bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gate-Prior-To-Isolation Cmos-Technology with Through-The-Gate-Implanted Ultra-Thin Gate Oxides
Authors: Schwalke Udo , Gruensfelder Christian , Gschwandtner Alexander , Innertsberger Gudrun , Kerber Martin 
Published: April 2011

ABSTRACTWe have realized direct-tunneling gate oxide (1.6nm) NMOS and PMOS transistors by means of through-the-gate-implantation in a comer parasitics-free shallow-trench-isolation CMOS technology. In order to take full advantage of in-situ cluster-tool processing and to preserve initial wafer-surface quality, the essential part of the MOS gate is fabricated prior to device isolation and through-the-gate-implantation is utilized for well- and channel doping. In addition, a fully-reinforced-gate-oxide-perimeter is provided and trench comer parasitics are eliminated by the advanced process architecture EXTIGATE without increasing process complexity.
The Effect of Grown-In Point Defects on Sb Diffusion in MBE-Grown Si and Sige
Authors: Bonar J.M. , Mcgregor B.M. , Willoughby A.F.W. , Paine A.D.N. 
Published: April 2011

ABSTRACTThe diffusion of antimony in Si and SiGe under the influence of grown-in point defects is studied in this work. The layers were grown by very low temperature MBE, and the diffused profiles measured using SIMS analysis. Fast diffusion of Sb is observed in both Si and SiGe. and is thought to be caused by grown-in point defects, specifically vacancies, arising from the very low temperature MIBE growth. The vacancies may be removed by heat treatments. and it was found that the processing the samples received before the heat treatments caused the most substantial diffusion. Comparison of the diffusivities for inert diffusion at 850°C following the heat treatments suggests 30 minutes at 800°C is sufficient to remove the majority of the grown-in defects. The diffusion of Sb in Si is thus demonstrated to be a very sensitive monitor of grown-in vacancies, and dopants which diffuse at least partly by vacancy mediated processes would be expected to be affected by this effect.
Diffusion of Phosphorus in Strained Si/SiGe/Si Heterostructures
Authors: Kuznetsov A. Yu. , Christensen J. S. , Linnarsson M. K. , Svensson B. G. , Radamson H. H. , Grahn J. , Landgren G. 
Published: April 2011

ABSTRACTPhosphorus diffusion in a biaxially compressed Si0.87Ge0.13 film has been investigated in the temperature range of 810–900°C. A significant enhancement of the P diffusion in the biaxially compressed Si0.87Ge0.13 in comparison with P diffusion in Si is observed. Injection of Si self-interstitials (I) during oxidation of a Si-cap in Si/Si0.87Ge0.13/Si heterostructures is used to characterize the atomic mechanism of P diffusion in Si0.87Ge0.13. It is found that the upper limit of the interstitial fraction of the P diffusion in Si0.87Ge0.13 is 0.87 of that in Si. A comparison between B and P diffusivities in SiGe supports the hypothesis of the pairing-controlled mechanism for the diffusion of B in SiGe.
Ab-Initio Pseudopotential Calculations of Boron Diffusion in Silicon
Authors: Windl W. , Bunea M. M. , Stumpf R. , Dunham S. T. , Masquelier M. P. 
Published: April 2011

ABSTRACTIn this work we investigate boron diffusion as a function of the Fermi-level position in crystalline silicon using ab-initio calculations and the nudged elastic band method to optimize diffusion paths. Based on our results, a new mechanism for B diffusion mediated by Si self-interstitials is proposed. We find a two-step diffusion process for all Fermi-level positions, which suggests a kick-out with a directly following kick-in process without extensive B diffusion on interstitial sites in-between. Our activation energy of 3.47 – 3.75 eV and diffusion-length exponent of -0.55 to -0.18 eV are in excellent agreement with experiment.
In Situ Etch Rate Measurements by Alpha-Particle Energy Loss
Authors: Levy Y. , Ballestad A. , Davies M. , Feng Y. , Kelson I. , Mandeville W.J. , Pacradouny V. , Schmalz A. , Tiedje T. , Young J.F. 
Published: April 2011

ABSTRACTWhen alpha-particles pass through thin films they lose an amount of energy proportional to the film thickness with the proportionality constant depending on the film composition. Thus, by measuring this energy loss one can determine the film thickness. We have applied this technique to measurements of the etch rate of various III-V semiconductor layers grown by molecular beam epitaxy. Prior to film growth, GaAs substrates were recoil-implanted with the alpha-emitting 224Ra isotope by exposure to a 5µCi source of 228Th. The implanted isotope decays with a half-life of 3.7 days, which allows measurements to be done for up to about two weeks after implantation. Following growth, the samples were etched in an electron cyclotron resonance etcher using a Cl2/BCl3/Ar gas mixture. As the film is etched the energy of the alpha-particles emitted from the surface increases. By introducing a high resolution Si detector into the etcher we are able to measure changes in the alpha-emission spectrum without removing the sample from the etcher. Thickness changes with an uncertainty of 5–10nm are obtained in 5 minute measurements at the end of each etch step. Some of the samples were also measured by SEM, yielding results in good agreement with values obtained by the alpha-particle measurements. As an example of an application of the technique we will describe measurements of the temperature dependence of the etch rate of GaAs in the 15–150 °C temperature range using optical bandgap thermometry to determine the substrate temperature. In a second example, we explore the application of the technique to etch rate of short pitch (250–500nm) grating. In this case the shape of the alpha-spectrum is sensitive to the profile of the etched trenches.
Extension of Multichannel Spectroscopic Ellipsometry into the Ultraviolet for Real Time Characterization of the Growth of Wide Bandgap Materials from 1.5 to 6.5 eV
Authors: Zapien J. A. , Collins R. W. , Messier R. 
Published: April 2011

ABSTRACTIn this article, we report the results of a successful effort to extend rotating-polarizer multichannel ellipsometry into the ultraviolet (uv) spectral region above 5 eV. Key modifications over previous system designs include (i) incorporation of a see-through deuterium (D2) lamp that allows a tandem Xe/D2 source configuration for a usable spectral output from 1.5 to 6.5 eV, (ii) MgF 2 Rochon polarizers for high transmission in the uv without the need for optical activity corrections, and (iii) a spectrograph with a concave grating blazed at 2500 A and internally mounted order-sorting filters. With these modifications, we can collect 132-point ellipsometric spectra over the range from 1.5 to 6.5 eV with a minimum acquisition time of 24.5 ms (one optical cycle). For averages over two and eighty optical cycles (requiring 49 ms and 1.96 s, respectively), the standard deviations in (Ψ, Δ) are (0.04°, 0.08°) and (0.008°, 0.015°), respectively, measured on a thermally-oxidized silicon wafer at a photon energy of 6 eV. In this first report, we briefly describe problems faced in the development of the new instrument. As an example of the applications of the instrument, we present the results of a real time study of the growth of a hexagonal boron nitride (BN) thin film by rf magnetron sputtering on a Si wafer substrate at a temperature of 250°C. The instrument is expected to be useful in BN film growth studies since the additional data in the uv assist in discriminating the wide band gap (Eg) hexagonal (4 < Eg < 5.8 eV) and cubic (Eg > 6 eV) phases of this material.
Electrical Injection and Transport in Films of Semiconductor Nanocrystals
Authors: Ginger D.S. , Greenham N.C. 
Published: April 2011

ABSTRACTWe study injection and transport in thin disordered films of CdSe nanocrystals between metal electrodes, We investigate the current-voltage characteristics of these devices as a function of electrode material, nanocrystal size, and temperature. We also measure the photocurrent response of these devices, and find that the photocurrent action spectra follow the quantum-confined absorption spectra of the nanocrystals. For dissimilar top and bottom electrodes, we find that the devices are highly rectifying. By studying space charge limited currents in these devices, we are able to place a lower bound on the effective carrier mobility in such films, and we find that the effective mobility is strongly field dependent. We find that the conductivity is strongly temperature dependent, and is qualitatively consistent with an activated hopping process at temperatures above 180 K.
Synthesis and Raman Spectra of Cupric Oxide Quantum Dots
Authors: Xu J.F. , Ji W. , Shen Z.X. , Tang S.H. , Ye X.R. , Jia D.Z. , Yin X.Q. 
Published: April 2011

ABSTRACTWe have synthesised CuO quantum dots by using a method of one-step solid state reaction under ambient conditions, and investigated them by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman scattering technique. The XRD shows that the sample is composed of single phase CuO with a monoclinic structure. The particle size estimated from the x-ray diffraction peaks is about 12 nm, consistent with the TEM result. The Raman spectra show that there are three Raman peaks at 282, 332 and 618 cm−1, which are much broader and shifted several cm−l to lower frequencies in comparison with those of bulk CuO crystal. The temperature dependence of the Raman spectra in the range 77–873 K is also presented.
Low Temperature Si Dot Thin-Film-Transistor Memory
Authors: Nomoto K. , Gosain D. P. , Noguchi T. , Usui S. , Mori Y. 
Published: April 2011

ABSTRACTWe report a novel poly-Si-thin-film-transistor based memory with Si-nano-crystals (Si dots) floating gate fabricated on a quartz substrate at a temperature below 400°C. Novel techniques of Si-dot and tunnel-oxide formation using excimer laser annealing were performed. A preliminary device shows a threshold voltage shift larger than 1 V with 20 V, 10 ms write/erase (W/E) operation and a retention time of 103 s at room temperature. The device operates 104 W/E cycles without significant degradation.
Size Dependence of Second Harmonic Generation in Cdse Nanocrystals
Authors: Jacobsohn M. , Banin U. 
Published: April 2011

ABSTRACTSecond Harmonic Generation in CdSe nanocrystal quantum dots is observed by Hyper-Rayleigh scattering. We use a Ti-Sapphire femtosecond laser at 820 nm to induce the nonlinear optical response of the nanocrystals in solution. The unit cell normalized second harmonic coefficient βn, shows a substantial systematic enhancement in small sizes. The observed size dependence of the second harmonic generation process, is explained assuming two contributions. The first is a bulk-like contribution, from the non-centrosymmetric nanocrystal core, and the second, a contribution from the particle surface. The latter contribution is most significant in small nanocrystals with a substantial proportion of surface atoms.
Mechanism of the Preferential Edge-Positioning of Self-Organized Ge Quantum Dots on Si Mesas
Authors: Jin G. , Tang Y.S. , Liu J.L. , Thomas S.G. , Wang K.L. 
Published: April 2011

ABSTRACTWe have investigated the preferential positioning of self-organized Ge quantum dots on Si (001) mesas fabricated in a selective epitaxial growth (SEG) mode of gas-source molecular beam epitaxy. The surface morphology was evaluated by atomic force microscopy, and for the Si SEG structures, showed mass accumulation at the periphery. Using micro-Raman spectroscopic imaging, the strain-field distribution of Si structures was studied before Ge deposition, and the results suggest a tensile strain at/near the periphery of the structure while a compressive strain at the center. These structures were subsequently used as a template for Ge dots, which tended to align along the mesa edge. The strain field distribution on Si mesas is speculated to be the driving force for preferential nucleation of Ge dots.
Growth Evolution of (Zn,Cd)Se Quantum Dots Deduced from Spatially Resolved Structural and Optical Characterization
Authors: Leonard K. , Hommel D. , Stockmann A. , Selke H. , Seufert J. , Weigand R. , Bacher G. , Forchel A. 
Published: April 2011

ABSTRACTThe growth mode of CdSe layers grown by migration enhanced epitaxy between ZnSe barriers has been investigated. In situ reflection high-energy electron diffraction shows a gradual transition to a three-dimensional growth mode which, however, is not accompanied by a change of the surface lattice constant. High-resolution transmission electron micrographs reveal a strong Cd diffusion, leading to ternary ZnCdSe quantum wells. Furthermore. composition fluctuations perpendicular to the growth direction on a nanometer scale are found already prior to the beginning of the growth mode transition. In the case of heterostructures containing a CdSe layer that has undergone the growth mode transition, micrographs show Cd-rich quantum dots with diameters of around 8 nm and heights of around 1.5 nm within a ternary quantum well. By spatially resolved photoluminescence the emission from single quantum dots could be observed. The polarization dependence of the emission from single dots indicates an asymmetric shape of the dots with certain preferential orientations along the [110] and [110] directions.
Growth and Microstructure of SrBi2Ta2O9 thin films
Authors: Srinivas S. , Katiyar Ram S. , Kim Won-Jeong , Kircohefer Steven W. , Horwitz James S. , Chrisey Douglas B. 
Published: April 2011

AbstractSingle phase, (001) oriented SrBi2Ta2O9(SBT) thin films have been deposited on (100) MgO substrates using pulsed laser deposition(PLD) technique. In order to study the influence of the growth conditions on the microstructure and stoichiometry, SBT film growth was carried out under different deposition conditions, using an Kr:F excimer laser (248 nm, 30 ns FWHM). Effect of laser fluence(0.75–2 J/cm2), frequency of the laser pulse (4–10 Hz), substrate temperature (700–850°C), oxygen partial pressure(150–450 mTorr) have been studied using X-ray diff-raction(XRD), Scanning Electron Microscope(SEM), X-ray energy dispersive analysis (EDAX), atomic force microscopy(AFM). It was found that small variation in growth temperature and oxygen pressure has a large influence on the average grain size (50–180 nm) and surface roughness (0.14–0.3 nm) respectively. Outgrowths on the film surface were observed at high substrate temperatures, high laser energy and with higher frequencies (>6) of the laser pulse. Highly c-axis oriented SBT thin films with homogeneous surface morphology and with an average surface roughness of 0.14 nm were deposited at 750 °C, 260 mTorr O2 pressure and 1.25 J/cm2 laser fluence. These films have a tangent loss around 0.05 and dielectric constant around 417 with a tunability of 4% in the microwave frequency region (1–20 GHz).
Growth Mechanisms and Surface Morphology of Ybco Based High-Tc Thin Films and Heterostructures for sns Junctions
Authors: Rao R. A. , Eom C. B. 
Published: April 2011

AbstractWe have controlled the nanoscale growth mechanism and surface morphology of YBa2Cu3O7 (YBCO) based high-Tc thin films and heterostructures, using miscut SrTiO3 substrates. On exact (001) SrTiO3 substrates, the YBCO films grow in a screw dislocation growth mode. The barrier layers (La6.4Sr1.6Cu8O20 and PrBa2Cu3O7) grown on top of such a YBCO film also show spiral growth features, indicating pseudomorphic growth. On miscut substrates (with miscut angle ≥ 4° toward [010]) the YBCO films grow by step-flow. However, the La6.4Sr1. 6Cu8O20 layers grown on such YBCO bottom electrodes, show a high degree of step bunching with rough surface. In contrast, the PrBa2Cu3O7 layers show clear step-terrace surface morphology similar to the underlying YBCO bottom electrode, suggesting the existence of periodic nanoscale steps at the S-N interface. These heterostructures can be used for the fabrication of SNS Josephson junctions to take advantage of the proximity effect coupling at the nanoscale steps at the interface.
Low Magnetic Field Response of 2d-Array of Weakly Coupled Ferromagnets
Authors: Ivanov Z. G. , Chakalov R. A. , Claeson T. 
Published: April 2011

AbstractWe demonstrated a low magnetic field response in 2D array of weakly coupled ferromagnets created by bi-epitaxial growth of La0.7Sr0.3MnO3 film on multilayer template of MgO seed and CeO2 buffer layer deposited on SrTiO3 substrate. To form the array we etched the MgO seed layer into a chess board pattern. The chess board fields, where the substrate surface is disclosed, initiate a 45° in-plate rotated growth of the CeO2 buffer layer while it does not rotate on the neighboring fields covered by MgO seed layer. The La0.7Sr0.3MnO3 film inherits the template orientation of the buffer layer forming misoriented at 45° domains and a well defined 2D array of 45° grain boundaries is created. The size of the domains, correspondingly the number of grain boundaries, can be varied by changing the dimensions of the chess board fields. The multilayer structures were investigated by θ–2θ and φ-scan x-ray diffraction. A magnetoresistance of 25% by 0.5 T was measured and ascribed to the properties of the 2D array of grain boundaries.
Dry Etching to form Submicron Features in CMR Oxides: (Pr,Ba,Ca)MnO3 and (La,Sr)MnO3
Authors: Lee K. P. , Jung K. B. , Cho H. , Kumar D. , Pietambaram S. V. , Singh R. K. , Hogan P. H. , Dahmen K. H. , Hahn Y. B. , Pearton S. J. 
Published: April 2011

AbstractEffective pattern transfer into (Pr,Ba,Ca)MnO3 and (La,Sr)MnO3 has been achieved using Cl2/Ar discharges operated under Inductively Coupled Plasma conditions. Etch rates up to 900 Å-min−1 for (La,Sr)MnO3 and 300 Å-min−1 for (Pr,Ba,Ca)MnO3 were obtained, with these rates being a strong function of ion flux, ion energy and ion-to-neutral ratio. The etching is still physically-dominated under all conditions, leading to significant surface smoothing on initially rough samples. Sub-micron (0.35 μm) features have been produced in both materials using SiNx as the mask.
Recent Advances in ab initio time—dependent Hartree-Fock theory and their applications to predict nonlinear optical properties of semiconductor nanoclusters
Authors: Karna Shashi P. , Korambath Prakashan P. 
Published: April 2011

ABSTRACTRecent advancements in ab initio time-dependent Hartree-Fock (TDHF) theory have made it a technique of choice for modeling nanoscale nonlinear optical (NLO) materials from first-principles. We have used this method to study structure-NLO property relationships of GaN, GaP and GaAs clusters. The geometry of the clusters used in the study was optimized by ab initio Hartree Fock (HF) calculations with the use of even tempered Gaussian (ETG) basis set. The clusters used in this study are of the type Gam Xn (M = 1,3,4,7 and n = 1,3,4,7) where X=N, P, and As. The GamXn clusters are in a charge neutral (q = 0) state for m = n and in appropriately charged state for m ∦ n. The magnitude of the calculated (hyper)polarizabilities appears to strongly depend on the composition of the cluster. For the same composition of heteroatoms, the hyperpolarizability depends on the size as well as the geometry of the cluster. The cluster size-dependence of calculated (hyper)polarizabilities is more pronounced for the first-hyperpolarizability. β than for the polarizability, α The calculated β(–ωμ,ωl,ω2) corresponding to various second order effects shows the following trend β(–2ω; ω,ω) > β(–ω; 0, ω) >β(0;0,0).
Subband Structure and Optical Transitions in a Superlattice with Electron Quasi-Localised States in Unit Cell
Authors: Dmitriev A.V. , Makeev V.V. 
Published: April 2011

ABSTRACTWe studied theoretically the electron spectrum and infrared transitions in a superlattice with a unit cell allowing for quasi-localised carrier states. The dispersion relation and the band structure of such a system have been found. We also calculated the dipole matrix element for inter-subband carrier infrared transitions. The wave functions and the electron spectrum in this superlattice show a peculiarity when the energy of a band state approaches the energy of the quasi-localised state in the single cell. In particular, the absorption strength peaks up at the respective frequencies.
Semiempirical Self-Consistent Field Modeling of the Ce+3 4f AND 5d Energy Levels in Solid State Luminescent Materials
Authors: Rack Philip D. , Holloway Paul H. , O'Brien Ted A , Zerner Michael C. 
Published: April 2011

ABSTRACTRare earth doped semiconductors are known to be efficient luminescent materials. In particular, SrS and SrxS and SrxGa2S4 doped with Ce+3 have recently been explored as efficient blue cathodoluminsecent and electroluminescent materials for flat panel display applications. The blue emission in these materials is due to Ce+3 5d-4f transitions, and the transition energies are sensitive to the local chemistry of the Ce+3 ion. To understand the effect that the local chemistry has on the Ce+3 4f–5d emission spectrum, we used a self-consistent-field configuration interaction (SCF/CI) model to calculate the electronic spectrum of the Ce−3 ion embedded in a cluster representation of the semiconductor lattice. The effects of changing nearest neighbor anions and cations have been modeled and are in excellent agreement with the experimental spectroscopy. While vibronic transitions are not calculated in this model, the calculated line transitions were fit to Gaussian peaks to generate absorption and emission spectra. Calculated and experimental Ce3+ 4f–5d emission spectra are compared for different materials, and the observed spectral changes are correlated to an analysis of the magnitude of the ligand field splitting and the nephelauxetic effect in various host lattices. Computed atomic orbital electron populations support these arguments.
Computation of the Porous Silicon Dielectric Function in the Supercell Model and Comparison with Experiment
Authors: Tagüeeña-Martínez J. , Rubo Y.G. , Beltrán M. , Wang C. , Cruz M. 
Published: April 2011

ABSTRACTWe present the results for the imaginary part of the dielectric function of porous silicon, which were obtained with the tight-binding 128–atom supercell model for different porosities. The supercells have been chosen to allow the interconnection of the Si skeleton. We have analyzed also the effects of pore morphology. We have found that, at a fixed porosity, the developing of the surface, resulting in the increase of saturating hydrogen atoms, leads to a noticeable blueshift of the absorption edge.
Polymeric Carbon Dioxide
Authors: Yoo Choong-Shik 
Published: April 2011

ABSTRACTSynthesis of polymeric carbon dioxide has long been of interest to many chemists and materials scientists. Very recently we discovered the polymeric phase of carbon dioxide (called CO2-V) at high pressures and temperatures. Our optical and x-ray results indicate that CO2-V is optically non-linear, generating the second harmonic of Nd: YLF laser at 527 nm and is also likely superhard similar to cubic-boron nitride or diamond. COz-V is made of CO4 tetrahedra, analogous to SiO2 polymorphs, and is quenchable at ambient temperature at pressures above 1 GPa. In this paper, we describe the pressure-induced polymerization of carbon dioxide together with the stability, structure, and mechanical and optical properties of polymeric CO2-V. We also present some implications of polymeric CO2 for high-pressure chemistry and new materials synthesis.
A Method of Incorporating the Composition into the Calculation of the Si Kβ X-ray Emission Spectrum of the SiO2 — CaO Binary Glass with the DV-X α Molecular Orbital Calculation
Authors: Morishita M. , Koyama K. , Kikko T. 
Published: April 2011

ABSTRACTSi KB X-ray emission spectra of SiO2—CaO binary glasses simulated with the DV-X α molecular orbital calculation were compared with ones measured by EPMA. The composition of the glass has been incorporated in the calculation of the Si 3p partial density of states (PDOS). The Si 3p PDOS, as a function of the CaO content, agreed well with the measured Si Kβ X-ray emission spectra of the 62.4mol%SiO2 – 37.6mol%CaO and 43.3mol%SiO2 – 56.7mol%CaO binary glasses. The present method was found to provide a very useful means of clarifying the change in the ionic configuration of the glass with the metal oxide content.