bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two Step Process for the Growth of a Thin Layer of Silicon Dioxide for Tunneling Effect Applications
Authors: Águas Hugo , Cabrita Ana , Tonello Pedro , Nunes Patricia , Fortunato Elvira , Martins Rodrigo 
Published: April 2011

ABSTRACTIn today's main crystalline silicon (c-Si) applications in MOS (metal-oxide-silicon), MIS (metalinsulator-semiconductor) or SIS (Semiconductor-Insulator-Semiconductor), the growing of the oxide layer plays the main role, dictating the device performances, in particular if it has to be grown by a low temperature process. Of fundamental importance is the SiO2 interface with the c-Si. A very low defect density interface is desirable so that the number of trapping states can be reduced and the devices performance optimised.A two step low temperature oxidation process is proposed. The process consists of growing first a layer of oxide by a wet process and then treating the grown oxide with an oxygen plasma. The oxygen ions from the plasma bombard the oxide causing compaction of the oxide and a decrease in the interface roughness and defect density.Infrared spectroscopy and spectroscopic ellipsometry measurements were performed on the samples to determine the oxide thickness, optical and structural properties. SIS structures were built and capacitance measurements were performed under dark and illuminated conditions from which were inferred the interface defect density and correlated with the oxide growth process.
SiC and GaN High-Voltage Power Devices
Authors: Chow T.P. 
Published: April 2011

ABSTRACTThe present status of development of SiC and GaN devices for high-voltage power electronics applications is reviewed. Device structures that are particularly applicable to these two wide bandgap semiconductors are considered and compared to those commonly used in silicon. The simulated and experimental performance of two-terminal rectifiers and three- terminal transistors and thyristors are compared. The effects of material parameters (mobility, ionization coefficients, lifetimes) and defects on device characteristics are pointed out. Similarities and differences between electronic and photonic device development in these semiconductors are discussed.
Polarization induced 2DEG in MBE grown AlGaN/GaN HFETs: On the origin, DC and RF characterization
Authors: Vetury R. , Smorchkova I.P. , Elsass C.R. , Heying B. , Keller S. , Mishra U.K. 
Published: April 2011

ABSTRACTThe contribution of spontaneous and piezoelectric polarization to the formation of a 2DEG in AlGaN/GaN heterostructures was investigated using undoped AlGaN/GaN structures. Hall measurements of 2DEG density on such structures with varying Al percentage (8%-27%) and varying thickness of the AlGaN layer (30-500Å) indicated that donor-like surface states at an energy of 1.42eV below the conduction band were the source of electrons in the 2DEG. Field effect transistors were fabricated on such undoped heterostructures. For an AlGaN/GaN structure with 0.27 Al mole fraction, power density in excess of 3.5 W/mm at 6 GHz with corresponding maximum PAE of 33.5% was obtained. These results exceed the best reported power performance of MBE grown GaN HFETs on sapphire, thus demonstrating the excellent capability of MBE grown GaN heterostructures for microwave power applications.
Plasma-Induced Damage and Passivation of GaN in Electron Cyclotron Resonance Excited N2 Plasma Source
Authors: Hsieh J. T. , Breitschädel O. , Rittner M. , Fu L. W. , Schweizer H. 
Published: April 2011

ABSTRACTElectron cyclotron resonance (ECR) excited N2 plasma exposure were performed to explore a possibility of a robust surface passivation on Ar+ ion beam etched GaN. We adopted Taguchi orthogonal design to optimize the ECR operating parameters with respect to reverse breakdown voltage (VB) and then used the results to determine the VB dependence on the parameters close to the optimum operating point. Rather consistent results were obtained by Taguchi and normal experimental methods. It is clearly indicated that the radio frequency (rf) chuck power play the most important role on the plasma passivation. After N2 plasma treatment, the diode reverse breakdown voltage is drastically restored from 15V to 95V. With the aid of N2 plasma exposure, the Schottky characteristics of ion beam etched GaN can be thus effectively improved.
Surface Disordering and Nitrogen Loss in GaN under Ion Bombardment
Authors: Kucheyev S.O. , Williams J.S. , Jagadish C. , Zou J. , Toth M. , Phillips M.R. , Tan H.H. , Li G. , Pearton S.J. 
Published: April 2011

ABSTRACTThe damage build-up and amorphization behavior in wurtzite GaN films under a wide range of implant conditions are studied by Rutherford backscattering / channeling spectrometry, transmission electron microscopy, and cathodoluminescence spectroscopy. A strong surface peak of lattice disorder, in addition to the expected damage peak in the region of the maximum of nuclear energy loss, has been observed for all implant conditions of this study. Capping of GaN with SiOx and SixNy layers prior to implantation does not eliminate surface disordering. This may suggest that nitrogen loss is not the main reason for the observed enhanced surface disorder, but, rather, the GaN surface acts as a strong sink for migrating point defects. However, pronounced loss of N during ion bombardment is observed for high dose implantation when the near-surface region is amorphized. Moreover, after amorphization, annealing at temperatures above about 400°C leads to complete decomposition of the near-surface layer.
Hydrostatic and Biaxial Strain in BaxSr1-xTiO3Films Grown by Pulsed Laser Deposition
Authors: Carlson C. M. , Parilla P. A. , Rivkin T. V. , Perkins J. D. , Ginley D. S. 
Published: April 2011

AbstractWe grew BaxSr1−xTiO3(BST) films on MgO single crystal substrates by pulsed laser deposition (PLD). We report the in-plane (a) and out-of-plane (c) lattice parameters of BST films deposited in a range of O2deposition pressures [P(02)], as measured by asymmetric rocking curve diffraction. As P(O2) increases, the films' biaxial strain changes from compression (a<c), to cubic (a=c), and then to tension (a>c). Furthermore, bothaandcare larger than the lattice constant for bulk BST of the same composition. This indicates the presence of a hydrostatic strain component in addition to the biaxial component. From the measured lattice parameters, we calculate the total residual strain in terms of biaxial and hydrostatic components. We also examine the effects of a post-deposition anneal. Characterizing residual strain and understanding its origin(s) are important since strain affects the dielectric properties of BST films and thereby the properties of devices which incorporate them.
Room Temperature Growth of Indium Tin Oxide Films by Ultraviolet-Assisted Pulsed Laser Deposition
Authors: Craciun V. , Craciun D. , Chen Z. , Hwang J. , Singh R.K. 
Published: April 2011

AbstractThe characteristics of indium tin oxide (ITO) films grown at room temperature on (100) Si and Corning glass substrates by an in situ ultraviolet-assisted pulsed laser deposition (UVPLD) technique have been investigated. The most important parameter, which influenced the optical and electrical properties of the grown films, was the oxygen pressure. For oxygen pressure below 1 mtorr, films were metallic, with very low optical transmittance and rather high resistivity values. The resistivity value decreased when using higher oxygen pressures while the optical transmittance increased. The optimum oxygen pressure was found to be around 10 mtorr. For higher oxygen pressures, the optical transmittance was better but a rapid degradation of the electrical conductivity was noticed. X-ray photoelectron spectroscopy investigations showed that ITO films grown at 10 mtorr oxygen are fully oxidized. All of the grown films were amorphous regardless of the oxygen pressure used.
Electrical Characteristics of LSMCD-Derived SrBi2.4Ta2O9 Thin Films Using TiO2 Buffer Layer for Metal/Ferroelectric/Insulator/Semiconductor Field Effect Transistor Devices
Authors: Park Joo Dong , Oh Tae Sung 
Published: April 2011

AbstractPt/SBT/TiO2/Si structure was proposed for metal/ferroelectric/insulator/semiconductor field effect transistor (MFIS-FET) applications. SrBi2.4 Ta2O9 (SBT) thin films of 400 nm thickness were prepared using liquid source misted chemical deposition (LSMCD) on Si(100) substrates with TiO2 buffer layers deposited by DC reactive sputtering with the thickness ranging from 5 nm to 200 nm and electrical properties of MFIS structures were investigated. Memory window and maximum capacitance of the Pt/SBT/TiO2 /Si structure increased with decreasing the thickness of TiO2 buffer layer. The Pt/SBT(400 nm)/TiO2(10 nm)/Si structure exhibited C-V hysteresis loop with the memory window of 1.6 V at ±5 V, and could be applicable for MFISFET applications.
Commercial Applications and Review for Direct Write Technologies
Authors: Church Kenneth H. , Fore Charlotte , Feeley Terry 
Published: April 2011

ABSTRACTDirect write in the past has generated the excitement of possibly replacing photoresist for all electronic applications. Removing the mask would substantially reduce the number of steps required to produce electronic circuits. A reduction in steps represented time and dollar savings. The advantage of being able to direct write a manufacturable device would also save time and money in the design process as well. With all of the obvious advantages, it seemed inevitable that research dollars would continue to mount and thus overcome the obstacles preventing this technology from becoming more than a novel technique used in laboratories. As Moore's law began to settle in, so did photoresist and direct write was little more than a novelty.That was then, and this is now. Developers have come to terms with the true value direct write can supply to the manufacturers and design engineers. Techniques such as Focused Ion Beam (FIB), Laser Chemical Vapor Deposition (LCVD), ink jetting and ink penning have found real applications that are making a difference in industry. A summary will be presented describing the various direct write techniques, their current applications and the possible or probable applications.
Initial Stages of Sintering of TiO2 Nanoparticles: Variable-Charge Molecular Dynamics Simulations
Authors: Ogata Shuji , Iyetomi Hiroshi , Tsuruta Kenji , Shimojo Fuyuki , Nakano Aiichiro , Vashishta Priya , Kalia Rajiv K. , Loong Chun-K. 
Published: April 2011

ABSTRACTVariable-charge molecular dynamics simulation of 32 TiO2-nanoparticles with diameter 60Å is performed for 40 ps at 1 GPa and 1,400 K for both rutile and anatase phases, to investigate their phase-dependent sintering mechanisms. In the rutile case, the nanoparticles rotate around their centers during the first 20 ps. Varying degrees of neck formation between neighboring rutile-nanoparticles are found at ∼ 40 ps. In the anatase case, the nanoparticles maintain their original orientations. Similar degrees of neck formation are observed at contacting regions of the anatase nanoparticles.
Intra-Monolayer Hydrogen-Bonding in Monolayer Protected Gold Clusters
Authors: Boal Andrew K. , Rotello Vincent M. 
Published: April 2011

AbstractUnlike the highly ordered Self-Assembled Monolayers (SAMs) formed on flat gold surfaces, those on gold nanoparticles radiate from a roughly spherical center and are amorphous in structure. One result of this structural motif is that the strength of intra- monolayer non-covalent interactions, such as Φ-stacking and hydrogen bonding, are a function of the distance of the recognition element from the colloidal core. We present here an exploration of these phenomena in amide functionalized thiols in MPCs where the amide functionality position was varied in the alkane chain. [1]
A ‘Building Block’ Approach To Mixed-Colloid Systems Through Electrostatic Self-Organization
Authors: Galow Trent H. , Boal Andrew K. , Rotello Vincent M. 
Published: April 2011

AbstractWe have developed a ‘building block’ approach to electrostatically-mediated construction of modular self-assembled colloid-colloid ensembles. Our strategy involves functionalization of one type of colloidal building block with a primary amine, and a counterpart building block with a carboxylic acid derivative (Scheme 1). By combining the two systems, acid-base chemistry followed by immediate charge-pairing resulted in the spontaneous formation of electrostatically-bound mixed-colloid constructs. The shape and size of these ensembles was controlled via variation of particle size for the two components and their stoichiometries.
Temperature dependences of channel mobility and threshold voltage in 4H- and 6H-SiC MOSFETs
Authors: Harada S. , Kosugi R. , Senzaki J. , Suzuki S. , Cho W. J. , Fukuda K. , Arai K. 
Published: April 2011

ABSTRACTWe have investigated the effect of polytype and oxidation condition on the temperature dependence of channel mobility and threshold voltage in 4H- and 6H-SiC MOSFETs. The behaviors of the channel mobility are apparently different for 4H- and 6H-SiC MOSFETs. In contrast to the polytype effect, dry and wet oxidation samples have almost similar channel mobilities. The variation of the threshold voltage with temperature is proportional to the number of the interface states near the conduction band extracted from n-type MOS capacitors. Therefore, we argue that the distribution of the interface states near the conduction band in p-type SiC MOS structure can be represented by that in n-type SiC MOS structure. Although the oxidation condition varies the distribution of the interface states in the energy range between 0.2 and 0.4 eV from the conduction band, it has little influence on the channel mobility.
Difference in Secondary Defects between High Energy B+ and Al+ implanted 4H-SiC
Authors: Ohno Toshiyuki , Kobayashi Naoto 
Published: April 2011

ABSTRACTThe differences of secondary defects between B+ and Al+ implanted layers in high-energy implantation were investigated. At the same volume concentration of implanted ion, density of secondary defects in Al+ implanted layer is higher than that in B+ implanted layer. On the contrary, mean defect size in B+ implanted layer is larger than that in Al+ implanted layer. The structure of secondary defect is thought to be a dislocation loop formed by an extra Si-C layer or localized lattice strain correlated to agglomerated interstitials. The amount of interstitials used for secondary defect formation is estimated. It almost coincides the same amount of implanted ions, and this correlation doesn't depend on ion species. B+ and Al+ implanted layers have different activation energy for secondary defect formation. This result means that they have different agglomerating mechanism of interstitials, which cause the differences of defect size and density between them.
IRAS Analysis of the Early Stage of Thermal Oxidation on a SiC Surface
Authors: Jikimoto Tamotsu , Tsuchida Hidekazu , Kamata Isaho , Izumi Kunikazu 
Published: April 2011

ABSTRACTThe structure of thermal oxide film thinner than 2nm on a SiC surface was investigated using in-situ infrared reflection absorption spectroscopy (IRAS). In the case of oxide films on 6H-SiC(0001), the peak frequencies of the TO mode (≈1050 cm−1) of the Si-O-Si stretch vibration shifts toward lower wave number with decreasing oxide thickness in the range of 0.2nm to 2nm and shift toward a higher frequency as the growth temperature rises. The LO mode (≈1250 cm−1) of the Si-O-Si stretch vibration remains almost constant with the increase in oxide thickness from 0.2 nm to 2 nm. These results indicate that there is a considerable difference in the structure near the interface between a thermally grown oxide layer formed on SiC and one formed on Si.
Characterization of SiC grown on Ge modified silicon substrates
Authors: Pezoldt J. , Stauden Th. , Förster Ch. , Masri P. 
Published: April 2011

ABSTRACTSilicon carbide layers were grown by solid source molecular beam epitaxy on silicon (111). Prior to the silicon carbide growth different amounts of germanium were predeposited on the silicon surface. Structural and morphological investigations with reflection high energy electron diffraction, x-ray diffraction, atomic force microscopy and spectroscopic ellipsometry revealed an improvement of the surface and interface properties for Ge coverages around and below 1 ML. The improved structural properties of the heterojunction lead to an amendment of the forward and reverse properties of the SiC/Si heterojunction.
Selective Doping of 4H-SiC by Aluminum/Boron Co-diffusion
Authors: Gao Ying , Soloviev S. I. , Wang X. , Tin C. C. , Sudarshan T. S. 
Published: April 2011

ABSTRACTBased upon graphite mask, selective aluminum/boron doping of SiC by thermal diffusion has been successfully realized in a temperature range of 1800 to 2100°C. Secondary ion mass spectrometry (SIMS) was used to identify the doping profiles, which showed very high aluminum concentration (5×1019 cm−3) near the surface and linearly graded boron profile up to several micrometers in depth. Hall-effect measurement was also employed to obtain the carrier concentration, which showed more than 1019 cm−3 carrier concentration at room temperature. Cathodoluminescence (CL) image clearly illustrated the locally diffused pattern. In addition, planar p-n diodes based upon this technique were fabricated and current-voltage (I-V) characteristics were measured. Excellent rectification property has been obtained. Built-in voltage of 2.9 V in the formed p-n junction was obtained by capacitance-voltage (C-V) measurement.
Deep-level luminescence at 1.0 eV in 6H SiC
Authors: Magnusson B. , Ellison A. , Son N. T. , Janzén E. 
Published: April 2011

ABSTRACTResults from photoluminescence (PL) and Zeeman effect measurements of a PL center, labeled UD-1, in 6H SiC are presented. The spectrum consists of three no phonon-lines (NPLs) at 0.9952, 1.0015 and 1.0020 eV. The luminescence starts decreasing in intensity above 40 K and is completely quenched at 80 K. The observed Zeeman splitting reveals a spin one half of the ground state of the two highest energy lines. No splitting of the 0.9952 eV line is detected. The g║-value for the 1.0015 eV and 1.0020 e║ lines are g║ = 1:4 and g║ = 1:7, respectively. For both lines, g⊥ = 0. The C3v symmetry indicates that the UD-1 center is either a substitutional defect or a complex with its constituents lying along the c-axis of the lattice.
A Novel Direct Pulse Laser Deposited Nickel Silicide Ohmic Contact to n-SiC
Authors: Cole M. W. , Joshi P. C. , Hubbard C. W. , Ngo E. , Demaree J. D. , Hirvonen J. K. , Wood M. C. , Ervin M. H. 
Published: April 2011

ABSTRACTPulsed laser direct deposit Ni2Si Ohmic contacts were successfully fabricated on n-SiC. The electrical, structural, compositional, and surface morphological properties were investigated as a function of heat treatments ranging from 700 °C to 950 °C. The as-deposited and 700 °C annealed samples were non-Ohmic. Annealing at 950 C° yielded excellent Ohmic behavior, an abrupt void free interface, and a smooth surface morphology. No residual carbon was present within the contact film or at the film-SiC interface and the contact showed no appreciable contact expansion as a result of the 950 °C annealing process. Results of this investigation demonstrate that 950 °C annealed pulse laser deposited Ni2Si-SiC contacts possess excellent electrical, interfacial, microstructural, and surface properties, which are required for reliable device operation.
Temperature Dependence of Dislocation Motion and Crack Propagation in a Two-Dimensional Binary Model Quasicrystal
Authors: Krdzalic Galib , Brunelli Marco , Trebin Hans-Rainer 
Published: April 2011

AbstractA twodimensional binary model quasicrystal (Roth-Mikulla tiling) was subjected to shear of constant rate (Lees-Edwards boundary conditions). Lennard-Jones forces were applied between the atoms and the evolution of the system was followed by isothermal molecular dynamics simulations. Temperature was controlled by a Nosé-Hoover thermostat. Dislocation dipoles were created followed by phason walls, which broadened with increasing shear. Widening happens by transversal shear induced diffusion. It starts with the onset of failure and is saturating after reaching two planes of high interface energy parallel to the glide plane. Thus a structurally damaged layer arises along which viscous glide is developing. The transverse diffusion constant follows an Arrhenius law at low temperature. With increasing temperature it is bending to a flatter slope similar as in the model of phason induced diffusion by Kalugin and Katz. First results of temperature-dependent crack-propagation are reported, too.
Bulk Mg-Cu-Y-Al Alloys in the Amorphous, Supercooled Liquid and Crystalline States
Authors: Linderoth S. , Pryds N. , Eldrup M. , Pedersen A.S. , Ohnuma M. , Zhou T.-J. , Gerward L. , Jiang J.Z. , Lathe C. 
Published: April 2011

AbstractBulk Mg-Cu-Y-Al alloys, prepared by casting into a wedge-shaped copper mold, have been studied in the as-prepared, the supercooled liquid, and the crystalline states. In the as-prepared state x-ray diffraction of sub-millimeter sized regions were performed using a focused x-ray beam. The phase composition of the cross section as well as of the surface of the wedge-shaped specimen was investigated as a function of position. The cooling history of the alloy was experimentally determined and compared to results of a control-volume finite-difference modelling study. The experimentally determined and the calculated cooling rates were correlated with the observed amorphous/crystalline structure. The transition from an amorphous to a crystalline state was followed by x-ray diffraction studies as a function of time at specific temperatures in the region between the glass transition and the crystallization temperature. Based on these results a temperature-time-phase diagram was constructed. The dependence of external pressure on the crystallisation temperature was investigated by in situ high-temperature and high- pressure x-ray powder diffraction by using synchrotron radiation. The investigations form the basis for a selection of the optimum temperature in the supercooled liquid region for performing deformation/shaping of the Mg-based alloys.
Glass Forming Ability and Crystallization Behaviors of the Ti-Cu-Ni-(Sn) Alloys with Large Supercooled Liquid Region
Authors: Kim Y.C. , Yi S. , Kim W.T. , Kim D.H. 
Published: April 2011

AbstractThe thermal stability and crystallization behavior of melt spun amorphous Ti50Cu35Ni15-xSnx (x=0, 3, 5, 7) alloys has been studied in by thermal analysis (DSC and DTA) and X-ray diffractometry. Partial replacement of Ni by Sn up to 5 at % in Ti50Cu35Ni15 alloy improved thermal stability and glass forming ability. The onset temperature of the first exotherm increased from 739 to 756 K with increasing Sn content x from 0 to 5, and then decreased to 745 K for the alloy with x=7 due to change in crystallization sequence. Melt spun amorphous Ti50Cu35Ni12Sn3 and Ti50Cu35Ni10Sn5 alloys exhibit ΔTx exceeding 78 and 76 K, respectively, which is significantly larger than ΔTx of 46 K in Ti50Cu35Ni15 alloy. Amorphous Ti50Cu35Ni15 alloy crystallized by precipitation of supersaturated cubic Ti(Ni,Cu) phase followed by decomposition into a mixture of TiCu and TiNi at higher temperature. Amorphous Ti50Cu35Ni15-xSnx (x=3, 5) phase crystallized by precipitation of cubic Ti(Ni,Cu) phase, followed by transformation into a mixture of TiNi, TiCu, Ti3Sn phases. Amorphous Ti50Cu32Ni8Sn7 phase crystallized by co- precipitation of cubic Ti(Ni,Cu) phase and unidentified phase, followed by transformation into a mixture of TiNi, TiCu, Ti3Sn phases.