bluuebunny/crossref_metadata_2025 huggingface dataset:
In-Situ Monitoring of the Initial Growth of a-C:H Films by AES
Authors: Tschersich K.G.
Published: March 2011

Amorphous hydrogenated carbon films are deposited by direct ion beam deposition onto Si and W substrates at room temperature. Simultaneously, the sample surface composition is measured by Auger electron spectroscopy. The results indicate a sharp interface between film and Si and the formation of a W2C layer between film and W. The in-situ measurements are compared with sputter depth profiles. It is found that the former ones give insight into film growth processes, that is unattainable by sputter profiling.
Mechanical and Chemical Characterization of a Metal-Bioceramic Interface
Authors: Filiaggi Mark J. , Coombs N. A. , Pilliar R.M.
Published: March 2011

Plasma sprayed Hydroxyapatite (HA) coatings are applied to metal prostheses to allow for implant fixation through chemical bonding of the coating with surrounding bone tissue. Without a well-adhering coating, this fixation is threatened. Thus, a thorough characterization of the metal / ceramic interface is necessary. This study used a novel composite short bar interfacial fracture toughness technique with high resolution electron spectroscopic imaging to examine Ti-6AI-4V plasma spray coated with 100μm of HA. For this system, an interfacial fracture toughness value of 1.31 +/− 0.08 MPa·m1/2 was obtained, with a corresponding tensile adhesive bond strength of 6.7 +/− 1.5 MPa. High resolution ESI revealed distinct phosphorous segregation to the interface and diffusion into the underlying titanium. A 24-hour post-heat treatment at 960°C greatly increased the bond strength at this interface. Observations from ESI suggested that this effect may be due to enhanced diffusion of both phosphorous and calcium into the metal substrate.
Microscopic Characterization of Cosintered Copper/Cordierite Interfaces
Authors: Werckmann J. , Han B.S. , Faerber J. , Humbert P. , Carriere B. , Esnouf C. , Chardon N. , Guille J. , Bernier J.C.
Published: March 2011

Copper and sol-gel processed cordierite were cosintered in oxidizing atmosphere using an eutectic bonding technique. Firing at low and high heating rates leads to interfaces which present different macroscopic properties. These interfaces were therefore investigated on a microscopic scale by SEM, XPS and STEM analyses. Copper diffusion as well as strong chemical and structural modifications were observed in the interface region. Although these interfaces have good adhesion properties, there was no evidence for the formation of some interfacial copper compound.
Calculation of Local Elastic Constants at a Metallic Grain Boundary
Authors: Kluge M. D. , Lutsko J. F. , Wolf D. , Phillpot S. R.
Published: March 2011

A new atomistic-simulation method for calculating the full local elastic-constant tensor in terms of local stress and local strain for inhomogeneous systems is described. Results of simulations of an isolated high-angle twist grain boundary are presented. A dramatic reduction in resistance to shear parallel to the grain boundary is observed, and its relation to structural disorder is discussed.
Dynamic Control of Water Concentration to Prolong The Life Time of Encapsulated Electronic Devices in High Humidity Environments
Authors: Kim I. U. , Troyk P. R. , Anderson J. E.
Published: March 2011

Silicone resins and gels have been used extensively for IC protection. Reduction of interfacial moisture and ionic contamination is considered crucial to device reliability.

The present research has revealed an interesting phenomenon. Prolonged lifetime was obtained for comb pattern samples using a non-conventional encapsulation method. In order to increase specimen sensitivity to interfacial moisture, samples were contaminated prior to encapsulation. Three groups of contaminated samples encapsulated with polysiloxane were produced. Group I was encapsulated with a polymer/CaCl2/polymer/substrate structure. The structure of group II consisted of only the polymer on the contaminated substrates. Group III was encapsulated with a CaCl2 embedded polymer/polymer /substrate structure. Following exposure at 85°C, 100−10 amperes after 2,000 hrs, with no visible corrosion. Group II and III samples showed visible corrosipn after 390 to 470 hrs with leakage current of the order of 10−5 amperes. Direct measurement of RH at the polymer/substrate interface and water sorption experiments were done to explain the mechanisms of these packaging structures.

The experimental results suggest that a desiccating multilayer coating can maintain low interfacial water concentrations. During exposure to high external RH, water from the surroundings diffuses through the top layer, producing an interlayer consisting of a solid CaCl2 and a CaCl2-saturated solution. Until all of the salt dissolves, the water chemical potential of the saturated solution defines the water content at the polymer/substrate interface. Hence the RH at the polymer/substrate interface was maintained below that required to dissolve the residual surface contamination for a longer time than by conventional encapsulation. This technique could be useful to reduce the dependence of IC reliability upon pre-encapsulation cleaning.
Stress Measurement in Spin Coated Polyimide Films Using Time Average Holographic Interferometry
Authors: Maden Michele A. , Farris Richard J.
Published: March 2011

It is proposed that the stresses in a thin polyimide film can be analyzed using the solution to the problem of a vibrating membrane. The polyimide membrane is supported on a copper substrate and excited with a small speaker. The membrane vibrates uniformly in response to its resonant frequencies. The vibration pattern will be recorded using holographic interferometry. The biaxial stress in the film is calculated from the measured characteristic frequency, the density of the material, and the mode of vibration. This technique may also be used to determine the Poisson's ratio of the film by combining uniaxial and biaxial stress analyses.
Polyimides for Passivation of VLSI Circuits
Authors: Andel Maarten A. van , Gootzen Wil F.M.
Published: March 2011

From a processing point of view polyimides are attractive materials for use as interlayer dielectric and as passivation coating on ICs. For plastic encapsulated devices they can also improve on the thermomechanics, thereby enhancing yield and reliability. We simulated the thermomechanical behaviour of such a device with finite element calculations. Based on these simulations the commercial product PIQ-L100 was chosen as a model polyimide to study some important physical and chemical parameters. The results from investigating internal stress, molecular orientation and imidization kinetics can be used to optimize polyimide processing and to obtain the desired coating characteristics.
Passivating Organic Coatings with Silicone Gels: The Correlation Between the Material Cure & its Electrical Reliability
Authors: Wong C. P.
Published: March 2011

Silicone gels are becoming some of the most accepted protective coatings for VLSI integrated circuits due to their excellent electrical, thermal, and soft gel-like nature and properties, as well as their ultra-purity and ability to protect IC devices against severe environments. Recent studies indicate that proper IC Chip surface protection with high performance silicone gels in low-cost, non-hermetic plastic packaging might well replace the conventional hermetic ceramic packaging. This paper describes the use of the soft silicone gels and coatings in IC devices. It also describes the correlation between the material cure temperature and cure time versus their adhesion and electrical reliability during 85°C, 85% RH and bias accelerating testing.
Moisture Intrusion in Sio2/Epoxy Interfaces
Authors: Takahashi Ken M.
Published: March 2011

In-situ interfacial impedance measurements were used to study the effects of moisture at 80 ° C on the interface between oxidized silicon and a diglycidyl ether of bisphenol A (DGEBA) epoxy cured with diethylene triamine (DETA). Using two electrode configurations, admittances attributable to bulk and interfacial conduction processes were distinguished. Bulk impedance measurements followed Randles behavior; conduction in the bulk epoxy was ionic, and was diffusion controlled at low frequencies. Equivalent circuit models were used to demonstrate that an apparent interfacial conduction process was caused by distributed current leakage into the silicon subphase, not a true interfacial conduction path that would indicate water adsorption or interfacial aggregation. However, transitions in diffusivity and bulk epoxy permittivity behavior above a 70–80% relative humidity threshold were observed. Effective epoxy permittivity (εc) jumped to values indicative of a water cluster induced Maxwell-Wagner relaxation. The humidity threshold corresponds to a level that has been associated with adhesion loss in epoxies. It appears that epoxy adhesion losses result from bulk epoxy property changes at high humidity rather than interfacial bond displacement or delamination.
The Processing and Properties of Multilayer Interconnection Structures Using Thermoset Films Derived from Bisbenzocyclobutene.
Authors: Townsend P. H. , Burdeaux D. C. , Hahn S. F. , Thomsen M. , Carr J. N.
Published: March 2011

Multilayer interconnection structures incorporating a novel polymeric dielectric derived from a bis-benzocyclobutene(bis-BCB) monomer have been fabricated. This paper discusses the processing conditions for the construction of these circuits and describes electrical characteristics of the dielectric layers. The relative dielectric constant of the BCB film was 2.7. Thermal cycling produced no significant change in the conductance of three level metal via chains through two layers of the polymer.
Silicon Hybrid Multi-Chip Modules
Authors: Trigg Alastair D.
Published: March 2011

The Research Initiative on Silicon Hybrids (RISH), is one of several National Electronics Research Initiatives created under the auspices of the UK Department of Trade and Industry. Its aims are to investigate the merits of silicon hybrids, evaluate their performance and develop the technology necessary for their implementation. The paper describes the design and fabrication of silicon hybrids using thin film metal-polyimide interconnect. Several chip attach options are considered. The merits of the technology are illustrated using functional circuit demonstrators.
SiO2-TiO2-ZrO2 Gel Glasses - Reaction Kinetics and Properties
Authors: Beier W. , Frischat G. H.
Published: March 2011

Solutions have been prepared containing silicon ethoxide, titanium butoxide, and zirconium propoxide as metal organic compounds. Additions of water (for hydrolysis), solvents (ethanol, formamide), and hydrochloric acid (as a catalyst) have been varied systematically. The reaction kinetics of the hydrolysis and condensation steps in these mixtures have been studied by measuring viscosity and 29Si NMR data as a function of time. After gelling, the products have been dried and then converted to glassy materials by firing. Temperatures well below 1000 °C have been used for that. Glasses from the title system have been obtained both in bulk and in thin film form. Properties like density, specific surface, and hardness have been investigated and are reported as well.
Hafnium Metallo-Organic Films and Gels Produced by Sol-Gel Processing
Authors: Gagliardi Charles D. , Berglund Kris A.
Published: March 2011

Metallo-organic materials are often used as precursors for highly refractory oxides and hightemperature composites. The feasibility of producing hafnium metallo-organic films and gels by sol-gel techniques is demonstrated in the present study. Since hafnium alkoxides are not commercially available, their preparation is an obstacle in the development of their sol-gel processing applications. A common synthesis technique was used to produce hafnium isopropoxide, which was subsequently hydrolyzed under acid catalyzed conditions to produce films and gels. The films were prepared by spin casting and remained optically transparent. Initially, the gels were also optically transparent, but became translucent upon drying. Raman, IR, and light scattering spectroscopies were used to characterize this sol-gel process, and it is compared with the analogous processing of titanium and zirconium alkoxides.
Ceramic Processing using Inorganic Polymers
Authors: Lannumti John J. , Schilling Christopher H. , Aksay Ilhan A.
Published: March 2011

Inorganic polymers are used in the formation of green compacts via sedimentation of colloidal alumina suspended in chloroform. Polymers containing highly polar components tend to produce constant density profiles of greater than 55% density, while those containing nonpolar, reactive components produce profiles with a large gradient in packing density. Density profiles describing the sedimentation behavior versus time and the final dried density of the compacts are generated via the use of gamma-ray densitometry. These polymers have the potential not only to increase green compact density but also to reduce weight losses due to “burnout” and subsequent sintering requirements by pyrolyzing to a ceramic phase.
Conversion of Alkoxide Solutions to Oxides: Evaporation of Products
Authors: Lipeles R. A. , Coleman D. J.
Published: March 2011

The evaporation of organic by-products released during drying of 1-mm thick silicon tetramethoxide gels was analyzed using gas chromatography. The evaporation kinetics of methanol depended on the drying rate achieved by flowing dry air over the gel. For drying at flow rates less than 50 cm 3/min, exponential kinetics were observed initially with a long time constant (about 100- to 400-min). For drying rates greater than 70 cm3/min, diffusional (t−1/2) kinetics were observed initially. Cracking of the gel during drying was used to indicate the degree of stress. At low drying rates, minor cracking was observed near the edges of the gel. At high flow rates, extensive cracking was observed in samples that exhibited early t−1/2 kinetics. Monitoring the kinetics of drying is essential to optimizing the drying conditions to minimize stress and cracking in gels.
Processing of Crystalline Li(Nb, Ta)O3 Films with Preferred Orientation Through Metal Alkoxides
Authors: Hirano Shin-Ichi , Kato Kazumi
Published: March 2011

LiNbO3 and LiTaO3 are very attractive and useful materials, which have been applied to piezoelectric and electro-optic devices. The authors have synthesized the stoichiometric crystalline fine powders and films of LiNbO3 at temperatures as low as 250°C by the controlled hydrolysis of double alkoxide solutions; and this method was used to prepare Li(Nb, Ta)O3 solid solution films with and without the preferred orientation. Water used during the processing played an important role in the low-temperature crystallization and the elimination of free carbon in the films. The water for the partial hydrolysis affected the properties of alkoxide solutions for dip-coating, and the morphologies of crystalline films. Water in a mixed gas flow with oxygen during calcination accelerated the crystallization of the alkoxy-derived films at low temperatures.
Temperature Measurement for Microwave Processing of Advanced Ceramics
Authors: Meek T. T. , Park S. S. , Nehls M. A. , Kim C. W.
Published: March 2011

The measurement of temperature in a microwave field is critical to the understanding of many phenomena which occur in materials heated in such an environment. Researchers have employed many techniques [1–4] to measure temperature in an electromagnetic field. This work examined three approaches: the use of a thermocouple, an IR meter, and a d. c. resistance technique.
Characterization and Processing of CVD Powders for Fabrication of Composite and Compound Ceramics
Authors: Hori Saburo , Shigaki Yoshiki , Hirata Yoshihiro , Yoshimura Masahiro , Sōmiya Shigeyuki
Published: March 2011

Two-component oxide powders were prepared in the systems Al2O3-ZrO2. Al2O3-TiO2. and Al2O3-SiO2 by a CVD (chemical vapor deposition) technique using a combustion flame for the purpose of fabricating respective composite or compound ceramics. The CVD powders were spherical and ultrafine (av. 30–70 nm) with log-normal size distribution, and exhibited either very homogeneous or nanoheterogeneous structure and crystallographic metastability in phases and solid solutions. By starting from these CVD powders, not only uniform and excellent microstructure was achieved in the sintered products, but also better sinterability and novel microstructure became possible owing to the metastability which reflected the formation mechanism of two-component powders at high temperatures. CVD powders, which were previously considered difficult to sinter, proved to be excellent starting materials for fabrication of composite and compound ceramics when improved processing techniques were applied.
Zero-Shrinkage Whisker Fraction in Ceramic Matrix-Ceramic Whisker Composites
Authors: Holm Elizabeth A. , Cima M. J.
Published: March 2011

A Monte Carlo computer simulation that percolates soft-core, pseudographic whiskers in a discrete matrix has been developed, and two- and three-dimensional whisker percolation thresholds were determined for various whisker aspect ratios. The percolation thresholds were found to agree with the predictions of the excluded volume theory of percolation; moreover, the thresholds were found to coincide with the zero-shrinkage whisker fraction in ceramic matrix-ceramic particle composites.
Densification Behavior of Al2O3 Powders Containing ZrO2 Inclusions
Authors: Sudre O. , Lam D. C. C. , Lange F. F.
Published: March 2011

Densification experiments using ZrO2 single-crystal particles in an Al2O3 powder matrix were performed to examine the microstructural changes produced by constrained densification. Observations showed the formation of large, lowdensity regions within a denser material network. Enlargement of pores by desintering of necks between grains was observed during grain coarsening within these low-density regions. This pore opening behavior was also investigated in a model experiment.
Mechanical Properties of Colloidal Gels
Authors: Shih W.-H. , Liu J. , Shih W. Y. , Kim S. I. , Sarikaya M. , Aksay I. A.
Published: March 2011

A colloidal suspension can be either dispersed or flocculated depending on the interaction between the colloidal particles. If the interaction is repulsive, particles can relax to the minimum of the potential due to their neighboring particles, and the system can reach an equilibrium dispersed state. In the case of attractive interaction, particles form aggregates that settle to the bottom of the container. As the concentration of particles is increased, the overcrowding of the aggregates produces a continuous network throughout the suspension before they settle and a colloidal gel is formed. A major difference between a colloidal gel and a colloidal suspension is that the gel can sustain finite stress and is therefore viscoelastic. Previously we studied the storage modulus and the yield strain of boehmite gels and found that they are related to the particle concentration in a power-law fashion [1]. Similar scaling behavior of the shear modulus was found for other colloidal particulate networks by Buscall et al. [2]. We developed a scaling theory [1] which successfully explains the experimental results on boehmite gels. The theory further predicts that there can be two types of power-law behavior depending on the relative elastic strength of the clusters to that of the links between clusters within the gel network. Furthermore, there can be a crossover from one type of behavior to the other as the particle concentration is varied.
Structural Problems and Non Stoichiometry in Thallium, Bismuth, and Lead Cuprates
Authors: Raveau B. , Michel C. , Hervieu M. , Groult D. , Provost J.
Published: March 2011

An over view of the crystal chemistry of the layered bismuth, thallium and lead cuprates is presented here. The classification of these oxides is examined, and the problems of non stoichiometry, especially of extented defects and incommensurability of the structures, are discussed in connection with the superconducting properties of these materials. A particular attention is paid for the role of the lone pair cations in the structural properties of these oxides.
Single Cu-O Layer Bismuth Strontium Cuprates: Crystal Growth and Electronic Properties
Authors: Schneemeyer L. F. , Waszczak J. V. , Fleming R. M. , Martin S. , Fiory A. T. , Sunshine S. A.
Published: March 2011

The growth of single crystals of Bi2+xSr2−yCuO6±δ from alkali chloride fluxes, typically sodium chloride is reported. Electronic properties of the resultant crystals are controlled by the melt composition and the partial pressure of oxygen during growth. Superconducting crystals with Tc's near 10K are obtained under low oxygen partial pressures from melts which are strontium-rich. Measurements of transport, tunneling and magnetoconductivity in nonsuperconducting crystals show two-dimensional localization within the CuO2 planes. Superconductivity occurs only when transport perpendicular to the planes gives rise to extended states in three dimensions.
Hrem on Grain Boundaries in Oxide Superconductors
Authors: Zandbergenl H.W. , Tendeloo G. van
Published: March 2011

High resolution electron microscopy has been carried out on grain boundaries in a number of superconducting oxides: YBa2Cu3O77−∂, LaCaBaCu3O7−∂, Bi2Sr2CanCun+1O2n+6+∂, and Pb2(Sr, Ca)3−xAxCu2+nO6+2n+∂. In general no amorphous material or another phase is observed at the grain boundaries. It is argued that the low critical currents in these polycrystalline materials are caused by the atomic structure of (001) interfaces at grain boundaries and concerning YBa2Cu3O7 and LaCaBaCu3O7−∂ by the intercalation of CuO layers starting from the grain boundaries.
Analysis of Superconducting Oxide by 7 MeV Alpha Particle Backscattering Analysis
Authors: Yonezawa Hiroki , Hidaka Yoshikazu , Suzuki Minoru , Shigematsu Toshio
Published: March 2011

High energy Ion backscattering analysis in combination with recently-developed resonance scattering analysis Is described, with a stress on precise and quantitative oxygen analysis and its successful application to the characterization and quality estimation of high Tc oxide superconductors. Particularly, the present status of high energy ion backscattering analysis, the review of analytical results for YBa2Cu3O7−x, the estimation of composition and crystalline quality of (La1−xSrx)2CuO4 by 7 MeV alpha particle backscattering analysis are described.
On the Origin of the Structural Modulation in the Bi Cuprates As Derived from 3d-Metal Substituted Phases
Authors: Tarascon J. M. , LePage Y. , McKinnon W. R. , Tselepis E. , Barboux P. , Bagley B.G. , Ramesh R.
Published: March 2011

A substitution for Cu by a 3d-metal (Fe, Co, Mn) in the superconducting Bi phases (Bi2Sr2Can−1CunOy; n = 1,2 and 3) has led to the discovery of new phases. These 3d-metal substituted phases are non-superconducting and, in contrast to the Cu-based phases, they exhibit a structural modulation that is commensurate. Single crystal x-ray studies were performed on the Bi2Sr3Fe2Oy, Bi2Sr2CoOy and Bi2Sr2MnOy compounds. A result, in common, is that the modulation is caused by the periodic insertion of a row of oxygen atoms in the Bi layers and this results in a corrugated-like slab structure. The Bi-O layers can be described as composed of alternating rocksalt-type and oxygen deficient perovskite-type blocks. For the Fe (n=2) phase the Bi atoms form ribbons (chains) in the ab plane. This is in contrast to the n=1 Co or Mn phases for which a disorder at the oxygen position is observed. Although the extra oxygen in the Bi-O layer could account for the doping mechanism in the high Tc Bi-phases, cation non-stoichiometry may also beimportant.
Identifying the Pairing Mechanism in High-Tc Superconductors
Authors: Goodenough J.B. , Manthiram A. , Zhou J.
Published: March 2011

It is argued that the origin of the high transition temperatures observed in Ba1−xKxBiO3 and the copper-oxide superconductors with perovskite-related structures is due to two factors: (1) overlap of a partially filled σ* band of primarily cation character and a π or π* band of mostly O-2pπ parentage permits charge transfer between cation and anion subarrays with oxygen-atom displacement perpendicular to a M-O-M bond axis and (2) bondlength mismatch places the M-O-M bondlength under a compressive or tensile stress. Relief of a compressive stress by the bending of a M-O-M bond from 180° introduces a strong electron-lattice interaction with holes; a 180° Cu-O-Cu bond allows strong electronlattice coupling with electrons of a Cu2+/+ redox couple, but not with holes in a Cu3+/2+redox couple.
Comparison of the Hole Conductivities in Ceramic Cuprate Semiconductors and High-Tc Superconductors, as Reflected in the Difference between Oxygen and Copper Madelung Site Potentials
Authors: Metzger Robert K. , Torrance Jerry B.
Published: March 2011

The Madelung energies of 18 cuprates and 1 nickelate with sheets or chains of Cu and O have been computed, along with the relevant Madelung site potentials for O and Cu. The difference between these site potentials has been shown to correlate extremely well with the conductivity of these cuprates: only if the site potential difference is intermediate can the holes (the presumed charge carriers) move more easily between Cu and O sites in the CuO2 sheets.
Composition of Superconducting La2CuO4+δ a Superconductor Doped by excess Oxygen Defects
Authors: Dabrowski B. , Hinks D. G. , Jorgensen J. D. , Richards D. R.
Published: March 2011

We have studied mixed-phase samples of bulk LazCuO4 using neutron powder diffraction, thermogravimetric analysis and resistivity measurements. Samples fired at 950°C and slowly cooled form in the K2NiF4 structure with CuO impurities for z<2 and La2O3 impurities for z>2. Neither La-vacancies nor stacking defects were found. The bulk resistivity of the samples show semiconducting behavior which is shorted at 38K by small amounts of superconducting material. The superconductivity is due to the presence of an oxygen-rich phase with stoichiometry La2CuO4.08. The occurrence of superconductivity in pure La2CuO4.08 with the same Tc as observed in the doped La1.85 Sr0.15CuO4 indicates that the excess oxygen provides the same level of doping as metal-ion substitution.
Direct Observation of Intermixing in GAAS/AIAS Multilayers After Very Low-Dose Ion-Implantation
Authors: Bode M. , Ourmazd A. , Rentschler J.A. , Hong M. , Feldman L.C. , Mannaerts J.P.
Published: March 2011

We combine chemical lattice imaging and digital vector pattern recognition to study quantitatively, kinetic intermixing in GaAs/AlAs multilayers. We thus obtain, with atomic plane resolution and near-atomic sensitivity, composition profiles across each interface of a multilayer stack before and after ion-implantation. Our results show significant intermixing even when only one 320 keV Ga+ ion is implanted at 77 K into each 2000 A2 area of the interface. This corresponds to an incident ion dose of 5×l012/cm2.

The intermixing is not uniform along the interface. At each interface, we observe more intensely intermixed regions, whose widths correspond to those created by the damage track of a single implanted ion, as expected from Monte-Carlo simulations. It thus appears that we can directly image intermixing due to single energetic ions implanted into the multilayered GaAs/AlAs structure.
Effect of Carbon on Ion Beam Mixing of Fe-Ti Bilayers
Authors: Hirvonen J-P. , Nastasi M. , Lappalainen R. , Sickafus K.
Published: March 2011

The influence of implanted carbon on ion beam mixing of a Fe-Ti system was investigated. Carbon was introduced into bilayer samples by implanting 13C isotopes. The implantation energies were selected to set the mean range of carbon ions in either the iron or titanium layer. The effect of implanted carbon on 400 keV Ar ion mixing in the temperature range from 0 to 300 °C was studied using Rutherford backscattering spectroscopy at the energy of 5 MeV. Changes in carbon concentration profiles were probed utilizing the resonance of the nuclear reaction l3C(p,y)14N at the proton energy of 1.748 MeV. The measurements revealed that mixing was not affected by carbon implanted into the titanium layer. However, carbon in the iron layer remarkably retarded mixing at all temperatures investigated. Significant changes in carbon depth distributions were observed only when the sample with implanted carbon in the iron layer was mixed at 300 °C. These result are explained in terms of the enhanced mobility of carbon in an evaporated iron film which allows segregation to the interface. At low temperatures, however, vacancy-carbon interaction in iron may have a contribution to the retarded ion beam mixing.
Ion-Beam Mixing and Tribology of Fe/B Multilayers
Authors: Hu Renyuan , Rehn L. E. , Fenske G. R. , Baldo P. M.
Published: March 2011

Interdiffusion of Fe and B trilayer specimens during 1-MeV Kr+ bombardment was studied using Rutherford backscattering and electron microscopy. The square of the interdiffusion distance during mixing at 300°C was found to depend linearly on the irradiation dose. Arrhenius behavior with an apparent activation enthalpy of 0.7 eV was observed for the mixing between 200 and 500°C. Electron microscopy of ion-beam mixed multilayer specimens revealed that two crystalline compounds, Fe2B and Fe3B, formed during bombardment at 450°C, while two different amorphous Fe/B phases formed at 300°C. Substantially improved adhesion and reduced friction were observed for Fe/B multilayers ion-beam mixed onto M50 steel substrates at 450°C.
Molecular Dynamics Simulations of the Interactions of Excited Electrons
Authors: Mazzone A. M.
Published: March 2011

In this work the processes of electron-electron interaction taking place in a highly excited electron gas are analyzed on the basis of molecular dynamics simulations. The time evolution of the system is described by using either classic mechanics or a quantum mechanical representation. New aspects of the collective behaviour of the particles are born out by the simulations.
Molecular Dynamics Simulations of Ionized Cluster Beam Deposition
Authors: Hsieh Horngming , Averback R.S. , Benedek R.
Published: March 2011

Fully dynamical computer simulations have been used to study the physical mechanisms of ionized cluster beam deposition. Clusters containing 92 atoms were directed at <001> surfaces with energies per cluster atom ranging from one sixth to three times the cohesive energy of the target. Simulation events employed either Lennard-Jones or Embedded Atom Method potentials. The atoms in the cluster appear to undergo local melting on impact with the substrate. Higher cluster energy increases the spreading of cluster atoms on the substrate and improves epitaxy, but it also increases interdiffusion and produces point defects.
Analysis of Scanning Tunneling Microscope Topographs of Graphite Surfaces Roughened by Ar+ Ion Bombardment
Authors: Eklund Elliott A. , Williams R. Stanley , Snyder Eric J.
Published: March 2011

The scanning tunneling microscope (STM) has been used to investigate graphite surfaces roughened by 5 keV Ar+ ion bombardment. The (0001) surfaces of several samples were etched with the same total ion dose but with different sputter rates for each surface. STM images taken after sputtering show that the roughness of the sputtered surfaces depended on the sputter rate and that the surface topography of each sample appeared self-similar over a large range of length scales. These experimental observations agree with predictions of the recently proposed Shadow Model. The two dimensional height-height correlation function is utilized as a means of quantitative analysis for STM topographs of sputtered surfaces.
Electron Beam Induced Nanometre Hole Formation and Surface Modification in Al, Si And MgO
Authors: Bullough Tim J. , Humphreys C. J. , Devenish R. W.
Published: March 2011

A wide variety of materials which are normally undamaged when exposed to a lOOkeV electron beam in a conventional transmission electron microscope can be modified on a nanometre scale by the high current density electron probe in a dedicated scanning transmission electron microscope (STEM). A stationary 100keV STEM electron probe can produce holes typically l-5nm diameter through crystalline Al, Si and MgO tens of nanometres in thickness, while a scanned electron beam can smooth surfaces on an atomic scale.

In Al the stationary electron probe in the STEM produces a row of facetted voids along the irradiated volume. The voids grow initially inwards from the electron exit surface, with each void typically 4nm in diameter and 12-24nm in length, separated by equal distances from one another. In contrast, continuous holes 1.2-1.6nm diameter form at the electron exit surface of Si when exposed to the focused electron beam. However, these holes form only at specific randomly distributed points separated from one another by 2-4nm over the surface of crystalline specimens of both n- and p-doped <001> and <111> Si.

Square cross-section holes with widths of about lnm can be formed by the stationary electron probe in MgO crystals. Rastering the probe over a restricted area of MgO initially results in the rapid development of surface islands and channels which are subsequently removed to leave an atomically smooth surface.
Investigation of Oxide/Metal Multilayers for Soft X-Ray Optics Fabricated by Ion Beam Sputterinc
Authors: Kataoka I. , Yoneiitsu T. , Sekine K. , Yaiada I. , Etoh K. , Ito K. , Hoshi N.
Published: March 2011

The dependence of the ordering factor and surface roughness of aiorphous SiO2 and Ni filis fabricated by Dual Ion Beai Sputtering(DIBS) assisted by Ar+ ion boibardient were evaluated. The ordering factor tas defined as a quantity which shows the degree of aiorphousness froi ris value of correlation function of the RHEED pattern. The surface roughness was leasured with a Talystep systei and STM, and the data was evaluated with respect to the spatial wavelength.

For aiorphous SiO2 filis, the surface roughness is strongly correlated with the ordering factor as a parameter of the assisting Ar+ ion energy, and it depends on the fill structure. Siiilar relationship was not observed for Ni filis, because of the traced surface roughness of substrate in the energy region investigated.
Freezing in Silicon at Large Undercooling
Authors: Stolk P.A. , Polman A. , Sinke W.C.
Published: March 2011

Pulsed laser irradiation is used to induce epitaxial explosive crystallization of amorphous silicon layers buried in a (100) oriented crystalline matrix. This process is mediated by a self-propagating liquid layer. Time-resolved determination of the crystallization speed combined with numerical calculation of the interface temperature shows that freezing in silicon saturates at 16 m/s for large undercooling (> 130 K). A comparison between data and different models for melting and freezing indicates that the crystallization behavior at large undercooling can be described correctly if the rate-limiting factor is assumed to be diffusion in liquid Si at the solid/liquid interface.
Pulsed Laser-Induced Melting of Intermediate Cu-Zn Phases
Authors: Follstaedt David M. , Peercy Paul S. , Perepezko John H.
Published: March 2011

We have discovered that the β and γ brasses of Cu-Zn exhibit clearly resolved increases in reflectance upon melting with a 30 ns ruby laser, which allow their melt durations to be readily measured. This system thus offers potential for obtaining quantitative information about the solidification kinetics of metals. We have also found that a heteroepitaxial layer of β' brass is formed on the surface of (ordered) γ brass with 63 wt.% Zn following pulsed laser-induced melting. The β' layer is interpreted to mean that the metastable β phase (bcc) formed on the liquid-solid interface as the γ substrate attempted to regrow, and that β ordered to β' (B2) during cooling. The β formation implies that undercoolings > 16 K were attained during the attempted regrowth of the γ phase.
Metastable Ge-Sn Alloy Layers Prepared by Pulsed Laser Melting
Authors: Chang I.T.H. , Cantor B. , Cullis A.G.
Published: March 2011

Ge has a diamond cubic crystal structure (α) while Sn exists in both the diamond cubic (α) and body centred tetragonal (β) allotropic forms. The solid solubilities between Ge and Sn are very small according to the equilibrium phase diagram. This paper describes an investigation into the manufacture of metastable diamond cubic Ge-Sn alloy layers using pulsed laser melting of evaporated thin films . Cross-sectional and plan-view transmission electron microscopy have been used to characterise the microstructures of the Ge-Sn alloy layers, with alloy compositions determined by energy-dispersive X-ray microanalysis. The metastable diamond cubic Ge-Sn alloy microstructures are discussed in detail as a function of processing conditions.
Condensation of Ultrafine Silica from a Laser-Induced Plume
Authors: Chow G.M. , Strutt PR.
Published: March 2011

The different silica-phase morphologies formed in synthesizing silica-metal matrix composites layers have been studied, using a new evaporation technique, involving rapid condensation of silica from a laser beam induced-ceramic plume. This process occurs within a reactive gas environment (98.5% hydrogen, 1.5% methane), with a heated tungsten filament in proximity to the laser beam-material interaction zone. The silica phase in the composite layers deposited on a nickel substrate exhibited different metastable morphologies, namely, nanometer-size amorphous fibers or linear-chain shape aggregates. There appeared to be a correlation between the morphology of the deposits and the position of the heated tungsten filament. When the tungsten filament was absent, silica was deposited in the form of clusters. In this case, depending on the beam-ceramic target interaction times, there was a shift in the Si-O stretching vibration characteristics. The laser beam-ceramic target interaction and the formation of the laser-induced ceramic plume are briefly discussed. Characterization techniques involved FTTR, X-ray diffraction, Auger and microprobe analysis, EDX and WDX analysis, SEM and TEM.
Excimer Laser Induced Crystallization of Amorphous Silicon Near Threshold
Authors: Bachrach R.Z. , Winer K. , Boyce J.B. , Ponce F.A. , Ready S.E. , Johnson R. , Anderson G.B.
Published: March 2011

Using a suitably homogenized excimer laser beam, we have shown that the threshold for crystallization of amorphous silicon is well defined and exhibits a square root dependence on the laser energy density above threshold. This sharp threshold behavior can be exploited in a number of ways.
Influence of Ion Beam Mixing on the Growth of High Temperature Oxide Superconducting Thin Film
Authors: Bordes N. , Rollett A.D. , Cohen M. , Nastasi M.
Published: March 2011

The superconducting properties of high temperature superconductor (HTS) thin films fabricated using the BaF2 process are dependent on the quality of the substrate used to grow these films. In order to maximize the lattice matching between the superconducting film and the substrate, we have used a YBa2Cu3O7, thin film deposited on <100> SrTiO3 as a template. The first film was prepared by co-evaporation of Y, BaF2 and Cu on <100> SrTiO3, followed by an anneal in “wet” oxygen at 850 °C. This film showed a sharp transition at about 90 K. A thicker layer of about 5000 A was then deposited on top of this first 2000 Å film, using the same procedure. After the post anneal at 900 °C, the transition took place at 82 K and no epitaxy of the second film was observed. Ion beam mixing at 400 °C, using 400 keV O ions was done at the interface of the two films (the second one being not annealed). After the post anneal, the film displayed an improved Tc at 88K. Moreover, epitaxial growth was observed to take place at the ion mixed two-layer interface which was dose dependent. These results suggest that the homoepitaxy of the second layer on the first is interface limited and can be enhanced by ion mixing treatments.
The Effect of Ion Induced Damage on the Mechanical Properties of Zirconia
Authors: Fleischer E. L. , Herd W. , Alford T. L. , Børgesen P. , Revesz P. , Mayer J. W.
Published: March 2011

Microhardness measurements were carried out on ion implanted single crystal Y2O3 stabilized cubic ZrO2. Ions were implanted up to fluences of 3×1017 ions/cm2. Comparison of the Knoop micro-hardness values of ZrO2 implanted with various species over a range of fluences showed that the principle variable causing hardness changes for inert ion implantation is damage energy and not the ion fluence nor the ion species. For shallow inert ion implants, the hardness versus damage energy gives a unified plot. Hardnesses rise with increasing deposited damage energy to a value 15% higher than that of unimplanted zirconia. With additional damage the hardness drops to a value 15% lower than that of the unimplanted zirconia. Deep implants showed 50% increases in hardness and significant fracture toughness increases.

Friction and wear measurements of the shallow implants in a pin-on-disk assembly showed very different behavior for high dose versus unimplanted ZrO2. The unimplanted samples showed debris with an associated rise in friction. The implanted system showed much less debris and a constant value of friction even after 10,000 cycles.
Synthesis of MOS2 Phase in the Near Surface Region of Al2O3 and ZrO2 by Ion Implantation
Authors: Rai A.K. , Bhattacharya R.S. , Rung S.C. , Patrizio D.
Published: March 2011

Al2O3 and ZrO2 substrates were coimplanted with 175 keV Mo+ and 74 keV S+ at doses of 1×10 cm−2 and 2×1017 cm−2 respectively. The energies of Mo+ and S+ ions were chosen to provide a nearly overlapping depth profiles in both substrates. Rutherford backscattering (RBS), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) techniques were used for characterization. The as implanted surface of Al2O3 became amorphous while as implanted ZrO2 surface remained crystalline. The MoS2 phase was observed in the as implanted ZrO2. The MoS2 phase was observed in the implanted region of Al2O3 and ZrO2 after furnace annealing at 700°C. Thermodynamic calculations were performed to predict the equilibrium binary phase formed in Al2O3 and ZrO2 under the present implant and annealing conditions. The predictions agree with the experimental findings.
Laser Vaporization and Deposition of Lead Zirconate Titanate
Authors: Schenck Peter K. , Cook Lawrence P. , Zhao Jianrong , Hastie John W. , Farabaugh Edward N. , Chiang Chwan-Kang , Vaudin Mark D. , Brody Philip S.
Published: March 2011

Laser-induced vaporization of ceramics shows promise as a technique for the deposition of thin films of these materials. Critical to the utility of this technique is an understanding of the laser-material interaction, plume formation and dynamics, material transport and how variations in the vaporization conditions affect the deposited film. Lead zirconate titanate (PZT, Zr/Ti-47/53) targets were irradiated using a q-switched Nd:YAG laser (15 ns, 100 mJ at 1.064 /μm) . The deposition chamber was maintained at a pressure of 100 mTorr oxygen. Material from the plume was collected on silicon wafer substrates, suspended 1.0 - 3.0 cm above the target. The films were characterized by SEM/EDX, TEM, x-ray diffraction and electrical measurements before and after annealing. Very thin films were deposited on carbon coated metal grids for observation in the TEM using a hot stage to study crystallization.
Temporally and spatially resolved spectra of the light emitted by the laser-generated plume were obtained with an optical multichannel analyzer (0MA) to yield information on the plume generation and chemistry of the deposition process. These spectra indicate that under these conditions a plasma is created above the target surface which persists for -100 ns after the laser pulse.
Comparison of the Effect of Boron and Phosphorus Impurities on Solid Phase Epitaxial Regrowth of Amorphous Silicon
Authors: Jeon Young-Jin , Becker M.F. , Walser R.M.
Published: March 2011

This work was concerned with comparing the relative effects of boron and phosphorus impurities on the solid phase epitaxial (SPE) regrowth rate of self-ion amorphized layers in silicon wafers with (100) orientation. We used previously reported data measured by in situ, high precision, cw laser interferometry during isothermal annealing for temperatures from 450°C to 590°C, and concentrations in the range from 7.8×1018 cm-3 to 5×l020 cm-3 for boron (NB), and from 5×l017 cm-3 to 3×1020 cm-3 for phosphorus (Np) impurities. The basis for the comparison was a recently developed model that extends the Spaepen-Turnbull model for silicon recrystallization to include ionization enhanced processes.

The experimental data for bom boron and phosphorus exhibited the linear variation in regrowth rate expected for low concentrations of implanted hydrogenic impurities having a concentration-independent fractional ionization in amorphous silicon. In the linear range the relative enhanced regrowth rate produced by these impurities can be expressed as a product of their, relative fractional ionizations, and the relative amount the rate constant for reconstruction is altered by localizing an electron, or a hole, at the reconstruction site. Assuming that a localized hole and electron equally softened the potential barrier for reconstruction, the experimental results indicated that boron had an ?40 meV lower barrier to ionization in amorphous silicon than phosphorus.

The variations in the SPE regrowth rates with higher concentrations of both implanted boron and phosphorus were well fit by quadratic equations, but with different curvatures (+ and - for B and P respectively). This result was interpreted to indicate that SPE regrowth was further enhanced by localized hole pairs, but retarded by localized electron pairs.
Irradiation-Induced Amorphization and Elastic Shear Instability in Intermetallic Compounds
Authors: Koike J. , Okamoto P. R. , Rehn L. E. , Bhadra R. , Grimsditch M. H. , Meshh M.
Published: March 2011

Previously we reported a substantial (∼ 50 %) decrease in shear modulus prior to amorphization in Kr irradiated Zr3Al, and proposed that amorphization is triggered when the crystalline lattice becomes unstable against shear stress. In the present work, the relation between amorphization and shear elastic instability has been investigated in two additional compounds (FeTi and NiAl) during room temperature irradiation with 1.7-MeV Kr+. A shear modulus was measured using Brillouin scattering; structural information was obtained in situ in a high voltage electron microscope interfaced to a tandem accelerator.

During irradiation of FeTi, chemical disordering and a large (∼40 %) decrease of shear modulus were observed, and an amorphous phase developed subsequently. In contrast, NiAl remained crystalline and chemically ordered during irradiation, and exhibited only a ∼ 10 % decrease in shear modulus. Hence, these two results provide further support that a shear instability triggers irradiation-induced amorphization. The shear instability mechanism may also apply to other solid-state amorphization techniques, e.g. hydrogen charging and mechanical deformation.
Studies of Ion-Assisted Growth and Properties of PbTe Epilayers Deposited by Rf Magnetron Sputtering
Authors: Cook J.G. , Mukherjee G. , Das S.R.
Published: March 2011

(111) PbTe // (111) BaF2 epilayers have been prepared by rf magnetron sputtering. A small negative substrate bias voltage (-10 V) enhances the (111) growth habit at reduced substrate temperatures (180 °C) and increased deposition rates (2.5 μ/h–1). Langmuir probe diagnostics is used to determine the energy and flux density of Ar ions incident on the growing film. Hall effect measurements are made to determine the carrier type and mobility as a function of the growth temperature.