bluuebunny/crossref_metadata_2025_split huggingface dataset:
3-Mercaptopropionic Acid modified Porous Silicon Substrate used in Hyperammonemia
Authors: Yun Dong-hwa , Chang Jun-Hyoung , Lee Woo-Jin , Hong Suk-In 
Published: April 2011

ABSTRACTAmperometric urea sensor is more suitable than optical and potentiometric urea sensor to diagnose hyperammonemia. However, because sensitivity in low concentration decreases remarkably, despite amperometric urea sensor has been studied for a long time it has not been applied for clinical diagnosis. In this paper, a new structure for an amperometric urea sensor was fabricated by MEMS, electrochemical etching, and electrostatic covalent binding techniques. Until now most amperometric urea sensors have had a membrane fixed on top of the transducer. That method often leads to malfunction of the sensor, arising from problems such as inadequate membrane adhesion, insufficient mechanical stability, and low sensitivity. To solve these kinds of problems, urease (Urs) was immobilized by electrostatic covalent binding method on the porous silicon (PSi) substrate coated self-assembled monolayer (SAM). Electrostatic covalent binding method was used to keep anisotropic orientation of urease on SAM.
Characterization of Gap Defect States in Hydrogenated Amorphous Silicon Materials
Authors: Jiao Lihong , Wronski C. R. 
Published: April 2011

ABSTRACTAn enhanced simulation model based on the carrier recombination through these states was developed to characterize the gap defect states in hydrogenated amorphous silicon materials (a-Si:H). The energy dependent density of electron occupied gap states, kN(E), was derived directly from Dual Beam Photoconductivity (DBP) measurements at different bias currents. Through Gaussian de-convolution of kN(E), the energy peaks of the multiple defect states, including both neutral and charged states, were obtained. These energy levels, together with the information on the capture cross sections, were used as known input parameters to self-consistently fit the subgap absorption spectra, the electron mobility-lifetime products over a wide range of generation rates, as well as the energy dependent density of electron occupied gap state spectra. Accurate gap state information was obtained and the nature of the defect states was studied. Simulation results on light degraded hydrogen diluted, protocrystalline a-Si:H show that the density of charged states is 2.3 times that of neutral states. The two states close to the midgap act as effective recombination centers at low generation rates and play key roles in photoconductivity studies.
Nanocrystalline Silicon Diodes for Rectifiers on Flexible RFID Tags
Authors: Kwong Ian Chi Yan , Lee Hyun Jung , Sazonov Andrei 
Published: April 2011

ABSTRACTThere has been an on-going effort to produce low cost radio frequency identification (RFID) tags as a replacement for traditional barcodes. One method to achieve low cost production is to integrate the manufacturing of the substrate, antenna and active devices into one single continuous process. Hydrogenated nanocrystalline silicon (nc-Si:H) is a suitable material for manufacturing the active devices in such a process.We present a nc-Si:H diode suitable for use in rectifiers on RFID tags. It consists of a Cr bottom contact, an undoped layer of nc-Si:H, an n-doped nc-Si:H and an Al top contact. We demonstrate the current-voltage characteristics of the nc-Si:H diode are much improved over a-Si:H diodes. Current density of 10 A/cm2 and ON/OFF ratio greater than 106 was measured at 2 V forward bias. Output DC voltage of 2.6 V was achieved using four nc-Si:H diodes in a full-wave bridge rectifier. The input AC signal was a sine wave at 14 MHz and 2 VRMS amplitude.
Microstructure Effects in Hot-wire Deposited Undoped Microcrystalline Silicon Films
Authors: Beyer Wolfhard , Carius Reinhard , Lennartz Dorothea , Niessen Lars , Pennartz Frank 
Published: April 2011

ABSTRACTThe microstructure of hot-wire microcrystalline silicon films prepared at a wide range of deposition conditions was characterized by both the microstructure parameter from infrared absorption data (analyzing the Si-H stretching modes) and the effusion spectra of (low dose) implanted He and Ne. Parameter ranges leading to the growth of a dense material are identified. A (relatively) high silane flow at rather high filament temperature is found to result in a dense material at high deposition rate. The microstructure data obtained by the two microstructure characterization methods are found to be largely correlated.
Structural and Opto-Electronic Properties of a-Si:H/a-SiNx:H Superlattices
Authors: Luxembourg Stefan L. , Tichelaar Frans D. , Kúš Peter , Zeman Miro 
Published: April 2011

ABSTRACTA series of multilayer structures consisting of alternating layers of hydrogenated amorphous silicon (a-Si:H) and amorphous silicon nitride (a-SiNx:H) was fabricated using plasma enhanced chemical vapor deposition. The overall thickness and a-Si:H-to-a-SiNx:H ratio was kept constant for the different multilayer samples fabricated. A blue shift of the optical bandgap was observed with decreasing a-Si:H well layer thickness. High-Resolution Transmission Electron Microscopy was used to estimate the abruptness of the layer-to-layer transitions. The thickness of the interface mixing layer for transitions from a-Si:H to a-SiNx:H was estimated to be 0.5 − 1 nm, while for the reverse transition a thickness of 2-2.5 nm was found. Results from Fourier Transform Infrared Spectroscopy support the found thickness range.
Characterization and light emission properties of osmium silicides synthesized by low energy ion implantation
Authors: Poudel Prakash R. , Hossain K. , Li J. , Gorman B. , Neogi A. , Rout B. , Duggan J. L. , McDaniel F. D. 
Published: April 2011

ABSTRACTLow energy (55 KeV) Osmium ( Os− ) negative ion beam was used to implant (5×1016 atoms/cm2 ) into p-type-Si (100). The implantation was performed with the ion source of a National Electrostatic Corp. 3 MV Tandem accelerator. The implanted sample was subsequently annealed at 650 °C in a gas mixture that was 4% H2 + 96% Ar. Rutherford Backscattering spectrometry (RBS) analysis with 1.5 MeV Alpha particles was used to monitor the precipitate formation. Photoluminescence (PL) measurements were also performed to study possible applications of silicides in light emission. Cross-sectional Scanning Electron Microscopy (X-SEM) was performed for topographic image of the implanted region. RBS along with PL measurements indicate that the presence of osmium silicide (Os2Si3) phase for light emission in the implanted region of the sample.
High Performance Bottom Gate μc-Si TFT Fabricated by Microwave Plasma CVD
Authors: Hiroe Akihiko , Teramoto Akinobu , Ohmi Tadahiro 
Published: April 2011

ABSTRACTDeposition trend of μc-Si was investigated using microwave (2.45GHz) plasma enhanced CVD. μc-Si films with the preferential orientation of (111) and (220) were deposited and compared. Raman scattering results show that the (111) preferentially oriented film has higher crystallinity while ESR measurements result in the fact that the (220) preferentially oriented film has smaller dangling bond density. Bottom gate thin film transistors (TFT's) were fabricated using these μc-Si films as channel layer and evaluated. H2 plasma post-treatment has been found to be effective to improve the TFT characteristics. Mobility of about 1.4cm2/Vsec and on/off ratio of more than 105 have been achieved.
Hydrogenated Nanocrystalline Silicon Thin Film Transistor Array for X-ray Detector Application
Authors: Shin Kyung-Wook , Esmaeili-Rad Mohammad R. , Sazonov Andrei , Nathan Arokia 
Published: April 2011

ABSTRACTHydrogenated nanocrystalline silicon (nc-Si:H) has strong potential to replace the hydrogenated amorphous silicon (a-Si:H) in thin film transistors (TFTs) due to its compatibility with the current industrial a-Si:H processes, and its better threshold voltage stability [1]. In this paper, we present an experimental TFT array backplane for direct conversion X-ray detector, using inverted staggered bottom gate nc-Si:H TFT as switching element. The TFTs employed a nc-Si:H/a-Si:H bilayer as the channel layer and hydrogenated amorphous silicon nitride (a-SiNx) as the gate dielectric; both layers deposited by plasma enhanced chemical vapor deposition (PECVD) at 280°C. Each pixel consists of a switching TFT, a charge storage capacitor (Cpx), and a mushroom electrode which serves as the bottom contact for X-ray detector such as amorphous selenium photoconductor. The chemical composition of the a-SiNx was studied by Fourier transform infrared spectroscopy. Current-voltage measurements of the a-SiNx film demonstrate that a breakdown field of 4.3 MV/cm.. TFTs in the array exhibits a field effect mobility (μEF) of 0.15 cm2/V·s, a threshold voltage (VTh) of 5.71 V, and a subthreshold leakage current (Isub) of 10−10 A. The fabrication sequence and TFT characteristics will be discussed in details.
Laser Fabrication of Sharp Conical Microstructures on Si Thin Films by Nd:YAG Laser Single Pulse Irradiation
Authors: Georgiev Daniel , Georgiev Daniel 
Published: April 2011

ABSTRACTConical microstructures with nanoscale sharpness form on silicon films as a result of single-pulse, localized UV irradiation using a solid-state, Q-switched Nd:YAG laser. Projection imaging of pinhole apertures was employed to obtain micron-sized irradiation spots on the surface of silicon-on-insulator samples. The formation of these structures requires melting of the silicon film and was followed at different laser fluence levels and irradiation spot sizes. Atomic force microscopy (AFM) was used to characterize the structures. After fabricating small arrays of such micro-cones, the silicon top layer was selectively etched away in order to understand the role of the underlying silicon oxide. AFM images of such etched samples revealed that the topography of the oxide material below the cones had been significantly modified: bumps with heights that represent a significant fraction of the original Si cone height have formed. This suggests that substrate melting plays an important role in the mechanism of formation of the silicon cones.
Optimization of Flash Annealing Parameters to Achieve Ultra-Shallow Junctions for sub-45nm CMOS
Authors: Kalra Pankaj , Majhi Prashant , Tseng Hsing-Huang , Jammy Raj , King Liu Tsu-Jae 
Published: April 2011

ABSTRACTThe use of millisecond annealing to meet ultra-shallow junction requirements for sub-45nm CMOS technologies is imperative. In this study, the effect of flash anneal parameters is presented. Reduced dopant diffusion and lower sheet resistance Rs is achieved for intermediate temperature Tint = 700°C (vs. 800°C). Significantly lower Rs is achieved with peak temperature Tpeak = 1300°C (vs. 1250°C). Multiple shots provide for lower Rs, albeit at the expense of increased dopant diffusion. Based on a simple quantitative model, an optimal flash anneal can achieve 82% dopant activation efficiency.
Dopant Condensation beyond Solubility Limit in the Vicinity of Silicon/Silicide Interface Based on First-Principles Calculations
Authors: Yamauchi Takashi , Nishi Yoshifumi , Kinoshita Atsuhiro , Tsuchiya Yoshinori , Koga Junji , Kato Koichi 
Published: April 2011

ABSTRACTIn the trend of scaling down metal-oxide-semiconductor field effect transistors (MOSFETs), reduction of contact resistance at the silicide/silicon (Si) interface will be essential for higher performance. Nickel silicide (NiSi) is considered as a substi-tute for a present electrode material in MOSFETs, cobalt silicide (CoSi2), because silicidation temperature can be reduced as compared with the case of the conventional CoSi2. Hence, we have focused on the NiSi/Si Schottky interface. An ordinary method to increase the dopant concentration at the interface is ion implantation before silicidation process. The dopant atoms are consequently condensed around the interface by snowplow effect, leading to the effective lowering of the Schottky bar-rier height (SBH) because of the band bending enhancement of the Si layer. However, this band bending technique does not reduce the SBH in further scaled MOSFETs. In this context, we studied another possibility of SBH modulation technique, based on the first-principles calculations. Throughout our calculations, we found that a large atomic-scale dipole between impurity and silicide atoms is generated across the interface. Impurity atoms are expected to be condensed because of a large energy gain at the interfaces, leading to the dramatic reduction of the SBH. Based on these results, we proposed a novel di-pole comforting Schottky (DCS) junction. We have also found that the thickness of the Si layer interfacing with the NiSi layer can be 1nm or less. In the present work, we applied this idea to the actual process through experimental techniques. The calculated results suggest that B implantation after silicidation leads to larger B concentration at the interface than that before silicidation, and thereby larger SBH modulation due to interface dipoles can be produced. Then, the NiSi/Si Schottky diodes were formed by ion implantation after silicidation process for dopants (As, B). We evaluated the interface dipoles contribution to the measured SBH reduction. As a result, the dopant atoms were found to be condensed beyond solubility limits on the interface Si side and we confirmed the generated interface dipoles actually reduces the SBT. Furthermore, we explored the other possibility of another type of impurity atoms applicable to the DCS junction. Among some other impurity atoms (Al, In, Mg), the calculated SBH modulation due to dipoles generated around these impurity atoms were found to be further enhanced in some cases. Based on these understandings, we propose a principle for choosing dopants towards ulti-mate lowering of the contact resistance in ultimately scaled MOSFETs.
Strategies for CMOS Low Equivalent Oxide Thickness Achievement with High-κ Oxides Grown on Si(001) by MBE
Authors: Becerra Loic , Merckling Clément , Baboux Nicolas , El-Kazzi Mario , Saint-Girons Guillaume , Vilquin Bertrand , Plossu Carole , Hollinger Guy 
Published: April 2011

ABSTRACTAmorphous LaAlO3 high-k oxide was grown in a molecular beam epitaxy reactor on p-Si(001) using a thin γ-Al2O3 epitaxied buffer layer. Interfaces were free of SiO2 or silicates and remained abrupt despite the high temperature used for annealing, as X-ray photoelectron spectroscopy showed. Electrical measurements performed on as-deposited samples revealed a dielectric constant value close to that of the bulk, small equivalent oxide thickness and low density of interface states. But some negative charges were present, leading to a flat band voltage shift. Post deposition annealing with forming gas can correct this effect.
Real-Time Spectroscopic Ellipsometry Studies of Zinc Oxide Deposition
Authors: Fesenmaier Christian Carl , Li Xiaonan S. , To Bobby , Levi Dean H. 
Published: April 2011

ABSTRACTZinc oxide is increasingly being studied as an eventual replacement for indium tin oxide as a transparent conducting oxide (TCO) for thin film solar cells. In order to better understand the growth process of ZnO, as well as provide for accurate control on the National Renewable Energy Laboratory's TCO deposition system, undoped RF-magnetron sputtered ZnO films on silicon were analyzed in situ using real-time spectroscopic ellipsometry (RTSE). A large wavelength range (245-994 nm) was measured in order to derive information about optical properties both below and above the bandgap. Atomic force microscopy (AFM) measurements were also taken to confirm ellipsometry surface roughness results and provide additional insight into the surface morphology.In light of observed poor fit of typical two-layer optical models to in situ ellipsometry data, we propose a model film structure consisting of two layers: a bulk ZnO layer of graded density that increases in thickness as the growth proceeds and a growth zone at the top of the film of approximately constant thickness with a slightly larger bandgap, lower density, and decreased excitonic absorption. Unfortunately, this model is insufficient to explain the evolution of the film during the early growth period, corresponding to film thicknesses less than 100 nm. Nevertheless, the presence of a growth zone for films above a certain thickness should provide some insight into the growth process of RF-magnetron sputtered ZnO.
Preparation and Properties of Silica-Coated AgI Nanoparticles with a Modified Stober Method
Authors: Kobayashi Yoshio , Misawa Kiyoto , Takeda Motohiro , Ohuchi Noriaki , Kasuya Atsuo , Konno Mikio 
Published: April 2011

ABSTRACTIodine compounds have been used as X-ray contrast agents in the field of medicine, because of their low transmittance property for X-ray. The iodine compounds may provoke adverse events as allergic reactions in patients, so that they can not be administered to such people. Core-shell nanoparticles are good candidates for prevention of allergic reactions, because the shell materials can keep the contrast agents from living systems. We have proposed a method for silica-coating of iodine compounds as AgI nanoparticles. In the present work, properties of the silica-coated AgI nanoparticles such as colloidal stability, X-ray absorption and X-ray CT imaging were examined.Silica-coated AgI nanoparticles were prepared with Stöber method, which was performed with 2.3×10-5 M MPS, 11 M water, 0.01 M DMA and 0.01 M tetraethyl orthosilicate in the presence of 5×10-4 M AgI nanoparticles that were prepared from AgClO4 and KI. The particles had an AgI core size of ca. 15 nm and a silica shell thickness of ca. 20 nm.Since high iodine concentration in sample solution is desired for practical use as X-ray contrast agents, the colloid of as-prepared coated particles was concentrated with centrifugation. The particle colloid that was concentrated up to an AgI concentration as high as 0.4 M was colloidally stable in saline, and exhibited properties of X-ray absorption and X-ray contrasting comparable to a commercial X-ray contrast agent. Accordingly, the silica-coated AgI nanoparticles prepared in the present work are expected to be applied to a novel X-ray contrast agent.
Electrochemical Fabrication of InSb Nanowires using Porous Alumina Membrane and their Characterization
Authors: Khan Muhammad Ibrahim , Wang Xu , Bozhilov Krassimir N. , Ozkan Cengiz S. 
Published: April 2011

ABSTRACTAmong various ways to produce nanowires; anodic alumina membrane (AAM) based synthesis has constantly received much attention because AAM possess a uniform and parallel porous structure which makes them an ideal template material for creating highly ordered nanostructures. In this paper we report fabrication of InSb nanowire arrays with diameter of 200 nm and 30 nm by direct current electrodeposition inside the nanochannels of anodic alumina membranes without subsequent annealing. The nanowires have four major growth direction, [220] being the most dominant with structure defects such as twins. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results demonstrate that these InSb nanowires are uniform with diameters about 200 nm and 30 nm, corresponding to the pore diameter of the AAMs. The nanowires also conduct almost no current in the dark, but when hit with light, they conduct 10,000 times more current. This photoconduction property could lead to a variety of tiny optoelectronic devices potentially useful in future generations of nanoelectronics and chemical sensors. The light-induced conductivity increase and the temperature dependent behavior of the nanowires are also reported.
C60 Fulleride Molecular Nanowire Crystals
Authors: Moriyama Hiroshi , Sugiura Takahito , Mori Hatsumi 
Published: April 2011

ABSTRACTThe novel low-dimensional nanostructural self-alignment of molecular nanowire composed of a C60 anion radical moiety (fulleride) formed by electrocrystallization was revealed by single crystal structure analysis of C60 fulleride salts stabilized by triphenylmethane dye cations. The structure should be noted as molecular nanowire and anticipated to be an organic novel semiconductor from the preliminary four-probe conductance measurement. C60 fulleride has drawn much attention because of its interesting physical properties, such as superconducting of alkali-metal doped C60(A3C60) and unique ferromagnetic behavior of tetrakis(dimethylamino)ethane salts of C60 fulleride, (TDAE)C60.[20]. These intriguing solid-state properties of C60 fulleride should arise from electronic cooperative interactions, mainly due to electron-accepting ability of C60 and the ball-to-ball van der Waals interaction. However, there have been rather a limited number of well-characterized C60 anion radical salts, in particular, molecular discrete fulleride, predominantly because of their sensitivity to air.We have succeeded in obtaining highly ordered single crystals of C60 anion radical salts stabilized by cationic triphenylmethane dyes, some of which were found to give rise to an intriguing nanostructural columnar alignment like molecular nanowire of C60 fullerides. The single-crystal structure of [Crystal Violet]+C60−. C6H5Cl, reveals that the C60 fulleride aligns like molecular nanowire with the columnar structure along the a axis (crystal growth direction), as well as a zigzag structure along the b axis, with contacts of almost van der Waals magnitude (ca. 10 Å, distance of the C60–C60 center of mass), stabilized by mutual interactions of C60−. and dye, due to such as CH-π, π-π, and face-to-face mutual interactions.Magnetic susceptibility measurements for crystal violet salts demonstrate antiferromagnetic behavior, which can be fitted fairly by one-dimensional Heisenberg model (uniform chain), associated with the one-dimensional columnar crystal structure of the C60 fulleride molecular nanowire. These results also account for the semiconducting properties of the corresponding salts.
CO Coverage Effects on Pt(111) from First-Principles Calculations
Authors: Shan Bin , Wang Ligen , Hyun Jangsuk , Sang Yang , Zhao Yujun , Nicholas John B 
Published: April 2011

ABSTRACTCO saturation coverage on Pt(111) is crucially important in diesel oxidation catalysis. We systematically studied high coverage CO adsorption on the Pt(111) surface using density functional theory (DFT) calculations and classical Monte Carlo (MC) simulations. The zero-coverage limit CO adsorption energy at different binding sites is almost degenerate at the revised Perdew–Burke–Erzernhof functional (RPBE) level. As CO populates the surface, strong through-space repulsion and substrate-mediated metal sharing tends to dominate the stability of adsorbates and alter their binding preferences. The calculated differential binding energy curve and adsorption patterns compare well with experiments.