bluuebunny/crossref_metadata_2025 huggingface dataset:
High-k Dielectrics and Dual Metal Gates: Integration Issues for New CMOS Materials
Authors: Claflin B. , Flock K. , Lucovsky G.
Published: April 2011

Several metal and conducting metal nitride candidates were investigated for alternative gate electrode applications in future complimentary metal-oxide-semiconductor (CMOS) devices. High frequency capacitance-voltage (CV) measurements were performed on n-MOS and p-MOS capacitors with Al, Ta, TaN, TIN, or W2N gates and ultra-thin SiO2/Si3N4 dielectric stacks. The work functions of Al and Ta were close to the conduction band of Si as expected while all the metal nitrides had work functions slightly above mid-gap. The thermal stability of the metal nitrides and the metal/dielectric interfaces was studied by Auger electron spectroscopy (AES) following rapid thermal annealing (RTA). Integration requirements for dual metal gate electrodes in future CMOS devices are discussed.
Atomistic Simulations of Damage Evolution in Silicon
Authors: Buneat Marius M. , Fastenko Pavel , Dunham Scott T.
Published: April 2011

We have studied the damage annealing process using kinetic lattice Monte Carlo (KLMC) and molecular dynamics (MD) with initial damage distribution from Monte Carlo ion implant simulations. MD calculations find a long range interstitial vacancy interaction, as also seen in previous tight-binding molecular dynamics (TBMD) simulations.1 The influence of the long range interaction as well as the initial spatial correlations present in the implant damage are then analyzed with KLMC in the form of corrections to the +1 model. We find that both long range interactions and the initial spatial correlations are significant at low doses, while the effects disappear at high doses.
Sub-Nm Screening Layer Approach for Ultra Shallow Junction Formation
Authors: Hori M. , Miyake T. , Hikazutani K. , Kataoka Y. , Nakamura M. , Wada T. , Kase M.
Published: April 2011

This paper describes the influence of the sub-nm screening and capping oxide layer of wet process on B diffusion for 50 nm shallow junction formation. The reason is proposed that the knock-on oxygen into Si makes B diffusion faster such as in the case of oxidation enhanced diffusion. To suppress the B enhanced diffusion, the screening oxide formed before implant should be thin to reduce the knock-on oxygen. The wet process before annealing strongly influences the B diffusion, in particular, thicker capping oxide with sub-oxide structure and knock-on oxygen has an important rule for the enhanced diffusion.
Effect of the oxidation of a silicide layer on dopant diffusion in the underlying silicon
Authors: Kappius L. , Tyagi A. K. , Breuer U. , Bay H. L. , Manti S.
Published: April 2011

We have studied the influence of an epitaxial silicide layer on the diffusion of B and Sb in silicon. B and Sb doping superlattices have been grown by molecular beam epitaxy. They were then covered with a 20 nm thick CoSi2 layer. Test samples were also grown without silicide. Samples were oxidized at various temperatures ranging from 800°C to 1200°C for times that ensured sufficient broadening of the spikes. Another set of samples was annealed at the same times and temperatures in N2. Dopant depth profiles were measured before and after diffusion by secondary ion mass spectrometry (SIMS). At the test samples we observed thermal diffusion of B and Sb, oxidation enhanced diffusion of B and oxidation retarded diffusion of Sb, all in accordance with the literature. In contrast to this, oxidized silicide capped samples showed a retardation of B diffusion by a factor of 2 - 10 as compared to thermal diffusivity and an enhancement of Sb diffusion by a factor of 1 - 2.
Phosphorus Diffusion From Doped Si1−xGex, Films into Silicon
Authors: Kobayashi S. , Iizuka M. , Aoki T. , Mikoshiba N. , Sakuraba M. , Matsuura T. , Murota J.
Published: April 2011

Phosphorus diffusion from in-situ doped Si1−xGex epitaxial films into Si at 800°C was investigated using secondary ion mass spectroscopy and differential resistance measurements. The surface P concentration in the diffused layer in Si was higher than the P concentration in the Si1−xGex, film in the present conditions, which signifies the segregation of P from the Si1−xGex, film into Si. The segregation coefficient, defined as the ratio of the active P concentration in the Si to that in the Si1−xGex, film, was about 2.5 in the case of the Si0.75Ge0.25 film as a diffusion source and increased with increasing Ge fraction. The P diffusion profiles in Si were normalized by x/√, even though the segregation of P occurred. The high concentration diffusion characteristics of P in Si were similar to those reported by using conventional diffusion sources.
Fabrication of Shallow Junctions with Conventional Furnace Equipment by Using Silicon Preimplants
Authors: Puchner H. , Aronowitz S.
Published: April 2011

The global scaling down of device dimensions requires process technologies which are able to create ultra-shallow junctions. Besides using ultra-low implant energies for shallow junction creation we present an alternative approach for the creation of MDD (Medium Doped Drain) junctions by using moderately low implant energies. Our approach employs the dopant/point-defect interaction mechanism to retard dopant diffusion as well as dopant de-activation in the tail of the diffusion profiles to achieve suitable shallow junctions. The silicon preimplant allows fabrication of 90nm arsenic, 150nm phosphorus, and 140nm boron metallurgical junctions for a 40keV arsenic, 20keV phosphorus, and 8keV boron implant.
Real Time Characterization of Non-Ideal Surfaces and Thin Film Growth by Advanced Ellipsometric Spectroscopies
Authors: Collins R. W. , Rovira P. I. , Ferlauto A. S. , Koh Joohyun , An Ilsin , Zapien J. A. , Messier R. , Wronski C. R.
Published: April 2011

The development of multichannel ellipsometers with photodiode array-based detection systems has enabled real time spectroscopic ellipsometry (SE), a technique now being used widely to study surface modification and thin film growth. Multichannel ellipsometers based on the rotating-element design acquire spectroscopic data in parallel and thus offer advantages over other designs. The simplest rotating-element multichannel ellipsometers are constructed using a rotating polarizer or analyzer for polarization state modulation or detection. These configurations have a number of drawbacks, in particular, their insensitivity when measuring samples that reflect linearly polarized light and their susceptibility to errors when measuring samples having unrecognized non-idealities (e.g., macroscopic inhomogeneities) that generate a mixture of polarization states in the reflected beam. In this review, we describe recent advances in multichannel ellipsometry including (i) enhancement of the spectral range of the rotating-polarizer multichannel ellipsometer to 1.5–6.5 eV, (ii) adaptation of the rotating-compensator configuration to multichannel ellipsometry for studies of weakly absorbing and macroscopically inhomogeneous materials, and (iii) development of a dual rotating-compensator multichannel ellipsometer design for real time studies of optically anisotropic materials. As a recent example of the application of rotating-compensator multichannel ellipsometry, we describe analyses of (i) a macroscopically-rough (textured) tin-oxide (Sno2) film on a glass substrate and (ii) the fabrication of the p-layer component of an amorphous silicon-based p-i-n solar cell on the textured SnO2 film surface at a temperature of 200°C.
In Situ Spectroscopic Ellipsometry Studies of The Interaction Process of Ethene With Si Surfaces During Sic Formation
Authors: Wöhner T. , Stauden Th. , Cimalla V. , Eichhorn G. , Schaefer J.A. , Pezoldt J.
Published: April 2011

The interaction of ethene with silicon (111) surfaces at different process temperatures (580°C, 680°C, 780°C) was monitored in situ by spectroscopic ellipsometry. It is shown that spectroscopic ellipsometry is a reliable method to monitor the carbonization process of silicon surfaces. Different SiC formation stages (incubation time, (√3×√3)R30° reconstruction, 2D growth and 3D growth) were observed using complimentary analyzing techniques. The change of the ellipsometric signal as a function of process time is related to these stages and was interpreted using an optical model which consists of four layers (surface roughness, SiC layer, interface layer, Si substrate).
Crystal Nucleation and Growth in Glassy and Liquid Pd40Ni40P20
Authors: Evans P. V. , Garcia-Escorial A. , Donovan P. E. , Greer A. L.
Published: April 2011

Turnbull pointed out that good glass formability should correlate with a high reduced glass transition temperature, Trg. The alloy Pd40Ni40P20 has an unusually high Trg of ∼0.66 and indeed it can be formed into a glass at rather low cooling rates (≲ 1 Ks−1 ). In this paper a number of experiments are described which take advantage of the high resistance to crystallization in this alloy to study behavior in the labile temperature range between Tg and Tm. The anomalously low crystal growth velocities arise because the product is a three phase mixture. Nucleation kinetics are derived from crystal size distribution analysis. Heterogeneous nucleation at the surface of melt spun ribbon is characterized; significant surface relief develops on crystallization because of the low number of nuclei. In bulk glass produced by fluxing, good crystal size statistics show that internal nucleation is predominantly also heterogeneous, but with a significant transient time. Measurements of the specific heat of the undercooled liquid reveal that the free energy of crystallization deviates significantly from a linear dependence on undercooling (expected for pure metals) in the way predicted by Dubey and Ramachandrarao.
The Importance of Transient Nucleation and Non-Equilibrium Viscosity for Glass Formation
Authors: Kelton Kenneth F.
Published: April 2011

The process of nucleation and growth in glasses and undercooled liquids is modeled by directly simulating the evolution of the molecular cluster distribution under both isothermal and non-isothermal conditions. Results of that simulation for the nucleation rate during the quench, and for the number of nuclei produced and the volume fraction transformed at the end of the quench are presented. The following three points are discussed: (1) The importance of transient, or non-steady state, nucleation rates on glass formation is assessed by considering three model glass forming systems: lithium disilicate, a relatively good glass former, and two metallic glasses, (Au85Cu15)77Si9Gd14 and Au81Si19. (2) Using experimentally determined values for the steady state nucleation rates and growth velocities for Pd40Ni40P20, it is demonstrated that, in agreement with recent experimental results, this alloy may be cycled at rates on the order of 1 K/sec between the melting and glass transition temperatures without crystallization. Transient effects are shown to be unimportant under these conditions in this system. (3) The effect on glass formation of a non-equilibrium viscosity during the quench due to configurational freezing is evaluated by assuming a phenomenological model for the changing viscosity.
Amorphous Alloys from Microsecond Current Pulses
Authors: Clemens Bruce M. , Buchholz Jeffrey C. , Gilgenbach Ronald M. , Bidwell Steven
Published: April 2011

We report the use of microsecond current pulses to produce an amorphous metal alloy. Starting materials consisted of electron beam deposited films of elemental crystalline zirconium and nickel layers with a composition modulation wavelength of 46 nm, a total thickness of about 2.5 μn, and an average composition of Zr38Ni62 deposited onto sapphire substrates. Current pulses had a total ring time of several microseconds and were produced with a low inductance capacitor and a spark gap switch. Integration of current traces showed that 85% of the energy was deposited into the sample within 2 microseconds. The energy in the pulses could be controlled in a range where their effect on the films went from no visible change to total vaporization. Pulses with a peak current in the kiloampere range produced melting in 1 cm wide samples. The cooling rate following this treatment was sufficient to produce amorphous material. We report structural changes resulting from rapid melting and resolidification as well as results of a search for solid state transformations resulting from current pulses below the melting threshold.
The Emergence of Modern Nucleation Theory
Authors: Cahn John W.
Published: April 2011

A series of important papers by David Turnbull and his collaborators in the late 1940's and early 1950's laid the experimental and theoretical foundation of modern nucleation theory. The elegance, versatility, and generality of the phenomenological approach, coupled with brilliant and insightful experimental confirmation, sparked widespread application which continues today. Much of David Turnbull's subsequent work in other subjects grew directly or indirectly from this work.
Crystal Growth Mechanisms and Kinetics
Authors: Glicksman M. E. , Selleck M. E.
Published: April 2011

The scientific contributions by David Turnbull and his co-workers toward understanding crystal growth span over 35 years from the late 1940's to the present. Turnbull's early attempt (1950) to correlate interfacial energies derived from droplet supercooling measurements with other thermochemical data still provides a significant data base for estimating such energies in a variety of materials. His work with Hillig in 1956 on quantification of the screw dislocation mechanism for interfacial molecular attachment remains as a predictive theory for defect-assisted growth of faceted, and therefore kinetically hindered, interfaces. The Hillig-Turnbull screw dislocation mechanism is now ranked among such notable kinetic models for crystal growth as the Wilson-Frenkel random attachment theory and the nucleationlimited layer spreading models of Burton, Cabrera, and Frank. Turnbull's contributions and interest in elucidating crystal growth kinetics have continued throughout his long and productive career, as evidenced by his recent work with Coriell (1982) on estimates of collision limited rapid crystal growth in highly supercooled transition metals. Progress in unraveling the kinetic contributions of interfacial attachment from those of heat and solute transport will also be reviewed to provide a current context of Professor Turnbuli's contributions to the field of rapid crystallization.
Self-Assembled InAs Islands on (AI,Ga)As, an In Situ Scanning Tunneling Microscopy Study
Authors: Ballet P. , Smathers J.B. , Salamo G.J.
Published: April 2011

We report an in-situ molecular beam epitaxy – scanning tunneling microscopy study of three dimensional (3D) self organized InAs islands on (AI,Ga)As surfaces. The influence of the presence of Al atoms on the roughness of the starting surface and on the island density is shown by investigating several Al compositions. We emphasize the case of InAs/AlAs and point out the major differences between this system and the widely studied InAs/GaAs system.
Stress-Driven Formation of Self-Assembled InGaAs Islands on Sub-Micron Metal-Patterned Substrate
Authors: Son Maeng Ho , Jung S. K. , Min Byung Don , Hyun Chan Kyung , Choi Bum Ho , Kim Eun Kyu , Kim Yong , Lim Jong Soo
Published: April 2011

A stress-driven formation of self-assembled InGaAs islands has been studied by the growth on GaAs (100) substrates with sub-micron platinum stripe pattern. Islands or quantum dots preferentially nucleate at the boundary of metal patterns. In addition, a quantum dot-free region near the boundary of the metal pattern is found. Those results are attributed to the stress between metal stripe and GaAs surface, which produces a laterally stressed region around the metal stripe. Adatoms on this region preferentially migrate toward the edge of metal stripes with maximum stress. This result may show a possible way for the interconnection between randomly distributed self-assembled quantum dots and metal stripes.
Quantum Confined Electron-Hole States in ZnSe Quantum Dots
Authors: Lee H. W. H. , Smith C. A. , Leppert V. J. , Risbud S. H.
Published: April 2011

We observed the quantum confined bandedge emission from ZnSe quantum dots and the size dependence of the energy states, spin-orbit interaction, and Stokes shift. The bandedge emission occurs in the UV-blue. The energy gap = Eg + C/dn where d is the diameter and n is 1. 19 ± 0.13 and 1.21 ± 0.13 for the first and second electron-hole transitions, respectively. The separation between these transitions approaches the bulk spin-orbit splitting, while the Stokes shift decreases with particle size. Effective mass theories can not explain these results. Trap emission is observed in some samples in the green and red, resulting from Se-related traps.
Manipulating InAs Dots with GaAs Patterns: Effect of GaAs Buffer Layer Growth and Pattern Profiles
Authors: Jeppesen Søren , Gerling Maria , Samuelson Lars , Miller Mark S.
Published: April 2011

We report on our efforts to selectively place chemical beam epitaxy grown Stranski-Krastanov InAs dots on GaAs patterns. The pattern profiles for placement depends on the growth conditions of a GaAs buffer layer grown on the lithographic patterns. Because we seek to suppress dot formation on (100)-oriented surfaces outside of the features, we investigated the effects buffer layer growth conditions have on dot nucleation using reflected high energy electron diffraction, atomic force microscopy and photo-luminescence. We conclude that buffer conditions favorable for patterns have negligible effect on the dots formed on the (100)- oriented surface, and that selective dot placement can be engineered by As pressure, InAs deposition and buffer growth conditions.
Intraband Absorption in Ge/Si Self-Assembled Quantum Dots
Authors: Boucaud P. , Le Thanh V. , Sauvage S. , Brunhes T. , Fortuna F. , Debarre D. , Bouchier D.
Published: April 2011

Mid-infrared intraband absorption in Ge/Si self-assembled quantum dots is reported. The self-assembled quantum dots are grown by ultra-high-vacuum chemical vapor deposition. The intraband absorption is observed using a photoinduced absorption technique. The mid-infrared absorption, which is in-plane polarized, is maximum around 300 meV. The absorption is attributed to a quantum dot hole transition between bound and continuum states. The absorption cross section is deduced from the saturation of the photoinduced intraband absorption. An inplane absorption cross section as large as 2 × 10−13 cm2 is measured for one dot plane.
First Principles Investigation of Multiferroism in Perovskite Manganites
Authors: Hill Nicola A. , Rabe Karin M.
Published: April 2011

We present results of first principles calculations which indicate the simultaneous occurrence of ferromagnetism and ferroelectricity in perovskite structure bismuth manganite, BiMnO3.
Inverse Magnetoresistance In Manganite/SrTiO3/Co Tunnel Junctions
Authors: Teresa J. M. De , Barthélémy A. , Contour J. P. , Fert A. , Lyonnet R. , Montaigne F. , Vaurès A. , Seneor P.
Published: April 2011

In La0.7Sr0.3MnO3/SrTiO3/Co tunnel junctions, the half-metallic nature of La0.7Sr0.3MnO3 allows probing the spin polarization of Co. For applied voltage bias around zero volts, an inverse tunnel magnetoresistance is found, indicating the negative spin polarization of Co at the Fermi level as expected from the density of states of the “d” band in Co. The bias dependence of the magnetoresistance reflects the structure of the “d” band density of states of Co. In this article we underline the important consequences for the knowledge of the spin-dependent tunneling in solids brought by these results and describe in detail the effect of temperature and high magnetic field on the magnetoresistance.
Detailed C-V Analysis for YbMnO3/Y2O3/Si Structure
Authors: Yoshimura Takeshi , Fujimura Norifumi , Ito Daisuke , Ito Taichiro
Published: April 2011

YbMnO3 (Yb/Mn = 0.96) thin films were prepared on Y2O3(111)/Si(111). Although the sample exhibited ferroelectric type C-V hysteresis, the window width changed depending on the applied bias voltage. Hence, the ferroelectric type hysteresis might include the effect of space charge. To make clear the C-V behavior caused by only ferroelectricity, and to obtain the optimal relationship between ferroelectric and insulator layer thicknesses, the C-V behavior at high frequency was computed for MFIS structure. Relationships between the counter bias voltage applied to the ferroelectric layer and the thickness of dielectric layer were also demonstrated. Compared with the calculated results, experimental C-V characteristics are discussed.
Energy Dispersion Contour Approach to Calculate Optical Properties of Quantum Well Structures
Authors: Osotchan T. , Shi W. , Zhang D.H.
Published: April 2011

In order to calculate optical properties i.e. dielectric function, refractive index and absorption coefficient, the evaluation of integration including ground and excited wavefunctions is required over entire k-space. The contour of energy dispersion was proposed to form the criteria to select and limit the value of k in the integration. With the contour approach the integration can be determined to truncate at certain k value where the weight factor of Fermi-Dirac distribution function become very small and the fraction of integration can be ignored. The approach was applied to AIGaAs/AlAs/GaAs double barrier quantum well structures with 14-band k.P Hamiltonian. By systematically modifing this quantum well structure the dependence of absorption peak width was investigated in bound-to-bound and bound-to-quasibound intersubband transitions. The energy dispersion contours of each involved state were illustrated in two dimensional k-space including the compositions in perpendicular and parallel directions to the interface. The calculated refractive index and absorption as a function of wavelength can be simply extracted from the contour characteristic especially at the constant Fermi energy surface.
Optical Properties of Silicon Nanocrystals: A First Principles Study
Authors: Ögüt Serdar , Chelikowsky James R. , Louie Steven G.
Published: April 2011

Ab initio quasiparticle gaps. self-energy corrections. exciton Coulomb energies. and optical gaps of Si nanocrystals are calculated using the higher-order finite difference psendopotential method. The calculations are performed in real space on hydrogen-passivated Si clusters with diameters up to 30 A (> 1000 atoins). The size-dependent self-enerkgy correction is enhanced substantially compared to bulk. and quantum confinement and reduced electronic screening result in appreciable excitonic Coulomb energies. Calculated optical gaps are in very good agreement with absorption data from Si nanocrystals.
Ab Initio Calculations of Response Properties Including the Electron-Hole Interaction
Authors: Olevano Valerio , Albrecht Stefan , Reining Lucia
Published: April 2011

We discuss the current status of a computational approach which allows to evaluate the dielectric matrix, and hence electronic excitations like optical properties, including local field and excitonic effects. We introduce a recent numerical development which greatly reduces the use of memory in such type of calculations, and hence eliminates one of the bottlenecks for the application to complex systems. We present recent applications of the method, focusing our interest on insulating oxides.
Selective Aluminum CVD on Si(100) From DMAH
Authors: Bisch C. , Rogge S. , Mélin T. , Janssen G.C.A.M.
Published: April 2011

The influence of the dose on the crystal growth and on the selectivity of the Al-CVD process has been studied. Doses were varied from 100 L to 18000 L. Selective deposition was observed, both on passivated Si vs. SiO2, as well as on bare Si vs. passivated Si. On oxide elongated crystals have been deposited with dimensions of 1200 × 60 × 60 nm.
Nucleation and Growth In Martensitic Transformations
Authors: Pond R.C. , Nixon T.
Published: April 2011

A mechanistic model of the nucleation and growth of martensitic products that is consistent with the phenomenological theory of martensite crystallography is described, and applied to the case of NiTi. In addition to the lattice invariant deformation specified in the phenomenological theory, an array of interfacial transformation dislocations, or disconnections, is present. The motion of these disconnections across the interface between the nucleus and matrix cause the growth of the precipitate, and the two defect arrays in combination relieve the strain in the nucleus. For such processes to be diffusionless, special crystallographic circumstances must arise, and these are explored in the paper.
3D Simulation of Coarsening of γ′ Precipitates in a Ni-Al Alloy
Authors: Vaithyanathan V. , Chen L.Q.
Published: April 2011

Precipitation of γ′ particles from a disordered γ matrix in a Ni-Al alloy is studied. A continuum phase-field model is employed in three-dimension(3D). The focus is on the evolution of γ′ particle morphology and development of spatial correlations during coherent nucleation, growth and coarsening. The effect of lattice mismatch on the rate of coarsening is investigated. The results are compared with those obtained from two-dimension(2D) simulations.
In Situ Ellipsometry Study of the Diamond Film Evolution Process
Authors: Cancel L.M. , Figueroa O.L. , Weiner B.R. , Morell G.
Published: April 2011

We employed in situ ellipsometry to monitor and study the nucleation and growth processes of diamond thin films fabricated by chemical vapor deposition. The films were grown on Si substrates in a hot filament chemical vapor deposition (HFCVD) system. We monitored the effective extinction coefficient (k) at 1.96 eV of the diamond films during growth through ellipsometry. The behavior of this parameter was found to be reproducible, making it suitable as a basis for dividing the deposition process into intervals. The film growth was aborted at various k values yielding diamond film samples that represent snapshots of the growth process at different stages. These films were removed for ex situ characterization using Raman spectroscopy and scanning electron microscopy (SEM). These characterizations were used to correlate the ellipsometric data with film microstructure, enabling us from now on to monitor the diamond film growth in real time and to design experiments targeted at modifying the film microstructure by changing growth parameters in the middle of film fabrication.
The Effects of Nucleation in the Two Step Growth of HVPE GaN
Authors: Tavernier P.R. , Etzkorn E.V. , Wang Y. , Clarke D.R.
Published: April 2011

The repeatable growth of high quality thick layers of GaN by hydride vapor phase epitaxy generally requires buffer layers or other surface pretreatments to produce morphologically smooth films suitable for further device growth. Of the conditions for high quality GaN growth, proper film nucleation invariably contributes most to the overall growth of high quality films and the exclusion of impurities. We have studied a two step growth process which incorporates a low temperature HVPE grown nucleation layer and have compared it to films grown without buffer layers to determine how the impurity content and the dislocation networks change the overall film quality. Additionally we observe the formation of macroscopic steps during growth with step heights of ∼0.75 μm and terrace widths of ∼ 7 μm, which we attribute to the initial conditions of the low temperature nucleation layer prior to growth and to kinetically limited growth.
Nucleation in Undercooled Co-Pd Alloys
Authors: Holland-Moritz D. , Schenk Th. , Herlach D.M.
Published: April 2011

The statistics of nucleation are studied for different Co-Pd alloys by electromagnetic levitation. Each alloy was undercooled approximately 100 times under the same experimental conditions. A model developed by Skripov is employed to statistically analyze the distribution of maximum undercoolings in order to obtain information on the prevailing nucleation mechanism. The results of these investigations indicate that nucleation is influenced by magnetism when the nucleation temperature is approaching the Curie temperature.
Stochastic Modeling of Grain Growth and Coarsening
Authors: Pande C.S. , Masumura R.A.
Published: April 2011

Recent developments in the modeling of grain growth and coarsening are briefly considered. Common characteristics of both these phenomena are briefly pointed out. A formulation based on stochastic consideration is proposed. This formulation assumes that the rate of growth of an individual grain or a precipitate is not entirely determined by its size but has a random component to it. This leads to a Fokker-Planck Equation for the size distribution. It can then be shown that there is indeed a unique state (the self-similar state) which is in general reached from an arbitrary initial state. The case of two dimensional grain growth is treated in detail as an example. Grain size distribution is obtained from these considerations, which is in good agreement with experiments.
Interdiffusion Microstructure Map Topology
Authors: Morral J. E. , Chen Huimi , Meisenkothen Frederick
Published: April 2011

When two alloys are placed in contact to form a diffusion couple, the microstructure that forms on heating is a function of alloy composition. This function can be illustrated on a phase diagram as an “Interdiffusion Microstructure Map” (IMM). An IMM was determined in the present work for Ni-Cr-Al diffusion couples at 1200°C. The couples consisted of one γ+γ' alloy bonded to a number of γ+β alloys. The IMM contained five fields corresponding to five different microstructures. The fields met at a five-line node, giving the map an unexpected topology. The IMM topology was deduced by considering the transition microstructures and kinetic equations that lead to the formation of interdiffusion microstructures.
Early Stages of Decomposition in Ni-Rich Ni-Ti
Authors: Kompatscher M. , Demé B. , Hecht J. , Heinrich H. , Kohlbrecher J. , Schneider J.-M. , Schönfeld B. , Kostorz G.
Published: April 2011

In-situ small-angle neutron scattering was performed on Ni-(10 to 12) at.% Ti polycrystals and single crystals at temperatures between 870 and 1270 K. During decomposition metastable precipitates of cuboidal shape form with preferred alignement along <100>. The Ti concentration of these precipitates is 17(1) at.% (between 870 and 950 K). Metastable precipitates precede the formation of platelets of the stable η phase even outside the hitherto accepted metastable miscibility gap.
Phase Transition and Pattern of Self-Organized Microstructures in Presence of Mobile Impurities
Authors: Ivanova K. , Ausloos M.
Published: April 2011

A growth model starting from a surface and in presence of mobile nonreactive localized impurities has been studied for the statistical physics of the microstructure and the surface roughness through simulation. The model is based on the Eden model. The microstructure is described at the mesoscopic (particle) scale level. A dynamical repulsion effect on the front with the mobile particles has been investigated numerically. The presence of such mobile particles shifts the usual percolation transition for three-dimensional (3D) systems from 0.65 corresponding to static hindrances, to the value of 0.8. The particle pushing leads to an aggregation phenomenon with self-organizing particles near and after the interface. This leads to the formation of front facets, competition between faces of different orientations and surface roughening.
Eutectoid Decomposition in Three Ti-Co Alloys
Authors: Coomber E. , Whiting M. J. , Tsakiropoulos P.
Published: April 2011

The mechanisms of eutectoid decomposition are important because of the widespread use of alloys which exhibit a eutectoid transformation. However, the transformation remains a matter of controversy for a number of reasons. The Ti-Co system is examined in order to test current understanding of eutectoid decomposition.

The high temperature beta phase can transform on cooling into several products - alpha plates, a non-lamellar mixture of alpha and Ti2Co which can be designated bainite, lamellar pearlite, spheroidal pearlite and Ti2Co allotriomorphs. In this study the high temperature beta phase was decomposed in hypoeutectoid, eutectoid and hypereutectoid alloys, for a range of undercoolings. The microstructure and crystallography of the transformation products was characterised by reflected light microscopy, SEM, XRD and TEM. The classification of the transformation products is discussed.
Improvement of Tft Characteristics by Using Controlled Grains
Authors: Takeuchi F. , Suga K. , Mishima Y. , Sasaki N.
Published: April 2011

We fabricated TFTs on a glass substrate using poly-Si films crystallized by an excimer laser with a SiO2 capping pattern placed exactly on the channel regions. This process greatly improves the uniformity of the TFT characteristics compared to conventional excimer laser-crystallized poly-Si TFTs, because the capping pattern controls nucleation and produces grains that are aligned along the capping pattern. However, the average mobility produced by the capping method is not as good as that produced by the conventional method. This study clarified that a thermal gradient can control grain structure and is effective in achieving uniformity, and that the maximum temperature of molten Si must be increased to obtain higher mobility.
A Possible Production Technique for Modulation Doped Sige Heterostructures
Authors: Rosenblad C. , Kummer M. , Müller E. , Hackbarth T. , Känel H. Von
Published: April 2011

The SiGe graded buffer layer is one of the most promising virtual substrates for future Si based high speed devices. The production of the SiGe buffer layer is, however, hampered by the time consumed by the synthesis of the several μm thick epitaxial layer. Low energy plasma enhanced chemical vapour deposition (LEPECVD) is a growth technique developed for low temperature epitaxy at high rates. Here we study the possibility to combine LEP-ECVD for graded SiGe buffer layer growth with other techniques for the growth of the electrically active layer.
Study of Strain Relaxation in Epitaxial Structure Ge0.2 Si0.8/Si At Thermo-Implantation Treatment by Ion Beam Channeling
Authors: Vyatkin A. F. , Egorov V. K. , Egorov E. V.
Published: April 2011

Strain relaxation in epitaxial Si-Ge structures induced by ion beam bombardment has been studied using a He+ channeling technique. It is shown that hot ion beam bombardment (230°C, Si+ ions with energy 200 keV and fluence 6·1013 ion/cm2) of thin strained Si-Ge layers results in partial strain relaxation. A model of the strain relaxation induced by radiation damage
is proposed.
Study of Low-Energy Ion Assisted Epitaxy of Gan Films: Influence of the Initial Growth Rate
Authors: Gerlach J. W. , Schrupp D. , Schwertberger R. , Rauschenbach B. , Anders A.
Published: April 2011

The deposition of thin epitaxial hexagonal gallium nitride films on c-plane sapphire by low-energy nitrogen ion assisted deposition is shown to result in films of high crystalline quality. The quality can be further heightened by using the concept of an isothermal growth rate ramp. Characterization of film structure, defect density distribution and surface topography by XRD, RBS/C, and AFM, respectively, reveals the importance of the nitrogen ion energy and the ion to atom ratio on the film properties.
Biaxially Textured Buffer Layers on Large-Area Polycrystalline Substrates
Authors: Dzick J. , Sievers S. , Hoffmann J. , Thiele K. , Garcia-Moreno F. , Usoskin A. , Jooss C. , Freyhardt H. C.
Published: April 2011

Biaxially textured yttria stabilized zirconia (YSZ) buffer layers were deposited on long polycrystalline metallic tapes by an ion-beam-assisted deposition process (IBAD) to serve as templates for high-current carrying Y1Ba2Cu3O7-x (YBCO) films. YSZ was deposited by a dualionbeam equipment with two 11 cm Kaufman ion sources. The coating of large-area technical substrates, large in comparison with the ion sources, requires substrate movements to render YSZ films of homogeneous texture quality. These movements can hinder cooling of the metallic tapes in the absence of a thermal contact. Therefore, the temperature of those small-heat-capacity substrates could rise to above 100 °C within minutes, causing a decrease of the in-plane alignment of YSZ. The investigation of the temperature dependence of the IBAD process reveals that the best results of the in-plane alignment could be obtained by room temperature deposition. Applying high tape velocities hinder a rise of the deposition temperature to above 90 °C. Therefore, it is possible to deposit YSZ films on metal tapes (up to 60 mm × 1000 mm) with in-plane textures down to 15° full width at half maximum (FWHM), which allow their coating with highcurrent-carrying YBCO films.
Microstructural Evolution of Ion Bombarded Copper Thin Films
Authors: Wagner T. , Müller D.
Published: April 2011

The effect of low-energy ion bombardment on the microstructure of copper films will be described. The copper films have been deposited on SiNx-coated, oxidized Si wafers by magnetron sputtering with a simultaneous bombardment of low-energy argon ions (60 eV). The films were annealed at 450°C in HV. The ion bombardment leads to a stronger and sharper {111} texture of the as-deposited films. After annealing, the ion-bombarded films had a significantly smaller grain size than films produced without ion bombardment. The experimental results will be discussed relating the textures of the as-deposited films with the grain sizes obtained after annealing. Details will be given describing how the microstructure of Cu films can be tailored using low-energy argon ion bombardment.
Electron Channeling X-ray Microanalysis for Cation Configuration in Irradiated Magnesium Aluminate Spinel
Authors: Matsumura S. , Soeda T. , Zaluzec N. J. , Kinoshita C.
Published: April 2011

High angular resolution electron channeling x-ray spectroscopy (HARECXS) was examined as a practical tool to locate lattice-ions in spinel crystals. The orientation dependent intensity distribution of emitted x-rays obtained by HARECXS is so sensitive to lattice-ion configuration in the illuminated areas that the occupation probabilities on specific positions in the crystal lattice can be determined accurately through comparison with the theoretical rocking curves. HARECXS measurements have revealed partially disordered cation arrangement in MgO·nAl2O3withn= 1.0 and 2.4. Most A13+lattice-ions occupy the octahedral (VI) sites with 6-fold coordination, while Mg2+lattice-ions reside on both the tetrahedral (IV) and the octahedral (VI) sites. The structural vacancies are enriched in the IV-sites. Further evacuation of cations from the IV-sites to the VI-sites is recognized in a disordering process induced by irradiation with 1 MeV Ne+ ions up to 8.9 dpa at 870 K.
Theoretical Explanation of Pt Trimers Observed by Z-Contrast STEM
Authors: Sohlberg Karl , Pantelides Sokrates T. , Pennycook Stephen J.
Published: April 2011

First-principles quantum-mechanical calculations on γ-alumina have revealed a fascinating “reactive sponge” phenomenon. γ-alumina can store and release water, but in a unique, “reactive” way. This “reactive sponge process” facilitates the creation of aluminum and oxygen vacancies in the alumina surface. Earlier atomic-resolution Z-contrast STEM images of ultradispersed Pt atoms on a γ-alumina support showed the individual atoms to form dimers and trimers with preferred spacings and orientations that are apparently dictated by the underlying support[1]. In turn, the reactive sponge property of γ-alumina is the key to understanding the Pt clusters. Our calculations demonstrate that if three Pt atoms fill three vacancies created during the reactive sponge process, the resulting geometry precisely matches that of the Pt trimers observed in the Z-STEM images. Understanding the initial nucleation of small clusters on the complex gamma alumina surface is an essential first step in determining the origins of catalytic activity.
Quantitative Mapping of Concentrations and Bonding States by Energy Filtering TEM
Authors: Mayer J. , Plitzko J. M.
Published: April 2011

We have developed new methods to quantify the data acquired by electron spectroscopic imaging (ESI) in an energy filtering TEM. The analysis is based on recording series of energy filtered images across inner-shell loss edges or in the low-loss region. From the series of ESI images, electron energy loss (EEL) spectra can be extracted and subsequently analysed using standard EELS quantification techniques. From an ESI series one can measure the absolute amount (area density) of an element in the given sample area or the concentration ratios of one element with respect to other elements. Spectrum line-profiling has been shown to be an efficient way to acquire and present the information on the chemistry of an interface. The results obtained for different metallisation layer systems show that segregation in the monolayer range can still be analysed with high spatial resolution. For the study of the energy-loss near-edge structure (ELNES) a higher energy resolution is required. ESI series with narrow energy window width can be used to distinguish between different bonding states of a given element and is demonstrated for thin films of diamond and amorphous carbon.
Measuring the Thin Film Strain Tensor Near Aluminum Grain Boundaries via a New Image Processing Approach to CBED HOLZ Patterns
Authors: Inoue J. , Schwartzman A. F. , Freund L. B.
Published: April 2011

HOLZ lines formed in a CBED pattern provide the most accurate means to measure a local strain tensor with high spatial resolution over mesoscopic length scales. With the advent of energy-filtering in a field-emission TEM, the precision of this measurement increases by filtering out the inelastically scattered electrons. This paper presents an alternate approach to obtaining the same increased precision by image processing of CBED patterns formed in a conventional LaB6 microscope. This technique results in the determination of the full strain tensor within ±0.01%. It is based on developing a Wiener filter for CBED patterns, deconvoluting the point spread function of the CCD camera, using the Hough transform to measure distances between HOLZ line intersections, and subtracting out an experimentally determined projector lens distortion. The present technique has been used to measure the strain tensor for the two types of grain boundaries found in MBE grown Al thin films on Si which have the mazed bicrystal microstructure.
Inelastic Deformations in Multi-Walled Carbon Nanotubes
Authors: Tekleab D. , Czerw R. , Rubio A. , Ajayan P.M. , Carroll D.L.
Published: April 2011

We report the use of high power ultrasonic agitation to create inelastic deformations in multiwalled carbon nanotubes. Using STM coupled with TEM we show that this damage can range from kinking to breaking of continuous tube walls into segments. Such deformed tubes provide an insight into the role of re-hybridization in the electrical and mechanical properties of tubes.
Effect of Gas Adsorption on the Electrical Properties of Single-Walled Carbon Nanotubes Mats
Authors: Marliere C. , Poncharal P. , Vaccarini L. , Zahab A.
Published: April 2011

Single wall nanotubes have been made by arc-discharge method. Residual impurities (fullerenes, amorphous carbon, catalyst metals…) have been removed by tangential filtration process followed by high temperature annealing under vacuum (1200 °C). In this work we present results on the influence of the surrounding gas nature (N2, H2, CO2, H2O…) on the electrical resistivity of carefully outgassed mat of such samples.

In particular, we have observed that the sample resistance exhibits a strong dependence on water contamination during the transfer to the measurement reactor.
Fluorinated Diamond-Like Carbon Films Produced by Plasma Immersion Ion Processing Technique
Authors: Hakovirta M. , Lee D. H. , He X. M. , Nastasi M.
Published: April 2011

Fluorinated diamond-like carbon (F-DLC) coatings were deposited on polished silicon substrates with plasma immersion ion processing (PIIP) technique. In the PIIP technique, pulsed glow discharge plasma from a mixture of acetylane and hexafluoroethane gases was used. Contact angle measurements were performed in order to see the un-wetting properties of the coatings. The film composition was measured with Rutherford Backscattering Spectroscopy (RBS) and Elastic Recoil Detection Analysis (ERDA) and the hardness was measured with a Nanoindenter® II. The results clearly show that the un-wetting properties and hardness are strongly dependent on the fluorine incorporation in the F-DLC coatings. With optimized gas ratio of acetylane and hexafluoroethane gases, a combination of extremely good un-wetting properties and high hardness was achieved.
Characterization and Dielectric Properties of Fluorinated Amorphous Carbon Measured by Capacitance-Voltage Response and Spectroscopic Ellipsometry
Authors: Glew A. D. , Cappelli M. A.
Published: April 2011

This paper describes a comparison between capacitance-voltage (CV) and spectral ellipsometry (SE) measurements of the dielectric constant of fluorinated amorphous carbon films. Whereas CV measurements require the construction of metal-insulatorsemiconductor (MIS) structures, SE measurements can be made on as-deposited films, and are much easier to implement. An examination of the results indicate that under certain conditions, the SE measurements give values that are in reasonable agreement with the more direct measurements based on the electrical (CV) response of the dielectric layer. The films reported on here had dielectric constants ranging from 3 – 5, and, in some cases, show promising characteristics for use as low-k dielectrics in semiconductor devices.
Voids Investigation of Amorphous Carbon Films Deposited by DC-Magnetron Sputtering: A Small Angle x-ray Scattering and Gas Thermal Effusion Study
Authors: Freire F.L. , Jacobsohn L.G. , Franceschini D.F. , Camargo S.S.
Published: April 2011

Amorphous carbon films were deposited onto (100) Si crystals and onto ultra-pure Al foils by dc-magnetron sputtering with different Ar plasma pressures, from 0.17 to 1.4 Pa. We investigate the voids structure and the voids density in these films by means of small angle x-ray scattering (SAXS) and mass spectrometry of effused gases. The analysis of the effusion spectra provided clear evidence that films deposited at lower pressures are compact, while the films deposited at higher pressure present a more open structural arrangement, confirming density results obtained by using ion beam techniques. SAXS results reveal that the fraction of open volumes increases with the plasma pressure: a direct correlation between film density and open volume fraction is found. These different film microstructures could be explained by the existence of different bombarding regimes during film growth