bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth and Structure of in-plane Textured MgO Thin Films Deposited on Amorphous Substrates using ion-beam-assisted E-Beam Evaporation
Authors: Wang Connie P. , Do Khiem B. , Marshall Ann F. , Geballe Theodore H. , Beasley Malcolm R. , Hammond Robert H.
Published: April 2011

In-plane aligned MgO thin films (∼100Å) have been obtained on various amorphous substrates by Ar+ ion-assisted electron-beam evaporation. Based on RHEED and cross-section TEM, we have shown that the MgO texture appears at a very early stage of film growth and is optimized at a thickness of around 100Å. Optimal thickness is the stage at which the surface is fully covered by MgO crystallites. The planar-view TEM of grain structure evolution in samples at different stages of growth reveals the dynamics of the texture developing process. Small, (100)-faceted MgO grains were observed both in planar-view and cross-section TEM images.
Mechanisms of Formation of Nonlinear Optical Light Guide Structures in Metal Cluster Composites Produced by Ion Beam Implantation
Authors: Sarkisov S. S. , Williams E. K. , Curley M. J. , Smith C. C. , Ila D. , Venkateswarlu P. , Poker D. B. , Hensley D. K.
Published: April 2011

We report the results of characterization of linear and nonlinear optical properties of a light guide structure produced by MeV Ag ion implantation of LiNbO3 crystal (z-cut) in relation to the mechanisms of formation.
Control of Optical Performance from Er-Doped Alumina Synthesized Using An Ecr Plasma
Authors: Barbour J. C. , Potter B. G.
Published: April 2011

Hydrogen in deposited optical ceramics can modify the optical properties, and therefore the role of the hydrogen needs to be understood to control its effects. Erbium-doped amorphous alumina films were deposited using simultaneous electron beam evaporation of aluminum and erbium while bombarding the sample with 30 eV 02+ ions from an electron cyclotron resonance (ECR) plasma. The hydrogen content was measured, using elastic recoil detection, as a function of isochronal annealing treatments. The data was fit to a simple trap-release model in order to determine an effective activation energy for the thermal release of H from alumina and Er-doped alumina. The intensity of the ion-beam stimulated luminescence from these samples was monitored in the visible and near infrared regions as a function of the thermal treatments. In order to gain a better understanding of the influence of hydrogen, the ionoluminescence (IL) data from samples containing hydrogen were fit with a simple linear equation.
Does the Latent Track Occurrence in Amorphous Materials Result from a Transient Thermal Process?
Authors: Toulemonde M. , Dufour Ch. , Paumier E. , Pawlak F.
Published: April 2011

Heavy ion irradiations in the electronic stopping power (Se.) regime have been performed in amorphous materials. Latent tracks have been observed in amorphous semiconductors (a-Ge, a-Si) and their radii have been deduced from a phenomenological analysis in an amorphous metallic alloy, in vitreous silica and “polymer” like amorphous carbon. A transient thermal model is developed describing the energy diffusion by the electron gas, by the atomic lattice and the energy exchange between the two subsystems. According to Fick's law, the classical equations of heat flow in the two subsystems (electrons and atoms) are numerically solved in a cylindrical geometry taking into account the temperature dependence of all the parameters. A simulation of annealing of nuclear collisions induced defects in crystalline iron allows to determine a local temperature. Electronic defect creation occurs when Se. increases and becomes larger than a threshold which is correlated with the appearance of a molten phase. Using such a criterion, the radii of latent tracks are reproduced in both a - Ge and a - Si with the same value of the electron-phonon coupling despite large differences in their lattice thermodynamic parameters. Such a model is applied to amorphous metallic alloy Fe85B15, vitreous silica and amorphous carbon.
Influence of Oxygen on Er-Related Emission in Gan With a Large Yellow Band
Authors: Ueklsa S. , Goto T. , Kumagai Mv.
Published: April 2011

In order to investigate the luminescence properties of Er3+in GaN and the effect of oxygen (O) on Er3+ -related emission in GaN:Er, erbium (Er) ions were implanted into single-crystal h-GaN grown on a c-axis sapphire substrate at an energy of 2MeV. Oxygen ions were subsequently coiniplanted into GaN with Er ions. The influence of oxygen on Er-related emission in GaN with a large yellow band was studied by comparing photoluminescence (PL) measurements of GaN:Er and GaN:ErO. It was found that the optimum annealing temperature to obtain maximum PL intensity was 1200°C and that the E3+a-related PL intensities from GaN:ErO samples were negligibly enhanced in comparison with the GaN:Er samples. The temperature dependence of PL intensity in GaN:ErO showed no appreciable difference from that of GaN:Er. But good correlation between Er-related and a large yellow band emission was observed in GaN. This indicates that codoped oxygen ions influence Er-related and yellow band emission in GaN
Fast Redistribution of Boron Impurity in Si During Ion Irradiation
Authors: Buzynin A.N. , Luk’yanov A.E. , Osiko V.V. , Voronkov V.V.
Published: April 2011

The model of point defects-induced inversion of conductivity, formation and movement of the inverted p-n junction during Ar+ ions irradiation of p-Si crystals is presented.
Electrons and Defects in Semiconductors
Authors: Queisser H.J.
Published: April 2011

This review addresses the centennial of the identification of the electron as the unit charge particle as well as the golden anniversary of the first demonstration of transistor action in a semiconductor material. Surprising skepticism arose in the acceptance of the quantized nature of the electric fluid; and formidable hurdles were encountered by the early generations of transistors. These obstacles are difficult to understand today. The transistor demonstration initiated research leading to highly perfected semiconductors. These materials can today be utilized toward precision measurements of fundamental quantities, such as the elementary charge by the quantum Hall effect, or the electron's effective spin magnetic moments by spectroscopy of quantum beats. Electrons and holes represent particle-antiparticle pairs in semiconductors with strong photon interactions, much like the fundamental lepton particles, for which a speculation on an evolutionary origin is presented. The unexpectedly long life of injected excess minority carriers in germanium established lifetime as the essential quantitative measure for materials quality and initiated massive and successful research on semiconductor defects.
Smart-Cut® Technology: an Industrial Application of Ion Implantation Induced Cavities
Authors: Aspar B. , Lagahe C. , Moriceau H. , Soubie A. , Bruel M. , Auberton-Hervé A.J. , Barge T. , Maleville C.
Published: April 2011

The Smart-Cut® process is based on proton implantation and wafer bonding. Proton implantation enables delamination of a thin layer from a thick substrate to be achieved whereas the wafer bonding technique enables different multilayer structures to be achieved by transferring the delaminated layer onto a second substrate. One of the best known applications of Smart Cut® is the Silicon On Insulator structure. The physical mechanisms involved in the delamination process are discussed based on the study of Proton-induced microcavity formation during implantation and growth during annealing. The experimental results on the time and temperature required to achieve delamination lead to different activation energies depending on the implantation conditions and resistivity of the substrate. All the experiments indicate that growth of microcavities is mainly controlled by hydrogen diffusion. The growth of these microcavities and the pressure inside them induce delamination when the catastrophic radius of the microcavities is reached.
Comparison of Device Performance Fabricated on Thick So and Bulk Wafers
Authors: Sasaki A. , Mitsuhida E. , Abe H. , Yoshii Y
Published: April 2011

We have investigated the surface quality of thick 10μm Silicon-On-Insulator (SOI) wafers by comparing CMOS device performance and reliability of SOI wafers with those of bulk wafers. Large scale CMOS circuits, microcontrollers with 12Kbyte ROM and 512byte EEPROM, were fabricated on thick SOI wafers and on bulk wafers, and device performance and reliability were evaluated by means of functional tests and acceleration tests. A significant difference was observed only in the ROM bit-map failure analysis in the functional tests, in which the number of single bit failures (defined as a chain of up to 4 adjacent bit failures) was more evident on ROM fabricated on the thick SOI than that fabricated on bulk wafers. The result indicates that the crystal defects introduced by the initial oxygen concentration and excess film stress of the SiO interlayer may cause single bit failures. The SOI wafers were prepared by Direct Wafer Bonding 2(DWB) and a mechanical polishing technique to form a 10μm active silicon layer and a 625μm silicon substrate, which sandwiches a 0.25μm SiO2 interlayer. Thick SOI wafers such as these are becoming a promising material for one-chip integration of CMOS devices and Micro Electrical Mechanical System (MEMS) devices.
The Impact of Rapid Thermal Annealing on the Properties of the Si (100)-SiO2 Interface
Authors: Hurley P.K. , Leveugle C. , Mathewson A. , Doyle D. , Whiston S. , Prendergast J. , Lundgren P.
Published: April 2011

In this work, we present results and analysis which demonstrate the influence of rapid thermal annealing (RTA) on the properties of the Si(100)-SiO2 interface. Polysilicon/oxide/silicon capacitor structures were subjected to RTA treatments, in a nitrogen ambient, over the temperature range 600-1050°C. The structures were examined using high frequency and quasi-static capacitance-voltage (CV) analysis to determine the interface state density profile across the energy gap immediately following the RTA step. The effect of hydrogen annealing subsequent to the RTA process is also presented. Based on the analysis of the interface state density profiles, it is suggested in this work, that RTA (T > 600°C) exposes silicon dangling bond (Pb) centres at the Si(100)-SiO2 interface. The implications of this work to the study of the Si-SiO2 interface, and the technological implications for silicon based MOS processes, are discussed.
Effects of Sputtering Conditions on Texture, Microstructure and Magnetic Properties of the CoCrPt/NiAl Thin Films
Authors: Hsu Y.-N. , Laughlin D. E. , Lambeth D. N.
Published: April 2011

The effects of sputtering argon pressures and sputtering power on the microstructure, texture and magnetic properties of NiAI underlayers on CoCrPt films were investigated. In this paper, the relationship between the sputtering conditions, microstructure, crystallographic texture and magnetic properties of these thin films will be discussed. By controlling the sputtering pressure and sputtering power, the texture and microstructure of NiAI underlayers were found to vary. This in turn was found to influence the magnetic properties of CoCrPt thin films. It was found that 10 mtorr is the optimum pressure to deposit the NiAl thin films to obtain the best magnetic properties for our system. At this argon pressure, the coercivity reached a maximum value because of the strongest CoCrPt (1010) texture and smallest grain size. At lower argon pressures (< 10 mtorr), NiAI tended to have a (110) texture reducing the CoCrPt (1010) texture, which in turn reduced the CoCrPt coercivity and S*. Also, high NiAl deposition pressures (>30 mtorr) yielded larger grains and a weaker CoCrPt (1010) texture, thereby decreasing the coercivity of the CoCrPt films. Increasing the sputtering power has been found to increase the CoCrPt coercivity and S* value. However, the grain sizes of the CoCrPt/NiAl thin films deposited at higher sputtering power were larger than those obtained at lower sputtering power.
Behavior of Magnetic Aftereffect Along a Magnetization Reversal Curve in a Metal Particle Recording Material
Authors: Swartzendruber L. J. , Bennett L.H. , Della Torre E. , Brown H.J. , Judy J.H.
Published: April 2011

Experimental measurements of the aftereffect along a magnetization reversal curve are compared with the predictions of a Preisach-Arrhenius model for a high density particulate recording medium. The Preisach parameters are determined from the measurement of the major hysteresis loop and the remanence loop. The Arrhenius parameters were determined from a single aftereffect curve. It was then found that the model gives good qualitative agreement with both the initial slope and, for the case in which the aftereffect is not monotonic, the peak value of the aftereffect.
Observations of Depth-Sensing Reciprocating Scratch Tests of DLC and Nitrogenated-DLC Overcoats on Magnetic Disks
Authors: Scharf T.W. , Ott R.D. , Yang D. , Barnard J.A.
Published: April 2011

In this investigation, the wear durability of existing and candidate protective overcoats and substrates was examined. Specifically, 5 nm thick diamond-like carbon (DLC) and nitrogenated diamond-like carbon (N-DLC) overcoats were deposited by sputtering onto glass, glass-ceramic, and NiP/AlMg substrates. The magnetic medium was a 15 nm thick layer of CoCrPt deposited on a 50 nm thick underlayer of CrV. The wear resistance of the hard disks was determined by a recently developed depth sensing reciprocating scratch test using the Nano Indenter© II. During the scratch tests, a constant normal load of 30 jtN was maintained at an indenter velocity of 2μm/sec. It was found the N-DLC/CoCrPt/CrV/glass disk exhibited the most wear resistance and least amount of plastic deformation after the last wear event. Conversely, the NDLC/CoCrPt/CrV/NiP/AiMg disk displayed the least wear resistance even though the magnitude of the elastic recovery was the greatest. This amount of recovery was influenced by the high elastic modulus of the NiP/AIMg substrate. Consequently, the scratch test failed to isolate the intrinsic properties of the overcoat, however it provided a very powerful means of quantitatively assessing the overall response of the whole magnetic disk. This is more relevant since it simulates the response the disks see in performance. In addition, a discrete amount of nitrogen up to 14 atomic % incorporated into the amorphous network resulted in an increase in overcoat durability compared to the DLC overcoat. This was attributed to an increase in the XPS determined number of N-sp3 C bonded sites in a predominantly N-sp2 C bonded matrix. However, with increasing nitrogen concentrations ≥18%, the film structure was weakened due to the micro-Raman spectroscopy determined formation of terminated sites in the amorphous carbon network since nitrogen failed to connect the sp2 domains within the network.
The 1280 Cm−1 Absorption Line in Amorphous Hydrogenated Boron Carbide
Authors: Lin Shu-Han , Feldman Bernard J.
Published: April 2011

We report infrared absorption measurements that provide evidence for the presence of boron carbide icosahedra in amorphous hydrogenated boron carbide thin films. The infrared absorption spectra is dominated by an intense line at 1280 cm-1 with a FWHM of ≃320 cm-1. Similar lines have been previously reported in polycrystalline boron carbide, where boron carbide icosahedra make up the unit cell. In both systems, the linewidth narrows and the peak position shifts to higher energy with increasing carbon concentrations. From annealing studies of amorphous hydrogenated boron carbide, hydrogen plays a very small role in the 1280 cm-1 line. Finally, the integrated intensity of the 1280 cm-1 line is a sublinear function of the boron concentration, providing further evidence that the carbon concentration in these icosahedra increases as the carbon concentration of the film increases.
Characterizing the Magneto-optic Properties of Amorphous Rare Earth - Transition Metal Thin Films
Authors: Challener W. A.
Published: April 2011

The amorphous rare earth - transition metal (RE-TM) thin film alloys and nanolayered materials exhibit numerous properties advantageous for optical recording, including perpendicular anisotropy, high coercivity and low magnetization at room temperature, low noise, and easily adjustable Curie and compensation points. As a result these materials have been employed in all commercial magneto-optic (MO) media. On the other hand, the MO effect of these materials is relatively small and tends to decrease with decreasing wavelength. It is important to understand the useful limits of these materials in MO media, and to determine if their MO figure of merit can be substantially increased through appropriate doping or nanolayering. In this paper we discuss experimental techniques for measuring MO properties, a theoretical approach for analyzing the data and designing optical thin film stacks, and results for a variety of RE-TM thin film materials.
Preparation of Nanocrystalline Titania Powder by Aerosol Pyrolysis of Titanium Alkoxide
Authors: Ahonen P.P. , Kauppinen E.I. , Deschanvres J.L. , Joubert J.C. , Van Tendeloo G.
Published: April 2011

Nanocrystalline titania powders were prepared via aerosol pyrolysis of titanium tetrabutoxide precursor. As-received and annealed powders were characterized by XRD, SEM and TEM (+EDS), thermogravimetry, Raman- and IR-spectrometry, surface area analysis and XRF. In addition, gas-phase mass size distributions were obtained by low-pressure impactor aerosol measurements. Powders consisted of micrometer sized spherical particles. Amorphous titanium oxide powders were obtained at lower pyrolysis temperatures and only after subsequent thermal annealings crystallized titania was formed. Not until at 500°C in nitrogen and 580°C in air did pyrolysis synthesis form nanocrystalline anatase phase in-situ. During the annealing at 900°C for one hour rutile phase was usually approached, but phase pure anatase was obtained when powder had been synthesized in nitrogen atmosphere at 500°C. The proposed reason for the thermally stable anatase formation is the formation of oxygen deficient anatase phase which has a high thermal barrier to convert to rutile. Titanium tetrabutoxide evaporation and subsequent gas-to-particle formation of additional 30-80 nm particles was observed in nitrogen atmosphere at temperatures higher than precursor boiling point.
Fabrication of Agglomerate-Free Nanopowders by Hydrothermal Chemical Processing
Authors: Schmidt H.K. , Nass R. , Burgard D. , Nonninger R.
Published: April 2011

A chemical processing technique for the fabrication of nanopowders has been developed. The route is based on precipitation processes in solutions, either within aqueous droplets in micro-emulsions in the presence of surface modifiers like surfactants or by direct precipitation in solutions in the presence of these surface modifiers or small organic molecules directly bonded to the particle surface. In order to obtain well crystallized or densified particles, a continuous flow hydrothermal process has been developed which allows the fabrication of agglomerate-free surface modified nanopowders. The surface modification provides a full redispersibility after drying and permits a water-based processing. Nanoparticles preparation for ZrO2, ITO and ATO by this route are described.
Joining of Aluminium Structures with Aluminium Foams
Authors: Burzer J. , Bernard T. , Bergmann H. W.
Published: April 2011

The aim of this work is the evaluation of new construction elements for applications in transportation industry which are based on new designs incorporating commonly applied aluminium structures and aluminium foams. The work includes the characterisation of the joining process, the joining mechanism and the mechanical properties of the joining zone. A testing method for the joints is developed which is based on a common tensile test in order to evaluate the influence of the main laser welding parameters on the toughness of the joints and to afford a comparison between laser beam welding and gluing process. The analysis of the joining mechanism is investigated with the help of metallographic studies. In addition, the energy absorption properties of aluminium hollows filled and joined with foam structures are characterised.
Shear Properties on Aluminum Metal Foams Prepared by the Melt Route
Authors: Saenz E. , Baranda P. S. , Bonhomme J.
Published: April 2011

The shear modulus and shear strength of AISi7Mg aluminum foam with 15% (vol) of 13tm SiC particles were determined through shear testing. A foam slab with a density of 0.31 g/cm3 was supplied by Hydro Aluminium.

Four samples were tested according to ASTM C 273–61. The specimens were bonded to steel load plates. The relative displacement of the plates was measured using two extensometers. In order to evaluate the effect of the cell size distribution on shear properties, cell size and material distribution analyses were carried out for the metal foam slab in areas close to those from which the shear specimens were extracted.

A fast failure was observed after the maximum shear load. The failure in the samples were located in the central section of the slab mainly because the lower density was located there.
Emissivity Of Coated Silicon At Elevated Temperatures
Authors: Rogne H. , Ahmed H.
Published: April 2011

Isothermal electron beam heating has been combined with in situ optical measurements in order to measure the emissivity of coated silicon samples at elevated temperatures. The coatings include a number of oxide, nitride, and silicon films. Infrared emission spectra were recorded from I to 9 μm for temperatures between 750 and 1200°C. The experimental results were compared with calculated theoretical values, which were predicted from the theory of thin film coatings, using a matrix model incorporating the optical constants for the materials. A good match between experimental and theoretical values validates the use of the infrared optical constants for theoretical modelling related to control and temperature measurements in rapid thermal processing systems.
Residual Gases and Their Influence on Processes in the Atmospheric Rapid Thermal Processing Equipment
Authors: Hu Yao Zhi , Tay Sing Pin
Published: April 2011

The residual impurity gases in the atmospheric rapid thermal processing (RTP) equipment are becoming an important factor in sub-micron ULSI industry. For example, 1% nitrogen in oxygen decreases the RT oxide thickness, and a small amount of moisture or oxygen in nitrogen may strongly affect the RT titanium silicidation. The effective method to reduce the residual gases is to use process gas to purge the chamber. In the present paper the gas purging mechanisms were in-situ investigated in the flow rate range of 10 to 60 slpm using a Quadrapole Residual Gas Analyser (RGA) and gas sensors. The gases for purging studies are N2, O2, He and Ar. It has been found that there are two regimes in the dependence of the residual gas concentration on purging time. Based on the results of systematic experiments, a purging equation, called Pseudo-PST (“perfectly stirred tank) model, has been developed and was used to give the interpretation of the purging process in the atmospheric RTP system. The limitation of the RGA and the oxygen analyzer used to atmospheric RTP system was also discussed.
The Growth of Strained Thin Films of Gadolinium
Authors: Waldfried C. , Zeybek O. , Bertrams T. , Barrett S. D. , Dowben P.A.
Published: April 2011

The growth of strained thin films of gadolinium has been investigated with low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) and compared to the film growth of unstrained gadolinium. Strained thin films of gadolinium are distinct from the unstrained films by a substrate induced preferential domain growth direction, which is also reflected in the electronic structure.
The Effect of Deposition Method on Growth Morphology - Comparison of Molecular Beam Epitaxy, Ion Beam Assisted Deposition and Sputter Deposition
Authors: Michely Th. , Kalff M. , Comsa G.
Published: April 2011

Thin films created by the deposition or under influence of atoms with hyperthermal energies (E = 100 -104eV) exhibit properties which differ in many respects from those of films created by deposition of atoms with thermal energy. The morphologies of thin Pt-films deposited on Pt(111) under otherwise identical deposition conditions by molecular beam epitaxy (MBE), ion beam assisted deposition (IBAD) and sputter deposition (SD) differ in film structure size, island shapes and film roughness. The different film structure sizes are unambiguously traced back to two different island formation mechanisms inherent to these deposition methods. While in MBE the islands result from nucleation in a supersaturated adatom gas, in IBAD and SD they result by direct or indirect creation of adatom clusters as a consequence of single impacts of energetic atoms present in the depositing particle flux. The differences in film roughness are not only due to the different island formation mechanisms, but seem to be closely related to the different step edge structures at the growth front.
Epitaxial Growth of Nb Films and Nb/Cu Bilayers on A12O3 Substrates by DC Magnetron Sputtering
Authors: Loloee R. , Crimp M.A. , Zhu W. , Pratt W.P.
Published: April 2011

Epitaxial single crystal Nb films have been grown by sputter deposition on (1 1 2 0) sapphire substrates. Subsequently, high quality epitaxial Cu films, with two orientation variants, have been grown onto the epitaxial Nb films. The sputtered films have been characterized using atomic force microscopy, electron backscattered patterns, and conventional transmission electron microscopy.
Role of Oxygen Adatoms in Homoepitaxial Growth of Cu(001)
Authors: Yata Masanori , Rouch Herve , Nakamura Keikichi
Published: April 2011

O atoms segregate to the surface during Cu homoepitaxial growth on Cu(001)-(2√2×√2)-O to retain the (2√2×√2) surface. The presence of an O adlayer on the Cu surface raises the barrier height for the surface diffusion of the Cu adatom and increases the transition temperature of the growth mode from step flow to layer by layer. The growth proceeds by site exchange between Cu adatoms and O atoms. The site-exchange rate competes with the Cu deposition rate. There exists a critical Cu deposition rate above which the O atoms can not exchange the sites with Cu adatoms. The critical Cu deposition rate obeys an Arrhenius relation and the active energy for the site-exchange is estimated at 0.66 eV.
Failure Mechanisms of Particulate Two-Phase Composites
Authors: Antretter T. , Fischer E D.
Published: April 2011

In many composites consisting of hard and brittle inclusions embedded in a ductile matrix failure can be attributed to particle cleavage followed by ductile crack growth in the matrix. Both mechanisms are significantly sensitive towards the presence of residual stresses.

On the one hand particle failure depends on the stress distribution inside the inclusion, which, in turn, is a function of various geometrical parameters such as the aspect ratio and the position relative to adjacent particles as well as the external load. On the other hand it has been observed that the absolute size of each particle plays a role as well and will, therefore, be taken into account in this work by means of the Weibull theory. Unit cells containing a number of quasi-randomly oriented elliptical inclusions serve as the basis for the finite element calculations. The numerical results are then correlated to the geometrical parameters defining the inclusions. The probability of fracture has been evaluated for a large number of inclusions and plotted versus the particle size. The parameters of the fitting curves to the resulting data points depend on the choice of the Weibull parameters.

A crack tip opening angle criterion (CTOA) is used to describe crack growth in the matrix emanating from a broken particle. It turns out that the crack resistance of the matrix largely depends on the distance from an adjacent particle. Residual stresses due to quenching of the material tend to reduce the risk of particle cleavage but promote crack propagation in the matrix.
Theoretical Analysis of Faceted Void Dynamics in Metallic Thin Films Under Electromigration Conditions
Authors: Ho Henry S. , Gungor M. Rauf , Maroudas Dimitrios
Published: April 2011

A theoretical analysis is presented of the electromigration-induced dynamics of transgranular voids in metallic thin films. The analysis is based on self-consistent dynamical simulations of current-driven void surface propagation coupled with the distribution of the electric field in the metallic film. The simulation predictions highlight the rich nonlinear dynamics of current-driven evolution of voids that become faceted due to the strongly anisotropic nature of surface diffusion. The numerical results are analyzed based on approximate analytical solutions to faceted void migration and a linearized theory for the morphological stability of planar void facets.
The Role of the Diffusion Mechanism in Models of the Evolution of Microstructure During Phase Separation
Authors: Rautialnen T.T. , Sutton A.P.
Published: April 2011

We have studied phase separation and subsequent coarsening of the microstructure in a two-dimensional square lattice using a stochastic Monte Carlo model and a deterministic mean field model. The differences and similarities between these approaches are discussed. We have found that a realistic diffusion mechanism through a vacancy motion in Monte Carlo simulations is cruicial in producing different coarsening mechanisms over a range of temperatures. This cannot be captured by the mean field model, in which the transformation is governed by the minimization of a free energy functional.
Potts Model Simulation of Grain Size Distributions During Final Stage Sintering
Authors: Zeng P. , Tikare V.
Published: April 2011

The Potts Monte Carlo model was used to simulate microstructural evolution and characterize grain size distribution during the final stages of sintering. Simultaneous grain growth, pore migration and pore shrinkage were simulated in a system with an initial porosity of 10% with varying ratios of grain boundary mobility to pore shrinkage rates. This investigation shows that the presence of pores changes the grain size distribution and the topological characteristics due to pinning of grains by pores. As pores shrink away, their pinning effect decreases. Once pore shrinkage is complete, normal grain growth is achieved.
A Study of Self-Reinforcement Phenomenon in Silicon Nitride by Monte-Carlo Simulation
Authors: Okamoto Y. , Hirosaki N. , Matsubara H.
Published: April 2011

A grain growth model based on the results of Monte-Carlo simulations is proposed for silicon nitride. The model was derived from the Potts model; in addition, principal characteristics of silicon nitride such as presence of liquid phase and anisotropy of grain growth were introduced. Employing this model, microstructure development of silicon nitride was investigated.

Under certain simulation conditions, several grains grew in preference to other grains, and consequently, a self-reinforced microstructure was produced similar to that of actual silicon nitride. In particular, liquid phase fraction was found to be dominant factor affecting microstructure development.
Fatigue Behavior of GeO2-SiO2 Glasses
Authors: Gulati Suresh T. , Helfinstine John D.
Published: April 2011

The fatigue behavior of binary oxide glasses in the germania-silica system is interesting since it influences the long-term mechanical reliability of products made of these glasses. Dynamic fatigue tests were carried out in four-point bending in 100% RH using tumble abraded rods. The fatigue data were obtained as a function of GeO2 content which ranged from 0 to 24 mole %. In addition, other physical properties of these glasses, such as the thermal expansion coefficient, were measured as a function of GeO2 content. The results of these tests and analyses are highlighted in this paper.
Current Advances in Development of Material in the Field of Wiring in Japan
Authors: Takagi S. , Ishii N. , Hashimoto D.
Published: April 2011

This paper presents the current advances in the development of materials in the field of telecommunication wiring together with the background which created the need for the new technologies. The background is somewhat unique to the current socio-economical situation of Japan. The key technical areas, which are addressed in this paper, are; (1) fibers for transmission of over 1 Tbps by utilizing WDM (wavelength division multiplexing), (2) fibers for fiber amplifiers to replace repeaters within trunk lines, (3) high density cables with over 1000 fiber counts, (4) ABF (air blown fiber) for access system, (5) plastic optical fibers wiring in premises or offices operating at the transmission speed of over 200 Mbps.
Telecommunications Technology for the First Decade of the 21st Century
Authors: Wyndrum R. W.
Published: April 2011

Today I will focus on telecommunications technology for the first decade of the 21st century. Few things incite speculation about the future more than a year ending in the numeral “zero.” With the approaching millennium and its near-mystical three zeroes, everyone everywhere hungers for a glimpse into the future. My vision of the telecommunications future shows a collective of universal capabilities made possible by limitless digital networks with ubiquitous access and functionality. Mobile communications, the Internet, video, telephony and a broad array of end-user services will be the major drivers moving network providers to fuse capability with transparency. Integration of the full spectrum of communication possibilities will be the trend of the 21st century.
Long-Term Reliability of Silica-Based Planar Lightwave Circuit Devices
Authors: Hanafusa H. , Sumida S. , Takato N.
Published: April 2011

We describe the results of accelerated lifetests performed on silica-based planar lightwave circuit (PLC) devices. Specifically, we tested PLC splitter modules in damp heat environments with different temperatures and humidities. The time-to-failure data of the splitter samples were analyzed by using the Weibull distribution, and the shape parameter was derived as 1.77. Moreover, the temperature and humidity dependence of the median life e was analyzed by using the equation

and the coefficients E and n were determined to be 1.49 eV and 3.70, respectively. The thirtyyear hazard rate is estimated to be less than 40 FIT for PLC splitter modules operating at 60°C/ 40% RH.
Life Testing and Reliability Behavior of Gan/Ingan/Aigan Light-Emitting Diodes
Authors: Osinski M. , Barton D. L. , Helms C. J. , Berg N. H. , Seager C. H.
Published: April 2011

Our studies of device lifetime and the main degradation mechanisms in Nichia blue LEDs date back to Spring 1994. Following the initial studies of rapid failures under high current electrical pulses, where metal migration was identified as the cause of degradation, we have placed a number of Nichia NLPB-500 LEDs on a series of life tests. The first test ran for 1000 hours under normal operating conditions (20 mA at 23 °C). As no noticeable degradation was observed, the second room temperature test was performed with the same devices but with a range of currents between 20 and 70 mA. After 1600 hours, some degradation in output intensity was observed in devices driven at 60 and 70 mA, but it was still less than 20%. The subsequent tests included stepping up the temperature by 10 °C in 500 h intervals up to a final temperature of 95 °C using the same currents applied in the second test. This work reviews the failure analysis that was performed on the degraded devices and the degradation mechanisms that were identified.
Material Properties of GaN in the Context of Electron Devices
Authors: Morkoç H. , Cingolani R. , Lambrecht W. , Gil B. , Jiang H.-X , Lin J. , Pavlidis D. , Shenai K.
Published: April 2011

Wide bandgap nitride semiconductors have recently attracted a great level of attention owing to their direct bandgaps in the visible to ultraviolet regions of the spectrum as emitters and detectors. However, this material system with its favorable heterojunctions and transport properties began to produce very respectable power levels in microwave amplifiers. If and when the breakdown fields achieved experimentally approaches the predicted values, this material system may also be very attractive for switching power devices. In addition to the premature breakdown, a number of scientific challenges remain including a clear experimental investigation of polarization effects. In this paper, transport properties as pertained to electronic devices and potential switching devices, and polarization effects will be treated.
Etch Processing of III-V Nitrides
Authors: Eddy Charles R.
Published: April 2011

As III-V nitride devices advance in technological importance, a fundamental understanding of device processing techniques becomes essential. Recent works have exposed various aspects of etch processes. The most recent advances and the greatest remaining challenges in the etching of GaN, AIN, and InN are reviewed. A more detailed presentation is given with respect to GaN high density plasma etching. In particular, the results of parametric and fundamental studies of GaN etching in a high density plasma are described. The effect of ion energy and mass on surface electronic properties is reported. Experimental results identify preferential sputtering as the leading cause of observed surface non-stoichiometry. This mechanism provides excellent surfaces for ohmic contacts to n-type GaN, but presents a major obstacle for Schottky contacts or ohmic contacts to p-type GaN. Chlorine-based discharges minimize this stoichiometry problem by improving the rate of gallium removal from the surface. In an effort to better understand the high density plasma etching process for GaN, in-situ mass spectrometry is employed to study the chlorine-based high density plasma etching process. Gallium chloride mass peaks were monitored in a highly surface sensitive geometry as a function of microwave power (ion flux), total pressure (neutral flux), and ion energy. Microwave power and pressure dependencies clearly demonstrate the importance of reactive ions in the etching of wide band gap materials. The ion energy dependence demonstrates the importance of adequate ion energy to promote a reasonable etch rate (≥ 100-150 eV). The benefits of ion-assisted chemical etching are diminished for ion energies in excess of 350 V, placing an upper limit to the useful ion energy range for etching GaN. The impact of these results on device processing will be discussed and future needs identified.
Hydrogen and Nitrogen Ambient Effects on Epitaxial Lateral Overgrowth (ELO) of GaN Via Metalorganic Vapor-Phase Epitaxy (MOVPE)
Authors: Tadatomo Kazuyuki , Ohuchi Yoichiro , Okagawa Hiroaki , Itoh Hirotaka , Miyake Hideto , Hiramatsu Kazumasa , Miyake Hideto , Hiramatsu Kazumasa
Published: April 2011

Ambient gas effect on the epitaxial lateral overgrowth (ELO) of GaN via metalorganic vapor-phase epitaxy (MOVPE) on a MOVPE-grown GaN (0001) / sapphire (0001) substrate with a SiO2 stripe mask has been studied by means of field-emission scanning electron microscopy (SEM) and high-resolution X-ray diffraction (XRD) analysis. Different ambient gases of nitrogen, hydrogen and their mixture (mixture ratio, hydrogen: nitrogen = 1: 1) affect the lateral overgrowth rate, the surface morphology and the crystalline tilting of ELO-GaN layers. XRD revealed that the ELO-GaN layer on the SiO2 mask aligned along the <1100> direction exhibited anisotropic crystalline tilting toward <1120>. For ELO-GaN growth in nitrogen ambient, the growth rate of the (0001) facet decreases, the lateral overgrowth rate increases and the tilting of the ELO-GaN layer increases, while no smooth surface is obtained, in comparison with ELO-GaN growth in hydrogen ambient. For the mixture ambient, a smooth surface with a fast lateral overgrowth rate is achieved and the dislocation density is not more than 107 cm-2, which is comparable to that in hydrogen ambient.
Structure of Ain on Si (111) Deposited with Metal Organic Vapor Phase Epitaxy
Authors: Rehder Eric , Zhou M. , Zhang L. , Perkins N. R. , Babcock S. E. , Kuech T. F.
Published: April 2011

The surface morphology and structure of AIN deposited by metal organic vapor phase epitaxy (MOVPE) on Si (111) at growth temperatures ranging from 825 to 1175°C was investigated. Transmission electron microscopy (TEM), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), and secondary ion mass spectrometry (SIMS) techniques were used to study the resulting film structure. Growth at high temperatures but less than ∼1100°C, resulted in a wire texture with some degree of in-plane alignment with (0001)AIN //(111)si, <1010>AIN //<211>si, and <1120>AIN. // <110>si. Deposition at temperatures greater than 1100°C results in single crystal films consisting of domains 60 nm across with an aspect ratio near unity. Growth below 1100°C leads to degraded crystal quality with the grains developing random rotational misalignments around the AIN [0001] axis. Growth at lower temperatures produces islands elongated along the [1120] direction. At the growth temperature of 825°C, the aspect ratio of the islands increased to 3 and a width of 25 nm. Cross -sectional TEM reveals that these islands are faceted due to slow growth on the {1101} planes.
Quantum-Confined Stark Effect and Recombination Dynamics of Spatially Indirect Excitons in Mbe-Grown GaN-AlGaN Quantum Wells
Authors: Lefebvre Pierre , Gil Bernard , Allègre Jacques , Mathieu Henry , Grandjean Nicolas , Leroux Mathieu , Massies Jean , Bigenwald Pierre
Published: April 2011

We analyze the low-temperature photoluminescence decay times, for a series of MBE-grown samples embedding GaN-AlGaN quantum wells. We investigate a variety of configurations in terms of well widths, barrier widths and overall strain states. We find that not only the wells but also the barriers are submitted to large built-in electric fields. In the case of narrow barriers (5 um), these fields favor the nonradiative escape of carriers from narrow wells into wider wells. When all wells have the same width, the field in such narrow barriers allow us to observe the recombination of long-lived “inter-well” excitons at energies close to those of the short-lived “intra-well” excitons. Our results also prove that the energies and the dynamics of excitonic recombinations depend on the parameters of the heterostructures in a complicated way, due to the interplay of piezoelectric and spontaneous polarizations.
Studies on Carbon as Alternative P-Type Dopant for Gallium Nitride
Authors: Birkle U. , Fehrer M. , Kirchner V. , Einfeldt S. , Hommel D. , Strauf S. , Michler P. , Gutowski J.
Published: April 2011

GaN layers were grown by molecular beam epitaxy and doped with carbon of nominal concentrations ranging from 1016 cm-1 to 10 20 cm-1. The incorporation of carbon leads to a reduction of the background electron concentration by one order of magnitude but the material remains n-type. For high carbon concentrations a re-increase of the carrier concentration is observed which is related to selfcompensation. Investigations of the donor-acceptor-pair luminescence show that doping with carbon is accompanied by the generation of a new donor exhibiting a thermal activation energy of about 55 meV. Layers grown by atomic layer epitaxy are marked by an increased intensity of the donor-acceptor-pair band luminescence which is attributed to the enforced incorporation of carbon onto the nitrogen sublattice. The yellow luminescence is found to be a typical feature of all carbon doped layers in contrast to nominally undoped samples.
Control of the Polarity and Surface Morphology of GaN Films Deposited on C-Plane Sapphire
Authors: Sumiya M. , Ohnishi T. , Tanaka M. , Ohtomo A. , Kawasaki M. , Yoshimoto M. , Koinuma H. , Ohtsuka K. , Fuke S.
Published: April 2011

Control of the polarity of GaN films deposited by metalorganic chemical vapor deposition was achieved by substrate nitridation and subsequent annealing of a buffer layer. The surface morphology and optical properties of 1.2μm GaN films were influenced by the different growth mode due to the polar direction. Coaxial impact collision ion scattering spectroscopy revealed that the polarity composition of a buffer layer on nitrided sapphire varied by annealing in a H2 atmosphere. It was considered that the systematic variation of the surface morphology was caused by the polarity composition of the buffer layer.
Electrical Characterization of MOVPE-GROWN P-Type GaN:Mg Against Annealing Temperature
Authors: Fujita Shizuo , Funato Mitsuru , Park Doo-Cheol , Ikenaga Yoshifumi , Fujita Shigeo
Published: April 2011

Hall effect measurements have been applied for the electrical characterization of p-type Mg-doped GaN grown by metalorganic vapor-phase epitaxy on sapphire substrates in terms of annealing temperature for dehydrogenation (N2 annealing) and hydrogenation (H2 annealing) of the acceptors. With the N2 annealing temperature from 600 to 900°C for dehydrogenation, both hole concentration and mobility increases, showing more activation of acceptors and less incorporation of unfavorable scattering centers probably originating from Mg-H bondings. The N2 annealing at higher than the growth temperature results in reduced hole concentration, but the mobility gets higher. Some defects compensating acceptors may be induced at high temperature annealing, but they seem to be no scattering centers and be inactivated by successive hydrogenation and re-dehydrogenation at the optimum dehydrogenation temperature 900°C. The electrical degradation of GaN due to thermal damage is not very destructive and can be well recovered by annealing treatments.
Dynamic Crack Propagation in Single-Crystalline Silicon
Authors: Cramer T. , Wanner A. , Gumbsch P.
Published: April 2011

Tensile tests on notched plates of single-crystalline silicon were carried out at high overloads. Cracks were forced to propagate on {110} planes in a <110> direction. The dynamics of the fracture process was measured using the potential drop technique and correlated with the fracture surface morphology. Crack propagation velocity did not exceed a terminal velocity of v = 3800 m/s, which corresponds to 83%7 of the Rayleigh wave velocity vR. Specimens fractured at low stresses exhibited crystallographic cleavage whereas a transition from mirror-like smooth regions to rougher hackle zones was observed in case of the specimens fractured at high stresses. Inspection of the mirror zone at high magnification revealed a deviation of the {110} plane onto {111} crystallographic facets.
Molecular Dynamics Study of Copper and Aluminum under Mechanical Strain
Authors: Heino P. , Häkkinen H. , Perondi L. , Kaski K.
Published: April 2011

Mechanical properties of copper and aluminum have been studied using finite temperature molecular dynamics simulations. Atomic interactions have been described by a many-atom effective medium potential, which takes into account interactions up to third neighbors. The computed elastic constants showed good agreement with experimental data. Encouraged by these results the model was applied to study fracture in copper. Systems with a grain boundary and an initial cut serving as a crack seed have been studied. In the first case, crack nucleation and propagation took place exclusively at the grain boundary. In the second case, dislocation propagation was observed in one of the <110> directions, with a speed of about 60% of the longitudinal speed of sound. For thin systems crack propagation occurred through micro-void coalescence with a speed of about 30% of the Rayleigh wave speed in copper.