in a compound prism design, we also show prisms whose angular dispersion shows improved linearity in wavelength. In order to achieve these designs, we exploit the well-behaved nature of prism design space to write customized algorithms that optimize directly in the nonlinear design space. Using these algorithms, we showcase a number of prism designs that illustrate a performance and flexibility that goes beyond what has often been considered possible with prisms.     

Compound prism design principles, III: linear-in-wavenumber and optical coherence tomography prisms

We extend the work of the first two papers in this series [Appl. Opt. 50, 4998-5011 (2011), Appl. Opt. 50, 5012-5022 (2011)] to design compound prisms for linear-in-wavenumber dispersion, especially for application in spectral domain optical coherence tomography (OCT). These dispersive prism designs are believed to be the first to meet the requirements of high resolution OCT systems in direct-view geometry, where they can be used to shrink system size, to improve light throughput, to reduce stray light, and to reduce errors resulting from interpolating between wavelength- and wavenumber-sampled domains. We show prism designs that can be used for thermal sources or for wideband superluminescent diodes centered around wavelengths 850, 900, 1300, and 1375 nm.     

Numerical investigation of the stress field near a crack normal to ceramic-metal interface

Ceramic-metal interfaces are often present in composite materials. The presence of cracks has a major impact on the reliability of advanced materials, such as fiber or particle reinforced ceramic composites, ceramic interfaces and laminated ceramics. The understanding of the failure mechanisms is very important, as is as the estimation of fracture parameters at the tip of the crack approaching an interface and crack propagation path. A cracked sandwich plate loaded with axial uniform normal stress was numerically investigated using plane strain Finite Element Analysis. The numerical results for the singularity orders were compared with the analytical solution. The influences of the material combination and crack length on the radial and circumferential stresses and displacement distributions were investigated. The Stress Intensity Factors were determined based on numerical results using a displacement extrapolation method. The results for the non-dimensional stress intensity factors show that at lower crack lengths the influence of material mismatch is lower, but this influence increases with increasing crack length.     

The Effect of Exogenous Application of Quercetin Derivative Solutions on the Course of Physiological and Biochemical Processes in Wheat Seedlings

Quercetin, classified as a flavonoid, is a strong antioxidant that plays a significant role in the regulation of physiological processes in plants, which is particularly important in the case of biotic and abiotic stresses. The study investigated the effect of the use of potassium quercetin solutions in various concentrations (0.5%, 1.0%, 3.0% and 5.0%) on the physiological and biochemical properties of wheat seedlings. A pot experiment was carried out in order to determine the most beneficial dose of this flavonoid acting as a bio-stimulant for wheat plants. Spraying with quercetin derivative solutions was performed twice, and physiological measurements (chlorophyll content and fluorescence as well as gas exchange) were carried out on the first and seventh days after each application. The total phenolic compounds content and the total antioxidant capacity were also determined. It was shown that the concentrations of potassium quercetin applied have a stimulating effect on the course of physiological processes. In the case of most of the tested physiological parameters (chlorophyll content and fluorescence and gas exchange) and the total antioxidant capacity, no significant differences were observed in their increase as a result of application with concentrations of 3.0 and 5.0%. Therefore, the beneficial effect of quercetin on the analysed parameters is already observed when spraying with a concentration of 3.0%.