Improved thermal isolation of silicon suspended platforms for an all-silicon thermoelectric microgenerator based on large scale integration of Si nanowires as thermoelectric material

Special suspended micro-platforms have been designed as a part of silicon compatible planar thermoelectric microgenerators. Bottom-up grown silicon nanowires are going to bridge in the future such platforms to the surrounding silicon bulk rim. They will act as thermoelectric material thus configuring an all-silicon thermoelectric device. In the new platform design other additional bridging elements (usually auxiliary support silicon beams) are substituted by low conductance thin film dielectric membranes in order to maximize the temperature difference developed between both areas. These membranes follow a sieve-like design that allows fabricating them with a short additional wet anisotropic etch step. © Published under licence by IOP Publishing Ltd.Peer ReviewedPostprint (published version

Atomic layer deposition of GaN at low temperatures

Cataloged from PDF version of article.The authors report on the self-limiting growth of GaNthin films at low temperatures. Films were deposited on Si substrates by plasma-enhanced atomic layer deposition using trimethylgallium (TMG) and ammonia (NH3) as the group-III and -V precursors, respectively. GaNdeposition rate saturated at 185 °C for NH3 doses starting from 90 s. Atomic layer deposition temperature window was observed from 185 to ∼385 °C. Deposition rate, which is constant at ∼0.51 Å/cycle within the temperature range of 250 – 350 °C, increased slightly as the temperature decreased to 185 °C. In the bulk film, concentrations of Ga, N, and O were constant at ∼36.6, ∼43.9, and ∼19.5 at. %, respectively. C was detected only at the surface and no C impurities were found in the bulk film. High oxygen concentration in films was attributed to the oxygen impurities present in group-V precursor. High-resolution transmission electron microscopy studies revealed a microstructure consisting of small crystallites dispersed in an amorphous matrix

Self-limiting low-temperature growth of crystalline AIN thin films by plasma-enhanced atomic layer deposition

Cataloged from PDF version of article.We report on the self-limiting growth and characterization of aluminum nitride (AlN) thin films. AlN films were deposited by plasma-enhanced atomic layer deposition on various substrates using trimethylaluminum (TMA) and ammonia (NH3). At 185 degrees C, deposition rate saturated for TMA and NH3 doses starting from 0.05 and 40 S. respectively. Saturative surface reactions between TMA and NH3 resulted in a constant growth rate of similar to 0.86 angstrom/cycle from 100 to 200 degrees C. Within this temperature range, film thickness increased linearly with the number of deposition cycles. At higher temperatures (>= 225 degrees C) deposition rate increased with temperature. Chemical composition and bonding states of the films deposited at 185 degrees C were investigated by Xray photoelectron spectroscopy. High resolution Al 2p and N 1s spectra confirmed the presence of AlN with peaks located at 73.02 and 396.07 eV, respectively. Films deposited at 185 degrees C were polycrystalline with a hexagonal wurtzite structure regardless of the substrate selection as determined by grazing incidence X-ray diffraction. High-resolution transmission electron microscopy images of the AlN thin films deposited on Si (100) and glass substrates revealed a microstructure consisting of nanometer sized crystallites. Films exhibited an optical band edge at similar to 5.8 eV and an optical transmittance of >95% in the visible region of the spectrum. (C) 2011 Elsevier B.V. All rights reserved

Assessment of genotype x environment interaction on yield and yield components of durum wheat genotypes by multivariate analyses

Wheat breeders have to determine the new cultivars and lines responsive to the environmental changes for grain yield and yield components. Therefore, this study was conducted to evaluate 25 durum wheat (Triticum turgidum spp. durum) genotypes including 12 registered cultivars and 13 advanced breeding lines for their stability grown in three different locations (Tokat-Kazova, Diyarbakir and Sivas-Ulas) of Turkey for two growing seasons (2005-2006 and 2006-2007), and to select genotypes having desirable traits to be used in future durum wheat breeding program. Field trials were conducted in a randomized complete block design with three replications at each location. Days to heading, plant height, number of spikes per square meter, number of kernels per spike, spike weight, 1000 kernel weight and grain yield of the genotypes were evaluated in each location. The regression coefficient (bi) of Finlay and Wilkinson (1963) and mean square of deviation from regression (S2d) of Eberhart and Russell (1966) were used as the stability parameters. The results of combined analysis of variance showed a strong influence of the locations on plant height, number of spikes per square meter, number of kernels per spike,  spike weight, 1000 kernel weight and grain yield. Genotypic effects were mainly observed for spike length and test weight. Year had strong impact only on the days to heading. Ecological conditions of Diyarbakir among locations offer the better opportunity for production of durum wheat. Line 5 and cultivar Gidara were both stable in yield ability and also appeared the stable group based on the cluster analysis. In the first principal component days to heading, number of spikes per square meter and spike length  were the most important traits contributing to variation that obtained about 44.3%. There was a positive relationship between grain yield and number of spikes per square meter together test weight, whereas days to heading and spike length were negatively correlated to grain yield. The results of this study also imply that Line-5 and cultivar Gidara among genotypes were the most stable cultivars and can be used as breeding materials. The days to heading, number of spikes per square meter and spike length could be adequate to introduce the differences among genotypes.Key words: Durum wheat, stability, principal component analysis, cluster analysis

Electrical characteristics of B-GaN2O3 thin films grown by PEALD

Cataloged from PDF version of article.In this work, 7.5 nm Ga2O3 dielectric thin films have been deposited on p-type (111) silicon wafer using plasma enhanced atomic layer deposition (PEALD) technique. After the deposition, Ga2O3 thin films were annealed under N-2 ambient at 600, 700, and 800 degrees C to obtain beta-phase. The structure and microstructure of the beta-Ga2O3 thin films was carried out by using grazing-incidence X-ray diffraction (GIXRD). To show effect of annealing temperature on the microstructure of beta-Ga2O3 thin films, average crystallite size was obtained from the full width at half maximum (FWHM) of Bragg lines using the Scherrer formula. It was found that crystallite size increased with increasing annealing temperature and changed from 0.8 nm to 9.1 nm with annealing. In order to perform electrical characterization on the deposited films, Al/beta-Ga2O3/p-Si metal-oxide-semiconductor (MOS) type Schottky barrier diodes (SBDs) were fabricated using the beta-Ga2O3 thin films were annealed at 800 degrees C. The main electrical parameters such as leakage current level, reverse breakdown voltage, series resistance (R-S), ideality factor (n), zero-bias barrier height (phi(Bo)), and interface states (N-SS) were obtained from the current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. The RS values were calculated by using Cheung methods. The energy density distribution profile of the interface states as a function of (E-SS-E-V) was obtained from the forward bias I-V measurements by taking bias dependence of ideality factor, effective barrier height (phi(e)), and R-S into account. Also using the Norde function and C-V technique, phi(e) values were calculated and cross-checked. Results show that beta-Ga2O3 thin films deposited by PEALD technique at low temperatures can be used as oxide layer for MOS devices and electrical properties of these devices are influenced by some important parameters such as NSS, RS, and beta-Ga2O3 oxide layer. (C) 2014 Elsevier B.V. All rights reserved

Effect of post-deposition annealing on the electrical properties of B-Ga2O3 thin films grown on p-Si by plasma-enhanced atomic layer deposition

Cataloged from PDF version of article.Ga2O3 dielectric thin films were deposited on (111)-oriented p-type silicon wafers by plasma-enhanced atomic layer deposition using trimethylgallium and oxygen plasma. Structural analysis of the Ga 2O3 thin films was carried out using grazing-incidence x-ray diffraction. As-deposited films were amorphous. Upon postdeposition annealing at 700, 800, and 900°C for 30min under N2 ambient, films crystallized into β-form monoclinic structure. Electrical properties of the β-Ga2O3 thin films were then investigated by fabricating and characterizing Al/β-Ga2O3/p-Si metal-oxide-semiconductor capacitors. The effect of postdeposition annealing on the leakage current densities, leakage current conduction mechanisms, dielectric constants, flat-band voltages, reverse breakdown voltages, threshold voltages, and effective oxide charges of the capacitors were presented. The effective oxide charges (Qeff) were calculated from the capacitance-voltage (C-V) curves using the flat-band voltage shift and were found as 2.6×1012, 1.9×1012, and 2.5×10 12 cm-2 for samples annealed at 700, 800, and 900°C, respectively. Effective dielectric constants of the films decreased with increasing annealing temperature. This situation was attributed to the formation of an interfacial SiO2 layer during annealing process. Leakage mechanisms in the regions where current increases gradually with voltage were well fitted by the Schottky emission model for films annealed at 700 and 900°C, and by the Frenkel-Poole emission model for film annealed at 800°C. Leakage current density was found to improve with annealing temperature. β-Ga2O3 thin film annealed at 800°C exhibited the highest reverse breakdown field value. © 2014 American Vacuum Society

Characterisation of an n-type segmented BEGe detector

A four-fold segmented n-type point-contact "Broad Energy" high-purity germanium detector, SegBEGe, has been characterised at the Max-Planck-Institut f\"ur Physik in Munich. The main characteristics of the detector are described and first measurements concerning the detector properties are presented. The possibility to use mirror pulses to determine source positions is discussed as well as charge losses observed close to the core contact

Polymer-inorganic core-shell nanofibers by electrospinning and atomic layer deposition: flexible nylon-znO core-shell nanofiber mats and their photocatalytic activity

Cataloged from PDF version of article.Polymer-inorganic core-shell nanofibers were produced by two-step approach; electrospinning and atomic layer deposition (ALD). First, nylon 6,6 (polymeric core) nanofibers were obtained by electrospinning, and then zinc oxide (ZnO) (inorganic shell) with precise thickness control was deposited onto electrospun nylon 6,6 nanofibers using ALD technique. The bead-free and uniform nylon 6,6 nanofibers having different average fiber diameters (∼80, ∼240 and ∼650 nm) were achieved by using two different solvent systems and polymer concentrations. ZnO layer about 90 nm, having uniform thickness around the fiber structure, was successfully deposited onto the nylon 6,6 nanofibers. Because of the low deposition temperature utilized (200 °C), ALD process did not deform the polymeric fiber structure, and highly conformal ZnO layer with precise thickness and composition over a large scale were accomplished regardless of the differences in fiber diameters. ZnO shell layer was found to have a polycrystalline nature with hexagonal wurtzite structure. The core-shell nylon 6,6-ZnO nanofiber mats were flexible because of the polymeric core component. Photocatalytic activity of the core-shell nylon 6,6-ZnO nanofiber mats were tested by following the photocatalytic decomposition of rhodamine-B dye. The nylon 6,6-ZnO nanofiber mat, having thinner fiber diameter, has shown better photocatalytic efficiency due to higher surface area of this sample. These nylon 6,6-ZnO nanofiber mats have also shown structural stability and kept their photocatalytic activity for the second cycle test. Our findings suggest that core-shell nylon 6,6-ZnO nanofiber mat can be a very good candidate as a filter material for water purification and organic waste treatment because of their photocatalytic properties along with structural flexibility and stability. © 2012 American Chemical Society

EFFECTS OF TIME PRESSURE ON THE USE OF AN AUTOMATED DECISION SUPPORT SYSTEM FOR STRIKE PLANNING

This paper describes the results of an experiment designed to examine the effects of time pressure on behavioral patterns. The main research hypothesis is that people under time pressure tend to increasingly rely on automation in order to cope with the added workload. The context is that of a missile strike planner having to create a set of matches between resources (missiles) and requirements (missions). We introduce time pressure by changing the temporal requirements towards the end of the mission. Overall performance, calls to automation and qualitative strategies are recorded and analyzed using ANOVA and other nonparametric tests. The main finding of this study is that while the number of calls to the automation did significantly increase under time pressure, there did not seem to be a statistically significant shift in problem solving strategies under time pressure. The experimental results show the importance of good automation-human interface design so as to gain maximum benefit from the use of an automated decision support systems.Boeing Corporatio