bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined Thermal and UV Growth of Thin Dielectrics on Silicon in an NO Environment
Authors: Jamet Philippe , Tanner Philip , Harrison H. Barry , Dimitrijev Sima
Published: April 2011

The necessity to decrease silicon wafer-processing temperatures substantially has stimulated research into new and innovative techniques for the formation of thin dielectric films. A photo-decomposition technique using Nitric Oxide (NO) is one such promising method. Thermally NO-grown and NO-annealed dielectric films have already shown very encouraging physical and electrical results. This study compares thermally NO-grown oxides with thermally NO grown and assisted by ultraviolet (UV) irradiation. Methods using UV and vacuum UV light generated from low-pressure mercury or deuterium lamps to stimulate the growth of ultrathin dielectric films are described. The oxynitridation of silicon is carried out by irradiating an ultraviolet beam on the heated silicon substrate covered by a thin layer of nitric oxide gas. Typical resultant film thickness were in the range 10 –40 A after oxynitridation for various times at 500°C. MIS devices were fabricated using these films as gate insulators and were electrically characterized. Electrical characterization revealed good film qualities, rendering this new UV-NO oxynitridation technique promising for low temperature (<600°C) semiconductor processing. Films grown in NO ambient under deuterium lamp irradiation followed by NO annealing were also investigated. These results will also be presented.
Experimental Observations of the Redistribution of Implanted Nitrogen at the Si-SiO2 Interface During RTA Processing
Authors: Lysaght Patrick S. , Nguyen Billy , Bennett Joe , Williamson Gary , Torres Kenneth , Gilmer Mark , Luo Tien-Ying , Brady David , Guan Jay , Brown George A. , Zeitzoff Peter , Bersuker Gennadi , Mucha Jay , Geyling Franz , Gebara Gabriel , Vishnubhotla Lucky , Jackson Michael D. , Huff Howard R.
Published: April 2011

The redistribution of nitrogen from silicon to the Si-SiO2 interface due to thermal processing is investigated by Secondary Ion Mass Spectroscopy (SIMS) using Metal-Oxide-Semiconductor (MOS) capacitors. SIMS profiles of implanted atomic nitrogen concentration indicate a significant redistribution of the nitrogen, from the silicon to the oxide layer in response to variations of the steady state time and temperature parameters of Rapid Thermal Anneal (RTA) processing. RTA treatment, in N2 ambient, over a temperature range of 750°C - 1100°C, results in a measured increase of the integrated nitrogen peak at the interface. High Frequency Capacitance Voltage (HFCV) measurements of an implanted (N/ 5 × 1014 cm2/s / 26keV) and annealed (900°C / 10s) sample is compared with a control (without N implant) sample to determine the relative nitrogen abundance at the interface. This value corresponds to the increase in fixed oxide charge Q that produces a negative shift in the flat band voltage Vo under negative gate bias conditions.
Decaborane as Ion Source Material for Boron Implantation
Authors: Sosnowski Marek , Gurudath Ravidath , Poate John , Mujsce Anthony , Jacobson Dale
Published: April 2011

Formation of p-type shallow junctions for future generations of Si technology will require ion implantation of B at very low energies, i.e. below 1 keV, where the beam formation and transport at reasonably high currents are hindered by Coulomb repulsion of ions at high volume density. An alternative to implantation of monomer ions at a very low energy is implantation of large molecular ions at a higher energy. In the latter case, the implantation depth of the atoms corresponds to a fraction of the beam energy, partitioned between the atoms of the molecule. The decaborane molecule (B10H14) is of particular interest for implantation of p-type shallow junction in Si, because each of the B atoms carries only 9% of the molecule's kinetic energy. Experimental PMOS devices made using decaborane implantation have been demonstrated recently. It also has been shown that transient enhanced diffusion (TED) of B in Si implanted with B ions and with decaborane ions at the equivalent dose and energy are the same. The prospect for using decaborane in ion sources is examined, based on measurements of its ionization and dissociation properties. It is shown that decaborane molecules are effectively ionized by electron impact in the energy range near 100 eV.
In Situ, Real-Time Studies of Film Growth Processes Using Ion Scattering and Direct Recoil Spectroscopy Techniques
Authors: Smentkowskiv V.S. , Krauss A. R. , Auciello O. , Im J. , Gruen D.M. , Holecek J. , Waters K. , Schultz J. A.
Published: April 2011

Time-of-flight ion scattering and recoil spectroscopy (TOF-ISARS) enables the characterization of the composition and structure of surfaces with 1–2 monolayer specificity. It will be shown that surface analysis is possible at ambient pressures greater than 3 mTorr using TOF-ISARS techniques; allowing for real-time, in situ studies of film growth processes. TOF-ISARS comprises three analytical techniques: ion scattering spectroscopy (ISS), which detects the backscattered primary ion beam; direct recoil spectroscopy (DRS), which detects the surface species recoiled into the forward scattering direction; and mass spectroscopy of recoiled ions (MSRI), which is a variant of DRS capable of isotopic resolution for all surface species - including H and He. The advantages and limitations of each of these techniques will be discussed.

The use of the three TOF-ISARS methods for real-time, in situ film growth studies at high ambient pressures will be illustrated. It will be shown that MSRI analysis is possible during sputter deposition. It will be also be demonstrated that the analyzer used for MSRI can also be used for time of flight secondary ion mass spectroscopy (TOF-SIMS) under high vacuum conditions. The use of a single analyzer to perform the complimentary surface analytical techniques of MSRI and SIMS is unique. The dual functionality of the MSRI analyzer provides surface information not obtained when either MSRI or SIMS is used independently.
On the Diffusivity of Au in Pb
Authors: Campbell Ann N. , Turnbull David
Published: April 2011

The precipitation of Pb3Au from dilute Pb(Au) alloys and the subsequent Ostwald ripening of the precipitate phase have been studied. The Au diffusivity which limits the precipitation from Pb(500 at. ppm Au) specimens is in good agreement with Dp = 45 exp[(−20.8 kcal/mol)/RT], found previously to control the precipitation rate in Pb(900–1000 at. ppm Au) alloys (Rossolimo and Turnbull, 1973). In contrast, precipitation from Pb(100 at. ppm Au) alloys and Ostwald ripening in the Pb(500 at. ppm Au) specimens appear to be governed by the high temperature Au tracer diffusivity, DAu = 0.0041 exp[(−9.35 kcal/mol)/RT], which is about 103 times greater than Dp at the temperatures of interest, 75 to 112°C, and is attributed to the motion of a Au interstitial defect. In the 100 ppm alloys the Au is incorporated most easily at the ends of the Pb3Au crystals and a ribbon- or whisker-like morphology results. The particles which form at the grain boundaries in the 500 ppm Au alloy specimens are at least six times larger in volume than the matrix particles and ripen at their expense. The Ostwald ripening kinetics of the grain boundary particles scale with t1/2 rather than with t1/3 as is usual. The Pb3Au formed whiskers, blades, ribbons, or equiaxed particles depending upon the Au concentration and precipitation temperature. The precipitation and ripening kinetics are critically dependent on the morphology of the second phase.
Amorphous Ni-Zr Phase Formation in Self-Supporting Thin-Film Lateral-Diffusion Couples
Authors: Barbour J. C. , Mayer J. W.
Published: April 2011

The formation of an amorphous Ni-Zr alloy, by heating to cause interdiffusion in the temperature range 250°C to 325°C, was demonstrated in a self-supporting lateral-diffusion couple. Micro-area diffraction in a scanning transmission electron microscope (STEM) indicates that microcrystalline ordering in the amorphous phase must be on a scale less than 5 nm. The samples were heated in a vacuum furnace to form the amorphous phase and later heated in the STEM for in situ observation of crystalline compoundformation. The amorphous to crystalline transformation occurs first in theZr-rich regions at 370°C. A crystalline phase begins to consume the Ni rich amorphous material, at 450° C; but at 325° C, the amorphous phase is stable up to 20.5 hours, even in the presence of crystalline compounds.
Transformation Kinetics for Crystalline, Quasicrystalline, and Glassy Alloys in the Binary Al100-xMnx and Pseudobinary Al84-ySiyMn16Systems
Authors: Bagley B. G. , Chent H. S.
Published: April 2011

The condensed state phase transition energetics and kinetics are reported for specific compositions within the Al-Si-Mn system which demonstrate crystal → crystal, quasicrystal→ crystal, and glass.→crystal structural transformations. Our observations, and their interpretation, for the solid state crystalline AI(Mn)→Al+Al6 Mn reaction and the crystallization of glassy Al54Si 30Mn16 are consistent with the anticipated mode for these transformations. The nature of the quasicrystal→ crystal transformation, consistent with our observations, is an enigma.
Precipitation Kinetics in Metastable Solid Solutions – Theoretical Considerations and Application to Cu-Ti Alloys
Authors: Kampmann R. , Eckerlebe H. , Wagner R.
Published: April 2011

Cu-2.9 at.% Ti single crystals were homogenized at various temperatures (780 °C ≤ TH ≤ 960°C) and quenched. Subsequent isothermal aging at 350 °C led to phase separation, the kinetics of which have been followed by employing small-angle neutron scattering (SANS). According to comple-mentary transmission electron and analytical field ion microscopy studies, the resulting transformation products of this first order phase transition are stoichiometrically ordered ellipsoidal Cu4Ti particles, the aspect ratio of which changes with aging time (t) as revealed by two-dimensional SANS-detection. In the early stages of phase separation, the decomposition kinet-ics are strongly influenced by the quenching rate via quenched-in excess vacancies. During aging the structure factor S(K,t) develops a maximum, the height (Sm) of which increases and the position (Km) of which decreases with t. Neither Sm(t) nor Km(t) follow a power law as predicted by several recent theories on spinodal decomposition. On the other hand, the time evolution of the mean Ti-rich cluster size (R), their number density (Nv), and the supersaturation (Δc) as inferred from the SANS-data and the diffuse Laue-scattering, are well predicted by a precipitation model which describes nucleation, growth and coarsening as competing processes.
Superheating of Metallic Crystals
Authors: Däges J. , Gleiter H. , Perepezko J. H.
Published: April 2011

For crystals that melt into fluid liquids, superheating of the solid has been detected in only a few cases. In these cases, a crystal was subjected to focused heating in the center. Under a high thermal gradient some interior superheating was possible, but usually only a few degrees or less. A new approach is reported for preparing samples which can exhibit superheating under more uniform thermal conditions. To exclude the vapor from contact with the crystal a continuous coating is developed with a melting temperature in excess of that for the pure core crystal. For single crystal spherical Ag samples with a diameter of about 130 μm the free surface was coated with a continuous higher melting point layer of Au to inhibit surface initiated melting of silver at its melting point. The coated Ag crystals were observed to exhibit superheating of at least 7.5 K above the melting point of pure Ag for time periods of the order of one minute. Under the experimental conditions used, internal stresses could be excluded as the reason for the observed increase in the melting onset temperature of Ag. The superheating duration is related to the interdiffusion between the coating layer and the core crystal. Some microstructural observations and electron microprobe composition scans also relate to the observed superheating behavior. The results seem to disagree with lattice stability models of melting and may open the way to the study of crystals in the metastable superheated state.
Near-Field Optical Imaging of Electromigration Damages in Passivated Metal Stripes
Authors: Bonera E. , Borghesi A. , Caprile C.
Published: April 2011

Electromigration is one of the main failure mechanisms limiting the miniaturization of microelectronic devices. As a consequence of the high current densities in the interconnections, hillocks and voids are formed and their evolution can modify the electrical performances of devices till failure. To characterize electromigration damages,. today's failure analysis techniques require removal of the protection passivation to allow scanning electron microscope or focused ion beam microscope imaging, but the removal process itself can damage the surface of the metal stripes. Due to the optical transparency of the passivation, near-field scanning optical microscopy can be used to overcome this problem. We succeeded in obtaining the first near-field images in resolution < 150 nm of electromigration-damaged metal structures without complete removal of the passivation. The latter was thinned to 100 – 200 nm to allow the evanescent waves to reach the metal structures and illuminate a subwavelength zone of the sample. Near-field images show the presence of hillocks and voids of dimensions down to 250 nm which can be due only to electrornigration, and, in this sense, they are more reliable than the usual scanning electron microscope images.
Fabrication and Characterization of 2D and 3D Ordered Arrays of Nanoparticles
Authors: Gates Byron , Zhong Ziyi , Xia Younan
Published: April 2011

Two methods are presented which have been successfully used to fabricate highly ordered 2D and 3D arrays of nano-scale particles. The first method uses a combination of microcontact printing (μCP) and surface-templated reactions to form 2D patterned arrays of nanoparticles on silicon substrates. The second method uses confined self-assembly to crystallize colloidal particles into 3D cubic-close-packed (ccp) arrays (or opaline structures).
Lateral Transport through Self-Assembled InAs Quantum Dots Located in the Narrow Gap Electrodes
Authors: Jung S. K. , Hwang S. W. , Park J. H. , Min B. D. , Kim E. K. , Kim Yong
Published: April 2011

We have fabricated and characterized the lateral electron transport through InAs quantum dots with double barrier system. Aluminum metal electrodes with the inter-electrode spacing of 30 nm have been deposited on an InAs self-assembled quantum dot wafer to form the planar type quantum dot devices. Current peak structure and negative differential resistance effects are observed above 77 K in current-voltage characteristics. These results are interpreted as due to 3D-0D resonant tunneling through the single quantum dot positioned in between the electrodes.
1.3 μm InAs/GaAs Quantum Dot Led
Authors: Childs D. , Malik S. , Siverns P. , Roberts C. , Murray R.
Published: April 2011

We have determined the growth conditions which result in a narrow linewidth and room temperature emission at 1.3pm from InAs/GaAs Quantum dots (QDs). The QDs formed under these conditions are extremely uniform in size and exhibit an emission linewidth of only 25meV. Single QD layers have been incorporated into p-i-n diodes which exhibit strong electroluminescence. We have compared the efficiency of these devices with a nominally identical quantum well device. The QD based device exhibits a higher electroluminescence efficiency, especially at low current densities. At higher current densities there is a loss of efficiency due to recombination from excited states.

Operated under reverse bias, the diodes act as photo-detectors and the measured photocurrent spectrum exhibits peaks due to absorption in the ground and excited states of the QDs as well as the 2D confining layer.
Properties of Ion Beam Synthesized Iron Disilicide Dots
Authors: Galli M. , Marabelli F. , Pagetti A. , Grimaldi M.G. , Coffay S. , Spinella C. , Miglio L.
Published: April 2011

Semiconducting iron silicide dots with dimensions ranging between 5 and 100 nm can be obtained by ion implantation on Si wafers and exhibit interesting photo- and electro- luminescent properties.

In our study we use structural and optical characterization as well as theoretical modelling in order to: i) discriminate among intrinsic effects of FeSi2 dots and effects due to lattice damage and Si matrix; ii) identify the range of physical parameters (size, phase, electronic structure) corresponding to the luminescent dots.
Three Dimensional Finite Element Simulations of Vertical Dot Correlation in Quantum Dot Superlattice
Authors: Zhang Y.W.
Published: April 2011

A three dimensional finite element method is used to simulate the kinetic process of island formation in quantum dot superlattices. Depending on the thickness of spacer layers and interruption time, top layer islands can be fully vertically aligned with the same morphology as the buried islands, or can be partially vertically aligned with increasingly less uniform and regular arrangement, or can be alternately misaligned with increasingly uniform and regular arrangement.
Preparation and Optical Properties of Ge and C-Induced Ge Quantum Dots on Si
Authors: Eberl K. , Schmidt O. G. , Kienzle O. , Ernst F.
Published: April 2011

Pure Ge epitaxially grown on Si (100) at high temperatures forms typically 100 nm lateral size islands on top of a 3–4 monolayer thick wetting layer. In stacked layers of Ge dots pronounced vertical alignment is observed if the thickness of the Si spacer layers is smaller than about 50 nm. Pregrowth of a small amount of C on Si substrate induces very small 10 nm size Ge quantum dots after deposition of about 2 to 3 monolayers Ge. Photoluminescence (PL) studies indicate a spatially indirect radiative recombination mechanism with the no-phonon line strongly dominating. Strong confinement shift in the 1–2 nm high and 1Onm lateral size dots results in low activation energies of 30 meV, which causes luminescence quenching above 50K.

For large stacked Ge islands with 13 nm thin Si spacer layers we observe a significantly enhanced Ge dot-related PL signal up to room temperature at 1.55μm wave length. This is attributed to a spatially indirect transition between heavy holes confined within the compressively strained Ge dots and two-fold degenerated A state electrons in the tensile strained Si between the Ge stacked dots.
Preparation of Nanocrystalline Silicon Quantum Dots by Pulsed Plasma Processes with High Deposition Rates
Authors: Nishiguchi K. , Hara S. , Amano T. , Hatatani S. , Oda S.
Published: April 2011

A new method for the fabrication of nanocrystalline silicon (nc-Si) in SiH4plasma with very-highfrequency (VHF; 144MHz) excitation is proposed to increase the deposition rate, to control the size, and to minimize size dispersion of nc-Si. Nanocrystalline silicon is formed in the gas phase of the SiH4plasma cell by coalescence of radicals. Supplying Ar enhances the nucleation of nc-Si because of high efficiency of SiH4excitation into SiH2radicals resulting in the nucleation. The deposition rate is thus increased by a factor of 100 to 1012/cm2.h. At the low flow rate of SiH4, smaller nc-Si with small dispersion is obtained. Moreover, when pulsed-SiH4is supplied into Ar plasma, the growth of nuclei is limited by the time when SiH4flows. The size of nc-Si and its dispersion are adjusted by the duration of SiH4gas pulse.
Colloidal Synthesis and Properties of InAs/InP and InAs/CdSe Core/Shell Nanocrystals
Authors: Cao Yun-Wei , Aksenton Julia , Soloviev Victor , Banin Uri
Published: April 2011

High-temperature colloidal synthesis of InAs/InP and InAs/CdSe core/shell nanocrystal quantum dots is reported. InP and CdSe shells with several thicknesses were grown on InAs cores ranging in diameter between 20 to 50 Å. Optical spectra, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to analyze the core/shell quantum dots and determine their chemical composition, average size, size distributions, and structures. The experimental results indicate that shell growth is uniform, expitaxial, and controllable. For both InP and CdSe shells, growth is accompanied by a red shift of the band gap energy as a result of the extension of the electron wavefunction into the shell region. An increase of the room temperature photoluminescence quantum yield by a factor of∼4 is observed with CdSe shell growth on InAs Cores. The growth of InP shells, however, quenches the photoluminescence quantum yield. The difference is assigned to outer surface effects in core/shell nanocrystals.
Reservoir Layers in High Tc Mercury Cuprates
Authors: Geballe T. H. , Moyzhes Boris Y. , Dicktnson P. H.
Published: April 2011

We put forward the hypothesis that cations with 6s electrons (Hg,Tl,Pb,Bi) in the charge reservoir layers of high Tc cuprate superconductors actively participate in the pairing interaction as negative-U centers. We further argue that the Hg-cuprates are outstanding superconductors (Tc > 160 K) because they can exist as two-ion negative-U centers, . Their electrons are less localized than in single-site centers (negative-U or bipolaron) and can have a strong pairing interaction with a smaller increase in effective mass. The centers are oriented in the x and y directions and can have phase differences compatible with the d-wave symmetry of the CuO2 planes.
Mott Transition Field Effect Transistor: Experimental Results
Authors: Schrott A. G. , Misewich J. A. , Scott B. A. , Gupta A. , Newns D. M. , Abraham D.
Published: April 2011

In this paper we describe the fabrication of oxide based devices similar in architecture to a conventional FET with source, drain, and gate electrodes and a channel. This distinctive characteristic of our device is the use of a channel material capable of undergoing a field-induced Mott insulator-metal transition at room temperature. Lithographic techniques developed for oxide materials have been combined with pulsed laser deposition of perovskite materials onto single-crystal strontium titanate (STO) substrates to fabricate these devices. Materials chosen for the Mott transition channel include La2CuO4 (LCO) and YBCO, p-type; and Nd2CuO4, n-type.
Inspection and Manipulation of Ferroelectrics on the Nanometer Scale
Authors: Eng L. M.
Published: April 2011

The increasing interest in scanning probe instruments (SPM) stems from the outstanding possibilities in measuring electric, magnetic, optical, and structural properties of surfaces and surface layers down to the molecular and atomic scale. For the inspection of ferroelectric materials both the scanning force microscope (SFM) and the scanning near-field optical microscope (SNOM) are promising techniques revealing information on the polarization vector and the electric field induced stress within a crystal. Polarization sensitive modes are discussed as is friction force microscopy, dynamic force microscopy (DFM) and voltage modulated SFM. From these measurements, 180° domain walls (c-domains) are resolved down to 4 nm, while 3-dimensional polarization mapping in ferroelectric BaTiO3 ceramics reveals a 25 nm resolution. On the other hand, non-contact DFM measurements in ultra-high vacuum are able to resolve ferroelectric surfaces down to the atomic scale. Then also the chemical heterogeneity at the sample surface is differentiated from ferroelectric domains down to a 5 nm lateral resolution, taking advantage of the short range chemical forces. SNOM in contrast probes the optical properties of ferroelectric crystals both in transmission and reflection. Here image contrast arises from changes in the refractive index between different domains as well as at domain walls. In addition, SPM instruments are used for the local modification of ferroic samples by applying a relatively high voltage pulse to the SPM tip. Domains with diameters down to 30 nm are thus created with the size depending on both the switching and material parameters.
Correlated Magnetoexcitons in Semiconductor Quantum Dots at Finite Temperature
Authors: Dean D.J. , Strayer M.R. , Wells J.C.
Published: April 2011

We describe computational methods for the theoretical study of explicit correlations beyond the mean field in excitons confined in semiconductor quantum dots in terms of the Auxiliary-Field Monte Carlo (AFMC) method [1]. Using AFMC, the many-body problem is formulated as a Feynman path integral at finite temperatures and evaluated to numerical precision. This approach is ideally suited for implementation on high-performance parallel computers. Our strategy is to generate a set of mean-field states via the Hartree-Fock method for use as a basis for the AFMC calculations. We present preliminary results.
Nonlocal Polarizabilities and the AB Initio Calculation of Surface Optical Properties of Gaas (110)
Authors: Wijers C.M.J. , De Boeij P.L.
Published: April 2011

We have calculated the reflectance anisotropy for the GaAs (110) surface using the discrete cellular method. This method extends the range of application of standard discrete dipole calculations by incorporating nonlocal polarizabilitites. The method adds a second quantum mechanical channel of nonlocality, which turns out to be necessary and yields very good agreement between theory and experiment.
Effect of Fe on Sintering of Al2O3-MgO-Fe2O3 Spinel
Authors: Kharissova O.V. , Aguilar J.A. , Ortiz U.
Published: April 2011

The influence of Fe on the microstructure of Al2O3-MgO-Fe2O3 spinel is described in this work. Heating a mixture of initial oxides in an electric furnace at 1400°C for 15 hrs produced the spinel. A ternary diagram for concentration ranges: Al2O3 (5-75 mol%), MgO (10-80 mol%), and Fe2O3 (3-70 mol%) summarize the constitution of this spinel. Amount, composition and weight ratios of each phase were determined by X-rays powder diffraction.

Microstructure of specimens was characterized by scanning electronic microscopy and Xray spectrometry. Distribution, size, shape of phases and pores were examined. Hardness measurements of spinel completed this study.
Phase Separation and Elastic Fields: Three Dimensional Simulations of a Phase Field Model
Authors: Orlikowski Daniel , Sagui Celeste , Somoza Andrds , Roland Christopher
Published: April 2011

The effects of long-range elastic fields on the phase separation process of three- dimensional binary alloy systems was investigated with large-scale Langevin simulations. The elastic effects incorporated in the model are the result of anisotropy and dilational misfits introduced via inhomogeneities in the elastic constants of the constituents. The domain morphology obtained is readily understandable in terms of selection criterion for the shape and/or orientation of the domains, and is based on the different shear moduli that are present in the system. Coarsening mechanisms were found to be a combination of the classical Ostwald ripening mechanism and the elastically-driven coalescence of domains. Other aspects of the coarsening process such as dynamic scaling of the structure function is presented.
Microdynamic Mechanisms of Crystal Growth Under Applied Electric Fields
Authors: Jiao Y.N. , Takamori S. , Ohsawa Y. , Arakane G. , Sato A.
Published: April 2011

On the basis of the model of atomic cluster jump theory, a microdynamical model of crystal growth rate was developed under an electric field. Theoretical analysis indicates that the crystal growth rate is dependent on not only the nature of the metal, the undercooling and so on but also the applied electric fields. Moreover, a novel model, which shows the effect of an applied electric field on the solute distribution, the constitutional undercooling and the temperature distribution at solid/liquid interface during unidirectional solidification, has been established theoretically. Analytical results show that the electrotransport of solute strongly influences the solute distribution and then changes the constitutional undercooling and the temperature distribution. But all changes are connected with the electric current direction of the applied electric field (positive or negative).
Growth of Lamellar Products During Discontinuous Solid State Reactions
Authors: Zieba P. , Gust W.
Published: April 2011

The nucleation, growth and dissolution of lamellar precipitates formed due to discontinuous solid state reactions like: discontinuous precipitation, coarsening and dissolution, are reviewed. Emphasis is given on recent studies based on analytical electron microscopy in describing the microchemistry, andin situelectron microscopy for revealing the morphological features of the reactions.
Formation and Evolution of Three Dimensional Structures in the Cu/Sn/Si(111) System
Authors: Hu Qin , Mitchell I. V. , Zinke-Allmang M.
Published: April 2011

Copper is a prevalent contaminant in silicon device fabrication. Since Cu has high solubility in Sn, we are exploring the use of Sn to form Cu-Sn surface alloys as a means to inhibit Cu diffusion into Si substrates. Cu/Sn/Si (111) samples were prepared by MBE at 100°C, then annealed at temperatures between 300°C and 600°C. Resultant surface structures were imaged by AFM and SEM. AES and EDX were used to investigate the composition of two differently shaped clusters that formed after annealing. Etching with dilute HCI solutions was used to seek the chemical origin of various surface morphologies. The results are compared with those from Sn/Si and Cu/Si samples. A possible model for the evolution of 3-D structures in the Cu/Sn/Si(111) system will be presented.
Ion-Enhanced Dry Etching of Magnetic Multilayers: Post-Etch Cleaning and Effects of UV Illumination
Authors: Cho H. , Lee K. P. , Jung K. B. , Sharifi F. , Marburger J. , Pearton S. J.
Published: April 2011

Patterning of magnetic multilayer structures of the type used for MRAMs (e.g. NiFeCo/CoFe/Cu/CoFe/NiFeCo) is generally performed with ion milling, but this can degrade the coercivity of small (micron-size) MRAM elements and lead to sidewall redeposition. In high ion density reactive plasmas (Cl2/Ar) it is possible to produce ion-enhanced desorption of otherwise involatile halogenated reaction products, and achieve practical etch rates (∼600 Å/min) for the multilayers. However, removal of the chlorinated etch products from the feature sidewalls is critically important to avoid corrosion. We have used de-ionized water rinsing or in-situ exposure to H2, O2 or SF6 plasmas for removal of these etch residues. Some slight degradation in magnetization was observed in O2 plasma treated structures, but the other cleaning procedures produced no change in magnetic properties and excellent long-term stability. UV illumination of the sample surface during etching is also found to enhance etch rates, as has been reported previously for room temperature etching of Cu.[1]
Kev Ion Beam Induced Surface Modification of Sic Hydrogen Sensor
Authors: Muntele C. I. , Ila D. , Williams E. K. , Poker D. B. , Hensley D. K.
Published: April 2011

Silicon carbide, a wide-bandgap semiconductor, is currently used to fabricate an efficient high temperature hydrogen sensor. When a palladium coating is applied on the exposed surface of silicon carbide, the chemical reaction between palladium and hydrogen produces a detectable change in the surface chemical potential. Rather than applying a palladium film, we have implanted palladium ions into the silicon face of 6H, n-type SiC samples. The implantation energies and fluences, as well as the results obtained by monitoring the current through the sample in the presence of hydrogen are included below. The exposure to hydrogen of this kind of sensor while monitoring the current flow with respect to time, has revealed a completely different behavior than the samples that have Pd deposited as a surface layer.
Modeling Metal Thin Film Growth under IPVD Conditions using Molecular Dynamics Rates in a Level Set Approach
Authors: Hansen U. , Rodgers S. , Nemirovskaya M. , Jensen K. F.
Published: April 2011

We present a recently developed method for modeling ionized physical vapor deposition. Using molecular dynamics techniques we examine the surface adsorption, reflection and sputter reactions taking place during ionized physical vapor deposition. We predict their relative probabilities and combine the information obtained from molecular dynamics into a transport model incorporating all effects of re-emission and re-sputtering. This provides a complete growth rate model that allows the inclusion of energy and angular dependent surface reaction rates. As an example, the method is applied to growth of an aluminum film under different deposition conditions.
Novel Defects and Anisotropic Vacancy Diffusion on Reconstructed Surfaces
Authors: De La Fuente O. Rodríguez , González M. A. , Rojo J. M.
Published: April 2011

STM and molecular dynamics simulations are used to study Au(001) 5×25 reconstructed surfaces after Ar+ bombardment at 600 eV and ion doses from 0.05 to 1 ML+. Surface 2D dislocation dipoles, identified as such in a previous investigation, are shown to have dislocation properties and to be formed by anisotropic diffusion of surface vacancies along the ridges of the reconstructed topmost layer. A new vacancy diffusion mechanism involving intermediate states with de-localized vacancies is identified. Increasing ion fluences is shown to lead to the formation of vacancy islands that are nucleated at the dislocation dipoles.
Microcharacterization of Heterogeneous Specimens Containing Tire Dust
Authors: Camatini Marina , Corbetta GAI M , Crosta Giovanini F , Dolukhanyan Tigran , Giuiani Giampaolo , Sung Changmo
Published: April 2011

This work is focused on dust or debris produced by the wear of tire tread. Two problems are addressed, which are solved by analytical electron microscopy (AEM): characterization of tire debris and identification of tire debris particles in a heterogeneous specimen. The characteristic morphology, microstructure and elemental composition of tire debris can all be determined by AEM. The scanning electron microscope (SEM) shows that the surface of a tire debris particle has a typical, warped structure with pores. The characteristic elements of tire rubber are S and Zn, which are detected by energy dispersive X ray (EDX) spectroscopy. The identification of rubber particles in heterogeneous debris containing talc and produced by a laboratory abrader is possible by the analytical SEM. Transmission electron microscope images, EDX spectra and selected area electron diffraction patterns characterize tire debris at the sub–micron scale, where the material can no longer be treated as homogeneous.
Microdiffraction, EDS, and HREM Investigation for Phase Identification With the Electron Microscope
Authors: Ruterana P. , Redjaïmia A.
Published: April 2011

Abstract: For micro or nanophase identification, the ideal method is electron microscopy which combines experimental technique and theoretical analysis in order to solve the problem which is typical in non homogeneous materials. In this work, two heterogeneous materials have been investigated: a Fe- 22Cr - 5Ni -0.3Mo - 0.03C (wt%) duplex stainless steel and a 6H-SiC reinforced Al-Cu alloy fabricated by the Ospray technique followed by extrusion and aging. This aging often gives rise to the precipitation of intermetallic compounds some of which can be new phases. Using microdiffraction, EDS and HREM, it was possible to identify two new phases: the orhorhombic τ phase in the heat treated duplex steel and the tetragonal Al7Cu3Zr2 in the reinforced aluminium copper alloy
A New Approach Towards Property Nanomeasurements Using In Situ TEM
Authors: Wang Z.L. , Poncharal P. , De Heer W.A. , Gao R.P.
Published: April 2011

Property characterization of nanomaterials is challenged by the small size of the structure because of the difficulties in manipulation. Here we demonstrate a novel approach that allows a direct measurement of the mechancial and electrical properties of individual nanotube-like structures by in-situ transmission electron microscopy (TEM). The technique is powerful in a way that it can directly correlate the atomic-scale microstructure of the carbon nanotube with its physical properties, providing an one-to-one correspondence in structure-property characterization. Applications of the technique will be demonstrated on mechanical properties, the electron field emission and the ballistic quantum conductance in individual nanotubes. A nanobalance technique is demonstrated that can be applied to measure the mass of a single tiny particle as light as 22 fg (1 f= 10−15).
Ion-Implanted Amorphous Silicon Studied by Variable Coherence TEM
Authors: Cheng J-Y. , Gibson J. M. , Voyles P. M. , Treacy M. M. J. , Jacobson D. C.
Published: April 2011

Amorphous silicon formed by ion-implantation of crystalline silicon is investigated with the use of VC-TEM (variable-coherence transmission electron microscopy). This technique is sensitive to medium-range-order structures. The results from high-energy Si implanted samples showed a striking similarity to sputtered amorphous silicon. We found that both ion-implanted and sputtered samples have paracrystalline structures, rather than the expected continuous random network (CRN). We also observed the structural relaxation of the ion-implanted amorphous silicon after ex-situ thermal annealing towards the random network. The more disordered structures are favored and a large heat of relaxation is released as the temperature increases. Finally, we show some preliminary results on the structural variation with the sample depth.
Investigating Atomic Scale Phenomena at Materials Interfaces With Correlated Techniques in STEM/TEM
Authors: Browning N. D. , Nicholls A. W. , James E. M. , Arslan I. , Xin Y. , Kishida K. , Stemmer S.
Published: April 2011

A complete understanding of the complexities behind the structure-property relationships at materials interfaces requires the structure, composition and bonding to be characterized on the fundamental atomic scale. This level of characterization is beyond the scope of a single imaging or microanalysis technique and so to solve practical interface problems, correlation between multiple techniques must be achieved. Here we describe recent advances in the JEOL 2010F 200kV field-emission STEM/TEM that now allow atomic resolution imaging and analysis to be obtained in both TEM and STEM mode and discuss two applications of these techniques
Characterization of Intergranular Phases in Doped Zirconia Polycrystals
Authors: Evans N. D. , Imamura P. H. , Bentley J. , Mecartney M. L.
Published: April 2011

Analytical electron microscopy at high spatial resolution in a scanning-transmission mode has been used to investigate the effects of glassy or crystalline material additions on grain boundary chemistry in yttria-stabilized zirconia polycrystals. Powders of additive phase were mixed into 3-mol% yttria-stabilized tetragonal zirconia polycrystals (‘3Y-TZP’) or 8-mol% yttria-stabilized cubic zirconia polycrystals (‘8Y-CSZ’). Zirconias processed without additive phases were also examined

Without additives, grain boundaries were depleted in zirconium and enriched in yttrium. In 3Y-TZP with I wt% borosilicate glass, silicon was observed only at triple points, but not in grain boundaries. In 3Y-TZP with 1 wt% barium silicate glass, barium was observed both along grain boundaries and at triple points, whereas silicon was detected only within the triple points. This suggests either the composition of the additive phase at the grain boundary is different from that at the triple points, or that barium ions segregate to grain boundaries during processing. In 8Y-CSZ with I wt% silica, silicon was observed in grain boundaries by an EDS spatial differencing technique. In 8Y-CSZ with 10 wt% alumina, EDS revealed aluminum at all grain boundaries examined
Electron Backscatter Diffraction: A Powerful Tool for Phase Identification in the SEM
Authors: Michael J. R. , Goehner R. P.
Published: April 2011

EBSD in the SEM has been developed into a tool that can provide identification of unknown crystalline phases with a spatial resolution that is better than one micrometer. This technique has been applied to a wide range of materials. Use of the HOLZ rings in the EBSD patterns has enabled the reduced unit cell to be determined from unindexed EBSD patterns. This paper introduces EBSD for phase identification and illustrates the technique with examples from metal joining and particle analysis. Reduced unit cell determination from EBSD patterns is then discussed.
Controlled Environment Transmission Electron Microscopy
Authors: Robertson I. M.
Published: April 2011

The basic design features of a controlled environment transmission electron microscope and the details of the one at the University of Illinois are described. Examples of how this instrument has been used to determine fundamental mechanisms of hydrogen embrittlement in metals are presented.
Analysis of the Atomic Scale Defect Chemistry in Oxygen Deficient Materials by STEM
Authors: Ito Y. , Stemmer S. , Klie R. F. , Browning N. D. , Sane A. , Mazanec T. J.
Published: April 2011

The high mobility of anion vacancies in oxygen deficient perovskite type materials makes these ceramics potential candidates for oxygen separation membranes. As a preliminary investigation of the defect chemistry in these oxides, we show here the analysis of SrCoO3−σ using atomic resolution Z-contrast imaging and electron energy loss spectroscopy in the scanning transmission electron microscope. In particular, after being subjected to oxidation/reduction cycles at high temperatures we find the formation of ordered microdomains with the brownmillerite structure.
Resonance Raman Scattering of Multi-Walled Carbon Nanotubes
Authors: Kataura H. , Achiba Y , Zhao X. , Ando Y
Published: April 2011

Multi-walled carbon nanotubes synthesized by the carbon arc in hydrogen gas have very thin core channels. We have measured resonance Raman scattering of some samples synthesized in different conditions, and have observed radial breathing mode (RBM) peaks from 200 to 500 cm−1. Resonance effect of each peak is similar to that of single-walled nanotube. However, the peak frequencies are about 5 % higher than those of single-walled nanotubes, which is probably due to the inter-layer interaction. Further, the highest RBM peak splits in three peaks. The result on the resonance effect and the zone-folding band calculation suggest that the thinnest core nanotube is (4,3) that have four candidates of second outer nanotubes. This suggests that the different outer nanotube gives different degree of the interlayer interaction.
Electronic Properties of Potassium-Doped Carbon Nanotube Lattice
Authors: Saito Susumu
Published: April 2011

We study the electronic structure of potassium-doped crystalline lattice of so-called (10.10) carbon nanotubes in the framework of the density-finctional theory. Tie stoichiometrv of the material studied is K2C80 which was originally proposed in designing the superconducting doped nanotube material based on tile size of dopants and the charge transfer being favorable for superconductivity. Electronic band dispersions obtained are actually found to be very similar to those of the pristine (10,10) nanotube lattice with the upward shift of the Fermi energy by 1 eV above the second conduction-band miinimum. Tie system therefore possesses higher Fermi-level density of states than the pristine material with rather sinmple charge transfer from K to C sites, and is confirned to be a good candidate for a naxiotube superconductor.
Molecular Dynamics Simulations of Polymer-Nanotube Composites
Authors: Frankland S. J. V. , Brenner D. W.
Published: April 2011

The structure and mechanical properties of nanocomposites composed of (10,10) carbon nanotubes in an amorphous polyethylene matrix have been modeled with molecular dynamics simulations. Two systems were studied, an infinite nanotube (via periodic boundaries) and a finite capped nanotube 6 nm in length. In the infinite case the modulus in the direction of the nanotube is given by the upper bound of the rule of mixtures, as expected under isostrain conditions for a well-aligned fiber-reinforced composite. In the finite case, no load transfer is observed at low strain, consistent with the weak nanotube-polymer adhesion and a subcritical nanotube length. The simulations predict that regions of amorphous polymer close to the bulk density remain around the nanotubes at relatively large strains, and that the density decrease during strain results primarily from chain disentanglement and alignment in regions between nanotubes.
Low Threshold Field Emission From Nanocluster Carbon Films
Authors: Milne W.I. , Satyanarayana B.S. , Robertson J.
Published: April 2011

Carbon films with variable sp3/sp2 bonding ratio can be deposited on a variety of substrates at room temperature, using the cathodic vacuum arc deposition process. The variation in their surface morphology as a function of He and N2partial pressure during growth have been investigated and it has been shown that the morphology of the films can be varied from the mirror like smooth tetrahedrally bonded carbon (ta-C) films through nanocluster to fibrous type carbon. This paper reviews the work carried out on Field Emission from these various carbon films. Threshold fields as low as 1 V/μm for emission current densities of 1 μA/cm2 and emission site densities of up to 104 -105/cm2 have been obtained.
Low Temperature Growth of Ultra-Nanocrystalline Diamond on Glass Substrates for Field Emission Applications
Authors: Corrigan T. D. , Krauss A. R. , Gruen D. M. , Auciello O. , Chang R. P. H.
Published: April 2011

Recent studies of field emission from diamond have focused on the feasibility of growing diamond films on glass substrates, which are the preferred choice for cost-effective, large area flat panel displays. However, diamond growth on glass requires temperatures < 500 °C, which is much lower than the temperature needed for growing conventional microwave plasma chemical vapor deposition (CVD) diamond films. In addition, it is desirable to minimize the deposition time for cost-effective processing. We have grown ultrananocrystalline diamond (UNCD) films using a unique microwave plasma technique that involves CH4-Ar gas mixtures, as opposed to the conventional CH4-H2 plasma CVD method. The growth species in the CH4-Ar CVD method are C2 dimers, resulting in lower activation energies and consequently the ability to grow diamond at lower temperatures than conventional CVD diamond processes. For the work discussed here, the UNCD films were grown with plasma-enhanced chemical vapor deposition (PECVD) at low temperatures on glass substrates coated with Ti thin films. The turn-on field was as low as 3 V/μm for a film grown at 500 °C with a gas chemistry of l%CH4/99%Ar at 100 Torr, and 7 V/μm for a film grown at 350 °C. UV Raman spectroscopy revealed the presence of high quality diamond in the films.
Rapid Photo-Thermal Chemical Vapor Deposition of Amorphous Carbon From Diiodomethane
Authors: Lindstam M. , Boman M. , Piglmayer K.
Published: April 2011

A novel approach to deposit amorphous carbon from the precursor CH2I2 at low cost and high efficiency is reported. The combination of thermal and quantum photo effects shows new interesting growth behaviour. The radiation of a halogen-lamp was used to heat the substrate material and to split photolytically the precursor molecules above the substrate surface. The deposition process was investigated as a function of lamp power, gas phase partial pressures and substrate materials. The films were analysed by Raman spectroscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray photon spectroscopy, transmission electron microscopy and atomic force microscopy.