bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Crystallography of Metal Halides formed within Single Walled Carbon Nanotubes
Authors: Sloan J. , Brown G. , Bailey S.R. , Coleman K.S. , Flahaut E. , Friedrichs S. , Xu C. , Green M.L.H. , Dunin-Borkowski R.E. , Hutchison J.L. , Kirkland A.I. , Meyer R.R. 
Published: April 2011

AbstractThe crystal growth behaviour and crystallography of a variety of metal halides incorporated within single walled carbon nanotubes (SWNTs) as determined by high resolution electron microscopy (HRTEM) is described. Simple packed structures, such as the alkali halides, form related structures within SWNTs that are found to be integral atomic layers in terms of their thickness as a function of the encapsulating SWNT diameter. An enhanced HRTEM image restoration technique reveals precise data concerning lattice distortions present in these crystals. More complex structures, such as those derived from 3D complex, layered and chain halides form related crystal structures within SWNTs. In narrow SWNTs (i.e. with diameters less than ca. 1.6 nm), structures consisting of individual 1D polyhedral chains (1D-PHCs) were obtained that were derived from the corresponding bulk halides structures. In the case of infinite 3D network and layered halides, the 1D polyhedral chains form with lower co-ordinations than in the bulk. Molecular halides also intercalate into SWNTs but these do not readily form organised structures within SWNTs.
Low-Voltage Electron Transport in Self-Assembled Nanocrystal Arrays
Authors: Black C. T. , Murray C. B. , Sandstrom R. L. , Sun Shouheng 
Published: April 2011

AbstractElectrons traverse two-dimensional nanocrystal arrays by sequential tunneling between neighboring nanocrystals. Analysis of array conductance at zero bias-voltage gives information about underlying nanocrystal uniformity, as well as the relevant single-electron charging energy. We discuss low-temperature measurements of two-dimensional self-assembled superlattices composed of 10 nanometer diameter cobalt nanocrystals, with ∼2 nm inter-nanocrystal spacing.
Status of Ion Projection Lithography
Authors: Bruenger Wilhelm H. , Kaesmaier Rainer , Loeschner Hans , Springer Reinhard 
Published: April 2011

AbstractAs part of the European MEDEA project on Ion Projection Lithography (IPL), headed by Infineon Techologies, a process development tool (PDT) has been assembled at IMS, Vienna, with the final target of 50 nm resolution in a 12.5 mm exposure field at 4× demagnification. The ion-optical system (PDT-IOS) has been integrated, including the LEICA mask changer and a sophisticated metrology stage with in-situ diagnostics. In parallel, the LEICA wafer stage and the vacuum compatible off-axis ASML wafer alignment system have been realized. At the moment (Nov00) the He+ ion beam is aligned until the mask level. Ion beam proximity wafer exposures directly behind the mask show a performance of the illumination optics as predicted. 150 mm stencil masks with 125mm diameter, 3μm Si membranes, 50mm × 50mm design field, have been produced by IMS-Chips, Stuttgart. There is expectation to start the PDT-IOS test phase in Q1/01. Using the experimental ion projector at the Fraunhofer-Institute ISiT in Berlin recent resolution tests have demonstrated 50 nm lines and spaces without proximity effect in standard Shipley DUV resist UVIIHS at an exposure dose of 0.5 μC/cm2 for 75 keV He+ions. This was accomplished by 8.5 × demagnification of a new generation of stencil test masks from IMSChips. One further promising application of IPL is the resistless structuring of thin magnetic films to produce magnetic nano dots for future ≥ 100 G bit/in2 storage devices. A consortium of IBM Germany - Speichersysteme Mainz, Fraunhofer-ISiT, LEICA Jena and IMS-Chips in cooperation with IMS-Vienna has been formed to evaluate this technology.
Spatially controlled CdSe nanocrystal distribution in phase separated polymer blend films
Authors: Asami Harumi , Saita Soichiro , Kamiya Itaru , Yoshie Kenichi 
Published: April 2011

AbstractWe report the fabrication and characterization of the self-assembled structure of tri-n-octylphosphine oxide (TOPO)-capped CdSe nanocrystals in binary polymer phase separated films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(2-vinylpyridine) (P2VP). These structures are formed via demixing of CdSe nanocrystals and binary polymer during spin coating. The nanocrystals preferentially segregate to the PS-rich phase in phase separated PS/PMMA and to the P2VP-rich phase in phase separated PS/P2VP, as shown by optical microscopy and photoluminescence images. For CdSe/PS/PMMA, we attribute the driving force for CdSe segregating to the PS-rich domain to the stronger attractive interaction of TOPO on PS with respect to PMMA due to polarity, and in the case of CdSe/PS/P2VP, segregating to the P2VP-rich domain to the interaction such as coordinate bonds being formed between pyridine groups and surface Cd atoms.
Dynamic Light Scattering at CdSe Nanocrystals and CdSe Cluster-Molecules
Authors: Eichhöfer A. , Hänisch C.V. , Jacobsohn M. , Banin U. 
Published: April 2011

AbstractHigh performance dynamic light scattering (DLS) has been used to determine the hydrodynamic diameters of CdSe-nanocrystals as well as CdSe cluster molecules in a size range of 1 to 10 nm. The method enables the determination of the particle sizes including the ligand shells directly in solution. Consistent with the blue shift of the absorption onset by reducing the particle sizes the values for the hydrodynamic radii decrease. For the CdSe nanoparticles the measured sizes were compared with the diameters determined by TEM experiments; the sizes of the cluster molecules were on the other hand estimated from the space filling models of the single crystal X-ray structure determination. Regarding both types of compounds, DLS yield comparable values for the radii, indicating that it provides a potentially important tool in addition to other size determining techniques like TEM, which operates at more drastic conditions, and powder X-ray diffraction being difficult to interpret below 5 nm.
Interband Transitions in Si Quantum Wires grown in {100} plane
Authors: Zianni X. , Nassiopoulou A.G. 
Published: April 2011

AbstractWe present calculations on the spontaneous emission rates of Si rectangular quantum wires grown in the {100} plane. The electron and holes states are calculated within an effective mass approximation model. For holes, the minimum of the one-dimensional sub-bands is at the Γ- point. For electrons, the six anisotropic valleys at the conduction band minimum of bulk Si are not equivalent in the quantum wires and so, the minima of the energy sub-bands depend on the growth direction of the wire. For some wire directions in the {100} plane, the minimum of the ground electron sub-band is at the Γ-point. The directional dependence of the electron states is reflected on the spontaneous emission of the quantum wires. Light emission from Si quantum wires of diameters of a few nanometers can have direct transition character in the visible range. Phonon assisted transitions are then also present, but their intensity is three orders of magnitude smaller than the intensity of direct transitions. In Si quantum wires with indirect band gap the intensity and the peak position of the phonon assisted transitions exhibit dependence on the wires direction.
Control of the Arrangement of Nano Holes on Silicon Surface
Authors: Ohno Y. , Ichihashi T. , Takeda S. 
Published: April 2011

AbstractWe have found that nanoholes are formed on silicon surfaces by the irradiation of electrons whose energy is above 40 keV. We have systematically investigated the size and distribution of nanoholes. In the temperature range from 300 K to 600 K, both the radii of nanohole and the distance of nearest-neighbor nanoholes increase with increasing temperature; the planar density of nanoholes decreased with increasing temperature. The data follow a simple Arrhenius law, suggesting that nanoholes are formed through the diffusion of surface vacancies. The diffusion energy is estimated to be 50 meV. Surface nanoholes are formed even at 4 K at which surface vacancies cannot diffuse thermally, presumably due to athermal diffusion of surface vacancies.
Erbium Emission from Silicon Based Photonic Bandgap Materials
Authors: Lopez Herman A. , Lugo J. Eduardo , Chan Selena , Weiss Sharon M. , Striemer Christopher C. , Fauchet Philippe M. 
Published: April 2011

AbstractControl over the 1.5 µm emission from erbium is desirable for communication and computational technologies because the erbium emission falls in the window of maximum transmission for silica based fiber optics. Tunable, narrow, directional, and enhanced erbium emission from silicon based 1-D photonic bandgap structures will be demonstrated. The structures are prepared by anodic etching of crystalline silicon and consist of two highly reflecting Bragg reflectors sandwiching an active layer. The cavities are doped by electro-migrating the erbium ions into the porous silicon matrix, followed by high temperature oxidation. By controlling the oxidation temperature, porosity, and thickness of the structure, the position of the erbium emission is tuned to emit in regions where the normal erbium emission is very weak. The erbium emission from the cavity is narrowed to a full width at half maximum (FWHM) of 12 nm with a cavity quality factor Q of 130, highly directional with a 20 degree emission cone around the normal axis, and enhanced by more than one order of magnitude when compared to its lateral emission. Erbium photoluminescence (PL) from porous silicon 2-D photonic bandgap structures is also demonstrated.
Er3+ Photoluminescence Properties of Erbium-doped Si/SiO2 Superlattices with sub-nm Thin Si Layers
Authors: Ha Yong Ho , Kim Sehun , Moon Dae Won , Jhe Ji-Hong , Shin Jung H. 
Published: April 2011

AbstractThe effect of varying the Si layer thickness on the Er3+ photoluminescence properties of Er-doped Si/SiO2 superlattice is investigated. We find that as the Si layer thickness is reduced from 3.6 nm down to a monolayer of Si, the Er3+ luminescence intensity increases by over an order of magnitude. Temperature dependence of the Er3+ luminescence intensity and time-resolved measurement of Er3+ luminescence intensity identify the increase in the excitation rate as the likely cause for such an increase, and underscore the importance of the Si/SiO2 interface in determining the Er3+ luminescence properties.
Charge Storage Mechanism in Nano-Crystalline Si Based Single-Electron Memories
Authors: Hinds Bruce J. , Yamanaka Takayuki , Oda Shunri 
Published: April 2011

AbstractA memory device sensitive to a single electron stored in a nanocrystalline Si dot has been synthesized allowing for the study of charge retention lifetime. A 50 nm by 20 nm transistor channel is synthesized by E-beam lithography followed by reactive ion etching of thin (20nm) Silicon-on-Insulator (SOI) channel. This small area of the narrow channel allows for the isolation of a single nano-crystalline Si dot and elimination of channel percolation paths around the screening charge. Remote Plasma Enhanced CVD is used to form 6±2nm diameter nc-Si dots in the gas phase from a pulsed SiH4 source. Electrons stored in a dot results in an observed discrete threshold shift of 90 mV. Analysis of lifetime as a function of applied potential and temperature show the dot to be an acceptor site with nearly Poisson lifetime distributions. An observed 1/T2 dependence of lifetime is consistent with a direct tunneling process, thus interface states are not the dominant mechanism for electron storage in this device structure. Median lifetimes are modeled by a direct tunneling process, which is influenced by gate bias and dot size.
Ballistic Electron Surface-Emitting Cold Cathode by Porous Polycrystalline Silicon Film Formed on Glass Substrate
Authors: Komoda Takuya , Ichihara Tsutomu , Honda Yoshiaki , Aizawa Koichi , Koshida Nobuyoshi 
Published: April 2011

AbstractIt is demonstrated that a porous polycrystalline silicon (PPS) film is useful as a ballistic electron emitter for excitation source of a flat panel display. A 1.5 µ m polysilicon layer is deposited on a silicon substrate by Low Pressure Chemical Vapour Deposition (LPCVD) technique and subsequently anodised in an ethanoic HF solution and oxidised in a Rapid Thermal Oxidation (RTO) furnace. A thin Au film is deposited onto the RTO-treated PPS layer and used as a top electrode. The electron emission current Ie and the diode current Ips are measured as a function of the bias voltage Vps. Electron emission of which onset voltage is about 8 V rapidly increases with increasing Vps. The Ie value reaches about 2 mA/cm2 for Vps= 20 V at which the emission efficiency defined as Ie/Ips is about 1 %. The emission mechanism has also been investigated in terms of the correlation between the emitted electron energy and the structure of PPS layer. The observed energy distribution curve of output electrons suggests that the PPS layer acts as a ballistic transport medium and the emission occurs based on multiple tunnelling through silicon nanocrystallites. The PPS layer is also formed on the polysilicon layer deposited on a glass substrate by Plasma Enhanced Chemical Vapour Deposition (PCVD) technique. In this case, the film is treated by an electrochemical oxidation (ECO) in an H2SO4 solution. Similar emission characteristics are observed, although the emission current is lower than that formed on silicon substrate. We also demonstrate the 2.6 inches diagonal 53×40 pixels multicolour flat panel display. We name it ballistic electron surface-emitting display device (BSD). BSD shows the possible application to the future flat panel display.
CVD growth of Si Nanocrystals on Dielectric Surfaces for Nanocrystal Floating Gate Memory Application
Authors: Madhukar Sucharita , Smith K. , Muralidhar R. , O'Meara D. , Sadd M. , Nguyen B-Y. , White B. , Jones B. 
Published: April 2011

AbstractInitial stages of growth of silicon on dielectric surface proceeds through Volmer-Webber growth mode (through island formation) and coalescence of islands to form a continuous thin film layer. Growth of silicon nanocrystals on dielectric surface can be achieved by controlling the nucleation and growth kinetics of these nanocrystals on the dielectric surface. In this study, we present CVD growth of Si nanocrystals on oxide, oxynitride and nitride surfaces using silane based chemistry. The effect of process conditions such as deposition temperature, precursor flow rate, carrier gas on nanocrystal incubation time, size and density of nanocrystals was studied. The nucleation and growth rate of the silicon nanocrystals is also a strong function of the surface chemistry, surface structure and strain in the dielectric film. We have studied the effect of oxide deposition temperature and surface pretreatments on the nucleation and growth characteristics of the silicon nanocrystals.
Oxidation of Silicon Nanocrystals
Authors: Scheer Kristen C. , Madhukar Sucharita , Muralidar Ramachandran , Lozano Jose , O'Meara David , Bagchi Sandeep , Conner James , Perez Carlos , Sadd Michael , Jones R. E. , White B. E. 
Published: April 2011

AbstractSilicon nanocrystals have made a recent appearance in the literature because of their potential importance in microelectronic[1] and optoelectronic [2] devices. For example, replacing the traditional Si floating gate in nonvolatile memory field effect transistors with nanocrystals has been shown to produce more reliable and lower power memory devices than traditional transistors [1]. Controlled oxidation of Si nanocrystals is desirable in the processing of Si quantum dots for these devices. If controlled oxidation is attainable, then it could be used to control nanocrystal size, achieve high nanocrystal density, and achieve a high quality interface between Si dot and SiO2 gate oxide layer in nanocrystal based memory. In this work, we report the oxidation properties of various sized silicon nanocrystals, deposited by low-pressure chemical vapor deposition, in different oxidizing environments. In the literature, when a Si column or dot is oxidized below the viscoelastic temperature of SiO2 (950 oC), the oxidation will self-limit to a Si core size that is dependent on the oxidizing conditions and the initial particle size. This self-limiting phenomenon is said to occur because of the presence of a compressive stress in the oxide layer that limits the diffusion of the oxidizing agent through the SiO2 to the Si- SiO2 interface. This compressive stress is present at the interface because of the difference in the density of the oxide and the Si and is enhanced by the radius of curvature of the dot. This self- limiting oxidation phenomenon will be studied experimentally using microscopy techniques and the effect of the constrained structure will be characterized.
Theory of electronic transport in semiconductor nanostructures.
Authors: Niquet Y.M. , Delerue C. , Allan G. , Lannoo M. 
Published: April 2011

AbstractWe review the orthodox theory of single charge tunneling in a semiconductor quantum dot and we extend it to treat both single electron and hole charging effects. We analyze recent tunneling spectroscopy experiments. We show that for sufficiently large bias voltages V, both electrons and holes can tunnel into the quantum dot, leading to specific features in the I(V) curve. We present detailed simulations of the I(V) curves based a tight binding method for the electronic structure. A very good agreement is obtained with available experiments on InAs nanocrystals, allowing a complete interpretation of the spectra. Finally, we make some predictions concerning Si nanocrystals.
Drastic Reduction of Threading Dislocation Density of AlGaN on SiC Wafer by Using Highly-Si-Incorporated AlGaN Superlattice
Authors: Hirayama Hideki , Ainoya Makoto , Kinoshita Atsuhiro , Hirata Akira , Aoyagi Yoshinobu 
Published: April 2011

ABSTRACTA new in-situ technique to reduce threading dislocation density (TDD) within sub- micron growth is demonstrated by using metal-organic vapor-phase epitaxy (MOVPE). We achieved drastic reduction of TDD of AlGaN buffer on SiC substrate by inserting highly-Si- incorporated AlGaN/undoped AlGaN superlattice (SL). TDD of AlGaN was decreased from 2×1010 to 7×107 cm−2 by inserting the SL with the total growth thickness of 0.8νm. Si incorporation in AlGaN SL was estimated to be 1.2×1020 cm−3. This technique is exactly in- situ process without complicated fabrication processes, and the surface is kept flat throughout the total growth. This method is especially useful on SiC wafer in order to prevent cracks with thin growth layer. We confirmed the similar effects for GaN and AlGaN buffer on sapphire substrates.
Emission Characteristics of GaN-Based EL Device with AC Operation
Authors: Honda Tohru , Kawanishi Hideo 
Published: April 2011

ABSTRACTGaN-based electroluminescence devices (ELDs) were fabricated using a GaN powder as an emission layer. The electroluminescence spectra of the GaN ELDs under AC operation were observed at room temperature. The emission characteristics of GaN-based ELDs were studied to compare the EL spectra and the cathodoluminescence (CL) spectra. It was clarified that the EL spectra were similar to the CL spectra of a GaN emission layer. The emission peaks in the EL spectra were shifted toward the high-energy side with increasing operation frequency.
High Resistivity GaN Formed by Ion Implantation
Authors: Kudo Jun , Hishida Yuji , Watanabe Masanori , Hatayama Tomoaki , Fuyuki Takashi 
Published: April 2011

ABSTRACTAdvanced high frequency devices using GaN-based semiconductor require the technology to form high resistivity regions with high thermal stability to electrically isolate the active elements from surroundings, as well as from the underlying substrate. The present paper describes the preparation of thermally stable, high resistivity GaN layers by ion implantation. It was confirmed that C or Zn implantation yielded high resistivity layers. In particular, Zn implantation yielded the layers with resistivity on the order of 1010 cm, which could be sustained at temperatures as high as 1000.
Hot Electron Transport in AlN
Authors: Collazo Ramón , Schlesser Raoul , Roskowski Amy , Davis Robert F. , Sitar Z. 
Published: April 2011

ABSTRACTThe energy distribution of electrons that were transported through a thin intrinsic AlN film was directly measured as a function of the applied field. The measurements were realized by extracting the electrons into vacuum through a semitransparent Au contact and measuring their energy using an electron spectrometer. At moderate applied fields (350 kV/cm), the energy distribution followed a Maxwellian model corresponding to an electron temperature of 2700 K and a drift component below the spectrometer resolution. At higher fields, intervalley scattering was evidenced by the presence of a second peak at 0.7 eV. This coincides well with the energy position of the L-M valley in AlN. To the best of our knowledge, these are the first measurements that offer direct evidence of intervalley scattering in any solid system.
Synthesis, Structure, and Luminescence of A2B4C5 Nitrides
Authors: Bondar Vyacheslav , Axelrud Lev , Davydov Vladimir , Felter Tom 
Published: April 2011

ABSTRACTIn order to extend the possibilities of doping of nitrides with activators of different valent and coordination states the complex A2B4C5 nitrides were investigated. The crystallochemical computer simulation of the new phosphor materials based on Mn, Ti and Eu-doped nitrides A2B4C5 has been made. Methods of synthesis of CaSiN2, and MgSiN2 have been developed, and X-ray diffraction analysis of these materials has been carried out. ESR and cathodoluminescent properties of MgSiN2, and CaSiN2 doped with manganese and europium have been studied.
Deep Level Formation in Undoped and Oxygen-Doped GaN
Authors: Gregie J. M. , Korotkov R. Y. , Wessels B. W. 
Published: April 2011

ABSTRACTDeep level defects in oxygen doped GaN grown by metal-organic vapor phase epitaxy were investigated. Using steady-state photocapacitance (SSPC) spectroscopy, three deep levels with optical ionization energies of 1.0, 1.4, and 3.25 eV were observed in both nominally undoped and oxygen-doped samples. The total deep level defect concentrations ranged from 6 × 1015 cm-3 in undoped films to 3 × 1016 cm-3 in oxygen-doped films. The concentration of the 3.25 eV level defect increased upon oxygen doping, while the concentrationof the 1.0 and 1.4 eV levels were essentially dopant independent. From the measured concentrations the formation energies of the defects were calculated and compared to energies calculated using density functional theory.