bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical properties of silicates co-doped with Si and Er3+ ions
Authors: Lebour Y. , Pellegrino P. , Moreno J. A. , Garcia C. , Garrido B. , Morante J.R. , Prassas M. 
Published: April 2011

ABSTRACTWe have characterized the mechanism of energy transfer from Si nanoparticles to Er3+ ions in different silicate glasses, namely soda-lime and aluminium silicates, and made the comparison with pure silica. By means of a multi-implantation scheme we have formed a 350 nm thick glass layer with a uniform Si excess (5% or 15% atomic excess) and an Er distribution. Several Er doses were chosen so that the resulting Er peak concentration could vary from 2 × 1019 up to 6 × 1020 cm−3. Fused silica wafers coimplanted in the same conditions were used as a reference material in order to compare the different efficiency and mechanisms of Er emission as a function of the host silicate composition. Thermal treatment at low temperature has been performed to enhance the photoluminescence around 1540 nm. Large PL emission, compared to structures doped only with Er, has been successfully detected in all co-implanted glasses, with similar intensity. Moreover, we have measured PL lifetimes from 2.5 to 12 ms (depending on the Er dose and Si excess), and estimated an Er effective excitation cross-section of the order of 1 × 10−17 cm2.
Growth and Overgrowth of Ge/Si Quantum Dots: An Observation by Atomic Resolution HAADF-STEM Imaging
Authors: Zhi Dan , Midgley Paul A. , Dunin-Borkowski Rafal E. , Joyce Bruce A. , Pashley Don W. , Bleloch Andrew L. , Goodhew Peter J. 
Published: April 2011

ABSTRACTThe formation of self-assembled quantum dots (QD) is of increasing interest for applications in optical, nanoelectronic, biological and quantum computing systems. From the perspective of fabrication technology, there are great advantages if the whole device can be made using a single Si substrate. Furthermore, GeSi is a model semiconductor system for fundamental studies of growth and material properties. In practice, as the MBE growth of heterostructures is inherently a non-equilibrium process, the formation of self-assembled nanostructures is both complex and sensitive to growth and overgrowth conditions. The morphology, structure and composition of QDs can all change during growth. It is therefore crucial to understand their structures at different stages of growth at the atomic scale. Here, the characterization of QD growth using high-resolution high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) imaging is presented. Both the formation of uncapped QDs and the effect of the encapsulation are investigated, and the morphological and compositional evolution of the QDs and wetting layers are observed directly at the atomic scale for the first time. During encapsulation, the Ge content in the centres of the QD remains unchanged, despite significant intermixing, lateral spreading and a laterally inhomogeneous Ge distribution inside the Ge QD. The initial non-uniform wetting layer for the uncapped Ge QD becomes uniform after encapsulation, and a 3-monolayer-thick core with ∼ 60% Ge content is formed in the 2 nm-thick wetting layer with an average Ge content of ∼ 30%. The results were obtained by direct analysis of the Z-contrast STEM imaging without involving complex image simulations.
Electric Force Microscopy Of Individually Charged Silicon Nanoparticles
Authors: Melin Thierry , Diesinger Heinrich , Barbet Sophie , Deresmes Dominique , Baron Thierry , Stievenard Didier 
Published: April 2011

ABSTRACTWe report on charge injection experiments performed on single silicon nanoparticles and their analysis by Electric Force Microscopy (EFM). An analytical model is presented, enabling a quantitative determination of the charge state of the semiconductor nanoparticles from EFM signals, for arbitrary tip and nanoparticle shapes.Experimentally, we provide an analysis of the capacitive and charge interactions taking place in EFM of silicon nanoparticles deposited on conductive substrates. We demonstrate that the weak image interactions associated with charged nanoparticles -of dipole-dipole type- can be identified from a spectroscopic EFM analysis.Finally, we address the issue of the charge injection mechanisms. From the hysteretic behaviour of the charge injection spectroscopy, we separate volume versus surface charge effects. We show that charges are mostly injected in the nanoparticle volume, with however some residual injection on the nanoparticle surface. Mechanisms of the charge saturation are discussed.
Subcritical CO2Assisted Polymer Surface Engineering at Low Temperatures
Authors: Yang Yong , Lee Ly James 
Published: April 2011

ABSTRACTPolymer-based Micro/Nano Electro Mechanical Systems (MEMS/NEMS) have attracted a great deal of interest from industries and academia. The common polymer processing methods involve either organic solvents or temperatures above the glass transition temperature (Tg), which is undesirable, particularly for biomedical applications. On the basis of different properties near polymer surfaces from those in the bulk, we introduce subcritical fluids (particularly carbon dioxide, CO2) into polymer surfaces to manipulate the polymer properties at the nanoscale so that we can achieve low temperature surface engineering. In this study, polymer surface dynamics under CO2were addressed using atomic force microscopy (AFM) and neutron reflectivity (NR). Monodispersed nanoparticles were deposited onto the smooth polymer surface and then embedded into the surface by annealing the sample at the pre-specified temperatures and CO2pressures. The embedding of nanoparticles in the proximity of the surface was measured using AFM, and thus the surfaceTgprofile could be determined. It was revealed that there is a rubbery layer of up to a hundred nanometers thick at the surface where theTgis lower than that in the bulk and CO2dramatically reduced the surfaceTg. NR studies also show that CO2can enhance chain mobility at the polymer surfaces below the polymer bulkTg. These results indicated that even low concentrated CO2greatly could enhance polymer chain mobility below theTgof the CO2–plasticized polymers. The thickness of the rubbery layer can be controlled by tuning either temperatures, or CO2pressures, or both, which makes it possible to engineer polymer surfaces at low temperatures. Guided by the CO2enhanced polymer surface dynamics, we developed a novel CO2bonding technique to succeed in low temperature bonding of polymers at the micro/nanoscales. This CO2bonding technique has been applied to seal polymeric nanofluidic biochips and construct well-defined three-dimensional (3D) biodegradable polymeric tissue scaffolds.
Real Time Measurement of Functional Groups Substitution on Fluorocarbon Surface by ATR FT-IR
Authors: Sato Yuki , Murahara Masataka 
Published: April 2011

ABSTRACTThe photochemical reaction process steps in substituting the functional groups on the surface of fluorocarbon [FEP] by irradiating an Xe2 excimer lamp on water or formic acid and FEP placed on the attenuated total reflectance [ATR] prism, has been measured in real time. These steps include, water photo-dissociation, the defluorination of the FEP and the hydrophilic group substitution.In case of formic acid, the absorption peaks of the -CHO in the region of 2940 cm−1 and the -COOH in the region of 1710 cm−1 decreased respectively by photo dissociation, but that of the -OH in the region of 3300cm−1 increased. The results indicated that the -CHO and -COOH have turned to -OH.Furthermore, the contact angle with water was measured. When compared to the untreated sample, whose contact angle was 110 degrees, the contact angle of the sample treated with water and the Xe2 lamp irradiation for 25 minutes became 31 degrees, and that of the sample modified with formic acid and the lamp irradiated for 25 minutes further improved to 17 degrees. This implies that the hydrophilic groups were produced more in formic acid than in water.
Fabrication of Surface Nitridation Mask on GaAs Substrate for Nano-Lithography
Authors: Yamamoto Yo , Saito Kohji , Kondo Toshiyuki , Maruyama Takahiro , Naritsuka Shigeya 
Published: April 2011

ABSTRACTThe surface nitridation of GaAs substrate under various conditions were performed and its surface morphology was studied by using atomic force microscope. The RMS roughness of the surfaces was closely related to formation of the particles which was formed by As evaporation and subsequent Ga migration, which was enhanced by higher substrate temperature.
Laser Fabrication and Characterization of Adhesive-Free Joints For Encapsulation of Biomedical Implant Devices
Authors: Newaz G. , Georgiev D. G. , Mian A. , Auner G. , Herfurth H. , Witte R. 
Published: April 2011

ABSTRACTLaser-fabricated joints of sub-millimeter widths between biocompatible, dissimilar materials have the potential for applications as encapsulation of miniature implant biomedical devices. In this work, we briefly describe the laser joining method of a very promising system, polyimide/titanium-coated borosilicate glass, and present and discuss results from characterization of such laser joints by means of mechanical failure (tensile) tests, optical microscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Our results suggest the formation of strong chemical bonds between Ti-containing species and certain polymeric functional groups. Mechanical tensile strength failure test showed that such joint experience only limited, disappearing with time degradation as a result of soaking in physiological solutions.
Fabrication of Novel Types of Colloidosome Microcapsules for Drug Delivery Applications
Authors: Paunov Vesselin N. , Noble Paul F. , Cayre Olivier J. , Alargova Rossitza G. , Velev Orlin D. 
Published: April 2011

ABSTRACTNovel colloidosome microcapsules with aqueous gel cores and shells of different polymeric colloid particles have been prepared and characterized. Our preparation technique involves templating water-in-oil emulsions stabilized by either polymeric microrods or polystyrene (PS) latex particles and subsequent gelling of the aqueous phase with a suitable hydrocolloid. The obtained colloidosome microcapsules were transferred in water after dissolving the oil phase in ethanol and multiple centrifugation/washing cycles with ethanol and water. The presence of an aqueous gel core was found to enhance the structural integrity and mechanical stability of the obtained colloidosomes. In the case of latex particles forming the colloidosome membrane, the effect of the oil type on the final structure of the colloidosome shell was also studied. It was shown that by using appropriate oil, the latex particles within the colloidosome shell can be partially or completely swollen which not only binds them together but also allows direct control over the membrane pore size and its permeability with respect to entrapped species. Such microcapsules can find various applications for development of novel drug and vaccine delivery vehicles, slow release of cosmetic and food supplements.
Electrodeposition Characteristics of Bismuth-Telluride Films
Authors: Prabhakar A. , Podlaha-Murphy E. J. , Murphy M. C. , Devireddy R. V. 
Published: April 2011

ABSTRACTThis work is a part of an on-going research effort to develop an array of micro thermoelectric coolers (TECs) for highly localized control of temperature at the cellular level. Prefabrication experimentation and modeling were carried out to understand the behavior of the proposed device. Mathematical models were used to identify important device parameters and optimal device dimensions. Preliminary experiments have shown that it is feasible to produce the TECs through electrodeposition of bismuth and telluride on modules produced using a modified multistep LIGA (Lithographie, Galvanoformung and Abformung) technique. The development and characterization of the proposed TECs would enable the bioengineer highly localized control of temperature in a native or artificial tissue system. Thus enabling further usage of low temperatures in biological systems for both destructive (cryosurgical) and beneficial (cryopreservation) procedures.
Matrix Assisted Pulsed Laser Evaporation of Poly (D, L) Lactic Acid Films
Authors: Patz Timothy M. , Doraiswamy Anand , Narayan Roger , Menegazzo Nicola , Kranz Christine , Mizaikoff Boris , Modi Rohit , Chrisey Douglas B. 
Published: April 2011

ABSTRACTWe have deposited poly (D, L lactic acid) (PDLLA) thin films using matrix assisted pulsed laser evaporation (MAPLE). FTIR spectroscopy revealed that the PDLLA had similar absorption bands to the dropcast material. X-ray photoelectron spectroscopy has shown that peaks corresponding to C-H, C-O and C=O represented 38.4, 30.1 and 31.4% of the C1s spectrum, respectively. XPS O1s analysis revealed that the O=C and O-C components make up 52 and 48 % of the O1s content. Atomic force microscopy revealed that MAPLE deposition provides smooth, continuous thin biomaterial films. These matrix assisted pulsed laser evaporation-deposited biomaterial thin films may serve to improve the implant/tissue interface.
New biological labels based on functionalized YVO4: Eu nanoparticles
Authors: Giaume D. , Buissette V , Lahlil K. , Gacoin T. , Boilot J.-P. , Casanova D. , Beaurepaire E. , Sauviat M.-P. , Mercuri A. , Alexandrou A. 
Published: April 2011

ABSTRACTLanthanide-ion doped oxide (YVO4: Eu) nanoparticles were synthesized as aqueous colloids and functionalized by a bioactive silane shell to be used as fluorescent biological labels. Nanoparticles functionalized with guanidinium groups were able to act as artificial toxins which specifically target Na+ channels. They were individually detectable in live cardiac myocytes. Functionalized oxide nanoparticles appear as a new interesting tool, especially attractive for long-term single-molecule tracking due to their photo-stability and long luminescence lifetime.
Hydrothermal Synthesis of the Deep-UV NLO Material Sr2Be2B2O7
Authors: Kolis Joseph W. , McMillen Colin D. , Franco Taina 
Published: April 2011

ABSTRACTThe synthesis of non-linear optical (NLO) materials that are transparent into the deep-UV (<200 nm) region is an important component in the development of advanced optical technology. Such materials are sought after for their potential applications in the fields of high resolution photolithography, micro-machining, and laser spectroscopy. Borates are one class of solid-state materials that have received consideration for these applications because of their favorable physical and optical properties. One such compound, Sr2Be2B2O7(SBBO) has been reported to be transparent below 200 nm, and exhibits a large second harmonic generation (SHG) coefficient. Significant difficulties in the flux growth of large, high quality crystals have prevented this material from further development. We have successfully grown large crystals of SBBO by a hydrothermal synthetic method for the first time, and have characterized their physical properties. The synthesis and structure of a new material encountered during the synthesis of SBBO, LiBeSr2B3O8, is also reported here.
Dramatically Enhanced Thermoelectric Properties of Ca3Co4Oy by Large Amount of RE Substitution
Authors: Sugiura Y. , Horii S. , Kumagai T. , Okamoto T. , Otzschi K. , Shimoyama J. , Kishio K. 
Published: April 2011

ABSTRACTWe report the synthesis and thermoelectric properties of [(Ca1-xREx)2CoO3-δ]0.62CoO2 compounds (RE: rare earth element, RE = Y, Sm, Eu, Tb, Dy, Ho and Lu). From optimization of synthesis conditions, all the chosen RE in this study were able to be substituted for the Ca sites in the block layers up to x = 0.25. In the case of RE = Tb, at 1150 K, only κ was systematically decreased with x, while both Seebeck coefficient (S) and resistivity (ρ) were almost constant for the charge of x. Consequently, the dimensionless figure of merit (ZT) was increased with x and reached 0.2 at 1150 K for x = 0.25. Moreover, interestingly, it was found that S and ρ at 300 K were enhanced with ionic radius of the doped trivalent RE ions in spite of the doping of equivalent RE ions. This is probably because local structures of oxygen sites around Co ion in the CoO2 layers largely depend on kinds of the doped RE.
Study Of Electrical, Chemical And Structural Characteristics Of Superconductor Thin Film Obtained By Polymeric Precursors Method
Authors: Carvalho C.L. , Peruzzi R.O. , Junior D.R. 
Published: April 2011

ABSTRACTSuperconductor films of the BSCCO system have been grown by dip coating technique with good success. The chemical method allows us to grow high temperature superconductor thin films to get better control of stoichiometry, large areas and is cheaper than other methods. There is a great technological interest in growth oriented superconductor films due anisotropic characteristics of superconductor materials of high critical temperature, specifically the cuprates, as we know that the orientation may increase the electrical transport properties. Based on this, the polymeric precursor method has been used to obtain thin films of the BSCCO system. In this work we have applied that method together with the deposition technique known as dip coating to obtain Bi-based superconductor thin films, specifically, Bi1.6Pb0.4Sr2.0Ca2.0Cu3.0Ox+δ, also known as 2223 phase with a critical temperature around 110 K. The films with multilayers have been grown on crystalline substrates of LaAlO3 and orientated (100) after being heat treated around 790°C - 820°C in lapse time of 1 hour in a controlled atmosphere. XRD measurements have shown the presence of a crystalline phase 2212 with a critical temperature around 85 K with (001) orientation, as well as a small fraction of 2223 phase. SEM has shown a low uniformity and some cracks that maybe related to the applied heat treatment. WDS has also been used to study the films composition. Different heat treatments have been used with the aim to increase the percentage of 2223 phase. Measurements of resistivity confirmed the presence of at least two crystalline phases, 2212 and 2223, with Tc around 85 K and 110 K, respectively.
Magnetic Properties of a New One-Dimensional Vanadium Oxide with the Hollandite Structure.
Authors: Chernova Natasha A. , Katana Ngala J. , Zavalij Peter Y. , Stanley Whittingham M. 
Published: April 2011

ABSTRACTThe magnetic properties of the first hollandite-type vanadium oxide containing anions in the 2×2 channels, V7.22O8(OH)8(Cl)0.77(H3O)2.34, are studied using static (DC) and dynamic (AC) magnetic susceptibilities. From the high-temperature Curie-Weiss behavior the effective magnetic moment is found consistent with the 3+ vanadium oxidation state; the negative Curie-Weiss temperature Θ ≈ -500 K indicates strong antiferromagnetic exchange. The DC magnetic susceptibility shows a rapid increase and the AC susceptibility shows a maximum at about 20 K, indicating magnetic phase transition. The field-cooled and zero-field-cooled susceptibilities diverge below the transition temperature. The real and imaginary components of the AC susceptibility show frequency dependence and shift of maximum toward lower temperatures with decreasing frequency. Analysis of the frequency dependences reveals at least three different relaxation processes existing around and below the transition temperature. The temperature dependences of their relaxation times were obtained using Cole-Cole analysis. We show that the magnetic behavior observed is well explained by the random-field Ising model, with randomness brought on by vacancies in vanadium sites.
Formation Mechanisms of Perovskite Pb(Ni1/3Nb2/3)O3 in Reaction-sintering Process
Authors: Liou Yi-Cheng , Huang Yi-Chen , Wu Chi-Ting 
Published: April 2011

ABSTRACTFormation mechanisms of perovskite Pb(Ni1/3Nb2/3)O3 (PNN) in the reaction-sintering process were investigated. Only the reflections of raw materials were detected at 400°C. For pellets heated to 500°C, pyrochlore phase Pb2Nb2O7 (P2N2) are found. Cubic Pb3Nb4O13 (P3N4) pyrochlore phase formed and became the main phase in pellets heated to 600°C. After being heated to 800°C, Pb3Nb2O8 (P3N2) pyrochlore phase formed in the pellets. As the pellets were heated to 900°C, the peak of NiNb2O6 columbite phase appeared. In pellets heated to 950°C, the weak peaks of PNN perovskite phase appeared. This means the perovskite phase formed at a temperature between 900°C and 950°C. As the pellets were heated to 1000°C, a large amount of PNN was formed and became dominant. The PbO, NiNb2O6 and Pb3Nb2O8 phases disappeared. The P3N4 content increased with temperature in pellets heated to 1050–1200°C. For pellets heated to 1250°C, the P3N4 content decreased significantly.
Femtosecond laser interactions with Co/Al multilayer films
Authors: Picard Yoosuf N. , Adams David P. , Yalisove Steven M. 
Published: April 2011

ABSTRACTReactive multilayer films of Co and Al were irradiated using femtosecond and nanosecond pulse-length lasers. While no ignition of a self-propagation reaction occurred during the laser machining studies, we observe considerable differences in the morphology and extent of damage induced by femtosecond and nanosecond lasers. Using scanning electron microscopy, we show that single metal layers can be removed at the micron scale with negligible damage to the underlying layers using femtosecond pulse-length lasers.
Laser ablation-based nanofabrication in aqueous solutions
Authors: Kabashin Andrei V. , Meunier Michel 
Published: April 2011

ABSTRACTAn overview of research results related to the femtosecond laser ablation-based method for nanofabri-cation in aqueous solutions is presented. The method makes possible the production of stable biofunctionalized gold nanoparticle colloids with extremely small size (down to 2–2.5 nm) and size dispersion (down to 1–1.5 nm). The colloids are of importance for biosensing applications.
Liquid Crystal Influenced Self-assembly in Mesogenic Polymer and Liquid Crystal Blends
Authors: Li Lanfang , Catanescu Carmen Otilia , Chien Liang-Chy 
Published: April 2011

ABSTRACTIn this work, we found that by performing photo-polymerization of the mesogenic monomer RM257 in liquid crystals, well organized polymer walls were formed through out the cell by self-assembly of the polymer within the anisotropic host – the liquid crystal. The polymerization conditions, which were parameterized as UV intensity, photo-reactivity (characterized by photo initiator concentration), curing temperature, monomer concentration and mesophase of the liquid crystal host, were systematically varied. Different liquid crystal host also raised some difference in polymer network. We believe this kind of morphology comes from spinodal decomposition and the anisotropic elastic property of the liquid crystal host. It is found that for RM257 and low molecular weight nematic liquid crystals a monomer concentration of 5% is sufficient to use liquid crystal hosts to work as templates for well structured polymer walls.
Target Morphologies in Polymer Blends
Authors: Clarke Nigel , Henderson Ian 
Published: April 2011

ABSTRACTWe model a novel process for obtaining controlled morphologies in polymer blends. Particles of one type of polymer are allowed to dissolve in a matrix of a dissimilar polymer. Prior to complete dissolution the blend is quenched into the two phase region, such that phase separation takes place. The combination of the incomplete dissolution and the wavelength selection process associated with phase separation results in particles that during the ‘intermediate’ stages have a core that is significantly rich in the matrix material. The concept is extended to consider the effect of phase separation on an inhomogeneous surface chemically patterned with regions which are more attractive to one component of the blend.