bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Collimation On Sputtered Alcusi and Almg Microstructures And Electromigration Failure Characteristics
Authors: Licata Thomas J. , Sullivan Timothy D. , Bass Roy S. , Ryan James G. , Knorr David B.
Published: March 2011

Increasing circuit densities produce higher metal wiring aspect ratios, and more difficult feature fill for damascene processing. One method of extending the use of sputter deposition to challenging aspect ratios is to collimate the sputtered flux using a collimator plate, and to avoid randomizing the collimated flux by using low process pressures corresponding to long sputtered atom mean free paths. In this paper, we discuss our fabrication of damascene AI-0.5Cu-2Si and AI-2Mg wiring using both collimated and uncollimated sputtering, and our observations of collimation-induced changes in Al alloy electromigration and microstructure. Our experiments show that collimation has only a small effect on AlCuSi, but a large effect on AIMg. Specifically, the median time to electromigration failure for collimated AIMg was ∼10X the value for uncollimated AlMg and ∼6X the values for collimated and uncollimated AlCuSi. Transmission electron microscope and x-ray diffraction analyses of these films show that the collimation-induced improvement in AIMg t50 is associated with the formation of smaller, lower strain grains which are clustered in very well-oriented (111) domains. We propose that the advantageous AlMg microstructure results from enhanced texture produced by aspects of the collimated deposition active in the absence of incoherent precipitates.
Continuum Model of Epitaxial Roughening
Authors: G. Amar Jacques , Family Fereydoon
Published: March 2011

A continuum equation for epitaxial and thin-film growth in which diffusion along the surface is the dominant relaxation process and the full diffusion along the surface is taken into account, is studied. The interface width is found to grow linearly with time (height) in agreement with recent experiments. At late times dynamic scaling breaks down and the surface develops a characteristic morphology which is similar to that found in experiments.
Epitaxial Growth of Eute on Pbte (111) Influenced by Strain-Induced Coherent 3D Islanding
Authors: Springholz G. , Bauer G. , Schilcher K.
Published: March 2011

EuTe on PbTe is an example of a strained layer heteroepitaxial system with a moderate lattice-Mismatch of 2%. Using reflection high-energy electron diffraction (RHEED), the phase diagram of heteroepitaxial growth of EuTe on PbTe (111) by molecular beam epitaxy was established, indicating that only in a narrow regime of growth conditions does two dimensional layer-by-layer growth occur. Using in situ RHEED, combined with ex situ atomic force Microscopy, the evolution of the surface morphology during heteroepitaxial growth was investigated. It is found that at the critical layer thickness an abrupt surface roughening occurs. Studying the dependence of this surface roughening transition on substrate temperature and on the Eu-to-Te2 beam flux ratio used for growth, the critical layer thickness is found to decrease strongly as the surface kinetics are enhanced, even if the substrate temperature is kept constant. These results indicate that the surface roughening is driven only by the surface kinetics, which strongly supports the model of strain relaxation by coherent three dimensional islanding.
Measurement of Lattice Relaxation During Epitaxy Using Tunneling Microscopy: Ge on Si(111)
Authors: Theiss Silva K. , Chen D.M. , Golovchenko J.A.
Published: March 2011

We have used the tunneling microscope to measure the lattice relaxation of Ge islands on Si (111) as a function of their height. Lattice constants on the top surfaces of individual Ge islands can be measured with an uncertainty of approximately one percent. The lattice constant is a continuous, Monotonically increasing function of island height up to 20 bilayers. At heights around 5O bilayers, the island-top lattice parameter may exceed that of bulk Ge. Defects can be observed penetrating the top surface of islands which have heights around 90 bilayers.
Sem Analysis of the Nucleation of Tin Oxide Films on Glass Surfaces
Authors: Mao Limin , Benoit Robert E. , Proscia James W.
Published: March 2011

Fluorine-doped tin oxide films were produced by atmospheric pressure chemical vapor deposition (APCVD) from the reaction of tin tetrachloride, water, and difluoroethanc. Tin oxide films deposited on glass substrates containing high sodium concentrations tended to be of lower quality with higher resistivities than films deposited on low sodium glass. Scanning electron Microscopy (SEM) was used to study the differences in film nucleation on the high and low sodium containing glass substrates. Eiarly in the nuclcation process, individual grains of tin oxide crystals arc observed to be distributed discontinuously over the substrates. As the deposition time was increased the number of nucleation sites increased and the individual grains became larger. The number of nucleation sites was consistently higher on the high sodium glass. However, numerous inclusions of sodium chloride crystals were observed by EDX in the tin oxide films deposited on the high sodium glass. SEM cross sections revealed how the film growth converted from the grains, which initially nucleated on the glass surface, to columns in the direction perpendicular to the substrate surface. Results for tin oxide grown on sodium-containing glass over coated with silica are also be presented.
Growth of Cuinse2 on (lOO) Gaas by Molecular Beam Epitaxy
Authors: Tseng Bae-Heng , Lin Song-Bin
Published: March 2011

Domain-free epitaxial layer of CuInSe2 has been successfully grown on (lOO) GaAs at the substrate temperature above 470°C. Both TEM and X-ray analyses were performed to verify this result. The CuInSe2/GaAs interface was examined by high resolution TEM. For films high in indium, InSe was identifed by X-ray diffraction. TEM observations showed that the InSe precipitates were rectangular in shape and the habit plane was determined to be (110). Photo-assisted MBE technique had also been used for the growth of CuInSe2 films with high crystalline quality. The epitaxial temperature was significantly reduced to 300°C.
Epitaxial Growth of Titanium Nitride Films On (100) Silicon Three-Dimensional Heterostructures: Processing and Characterization
Authors: Chowdhury Rina , Biunno N. , Narayan J.
Published: March 2011

We have shown that epitaxial films can be grown on highly lattice mismatch systems by domain epitaxial growth. For titanium nitride films on (100) silicon substrates, it is shown that epitaxial growth can occur by Matching M TiN = n asi, where M and n are simple integers with values of 4 and 3 respectively, giving rise to less than 4.0% Misfit. We have investigated the formation of epitaxial titanium nitride films grown on (100) Si by pulsed laser (KrF: λ = 248 nm, τ = 25 ns) physical vapor deposition technique at different substrate temperatures, ranging from 200°C to 600°C. After optimizing the deposition conditions for epitaxial TiN film on Si, we have grown epitaxial silicon film on TiN. The epitaxial relationship was found to be <100> Si ∥ <100> TiN π <100> Si. This semiconductor-Metal-semiconductor device configuration has potential applications in three-dimensional integrated circuits and radiation hardened devices. The success of this technology is predicted on our understanding of: (a) defects at interfaces of Si/TiN/Si, and (b) stresses/strains at interfaces. This paper focuses on the nature of epitaxial growth and analyzes the atomic structures of defects at Si/TiN/Si interfaces using high resolution transmission electron Microscopy (HRTEM). These results are correlated with the results from theoretical modeling of Si/TiN/Si heterostructures.
Room Temperature Epitaxy of Al (100) on Si (111)
Authors: Sosnowski Marek , Ramac Samuel , Brown Walter L. , Kim Young O.
Published: March 2011

There are a number of published reports on the epitaxial growth of Al(111) on Si(111) surfaces usually following a high temperature treatment of the Si surface in UHV. In contrast to these results, we have for the first time observed dominant epitaxial growth of Al(100) films on Si(111) surfaces that have been carefully cleaned and hydrogen terminated and not heated prior to effusion cell deposition of Al at room temperature in UHV. X-ray diffraction shows sharp and intense Al (200) diffraction, enhanced by post deposition annealing. Crystal quality and the dominance of Al(100) structure depend strongly on the substrate treatment and the off-cut angle, both of which control the steps on the Si(111) surface. The steps were found responsible for the epitaxial alignment of the film and the substrate lattices. Details of this alignment were observed in TEM cross-sectional images of the interface.
The Template Technique Applied to Epitaxial Growth of CrSi2 on Silicon (111)
Authors: Manan John E. , Long Robert G. , Vantomme André , Nicolet Marc-A.
Published: March 2011

The template growth technique was applied to the growth of CrSi2 thin films on Si(111) by UHV E-gun evaporation. A 4He+ channeling yield of -50% was obtained for an epitaxial -2100 Å-thick film of continuous morphology grown at 450° C The heteroepitaxial relationship is CrSi2 (001) / Si (lll) with CrSi2[210] ∥ Si<110>.

In the case of film formation simply via reactive deposition epitaxy (RDE, chromium evaporation onto hot substrates) a severe crystallinity-Morphology tradeoff is always observed. Continuous films are formed at low temperature but no long-range epitaxy is found. On the other hand, high temperature annealing of these films induces the formation of islands that show good epitaxial alignment with the substrate. This tradeoff was addressed with the template growth technique.
Defect-Free Coalescence of Silicon Layers Over SiO2
Authors: Banhart F. , Nagel N. , Phillipp F. , Bauser E.
Published: March 2011

Defect-free coalescence of Si layers which grow laterally over partially oxidized Si substrates is achieved in liquid phase epitaxy from indium solution. An adequate design of the oxide pattern on (111) substrates ascertains that the growth fronts of the Si layers merge gradually on the SiO2 and avoids the formation of inclusions or crystallographic defects. Electron Microscopy in diffraction contrast and convergent beam electron diffraction reveal that the epitaxial Si layers bend towards the substrate as they grow laterally over the SiO2 film. The layers straighten out again as they merge and form a perfect seam of coalescence.
Surface Stress Effects on Thin Film Growth
Authors: Cammarata R.C.
Published: March 2011

A review of surface and interface stresses relevant to thin film growth is presented. It is shown that surface stress effects that are generally ignored in the analysis of epitaxy can have an influence on the critical thickness for epitaxy, especially at larger Misfits. A discussion of intrinsic stress generation from surface stress is also presented.
Atomistic Calculations on the Surfactant Role of Indium in the Homoepitaxial Growth of Cu on Cu (100)
Authors: Breeman M. , Barkema G.T. , Boerma D.O.
Published: March 2011

We present atomistic calculations for the system In on Cu (100), using the atom-embedding model of Finnis and Sinclair. It was found that the energy banier for Cu adatoms to jump off a descending step is higher than the adatom migration energy, i.e. descending steps form an additional barrier for diffusion. The presence of In atoms at or in step edges or island edges drastically reduces the energy barrier for interlayer diffusion of Cu adatoms. Therefore, we predict that In atoms may be used as surfactants to improve the homoepitaxial growth of Cu on Cu (100), especially in the temperature range between 150 and 200 K.
Ab Initio Quantum Chemical Studies of Hydrogen and Halogen Migration on the Diamond (110) Surface
Authors: Melnik M. S. , Goodwin D. G. , Goddard W. A.
Published: March 2011

Activation energies for the migrations of H, F, and Cl on the diamond C(110) surface are calculated by quantum chemical methods using hydrocarbon cluster Models. The calculations include extensive basis sets with Many-body effects at the level of single and double excitations from Hartree-Fock and Complete-Active-Space wavefunctions. The calculated activation barriers for the (1,2) and (1,3) Migrations indicate that such migrations are too slow to compete with gas-surface reactions during chemical-vapor deposition of diamond. However, the (1,4) migrations of both H and Cl are calculated to be sufficiently fast to compete with gas-surface reactions under typical diamond growth conditions.
Empirical Interatomic Potential for Si-H Interactions
Authors: Ramana Murty M.V. , Atwater Harry A. , Watson Thomas J.
Published: March 2011

An empirical TersofF-type interatomic potential has been developed for describing Si-H interactions. The potential gives a reasonable fit to bond lengths, angles and energetics of silicon hydride molecules and hydrogen-terminated silicon surfaces. The frequencies of most vibrational modes are within 15% of the experimental and ab initio theory values. The potential is computationally efficient and suitable for molecular dynamics investigations of various processing treatments of hydrogen-terminated silicon surfaces.
Strained Layer Epitaxy: The Role of a Capping Layer and mechanism of Strain Compensation in Multilayers Systems
Authors: Lefebvre I. , Priester C. , Allan G. , Lannoo M.
Published: March 2011

Within a valence force field framework, we calculate the critical thickness of a film lattice mismatched to the substrate on which it is epitaxially deposited. A capping layer lattice matched to the substrate is known to enhance the critical thickness. We calculate the efficiency of the capping layer and study how the capping layer thickness modifies this efficiency. We also demonstrate how using a capping layer which is no more lattice matched to the substrate may improve the effect of the capping layer. Extension to strain compensation in multilayer systems is provided. In the case of uncapped systems, or systems with a thick capping layer lattice matched to the substrate, the results we have obtained using a microscopic description are compared to recent results, obtained using continuous classical elasticity.
Density-Functional Study of Chemisorption of Oxygen on Al (111)
Authors: Ramprasad R. , Drabold D. A. , Adams J. B.
Published: March 2011

We present ab initio studies of oxygen adsorption on Al (111) using a density-functional local-orbital method. Our results indicate that, for very low oxygen exposures, the oxygen atoms are incorporated in the first Al (111) layer. For exposures corresponding to approximately a monolayer of oxygen, an ordered oxygen overlayer with the O atoms sitting on the 3-fold sites was seen. These results are consistent with EXAFS experiments. We have also studied clean Al surfaces and have analyzed their surface relaxations.
Localized Texture Formation and its Detection in Polycrystalline Thin Films of Gold
Authors: Harris Karen E. , King Alexander H.
Published: March 2011

We have developed a technique for detecting microscopic variations in texture in thin film TEM specimens using conical dark field imaging. This technique has been used to identify texture variations in 25nm thick gold films which were deposited on rock salt and annealed at 150°C. After annealing, the films were Mostly (111) textured with one micrometer wide bands of contrast in which the grain remained randomly oriented. When the contrast due to the variation in texture was first observed, the films were columnar-structured and the grain sizes in both the textured and un-textured regions were uniform, with a mean equivalent diameter of 54nm; no abnormal grains were observed. After additional annealing, abnormal (111) oriented grains appeared in some untextured regions of the film. The evolution of texture during grain growth and the influence of substrate morphology on texture formation will be discussed.
Strain, Stress, and Magnetic Surfaceanisotropy of Epitaxial FE(110)/MO (110) Multilayers
Authors: Osgood R.M. , Clemens B.M. , White R.L. , Brennan S.
Published: March 2011

Grazing incidence and asymmetric X-ray diffraction were used to measure the stress and strain state of Fe(110)/Mo(110) Multilayers. The highest stress in the Fe constituent of the multilayer was along the [110] in-plane direction and was due to interaction with the substrate. The Magnetic anisotropy of the Fe Multilayer constituent was measured and the magnetic surface anisotropy, which favored in-plane [001] magnetization, was deduced. In contrast, the magnetic surface anisotropy of a single layer of Fe on W preferred in-plane [110] magnetization, in agreement with the Néel Model.
Substrate Effects on The Growth of Oriented MgO Thin Films
Authors: Chang Bertha P. , Sonnenberg Neville , Cima Michael J.
Published: March 2011

MgO thin films were deposited onto SrTiO3 and LaAlO3 single crystal substrates using off-axis rf-Magnetron sputtering. Films from 1000–3000Å thick were grown in an Ar - 20%O2 atmosphere at temperatures between 200 and 700°C. X-ray measurements indicate MgO grows epitaxially on SrTiO3 at temperatures above 400°C. The Microstructure of these films was smooth and dense. At deposition temperatures below 400°C, orientation is Maintained, but a rough plate-like microstructure begins to take over. MgO films deposited on LaAlO3 grow with a high degree of preferred orientation. Film Microstructure resembled MgO deposited on SrTiO3 at temperatures below 400°C. Variations in the quality of MgO films grown on LaAlO3 were also observed which may be related to variations in steps on the substrate surfaces.
Texture in Sputtered MO Films
Authors: Karpenko O.P. , Vill M. , Malhotra S.G. , Bilello J.C. , Yalisove S.M.
Published: March 2011

The evolution of texture in thin films must be fully understood in order to take advantage of favorable crystallographic orientations in a material for a given application. The development of an out-of-plane texture (preferred crystallographic orientation in the growth direction) and an in-plane texture (preferred crystallographic orientation in the plane of growth) in sputter deposited, thin mo films on Si was studied using transmission electron microscopy and diffraction, and conventional x-ray pole figures. For a range of deposition parameters, a strong (110) out-of-plane texture developed within 1000Å, while a strong in-plane texture did not develop until a thickness of about 1 μm.
Grain Growth in Thin Films With Variable Grain Boundary Energy
Authors: Frost H.J. , Hayashi Y. , Thompson C.V. , Walton D.T.
Published: March 2011

In simulations of grain growth in thin films we have considered the effect of variations in grain boundary energy. Boundary energy depends on both the misorientation between the two neighboring grains, and the angles which the boundary plane makes with the crystallographic axes of the two crystals. Variations in grain boundary energy mean that dihedral angles at triple junctions deviate from 120°. The proportionality between boundary velocities and local curvatures, and the critical curvature for boundary pinning due to surface grooving also both depend on boundary energy. One effect of variable boundary energies is that grains no longer gain or lose area at rates determined solely by their topology or number of sides. (They no longer obey the Von Neumann/Mullins law). Another effect is that as the grain structures evolve, the fraction of high-energy boundaries decreases. Also, the stagnant structures have broader grain size distributions.
On the Evolution of Copper Oxide Films Grown on α-A12O3 By Pulsed-Laser Ablation
Authors: Bench Michael W. , Sartain Kevin B. , Heffelfinger Jason R. , Barry Carter C.
Published: March 2011

Pulsed-laser ablation was used to deposit copper oxide onto single-crystal substrates of (0001) OC-AI2O3 at temperatures ranging up to 900°C. Prior to deposition, the substrates were chemically cleaned and annealed to create a surface structure of low-index terraces separated by crystallographic steps. After deposition, the samples were characterized using transmission electron microscopy and scanning electron Microscopy.

The deposited film evolved by an island growth process, with the morphology of the particles being dependent on the growth conditions, substrate orientation, and nature of the substrate surface. Both CuO and Cu2O were produced by the depositions. The phase observed changed from CuO to Cu2O with increasing deposition temperature, as would be expected based on the equilibrium phase diagram. In depositions performed on (0001) alumina substrates with widely spaced surface steps, it was found that on some surface terraces one characteristic particle morphology was produced whereas on others a second morphology was dominant. This suggests that the plane of surface termination in the alumina lattice, which consists of a layer of either Al or O in this orientation, is influencing the growth process.
Nucleation of Special Orientations During Heteroepitaxial Growth of Diamond on Silicon
Authors: Tzou Y. , Raj R. , Bruley J. , Ernst F. , Riihle M.
Published: March 2011

The orientation relationships that develop in the early stages of diamond nucleation on silicon, were examined by TEM and HRTEM. The films were produced by microwave plasma assisted CVD. Two types of interface regions were identified. In one case an amorphous interlayer was observed and the nucleation of diamond was nanocrystalline. In the second case the interface was apparently free from a second phase; in these instances the diamond and silicon lattices formed special orientations. The special orientations were identified as the following: (a) <110> 60 degree rotation, (b) <110> 90 degree rotation and (c) diamond {111} plane tilted 6 degrees from silicon {220} plane. The orientation relationships are analyzed in terms of geometric models that seek the best fit between the diamond and silicon lattices at the interface plane.
Atomistic Configurations of Diamond/Silicon Interface
Authors: Nandedkar A. S. , Narayan J.
Published: March 2011

The quality of diamond thin films on nondiamond substrates is often poor because of large number of defects such as dislocations, twins, stacking faults and grain boundaries. The diamond films often exhibit poor adhesion on nondiamond substrates because of large differences in interatomic potentials between the film and the substrate. The epitaxial nature of the film is determined not only by lattice matching but also by gradient in interatomic potentials across the interface. We have used computer simulations to study energetics of different geometric configurations of C / Si interfaces. The simulations predict that an C / SiC interface had the least energy and therefore the preferred interface configuration. This is in concordance with experimental deposition of C on Si which resulted in formation of an SiC layer in between C and Si.
Epitaxial Chemically Derived Lanthanum Aluminate Films for Ba2YCu3O7−x Devices
Authors: Faing Man , Cima Michael J.
Published: March 2011

Lanthanum aluminate (LaAlO3) has been used as a substrate material for depositing Ba2YCu3O7−x (YBCO) films. In the present study, chemically derived epitaxial LaAlO3 thin films were used for depositing epitaxial YBCO films. These epitaxial LaAlO3 films were deposited on both (100) SrTiO3 and (100) LaAlO3 single crystal substrates by pyrolysis of a mixed nitrate precursor. Crystallization of LaAlO3 on lattice-Matched substrates occurs at below 650°C, whereas crystallization on non lattice-Matched substrates occurs at much higher temperature. The average surface roughness of these LaAlO3 films can be as low as 7Å. The YBCO films derived from metalorganic deposition of metal trifluoroacetate precursors were deposited on these epitaxial LaAlO3 films on SrTiO3 substrates. The resultant YBCO films have critical current densities of > 2 × 106 A/cm2 at 77K and zero field. Transmission electron microscopy of these films shows that they are highly epitaxial yet have pore of about 15–30 nm in size. Chemically derived LaAlO3 films also were used to planarize stepped substrates.
Evolution of Yttrium Aluminum Garnet Films by Solid-State Reaction
Authors: Heffelfinger Jason R. , Barry Carter C.
Published: March 2011

Yttrium aluminum garnet (YAG) films were produced by reacting thin Y2O3 layers with single-crystal Al2O3 substrates. Y2O3 films were deposited using pulsed-laser deposition (PLD), which produced smooth textured films on specially prepared (0001) α-Al2O3 substrates. Solid-state reaction of the Y2O3 with the Al2O3 was induced by specific heat treatments. Transmission-electron microscopy was used to characterize the reaction products of each heat treatment. For a reaction temperature of 1200°C, cross-sectional TEM specimens revealed the development of Monoclinic Y4Al2O9 at the interface between the Y2O3 and the Al2O3. Development of YAG was seen to occur at the interface between the Al2O3 and the Y4Al2O9 for a slightly higher reaction temperature of 1250°C. The Metastable Y4Al2O9 phase and the Y2O3 phase were found to be consumed at higher reaction temperatures to form the equilibrium Y3Al5O12 (YAG) phase. The Morphology of the YAG film was characterized by scanning-electron microscopy.
Interfacial Reaction Between a Sputter Deposited MoSi2 Film and its Oxidation Product on Al2O3 at 1300°C in Air.
Authors: Wu P.K. , Kolaya L.E. , Duquette D.J. , Hudson J.B.
Published: March 2011

The chemical compatibility between MoSi2 and Al2O3 at 1300° C was examined using sputter deposited MoSi2 films, 0.7 μm thick, on sapphire and on polycrystalline alumina. The oxidation behavior of the sputter deposited films was found to be identical to that of bulk MoSi2. The oxidation products of the MoSi2 are Si oxides and lower suicides of Mo. MoO3 is formed and sublimes at the free surface. Oxidation is found to occur at the SiO2/MoSi2 interface. Just beneath this interface, suicides of mo and two oxidation states of Si were identified. No reaction between MoSi2 and alumina was found. In the case of a sapphire substrate, after mo was completely eliminated from the interface, silica reacted with the substrate and eventually phase separated into high- and low-silica phases. Nucleation, growth and coalescence of high-silica precipitates were observed.
Epitaxial Alignment and Microstructural Development in Lithium Niobate Thin Films Prepared by Metallo-Organic Decomposition.
Authors: Braunstein G. , Paz-Pujalt G. R. , Blanton T. N.
Published: March 2011

We investigate the microstructural evolution and epitaxial alignment of thin films of LiNbO3 deposited by the Metallo-organic decomposition method on Al2O3. The LiNbO3 films are prepared by spin coating and thermal decomposition of a solution of Metallo-organic precursors on single-crystal, <0001> oriented, Al2O3 substrates, followed by heat treatment in a quartz tube furnace at temperatures ranging from 500 to 1000 °C.

X-ray diffraction analysis reveals that films heat treated at 600 °C for 1 h are highly oriented along the c-axis direction, but the alignment is not good enough to permit channeling of 2 MeV He++ particles. Heat treatment at 900 °C improves significantly the epitaxial alignment as determined by ion-channeling measurements. However, concomitantly with the improvement in crystal orientation, the films break up into a network of LiNbO3 grains, partially uncovering the Al2O3 substrates along grain boundaries. Pole figure analysis shows that all the grains share the same in-plane orientation.
Microstructural Evolution of Epitaxial MgAl2O4 Thin Films Derived From Metal Nitrates and From Metal Alkoxides
Authors: Faing Man , Cima Michael J.
Published: March 2011

Magnesium aluminate (MgAl2O4) is a potential dielectric material in Ba2YCu3O7−x (BYC) devices. In the present study, epitaxial MgAl2O4 films were deposited on (100) SrTiO3 single crystal substrates by pyrolysis of chemical precursors. Two precursors were used: one was a mixed nitrate precursor, and the other was MgAl2(OC3H7)8. Crystallization of MgAl2O4 on lattice-Matched substrates is observed at 700°C. The average surface roughness of these MgAl2O4 films is about 6Å. These chemically-derived MgAl2O4 films have demonstrated the potential for planarization by metalorganic deposition. The relationship between the processing parameters and the surface morphology of these MgAl2O4 films will be discussed.
Molecular-Dynamics Simulations of Low-Energy Ion/Surface Interactions During Ion-Beam-Assisted Thin Film Deposition.
Authors: Feil H.
Published: March 2011

Molecular dynamics simulations are performed of low-energy ion irradiation of two-dimensional Cu islands on a Cu(111) surface. The irradiation of the surface with low-energy particles influences the mobility of the atoms in the surface region and therefore may alter the thin film growth Mode. The effect of 100 eV Ar+ ions incident at grazing angles is limited to situations in which the ions hit the edges of the islands. In Most cases the islands lose one or two atoms. Changing the angle-of-incidence or changing the type of the incident particle has a strong influence on the size distribution of the two-dimensional islands.
Structural Transformation During the Epitaxial Growth of a System with a Large Misfit: MBE Study of Ni on Au (100)
Authors: Gilles B. , Marty A. , Patrat G. , Vassent J.L. , Joud J.C. , Chamberod A.
Published: March 2011

The growth of Ni on Au (100) has been investigated by MBE. It has been found that a Metastable BCT Ni (100) phase is coherent with the substrate up to a thickness of 5 ML. Then a structural transformation analogous to a raartensitic transition occurs, and the structure becomes FCC Ni (110). We show that the interfacial stress is progressively relieved by a high density of stacking faults, as was predicted by Bruinsma and Zangwill for epitaxial overlayers with a large Misfit.
The Role Of Steps On The Micro Structure Of Titanium-Oxide Films Deposited By Pld Onto (100) Mgo Surfaces
Authors: King Simon , Barry Carter C.
Published: March 2011

The phenomenon of graphoepitaxy, whereby island nucleation occurs preferentially at steps, is a prime example of a manner in which the substrate morphology (and notably surface steps) can affect the microstructure of as-deposited thin-films. This paper provides a further illustration of the fundamental importance of the substrate morphology to the development of the thin-film microstructure, employing the example of TiO2 deposited by pulsed-laser deposition (PLD) directly onto specially prepared (100) MgO TEM foils. The same areas of these foils are imaged both before and after deposition.
Single-Atom Diffusion on Silver and Gold Surfaces
Authors: Boisvert Ghyslain , Lewis Laurent J.
Published: March 2011

We present the results of a detailed Molecular-dynamics study of single-atom diffusion on the surfaces Ag (100) and (111), and Au (111), using the embedded-atom method to describe the interactions between the atoms. We find that diffusion is Arrhenius-like up to temperatures corresponding to a large fraction of the activation energy. We demonstrate, in addition, that an excellent description of the rate of diffusion is provided by a simple transition-state theory, together with parameters that derive directly from the static potential-energy surface. The Model predicts very accurately the activation energies, while the prefactor for diffusion is obtained within a factor of 2, a discrepancy we attribute to the neglect, in the Model, of the details of the structure of the surface. At higher temperatures, diffusion becomes clearly non-Arrhenius, and the model fails.
Kinetics of Surface Roughening and Smoothing During Ion Sputtering
Authors: Chason E. , Mayer T. M. , Howard A. J.
Published: March 2011

We have measured the kinetics of roughness evolution during low energy ion sputtering of SiO2 surfaces using in situ X-ray reflectivity. Sputtering with heavy ions (Xe) leads to rapid roughening of the surface that can not be explained by a simple random removal process. Subsequent bombardment with light ions (He, H) leads to an exponential decrease in the surface roughness. These kinetics are explained quantitatively by a linear model that contains a balance between smoothing by surface diffusion and viscous flow and roughening by sputter removal of Material. A curvature dependent sputter yield leads to amplification of a limited range of spatial frequencies on the surface and the formation of a ripple topography.
Tem Investigations of CdTe/GaAs(001) Interfaces
Authors: Angelo J.E. , Gerberich W.W. , Bratina G. , Sorba L. , Franciosi A. , Mills M.J.
Published: March 2011

In this study, cross-sectional transmission electron microscopy (XTEM) was used to investigate the defect structure at the interface between CdTe(001) and GaAs(001) as well as CdTe(1 11) and GaAs(001). The heterostructures were fabricated by molecular beam epitaxy on GaAs(001) buffer layers grown in-situ by molecular beam epitaxy. The defect structure at the as-deposited CdTe(001)/GaAs(001) interface consists of both dislocations and planar faults. The planar faults are both microtwins and stacking faults. It is found that annealing of the film ex-situ causes a restructuring of the CdTe near the interface, with the microtwins being completely removed upon annealing to 450°C for 100 hours. The CdTe(111)/GaAs(001) thin film structure consists of a large number of microtwins parallel to the growth direction. This twinned structure is shown to be related to the relaxation of a residual misfit strain normal to the twin direction. Possible mechanisms for the relaxation are discussed.
Relationship Between Crystal Defects, Ge Outdiffusion and V/III Ratio in MOVPE Grown (001) GaAs/Ge
Authors: Frigeri C. , Atrolini G. , Pelosi C. , Longo F.
Published: March 2011

Two regimes of defect generation have been found in MOVPE GaAs/Ge layers upon changing the V/III ratio between 1.3 and 11.8. For low V/III ratio the layers contained misfit dislocations along with stacking faults that had been generated by dissociation of the misfit dislocations. The stacking fault density increased with decreasing V/III ratio. This might be explained by an enhanced mobility of the dissociated partials due the reduced unintentional doping of the layer caused by reduced Ge outdiffusion from the substrate when V/III is small. The secon regime corresponds to high V/III ratios and is characterized by the absence of misfit dislocations and the presence of a high density of planar defects. This means that breakdown of the 2D layer-by-layer growth occurred and 3D island growth prevailed.
Hrem Investigation of Ai-MgO Interface
Authors: Vellinga W.P. , Verwerft M. , De Hosson J.Th.M. , Hibma Tj.
Published: March 2011

A metal-ceramic interface was produced by depositing Al on a {100} MgO substrate in a MBE system. The interface was studied with High Resolution Electron Microscopy. Results of some image simulations are shown, raising the question if effects of ionicity and charging should be taken into account.
Behavior of Damage in Selectively Implanted SiGe/Si
Authors: Theodore N. David , Tam Gordon , Whitfield Jim , Christiansen Jim , Steele John
Published: March 2011

Epitaxial SiGe/Si layers are being extensively investigated for use in base regions of high-speed heterojunction bipolar-transistors (HBTs). Extended defects can be formed in SiGe/Si layers by ion-implantation. Defects, once formed in the layers, can negatively impact electrical performance and also future reliability of the HBTs. The present study investigates the interaction between selective-implant damage and strained SiGe/Si layers of sub-critical thickness. Implant-damage is observed to form dislocation-sources at the edges of implanted regions in SiGe/Si heterolayers. The dislocation sources produce glide dislocation loops. Segments of these loops glide down to SiGe/Si interfaces causing misfit dislocations to arise at interfaces in the heterolayers. Misfitdislocations are formed in directions parallel to and perpendicular to the <110> edge of the implanted region. Dislocations propagate out to a distance of ∼100-150 nm past the edge of the implant in the case of Si0.9Ge0.1/Si layers of sub-critical thickness. The origin and behavior of these defects is discussed.
Defect Growth Interruption Phenomena Related to Impurity Atoms in Growing Multilayer Si-Si1−x Gex Systems Deposited by APCVD
Authors: Babanskaya I. , Lippert G. , KrÜger D. , Methfessel M. , Morgenstern G. , Morgenstern T.
Published: March 2011

The present paper examines conditions which can lead to generation or blocking of structural defects as observed in the deposition of the Si-Si1−x Gex heterostructures prepared by conventional AP CVD. The lowering of the epitaxial temperature can lead to a breakdown of the epitaxial growth and to a generation of defects such as dendritically grown polycrystalline inclusions. Their generation depends on the moisture and oxygen content in the gas mixture. Fast cooling during growth of the underlying buffer layer leads to defect growth interruption and is attributed to the influence of hydrogen adsorption / desorption. A similar defect growth blocking has been found by addition of diborane to the gas mixture during CVD deposition.
Diffusion of Ge Along Grain Boundaries During Oxidation of Polycrystalline Silicon-Germanium Films
Authors: Edwards W. J. , Tsutsu Hiroshi , Ast D. G. , Kamins T. I.
Published: March 2011

Polycrystalline silicon-germanium alloys with compositions between 5 and 30% Ge were wet oxidized in pyrogenic steam with TCA at 700°C. TEM showed that the columnar structure and grain size, ∼500Å, were independent of composition and did not change during oxidation. Both energy dispersive x-ray spectroscopy (EDS) in a UHV STEM and RBS indicate that for low Ge containing films (≤20% Ge), Ge is rejected from the growing oxide, whereas for films with a greater Ge concentration, some Ge is incorporated in the oxide. In low Ge containing alloys, the average Ge profile was determined by RBS and the local Ge distribution was determined by EDS from the oxide interface to about 500Å deep into the alloy. A Ge rich layer was observed at the oxide/poly-SiGe interface. The Ge concentration at the grain boundaries was found to be at least three times higher than that in the grains. The mean diffusion length of Ge along the grain boundaries, measured in cross-section by EDS, was about 300Å, corresponding to an effective diffusivity of about 6×10−16 cm2/s. Analysis of RBS profiles yielded an average effective diffusivity of ∼1.3×10−14 cm2/s. Both diffusivity values suggest that Ge rejected from the oxide growth front diffuses along grain boundaries since the bulk diffusivity of Ge in Si at 700°C is on the order of 10−22 cm2s/s.
Formation of Extrinsic Defects at the Amorphouscrystalline Interface in Ion-Implanted Silicon
Authors: Seibt M. , Imschweiler J. , Hefner H.-A.
Published: March 2011

We have used high-resolution electron microscopy to examine structural changes in the amorphous - crystalline interfacial region in Ge implanted silicon due to annealing at 450°C. We observe the removal of strain in the crystalline part of the interface and a strong decrease of interfacial roughness due to annealing. In addition, we observe the nucleation of interstitial type extended defects in the crystalline region beneath the interface. These grow into {113} - stacking faults during subsequent solid-phase epitaxial regrowth. By measuring the size and density distribution of these defects we estimate the concentration profile of silicon self-interstitials in the crystalline substrate of implanted silicon.
On In-Situ Study of Dislocation/Grain Boundary Interactions Using X-ray Topography and Tem
Authors: Baker Ian , Liu Fuping
Published: March 2011

The advantages and disadvantages of in-situ straining using both synchrotron x-ray topography and transmission electron microscopy for examining dislocation/grain boundary interactions are compared and examples given of the use of each technique. For x-ray topography, studies on ice polycrystals are discussed. Ice is well-suited for x-ray topographic studies since it has both low absorption and can be produced with a low dislocation density. Stress concentrations have been observed at grain boundaries in ice which are partially relieved by generation of 1/3<1120> dislocations. Interestingly, grain boundary generation of dislocations completely overwhelms lattice generation mechanisms. Examples of transmission electron microscope in-situ straining studies include dislocation/grain boundary interactions in L12-structured and B2-structured intermetallics. Slip transmission across grain boundaries by dislocations gliding ahead of an advancing crack is a principal feature of these studies. A significant advantage of the such studies is their inherently high resolution. However, the dislocation behavior is dominated by the inherent thinness of the specimens.
Structure-Property Relationship of Metal-Ceramic Interfaces Produced by Laser Processing
Authors: De Hosson J.Th.M. , Zhou X.B. , Burg M. Van Den
Published: March 2011

A novel process was developed to firmly coat an aluminium alloy, A16061, with α-A12O3 by means of laser processing. In this approach a mixture of SiO2 and Al powder was used to inject in the laser melted surface of aluminium. A reaction product α-A12O3 layer of a thickness of 100 μm was created which was well bonded to the aluminium surface.Various interfaces, A1/α-A12O3, Al/mullite and α-A12O3/;mullite, were studied by conventional transmission electron microscopy (CTEM) and high resolution electron microscope (HREM). It turns out that the presence of the A1/;muilite interface may be essential to form a well bonded oxide layer and the high Si-content α-A12O3 intermediate layer may be wetted better by liquid Al.
Atomic Scale Structure and Chemistry of Interfaces by Z-Contrast Imaging and Electron Energy Loss Spectroscopy in the Stem
Authors: Mcgibbon M.M. , Browning N.D. , Chisholm M.F. , Pennycook S.J. , Ravikumar V. , Dravid V.P.
Published: March 2011

The macroscopic properties of many materials are controlled by the structure and chemistry at grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. The high-resolution Z-contrast imaging technique in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition can be interpreted intuitively. This direct image allows the electron probe to be positioned over individual atomic columns for parallel detection electron energy loss spectroscopy (EELS) at a spatial resolution approaching 0.22nm. In this paper we have combined the structural information available in the Z-contrast images with the bonding information obtained from the fine structure within the EELS edges to determine the grain boundary structure in a SrTiO3 bicrystal.
The Slip Transfer Process Through Grain Boundaries in HCP Ti
Authors: Shirokoff J. , Robertson I.M. , Birnbaum H.K.
Published: March 2011

Information on the mechanisms of slip transfer across grain boundaries in an HCP α-Ti alloy has been obtained from deformation experiments performed In situ in the transmission electron microscope. Initially, lattice dislocations are accommodated within the grain boundary until a critical local dislocation density is reached. The boundary then responds by activating slip in the adjoining grain on the slip system experiencing the highest local resolved shear stress and producing the residual grain-boundary dislocation with the smallest Burgers vector. Slip on secondary slip systems may be initiated provided they reduce the magnitude of the Burgers vector of, or eliminate, the residual grainboundary dislocation. The selection rules used to predict the slip system activated by the grain boundary are the same as apply in ordered and disordered FCC materials.
The Interaction Between Dislocations and Lamellar Grain Boundaries in Pst γ Tiai
Authors: Rao S. , Woodward C. , Hazzledine P.M.
Published: March 2011

In lamellar TiAl the flat-plate geometry of the grains, the barriers to deformation across the grain boundaries and the coherency stresses all contribute to a marked anisotropy in the yield and fracture stresses of the material. Both yield and fracture occur at low stresses when the deformation is within the lamellae (soft mode) and they occur at high stresses when the deformation crosses the lamellae (hard mode). The anisotropy is enhanced by a new effect which can soften the soft mode and harden the hard mode: the geometry of the lamellar boundary produces degeneracies in the planar fault energies at the interfaces which enhance the mobilities of dislocations on these interfaces. These degeneracies modify the core structure of dislocations on or near the interfaces, consequently soft mode dislocations can dissociate widely and move more easily when their glide plane is contained in the interface. Hard mode dislocations can substantially reduce their core energies when intersecting a γ/γ interface, and subsequently become immobilized, by cross slipping on to the interface plane. This paper presents a discussion of the geometry and relative energies of the γ/γ interfaces using elements of Bollman O-lattice theory. In order to investigate the influence of the interfaces on dislocation core structure we have fit an empirical Embedded Atom Method (EAM) potential to the structural and elastic properties of bulk L10 TiAl. The mobility and core structure of the twinning dislocation at the 180° interface and the perfect, 1/2<110] screw dislocation at the 60° and 120° interfaces were calculated using molecular statics within the EAM. We have also studied the influence of one and two atomic step ledges on dislocation mobility in the 120° interface. We find in general that dislocations are more glissile on the γ/γ interfaces, as compared to bulk TiAl and that ledges are weak barriers to dislocation glide. The interfaces themselves are strong barriers to dislocation motion in the hard mode. We find that the 1/2<110] screw dislocations gliding on conjugate {111} planes are trapped at these interfaces, as a result of lower core energies for screw dislocations lying in the interface.
Misfit Dislocations at Metal/Ceramics Interfaces
Authors: Gutekunst G. , Mayer J. , RÜHle M.
Published: March 2011

The atomistic structure of the coherent regions of Nb/A12O3-interfaces of various substrate orientations have been determined by high-resolution electron microscopy (HREM). The substrate surfaces were parallel to (0001)A12O3, (0110)A12O3, (2110)A12O3 and (0112)A12O3. In all cases, the Al sublattice of the A12O3 substrate is continued in the first Nb layer at the interface. This principle results in the unique orientation relationship.

The Burgers vectors of the misfit dislocations and the geometry of the dislocation network of all Nb/A12O3-interfaces have been determined by HREM. All Burgers vectors are lattice vectors. Thus no coherent regions with different atomistic structures are found. The Burgers vectors are of the type 1/2<111>. These Burgers vectors correspond to the Burgers vector of bulk dislocations. All Burgers vector components which do not accommodate the lattice mismatch are compensated in the networks. The network geometry is rectangular for the following interface planes: (0110)A12O3||(112)Nb (orientation 2) and (0112)A12O3||(001)Nb. If the interface is parallel to (0001)A12O3 and (111)Nb the geometry is rhombic.

The core structure of misfit dislocations of orientation 2 with line direction ξ1=[110] are calculated with an atomistic model and a continuum approach. The calculated core structures are in good agreement with the experimental HREM-micrographs of misfit dislocations of orientation 2.
Computer Simulation of Creation of Dislocations in Titanium Small Crystals
Authors: Ida Junji , Doyama Masao
Published: March 2011

Edge dislocations were created on a basal plane (0001) in a small titanium single crystal whose surfases are (0001), (0001), (1010), (1010), (1210) and (1210) by use of n-body embedded atom potentials and molecular dynamics.