bluuebunny/crossref_metadata_2025 huggingface dataset:
Size-Dependent Quantum Efficiency of Luminescence in Self Assembled Germanium Nanocrystals
Authors: Lockwood David J. , Rowell Nelson , Berbezier Isabelle , Ronda Antoine
Published: September 2009

Self-assembled Ge nanocrystals (NCs), as verified from transmission electron microscopy and Raman spectroscopy, were formed by in-situ thermal annealing of a thin amorphous Ge layer deposited by molecular beam epitaxy on a thin SiO2 layer on Si(001). The Ge NCs were then capped in situ with a thin layer of amorphous Si to prevent oxidation. For samples with average NC diameters ranging from 2.5 to 60 nm, the NC photoluminescence (PL) appeared primarily as a wide near-infrared band peaked near 800 meV. Using both the k•p and tight binding theoretical models, we have analyzed the PL spectrum in terms of the NC size distribution required to reproduce the observed asymmetric band shape, which includes, for the smaller diameter NCs, a bandgap enlargement due to quantum confinement. The peak energy of the PL band reflects the average NC size and its shape depends on the NC size distribution. The observed size distribution determined from transmission electron microscopy analysis allowed the determination of the nonlinear increase in the PL quantum efficiency with decreasing NC diameter. Alternatively, given a good theoretical description of the system, it is thus possible to evaluate the size distribution of semiconductor NCs from their PL energy dependence.
Structural and Optical Properties of Electropolymerized Poly(para-phenylene)vinylene Films on Si and Porous Si
Authors: Djenizian Thierry , Gelloz Bernard , Dumur Frederic , Chassigneux C. , Koshida Nobuyoshi
Published: September 2009

Poly(para-phenylene)vinylene (PPV) was electrochemically deposited onto silicon and porous silicon substrates. The structures of the films were characterized by SEM and AFM. The PPV layers show good uniformity and flatness. Their emission properties were studied in term of photoluminescence and electroluminescence. The photoluminescence of PPV films is green and much stronger than that of the studied porous Si layers (emitting red color). The comparative study of the electroluminescence of Si/PPV/indium tin oxide and Si/PSi/indium tin oxide devices shows that charge carrier injection is achieved in the PPV film, but that it is more difficult than in porous Si.
Tuning Photoluminescence Properties of Alkaline-earth Oxide Nanoparticles by Site-selective Functionalization and Doping
Authors: Sushko Peter V. , McKenna Keith , Shluger Alexander , Diwald Oliver
Published: September 2009

We investigate theoretically the effects of isovalent substitutional doping on the optical properties of cubic MgO nanoparticles. The Ca, Sr, and Ba impurities preferentially occupy the three-coordinated cation sites and counterbalance the lattice strain induced by the finite size of the host particles. The lowest optical absorption band shifts to the lower energies as the radius of the substitutional species increases. Two types of nearly iso-energetic triplet excitons are found: the symmetric and asymmetric configurations correspond to the hole component being delocalized over three four-coordinated anion and localized on a single anion, respectively. The photoluminescence energies strongly depend on the exciton configuration and can be controlled by the judicious choice of the dopans.
The Luminescence Properties and Ce3+ → Tb3+ Energy Transfer of Ca3Y2(Si3O9)2
Authors: Chiu Yi-Chen , Liu Wei-Ren , Yeh Yao-Tsung , Jang Shyue-Ming , Chen Teng-Ming
Published: September 2009

Novel green-emitting phosphors of Ca3Y2(Si3O9)2:Ce3+,Tb3+ was successfully synthesized by solid-state reaction. Not merely the luminescence properties and energy transfer of Ca3Y2(Si3O9)2:Ce3+,Tb3+, the calculation of the energy transfer critical distance between Ce3+ and Tb3+ ions are also investigated in this work. By codoping Ce3+ into Ca3Y2(Si3O9)2:Tb3+, the emission intensity is dramatically enhanced by 5.8 times and the emission intensity is 126% as compared to that of ZnS:Cu,Al. We has been demonstrated that the energy transfer from Ce3+ to Tb3+ is a resonant type via dipole-dipole mechanism with the energy transfer critical distance of 6.78 Aå. The preliminary data demonstrate that the novel phosphor can emit blue to yellow-greenish under UV excitation and it exhibit the potential to act as UV convertible phosphor.
Measurement of Silicon Nanoparticle Concentration using Quartz Crystal Microgravimetry
Authors: Reipa Vytas , Choi Jonghoon H.
Published: September 2009

Various nano-scale items (nanoparticles, nanotubes, etc.) are actively investigated due to their unique physico-chemical properties. A common issue, encountered in such studies is accurate nanoparticle concentration expression, given the critical importance of the dose-response relationships. We present here the application of quartz crystal microgravimetry (QCM) to accurately measure Si nanoparticle concentration in a colloidal suspension. The QCM demonstrated a linear response for Si nanoparticle concentrations from 5 to 500 μg/ml. Our concentration estimates are compared with measurements derived from the TEM image analysis and optical absorbance. QCM concentration data was used to determine Si nanocrystal extinction coefficients for size selected samples.
Improvement of Light Extraction Efficiency in n-ZnO:Ga/i-ZnO/p-Si Heterojunction LED Using Truncated Pyramid Patterned Si Substrates
Authors: Kim Jae Hyun , Choi Mi Kyung , Seo Hong-Seok , Han Won Suk , Kim Young Yi , Kong Bo Hyun , Cho Hyung Koun , Lee Jung-Ho
Published: September 2009

n-ZnO:Ga/i-ZnO/p-Si heterojunction light-emitting diodes (LEDs) were fabricated using patterned Si substrates having larger junction area than normal flat ones where recombined photons are generated. The patterned p-type Si substrates were prepared by anodization which is very cost competitive method, and the n-type ZnO:Ga films were deposited by high-temperature sputtering. The truncated patterning of the substrates resulted in approximately 75 % improvement in output power compared with the LED without the pattern, which was attributed to a 1.33-fold increase in the junction area through patterning.
Synthesis and Characterization of Flower-like Au Doped MoS2
Authors: Liang Ching-Huei , Hu Sheng-Yao , Chan Yi-Hao , Wang Szu-Kai , Tiong Kwong-Kau , Huang Ying-Sheng
Published: September 2009

Single crystals of flower-like Au-doped MoS2 were grown using the chemical vapor transport (CVT) method with I2 as a transport agent. X-ray photoelectron spectroscopy showed a slight down shift of the Mo 3d and S 2p binding energies as a result of doping with Au. Field-emission scanning electron microscopy and high resolution transmission electron microscopy showed foliate morphology and single crystalline structure for the synthesized Au-MoS2. Room temperature Hall effect measurement indicated p-type semiconducting character for the sample. The optical transmittance measurements revealed that Au-doped MoS2 is an indirect semiconductor.
Luminescence Properties of YAG:Ce3+ Nanophosphors Prepared by Flame Spray Pyrolysis
Authors: Lee Jae Seok , Gupta Sushant , Oh Myounghwan , Ranade Madhav B. , Singh Rajiv K.
Published: September 2009

Among the various types of synthesis techniques for phosphors, flame spray pyrolysis (FSP) is a powerful method which is capable of producing particles with good crystallinity and high luminescence efficiency. In this work, we have investigated the influence of the addition of urea and the molar ratio of yttrium to aluminum in the liquid precursor on crystallinity and luminescence properties of YAG:Ce3+ nanophosphors prepared by flame spray pyrolysis (FSP) were comparatively studied. The heat-treated phosphor particles are spherical shape with an average size blow 50 nm. For FSP, the crystallinity of YAG:Ce3+ nanophosphors improved with addition of urea and overloaded aluminum in starting liquid precursor. As a result of XRD result, the nanophosphors from urea-added and slight excess of aluminum in liquid precursor presents higher luminescence intensity than those of from non-urea and less aluminum.
Partial Nitridation of Sr3Al10SiO20:Eu and Its Effect on Photoluminescence Properties
Authors: Matsuo Hitoshi , Mikami Masayoshi , Yamamoto Hajime , Imura Hiroyuki , Uheda Kyota , Kijima Naoto
Published: September 2009

The first principle calculation and Pauling's second rule predicted that an O2- ion coordinated with two Al3+ and one Si4+, or Si4+-O[3]-2Al3+, is stabilized by cross-substitution to form 2Si4+-N[3]-Al3+ configuration. Motivated by this idea, this work has attempted to synthesize a new phosphor by partial nitridation of Sr3Al10SiO20:Eu2+, which contains one set of Si4+-O[3]-2Al3+ per 20 O2- ions. Synthesis condition of Sr3Al10-xSi1+xO20-xNx:Eu2+ with x=1 was investigated by variation of Si3N4/SiO2 ratio in the starting materials. Neutron diffraction analysis has shown that nitridation as much as x=0.6-2 was attained by supply of Si3N4 in excess of the stoichiometry, because Si3N4 is partly oxidized even by firing in reduced atmosphere. Luminescence intensity is increased by 7 times at the best by the nitridation, though little change is observed in luminescence spectra and X-ray diffraction patterns. The increased luminescence intensity results mainly from more efficient reduction of Eu3+ by Si3N4.
Preparation of High-luminance SrGa2S2:Eu Thin Film Phosphors by Laser Annealing
Authors: Kominami Hiroko , Nakanishi Yoichiro , Terada K. , Yamasaki Takahisa , Seino Toshiaki , Hara Kazuhiko
Published: September 2009

Preparation of green-emitting SrGa2S4:Eu thin film phosphors by low temperature process at lower than 600oC under an assist with a laser annealing technique after the deposition was investigated. It was shown that the crystallinity and emission intensity of the SrGa2S4:Eu film annealed at 500oC were improved considerably by the assist with laser annealing using KrF excimer laser. As a result, the film showed cathodoluminescent (CL) luminance of about 2,000 cd/m2 under excitation with 5kV and 60uA/cm2. It was found from these results indicate that the laser annealing technique assists the improvement of both structural and luminescent properties.
A Step Forward Towards Smart White Lighting: Combination of Glass Phosphor and Blue LEDs
Authors: Andrade Luis , Lima Sandro , Novatski Andressa , Steimacher Alysson , Neto Antônio , Bento Antônio , Baesso Mauro , Guyot Yannick , Boulon Georges
Published: September 2009

We report a broad and intense yellow emission band from Ce3+-doped Low Silica Calcium Aluminosilicate (LSCAS) glass obtained under blue light excitation. The CIE 1931 x-y chromatic diagram shows that the association of the Ce3+:LSCAS glass with 405 nm blue LED presents emission very close to the ideal white light position.
Photoluminescence Study of Diffusion and Reactions of 18O-labeled Interstitial Oxygen Molecules in Amorphous SiO2
Authors: Kajihara Koichi , Miura Taisuke , Kamioka Hayato , Hirano Masahiro , Skuja Linards , Hosono Hideo
Published: September 2009

A photoluminescence (PL) method to evaluate the concentration and isotopic fraction of 18O-labeled oxygen molecules (O2) dissolved in interstitial voids in amorphous SiO2 (a-SiO2) was developed. This method utilizes laser-induced infrared PL bands of interstitial O2 attributed to the transition from the first excited singlet state, in particular, the vibrational sideband coupled to the O-O stretching mode. From the variation of the concentration and isotopic fraction of interstitial O2 with time and temperature of thermal annealing under an 16O2 or 18O2 atmosphere, the diffusion of interstitial O2 as well as the rate of oxygen exchange between interstitial O2 and the Si-O network were examined directly and quantitatively. This observation provides clear experimental evidence that the main oxygen transport mechanism in a-SiO2 is the permeation of interstitial O2.
Advances in Solid-State Laser Materials
Authors: Huber Guenter
Published: September 2009

We review the spectroscopic properties and performance of laser materials doped with Pr3+ and Yb3+ ions emitting in the visible and near infrared spectral region, respectively. With Yb3+:Lu2O3 high slope efficiencies (~ 80 %) have been obtained. GaN-diode-pumped Pr-lasers offer compact and efficient set-ups for the generation of visible and ultraviolet continuous wave laser radiation.
Electroluminescence in Metal-Oxide-Semiconductor Tunneling Diodes with Ultra Thin Silicon
Authors: Matsumura Kei , Yamada Ryuta , Arima Kenta , Uchikoshi Junichi , Morita Mizuho
Published: September 2009

Electroluminescence characteristics of a metal-oxide-semiconductor tunneling diode on a silicon-on-insulator wafer have been studied. The spectrum from the diode is peaked at 1050 nm (1.18 eV) and at 1145 nm (1.08 eV). The spectrum from the diode on a silicon wafer is peaked at 1145 nm. The peak at 1145 nm can be assigned as phonon-assisted indirect transitions. It is indicated that the peak at 1050 nm is due to the quantum confinement in an ultra thin silicon layer.
Metal - Semiconductor Nanoassemblies for Improving of Sensing Efficiency
Authors: Miu Mihaela , Kleps Irina , Craciunoiu Florea , Ignat Teodora , Simion Monica , Dinescu Adrian , Bragaru Adina , Danila Mihai
Published: September 2009

In the nanometer size regime, both semiconductor and noble metal nanostructures have many interesting optical, electronic and chemical properties that are size-dependent, due to quantum effects. The hybrid nanoassemblies obtained from putting them together become suitable for applications in developing biological nanosensors and optoelectronic nanodevices with significant enhancement of sensing efficiency.
Electrochemical Reduction Synthesis of Photoluminescent Silicon Nanocrystals
Authors: Reipa Vytas , Choi Jonghoon H.
Published: September 2009

An efficient synthesizing procedure of photoluminescent silicon nanocrystals is demonstrated using ultrasound assisted electrochemical octyltrichlorosilane reduction that produces alkyl terminated Si nanocrystals in a single step. The described procedure allows to make Si nanocrystals with octyl surface termination, is clean, relatively simple, and potentially scalable to industrial quantities. High resolution transmission electron microscopy, powder X-ray diffraction, UV-VIS absorbance, Fourier transform infra red spectroscopy and photoluminescence spectroscopy are employed to characterize the synthesized photoluminescent Si nanocrystals. Resulting octyl termination provides a stable passivation and could serve as a platform for further particle functionalization.
Fabrication and Properties of Au Nanoflowers for SERS Substrates
Authors: Krishnan Jegatha Nambi N. , Kim In Tae , Ahn Sung-Hyun , Kim Zee Hwan , Kim Sang Kyung K.
Published: September 2009

This paper reports a simple, template-free and cost effective method for the fabrication of Au nanoflowers and nanostructures with high yield. The key synthesis strategy was to use a KAuCN2 solution and a variety of metals (Pt, Ag and Cu etc) deposited on the Si substrate using e-beam evaporation. The Au nanostructures differ with respect to each metal that has been deposited onto the substrate. The surface properties of Au nanostructures formed on different metallic substrates were investigated by XPS measurements. Time course measurements by SEM were used to follow the reaction progress and the evolution of the flower-like shape. Such Au nanoflowers and nanostructures exhibited strong surface-enhanced effects which could be used in the design of efficient, stable and nontoxic Raman-active substrates for biosensing applications.
Tunable Electrochemical Switch of the Optical Properties of Metallic Nanoparticles
Authors: Leroux Yann , Lacroix Jean Christophe , Stockhausen Verena , Fave Claire , Felidj Nordin , Grand Johan , Hohenau Andreas , Krenn Joachim
Published: September 2009

Control of the optical properties of metallic nanoparticles (NP) is realized using an electrochemical switch consisting of a thin layer of conducting polymer (CP). Reversible modulation and almost total quenching of the localized surface plasmon resonance(LSPR) is achieved as a function of the thickness of the CP layer and the potential applied to the electrochemical systems, i.e. the charge carrier density injected into the CP layer. The quenching of LSP also depends of the frequency of the LSPR. This effect is attributed to the variation of the CP dielectric function with wavelength. As a consequence, prolate arrays show total quenching of the LSPR along the major axis of the particles whereas modulation and moderate damping are observed along the minor axis. We believe that combining an electroactive conducting polymer and NP will prove to be a general strategy for controlling the properties of various types of NP (fluorescent, magnetic, semiconducting).
Performance Degradation of P3HT:PCBM Polymer/Fullerene Photovoltaic Cells Under Gamma Irradiation
Authors: Todd Aaron , Zhu Ting , Zhang Fan , Zhang Chunfeng , Berger Alan , Xu Jian
Published: September 2009

Organic photovoltaic cells are being considered for space applications due to the ease of fabrication, low production cost, and the potential to be used on flexible substrates. However, space-bound cells are exposed to high levels of radiation when orbiting the Earth. In this ongoing study, we examine the performance of P3HT:PCBM photovoltaic cells after exposure to gamma radiation from a cesium-137 source (662 keV). Preliminary results show degradation of the device I-V characteristics with radiation doses up to 5 krad. The integral mode time of flight (I-TOF) technique and current extraction by a linearly increasing voltage (CELIV) technique will be used to study the electron mobility and carrier lifetime properties as a function of the radiation dose. We speculate that main chain scission and reduced π-conjugation of P3HT are the dominant mechanisms responsible for performance degradation.
Preparation of Ni Oxyhydroxide Thin Films by Reactive Sputtering in H2O Atmosphere and Their Electrochromic Properties
Authors: Abe Yoshio , Ueta Hideaki , Obata Takeshi , Kawamura Midori , Sasaki Katsutaka , Itoh Hidenobu
Published: September 2009

Ni oxyhydroxide (NiOOH) thin films were prepared by reactive sputtering in an atmosphere of H2O gas, and effects of sputtering gas pressure on their electrochromic properties were studied. The largest optical density change was obtained for the thin films deposited under high sputtering pressures of around 50 mTorr because of their low film density and chemical composition close to NiOOH.
Tungsten Oxide Electrochromic Windows with Lithium Polymer Electrolytes
Authors: Sequeira Cesar A. , Santos Diogo M.
Published: September 2009

Electrochromic windows are built using WO3 as the electrochromic material and V2O5 as the counter electrode. Both are deposited onto ITO coated glass panes by vacuum evaporation and are amorphous to X-ray diffraction. The electrolytes are lithium conducting polymers constituted by diallyl amide by-product DaaRfSO3Li, (CH2=CH-CH2)2NCO-CF(CF3)SO3Li grafted in a cross-linked polyether NPC1000 (network poly(isobuthenyloligooxyethylene)), with a tLi+ close to unity, and poly(ethyleneglycol)-borate ester with LiCF3SO3, with a tLi+ close to 0.34. The electrochemical characterization of the electrodes is carried out by cyclic voltammetry, coulometric titration, and impedance spectroscopy, allowing the determination of the chemical diffusion coefficients of lithium into WO3 and V2O5. Potentiostatic cycling of the complete transmissive cells yield a transmission variation from 48% to 12% at ~630 nm with a response time of 10 seconds at room temperature. The main drawbacks are the residual coloration in the bleached state and the low exchange current densities at room temperature, which underline the need for good electrolyte/electrode contacts.
Noble-Metal Covered W(111) Single-Atom Electron Sources
Authors: Hwang Ing-Shouh , Kuo Hong-Shi , Chang Che-Cheng , Tsong Tien T.
Published: September 2009

Single-atom tips can be used as ideal point sources of electron beams. It has been shown that noble-metal covered W(111) single-atom tips can be reliably prepared and their lifetimes are long enough for real applications. These tips are both thermally and chemically stable, and can be regenerated in vacuum when accidentally damaged or contaminated. The atomic stacking remains the same each time it is regenerated. The small opening angle, smallest emitting area, high brightness, high spatial coherence, and high stability of these single-atom electron sources make them highly desirable for many applications. Both the brightness and spatial coherency of these electron sources are orders of magnitude better than those of the state-of-the-art electron sources used in electron microscopes. Application of these sources may significantly improve the performance and expand the capabilities of current electron microscopes, and open up many new possibilities in electron-beam based techniques.
Growth of Large Transparent and Conducting Graphene Sheets Using Chemical Vapor Deposition
Authors: Park Hye Jin , Skakalova Viera , Meyer Jannik , Roth S. , Von Klitzing Klaus
Published: September 2009

Growth and various properties of chemical vapor deposition (CVD) grown grapheme were studied. The graphene was synthesized on Ni coated SiO2/Si substrate using CH4 and H2 gases at 1000oC. The samples were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, UV/Vis/IR spectroscopy, optical microscopy and 4-probe electrical measurements before or after transferring samples onto arbitrary substrates such as quartz glass, KBr, Si wafer, and polycarbonate (PC) film. Raman spectra proved that samples consist of from one to five graphene layers. TEM images confirmed the results of Raman analysis. A large part of the samples was formed by a highly crystalline single layer. The other parts consisted of multilayer domains where crystal boundaries were clearly visible in atomic resolution scale.
The Growth of Semiconductor and Dielectric Nanowires and Nanowire Arrays and their Plasmonic Applications.
Authors: Prokes S.M. , Glembocki Orest J. , Mazeina Lena , Alexson Dimitri A , Park Hyun D. , Qi Hua , Rendell Ronald
Published: September 2009

We have investigated the growth of a number of nanowire systems, including Ga2O3, ZnO, InAs, as well as Ga2O3/ZnO hierarchical structures and dielectric core/metal sheath composites. We show that the growth of nanowires can occur by a number of growth mechanisms, even in the same system, and how this process can be tailored for specific applications, including plasmonics. We will show that dielectric/metal composite nanowires can exhibit very strong surface enhanced Raman (SERS) signals, when arranged in a random 3D geometry, which is due to nanowire crossings, and we will show the effects of crossing geometries on the strength of the SERS signal, which is compared with electric field calculations.
Facet Specific Gold Tip Growth on Semiconductor Nanorods
Authors: O'Sullivan Catriona , Gunning Robert , Barrett Christopher , Singh Ajay , Geaney Hugh , Sanyal Ambarish , Ahmed Shafaat , Bala Tanu , Ryan Kevin
Published: September 2009

High quality CdS-Au and CdSe-Au hybrid nanocrystals have been developed via facile approaches. Gold tip growth onto II-VI nanorods has been shown to occur instantaneously both via a solution and spin cast method. Gold tip size and multiplicity can be varied by changing the starting gold chloride concentration or the reaction duration. Gold tip growth typically occurs at one end of the nanorod, however we recently observed that a variation in the reaction temperature leads to the growth of a tip on both ends of the nanorod. TEM analysis showed that the gold tip growth does not always occur centrosymmetrically on the rod tip, with growth occurring on either the (001) or the (101) facet depending on the respective sizes. Spin coating gold chloride solution onto a pre-deposited perpendicular oriented array of nanorods leads to individual gold growth at the tips of each nanorod.
Au Free Ohmic Contacts for High Temperature InAlN/GaN HEMT's
Authors: Alomari Mohammed , Maier David , Carlin Jean-Francois , Grandjean Nicolas , Poisson Marie-Antoinette , Delage Sylvain , Kohn E.
Published: September 2009

In this paper we report on the fabrication of Au free ohmic contacts, with a contact resistance down to 0.46 Ωmm. The contact resistance and thermal stability was evaluated up to 1000oC in vacuum. No degradation of the ohmic contact was observed after cooling down to room temperature.
Enhanced Vertical Emission from GaN Based Light Emitting Diode with ZnO Nanorod Arrays Produced by Hydrothermal Method
Authors: Dalui Saikat , Lin Chih-Chien , Lee Hsin-Ying , Lee Ching-Ting
Published: September 2009

In this study, we analyzed the modulated light output from the GaN based light emitting diodes (LEDs) with the incorporation of ZnO nanorod by hydrothermal method. With the ZnO nanorod, the light output from the LEDs increased by 20.2% at an injection current of 100mA and more interestingly, output power was more concentrated in a smaller escape cone of~ θ=30o than that of conventional LEDs with a cone of ~ θ=42o. Surface damaging of LEDs was also avoided by the low temperature hydrothermal growth of ZnO nanorod arrays which was evident as there was no significant change in I-V characteristics for both the cases.
Electron-beam Evaporation of Distinctive Indium-tin-oxide Nanorods for Enhanced Light Extraction from InGaN/GaN Light Emitting Diodes
Authors: Chiu ChingHua , Yu Peichen , Tsai M.A. , Kuo H.C.
Published: September 2009

In this paper, we present a novel and mass-producible technique to fabricate indium-tin-oxide (ITO) nanorods arrays on InGaN/GaN light emitting diodes (LEDs) surface to be served as an omnidirectional transparent conductive layer. The characteristics nanorods, prepared by the electron-beam evaporation with an obliquely incident nitrogen flux on an ITO glass, demonstrate high optical transmittance (T>95%) for a broad wavelength ranging from 350 to 900 nm. The light output power of an InGaN/GaN LED with incorporated ITO nanorods increases by 35.1 % at an injection current of 350 mA, compared to a conventional LED. The higher efficiency is attributed to the better transmission and gradient refractive index resulted from the fabricated ITO nanorod on the surface.
SiC Power Device Technology - Differences to Silicon and Their Influence on Device Processing and Performance
Authors: Friedrichs Peter
Published: September 2009

The paper summarizes important challenges in manufacturing silicon carbide based power devices on an industrial scale. Special emphasize is paid to processes which differ considerably from well know silicon power device process flows and processing conditions. In general, higher temperatures used in the processing of silicon carbide devices represent a challenge for both, equipment manufacturers and device design experts. The main topics discussed in the contribution are processes for annealing ion implanted species, the formation of ohmic contacts as well as the crucial question of forming high quality interfaces between SiC and insulating materials for MOS based power devices structures. Finally, progress will be presented how to suppress the forward drift effects in silicon carbide high voltage bipolar devices in order to open up a commercial future for this device family.
Multiple Heterostructures of Ni2Si/Si Formed by the Point Contact Reaction
Authors: Ouyang Hao , Cheng Ming-Ting , Shiu Yung-Ruei , Lo Shen-Chuan , Wu Wen-Wei , Chen S.Y. , Chen Lih-Juann
Published: September 2009

The high quality multiple heterostructures of Ni2Si/Si in a nanowire of Si can be formed by using the point contact reaction between several Ni nanodots and a Si nanowire carried out in-situ in an ultrahigh vacuum transmission electron microscopy. The fabricated multi-nano-heterostructures may enhance the development of circuit elements in nano-scale electronic devices. The unusual tetragonal Ni2Si (I4/mcm) phase rather than the commonly observed HCP Ni2Si (P63/m) was identified in the multiple heterostructures of Ni2Si/Si with the existence of surface oxide. The corresponding electronic structure and kinetic paths of phase transformations will be simulated and discussed.
Ultra-thin SOI Layer Nanostructuring and Nanowire Transistor Formation for FemtoMole Electronic Biosensors
Authors: Naumova Olga , Popov Vladimir P. , Safronov Leonid , Fomin Boris , Nasimov Dmitry , Latyshev Alexander , Aseev Alexander , Ivanov Yury , Archakov Alexander
Published: September 2009

In this work nanostructuring of SOI layers with tenth nanometer thickness was made at last stage of electronic biochip producing using fluorine gas-plasma content etching. Electrical characterization verities that used fabrication approach produces high-quality devices operating up to temperatures close to liquid helium. The sensitivity of SOI NWs to negative ions Cl- in aqua solution (pH 6) was shown to be as high as 10 femtoMoles. The sensitivity of SOI NWs to negative protein BSA molecules in pH 7.4 buffer solution was shown to be as high as 1 femtoMoles.
Synapse Plasticity in Motor, Sensory, and Limbo-Prefrontal Cortex Areas as Measured by Degrading Axon Terminals in an Environment Model of Gerbils (Meriones unguiculatus)
Authors: Neufeld Janina , Teuchert-Noodt Gertraud , Grafen Keren , Winter York , Witte A. Veronica
Published: September 2009

Still little is known about naturally occurring synaptogenesis in the adult neocortex and related impacts of epigenetic influences. We therefore investigated (pre)synaptic plasticity in various cortices of adult rodents, visualized by secondary lysosome accumulations (LA) in remodeling axon terminals. Twenty-two male gerbils from either enriched (ER) or impoverished rearing (IR) were used for quantification of silver-stained LA. ER-animals showed rather low LA densities in most primary fields, whereas barrel and secondary/associative cortices exhibited higher densities and layer-specific differences. In IR-animals, these differences were evened out or even inverted. Basic plastic capacities might be linked with remodeling of local intrinsic circuits in the context of cortical map adaptation in both IR- and ER-animals. Frequently described disturbances due to IR in multiple corticocortical and extracortical afferent systems, including the mesocortical dopamine projection, might have led to maladaptations in the plastic capacities of prefronto-limbic areas, as indicated by different LA densities in IR- compared with ER-animals.
Construction Solutions of PDE in Parametric Form
Authors: Volosova Alexandra K. , Volosov Konstantin Alexandrovich
Published: September 2009

The new important property of wide class PDE was found solely by K. A. Volosov. We make an arbitrary replacement of variables. In the case of two independent variables x, t, then it always gives
the possibility of expressing all PDE second and more order as AX = b. This is a linear algebraic equations system with regards
derivatives to old variables x(ξ, δ), t(ξ, δ) on new variables . This
system has the unique solution. In the case of three and more independent variables
x, y, t, …, then it gives the possibility of expressing PDE second order as
AX = b, if we do same compliment proposes. In the present paper, we suggest a new method for constructing closed
formulas for exact solutions of PDE, then support on this important new
property.
ABO Incompatible Liver Transplantation as a Bridge to Treat HELLP Syndrome
Authors: Connor Kathleen , Rubin Raymond A. , Shrestha Roshan , Johnson Mark , Sellers Marty , Butler Brad
Published: September 2009

The following is a case report of a primiparous woman who developed fulminant liver failure in the setting of HELLP syndrome complicated by hepatic rupture. It is unique in that a timely ABO compatible liver donor was unavailable, necessitating the transplantation of an ABO incompatible organ. Despite aggressive therapy,severe reperfusion injuryand humoral rejection dictated retransplantation with an ABO compatible organon postoperative day 15, resulting in rapid clinical recovery.
Pediatric Inflammatory Bowel Disease: Is It Different?
Authors: Levine Arie
Published: September 2009

The clinical manifestations of Crohn’s disease (CD) and ulcerative colitis (UC) are highly variable, with significant diversity in phenotypes of the diseases. This diversity may manifest as a difference in age of onset. Pediatric-onset disease may present differently and have a different natural history, with ramifications for disease management. Clear evidence exists at present that pediatric-onset UC may be different than adult-onset UC. The primary difference in disease phenotype is extent of disease. Approximately 60–70% of patients with pediatric-onset UC present with pancolitis, as opposed to approximately 20–30% in adults. Patients are more likely to have severe disease and become steroid-dependent. CD may be affected by an age gradient. There is an inverse linear relationship between age and colonic CD, the younger the patient, the more likely is the patient to have colonic CD. This inverse relationship is true through age 10. In addition, pediatric patients are more likely to have upper gastrointestinal involvement than their adult peers. Comparing adult and pediatric phenotypes is fraught with methodological obstacles. Disease behavior, with the exception of growth failure, seems to parallel disease behavior in adults. Patients with growth retardation are a high risk group for complications and should be managed as such.
Environmental Factors Affecting Inflammatory Bowel Disease: Have We Made Progress?
Authors: Lakatos Peter Laszlo
Published: September 2009

The pathogenesis of inflammatory bowel disease (IBD) is only partially understood; various environmental and host (e.g. genetic, epithelial, immune, and nonimmune) factors are involved. The critical role for environmental factors is strongly supported by recent worldwide trends in IBD epidemiology. One important environmental factor is smoking. A meta-analysis partially confirms previous findings that smoking was found to be protective against ulcerative colitis and, after the onset of the disease, might improve its course, decreasing the need for colectomy. In contrast, smoking increases the risk of developing Crohn’s disease and aggravates its course. The history of IBD is dotted by cyclic reports on the isolation of specific infectious agents responsible for Crohn’s disease or ulcerative colitis. The more recently published cold chain hypothesis is providing an even broader platform by linking dietary factors and microbial agents. An additional, recent theory has suggested a breakdown in the balance between putative species of ‘protective’ versus ‘harmful’ intestinal bacteria – this concept has been termed dysbiosis resulting in decreased bacterial diversity. Other factors such as oral contraceptive use, appendectomy, dietary factors (e.g. refined sugar, fat, and fast food), perinatal events, and childhood infections have also been associated with both diseases, but their role is more controversial. Nonetheless, there is no doubt that economic development, leading to improved hygiene and other changes in lifestyle (‘westernized lifestyle’) may play a role in the increase in IBD. This review article focuses on the role of environmental factors in the pathogenesis and progression of IBDs.
Links between Autophagy, Innate Immunity, Inflammation and Crohn’s Disease
Authors: Deretic Vojo
Published: September 2009

Autophagy is a fundamental biological process that endows eukaryotic cells with the ability to autodigest portions of their own cytoplasm. Autophagy plays roles in aging, development, neurodegeneration, cancer and immunity. The immunological role of autophagy was first recognized for the ability of autophagy to sanitize the cellular interior by killing intracellular microbes and, indirectly, by the adaptations that successful intracellular pathogens have evolved to protect themselves from autophagy. Since then, the repertoire of autophagy functions in immunity has been vastly expanded to include numerous intersections of regulatory and effector nature with innate and adaptive immunity. Autophagy acts both as an effector and a regulator of pattern recognition receptors, it supports MHC II presentation of cytosolic (self and microbial) antigens, it shapes central tolerance via thymic selection of the T cell repertoire, is an effector of Th1/Th2 polarization, affects homeostasis of T, B, and specialized immune cells such as Paneth cells, and – when defective – can be a contributing factor to chronic inflammatory conditions in human populations such as Crohn’s disease.
Risk of Radiation and Choice of Imaging
Authors: Herfarth Hans , Palmer Lena
Published: September 2009

Radiological imaging plays an important role in the diagnosis and management of patients with inflammatory bowel diseases (IBD). The barium or contrast techniques enteroclysis (SBE) and small bowel follow through (SBFT) are still the mainstays in small bowel imaging. However, abdominal CT and MRI, including enteroclysis, have comparable sensitivity and specificity in detecting intestinal pathologies and have gained in popularity over conventional techniques. The cancer risk associated with diagnostic procedures employing radiation has been receiving increasing attention over the last few years. The cumulative exposure to ionizing radiation may be a specific concern in young patients with IBD, who are more susceptible than adults to the risks of ionizing radiation. Substantial exposure to radiation seems to be mainly caused by CT examinations of the abdomen. For that reason, imaging methods such as MRI or ultrasound should be considered first when debating between alternative imaging strategies, particularly in young IBD patients. The major drawbacks of MRI are its limited availability and greater costs compared to CT. Moreover, the diagnostic accuracy of abdominal ultrasound is clearly operator dependent, which limits the range of its applications. In light of these concerns, diagnostic imaging studies using radiation will continue to play an important role in the evaluation of patients with IBD. Therefore, we need to develop low-radiation imaging protocols or improve access to MRI imaging procedures. We also need to identify subsets of IBD patients who are at greater risk of a significant lifetime exposure to radiation and develop methods to monitor their radiation exposure rate.
Enteral Nutrition Should Be Used to Induce Remission in Childhood Crohn’s Disease
Authors: Heuschkel Robert
Published: September 2009

Background: Exclusive enteral nutrition has been used over many years as a therapy to try and achieve a remission in adults and children presenting with acute Crohn’s disease. Despite its reported efficacy at achieving clinical responses in excess of 80% in some case series, it has not been taken up widely as a first-line therapy. This is, at least in part, due to the lack of a large prospective randomised study. Methods: The literature is replete with small case series and anecdotal reports from units who use this therapy. Recent literature is reviewed on efficacy, application, composition and potential mechanisms of action of this therapy. Results: Although the evidence base remains quite limited, further data are available that suggest a clear benefit of exclusive enteral nutrition as an efficacious alternative to steroid therapy at inducing a clinical remission in Crohn’s disease. Certain sub-groups are likely to benefit more, with potential benefits on growth making it particularly useful in adolescents and growing young adults. Given the lack of side effects compared to the alternative of steroid therapy, along with the clear nutritional benefits of this therapy, it remains an obvious choice for patients presenting with Crohn’s disease and a degree of malnutrition. Conclusions: This therapy should remain a first-line therapy for children and adults presenting with mild to moderate Crohn’s disease.
Top-Down Therapy: Is the Evidence Strong Enough?
Authors: Domènech Eugeni , Mañosa Míriam , Cabré Eduard
Published: September 2009

Crohn’s disease (CD) has usually been managed in an escalation manner, introducing more powerful (and toxic) drugs only once those with a better safety profile had failed. However, the natural history of CD under conventional therapeutic strategies results in high intestinal resection requirements and high rates of clinical relapse and steroid dependence. Indirect data seem to point at an improved efficacy of drugs when they are introduced early after disease diagnosis. The spreading use of immunomodulators and the appearance of biological agents prompted the idea of their early introduction in order to change the natural history of the disease. By now, only thiopurines have been shown to reduce steroid requirements, relapse rates, and even surgical requirements, at least in pediatric CD. However, many other ‘top-down’ treatment strategies have not yet been evaluated. In addition, there is a risk of overtreating those 10–30% of patients that will have a benign course of the disease; that’s the reason why the implementation of top-down strategies remains as a matter of debate.
Immunomodulation with Methotrexate: Underused and Undervalued?
Authors: Ruemmele Frank M.
Published: September 2009

Therapeutic options for the treatment of inflammatory bowel disease (IBD) are multiple. There are excellent clinical trials showing in patients with IBD that immunomodulatory therapy is highly efficacious in the disease control in moderate active to severe forms. Most clinical experience was gained over the last years with the purine analogues azathioprine (AZA)/6-mercaptopurine (6-MP). These drugs are now considered as gold standard in the treatment of severe Crohn’s disease (CD). However, for patients who fail to respond or who do not tolerate AZA/6-MP therapy, methotrexate is an interesting alternative drug. Two initial clinical trials validated the use of MTX in adult CD cohorts. There are now two retrospective analyses in pediatric cohorts available which nicely demonstrate the efficacy of MTX to maintain long-term remission in CD patients with active and severe disease progression. The remission rates are close to 50% in long-term follow-up, an efficacy comparable to purine analogues. Overall tolerance of MTX was good, with about 10% of adverse events in either study. Taken together, there are first data indicating that MTX might play a role comparable to AZA in the treatment of CD; however, to date it seems to be underused in the routine care of IBD patients.
Treatment of Ulcerative Colitis in the Elderly
Authors: Ananthakrishnan Ashwin N. , Binion David G.
Published: September 2009

Ulcerative colitis (UC) has a bimodal age distribution, with the majority of patients being diagnosed between the second and fourth decades of life. However, a second peak in diagnosis occurs in older patients and an estimated 15% of patients present after age 65. Caring for older UC patients who have either presented later in life or who have carried an inflammatory bowel disease (IBD) diagnosis for multiple decades may pose additional challenges in management. Recent studies using nationwide administrative databases from the USA have demonstrated that older IBD patients are challenged by worse hospital outcomes. This pattern, seen for both UC and Crohn’s disease, demonstrated increased rates of vascular complications (i.e. venous thrombosis), worse post-operative outcomes and increased rates of complicated and prolonged clinical courses compared to younger IBD patients. This article provides an overview of caring for elderly patients with UC, including diagnostic and therapeutic considerations.
Surgery in Ulcerative Colitis: Indication and Timing
Authors: Andersson Peter , Söderholm Johan D.
Published: September 2009

Surgery continues to play an important role in the therapeutic arsenal in ulcerative colitis. In acute colitis, close collaboration between the gastroenterologist and the surgeon is pertinent. Absolute indications for surgery include toxic megacolon, perforation, and severe colorectal bleeding. In addition, surgery should always be considered upon deterioration during medical therapy. The recommended operation in acute colitis is colectomy and ileostomy, with the rectum left in situ; reconstruction is not an option in the acute setting. In chronic continuous colitis, often with long-term steroid therapy, healing conditions are poor. A staged procedure is preferred also in these cases. In cases with dysplasia, surgery should be done after verifying the dysplasia since these patients often have little symptoms from their colitis. The proctocolectomy should in these cases include total mesorectal excision. Ileal pouch-anal anastomosis is the standard bowel reconstruction in ulcerative colitis. The various options should, however, always be thoroughly discussed, considering the pros and cons in each individual patient, before a choice is made. Ileorectal anastomosis is a temporary alternative in select cases (e.g. young women not having had children). Reconstructive surgery is best done approximately 6 months after primary surgery. Surgery for ulcerative colitis should be seen as complementary to medical treatment and may prevent complications, improve the patients’ quality of life and occasionally be life-saving. Correct assessment and optimised medical treatment are prerequisites for surgery on accurate indications and good surgical results. Therefore, close interactions between gastroenterologists and colorectal surgeons are mandatory for optimal patient outcome.
Mild to Moderate Crohn’s Disease: Still Room for Step-Up Therapies?
Authors: Bar-Meir Simon
Published: September 2009

Step-up therapy in Crohn’s disease refers to the classic therapeutic approach resulting in progressive increase of therapies with the increasing severity of the disease. This approach has been recently challenged by the top-down strategy, where biologicals together with thiopurines were used as first-line therapy. Several arguments exist against the top-down therapy. The current ECCO recommendation is in favor of the step-up therapy. ECCO recommended budesonide 9 mg daily as the preferred treatment in mild to moderate Crohn’s disease patients. The benefit of mesalazine in small bowel disease is limited and should be considered clinically no more effective than placebo. Antibiotics cannot be recommended unless septic complications are suspected. No treatment is an option for some patients with mild symptoms. Budesonide is preferred to prednisone for mild active Crohn’s disease because it is associated with fewer side effects. Active mild colonic disease may be treated with sulfasalazine and when needed with systemic corticosteroids as well. Topical treatment should be considered for distal disease. The national cooperative Crohn’s disease study and the European co-operative Crohn’s disease study established corticosteroids as an effective therapy for inducing remission in Crohn’s disease. Remission is achieved in 60–83% of the patients. A Cochrane review of the efficacy of azathioprine and 6-mercaptopurine for inducing remission in active Crohn’s disease showed a benefit for thiopurine therapy compared with placebo. Methotrexate is another effective medication that has been confirmed in a systematic review. Once remission has been achieved with systemic corticosteroids, maintenance with azathioprine should be considered. For patients with extensive colitis, long-term treatment with mesalazine is an option as this may reduce the risk of colon cancer, although this is still unproved in Crohn’s disease. In conclusion, the natural course of most patients with Crohn’s disease is relatively mild and there is a room for step-up therapy. The efficacy of most medications is similar to the efficacy of infliximab but with less adverse effects. Infliximab should be reserved only for patients where other therapies failed.