bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ferromagnetic Ordering at Room Temperature in ZnO:Co Nanoparticles
Authors: Chaudhary Sujeet , Bhatti Kanwal Preet , Kundu Shankhmala , Kashyap Subhash C. , Pandya Dinesh K. 
Published: April 2011

ABSTRACTIntrinsic room temperature ferromagnetism is reported in sequentially sintered (in air ambient) nanocrystalline ZnO:Co (1 to 10 at% Co) samples prepared by chemical route. The Curie temperature of the ZnO:Co ferromagnetic samples is determined to be ∼495°C. The saturation magnetization of the ferromagnetic phase is found to first increase with Co concentration (up to 5%) and then decrease. It is also found to decrease with increase in sintering temperature up to 800°C; there after it remains unaffected till 1000°C. The d-d band transitions in the optical spectrum confirm that Co2+ substitutes Zn2+ in the ZnO lattice. A plausible explanation of the observed ferromagnetic ordering is presented in terms of Bound Magnetic Polarons model.
Magnetic Properties of ZnO:Ni Aerogel Nanopowders: Effect of Thermal Treatments
Authors: El Mir Lassaad , von Bardeleben H.Jurgen , Saadoun M , Ben Mahmoud Aroussi , Cantin Jean-Louis 
Published: April 2011

ABSTRACTWe report the elaboration of Ni doped ZnO nanoparticles prepared by a sol-gel processing technique. In our approach the water for hydrolyse was slowly released by esterification of the metal acetate with methanol followed by a supercritical drying in ethyl alcohol. Doping concentrations between 5 and 25 at% have been investigated. In the as-prepared state the powders with an average particle size of 30nm present ferromagnetic properties; thermal annealing in the 500°C to 700°C temperature range in air or oxygen modifies the magnetic properties. We ascribe the observed ferromagnetism to the presence and transformation of Ni based secondary phases.
Transport Properties and Conduction Band Offset of n-ZnO/n-6H-SiC Heterostructures
Authors: Alivov Yahya , Bo Xiao , Qian Fan , Johnstone Daniel , Litton Cole , Morkoç Hadis 
Published: April 2011

ABSTRACTThe conduction band offset of n-ZnO/n-6H-SiC heterostructures fabricated by rf-sputtered ZnO on commercial n-type 6H-SiC substrates has been measured. Temperature dependent current-voltage characteristics, photocapacitance, and deep level transient spectroscopy measurements showed the conduction band offsets to be 1.25 eV, 1.1 eV, and 1.22 eV, respectively.
Influence of Annealing Temperature on ZnO Thin Films Prepared by Single and Multi-step Sol-gel Processes
Authors: Kelly Koh Lee Huat , O'Brien Shane , Lovera Pierre , Redmond Gareth , Crean Gabriel M 
Published: April 2011

ABSTRACTZnO thin films were prepared on borosilicate glass from both single- and multi- step coating deposition of a sol-gel prepared with anhydrous zinc acetate [Zn(C2H3O2)2], monoethanolamine [H2NC2H4OH ] and isopropanol. ZnO films prepared over a range of zinc acetate concentrations, for a fixed annealing temperature, showed that sol-gels prepared with a 0.3M zinc acetate concentration resulted in the formation of films with the greatest degree of c-axis orientation. In this study, a detailed investigation of the influence of process annealing temperature over the range 450 – 550°C on the microstructural, physical, electronic and optical properties of these single and multi-step ZnO thin films around this 0.3M zinc concentration set point is presented. X-ray analysis showed that all single-step deposition thin films were preferentially orientated along the [002] c-axis direction of the crystal. In contrast, only the multi-layer film annealed at 550°C showed similar preferential orientation. All single step deposited films showed a similar average optical transmittance above 87%, independent of annealing temperature. The transmittance of the multi-step films was shown to be strongly correlated to the degree of c-axis orientation. The optical band-gap energy was evaluated to be 3.298 – 3.316 eV for all samples. The photoluminescence spectra of the single layer ZnO films showed a strong emission centred at ca. 405 nm, which blue shifted with increasing annealing temperature. The multi-layer ZnO samples emitted throughout the UV and the visible range, with the samples prepared at 500 and 550°C showing the expected ZnO emission peak at 380 nm. Despite being thicker, the emission from the multi- layer samples was less than measured for the single layer samples. The effect of sol-gel annealing temperature and deposition process on film microstructure, morphology, electrical resistivity and optical transparency is detailed.
The Impact of Hydrogen Plasma Treatments at Moderate Temperatures on Sintered Zinc Oxide Samples - Evidence for Hydrogen Induced Nano-Void Formation
Authors: Job Reinhart 
Published: April 2011

ABSTRACTUsing μ-Raman spectroscopy (μRS) analyses, the impact of hydrogen plasma treatments on sintered zinc oxide (ZnO) samples was investigated. H-plasma exposures (150 W, 13.56 MHz) were carried out for 1 hour at substrate temperatures between 250 °C and 500 °C. μRS reveals that plasma hydrogenated ZnO samples are more defective than non-treated ones. On one hand non-specified defect species are created with a maximal density upon plasma hydrogenation at 350 °C, on the other hand the formation of oxygen vacancies (VO) can be traced. The density of VO defects, appearing upon H-plasma exposure, is not significantly correlated to the applied substrate temperatures. μRS also reveals vibration modes of H2 molecules trapped in nano-voids. The μRS results indicate that those nano-voids are created by the coalescence of VO defects.
Investigation of Nitrogen Induced closely coupled Sb based Quantum Dots for Infrared Sensors Application
Authors: Kim Seongsin M , Hatami Fariba , Yuen Homan B , Harris James S 
Published: April 2011

ABSTRACTWe report the growth and structural properties of InSb and InSb:N quantum dots on InAs and GaAs substrates. Strain induced, self-assembled quantum dots are grown using solid-source molecular beam epitaxy. For improved growth control, we developed a growth technique similar to atomic layer epitaxial methods. InSb and InSb:N multiple quantum dots formed on both InAs and GaAs. We explain the formation of multiple quantum dots by the anisotropic distribution of strain energy within the quantum dot, the long adatom lifetime during atomic layer epitaxy, and the low bond energy of InSb. Nitrogen incorporation during formation of quantum dots changes surface energy barrier and causes anisotropic distribution of strain energy, results in formation of closely coupled multiple quantum dots in <110> orientation. We obtained mid infrared luminescence around 3.6 μm from InNSb QDs grown on InAs substrate, where it exhibits relatively low efficiencies of nitrogen incorporation compared to the quantum well structure.
A Voltage-Tunable Two-Color InGaAs/AlGaAs Quantum well Infrared Photodetector
Authors: Passmore Brandon , Liang Jie , Zhuang Da , Manasreh Omar , Kunets Vasyl , Salamo Greg 
Published: April 2011

ABSTRACTA voltage-tunable two-color multiple quantum well infrared photodetector was fabricated with two bands at 6.0 and 10.3 ìm. The molecular beam epitaxy grown structure consists of two stacks of n-type InGaAs wells and GaAs/AlGaAs superlattice barriers. The 6.0 ìm band was found to be dominant at low bias voltages while the 10.3 ìm band is dominant at high bias voltages. The optical absorption measurements confirm the presence of both bands. Furthermore, the transfer matrix method is used to estimate the peak position energies of the intersubband transitions in the two stacks.
Synthesis and Electronic Application of Germanium Nanocrystals in Silicon Oxide Matrix
Authors: Choi Wee Kiong , Chim Wai Kin , Chew Han Guan 
Published: April 2011

ABSTRACTThe size of germanium (Ge) nanocrystals in a trilayer memory device structure was controlled by varying the thickness of the middle co-sputtered Ge plus silicon oxide layer. Such confinement of nanocrystals was not effective in a trilayer structure with a pure Ge middle layer. Significant diffusion of Ge atoms through the tunnel oxide or rapid thermal oxide (RTO) layer and into the silicon substrate was observed when the RTO layer thickness of the trilayer structure was reduced. This resulted in no (or very few) nanocrystals formed in the system. A higher charge storage capability was obtained from devices with a thinner RTO layer.
Temperature Dependence of Optical Transitions of One Dimensional InGaAs/GaAs Quantum Structures
Authors: Ma Zhixun , Holden Todd , Wang Zhiming , Mao Samuel S. , Salomo Gregory J. 
Published: April 2011

ABSTRACTWe have studied the temperature dependence of CER spectra of layered InGaAs QWRs and QDCs and found strain-induced splitting of lh and hh states occur in both InGsAs and GaAs layers. By fitting experimental data using Varshni law and Bose-Einstein type relation, various parameters are obtained, which are similar to those of bulk GaAs. We pointed out that a caution must be excised when extracting the electron-phonon interaction parameters by subtracting the thermal dilation part from the experimental data of the embedded semiconductor microstructures because in these structures the temperature-induced lattice-dilation may produce additional strain besides the lattice mismatch.
Vertically self-organized gold nanoparticles in amorphous alumina matrices
Authors: Jin Chunming , Zhou Honghui , Wei Wei , Narayan Roger J. 
Published: April 2011

ABSTRACTIn this study, self-organized growth of gold nanoparticles dispersed in amorphous alumina matrices was investigated. Au/Al2O3 multilayered structures were grown on silicon (001) substrates using pulsed laser deposition. Vertical ordering of particles was examined with cross-sectional transmission electron microscopy and image Fourier transformation. Self-organization of gold nanoparticles along the vertical direction was observed in the samples grown at room temperature and 320 °C. This process occurred through two-different growth modes, known as top-on-top growth and top-on-middle growth. The driving force for the vertical ordering was attributed to long-range elastic interactions among nanoparticles during the film deposition process.
Defects Study in Gold Surfaces produced by Ion Bombardment
Authors: Carrasco Esther , de la Fuente O. Rodríguez , Rojo J.M. , García M.A. , de Julián C. 
Published: April 2011

ABSTRACTWe present new experimental results regarding the surface defect structure of ion bombarded gold surfaces. We report annealing mechanisms of surface defects on reconstructed Au(001) after medium fluence ion bombardment. We show how (001) and (111) gold surfaces can be nanostructured with a certain degree of lateral order by means of high fluence and high flux ion irradiation. We prove that ion irradiation nanostructuring strongly changes optical (plasmonic) properties of gold polycrystalline thin films.
Effects of P Content on Morphology of Nanocrystals Induced by FIB Irradiation in Ni-P Amorphous Alloy
Authors: Sato Koji , Ishiyama Chiemi , Sone Masato , Higo Yakichi 
Published: April 2011

ABSTRACTWe studied the effects of phosphorus (P) on Ni nanocrystalline morphology formed by focused ion beam (FIB) irradiation for Ni-P amorphous alloy thin films. The P content in the amorphous alloy was varied from 8 to 12 wt.%. The nanocrystals induced by the FIB irradiation for Ni-11.8, 8.9, 7.9 wt.% amorphous alloy had an f.c.c. structure and showed unique crystallographic orientation relationships to the geometry of the focused ion beam, that is, {111}f.c.c. parallel to the irradiated plane and <110>f.c.c. parallel to the projected ion beam direction, respectively. The Ni nanocrystals precipitated like aggregates with decreasing of the P content. These results represent that the P content does not affect crystallographic orientation relationships, while influences the precipitation distribution of Ni nanocrystals generated by the FIB irradiation.
Novel Methods to Reduce Pattern Size and Pitch for Data Storage Using Electron Beam Writing
Authors: Lu Zhou , Cartwright A. N. 
Published: April 2011

ABSTRACTPattern size and pitch are two major factors that directly affect the capacity of a data storage unit. Electron beam lithography, because it can be used for direct writing at the nanometer scale, is one of the potential candidates to fabricate ultra-fine and ultra-compact patterns for the next generation of data storage media.In the paper, we present methods to reduce the pattern size and pitch written by electron beam on positive tone resist Poly(methylmethacrylate) (PMMA). The first method uses a writing dose which is much lower than the critical dose of the PMMA. However, in this technique, the distance between the adjacent writing spots (which are approximately Gaussian in spatial extent) is finely adjusted until the partially overlapping Gaussian functions form a contour with periodic dose peaks higher than the critical dose. This overlapping exposure results in a periodic exposure of the PMMA. Most importantly, this writing strategy, using the overlapping of low dose Gaussian beams, results in patterns with smaller size and pitch compared to the conventional methods that use a higher writing dose than the critical dose. To further improve the results, we use ultrasonic development in combination with cold development to greatly increase the resist contrast. The increased contrast results in smaller pattern sizes, and enables smaller pattern pitches, as well as improving pattern uniformity and reproducibility.Finally, as a demonstration of the technique using a conventional beam voltage of 15kV, we achieve ultra-fine and high density patterns with ∼10nm linewidths and 50nm in pitch, which corresponds to a storage capacity near 200 billion bits/inch2. In comparison, standard techniques (using a dose slightly higher than the critical dose and normal development strategy), we can only obtain patterns with linewidths of about 20-30nm and pitch of about 100nm.
Impact of planarization sheet addition on full wafer printing uniformity
Authors: Leveder Tanguy , Landis Stefan , Davoust Laurent , Chaix Nicolas 
Published: April 2011

ABSTRACTUniformity of nanoimprint lithography has been quantitatively studied through the ability to replicate regular lines arrays by wafer-to-wafer imprint. Two statistic coefficients have been defined in order to quantify the local uniformity and the ability to identically imprint two similar areas respectively. Those coefficients enable to compare different imprint profiles in terms of uniformity and to point out the efficiency of soft layers insertion into the imprint stack.
Development of 3-D Magnetic Nano-Arrays by Electrodeposition into Mesoporous Silica Films
Authors: Manning Jason , Campbell Roger , Bakker Martin Gerard , Li Xuefa , Lee Dong Ryeol , Wang Jin 
Published: April 2011

ABSTRACTThe development of periodic nanostructures fabricated by self-assembly of surfactants and block co-polymers has opened up the possibility of generating periodic magnetic nanostructures of types not accessible by self-assembly of nano-particles. The fabrication of mesoporous silica thin films around self-assembled block co-polymers is well established. Common structures for such films are SBA-15 which consists of hexagonal arrays of cylindrical pores and SBA-16 which has face centered arrays of spherical voids. These pores are connected by 1-2 nm thick flaws in the continuous silica phase producing an effectively continuous porous phase. After removal of the block co-polymer template, electrodeposition into the mesoporous silica thin films produces arrays of 5-10 nm diameter nano-wires and nano-particles. We have demonstrated that such materials can be fabricated on a wide range of metal substrates. Characterization by Scanning Electron Microscopies shows that the mesoporous silica is well ordered over micron scale areas. Grazing Incidence Small Angle X-ray Scattering (GISAXS) studies shows diffraction spots, consistent with the entire film being well ordered. GISAXS also shows that the mesoporous silica films survive removal of the template and electrodeposition of nickel and cobalt into the mesoporous silica films. Such films are of interest for their magnetic properties, as the nanophase and scale can be independently varied. Further, the presence of nanowires inside an insulator suggests that these films might also be of interest as the current confining element for Confined Current Path-Current Perpendicular to Plane GMR sensors.
Nanoelectrode Lithography
Authors: Yokoo Atsushi , Namatsu Hideo , Oda Masatoshi 
Published: April 2011

ABSTRACTNanoelectrode lithography is a pattern duplication method which combine template and electrochemical reaction. With the nanoelectrode lithography, electrochemical reaction occurs along with the conductive area of the template, and oxide pattern can be directly fabricated on a surface of semiconductor or metal layer. This "Resist-less patterning" method may have advantage for precise patterning in the future.
Ab Initio Investigation of a CoFeB/MgO/CoFeB Interface
Authors: Domingos Helder Sousa , Martins José Julio 
Published: April 2011

ABSTRACTWe have carried out density functional calculations on a CoFeB/MgO/CoFeB interface with amorphous electrodes. The interface was shown to be stable with 4 mono-layers (ML) and to contain spin-polarized metal-oxigen bonds at the interface. The interfacial energy was estimated, to be used as a comparative measure of stability. In addition, the exchange-coupling indicated a favouring of the anti-paralell magnetization configuration with respect to the paralell for 4 ML.
Electron Holography of Ferromagnetic Nanoparticles Encapsulated in Three-Dimensional Arrays of Aligned Carbon Nanotubes
Authors: Koziol Krzysztof K. , Kasama Takeshi , Dunin-Borkowski Rafal E. , Barpanda Prabeer , Windle Alan H. 
Published: April 2011

ABSTRACTClosely-spaced ferromagnetic nanoparticles are of interest for applications that include data storage, magnetic imaging and drug delivery. Here, we use off-axis electron holography and micromagnetic simulations to study the magnetic properties of iron nanoparticles encapsulated in three-dimensional arrays of carbon nanotubes. The nanotubes constrain the shapes, sizes and separations of the nanoparticles, as well protecting them from oxidation. We record magnetic induction maps from individual particles that each contain a single magnetic domain. We also discuss the use of electron holography to assess magnetostatic interactions between adjacent particles.
Enhancement of Plasmon Propagation Length Using Metamaterials
Authors: Brandon David , Krokhin Arkadii , Neogi Arup 
Published: April 2011

ABSTRACTWe propose using a strongly anisotropic dielectric as a substrate for a thin metallic film along the boundary of which surface plasmon excitations may propagate. We show that the propagation range of surface plasmons is increased if the substrate is a birefringent dielectric crystal with a properly oriented optical axis. The increase of the propagation range depends on the degree of anisotropy, and, consequently, it turns out to be small for substrates of natural optical crystals, where anisotropy is weak. However, in specially designed photonic crystals, the anisotropy may be very strong, thus leading to appreciable increase of the propagation range. A photonic-crystal substrate, being a medium with nonlinear dispersion, also affects the dispersion law of the surface plasmon. All these effects may be used in order to increase the efficiency of modern plasmonic and optoelectronic devices.
Screen Printed Frequency-Selective Surfaces on Rigid, Flexible and Elastic Substrates
Authors: Kistenmacher Thomas , Francomacaro Shaun , Brawley Ben , Awadallah Ra'id , Vichot Paul , Fitch Michael , Spicer Jane , Wickenden Dennis 
Published: April 2011

ABSTRACTA series of frequency-selective surface (FSS) arrays based on nested split-ring triangle resonators have been fabricated using screen printing. A silver-filled polymer thick film (PTF) paste was selected as the active medium for the FSS arrays as it has good compatibility with the various substrates employed and is in itself naturally flexible. Substrates included FR4 boards and polyimide (PI), polyethylene terephthalate (PET) and silicone sheeting. Compared to arrays fabricated from Cu-clad FR4 board, the screen-printed arrays are resonance shifted owing to the magnitude of the dielectric constant and thickness of the various substrates. In addition, the quality factors of the screen-printed arrays are reduced compared to those fabricated from the more conductive Cu resonators. Despite these limitations, screen-printed arrays have considerable potential as components for low-cost flexible and conformal microwave devices.
Ferroelectric and Magnetic Characterization of Ferroic Pb(Fe0.5Nb0.5)O3 Ceramics
Authors: Raymond Oscar , Font Reynaldo , Alvarez Guillermo , Portelles Jorge , Srinivasan Gopalan , Siqueiros Jesús M. 
Published: April 2011

ABSTRACTSingle phase multifunctional materials such as Pb(Fe0.5 Nb0.5)O3 (PFN), where ferroelectric and magnetic order coexist, are very promising and have great interest from the academic and technological points of view. PFN ceramics have been prepared from different kinds of FeNbO4 precursors with either monoclinic or orthorhombic structures. Crystallographic, compositional and surface morphological studies and the temperature-frequency response carried out and reported in previous works are summarized. Ferroelectric hysteretic, magnetic and magnetoelectric behaviors were measured. The remanent polarization (Pr) and coercive field (EC) as functions of temperature and external electric fields (Eext) were determined. Measurements of magnetic susceptibility (χm) exhibited antiferromagnetic order and, above the Núel point near 122 °K, Curie–Weis behavior; whereas a weak ferromagnetic observed from electron paramagnetic resonance (EPR) is discussed. However, magnetoelectric effects were not observed. Ferroelectric and magnetic behaviors, as functions of the kind of precursor used in the preparation, are discussed and correlated with the previous dielectric characterization where microstructural and equivalent circuit models were established using the impedance spectroscopy technique.
Cross-Sectional Observation of Nano-Domain Dots Formed in Congruent Single-Crystal LiTaO3
Authors: Cho Yasuo , Daimon Yasuhiro 
Published: April 2011

ABSTRACTCross-sectional shapes of reversal nano-domain dots formed in a congruent LiTaO3 single-crystal recording medium were studied by scanning nonlinear dielectric microscopy (SNDM). Images obtained by SNDM measurements confirm that reversal nano-domain dots penetrate through the entire sample. The domain wall thickness was evaluated by the cross-sectional measurement results. The variation of the domain wall thickness as a function of sample thickness and of depth position was evaluated. It was found that thinner samples have a tendency to have thinner domain walls, and it was confirmed that the domain wall thickness at the bottom of the sample was thinner than at the front surface of the sample. A discussion of the measured result is also provided.
Dielectric Properties of Cr2O3 Doped (Ba,Sr,Ca)TiO3 Ceramics for Tunable Microwave Devices
Authors: Qin Bing , Jin Dengren , Chen Jinrong , Meng Zhongyan 
Published: April 2011

ABSTRACTCr2O3-doped (Ba0.55Sr0.4Ca0.05)TiO3 ceramics were fabricated by the mixed-oxide method. Their dielectric properties were investigated with the variation of Cr3+ doping concentrations (0∼2.0mol%). All the BSCT specimens owned dense and homogeneous structure. Doping of Cr3+ could reduce the Curie temperature and their dielectric constant peak values, and improve the thermal stabilities of their dielectric properties. Both the dielectric constant and dielectric loss of the BSCT ceramics were reduced by doping Cr ions when the dopant concentration was lower than 1.5mol%. 1.0mol% Cr-doped BSCT specimens are expected to be the candidate materials for microwave tunable devices, whose tunability, dielectric constant and loss were 16.1%, 2700 and 0.24% respectively.