bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ba substituted Pb(ZrxTi1-x)O3 thin films grown by MOCVD
Authors: Puchalla Jochen , Hoffmann-Eifert Susanne , Cattaneo Lorena , Carella Sergio , Waser Rainer 
Published: April 2011

AbstractHigh quality Pb(Zr,Ti)O3 [PZT] and (Pb1-xBax)(ZryTi1-y)O3 (x ≤ 0.15, 0.25 ≤ y ≤ 0.50) [PBZT] thin films were grown on Pt (111) and Ir (111) coated silicon substrates by means of a pulsed liquid injection metal organic chemical vapor deposition (MOCVD) technique. The precursor solutions of Pb(DPM)2, Ba(DPM)2, Zr(IBPM)4, and Ti(OiPr)2(DPM)2 dissolved in butylacetate were separately injected into an AIX-200 reactor using a TriJet™ vaporizer. Stoichiometric films (0.98 ≤ A/B ≤ 1.06) with thickness between 80 nm and 150 nm were deposited at a susceptor temperature of 615 °C to 660 °C. Pure PZT films grown on platinum coated substrates show a randomly oriented perovskite structure accompanied with formation of a PbPtx alloy at the PZT/Pt interface. On the Ir(111) coated substrates the pure PZT films also exhibit a random orientation possibly due to oxidation of the Ir surface layer during the deposition process. Ferroelectric properties of Pr = 35 µC/cm2 and Ec = 90 kV/cm were obtained for a PZT (30/70) film of 150 nm thickness grown on Ir/Si. In contrast, PBZT films with a Ba content of about 5 to 15% show lower tendency for formation of a PbPtx interfacial layer, and a preferred (111) texture was observed for PBZT films grown on the Ir (111) substrates under optimized process conditions. Tetragonal and rhombohedral PBZT films with 15% Ba and a Zr-content of about 0.35 and 0.50, respectively, show an orientation dependence of the ferroelectric properties in the way that Ec is highest for <111> textured films in comparison to Ec determined for <110> textured films. The remanent polarization of 85 nm thick tetragonal PBZT films changes from 17 µC/cm2 for <111> orientation to 13.5 µC/cm2 for <110> texture. The relative permittivity changes in the same way from 600 to 540, respectively. The rhombohedral films exhibit a nearly independent Pr value of about 11 µC/cm2 while the switching field changes from 75 kV/cm for an <111> textured film to 46 kV/cm for an (110) textured one. The relative permittivity values of both films are 890 and 715 for the (110) and the (111) textured films, respectively. The trends observed for the textured PBZT films grown on Si substrates reflect the behaviour reported for epitaxial films [2]
Optical, Electrical and Lifetime Characterization of In-Grown Stacking Faults in 4H-SiC
Authors: Caldwell Joshua David , Klein Paul B , Glembocki Orest J , Stahlbush Robert E , Liu Kendrick X , Hobart Karl D , Kub Fritz 
Published: April 2011

AbstractHere we present optical beam induced current, electroluminescence, time resolved photoluminescence and current-voltage measurements on several 4H-SiC PiN diodes containing in-grown stacking faults (IGSFs). These defects were observed to act as either current shorts, creating a direct electrical contact between the p+ and n+ layers, or as a current barrier. Carrier lifetime measurements verify that the change in behavior is indeed associated with changes in the conductivity of the material in the vicinity of the defect and not due to local changes in the carrier lifetime. The IGSFs discussed here appear to differ from those previously discussed in the literature and may constitute a new, multi-layered IGSF.
Deep Levels in 4H Silicon Carbide Epilayers Induced by Neutron-Irradiation up to 1016 n/cm2
Authors: Cavallini Anna , Castaldini Antonio , Nava Filippo , Errani Paolo , Cindro Vladimir 
Published: April 2011

AbstractWe investigated the electronic levels of defects introduced in 4H-SiC &#945;-particle detectors by irradiation with 1 MeV neutrons up to a fluence equal to 8x1015 n/cm2. As well, we investigated their effect on the detector radiation hardness. This study was carried out by deep level transient spectroscopy (DLTS) and photo-induced current transient spectroscopy (PICTS). As the irradiation level approaches fluences in the order of 1015 n/cm2, the material behaves as highly resistive due to a very great compensation effect but the diodes are still able to detect with a acceptably good charge collection efficiency (CCE) equal to 80%. By further increasing fluence, CCE decreases reaching the value of &#8776; 20% at fluence of 8x1015 n/cm2.The dominant peaks in the PICTS spectra occur in the temperature range [400, 700] K. Enthalpy, capture cross-section and order of magnitude of the density of such deep levels were calculated. In the above said temperature range the deep levels associated to the radiation induced defects play the key role in the degradation of the CCE. Two deep levels at Et = 1.18 eV and Et = 1.50 eV are likely to be responsible of such dramatic decrease of the charge collection efficiency. These levels were reasonably associated to an elementary defect involving a carbon vacancy and to a defect complex involving a carbon and a silicon vacancy, respectively.
Surface morphology and structure of hydrogen etched 3C-SiC(001) on Si(001)
Authors: Coletti Camilla , Hetzel Martin , Virojanadara Chariya , Starke Ulrich , Saddow Stephen E. 
Published: April 2011

AbstractThe surface of 3C-SiC(001) single-crystal epilayers grown on Si(001) substrates is well known to be inhomogeneous and defective. Therefore, the control and understanding at the atomic scale of 3C-SiC surfaces is a key issue. We study the effect of hydrogen etching at different temperatures on the morphology of 3C-SiC(001) surfaces by using Nomarksi optical microscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). As-grown 3C-SiC(001) samples have been hydrogen etched in a horizontal hot-wall chemical vapor deposition (CVD) reactor at atmospheric pressure for different times and temperatures. Flat, high-quality surfaces presenting defined atomic terraces were observed within the 3C-SiC grain boundaries after etching at 1200°C for 30 minutes. Higher etching temperatures resulted in surfaces with step bunching and enlarged surface defects. Samples etched under the best conditions have been studied using low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES).
Homoepitaxial growth on 4H-SiC Substrates by Chemical Vapor Deposition
Authors: Hallin Christer , Khlebnikov Igor , Khlebnikov Yuri , Muzykov Peter , Berkman Elif , Sharma Monica , Stratiy George , Silan Murat , Basceri Cem , Balkas Cengiz 
Published: April 2011

AbstractLow dislocation density and even micropipe free substrates open up a great opportunity to produce high quality epitaxial layers. The epi-layer will become more sensitive to the epitaxial process itself and less dependent on varying substrate quality. Results presented here indicate a strong dependence of the epitaxial layers' growth mode and surface roughness on the substrates' dislocations and domain structure. Thick epitaxial layers grown on near on-axis wafers, both C-face and Si-face, show very similar growth behaviors as for physical vapor transport (PVT) grown crystals. The mix between step-flow and dislocation driven growth on near on-axis C-face chemical vapor deposition (CVD) grown epi-layers (30 μm thick) is resulting in a as smooth, and measured surface roughness is as low, as for growth on 8o off-axis substrates.Surface roughness, Ra, measured on a 50 μm thick epitaxial layer, grown on a low EPD (1E+4 cm-2) 8o off-axis micropipe free substrate, was as low as 1.0 nm (2.98x2.32 mm area).
Nanopatterning of Si/SiGe Two-dimensional Hole Gases by PFOTS-aided AFM Lithography of Carrier Supply Layer
Authors: Yao Kun , Sturm James C 
Published: April 2011

AbstractThe nanopatterning of Si/SiGe layers by PFOTS (perfluorooctyl trichlorosilane) -aided AFM (atomic force microscopy) lithography is demonstrated. We use self-assembled PFOTS monolayers as a resist for AFM exposure and then transfer patterns in to underlying SiGe layers by a two-step selective wet etching. Linewidths well under 100nm can be achieved with improved uniformity and repeatability compared to AFM lithography without PFOTS. This lithography technique was used to pattern the carrier supply layer in Si/SiGe 2-D hole gases to localize holes for epitaxially passivated quantum dot applications.
Thermoplastic Acrylic Lacquer as a Base for Hot Embossing
Authors: Leech P. W. , Lee Robert A. 
Published: April 2011

AbstractWe report the novel use of thermoplastic acrylic lacquer (automotive paint) in the hot embossing of nanoscale structures. Replicas of grating arrays have been produced in coatings of acrylic lacquer using a standard embossing process. The master dies for the experiments comprised grating arrays fabricated by electron beam lithography. Grating patterns with a pitch of 0.7-1.3 μm were configured to produce diffractive images over an area of ~25 × 25 mm. The embossing experiments used a replicated Ni shim as a die and were performed at 100-150 °C and 80 kN force. A temperature above the reflow range for the lacquer, T = 120-150° C, was required in order to achieve a uniform impression across the embossed area of ~80 × 80 mm. The diffractive grating patterns which were embossed into acrylic lacquer have shown optical effects suitable as a security feature including image switching and color movement.
A Novel Design Toward Understanding and Characterizing Transport Behavior of Composite Mesoporous Silica Thin Films
Authors: Chen Zhu , Adams David P , Vasile Michael J , Liu Nanguo , Jiang Yingbing , Xomeritakes George , Brinker C. Jeffrey 
Published: April 2011

AbstractResearch in synthetic materials with controlled transport properties has been inspired by the exquisite selectivity exhibited by natural transmembrane proteins such as ion channels (for selectively transporting ions like sodium and potassium, etc) and aquaporins (for conducting high fluxes of water and excluding ions). In this poster we focus on the transport behavior of highly ordered mesoporous silica thin films synthesized by evaporation induced silica/surfactant self-assembly (EISA). This process allows us to integrate the nanostructures into electronic and fluidic systems by simple coating or spraying procedures, facilitating the characterization of their transport behaviors. Also, the nanocomposite architecture made by this process gives precisely defined pore size, orientation and surface chemistry, allowing tailoring of the motion of molecules and ions transported across the nanochannels. To approach our final goal of understanding and characterizing the transport behavior of our materials, we designed our experiments into three steps: first, we employed focused ion beam (FIB) lithography to drill a single sub-100-nm pore on a substrate support, providing a platform enabling the characterization of trans-membrane behavior of ions/molecules. Second, we developed two EISA approaches to form cubic thin film silica mesophases spanning the FIB-drilled pore. In one approach, we adapted our aerosol-assisted EISA where fusion of liquid crystalline aerosol droplets creates a thin membrane spanning the substrate pore. In the other approach, we modified our synthetic protocol to form ultra thin (20-nm) spanning films by spin-coating. Films with pore sizes ranging from 2nm to 7nm and surface chemistries including –OH, -COOH and –NH2 terminated pore surfaces were prepared in this fashion and integrated to the FIB-drilled single pore substrate support with uniformity to allow tailoring of the motion of ions and molecules. Third, we designed an electrochemical cell in which the FIB-drilled substrates are integrated to enable the measurements of ion fluxes using standard “patch-clamp” instruments. Experiments are conducted to demonstrate the transport characteristics of our materials by measuring transmembrane ion fluxes when specific molecules such as DNA are applied, a method relevant to low cost DNA sequencing. Also, by chemically or physically blocking all but one or several membrane pores, we are attempting to measure ion and water transport in individual synthetic nanopores and compare results with natural ion and water channels.
Control over Pore Positions in Anodised Aluminium Oxide Films via Scratching the Surface of Pure Aluminium
Authors: LeClere Darren , Derby Brian , Thompson George E. 
Published: April 2011

AbstractAnodised aluminium oxide films have several applications in nanotechnology due to the ability to control the dimensions and ordering of the pores. Several techniques have been developed which allow for accurate control over the ordering of pore arrays. Examples of such techniques are the “Two-Step” method, and embossing with optical gratings or micro-machined Si templates. It will be demonstrated that it is possible to control the position of the pores using a nanoindenting device that has scratched the aluminium surface before anodising. The interpore distances accomplished via this technique were 200nm and 400nm by anodising in 0.3M (COOH)2 at 80V and 0.1M H3PO4 at 160V respectively. Hexagonal and square arrays were created by scratching the aluminium with a series of crosshatched lines.
Spatially Resolved MicroDiffraction Analysis of the Plastic Deformation in the Shock Recovered Al Single Crystaltal
Authors: Barabash Rozaliya , Ice G. E. , Liu W. , Belak J. , Kumar M. 
Published: April 2011

AbstractA spatially resolved diffraction method with a sub micrometer-diameter beam and 3D differential aperture technique together with MD simulations, SEM and OIM analysis are applied to understand the arrangements of voids, geometrically necessary dislocations and strain gradient distribution in samples of Al (123) single crystal shocked to incipient spallation fracture. We describe how geometrically necessary dislocations and effective strain gradient alter white beam Laue patterns of the shocked materials. We show how to quantitatively determine the orientation and density of geometrically necessary dislocations in the shock recovered Al samples being initially oriented for single slip.
Local Electron Beam Induced Reduction and Crystallization in Electrochemically Deposited Amorphous TiO2 Films
Authors: Kern Philippe , Michler Johann 
Published: April 2011

ABSTRACTContrary to crystalline titanium oxide (TiO2), electrochemically deposited amorphous thin TiO2 films are found significantly more sensitive towards electron beam (e-beam) exposure. E-beam irradiation experiments were performed under scanning electron microscope conditions at 20 keV with well controlled beam current (IP), current density and exposure dose. As shown by atomic force microscopy and Micro-Raman spectroscopy, even moderate e-beam exposure immediately leads to oxide reduction due to electron stimulated oxygen desorption, while exposure with IP>1 micro-A and J>1 A/cm2 triggers localized crystallization into anatase phase already after seconds of irradiation. The mechanisms for oxide reduction and beam heating induced crystallization are discussed, and a temperature estimation in the beam center indicates that crystallization occurs at less than 150 °C. The well-defined volume loss upon oxygen desorption is shown to be attractive for precise topographical surface patterning, while the triggering local structural changes within a semi-conductive amorphous matrix opens interesting possibilities for tailoring of its local electrical or catalytic properties.
Epitaxial Growth and Luminescence Characterization of Si-based Double Heterostructures Light-emitting Diodes with Iron Disilicide Active Region
Authors: Suemasu Takashi , Li Cheng , Sunohara Tsuyoshi , Ugajin Yuta , Kobayashi Ken'ichi , Murase Shigemitsu , Hasegawa Fumio 
Published: April 2011

ABSTRACTWe have epitaxially grown Si/β-FeSi2/Si (SFS) structures with β-FeSi2 particles or β-FeSi2 continuous films on Si substrates by molecular beam epitaxy (MBE), and observed 1.6 μm electroluminescence (EL) at room temperature (RT). The EL intensity increases with increasing the number of β-FeSi2 layers. The origin of the luminescence was discussed using time-resolved photoluminescence (PL) measurements. It was found that the luminescence originated from two sources, one with a short decay time (τ∼10 ns) and the other with a long decay time (τ∼100 ns). The short decay time was due to carrier recombination in β-FeSi2, whereas the long decay time was due probably to a defect-related D1 line in Si.
Piezoresistance in Strained Silicon and Strained Silicon Germanium
Authors: Richter Jacob , Arnoldus M. B. , Hansen J. Lundsgaard , Larsen A. Nylandsted , Hansen O. , Thomsen E. V. 
Published: April 2011

ABSTRACTThis paper presents experimental results of the piezoresistance in p-type tensile strained silicon and compressive strained silicon germanium grown by molecular beam epitaxy (MBE) on (001) silicon substrates. The piezoresistance decreases in a tensile strained layer and increases in a compressive strained layer when compared to the unstrained material. The results show that one can tune the piezoresistance by tuning the strain in the piezoresistor and thus tailor the performance of the device. The obtained results show an increase in the piezoresistance effect of 35% in compressive strained silicon germanium and a decrease in the piezoresistance effect in tensile strained silicon of 24%. Furthermore, the results show that the piezoresistance of a tensile strained silicon crystal has a smaller temperature dependency compared to that of unstrained silicon. The piezoresistance effect decreases by 7% in tensile strained silicon compared to the piezoresistance effect decrease in silicon of 18% when changing the temperature from 30°C to 80°C.
SOI-Based Silicon Quantum Dots Contacted by Self-Aligned Nano-Electrodes
Authors: Wolf Conrad R. , Ladenburger Andreas , Enchelmaier Rainer , Thonke Klaus , Sauer Rolf 
Published: April 2011

ABSTRACTIn this paper we present a novel approach to fabricate single-electron devices utilizing different self-organization and self-alignment effects. Silicon quantum dots (QDs) are obtained employing reactive ion etching (RIE) into a silicon-on-insulator (SOI) substrate with a self-assembled etch mask. Electrodes with nanometer separation are fabricated and aligned to the QDs by means of a controlled electromigration process. The tunneling rates of the devices are defined by the native oxide covering the silicon QDs and can be adjusted by self-limiting thermal oxidation. The devices show clear Coulomb blockade behavior as well as Coulomb staircase features. In some samples also a gate influence is present giving rise to Coulomb diamonds in the differential conductance diagram.
Growth of Gallium Nitride Nanowires and Nanospirals
Authors: Koley Goutam , Cai Zhihua 
Published: April 2011

ABSTRACTGaN nanostructure synthesis was done in a quartz tube furnace using ammonia and liquid Ga as precursors, and hydrogen as the carrier gas. Ni nanoparticles formed due to annealing, has been used as the catalyst layer, facilitating vapor-liquid-solid growth of the nanostructures. The growth process resulted in the formation of two types of structures, straight nanowires, and irregular growth sometimes resulting in nanospirals. Growth using uniform distribution of catalyst over the entire surface resulted in growth of straight nanowires, while growth performed on catalyst patterned surface resulted in growth of nanospirals. The diameter of the nanowires varied from 20 – 100 nm, while for spirals the cross-sectional diameters were found to be in the range of 100 nm – 1 micron, and spiral diameters in the range of several microns. Using the present growth system and gas flow set-up, it was possible to synthesize ultra-long nanowires and spirals, with overall lengths exceeding 70 microns. The regular straight nanowires were found to have a smooth circular cross-section, while the irregular wires and nanospirals were found to have a very rough surface with approximate hexagonal or triangular cross-sections. Some of the spirals changed into straight nanowires with uniform triangular cross-sections. While more investigations are required to fully establish their structures, based on preliminary characterization and past studies, we conclude that the nanowires with circular cross-sections grow along the c-direction [0001], while the spirals and consequent triangular cross-section nanowires grow along one of the non-polar directions. The formation of spirals themselves may be related to the polarization properties of GaN, similar to those predicted for ZnO nanosprings and nanoribbons.
Improved Stability of Solid State Light Emitting Electrochemical Cells Consisting of Ruthenium and Iridium Complexes
Authors: Bolink Henk Jan , Cappelli Luca , Coronado Eugenio , Costa Rubén D. , Graetzel Michael , Nazeeruddin MdK , Viruela Pedro M , Ortí Enrique 
Published: April 2011

ABSTRACTTwo charged organometallic complexes containing bulky hydrophobic ligands based on ruthenium (II) and iridium (III) were synthesized and their performance in solid state light emitting electrochemical cells is described. The complexes were chosen as due to their large ligands a diminished susceptibility towards the formation of destructive complexes during device operation is expected. The LEC device performances reveal the longest living devices reported so far under dc bias. Quantum chemical calculations confirm that the major effect of the bulky diphenylphenanthroline ligands is of steric origin and not related with changes in the molecular electronic structure of the complexes.
Waveguiding, Microcavity Effects and Optically Pumped Lasing in Single Melt Processed Polyfluorene Nanowires
Authors: O'Carroll Deirdre , Redmond Gareth 
Published: April 2011

ABSTRACTThe synthesis of poly(9,9-dioctylfluorene) conjugated polymer nanowires using the method of melt-assisted wetting of nanoporous alumina membrane templates is reported. Polymer nanowires exhibiting blue photoluminescence emission with diameters of approx. 300 nm are obtained. Absorption and photoluminescence spectra of nanowire mats indicate that the nanowires consist of the semi-crystalline form of the polymer. Single wires exhibit active waveguide behavior whereby excited luminescence propagates towards and out-couples at the tips of the nanowires. Spectra of out-coupled emission exhibit multiple modes with mode spacing corresponding to longitudinal Fabry-Pérot cavities of equivalent lengths to those of the nanowires. Above a threshold incident pump energy spectral collapse to a single blue shifted peak with instrument limited line width occurs characteristic of single mode lasing.