bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cathodoluminescence and microRaman study of GaN ELO structures
Authors: Martínez O. , Avella M. , Jiménez J. , Gérard B. , Galloway S. 
Published: April 2011

ABSTRACTEpitaxial Lateral Overgrowth (ELO) is an effective method to reduce dislocations in heterostructures with large lattice mismatch. This method has been widely used to improve the quality of GaN layers. We present herein a study of the properties of ELO GaN layers grown by HVPE from an MOVPE GaN buffer layer. Cathodoluminescence shows a strong enhancement of the luminescence emission in the ELO regions, where TEM has proven the absence of dislocations. Local cathodoluminescence spectra show that this enhancement is mostly due to the yellow luminescence band. Besides Donor-Acceptor Pair recombination bands are observed in the near band gap spectral range. Raman data show that the ELO layers present a good crystalline quality. The Raman spectra did not reveal the presence of free carriers in concentration high enough to allow the presence of Longitudinal Optic Phonon Plasmon Coupled modes. The results are discussed in terms of the incorporation of impurities in the ELO layers together with the formation of compensating deep acceptors, probably VGa.
Determination of the Plastic Behavior of Low Thermal Expansion Glass at the Nanometer Scale
Authors: Tejeda Richard , Engelstad Roxann , Lovell Edward , Anderson Anthony , Yang Dehua , Blaedel Kenneth 
Published: April 2011

ABSTRACTThe nanometer-scale plastic behavior of two low thermal expansion glasses (ULE® and Zerodur®) was determined through a combination of nanoindentation experiments and finite element modeling. The finite element models were then extended to investigate aspects of the performance of these materials as extreme ultraviolet lithography reticles.
Observation of the Morphology of ZnO:Al Nanocoating by Pulsed Laser Deposition on ZnS:Ag Phosphor for Degradation Repression
Authors: Nagare Sanshiro , Ollinger Michael , Singh Rajiv , Senna Mamoru 
Published: April 2011

ABSTRACTDegradation due to electron beam irradiation is a significant problem for ZnS based phosphors, particularly for flat panel displays. In this study, ZnS:Ag phosphor particles were coated by nanoparticles of ZnO:Al by pulsed laser deposition (PLD), to suppress the cathodoluminescence (CL) degradation process under electron bombardment at 15 k V. The pressure of the vacuum chamber and the deposition time were changed to control the morphology of the coating, i.e. thickness, continuity, and uniformity. CL degradation of the phosphors was slowed down for all cases by the nanocoating. The relationship between the CL degradation and the morphology of the coating material was examined by an SEM combined with a simultaneous CL measurement device. Degradation mechanisms were elucidated in terms of the morphology of the coating material and the change in the surface atomic species during irradiation of the electron beam.
Organic Light Emitting Devices Fabricated from Semiconducting Nanospheres
Authors: Piok Thomas , Wenzl Franz P. , Gamerith Stefan , Gadermaier Christoph , Patil Satish , Montenegro Rivelino , Kietzke Thomas , Neher Dieter , Scherf Ullrich , Landfester Katharina , List Emil J.W. 
Published: April 2011

ABSTRACTOrganic light emitting diodes (OLEDs) have been fabricated from organic semiconducting polymer nanospheres (SPNs) which have been deposited from aqueous dispersions. The active layer of the devices consists of a single, homogeneous layer of light emitting SPNs, as verified by optical, interferometric and surface probe measurements. Different batches of SPNs with different SPN diameters have been tested (69nm, 95nm, 126nm and 150 nm). All SPN-based OLEDs exhibit a light emission onset corresponding to the SPN energy gap (ca. 2.7 eV for m-LPPP, a semiconductingpara-phenylene ladder polymer). The low onset is attributed to field enhanced injection of charge carriers at the aluminum cathode due to the formation of stalactite-type nanostructures. A detailed comparison of the SPN-based and bulk semiconducting polymer films reveals no differences in the basic optoelectronic properties.
Deformation and Coble Creep of Nanocrystalline Materials
Authors: Pande C.S. , Masumura R. A. 
Published: April 2011

ABSTRACTModeling of strengthening by nanocrystalline materials need consideration of dislocation interactions and sliding due to Coble creep, both of which may be acting simultaneously. Such a mechanism is considered in this paper. It is shown that a model based on using Coble creep (with a threshold stress) for finer grains and conventional Hall-Petch strengthening for larger grains, appears to be most successful in explaining experimental results provided care is taken to incorporate into the analysis the effect of grain size distribution occurring in most specimens. A generalized expression relating yield stress to grain size is also proposed.
Fluorinated Single Wall Nanotube/Polyethylene Composites for Multifunctional Radiation Protection
Authors: Pulikkathara Merlyn X. , Shofner Meisha L. , Wilkins Richard T. , Vera Jesus G. , Barrera Enrique V. , Rodríguez-Macías Fernando J. , Vaidyanathan Ranji K. , Green Catherine E. , Condon Clay G. 
Published: April 2011

ABSTRACTFluorinated Single Wall Nanotubes (f-SWNTs) have been processed in polyethylene by an incipient wetting technique to achieve a well dispersed nanocomposite for radiation protection. In some cases, samples were further processed using the rapid prototyping method of extrusion freeform fabrication. Composites were exposed to 40 MeV proton radiation with a flux of about 1.7×107 protons/cm2/sec to a total fluence of 3×1010 protons/cm2.This exposure is consistent with a long-term space mission in low earth orbit. The samples were evaluated by means of Raman spectroscopy and thermogravimetric analysis (TGA). These results were compared to the unexposed composite and unfilled polymer samples. This study has focused on the stability of the nanotube composites when exposed to radiation and prior to hydrogen exposure. It was shown that the stability of the functional group is not constant with SWNTs produced by different processes and that radiation exposure is capable of defluorinating SWNTs in polyethylene.
Stoichiometry, crystallinity, and nano-scale surface morphology of the graded calcium phosphate-based bio-ceramic interlayer on Ti-Al-V
Authors: Long J. D. , Ostrikov K. , Xu S. , Ligatchev V. 
Published: April 2011

ABSTRACTA plasma-assisted concurrent Rf sputtering technique for fabrication of biocompatible, functionally graded CaP-based interlayer on Ti-6Al-4V orthopedic alloy is reported. Each layer in the coating is designed to meet a specific functionality. The adherent to the metal layer features elevated content of Ti and supports excellent ceramic-metal interfacial stability. The middle layer features nanocrystalline structure and mimics natural bone apatites. The technique allows one to reproduce Ca/P ratios intrinsic to major natural calcium phosphates. Surface morphology of the outer, a few to few tens of nanometers thick, layer, has been tailored to fit the requirements for the bio-molecule/protein attachment factors. Various material and surface characterization techniques confirm that the optimal surface morphology of the outer layer is achieved for the process conditions yielding nanocrystalline structure of the middle layer. Preliminary cell culturing tests confirm the link between the tailored nano-scale surface morphology, parameters of the middle nanostructured layer, and overall biocompatibility of the coating.
Compressive Behavior for Surface-Nanocrystallized Al-Alloy Material
Authors: Wei Yueguang , Zhu Chen , Wu Xiaolei 
Published: April 2011

ABSTRACTMechanical behavior of the surface-nanocrystallized material fabricated by the ultrasonic shot peening method is investigated experimentally and theoretically. In the experimental research, based on microscopic observations, the compressive specimens are designed and machined considering the material features, and the compressive experiments are performed. Furthermore the compressive stress-strain curves are measured. In the theoretical research, a microstructure cell model is presented considering the material microscopic organization observed from experiments, and the compressive stress-strain relations are simulated. Both experimental and theoretical results display the strong size effect on the material behavior.
Material Properties and Process Compatibility of Spin-on Nano-foamed Polybenzoxazole for Copper Damascene Process
Authors: Enoki Takashi , Maejima Kenzo , Saito Hidenori , Katsumura Akifumi 
Published: April 2011

ABSTRACTWe have developed nano-foamed OxD which has good properties such as dielectric constant=2.2, homogeneous distributed nano pores, smooth surface based on polybenzoxazole chemistry and nano-foaming technology. The nano-foamed OxD also has excellent thermal stability, chemical stability and etching property. The developed nano-foamed OxD is one of good candidates for copper damascene structure to achieve shrinking dimensions of future semi-conductor devices.
Synthesis of Titania coated Alumina Particles by a Hybrid Sol-gel Method
Authors: Schmidt A.D. , Majumder S.B. , Dobal P.S. , Katiyar R.S. , Agrawal D.C. 
Published: April 2011

ABSTRACTModifying their surface with a coating of another ceramic material can dramatically alter the properties of ceramic particles. In the present work we have demonstrated that the Al2O3 particles can be successfully coated by TiO2 using a novel sol-gel technique. The nature of these coatings was predicted on the basis of scanning electron microscopy imaging in conjunction with the micro-Raman scattering measurements. The surface morphology of these particles shows that either individual or group of sub-micron alumina particles are coated with the nano-crystalline titania particles. The thickness of the titania coating could be varied by changing the precursor sol concentration. Amorphous titania was converted to anatase phase at 400°C and upon further heating it started transforming to rutile phase, and both these phases coexisted in the coated particles that were heat treated up to 800°C. The mechanical strength of the titania coating was measured qualitatively by ultrasonicating the coated powders for longer duration to observe that titania coatings are strongly adhered with the alumina particles.
Processing of Clay/Epoxy Nanocomposites with A Three-Roll Mill Machine
Authors: Yasmin Asma , Abot Jandro L. , Daniel Isaac M. 
Published: April 2011

ABSTRACTIn the present study, a three-roll mill machine was used to disperse/exfoliate the nanoclay particles in an epoxy matrix. The compounding process was carried out with varying mixing time and concentrations of clay particles (1 to 10 wt.%). It was found that the longer the mixing time, the higher the degree of intercalation. Mechanical properties, XRD and TEM were used to characterize the nanocomposites. Elastic modulus was found to increase with increasing clay content, however, the tensile strength was not found to vary accordingly. Compared to conventional direct and solution mixing techniques, the compounding of clay/epoxy nanocomposites by a three-roll mill was found to be highly efficient in achieving higher levels of intercalation/exfoliation in a short period of time and also environmentally friendly.
Characterization of Metal-Oxide Nanoparticles: Synthesis and Dispersion in Polymeric Coatings
Authors: Sung Li-Piin , Scierka Stephanie , Baghai-Anaraki Mana , Ho Derek L. 
Published: April 2011

ABSTRACTMetal-oxide nanoparticles can be used to optimize UV absorption and to enhance the stiffness, toughness, and probably the service life of polymeric materials. Characterization of the nano- and microstructure dispersion of particles is necessary to optimize the structure-property relationships. Characterizations of both TiO2 particles dispersed in an acrylic-urethane matrix and TiO2 nanostructured films obtained through sol-gel synthesis are discussed. Experimental methods include microscopy (confocal, AFM) and small angle neutron scattering (SANS). Results from SANS experiments, which yield information about the cluster size of the nano-TiO2 particles and the spatial dispersion in various nanoparticle/polymer samples are presented and compared to the results of microscopy studies.
Adhesion of HVOF Sprayed Diamond-Containing Nanostructured Composite Coating
Authors: Kireitseu Maksim V. , Nemerenco Ion 
Published: April 2011

ABSTRACTIn the present paper mechanical properties of HVOF sprayed diamonds-containing aluminum oxide composite coating have been investigated. Crystallographic and morphologic texture was measured. Diamonds nanoparticles may improve fracture resistance of aluminum oxide-based coating. Investigations of thermally sprayed coatings by the test revealed high accuracy, speed and reliability of the test. It is also thought that the composite coatings will have better thermal conductivity and thermal shock resistance than that of aluminum oxide-based coatings.
Synthesis of Zeolite Y Nanocrystals from Clear Solutions
Authors: Shen Y. , Manning M.P. , Warzywoda J. , Sacco A. 
Published: April 2011

ABSTRACTSynthesis of zeolite nano-sized crystals has attracted much attention because of their properties, some of which maybe different from the normal sized crystals. A synthesis adopted by Voltchev and Mintova was used as the starting point: 0.078 Na2O: 4.35 SiO2: 1.0 Al2O3: 2.35 (TMA)2O: 248 H2O. Both the silicate and aluminum starting solutions were clear. Zeolite Y nanocrystals with zeolite A nanocrystals as an impurity were obtained with a size range of 20–100 nm through this synthesis technique.
Nanoindentation Technique at Investigating of Aluminum Oxide - CrC Nanoparticles Composite Coating
Authors: Kireitseu Maksim V. 
Published: April 2011

ABSTRACTIn this paper fatigue and fracture of Al-Al2O3-CrC nanostructured composite coatings was investigated by nanoindentation technique and in-situ experiments performed by a scanning electron microscope to permit examination of freshly exposed surfaces. Crystallography and morphological textures were characterized and fracture resistance was measured. CrC layer improves fracture resistance of alumina layer. CrC layer produced by pyrolitic deposition (CVD) may effectively heal pores and defects of alumina layer. It resulted in high load rating of the composite coating. Experiments reveal that in all cases, the detection of an acoustic signal corresponded to the appearance of a circular cracks seen on surface; in a very few cases, examination of surface after detection of a signal revealed presence of two ring cracks. Degree of toughening associated with crack healing is determined by a number of healed defects and an effectiveness of an individual healing.
The Improvement of Temperature Coefficient of Frequency in Thin Film Bulk Acoustic Wave Resonator using Secondary Harmonics
Authors: Yoshino Yukio , Takeuchi Masaki , Yamada Hajime , Goto Yoshihiko , Nomura Tadashi , Makino Takahiro , Arai Seiichi 
Published: April 2011

ABSTRACTWe have succeeded in making an 870MHz-range thin film bulk acoustic wave (BAW) resonator that has a small temperature coefficient of frequency (TCF) using secondary harmonics. The 870MHz-range BAW resonator has been requested to have nearly zero TCF, because it will be used in an oscillator for remote keyless entry systems. The BAW resonator has composite structure that consists of Al electrodes and ZnO/SiO2. We directed our attention to the fact that ZnO and Al have negative TCF, and SiO2 has a positive one. It is theoretically possible to make zero TCF BAW resonators by optimizing the thickness ratio of ZnO and SiO2. However, using fundamental resonance, TCF is so sensitive to the thickness ratio that it cannot be easily controlled by MEMS techniques. We founds in finite element method simulation and confirmed by experiment that the TCF of secondary harmonics has a local minimum when changing the ZnO/SiO2 thickness ratio. As the result, a nearly zero TCF resonator without strict control of ZnO/SiO2 thickness ratio has been realized by adopting Al/ZnO/SiO2/ZnO/Al/SiO2 structure and combining thermal oxidized Si and sputtered SiO2. The resonator has the TCF of -1.86ppm/degree in the range of −40 to 85 degrees centigrade.
High Temperature Behavior of Polysilicon
Authors: Oh Chung-Seog , Coles George , Sharpe William N. 
Published: April 2011

ABSTRACTThe polysilicon elements of thermal actuators can reach temperatures high enough to cause permanent deformation. A fundamental understanding of the constitutive behavior is necessary for intelligent design and life prediction, but mechanical testing at high temperatures is especially challenging at the micron level.This paper describes techniques for testing freestanding thin-film polysilicon specimens in tension at temperatures up to 700°C. Strain is measured directly on the specimens by laser interferometry from platinum markers. The complete stress-strain curve can be obtained as well as strain versus time for creep tests. Initial results show that polysilicon is ductile at temperatures above 500°C and can have a high creep rate.
Nonuniformity in Selective Anodization of Silicon and its Application to Micro-Tip Fabrication
Authors: Uehara S. , Negishi N. , Matsubara T. 
Published: April 2011

ABSTRACTCharacteristics of selective anodization of p+-type Si have been studied. Temporal evolution of the etching front was visualized by periodic porosity modulated anodization. The etching front proceeded inside along the bottom of mask making its angle with the mask bottom face sharper and sharper. It was also found that the etching front proceeds forming a specifically angled facet. Selective anodization was applied to form Si micro-tips. Proper time of anodization for p+-type Si substrate with an n-type circular shape mask left a Si micro-tip formed on the substrate. A high resolution SEM observation revealed that the apex of the tip was composed of {110} facets.
Channel Epitaxy of 3C-SiC on Si Substrates by CVD
Authors: Nishino S. , Okui Y. , Jacob C. , Ohshima S. 
Published: April 2011

AbstractEpitaxial growth of 3C-SiC on Si substrates has been studied for many years, however an important issue is how to reduce the high density of interfacial defects. Channel epitaxy is the growth of a film on small channeled windows and is related to selective growth. Channel epitaxy of 3C-SiC grown on the seed 3C-SiC previously deposited on patterned Si substrates was achieved via CVD using hexamethyldisilane (HMDS). The proper selection of mask materials was also key to achieve channel epitaxy. Thermal oxide, silicon nitride and thin SiC masks were tried. Thin SiC was an effective mask to achieve selective growth at 1350°C. Smooth surface morphology was observed on both the channel regions and the mask regions at the growth temperature of 1350°C. Scanning electron microscopy revealed coalescence of the laterally grown regions via channel epitaxial growth of 3C-SiC.
3C-SiC Monocrystals Grown on Undulant Si(001) Substrates
Authors: Nagasawa Hiroyuki , Yagi Kuniaki , Kawahara Takamitsu , Hatta Naoki 
Published: April 2011

ABSTRACTA novel technique to reduce planar defects in 3C-SiC is to grow it on “undulant-Si” substrates, on which the surface forms countered slopes oriented in the [110] and [110] directions. In the initial stage of 3C-SiC growth, step flow epitaxy occurs on each slope of the substrate, reducing the anti-phase boundaries. Then, the stacking faults in the (111) and (111) planes are gradually annihilated by combining with counter-stacking faults, while those parallel to (111) and (111) vanish. The freestanding 3C-SiC exhibits anisotropy in its electrical properties. The origin of the anisotropy in electrical properties is discussed by referring to the results of X-ray diffraction study.
Thermal stress as the major factor of defect generation in SiC during PVT growth
Authors: Cherednichenko D. I. , Drachev R. V. , Khlebnikov I. I. , Deng X. , Sudarshan T. S. 
Published: April 2011

ABSTRACTNumerical simulations of the thermal stress distribution in a SiC boule 2” in diameter and 1” long grown by conventional PVT technique were performed based on the temperature field distribution in a resistively heated growth reactor that was simulated using the GAMBIT-2.0.4/FIDAP-8.6.2 software package. Analysis of the simulation results revealed the existence of a thermal stress, which was excessively nonuniform in distribution and whose magnitude exceeded the value of the critical resolved shear stress of 1.0 MPa by a factor of 2. The high stress initiated plastic deformation and the high temperature provoked the intense self-diffusion processes. The combination of these factors alters the mechanism of plastic deformation, significantly affecting the structural quality of the growing crystal. The influence of self-diffusion processes initiating the formation of interstitial atoms and vacancies; stacking fault formation as a result of the nonconservative motion of the basal plane dislocations; and micropipe formation from the dislocation groups piled up at silicon and carbon second phase inclusions are also discussed.
Ion Implantation Induced Deep Defects in n-type 4H-Silicon Carbide
Authors: Evwaraye A. O. , Smith S. R. , Mitchel W. C. , Capano M. A. 
Published: April 2011

ABSTRACTAluminum (Al) and argon (Ar) ions were implanted into n-type 4H-SiC epitaxial layers at 600 °C. The energy of the ions was 160 keV at a dose of 2 × 1016 cm-2. After annealing at 1600 °C for 5–60 minutes, Schottky diodes were fabricated on the ion implanted samples. Deep Level Transient Spectroscopy (DLTS) was used to characterize ion implantation induced defects. A defect at EC-0.18 eV was observed in the Al+ implanted devices annealed for five and fifteen minutes. However, annealing for 30 minutes produced an additional deeper defect at EC -0.24 eV. This defect annealed out after a sixty minute anneal. DLTS studies of Ar+ implanted devices showed six defect levels at EC -0.18 eV, EC -0.23 eV, EC -0.31 eV, EC -0.38eV, EC -0.72 eV, and EC -0.81eV. These defects are attributed to intrinsic-related defects. It is suggested that “hot” implantation of Al+ inhibits the formation of intrinsic-related defects. While “hot” implantation of Ar+ into 4H-SiC does not reduce the concentration of the vacancies and interstitials.
SiO2/SiC Interface Properties on Various Surface Orientations
Authors: Yano Hiroshi , Hirao Taichi , Kimoto Tsunenobu , Matsunami Hiroyuki 
Published: April 2011

ABSTRACTThe interface properties of MOS capacitors and MOSFETs were characterized using the (0001), (1120), and (0338) faces of 4H-SiC. (0001) and (1120) correspond to (111) and (110) in cubic structure. (0338) is semi-equivalent to (100). The interface states near the conduction band edge are discussed based on the capacitance and conductance measurements of n-type MOS capacitors at a low temperature and room temperature. The (0338) face indicated the smallest interface state density near the conduction band edge and highest channel mobility in n-channel MOSFETs among these faces.
A semi-empirical model for electron mobility at the SiC/SiO2 interface
Authors: Saks Nelson S. 
Published: April 2011

ABSTRACTThe mobility of electrons in inversion layers at SiC/SiO2 interfaces μinv has been characterized in 4H- and 6H-SiC using Hall effect measurements. In order to understand the cause of the low mobilities typically observed in SiC MOS devices, a semi-empirical mobility model has been developed based on a previous model for silicon inversion layers. Using this model, two scattering mechanisms, surface phonon and Coulomb scattering from high densities of electrons trapped at the SiC/SiO2 interface, are found to account reasonably well for the behavior of the mobility. The model employs a changing density of trapped electrons as a function of gate voltage to accurately model Coulomb scattering. Surprisingly, evidence of surface roughness scattering is not observed in any SiC MOS device.