bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biocompatible Ceramics for Implants Based on Calcium Phosphates
Authors: Safronova Tatiana , Putlayev Valery I. , Veresov Alexander G. , Kuznetsov Anton V. , Shekhirev Mikhail A. , Agahi Kamila A. 
Published: April 2011

ABSTRACTHydroxyapatite (HAp), tricalcium phosphate (TCP) and calcium pyrophosphate (CPP) are known to be among calcium phosphates used in clinical medicine due to their biocompatibility. HAp and other complex calcium phosphate salts are the end-products of the biological mineralization process. Calcium pyrophosphate Ca2P2O7 (β-CPP) is one of the intermediate products involved in this process. The biological response with respect to new bone formation is quite similar for CPP and HAp. Sintered CPP has better biological responses, and, thus, a great potential as a biodegradable bone substitute. The rate of biodegradation depends on: (i) material texture (porosity type and level), (ii) quality of biodegradation phase (phase composition, grain size, properties of grain boundaries). Several sources for CPP phase in ceramics can be assumed. CPP phase may come from frit (CaO-P2O5, Ca/P=0.2-0.75) used as a sintering additive. Ceramics can be fabricated from powder of CPP with Na4P2O7 as sintering additive, via interaction between H3PO4 or (NH4)2HPO4 and porous HAp at high temperature after soaking it in the former solutions. The aim of the present work was focused on fabrication of multiphase ceramics with enhanced resorptivity due to presence of CPP phase and investigation of processes leading to formation of the multiphase ceramics based on HAp and CPP originated from CaHPO4. Ceramic materials have been made from mixtures of powders of stoihiometric HAp (Ca/P=1.67) and monetite (CaHPO4, Ca/P=1). Powders of HAp and monetite were synthesized by means of wet chemical precipitation from aqueous solutions of Ca(NO3)2*4H2O and (NH4)2HPO4 at 60 °C and pH=9 for HAp and pH=4-5 for monetite. Component ratio HAp:monetite was varied from 0:100 to 100:0 % with a step of 20%. Powders of raw materials and the mixtures were tested by means of XRD, TG, DTG, SEM, dilatometry. Linear shrinkage, density and microstructure of samples of ceramic materials sintered at 900, 1000, 1100°C with isothermal holding during 6 hours were tested. Complicated consequence of phase transformations took place during heating the the mixtures from 20 to 1200 C. The CPP (Ca/P=1, converted from CaHPO4 at 400-500°C ) reacts with HAp (Ca/P=1.67) causing additional weight loss in the region of 600-1050°C due to solid state reaction leading to TCP (Ca/P=1.55) formation. Linear shrinkage of HAp at 1100°C after 6 hours was found to be about 21%; for Ca2P2O7 formed from monetite, and for the mixtures - less than 11%. Resulted ceramics with the phase composition of HAp, CPP and TCP, i.e. with a different content of degradable phase and different ratio of CPP/TCP, can be treated as a biocompatible bioactive material with a tunable rate and limit of biodegradation.
Rapid Detection of Bacillus anthracis in a Microchip-based Real-time PCR Biosensor
Authors: Cady Nathaniel Charles , Stelick Scott J. , Batt Carl 
Published: April 2011

ABSTRACTA miniaturized, fully-automated, PCR-based detection system has been developed for the rapid detection of the pathogenic bacteriumBacillus anthracis. Monolithic silicon DNA purification / real-time PCR chips were fabricated and tested for their ability to purify and detect DNA from bacterial cells. Using silica-coated microstructures and chemical-based lysis, nucleic acids could be isolated, washed and eluted for subsequent real-time PCR. These microstructures were integrated into a detection microchip containing two distinct regions, one for DNA purification and one for real-time PCR. Using an automated detection platform with integrated microprocessor, pumps, valves, thermocycler and fluorescence detector, target bacterial DNA was detected by real-time PCR amplification using SYBR Green fluorescent dye. As few as 40B. anthraciscells could be detected using this system with an average time for detection of 60 min. Detection was augmented by on-chip melting curve analysis capable of differentiating between positive and false-positive results.
High Temperature MOVPE Growth of AlxGa1−xN (0.2-1) Layers on Sapphire and SiC Substrates for the Fabrication Deep UV Optical Devices
Authors: Krishnan Balakrishnan , Imura Masataka , Iida Kazuyoshi , Nagamatsu Kentaro , Sugimura Hiroki , Nagai Tetsuya , Sumii Takafumi , Mori Fumiaki , Bandoh Akira , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu 
Published: April 2011

ABSTRACTSingle crystalline AlN epitaxial layers have been grown on and (0001) sapphire and 6H-SiC substrates by MOVPE technique at high temperatures in the range of 1340-1500°C. The structural qualities of the high temperature grown AlN layers were found to be good as evidenced by X-ray diffraction analyses results. By transmission electron microscopic analysis, dislocation densities of the layers were found to be 6.2 × 107 cm−2 or lower and the formation of dislocation loops was confirmed. High temperature bridge layers of AlN and AlxGa1−xN layers were grown on linear-groove patterned sapphire based AlN templates and 6H-SiC substrates. AlxGa1−xN bridge layers exhibited different growth behaviours depending on the direction of groove patterns on the sub-strates.
Blue-green-red LEDs based on InGaN Quantum Dots by Plasma-assisted MBE using GaN QDs for Dislocation Filtering
Authors: Xu Tao , Nikiforov Alexey Yu , France Ryan , Thomidis Christos , Williams Adrian , Moustakas Theodore D. , Zhou Lin , Smith David J 
Published: April 2011

ABSTRACTIn this paper, we report the development of blue-green-red LEDs based on InGaN quantum dots (QDs) and quantum wells in the active region, and GaN QDs in the nucleation layer for dislocation filtering, by plasma assisted molecular beam epitaxy. Self-assembled InGaN QDs and GaN QDs were grown in the Stranski-Krastanov mode. For the GaN QDs grown at 770 °C, the height distribution of the dots shows a bimodal distribution, which can be attributed to the interaction of the GaN QDs with the threading dislocations. TEM and XRD studies indicate that GaN QDs in the nucleation region help threading dislocations to deviate and annihilate. The average dot height, diameter and density of the InGaN QDs were estimated to be 3 nm, 30 nm and 7×1010 cm−2, respectively. The cathodoluminescence emission peak of the InGaN/GaN multiple layer quantum dots (MQDs) was found to red shift 330 meV with respect to the emission peak of the uncapped single layer of InGaN QDs due to Quantum Confined Stark effect. Blue LEDs based on InGaN/GaN multiple quantum wells (MQWs) as well as green and red LEDs based on InGaN MQDs emitting at 440 nm, 560 nm and 640 nm with FWHM of 30 nm, 87 nm and 97 nm, respectively, were grown and fabricated. The electroluminescence peak positions of both the green and red InGaN MQD LEDs are shown to be more blue-shifted with increasing injection current than that of the blue InGaN/GaN MQW LEDs.
Recombination dynamics in ultraviolet light-emitting diodes with Si-doped AlxGa1−xN/AlyGa1−yN multiple quantum well active regions
Authors: Chen Kaixuan , Xi Y. A. , Mont F. W. , Kim J. K. , Schubert E. F. , Li X. , Liu W. , Smart J. A. 
Published: April 2011

ABSTRACTUltraviolet light-emitting diodes (UV LEDs) with AlxGa1−xN/AlyGa1−yN multiple quantum well (MQW) active regions, doped in the barriers with different Si doping level, show a sharp near band-edge emission (UV luminescence). Besides the near band-edge emission, some samples also show parasitic emissions with a broad peak centered at about 520 nm (green luminescence). The EL intensities of the UV emission line and the green emission line are studied. The UV luminescence peak intensity increases superlinearly with the injection current, following a power law with an exponent of about 2.0. In contrast, the green luminescence peak intensity increases linearly with the injection current, with an exponent of about 1.0. A theoretical model is proposed to explain the relationship between the peak intensities and the injection current. The results obtained from the model are in excellent agreement with the experimental results. The model provides a method to evaluate the dominant recombination process by measuring the exponent of the power-law dependence.
Investigation of the Optical Properties of epitaxial-lateral-overgrown GaN on R- and M- plane Sapphire
Authors: Guhne Tobias , Bougrioua Zahia , Albrecht Martin , Vennéguès Phillippe , Leroux Mathieu , Laügt Marguerite , Ndiaye Sosse , Teisseire Monique , Nguyen Luan , Gibart Pierre 
Published: April 2011

ABSTRACTOptical properties of GaN templates grown by the Epitaxial Lateral Overgrowth (ELO) technique along the nonpolar (1120) and the semipolar (1122) directions on R- and M-sapphire were investigated. Spatially resolved Cathodoluminescence (CL) was carried out in order to identify defect related transitions, to resolve their localization and to study the efficiency of ELO concerning defect filtration. The wing region of semipolar GaN is shown to be almost defect free with a luminescence spectrum dominated by the GaN emission at 3,472 eV. It is shown that the defect related emissions are localized in the seed, but different defects occur as well in the wing, especially in A-plane (nonpolar) GaN.
n-Type Doping of Diamond
Authors: Koizumi Satoshi 
Published: April 2011

ABSTRACTn-Type doping of diamond is one of the most important issues for electronic application of diamond. Phosphorus is the best candidate as an n-type dopant at this moment. We have succeeded to grow high quality phosphorus doped diamond thin films on {111} diamond substrates. Although the ionization energy of phosphorus donor is large (0.57 eV), the n-type conductivity is clearly observed by Hall measurements. The Hall mobility is as high as 660 cm2/V-sec at room temperature. In this paper, current status of n-type diamond research are mentioned mainly focused on the growth of high mobility n-type diamond and its electrical properties. The Hall measurements performed in a wide temperature range gives detailed information about the n-type conductivity nature of phosphorus doped diamond.
Single Crystal CVD Diamond growth and characterizations
Authors: Tranchant Nicolas Olivier , Tromson Dominique , Remes Zdenek , Rocha Licinio , Nesladek Milos , Bergonzo Philippe 
Published: April 2011

ABSTRACTDue to its radiation harness, single crystal CVD diamond is a remarkable material for the construction of detectors used in hadron physics and for medical therapy. In this work, single crystal CVD diamond plates were grown in a microwave plasma reactor, using home design substrate holder and a relatively high pressure. Optical Emission Spectroscopy was employed during the MW-PECVD growth to characterize excited species present in the plasma and to detect the presence of residual gases such as nitrogen which is unsuitable for detector's applications.The samples were characterized using various methods such as Raman spectroscopy, photoluminescence (PL), photocurrent spectroscopy, Raman mapping, birefringence microscopy, optical microscopy and also AFM. The best sample, exhibits a FWHM for the 1332 cm−1 Raman peak about 1.6 cm−1. Room temperature PL spectra showed no N–related luminescence, confirming the high quality of the grown single crystal diamond.
Electrical Characterization of Proton Irradiated n-Type ZnO
Authors: Auret F Danie , Hayes Michael , Nel Jackie , Meyer Walter , Janse van Rensburg Pieter Johan , Wesch Werner , Wendler E 
Published: April 2011

ABSTRACTRu Schottky barrier diodes (SBD's) were fabricated on the Zn face of n-type ZnO. These diodes were irradiated with 1.8 MeV at fluences ranging from 1 ´ 1013 cm-2 to 2.4 ´ 1014 cm-2. Capacitance and current (I) deep level transient spectroscopy (DLTS) was used to characterise the irradiation induced defects. Capacitance DLTS showed that proton irradiation introduced a level, Ep1, at 0.52 eV below the conduction band at an introduction rate of 13±1 cm-1. A defect with a very similar DLTS signature was also present in low concentrations in unirradiated ZnO. I-DLTS revealed that this proton irradiation introduced a defect with an energy level at (0.036± 0.004) eV below the conduction band. This defect is clearly distinguishable from a defect with a level at (0.033± 0.004) eV below the conduction band that was present in the unirradiated sample. It is speculated that these shallow level defects are related to zinc interstitials or complexes involving them.
Visible-Light Sensitivity in N-Doped ZnO Films Prepared by Reactive Magnetron Sputtering
Authors: Nakano Yoshitaka , Morikawa Takeshi , Ohwaki Takeshi 
Published: April 2011

ABSTRACTWe report on visible-light sensitivity in N-doped ZnO (ZnO:N) films that were deposited on ITO/quartz substrates by reactive magnetron sputtering. Colored ZnO:N samples showed enhanced polycrystallization and a significant decrease in optical band gap from 3.1 to 2.3 eV with increasing N doping concentration, as determined by x-ray diffraction and optical absorption measurements. Deep-level optical spectroscopy measurements revealed three characteristic deep levels located at ∼0.98, ∼1.20, and ∼2.21 eV below the conduction band. In particular, the pronounced 2.21 eV band is newly introduced by the N doping and behaves as part of the valence band, resulting in the band-gap narrowing of ZnO. Therefore, this deep level is probably one origin of visible-light sensitivity in ZnO:N.
Elaboration and Characterization of ZnO Transition Metal (Co, Mn, Ni, Fe) Doped Aerogel Nanoparticles
Authors: El Mir Lassaad , Ben Mahmoud Aroussi , von Bardeleben H.Jurgen , Cantin Jean-Louis 
Published: April 2011

ABSTRACTNanocrystalline transition metal (TM=Co, Mn, Ni, Fe) doped zinc oxide powders have been elaborated by a new protocol based on slow hydrolyse of zinc acetate dissolved in methanol and supercritical drying in ethyl alcohol. The powders have a narrow size distribution with an average value of ∼ 25nm. Electron microscopy characterization showed that the size of the ZnO:TM particles did not change significantly for the different dopants. High doping levels of up to [TM] =0.25 have been investigated. X-ray diffraction studies showed the formation of the ZnO wurtzite phase for all dopants but secondary phases are equally detected. High temperature ferromagnetism was observed for Ni and Co doped powders whereas Mn doped powders showed only antiferromagnetic interactions. EPR spectroscopy indicates that the magnetism is related to the presence of extrinsic phases.
Structural, Optical and Magnetic Properties of Co and Fe Doped ZnO Thin Films Grown by Radio Frequency Magnetron Sputtering
Authors: Angelats Luis Manuel , Tomar Maharaj S , Singhal Rahul , Perez Oscar P , Jimenez Hector J , Martinez Ricardo 
Published: April 2011

ABSTRACTZn0.90Co0.10O and Zn0.85[Co0.50Fe0.50]0.15O targets were used to grow thin films by rf magnetron sputtering. XRD patterns of the films showed a strong preferred orientation along c-axis. Zn0.90Co0.10O film showed a transmittance above 75% in the visible range, while the transmittance of the Zn0.85[Co0.50Fe0.50]0.15O film was about 45%; with three absorption peaks attributed to d-d transitions of tetrahedrally coordinated Co2+. The band gap values for Zn0.90Co0.10O and Zn0.85[Co0.50Fe0.50]0.15O films were 2.95 and 2.70 eV respectively, which are slightly less than ZnO bulk. The Zn0.90Co0.10O film showed a relatively large positive magnetoresistance (MR) at the high magnetic field in the temperature range from 7 to 50 K, which reached 11.9% a 7K for the magnetoresistance. The lowest MR was found at 100 K. From M-H curve measured at room temperature shown a probable antiferromagnetic behavior, although was possible to observe little coercive field of 30 Oe and 40 Oe for Zn0.90Co0.10O and Zn0.85[Co0.50Fe0.50]0.15O films, respectively.
Forces that Drive the Self-assembly of Metallic Dots on Semiconductor Substrates
Authors: Salac David , Lu Wei 
Published: April 2011

ABSTRACTThe scaling and ordering of metallic nanoclusters on semiconductor substrates has been explored computationally. Numerical techniques were implemented to calculate the total electrostatic and van der Waals energies for systems containing multiple disks. Observations show that interactions in charge clouds beneath the metallic disks led to an electrostatic repulsive force. Attraction was observed due to the van der Waals energy. An energy barrier exists for disk coalescence. This work suggests the potential of double layer charges in the development of large-scale nanodot systems that require precise control over both dot location and size.
InAs and InP Quantum Dot Molecules and their Potentials for Photovoltaic Applications
Authors: Jevasuwan Wipakorn , Thainoi Supachok , Kanjanachuchai Songphol , Ratanathammaphan Somchai , Panyakeow Somsak 
Published: April 2011

ABSTRACTSelf-assembled InAs and InP quantum dot molecules (QDMs) are grown on GaAs substrates using different molecular beam epitaxial (MBE) growth techniques. The structural and optical properties of the two types of QDMs are then compared and reported. Multi-stack high-density (1012 cm-2) InAs QDMs are grown and when inserted into GaAlAs/GaAs heterostructure results in high-efficiency solar cells. As an alternative to InAs, InP QDMs are grown by droplet epitaxy of In and annealing under P2 pressure. While the number of quantum dots per QDM in the case of InP is in the range of 10 to 12 dots, those in the case of InAs can be smaller or much larger depending on exact growth parameters prior to QD growth. Photoluminescence (PL) measurements show that while InAs QDMs provide room-temperature optical output that peaks at 1.1 eV, InP QDMs have no PL output, possibly due to crystal defects created by low-temperature processing associated with droplet epitaxy. Discussion on the practicality of our QDMs as material for intermediate band solar cells is also provided.
Laser-Induced Formation of Periodic Structures in Plasma Deposited Polymer Films Containing Au, Ag, and Cu Nanoparticles
Authors: Loeschner Katrin , Kiesow Andreas , Heilmann Andreas 
Published: April 2011

ABSTRACTThin polymer films containing metal nanoparticles were irradiated with linearly polarized femtosecond laser pulses. The resulting laser-induced periodic modification of the nanoparticle assemblies was studied by using scanning and transmission electron microscopy. The structure period Lambda is correlated with the applied laser wavelength lambda by Lambda = 0.7 lambda. The effect was observed for gold, silver and copper nanoparticles. Optical spectra of the laser-irradiated films show a clear dichroism.
Highly Charged Ion Modified Magnetic Tunnel Junctions
Authors: Grube Holger , Pomeroy J. M. , Perrella A. C. , Gillaspy J. D. 
Published: April 2011

ABSTRACTWe have used highly charged ions (HCIs) such as Xe44+ to modify ultrathin aluminum oxide barriers in magnetic tunnel junctions (MTJs) in order to controllably adjust their electrical properties independently of oxide thickness. We have reduced the resistance area (RA) product of our MTJ devices by up to three orders of magnitude down to our present measurement uncertainty limit of 30 Ω·μm2 by varying the HCI dose. Preliminary experiments indicate that HCI modified Co/Al2O3/Co MTJs have a reduced magnetoresistance (MR) of ≈ 1% at room temperature as compared to ≈ 10% for undosed devices. The goal of this effort is to fabricate a magnetic field sensor in current-perpendicular-to-plane (CPP) geometry with an RA optimized for hard drive read heads. This is an improvement over presently demonstrated CPP architectures based on giant magnetoresistance or tunnel junctions, whose RAs are either to low or too high.
Fabrication of Piezoelectric PZT Film Actuators on Thin Metal Plates Prepared by a Hydrothermal Method
Authors: Aoki Tuyoshi , Umemiya Shigeyoshi , Hida Masaharu , Satoh Keisuke , Kondo Masao , Kurihara Kazuaki 
Published: April 2011

ABSTRACTHydrothermal lead zirconate titanate (Pb(Zr,Ti)O3: PZT) films with a thick of about 10 μm on both a Ti foil and a Ti layer sputtered stainless steel (SS) foil were obtained. Both PZT films showed same morphology and crystalinity. After repeating the hydrothermal process, the films were formed to cantilever shape. A tip displacement measurement of the cantilevers was carried out in order to estimate transverse piezoelectric constant (d31). The obtained d31 value of the PZT films on Ti sputtered SS foils is -29 pm/V, which is larger than that on Ti foil (-24 pm/V). Amorphous layer consist of Pb and Ti was observed at the interfaces between the both PZT film and the Ti metals. The thickness of the layer for PZT film on Ti foil (350 nm) is thicker than that for PZT film on SS foil (200 nm). The relative permittivity of the layer is estimated to be small compared with that of PZT. Accordingly, the effective electric field for PZT layer is decreased. The deference of d31 values between the obtained PZT films is thought to be attributed to the thickness of amorphous layer.
Fabrication of Piezoelectric ZnO and PZT Films for FPW Device
Authors: Yoon Sang Hoon , Kim Dong-Joo 
Published: April 2011

ABSTRACTPiezoelectric ZnO and PZT films for acoustic wave device have been investigated. The films used for acoustic wave devices require textured structure, high piezoelectric coefficients, and high electromechanical coupling coefficients, because the piezoelectric films launch and receive the acoustic wave. We fabricated ZnO films by RF magnetron sputtering, and PZT films by chemical solution deposition (CSD). Results showed that uniform, dense and highly textured films were obtained under optimal process parameters. The film texture was controlled by modifying process parameters, such as gas kinds, gas ratio, and substrate type for sputtered ZnO films, and the presence of chelating agent, temperature of heat treatment, and substrate type for solution derived PZT films. Flexural plate wave (FPW) device has been successfully integrated onto 4-inch silicon wafers with optimized piezoelectric films.
Theoretical Investigation of the Band Alignment at the LaAlO3/SrTiO3 Interface
Authors: Lee Jaekwang , Demkov Alexander A. 
Published: April 2011

ABSTRACTEpitaxially grown oxide superlattices are attracting considerable attention due to their unusual properties and possible applications ranging from sensors to electronic devices [1]. We report a first-principles study of interfaces in the epitaxial LaAlO3/SrTiO3 system within density functional theory. We consider the electronic structure of the n-type interface, and compute the band alignment
Effect of Interfaces on the Properties of Polycrystalline Thin-Film PZT Ferroelectric Capacitors
Authors: Delimova Lyuba A. , Grekhov Igor , Mashovets Dmitri , Titkov Ilya , Afanasjev Valentin , Afanasjev Petr , Kramar Galina , Petrov Anatolii 
Published: April 2011

ABSTRACTA photocurrent directed opposite to ferroelectric (FE) polarization is observed in short-circuit thin-film polycrystalline Pt/PZT/Ir structures. The direction and magnitude of photocurrent are defined by the sign and magnitude of the FE polarization. A model based on a photovoltaic effect with characteristics determined by polarization of PZT grains is proposed. The model considers the field interaction of FE polarization charge with the charge carriers in intergranular PbO channel. Thin-film FE capacitor is considered as a photosensitive heterogeneous medium, where the conduction of PbO channels along PZT grain boundaries is controlled by FE polarization.