bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variational Calculations of Donor Binding Energy in Rectangular Wurtzite Aluminium Gallium Nitride / Gallium Nitride Quantum Wires
Authors: Praharaj Choudhury Jayant 
Published: April 2011

AbstractWe present variational calculations of donor binding energy in rectangular wurtzite aluminium gallium nitride / gallium nitride quantum wires. We explicitly take into account the effect of spontaneous and piezoelectric polarization on the energy levels of donors in quantum wires. Wurtzite structure nitride semiconductors have spontaneous polarization even in the absence of externally applied electric fields. They also have large piezoelectric polarization when grown as pseudomorphic layers. The magnitude of both polarization components is of the order of 1013 electrons per cm2, and has a non-trivial effect on the potential profile seen by electrons. Due to the large built-in electric fields resulting from the polarization discontinuities at heterojunctions, the binding energies of donors is a strong function of the position inside the quantum wire. The potential profile in the 0001 direction can vary by as much as 1.5eV due to polarization effects for vertical dimensions of the quantum wire up to 20 angstroms. The probability density of electrons tends to concentrate near the minimum of the conduction band profile in the 0001 direction. Donors located close to this minimum tend to have a larger concentration of electron density compared to those located closer to the maximum. As a consequence, the binding energy of the former are higher compared to the latter. We use Lorentzian variational wavefunctions to calculate the binding energy as a function of donor position. The confinement potential enhances the binding by a factor of about 3 compared to donors in bulk nitride semiconductors, from about 30 meV to about 90 meV. The variation of binding energy with position is calculated to be more than 50% for typical compositions of the quantum wire regions. Our calculations will be useful for understanding device applications involving n-type doped nitride semiconductor quantum wires.
A Role of the Built-in Piezoelectric Field in InGaN/AlGaN/GaN Multiple Quantum Wells in the Electroferlectance Experiments
Authors: Bokov Pavel , Avakyants Lev , Badgutdinov Mansur , Chervyakov Anatoly , Shirokov Stanislav , Yunovich Alexander , Vasileva Elena , Snegov Feodor , Bauman Dmitry , Yavich Boris 
Published: April 2011

AbstractThe influence of built in piezoelectric field in the light-emitting diodes based on InGaN/AlGaN/GaN heterostructures on the electroreflectance spectra have been studied. The structures were grown by MOCVD technology and «flip-chip» mounted. Light was emitted or reflected through sapphire substrate. The built in electric field in the structure was modulated by pulses of reverse bias from -6 to +1 V applied to the contacts of diode. Observed blue shift of spectral line from InGaN/GaN multiply quantum wells region with the increasing reverse bias voltage has been explained as the result of lowering of the electric field in the quantum well.
Formation of Aluminum Nitrides by Precipitate-Accommodated Plasma Nitriding
Authors: Aizawa Tatsuhiko , Vissutipitukul Patama 
Published: April 2011

AbstractPrecipitate accommodated nitriding is proposed as a new, non-traditional surface treatment of aluminum alloys. In the case of nitriding the aluminum-copper alloys, Al2Cu plays an important role as a nucleation site to form AlN by the two step reactions of Al2Cu + 2N → 2AlN + Cu and Cu + 2Al → Al2Cu and as a helper to preserve the fast nitrogen diffusion path. In this precipitate accommodation, AlN islands form on Al2Cu in coherent, and, gradually cover the matrix surface by the AlN layer. This Al2Cu accommodation in nucleation reduces the pre-sputtering time and shortens the incubation time prior to formation of AlN layer. Furthermore, the interface between Al2Cu and AlN plays a nitrogen diffusion path across the nitrided layer. This Al2Cu accommodation in growth of AlN accelerates the growth rate of AlN layer in practice. The formation rate of AlN approaches to 7 μm/ks in the present nitriding. This reduction of processing time is much favored for industrial manufacturing of automotive parts and electrical components in practice. Low friction and wear is also attained in dry sliding condition by this AlN-layered specimen: μ = 0.13 and Ws = 1.5 × 10−5 mm3N−1m−1. Since Al2Cu is common precipitate to most of aluminum alloys, this AlN-layer formation is also favored to protective coating for automotive parts and electric components.
DEFECT SELECTIVE ETCHING OF THICK AlN LAYERS GROWN ON 6H-SIC SEEDS – A TRANSMISSION ELECTRON MICROSCOPY STUDY
Authors: Nyakiti Luke Owuor , Chaudhuri Jharna , Kenik Ed A , Lu Peng , Edgar James H 
Published: April 2011

AbstractIn the present study, the type and densities of defects in AlN crystals grown on 6H-SiC seeds by the sublimation-recombination method were assessed. The positions of the defects in AlN were first identified by defect selective etching (DSE) in molten NaOH-KOH at 400 °C for 2 minutes. Etching produced pits of three different sizes: 1.77 ìm, 2.35 ìm , and 2.86 ìm. The etch pits were either aligned together forming a sub-grain boundary or randomly distributed. The smaller etch pits were either isolated or associated with larger etch pits. After preparing cross-sections of the pits by the focused ion beam (FIB) technique, transmission electron microscopy (TEM) was performed to determine which dislocation type (edge, mixed or screw) produced a specific etch pit sizes. Preliminary TEM bright field and dark field study using different zone axes and diffraction vectors indicates an edge dislocation with a Burgers vector 1/3 is associated with the smallest etch pit size.
Delamination of Oil Paints on Acrylic Grounds
Authors: Maor Yonah , Murray Alison 
Published: April 2011

AbstractIn a set of composite samples of oil or alkyd paints, over acrylic grounds, naturally aged for eight years, some of the samples delaminated. Samples were analyzed with X-ray fluorescence (XRF), inductively coupled plasma (ICP), Fourier transform infrared - attenuated total reflectance (FTIR-ATR) and atomic force microscopy (AFM) as well as other techniques not detailed in this paper. Results indicate the main cause of delamination is metal soaps in the oil paint and particularly zinc soaps. The ground is a minor consideration as well, rougher grounds providing better adhesion than smooth ones.
Fabrication of Carbon Nanotube Field-Effect Transistors with Metal and Semiconductor Electrodes
Authors: Sharma Himani , Xiao Zhigang 
Published: April 2011

ABSTRACTCarbon nanotube field-effect transistors (CNTFETs) were fabricated with metal material (gold) and semiconductor material (bismuth telluride) as the source and drain materials. Highly-purified HiPCO-grown single-walled carbon nanotubes (CNTs) from Carbon Nanotechnologies, Inc. (CNI) were used for the fabrication of CNTFETs. The single-walled carbon nanotubes were ultrasonically dispersed in toluene and dimethylformamide (DMF) with trifluoroacetic acid (TFA), as co-solvent. Dielectrophoresis (DEP) method was used to deposit, align, and assemble carbon nanotubes (CNTs) to bridge the gap between the source and drain of CNTFETs to form the channel. The structure of CNTFET is similar to a conventional field-effect transistor with substrate acting as a back-side gate. Electron-beam evaporation was used to deposit gold and bismuth telluride thin films. Microfabrication techniques such as photolithography, e-beam lithography, and lift-off process were used to define and fabricate the source, drain, and gate of CNTFETs. The gap between the source and drain varied from 800 nm to 3 µm. The drain-source current (IDS) of the fabricated CNTFETs versus the drain-source voltage (VDS) and the gate voltage (VG) was characterized. It was found that in the case of gold (Au) electrodes, the IV curves of CNTFETs clearly show behavior of the CNT (metallic or semiconducting) aligned across the source and drain of CNTFETs, while in the case of bismuth telluride (Bi2Te3) electrodes, the I-V curves are less dependent on the type of CNTs (metallic or semiconducting). The developed carbon nanotube field-effect transistors (CNTFETs) can be a good candidate for the application of nanoelectronics and integrated circuits with a high mobility and fast switching.
Transistor Level Integration of Compound Semiconductor Devices and CMOS (CoSMOS
Authors: Elliott Kenneth , Patterson Pamela , Li James C. , Royter Yakov , Hussain Tahir 
Published: April 2011

ABSTRACTIn the COSMOS program, HRL Laboratories, LLC. is developing technology for intimate integration of CMOS devices with 400 GHz InP HBTs to form complex integrated circuits. This research is investigating innovative approaches to the transistor-scale integration of compound semiconductor and silicon-based transistors so as to enable revolutionary advances in science, devices, circuits, and systems.
Enhancement Mode GaN MOSFETs on Silicon Substrates with High Field-effect Mobility
Authors: Kambayashi Hiroshi , Niiyama Yuki , Ootomo Shinya , Nomura Takehiko , Iwami Masayuki , Satoh Yoshihiro , Kato Sadahiro , Yoshida Seikoh 
Published: April 2011

ABSTRACTIn this report, we have demonstrated enhancement-mode n-channel GaN MOSFETs on silicon (111) substrates. We observe a high field-effect mobility of 115 cm2/Vs, the best report for GaN MOSFET fabricated on a silicon substrate to our knowledge. The threshold voltage was estimated to be +2.7 V, and the maximum operation current was over 3.5 A. This value is the largest which have ever been reports.
Molecular Beam Epitaxy of AlN Layers on Si (111)
Authors: Moreno Jean-Christophe , Frayssinet Eric , Semond Fabrice , Massies Jean 
Published: April 2011

ABSTRACTIn this work, we present a study of epitaxial Aluminium Nitride (AlN) for thin film bulk acoustic wave (BAW) applications. Molecular beam epitaxy (MBE) was used to perform high crystalline quality AlN thin films growth on different silicon substrate preparations. A morphological study was performed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), while structural properties and acoustic wave speed were respectively assessed by X-ray diffraction and acoustic picoseconds.
Condensation Mechanism for the Formation of Relaxed SiGe Layer Grown-on-Insulator
Authors: Lee Hun-Joo , Lee Gon-Sub , Han Young-Soo , Hong Seuck-Hoon , Shim Tae-Hun , Park Jae-Gun 
Published: April 2011

ABSTRACTThe condensation method to grow a strained SiGe layer-on-insulator (ε-SGOI) has attracted interests for the application of high speed complementary metal–oxide–semiconductor field-effect transistors (CMOSFETs) because of high quality properties and effective process cost. Although many reports presented its superiority in a device performance to bonding and dislocation sink technologies, the mechanism by which the condensation method produces ε-SGOI has also not been clearly explained and the surface properties have not been evaluated. Thus, we investigated condensation mechanism in detail by characterizing a surface property and Ge profile in SiGe layer. For the experiment, first, a SiGe layer on silicon-on-insulator layer was epitaxally grown at 550 °C, and three different oxidation thicknesses were grown at 950 °C, i.e., 40, 60, 90 nm. From our investigation results, we found that there are three steps in producing ε-SGOI. For the first step, by the 40-nm-thick oxidation, a diffusion of Ge atoms in SiGe layer into Si layer-on-insulator was generated and Ge atoms were segregated into only surface oxide. It was observed that Ge profile of SiGe layer was shown a less graded profile. And, in the second step with 60-nm-thick oxidation, Ge atoms in SiGe layer into Si layer-on-insulator was diffused further than a first step did and Ge atoms were segregated into surface oxide. It was observed that Si layer was shown a fully graded profile. Lastly, in the third step with 90-nm-thick oxidation, the diffusion of Ge atoms in SiGe layer into Si layer-on-insulator was finished completely and Ge atoms were segregated into both surface and buried oxides. It was confirm that Ge profile of SiGe layer was shown a Gaussian profile rather than a graded profile, and dislocation sink occurred. Therefore, our talk will focus on the explanation for the mechanism by which condensation method produces ε-SGOI via characterizing a surface property, SiGe thickness, a remained Si thickness on insulator, and Ge concentration in SiGe layer.
Growth of AlGaN/GaN HEMTs on Silicon Substrates by MBE
Authors: Semond Fabrice , Cordier Yvon , Natali Franck , Le Louarn Arnaud , Vézian Stéphane , Joblot Sylvain , Chenot Sébastien , Baron Nicolas , Frayssinet Eric , Moreno Jean-Christophe , Massies Jean 
Published: April 2011

ABSTRACTDuring the last ten years, we have developed an efficient growth process of nitrides on silicon substrates by molecular beam epitaxy. In collaboration with partners AlGaN/GaN HEMTs on Si having promising performances have been fabricated. Focusing on the growth aspect and underlying some of the key issues, we present in this paper an overview of our contribution in the field of AlGaN/GaN HEMTs on Si substrates.
Strong Light-Matter Coupling in GaN-Based Microcavities Grown on Silicon Substrates
Authors: Semond Fabrice , Sellers Ian Roberts , Ollier Nadège , Natali Franck , Byrne Declan , Réveret François , Stokker-Cheregi Flavian , Bejtka Katarzyna , Gurioli Maximo , Vinattieri Anna , Vasson Aimé , Disseix Pierre , Leymarie Joël , Leroux Mathieu , Massies Jean 
Published: April 2011

ABSTRACTWe present an overview of our work concerning the fabrication of GaN-based microcavities grown on silicon substrates dedicated to the observation of the strong light-matter coupling regime. In the view of recent promising results in the field, prospects regarding the improvement of heterostructures in order to observe room temperature polariton lasing from a GaN-based microcavity grown on a silicon substrate will be discussed.
AlGaN Transition Layers on Si (111) Substrates - Observations of Microstructure and Impact on Material Quality
Authors: Roberts John C. , Cook James W. , Rajagopal Pradeep , Piner Edwin L. , Linthicum Kevin J. 
Published: April 2011

ABSTRACTIII-nitride materials have different crystal structures and properties than the substrates commonly used for their deposition, including silicon, silicon carbide and sapphire. These differences, such as thermal expansion coefficient and lattice constant, necessitate the use of a transition layer to accommodate the resulting stress between substrate and the epitaxially grown III-N layers. AlxGa1−xN based transition layers are one proven solution used for the growth of device quality GaN layers on Si (111) substrates. The use of such transition layers enables the deposition of state of the art AlGaN/GaN high electron mobility transistor epitaxial structures that, upon fabrication into devices, exhibit high performance and excellent reliability.Examination of the microstructure of these AlxGa1−xN transition layers, by transmission electron microscopy (TEM) and other methods, reveals some interesting properties that can help explain how high quality III-N epitaxy can be performed in a system with significant thermal and lattice mismatch. Observations that will be reported on and discussed in this presentation are (1) the role that a thin strain absorbing amorphous SiNx layer at the Si substrate/transition layer interface plays in the reduction of the formation of misfit dislocations, (2) the low screw dislocation density (less than ȼ107/cm2) in these III-N films relative to edge and mixed dislocation densities, and (3) the role that the substrate type and quality can play on dislocation type and density.
Epitaxial Growth of High-κ Dielectrics for GaN MOSFETs
Authors: Jur Jesse S. , Wheeler Ginger D. , Veety Matthew T. , Lichtenwalner Daniel J. , Barlage Douglas W. , Johnson Mark A. L. 
Published: April 2011

ABSTRACTHigh-dielectric constant (high-κ) oxide growth on hexagonal-GaN (on sapphire) is examined for potential use in enhancement-mode metal oxide semiconductor field effect transistor (MOSFET). Enhancement-mode MOSFET devices (ns > 4×1013 cm−2) offer significant performance advantages, such as greater efficiency and scalability, as compared to heterojunction field effect transistor (HFET) devices for use in high power and high frequency GaN-based devices. High leakage current and current collapse at high drive conditions suggests that the use of a high-κ insulating layer is principle for enhancement-mode MOSFET development. In this work, rare earth oxides (Sc, La, etc.) are explored due to their ideal combination of permittivity and high band gap energy. However, a substantial lattice mismatch (9-21%) between the rare earth oxides and the GaN substrate results in mid-gap defect state densities and growth dislocations. The epitaxial growth of the rare earth oxides by molecular beam epitaxy (MBE) on native oxide passivated-GaN is examined in an effort to minimize these growth related defects and other growth-related limitations. Growth of the oxide on GaN is characterized analytically by RHEED, XRD, and XPS. Preliminary MOS electrical analysis of a 50 Å La2O3 on GaN shows superior leakage performance as compared to significantly thicker Si3N4 dielectric.
Flash Memory Scaling: From Material Selection to Performance Improvement
Authors: Hou Tuo-Hung , Lee Jaegoo , Shaw Jonathan T. , Kan Edwin C. 
Published: April 2011

AbstractBelow the 65-nm technology node, scaling of Flash memory, NAND, NOR or embedded, needs smart and heterogeneous integration of materials in the entire device structure. In addition to maintaining retention, in the order of importance, we need to continuously make functional density (bits/cm2) higher, cycling endurance longer, program/erase (P/E) voltage lower (negated by the read disturbance, multi-level possibility and noise margin), and P/E time faster (helped by inserting SRAM buffer at system interface). From both theory and experiments, we will compare the advantages and disadvantages in various material choices in view of 3D electrostatics, quantum transport and CMOS process compatibility.
Realization of Hybrid Silicon core/silicon Nitride Shell Nanodots by LPCVD for NVM Application
Authors: Colonna Jean Philippe , Molas Gabriel , Gely Marc W , Bocquet Marc , Jalaguier Eric , De Slavo Barbara , Grampeix Helen , Brianceau Pierre , Yckache Karim , Papon Anne-Marie , Auvert Geoffroy , Bongiorno Corrado , Lombardo Salvatore 
Published: April 2011

AbstractWe present the realization of hybrid silicon core/silicon nitride shell nanodots by Low Pressure Chemical Vapor Deposition (LPCVD) and their application as floating gate in Non Volatile Memory (NVM) devices. The LPCVD process includes three steps: nucleation using SiH4, selective growth of the silicon nuclei using SiH2Cl2 and finally selective growth of silicon nitride using a mixture of SiH2Cl2 and NH3 around the silicon dot. The two first steps have already been described in literature. We will therefore focus on the selective growth of a nitride layer on silicon dots. Morphological characterization using Scanning Electron Microscopy (SEM) allows control over dots size – 5 to 10nm – and density – up to 1E12/cm2. High Resolution Transmission Electron Microscopy (HRTEM) shows a crystalline silicon core and an outer shell of amorphous silicon nitride. Energy Filtered TEM pictures confirm that the nitride layer is deposited only around the silicon dots and not on the oxide. Oxidation resistance of the silicon nitride shell is also investigated. A 2nm thick silicon nitride layer is an efficient barrier to an oxidation at 800°C in dry oxygen for 5 minutes. We thus have a very thin high quality stoechiometric nitride layer. Such a high quality nitride film can only be achieved using in-situ deposition i.e. on an oxide-free silicon surface. Finally, hybrid Si/SiN nanodots are integrated in a single memory cell with high-K interpoly dielectric. Electrical results show large threshold voltage shift of 6V. The use of silicon nitride shells on the silicon dots has therefore two main advantages: it provides both oxidation resistance and charge storage enhancement.
Metallurgical Effects of Solution Heat Treatment Temperatures of Alloy Haynes™ HR-120™ for Land-Based Turbine Application
Authors: Covarrubias O. , Elizarrarás Osvaldo 
Published: April 2011

ABSTRACTHaynes™ HR-120™ alloy is a solid-solution-strengthened heat resistant alloy. The main characteristics of this alloy are strength at elevated temperature combined with resistance to carburizing and sulfidizing environments. Typical solution heat treatment for this alloy is usually performed above 1100°C. Solution heat treatment promotes non-desired precipitates to dissolve and, if deformation parameters are adequate, re-crystallization after forging procedures. It is reported that the solution temperature can also promote non-controlled grain coarsening. This investigation summarizes results on the effect of solution heat treatment on the microstructure of forgings when it is performed at 1000°C, 1050°C and above 1100°C. The experimental conditions resemble industrial environments. The obtained results include the alloy microstructural evolution by optical microscopy and Scanning Electron Microscopy (SEM) and the effect of these heat treatments on mechanical properties such as tensile, hardness and stress-rupture properties.
Cross-Sectional Scanning Tunneling Microscopy of III-V Semiconductor Structures
Authors: Feenstra R. M. , Vaterlaus A. , Woodall J. M. , Collins D. A. , McGill T. C. 
Published: April 2011

ABSTRACTThe method of cross-sectional scanning tunneling microscopy (STM) is described. Illustrative examples are given of studies of III-V semiconductor systems, including low-temperature-grown (LT) GaAs, and InAs/GaSb superlattices. In each case, the STM permits the observation of structural features on an atomic scale. The associated electronic spectroscopy for states a few eV on either side of the Fermi-level can be determined. Such information is relevant for the operation of devices constructed from these layered semiconductor systems.
High Resolution Tem Applied to Nanoscale Structure Studies
Authors: Rio L. Beltran Del , Yacaman M.Jose , Tehuacanero S. , Gomez A. 
Published: April 2011

ABSTRACTIn this work, digital image processing techniques are used to study the structure of small metallic particles imaged under high resolution conditions. An algorithm is devised to extract directly from the micrographs the coordinates of columns of atoms in such a way that the crystal structure of the particles and their boundaries can be determined. For distorted regions (such as grain boundaries) the actual positions can be compared to the ones in the ideal lattice so that a general trend of the distortion field can be elucidated.
Elemental Mapping by Energy-Filtered Electron Microscopy
Authors: Krivanek Ondrej L. , Kundmann Michael K. , Bourrat Xavier 
Published: April 2011

ABSTRACTEnergy-filtered imaging in a transmission electron microscope provides a fast and quantitative technique for mapping the distribution of elements in solids at nm-level resolution. The technique and its instrumental requirements are reviewed, and illustrated in the context of materials science.
Quantitative Hrtem: Measuring Projected Potential, Surface Roughness and Chemical Composition
Authors: Schwander P. , Kisielowski C. , Baumann F.H. , Kim Y.O. , Ourmazd A. 
Published: April 2011

ABSTRACTWe describe how general lattice images may be used to measure the variation of the potential in crystalline solids in any projection, with no knowledge of the imaging conditions. This approach is applicable to structurally perfect samples, in which interfacial topography, or changes in composition are of interest. We present the first atomic-level topographic map of a Si/SiO2 interface in plan-view, and the first microscopic compositional map of a Si/GeSi/Si quantum well in cross-section.