bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties of Single Crystal Diamond Estimated by Molecular Dynamics Simulation with the Second-Generation REBO Potential
Authors: Okamoto Shingo , Ito Akihiko
Published: September 2011

We investigated the effects of tensile direction and periodic boundary condition (PBC) on the mechanical properties of single crystal diamond (SCD) under tensile loading, using MD simulations with the second-generation reactive empirical bond order (REBO) potential. We found that when the Poisson’s ratio is assumed to be constant under the canonical (NVT) ensemble and the PBC is applied to all directions of X, Y, and Z, each qualitative relation between a mechanical property such as tensile strength or Young’s modulus and the tensile direction is in agreement with both the results calculated by the first principle and by the cleavage energy method. In addition, we found that when the PBC is applied only to the Y direction under the NVT ensemble, each qualitative relation between a mechanical property and the tensile directions is in agreement with the MD results using the Tersoff potential.

Our results indicate that the second-generation REBO potential is also useful for MD simulations on the tension of diamond.
ZrO2 Layer Thickness Dependent Electrical and Dielectric Properties of BST/ZrO2/BST Multilayer Thin Films
Authors: Sahoo Santosh K. , Misra D. , Agrawal D. C. , Mohapatra Y. N.
Published: September 2011

Recently, high K materials play an important role in microelectronic devices such as capacitors, memory devices, and microwave devices. Now a days ferroelectric barium strontium titanate [BaxSr1-xTiO3, (BST)] thin film is being actively investigated for applications in dynamic random access memories (DRAM), field effect transistor (FET), and tunable devices because of its properties such as high dielectric constant, low leakage current, low dielectric loss, and high dielectric breakdown strength. Several approaches have been used to optimize the dielectric and electrical properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in dielectric constant, loss tangent, and leakage current in the multilayer thin films. Also it is shown that the properties of multilayer structure are found to depend strongly on the sublayer thicknesses. In this work the effect of ZrO2 layer thickness on the dielectric, ferroelectric as well as electrical properties of BST/ZrO2/BST multilayer structure is studied. The multilayer Ba0.8Sr0.2TiO3/ZrO2/Ba0.8Sr0.2TiO3 film is deposited by a sol-gel process on the platinized Si substrate. The thickness of the middle ZrO2 layer is varied while keeping the top and bottom BST layer thickness as fixed. It is observed that the dielectric constant, dielectric loss tangent, and leakage current of the multilayer films reduce with the increase of ZrO2 layer thickness and hence suitable for memory device applications. The ferroelectric properties of the multilayer film also decrease with the ZrO2 layer thickness.
Electronic Structure and Optical Absorption of Fluorographene
Authors: Liang Yufeng , Yang Li
Published: September 2011

A first-principles study on the quasiparticles energy and optical absorption spectrum of fluorographene is presented by employing the GW + Bethe-Salpeter Equation (BSE) method with many-electron effects included. The calculated band gap is increased from 3.0 eV to 7.3 eV by the GW approximation. Moreover, the optical absorption spectrum of fluorographene is dominated by enhanced excitonic effects. The prominent absorption peak is dictated by bright resonant excitons around 9.0 eV that exhibit a strong charge transfer character, shedding light on the exciton condensation and relevant optoelectronic applications. At the same time, the lowest-lying exciton at 3.8 eV with a binding energy of 3.5 eV is identified, which gives rise to explanation of the recent ultraviolet photoluminescence experiment.
Ionizing Radiation Total Dose Detectors Using Oligomer Organic Semiconductor Material and Devices
Authors: Raval Harshil N. , Rao V. Ramgopal
Published: September 2011

Organic semiconducting oligomer – Pentacene, as a material and organic electronic devices based on it, are proposed here as total dose detectors for ionizing radiation. Pentacene, when exposed to ionizing radiation of γ – rays using Cobalt – 60 (60Co) radiation source, shows increase in the conductivity of the material which can be used as a sensing phenomenon for determining the dose of ionizing radiation. The change in material property was also verified using UV-visible (UV-VIS) spectrum for pentacene thin-films with rising absorption peaks at the oxidized positions in the wavelength. A pentacene resistor can be used as a detector, as the change in the conductivity of the pentacene film can be easily quantified by measuring the change in resistance of the pentacene resistor after different total radiation dose exposures. The experiments resulted in a sensitivity of 340 kΩ/Gy for a total 100 Gy radiation dose for the pentacene resistor. Furthermore, employing this simple electrical measurement technique for determining the dose of ionizing radiation and to improve the sensitivity of the sensor by transistor action, a pentacene based organic field effect transistor (OFET) was exposed to ionizing radiation. Change in OFF current (IOFF) of the OFET sensor with W/L = 19350 μm/100 μm, suggests a sensitivity of 21 nA/Gy for 100 Gy dose. Also, changes in various other parameters like threshold voltage, subthreshold swing, field effect mobility, number of interface states etc. can be extracted from the electrical characterizations which prove their usefulness as a detector for ionizing radiation.
Multi-layered PVDF Systems for Enhanced Energy Harvesting and Sensing
Authors: Jones Jennifer , Aga Roberto S. , Mu Richard
Published: September 2011

The peak output voltage (VL) of polyvinylidene fluoride (PVDF) piezoelectric devices has been investigated as a function of load resistance (RL). Two identical piezoelectric devices were mounted, back to back, on a vibrating cantilever giving almost similar VL. Using RL values in the range of 4.6 KΩ to 1 MΩ, it was observed that VL was doubled when the devices were connected in parallel but it did not change when the devices were connected in series. For single, parallel and series configurations, VL increases linearly with increasing RL. These results are explained well by modeling the device as a discharging capacitor with internal source of charge generation.
Investigation of Inherently Conductive Polymer as Structure Health Monitoring Sensor for Composite
Authors: Yang Huaxiang , Kim Dongsik , Singh Abhishek K. , Pitts Brady W. , Tregre Gregory J. , Kinlen Patrick J.
Published: September 2011

A soluble polyaniline was synthesized through emulsion polymerization and characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), gel permeation chromatography (GPC), viscosity analysis, and coefficient of linear thermal expansion (CLTE) determination. The electrical conductivity is found to reach 1000 S/cm with specific post doping treatments. Multiple printing processes, such as inkjet printing, screen printing and aerosol jet printing etc, make it feasible to print a variety of sensor patterns. The electromechanical response of these sensors was used to measure strain/stress or damage of composite structures under various load conditions expected to be experienced by aircraft. These unique conductive polymer sensors provide a feasible, near real time monitoring system for composites without adding significant additional weight to the structure.
Stability Improvement of Polymer Based Solar Cells by Thermally Evaporated Cr2O3 Interfacial Layer
Authors: Wang Mingdong , Xie Fangyan , Zheng Shizhao , Xu Jianbin.
Published: September 2011

We report on Cr2O3 layer by thermal evaporation of Cr2O3 powder as cathode interfacial layer to improve the stability in air for the bulk heterojunction solar cells of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Devices with Cr2O3 interfacial layers show higher power conversion efficiency (PCE) and stability than those without interfacial layer. Devices with Cr2O3 show improved stability approximately 100 times than that of devices without interfacial layer or with LiF interfacial layer.
Poly(vinylidene fluoride-trifluoroethylene) (72/28) interconnected porous membranes obtained by crystallization from solution
Authors: Ferreira Armando , Silva Jaime , Sencadas Vitor , Gómez-Ribelles José Luís , Lanceros-Méndez Senentxu
Published: September 2011

Electroactive macroporous poly[(vinylidene fluoride)-co-trifluoroethylene] membranes have been processed by solvent evaporation at room temperature with different polymer/solvent concentrations. The pore architecture consists on interconnected spherical pores and this morphology is independent of the membrane thickness. The porosity of the produced membranes increases from 72% for the higher polymer concentration in the polymer/solvent solution (15/85), up to 80% for the lowest polymer concentration in the polymer/solvent solution.

Fourier transform infrared spectroscopy and differential scanning calorimetry measurements reveal that the polymer crystallizes in the ferroelectric phase and the polymer/solvent ratio does not influences the Curie transition and the melting temperature of the polymer.
In situ Imaging at the NIST Neutron Imaging Facility
Authors: Jacobson David L. , Hussey Daniel S. , Baltic Eli
Published: September 2011

Neutron imaging as a method to perform in situ studies of hydrogen fuel cells, hydrogen storage devices, heat pipes, and batteries has made tremendous progress in recent years. Neutrons are useful to study light elements mixed with heavy Z elements where penetration by other forms of radiation is either impossible or incapable of contrasting the light elements. Useful spatial resolution available at neutron imaging facilities is now approaching 10 micrometers. Complimentary time resolution of 30 fps or greater is also possible with a spatial resolution approaching 300 micrometers. Here we will provide an overview of the technique of neutron imaging and experimental studies with neutrons at the National Institute of Standards and Technology. Examples of in situ studies of fuel cells, hydrogen storage devices, heat pipes and batteries will be discussed.
Magnetic Nanocomposite Aerogels
Authors: Corrias Anna , Loche Danilo , Casula Maria F.
Published: September 2011

Aerogels are regarded as ideal candidates for the design of functional nanocomposites containing supported metal or metal oxide nanoparticles. The large specific surface area together with the open pore structure enables aerogels to effectively host finely dispersed nanoparticles up to the desired loading, to provide nanoparticle accessibility and/or to prevent nanoparticle agglomeration, as required to supply their specific functionalities.

The preparation of highly porous nanocomposite aerogels containing magnetic metal, alloy or metal oxide nanoparticles dispersed into amorphous silica, with high purity and homogeneity, was successfully achieved by a novel sol-gel procedure involving urea-assisted co-gelation of the precursor phases. This method allows fast gelation, giving rise to aerogels with 97% porosity, and it is very versatile allowing to vary composition, loading and average size of the nanoparticles.

The characterization of the morphological and structural features of the nanocomposite aerogels is carried out using different techniques, such as X-ray diffraction, Transmission Electron Microscopy and X-ray Absorption Spectroscopy. The characterization of the magnetic properties is carried out by SQUID magnetometry.
Automated Crystallite Orientation and Phase Mapping in a Transmission Electron Microscope
Authors: Rouvimov Sergei , Moeck Peter , Häusler Ines , Neumann Wolfgang , Nicolopoulos Stavros
Published: September 2011

An automated technique for the mapping of nanocrystal phases and orientations in a transmission electron microscope (TEM) is briefly described. It is primarily based on the projected reciprocal lattice geometry that is extracted automatically from precession electron diffraction (PED) enhanced spot patterns. The required hardware allows for a scanning-precession movement of the primary electron beam on the crystalline sample and can be interfaced to any newer or older mid-voltage TEM. Comprehensive open-access crystallographic databases that may be used in support of this technique are mentioned.
Improvement of Single-Junction a-Si:H Thin-Film Solar Cells Toward 10% Efficiency
Authors: Cheng P. H. , Liang S. W. , Lin Y. P. , Hsu H. J. , Hsu C. H. , Tsai C. C.
Published: September 2011

The hydrogenated amorphous silicon (a-Si:H) single-junction thin-film solar cells were fabricated on SnO2:F-coated glasses by plasma-enhanced chemical vapor deposition (PECVD) system. The boron-doped amorphous silicon carbide (a-SiC:H) was served as the window layer (p-layer) and the undoped a-SiC:H was used as a buffer layer (b-layer). The optimization of the p/b/i/n thin-films in a-Si:H solar cells have been carried out and discussed. Considering the effects of light absorption, electron-hole extraction and light-induced degradation, the thicknesses of p, b, n and i layers have been optimized. The optimal a-Si:H thin-film solar cell having an efficiency of 9.46% was achieved, with VOC=906 mV, JSC=14.42 mA/cm2 and FF=72.36%.
Numerical 3D-Simulation of Micromorph Silicon Thin Film Solar Cells
Authors: Geißendörfer Stefan , von Maydell Karsten , Agert Carsten
Published: September 2011

In this contribution 1, 2 and 3-dimensional simulations of micromorph silicon solar cells are presented. In order to simulate solar cells with rough interfaces, the surface topographies were measured via atomic force microscopy (AFM) and transferred into the commercial software Sentaurus TCAD (Synopsys). The model of the structure includes layer thicknesses and optoelectronic parameters like complex refractive index and defect structure. Results of the space resolved optical generation rates by using of the optical solver Raytracer are presented. The space resolved optical generation rate inside the semiconductor layers depends on the structure of the transparent conductive oxides (TCO) interface. In this contribution the influence of different optical generation rates on the electrical characteristics of the solar cell device are investigated. Furthermore, the optical and electrical results of the 1D, 2D and 3D structures, which have equal layer thicknesses and optoelectronic parameters, are compared.
Opto-electronic properties of co-deposited mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films
Authors: Kakalios James , Kortshagen U. , Blackwell C. , Anderson C. , Adjallah Y. , Wienkes L. R. , Bodurtha K. , Trask J.
Published: September 2011

Mixed-phase thin film materials, consisting of nanocrystalline semiconductors embedded within a bulk semiconductor or insulator, have been synthesized in a dual-chamber co-deposition system. A flow-through plasma reactor is employed to generate nanocrystalline particles, that are then injected into a second, capacitively-coupled plasma deposition system in which the surrounding semiconductor or insulating material is deposited. Raman spectroscopy, X-ray diffraction and high resolution TEM confirm the presence of nanocrystals homogenously embedded throughout the a-Si:H matrix. In undoped nc-Si within a-Si:H (a/nc-Si:H), the dark conductivity increases with crystal fraction, with the largest enhancement of several orders of magnitude observed when the nanocrystalline density corresponds to a crystalline fraction of 2 – 4%. These results are consistent with the nc donating electrons to the surrounding a-Si:H matrix without a corresponding increase in dangling bond density for these films. In contrast, charge transport in n-type doped a/nc-Si:H films is consistent with multi-phonon hopping, possibly through extended nanocrystallite clusters with weak electron-phonon coupling. The flexibility of the dual-chamber co-deposition process is demonstrated by the synthesis of mixed-phase thin films comprised of two distinct chemical species, such as germanium nanocrystallites embedded in a-Si:H and Si nanocrystallites embedded within an insulating a-SiNx:H film.
Calibration of multi-junction (tandem) thin film photovoltaic modules under natural sunlight
Authors: Tzamalis Georgios , Müllejans Harald
Published: September 2011

We present a procedure for calibrating tandem thin film photovoltaic modules under natural sunlight. The distinct steps involve pre-conditioning via light soaking, spectral response measurements and I-V measurements under natural sunlight. The measurements were done using a crystalline silicon reference cell as well as two filtered reference cells designed to spectrally match the top and bottom junctions in the tandem module.
PERFORMANCE of HYDROGENATED a-Si:H SOLAR CELLS with DOWNSHIFTING COATING
Authors: Nemeth Bill , Xu Yueqin , Wang Haorong , Sun Ted , Lee Benjamin G. , Duda Anna , Wang Qi
Published: September 2011

We apply a thin luminescent downshifting (LDS) coating to a hydrogenated amorphous Si (a-Si:H) solar cell and study the mechanism of possible current enhancement. The conversion material used in this study converts wavelengths below 400 nm to a narrow line around 615 nm. This material is coated on the front of the glass of the a-Si:H solar cell with a glass/TCO/p/i/n/Ag superstrate configuration. The initial efficiency of the solar cell without the LDS coating is above 9.0 % with open circuit voltage of 0.84 V. Typically, the spectral response below 400 nm of an a-Si:H solar cell is weaker than that at 615 nm. By converting ultraviolet (UV) light to red light, the solar cell will receive more red photons; therefore, solar cell performance is expected to improve. We observe evidence of downshifting in reflectance spectra. The cell Jsc decreases by 0.13 mA/cm2, and loss mechanisms are identified.
Modulated surface-textured substrates with high haze for thin-film silicon solar cells
Authors: Isabella O. , Liu P. , Bolman B. , Krč J. , Zeman M.
Published: September 2011

Modulated surface-textured substrates for thin-film silicon solar cells exhibiting high haze in a broad range of wavelengths were fabricated. Glass substrates coated with different thicknesses of a sacrificial layer were wet-etched allowing the manipulation of the surface morphology with surface roughness ranging from 200 nm up to 1000 nm. Subsequently, zinc-oxide layers were sputtered and then wet-etched constituting the final modulated textures. The morphological analysis of the substrates demonstrated the surface modulation, and the optical analysis revealed broad angle intensity distributions and high hazes. A small anti-reflective effect with respect to untreated glass was found for etched glass samples. The performance of solar cells on high-haze substrates was evaluated. The solar cells outperformed the reference cell fabricated on a randomly-textured zinc-oxide-coated flat glass. The trend in the efficiency resembled the increased surface roughness and the anti-reflective effect was confirmed also in solar cell devices.
N-Type Hydrogenated Microcrystalline Silicon Oxide Films and Their Applications in Micromorph Silicon Solar Cells
Authors: Limmanee Amornrat , Kittisontirak Songkiate , Piromjit Channarong , Sritharathikhun Jaran , Sriprapha Kobsak
Published: September 2011

We have prepared n-type hydrogenated microcrystalline silicon oxide films (n μc-SiO:H) and investigated their structural, electrical and optical properties. Raman spectra shows that, amorphous phase of the n μc-SiO:H films tends to increase when the CO2/SiH4 ratio increases from 0 to 0.28 resulting in a reduction of the crystalline volume fraction (Xc) from 70 to 12%. Optical bandgap (E04) becomes gradually wider while dark conductivity and refractive index (n) continuously drop with increasing CO2/SiH4 ratio. The n μc-SiO:H films have been practically applied as a n layer in top cell of a-SiO:H/μc-Si:H micromorph silicon solar cells. We found that, open circuit voltage (Voc) and fill factor (FF) of the cells gradually increased, while short circuit current density (Jsc) remained almost the same value with increasing CO2/SiH4 ratio for n top layer deposition up to 0.23. The highest initial cell efficiency of 10.7% is achieved at the CO2/SiH4 ratio of 0.23. The enhancement of the Voc is supposed to be due to a reduction of reverse bias at sub cell connection (n top/p bottom interface). An increase of shunt resistance (Rsh) which is caused by a better tunnel recombination junction contributes to the improvement in the FF. Quantum efficiency (QE) results indicate no difference between the cells using n top μc-SiO:H and the cells with n top μc-Si:H layers. These results reveal that, the n μc-SiO:H films in this study do not work as an intermediate reflector to enhance light scattering inside the solar cells, but mainly play a key role to allow ohmic and low resistive electrical connection between the two adjacent cells in the micromorph silicon solar cells.
Optical Demultiplexer Device: Frequency and optical bias analysis
Authors: Louro P. , Vieira M. , Vieira M. A. , Silva T.
Published: September 2011

In this paper we present results on the use of a multilayered a-SiC:H heterostructure as a device for wavelength-division demultiplexing of optical signals. This device is useful in optical communications applications that use the wavelength division multiplexing technique to encode multiple signals into the same transmission medium. The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photo generated carriers. Band gap engineering was used to adjust the photogeneration and recombination rates profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption and carrier collection in the visible spectrum. The photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. A demux algorithm based on the voltage controlled sensitivity of the device was proposed and tested. The operation frequency of the device was analyzed under different optical bias conditions. An electrical model of the WDM device is presented and supported by the solution of the respective circuit equations.
Influence of the Electrode Spacing on the Plasma Characteristics and Hydrogenated Amorphous Silicon Film Properties Grown in the DC Saddle Field PECVD System
Authors: Leong Keith R. , Kherani Nazir P. , Zukotynski Stefan
Published: September 2011

A new plasma deposition system was built with the capability of varying the electrode spacing in the DC Saddle Field plasma enhanced chemical vapor deposition system. An ion mass spectrometer was installed just below the substrate holder to sample the ion species travelling towards the substrate. Silane plasma and amorphous silicon film studies were conducted to shed light on the impinging ion species, ion energy distributions, and film properties with varying electrode spacing. The results indicate that decreasing the distance between the substrate and cathode leads to a reduction in the high energy ion bombardment.
Crack-free III-nitride structures (> 3.5 μm) on silicon
Authors: Tungare Mihir , Leathersich Jeffrey M. , Tripathi Neeraj , Suvarna Puneet , Shahedipour-Sandvik Fatemeh (Shadi) , Walsh Timothy A. , Tompkins Randy P. , Jones Kenneth A.
Published: September 2011

III-nitride structures on Si are of great technological importance due to the availability of large area, epi ready Si substrates and the ability to heterointegrate with mature silicon micro and nanoelectronics. High voltage, high power density, and high frequency attributes of GaN make the III-N on Si platform the most promising technology for next-generation power devices. However, the large lattice and thermal mismatch between GaN and Si (111) introduces a large density of dislocations and cracks in the epilayer. Cracking occurs along three equivalent {1−100} planes which limits the useable device area. Hence, efforts to obtain crack-free GaN on Si have been put forth with the most commonly reported technique being the insertion of low temperature (LT) AlN interlayers. However, these layers tend to further degrade the quality of the devices due to the poor quality of films grown at a lower temperature using metal organic chemical vapor deposition (MOCVD). Our substrate engineering technique shows a considerable improvement in the quality of 2 μm thick GaN on Si (111), with a simultaneous decrease in dislocations and cracks. Dislocation reduction by an order of magnitude and crack separation of > 1 mm has been achieved. Here we combine our method with step-graded AlGaN layers and LT AlN interlayers to obtain crack-free structures greater than 3.5 μm on 2” Si (111) substrates. A comparison of these film stacks before and after substrate engineering is done using atomic force microscopy (AFM) and optical microscopy. High electron mobility transistor (HEMT) devices developed on a systematic set of samples are tested to understand the effects of our technique in combination with crack reduction techniques. Although there is degradation in the quality upon the insertion of LT AlN interlayers, this degradation is less prominent in the stack grown on the engineered substrates. Also, this methodology enables a crack-free surface with the capability of growing thicker layers.
Fabrication and Optical Properties of Green emission semipolar {101̅1} InGaN/GaN MQWs Selective Grown on GaN Nanopyramid Arrays
Authors: Chang Shih-Pang , Chang Jet-Rung , Huang Ji-Kai , Li Jinchai , Chen Yi-Chen , Sou Kuok-Pan , Li Yun-Jing , Yang Hung-Chih , Hsu Ta-Cheng , Lu Tien-Chang , Kuo Hao-Chung , Chang Chun-Yen
Published: September 2011

We report that the high crystalline and high efficiency green emission semipolar {101̅1} InGaN/GaN multiple quantum wells (MQWs) grown on the {101̅1} facets of GaN nanopyramid arrays by selective area epitaxy. Clear and sharp interfaces of the semipolar {101̅1} InGaN/GaN MQWs was observed by transmission electron microscopy images. As comparing with (0001) MQWs, the internal electric field of {101̅1} MQWs was remarkably reduced from 1.7 MV/cm to 0.5 MV/cm, and the room temperature (RT) internal quantum efficiency (IQE) at green emission was enhanced by about 80%. This greatly enhancement of IQE is due to suppress the polarization effect in the {101̅1} MQWs which shorten the radiative recombination to compete with nonradiative recombination at RT. These results evince that the {101̅1} planes are promising for solving the efficiency green gap of III-nitride light emitters.
Research Highlights from the U.S. Department of Energy’s Working Group on Photoelectrochemical Hydrogen Production
Authors: Miller Eric L. , Garland Roxanne , Dillich Sara
Published: September 2011

The US Department of Energy (DOE) hydrogen production research and development portfolio focuses on low-cost, highly efficient and environmentally friendly production technologies based on diverse, domestic resources. Within the DOE, work on hydrogen production technologies integrates basic and applied research, as well as technology development and demonstration. The integration of basic and applied research is of particular importance in “transformational” production technologies, such as photoelectrochemical (PEC) hydrogen production, where scientific advances are needed for achieving the long-term DOE performance and cost targets. In the case of renewable hydrogen production via PEC solar water splitting, high solar-to-hydrogen conversion efficiency has been demonstrated to date on the laboratory scale, but only with high-cost, low-durability material systems. In order to identify and develop the appropriate high-efficiency, low-cost, durable and scalable PEC material systems, research and development efforts in the DOE EERE (Energy Efficiency and Renewable Energy) Office have keyed in on specific focus areas, including: 1) the engineering of solar energy absorption properties in PEC semiconductor materials, such as the bandgap lowering in stable metal oxides as well as bandgap raising in nanostructured sulfide catalysts; 2) the engineering of PEC solid-liquid interfaces for optimal reaction rates and stability, such as surface nitrogenation in III-V semiconductor systems; 3) the standardization of PEC measurement and reporting methodologies, using national and international peer-review process, for facilitating research progress; and 4) the design and analysis of integrated PEC device and system configurations for scalable hydrogen production. As described in this presentation, all of these research and development areas rely heavily on collaborative efforts among academia, industry and national laboratory partners, utilizing state of the art resources in materials theory, synthesis, characterization and analysis. The collaboration extends nationally among research programs supported by the DOE EERE as well as Office of Science; and internationally via networking through the International Energy Agency’s Hydrogen Implementation Agreement Annex-26. Key and encouraging accomplishments resulting from the collaborative work are highlighted in this presentation.
Costing out light source and product collection during evaluation of materials for renewable fuels
Authors: Palanivelu Karthikayini , Ramalingam Meenakshi , Ramanathan Ramnarayanan
Published: September 2011

We examined LEDs as a cheap and test lamp source to simulate monochromatic laser radiation to help us cost out optics while evaluating materials for renewable fuels. The light source spectrum was recorded using a fiber optic spectrophotometer and a calibrated silicon photodiode was used to determine the intensity. Photon flux from the LEDs was recorded using actinometry. We chose CdS and Fe3O4 as photocatalysts. The as-prepared and annealed samples were characterised using X-Ray Diffraction, UV-Visible spectroscopy, UV-Visible Diffuse reflectance spectroscopy, Fourier Transform Infra-red spectroscopy, Attenuated Total Reluctance -FTIR spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). CdS and Fe3O4 were evaluated for hydrogen evolution using DI water, sacrificial agents and an electron donor (methyl viologen) using three light sources (LEDs, sunlight and mercury vapour lamp). Products were collected by an inverted burette (Generation1), balloons with a B-14 adapter (Generation2) and septum cells (Generation3). Developing an analytical technique to quantify products continues to remain a challenge.
Growth and In-line Characterization of Silicon Nanodots Integrated in Discrete Charge Trapping Non-volatile Memories
Authors: Amouroux J. , Della Marca V. , Petit E. , Deleruyelle D. , Putero M. , Muller Ch. , Boivin P. , Jalaguier E. , Colonna J-P. , Maillot P. , Fares L.
Published: September 2011

Non-Volatile Memories (NVM) integrating silicon nanodots (noted SDs) are considered as an emerging solution to extend Flash memories downscaling. In this alternative memory technology, silicon nanocrystals act as discrete traps for injected charges.

Si-dots were grown by Low Pressure Chemical Vapor Deposition (LPCVD) on top of tunnel oxide. Depending on the pre-growth surface treatment, tunnel oxide surface may present either siloxane or silanol groups. SDs deposition relies on a 2–steps process: nucleation by SiH4 and selective growth with SiH2Cl2.

In a context of technological industrialization, it is of primary importance to develop in-line metrology tools dedicated to Si-dots growth process control. Hence, silicon-dots were observed in top view by using an in-line Critical Dimension Scanning Electron Microscopy CDSEM and their average size and density were extracted from image processing. In addition, Haze measurement, generally used for bare silicon surface characterization, was customized to quantify Si-dots deposition uniformity over the wafer. Finally, Haze value was correlated to Si nanodots density and size determined by CDSEM.
Matrix Density Effect on Morphology of Germanium Nanocrystals Embedded in Silicon Dioxide Thin Films
Authors: Alagoz Arif S. , Genisel Mustafa F. , Foss Steinar , Finstad Terje G. , Turan Rasit
Published: September 2011

Flash type electronic memories are the preferred format in code storage at complex programs running on fast processors and larger media files in portable electronics due to fast write/read operations, long rewrite life, high density and low cost of fabrication. Scaling limitations of top-down fabrication approaches can be overcome in next generation flash memories by replacing continuous floating gate with array of nanocrystals. Germanium (Ge) is a good candidate for nanocrystal based flash memories due its small band gap. In this work, we present effect of silicon dioxide (SiO2) host matrix density on Ge nanocrystals morphology. Low density Ge+SiO2 layers are deposited between high density SiO2 layers by using off-angle magnetron sputter deposition. After high temperature post-annealing, faceted and elongated Ge nanocrystals formation is observed in low density layers. Effects of Ge concentration and annealing temperature on nanocrystal morphology and mean size were investigated by using transmission electron microscopy. Positive correlation between stress development and nanocrystal size is observed at Raman spectroscopy measurements. We concluded that non-uniform stress distribution on nanocrystals during growth is responsible from faceted and elongated nanocrystal morphology.
Interface Characterization of Metals and Metal-nitrides to Phase Change Materials
Authors: Roy Deepu , Gravesteijn Dirk J. , Wolters Rob A. M.
Published: September 2011

We have investigated the interfacial contact properties of the CMOS compatible electrode materials W, TiW, Ta, TaN and TiN to doped-Sb2Te phase change material (PCM). This interface is characterized both in the amorphous and in the crystalline state of the doped-Sb2Te. The electrical nature of the interface is characterized by contact resistance measurements and is expressed in terms of specific interfacial contact resistance (ρC). These measurements are performed on four-terminal Kelvin Resistor test structures. Knowledge of the ρC is useful for selection of the electrode in the integration and optimization of the phase change memory cells.
Electro-forming of vacancy-doped metal-SrTiO3-metal structures
Authors: Hanzig Florian , Seibt Juliane , Stoecker Hartmut , Abendroth Barbara , Meyer Dirk C.
Published: September 2011

Resistance switching in metal – insulator - metal (MIM) structures with transition metal oxides as the insulator material is a promising concept for upcoming non-volatile memories. The electronic properties of transition metal oxides can be tailored in a wide range by doping and external fields. In this study SrTiO3 single crystals are subjected to high temperature vacuum annealing. The vacuum annealing introduces oxygen vacancies, which act as donor centers. MIM stacks are produced by physical vapor deposition of Au and Ti contacts on the front and rear face of the SrTiO3 crystal. The time dependent forming of the MIM stacks under an external voltage is investigated for crystals with varying bulk conductivities. For continued formation, the resistivity increases up to failure of the system where no current can be measured anymore and switching becomes impossible.
Manipulation of amorphous Ge2Sb2Te5 nano-structures in isolated and crystalline environment.
Authors: Mio A. M. , D’Arrigo G. , Carria E. , Bongiorno C. , Rossini S. , Spinella C. , Grimaldi M. G. , Rimini E.
Published: September 2011

We have investigated the stability of nano-amorphous region of Ge2Sb2Te5 (GST), fabricated by Electron Beam Lithography (EBL), dry etching, and ion implantation. Nano-structures, less than 100 nm in diameter and 20 nm thick, were either embedded in a crystalline environment or just isolated. We have observed nano-structure crystallization by in situ Transmission Electron Microscopy (TEM) in the 75°C-150°C temperature range. Re-crystallization of amorphous dots embedded in a crystalline region (either in the cubic or hexagonal phase) occurs by the movement of the interface at relatively low temperature (about 90°C). Instead, in the isolated structures the transition occurs at about 145°C by nucleation and growth. These results might be of relevance for the data retention of sub-50nm devices. Indeed, the more stable amorphous phase in self-standing regions indicates the better retention properties of isolated cells with respect to the traditional mushroom cell configuration.
Efficient near-infrared luminescence and energy transfer in Nd-Bi codoped zeolites
Authors: Bai Zhenhua , Fujii Minoru , Mori Yuki , Miwa Yuji , Mizuhata Minoru , Sun Hong-Tao , Hayashi Shinji
Published: September 2011

We prepare Nd-Bi codoped zeolites by a method consisting of a simple ion-exchange process and subsequent high-temperature annealing. The emission covers the range of 970∼1450 nm, corresponding to the electronic transitions of Nd3+ ions and Bi-related active centers (BiRAC), respectively. The introduction of Bi distinctly broadens the excitation band of Nd3+ in the visible region, and the lifetime of Nd3+ reaches as long as 354 μs. In the zeolite matrix, Bi ions exist as BiRAC and Bi oxide agglomerates. The former one act as a sensitizer of Nd3+ ions, and the latter one act as a blockage to avoid the quenching effect of coordinated water, which enable Nd3+ ions to show efficient near-infrared (NIR) emission even the zeolites contain large amount of coordinated water. The excellent optical and structural properties make these NIR emitting nanoparticles promising in application as laser materials and biological probes.
Photoluminescence of Eu-doped GaN
Authors: O’Donnell K.P.
Published: September 2011

This talk reviews work on the optical properties of Eu-doped GaN at the Semiconductor Spectroscopy laboratory of the University of Strathclyde. The principal experimental technique used has been lamp-based Photoluminescence/Excitation (PL/E) spectroscopy on samples produced mainly by high-energy ion implantation and annealing, either at low or high pressures of nitrogen, as described by Lorenz et al. [1]. These have been supplemented by samples doped in-situ either by Molecular Beam Epitaxy or Metallorganic Vapour Phase Epitaxy. Magneto-optic experiments on GaN:Eu were carried out in collaboration with the University of Bath.
Volumes de substratos comerciais, solo e composto orgânico afetando a formação de mudas de maracujazeiro-amarelo em diferentes ambientes de cultivo
Authors: Costa Edilson , Santos Léia Carla Rodrigues dos , Carvalho Cassia de , Leal Paulo Ademar Martins , Gomes Viviane do Amaral
Published: September 2011

Este trabalho teve como objetivo avaliar o crescimento de mudas de maracujazeiro- amarelo em três diferentes tamanhos de recipientes, em três condições de cultivo protegido, utilizando seis diferentes substratos. Foram empregados três ambientes de cultivo: (A1) estufa em arco, coberta de filme de polietileno de 150 μm, abertura zenital e tela termorrefletora de 50% sob o filme; (A2) viveiro agrícola de tela de monofilamento, com 50% de sombra; e (A3) viveiro agrícola de tela termorrefletora, com 50% de sombra. Foram testados três volumes (V1 = xx cm³ -sacolas de polietileno de 7,5 x 11,5 cm; V2 = xx cm33 - sacolas de polietileno 10,0 x 16,5 cm; e V3 = xx cm33 -sacolas de polietileno de 15,0 x 21,5 cm) e seis substratos (S1 = solo; S2 = Plantmax®; S3 = vermiculita; S4 = fibra de coco; S5 = fibra de coco chips; e S6 = Organosuper®, composto orgânico comercial). O delineamento experimental foi inteiramente casualizado, em esquema de parcelas subsubdivididas, em que os ambientes foram as parcelas, os recipientes de diferentes volumes as subparcelas e os substratos as subsubparcelas. Aos 50 dias após a semeadura, foram medidos a altura das plantas, o comprimento da raiz, a massa de matéria seca da parte aérea e das raízes. A partir das massas de matéria seca determinaram-se a relação massa de matéria seca de parte aérea e raiz e massa de matéria seca total. A estufa foi o melhor ambiente quando se utilizou o recipiente de XX cm33 o qual proporcionou mudas maiores, com maior biomassa seca aérea, radicular e total. A vermiculita foi o melhor substrato, porém o solo adubado é uma alternativa menos dispendiosa para a região.
Medidas radiométricas em casas de vegetação com cobertura plástica na região de Campinas - SP
Authors: Costa Edilson , Leal Paulo A. M.
Published: September 2011

Com o objetivo de caracterizar as relações e alterações radiométricas em três casas de vegetação, cobertas com filme transparente de polietileno de baixa densidade (PEBD) de camada simples com 150µm de espessura, tratado contra raios ultravioleta, sob ambientes distintos, foram realizados os experimentos durante o cultivo hidropônico de alface, cultivar Vera, na região de Campinas - SP, em diferentes períodos do ano, visando ao uso de dados experimentais de postos meteorológicos em substituição à necessidade de adquirir equipamentos de radiação para medições internas. As casas de vegetação eram de estrutura metálica de aço, de forma e volume idênticos. Coletaram-se a radiação solar global interna e externa (RSGI e RSGE, W m-2), a radiação fotossinteticamente ativa (RFA, µmol m-2 s-1) e a radiação ultravioleta, em 254; 312 e 365 nm (RUV, W m-2). Os resultados mostraram que as equações de regressão linear são estimativas aceitáveis na obtenção da radiação fotossinteticamente ativa em função da radiação solar global externa. Em ambientes fechados e climatizados, existe maior correlação entre a radiação fotossinteticamente ativa e a radiação solar global externa. A orientação das casas de vegetação não climatizadas não influencia no espalhamento interno da radiação fotossinteticamente ativa.
A dimensão pública da subjetividade em tempos de Orkut
Authors: Neves Carla , Portugal Francisco Teixeira
Published: September 2011

Partindo da presença garantida das novas tecnologias de comunicação na vida cotidiana, procura-se, no presente artigo investigar os efeitos subjetivos relacionados à comunidade online do Orkut e às experiências sociais contemporâneas. O trabalho estabelece um diálogo com os estudos de autores como Latour, Callon e Law, principalmente no que se refere ao conceito de rede sociotécnica ou de coletivo e à noção de mediação entendida como tradução, para, a partir daí, pensar os objetos técnicos como um dos muitos elementos que participam ativamente do processo de produção de diferentes modos de sociabilidade e de subjetivação. Por meio do levantamento e da análise das comunidades do Orkut que tem como temática o próprio site, procurou-se elucidar seus efeitos e deslocamentos, travando uma reflexão sobre o regime de visibilidade da subjetividade e o movimento atual de publicização de si.
O assédio moral no trabalho na visão de operadores do direito
Authors: Battistelli Bruna Moraes , Amazarray Mayte Raya , Koller Silvia Helena
Published: September 2011

Este estudo analisou a concepção de operadores do Direito acerca do assédio moral no trabalho, sua avaliação nas instâncias jurídicas, o perfil dos trabalhadores vitimados atendidos, assim como o papel do Direito e da Psicologia em relação ao fenômeno. Foram realizadas entrevistas semiestruturadas junto a seis operadores do Direito. Com base na análise de conteúdo das entrevistas, constatou-se uma tendência, entre os entrevistados, de perceberem a natureza organizacional do fenômeno. O medo dos trabalhadores em denunciar eventos dessa natureza foi outro elemento apontado. Os participantes afirmaram ser muito difícil avaliar e comprovar o assédio nos casos que recorrem às diferentes instâncias jurídicas. Quanto ao papel da Psicologia, os entrevistados referem sua importância para a produção de conhecimento, avaliação psicológica dos casos e prevenção da violência psicológica nas organizações. Em relação ao papel do Direito, reiteraram que as instâncias legais sejam espaços de garantia de direitos e reparação de danos.
Desvendando olhares: infância e AIDS nos discursos da sociedade
Authors: Calais Lara Brum de , Jesus Maria Ângela das Graças Santana de
Published: September 2011

O presente trabalho aborda a epidemia da Aids sob a perspectiva não somente de seu impacto biológico, como também social, tendo como principal foco as crianças infectadas pelo vírus HIV. Para tanto, contextualiza o percurso da epidemia, abordando a mudança de seu quadro no panorama mundial até chegar à infância. A partir de uma perspectiva histórica, analisa o conceito de infância e se atém principalmente aos aspectos psicossociais peculiares a essa infância "produzida" a partir do surgimento da epidemia. Baseada principalmente na teoria de Michel Foucault, aliada a aspectos específicos sobre Aids, procura identificar os discursos que envolvem essa infância, acreditando que estes têm poder de determinar lugares, mas também de realizar mudanças em nossa sociedade.
Caracterização dos serviços que atendem adolescentes: interfaces entre saúde mental e drogadição
Authors: Areco Nichollas Martins , Camila Alessandra Matias , Silva Rosalina Carvalho da , Simon Cristiane Paulin
Published: September 2011

A relação entre Estado e atendimento às demandas dos adolescentes sofreram mudanças históricas, tendo como importante marco a criação do Estatuto da Criança e do Adolescente (ECA). Analisamos, com enfoque qualitativo, como os serviços de saúde mental e drogadição de um município do Estado de São Paulo compreendem a demanda dos adolescentes em situação de vulnerabilidade social. As cinco instituições participantes informaram, por meio de questionários, as características dos serviços oferecidos e sua aproximação com a população atendida. Identificamos a fragmentação entre as ações públicas, havendo ora sobreposição de serviços, ora ausência desses, além do distanciamento das necessidades dos adolescentes, o que impossibilita que essas ações ofereçam elementos para que esse público mantenha uma relação positiva frente aos elementos vulnerabilizantes
Atitude político-ideológica e inserção social: fatores psicossociais do preconceito
Authors: Nunes Aline Vieira de Lima , Camino Leoncio
Published: September 2011

Neste estudo, objetivou-se verificar como se apresentam a atitude político-ideológica e a inserção social, no contexto universitário, frente ao preconceito sutil. Participaram 206 estudantes, 80% mulheres e idade média de 23 anos (DP=5,34), sendo heterogênea a divisão entre as áreas do conhecimento humano, saúde e educação. Foram utilizadas as escalas de inserção universitária, preconceito sutil e atitude favorável ao 1º e 3º mundos. Foi realizada ANOVA (Scheffé) entre as áreas do conhecimento e inserções, onde se verificou a promoção de inserções em diferentes atividades na universidade. Regressões (stepwise) constatam que as atitudes primeiro e terceiro mundistas são inversamente preditivas às inserções universitárias, assim como sua pertença às áreas, e que a inserção extracurricular prediz menor expressão de preconceito sutil. Infere-se que atitudes político-ideológicas atuam indiretamente no preconceito sutil, diferentemente da sua atuação mais direta frente à inserção social e ao antirracismo.