bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of Porosity and Surface Roughness of Cured Phenolic Resin by Ion Implantation
Authors: Zimmerman R.L. , Ila D. , Smith C.C. , Evelyn A.L. , Poker D.B. , Hensley D.K.
Published: April 2011

We present recent results using ions such as C., O, Si, Fe, Zn, and Au at energies between 100 keV to 10 MeV to increase the roughness and porosity of the partially and fully cured precursor phenolic resins. The fully cured phenolic resin is called Glassy Polymeric Carbon (GPC). GPC is chemically inert, biocompatible and useful for medical applications, such as heart valves and other prosthetic devices. Ion implantation enhances biological cell/tissue growth on, and tissue adhesion to, prosthetic devices made from GPC. We have previously shown that increased porosity of GPC is also useful for drug delivery devices. The porosity of the ion implanted partially and fully cured precursor phenolic resins was measured by introducing lithium from a molten LiCl salt into each sample. By using Li(p,2α) nuclear reaction analysis (NRA) we measured the concentration of Li retention in the pre- and post-implanted samples. The surface roughness was measured using optical microscopy. The curing process was monitored using micro-Raman microscopy. We have correlated the NRA measurements of increased pore availability with the observations of increased surface roughness.
Post Implantation Treatment of Silicon Carbide-Based Sensors for Hydrogen Detection Properties Enhancement
Authors: Muntele I. C. , Muntele C. I. , Ila D. , Zimmerman R. L. , Poker D. B. , Hensley D. K.
Published: April 2011

Palladium ion implantation was performed at energies of 35 keV, 50 keV and 100 keV, at both room temperature (RT) and 500 °C, on two identical sets of 6H, n-type silicon carbide samples. Then, one set of samples was subjected to a post-implantation sputtering process, in order to eliminate the substrate layer damaged by the palladium ions during implantation. Electrical and micro-Raman measurements have been performed on both sets of samples, aiming for a better understanding of the chemical processes that take place in the presence of hydrogen atmosphere in the chemical sensors prepared this way.
Modification of Carbon Related Films with Energy Beams
Authors: Naramoto Hiroshi , Xu Yonghua , Narumi Kazumasa , Zhu Xiaodong , Vacik Jiri , Yamamoto Shunya , Miyashita Kiyoshi
Published: April 2011

We report on typical examples of thin carbon films prepared employing energy beam techniques such as ion beam deposition, ion beam assisted deposition and Laser illumination. In an annealing study of ion beam deposited carbon films, small dots with sub-micron size are isolated through the selective oxidation of sp3-bonded amorphous carbon films, and they were confirmed to be diamond nano-particles by micro-Raman spectrometry. C60 deposition assisted with Ne ion beam results in two kinds of films: 1) The quality of C60 films is improved by the assist of 500eV Ne ion bombardment. 2) The increase of Ne ion Energy results in the decomposition of C60 and the films obtained at 700°C contain possible nano-diamond crystallites at the center of the intense beam spot. The Laser illumination decomposes C60 molecules in general, but the fine-tuning of Laser energy density makes it possible to prepare an array of high luminescent spots.
Properties of Gallium Disorder and Gold Implants in GaN
Authors: Jiang W. , Weber W.J. , Thevuthasan S. , Shutthanandan V.
Published: April 2011

Epitaxial single-crystal GaN films on sapphire were implanted 60° off the <0001> surface normal with 1 MeV Au2+ or 3 MeV Au3+ over a fluence range from 0.88 to 86.2 ions/nm2 at 180 and 300 K. The implantation damage was studied in-situ using 2 MeV He+ Rutherford backscattering spectrometry in channeling geometry (RBS/C). The disordering rate in the near- surface region is faster than at the damage peak. In all cases, results show an intermediate stage of Ga disorder saturation at the damage peak. During the thermal annealing at 870 K for 20 min, some Au implants in GaN diffuse into the amorphized surface region, while the remaining Au atoms distribute around the mean ion-projected-range. These results suggest a high mobility of both Ga defects and Au implants in GaN. Deeper damage implantation by 3 MeV Au3+ indicates that GaN cannot be completely amorphized up to the highest ion fluence (86.2 ions/nm2) applied at 300 K.
Optimization of the Ion-Cut Process in Si and SiC
Authors: Holland O. W. , Thomas D. K. , Gregory R. B.
Published: April 2011

H+-implantation is the basis for an ion-cut process, which combines hydrophilic wafer bonding, to produce heterostructures over a wide range of materials. This process has been successfully applied in Si to produce a commercial silicon-on-insulator material. The efficacy of implantation to produce thin-film separation was studied by investigation of H+-induced exfoliation in Si and SiC. Experiments were done to isolate the effects of the hydrogen chemistry from that of implant damage. Damage is manipulated independently of H+ dosage by a variety of techniques ranging from elevated temperature irradiation to a two-step implantation scheme in Si, and the use of channeled-ion implantation in SiC. The results will demonstrate that such schemes can significantly reduce the critical dose for exfoliation.
Ion Beam Slicing of Single Crystal Oxide Thin Films
Authors: Thevuthasan S. , Shutthanandan V. , Jiang W. , Weber W. J.
Published: April 2011

Epitaxial thin film liftoff using the ion-slicing method has been applied to SrTiO3 single crystals. Rutherford backscattering spectrometry along with channeling (RBS/C) has been used to investigate the relative disorder as a function of temperature from the samples that were irradiated by 40 KeV hydrogen ions to a fluence of 5.0×1016 H+/cm2. Hydrogen profiles were also measured as a function of annealing temperature to understand the role of hydrogen in the ion slicing process. Film cleavage occurred during or after annealing at 570 K, and cleaved film has been successfully transferred to a silicon substrate using ceramic adhesive.
Ion Beam Assisted Texture Evolution during Thin Film Deposition of Metal Nitrides
Authors: Stritzker Bernd , Gerlach Jürgen W. , Six Stephan , Rauschenbach Bernd
Published: April 2011

Ion beam assisted deposition, i.e., the bombardment of thin films with a beam of energetic particles has become a highly developed tool for the preparation of thin films. This technique provides thin films and coatings with modified microstructure and properties. In this paper examples are presented for the modifying of the structure: in-situ modification of texture during ion beam assisted film growth and ion beam enhanced epitaxy.

The biaxial alignment of titanium nitride films prepared on Si(111) by nitrogen ion beam assisted deposition at room temperature was studied. The bombardment perpendicular to the surface of the substrate causes an {001} alignment of crystallites. A 55° ion beam incidence angle produces both a {111} orientation relative to the surface and a {100} orientation relative to the ion beam. This results in a totally fixed orientation of the crystallites. The texture evolution is explained by the existence of open channeling directions.

Epitaxial, hexagonal gallium nitride films were grown on c-plane sapphire by low-energy nitrogen ion beam assisted deposition (≤ 25 eV). The ion energy was chosen to be less than the corrected bulk displacement energy to avoid the formation of ion-induced point defects in the bulk. The results show that GaN films with a nearly perfect {0002} texture are formed which have superior crystalline quality than films grown without ion irradiation. The mosaicity and the defect density are reduced.

By applying an assisting ion beam during pulsed laser deposition of aluminum nitride on the c-plane of sapphire, epitaxial, hexagonal films could be produced. The results prove the beneficial influence of the ion beam on the crystalline quality of the films. An optimum ion energy of 500 eV was found where the medium tilt as well as the medium twist of the crystallites was minimal.
A Scaling Approach to Modeling Indentation Measurements
Authors: Cheng Yang-Tse , Li Zhiyong , Cheng Che-Min
Published: April 2011

Using dimensional analysis and finite element calculations, the relationships between hardness, elastic modulus, final contact depth, and the work of indentation are extended to conical indentation in elastic-plastic solids with various cone angles. These relationships provide new insights into indentation measurements. They may also be useful to the interpretation of results obtained from instrumented indentation experiments.
Determination of the Real Indenter Shape for Nanoindentation/Nanotribology Tests by Surface Metrological and Analytical Investigations
Authors: Enders S. , Grau P. , Hawthorne H. M.
Published: April 2011

In this paper a critical comparison of different kinds of surface metrological methods like atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical interferometric profilometry is made, as well as analytical investigations based on both Hertz and Sneddon theories of pure elastic contact, to qualify the real indenter shape function. The results obtained show the advantages and disadvantages of the respective methods by describing a rounded indenter tip.
Probing the Critical Stress Intensity Factor for Slip Transfer across Grain Boundaries by Subgranular Indentation Alfonso
Authors: Ngan H.W. , Chiu Y.L.
Published: April 2011

By analysing the relevant results in the literature, we have found that, when indentation is made on a subgranular level, the hardness varies roughly inversely with the square root of the distance between the indent and the grain boundary. This effect is analogous to the Hall-Petch effect for macroscopic deformation.
Dislocation Configurations Around Nanoindentations in Reconstructed Au(001)
Authors: Fuente O. Rodríguez de la , González M.A. , Rojo J.M.
Published: April 2011

Nanoindentations resulting from STM tungsten tip contacts with the 5×20 reconstructed surface of a Au(001) crystal around the indentation point have been studied by Scanning Tunnel Microscopy (STM). A novel defect structure is recognised: a row of hillocks extending along more than a hundred nm along the <110> directions stemming from the indentation point. These hillocks have about 7 nm of side and 0.06 nm of height. With the help of simulation models we identify individual hillocks as dislocation configurations consisting of two stacking fault ribbons encompassed by Shockley partials having a stair-rod dislocation as a ridge. It is proposed that hillocks are generated by plastic flow, from an initially nucleated V-shaped dislocation loop intersecting the surface.
The Effects of Creep on Elastic Modulus Measurement Using Nanoindentation
Authors: Feng G. , Ngan A.H.W.
Published: April 2011

During the unloading segment of nanoindentation, time dependent displacement (TDD) accompanies elastic deformation. Consequently the modulus calculated by the Oliver-Pharr scheme can be overestimated. In this paper we present evidences for the influence of the measured modulus by TDD. A modification method is also presented to correct for the effects of TDD by extrapolating the TDD law in the holding process to the beginning of the unloading process. Using this method, the appropriate holding time and unloading rate can be estimated for nanoindentation test to minimise the effects of TDD. The elastic moduli of three materials computed by the modification method are compared with the results without considering the TDD effects.
Mechanism of Al-Cu-Fe Quasicrystal Plastic Deformation Studied by Instrumented Sharp Indentation
Authors: Dub Sergey N. , Milman Yuly V. , Lozko Dina V. , Belous Anton N.
Published: April 2011

Cyclic nanohardness tests of Al65Cu23Fe12 quasicrystal reveals a different mechanism of plastic deformation as compared with a regular metal. For a polycrystalline metal, the indent depth increases monotonically with load, while for a quasicrystal, it increases stepwise. Probably, the step formation in the Al-Cu-Fe quasicrystal loading curve is due to the structural transformation in the indent. It is known that the quasicrystal structure destroys at high pressure and transforms into a regular crystalline structure. Therefore, it is possible to attribute the pressure drop in the indent to the transformation of the quasicrystalline structure into the crystalline one and extrusion of the plastic polycrystalline metallic phase out from indent. The observation of thin layers extruded out of the indent in Al-Cu-Fe quasicrystal supports this assumption.
Determining the Area Function of Spherical Indenters for Nanoindentation.
Authors: Bushby Andrew J. , Jennett Nigel M.
Published: April 2011

Nanoindentation with spherical tipped indenters provides a powerful technique for exploring surface mechanical properties through the application of Hertzian mechanics. The full range of mechanical response can be obtained from elastic, through the yield point to a range of permanent deformation. However, the successful application of the technique requires accurate calibration of the indenter tip geometry. In this paper methods based on indentation into a number of reference materials are used to characterise a range of spherical tipped indenters with nominal radii from 5 to 50 microns. A traceably calibrated metrological AFM is also used to determine the actual shape of one of the indenters. The sensitivity of each method to test parameters is discussed. Coincidence of the data from both methods validates the determined shape of the indenter and offers the opportunity to cross-correlate the calibration of both instruments with high sensitivity.
Influence of Tipradius and Substrate on the Nanotribological Characterization of Thin DLC Coatings
Authors: Staedler Thorsten , Schiffmann Kirsten I.
Published: April 2011

In this work diamond-like carbon films deposited via plasma enhanced chemical vapor deposition with a thickness of 250nm on different substrates are characterized by nanoindentation and microscratching in combination with scanning probe microscopy. The substrates (SU8 photoresist, quartz glass, Si(100) and AlTiC ceramic) provide a wide range of combinations between film and substrate properties. The experimental configuration allows the testing of samples with loads between 1μN and 10mN and a high local resolution. The tribological response of the various film/substrate systems is analysed in two different ways. A single scratch test with linear increasing load and an oscillating wear tests at constant loads is used. The tip radii of the conical diamond tips utilized vary between 0.6 and 6μm. Both, the substrates as well as the tip radii, show a significant influence on the tribological behavior of the systems.
Microstructure and Post-Irradiation Annealing Behavior of 20% Cold-Worked 316 Stainless Steel
Authors: Cole J. I. , Allen T. R. , Kusanagi H. , Dohi K. , Ohta J.
Published: April 2011

Microstructural examination and in situ post-irradiation annealing studies were carried out on 20% cold-worked 316 stainless steel (SS) hexagonal duct material following irradiation in the reflector region of the EBR-II reactor. Stainless steel hexagonal ducts were used to house reactor subassemblies and provide a valuable source of information on irradiation behavior of reactor structural materials at lower dose-rates (on the order of 10-8 dpa/sec) than previously examined. The microstructural development of samples irradiated to doses of 1, 20 and 30 dpa is examined, while the post-irradiation annealing behavior of a sample irradiated to 20 dpa is described. Annealing studies were performed at 370 and 500°C to examine the kinetics of radiation damage recovery as a function of annealing temperature. The initial (pre-annealed) microstructures consists of a substantial density of irradiation induced chromium-rich M23C6 and M6C carbides which form both on the grain boundaries and within the grain interiors. Recovery of the cold- work is evident in the 1 dpa sample while samples irradiated to 20 and 30 dpa possess dense populations of voids and dislocation structures consisting of networks of line dislocations and faulted dislocation loops. Results indicate that post-irradiation annealing of the samples at 370°C for 1 hour has little effect on the microstructure, while further annealing at 500°C for 1 hour results in void shrinkage, the formation of small cavities, and a reduction in the dislocation loop and network density.
Molecular Dynamic Simulation of Cascade Overlap and Amorphization in 3C-SiC
Authors: Gao Fei , Weber William J.
Published: April 2011

Molecular dynamics (MD) simulations have been employed to study cascade overlap and defect accumulation processes during amorphization in 3C-SiC. A large number of 10 keV displacement cascades were randomly generated in a model crystal to achieve the amorphous state, and the corresponding dose is consistent with experimental observations. The results show that most defects are single interstitials and mono-vacancies at low dose, whereas the amorphous or disordered clusters, which consist of interstitials and antisite defects, appear at intermediate dose levels. These local disordered regions play an important role in the amorphization of SiC. At higher doses, a significant proportion of antisite defects is created during continued cascade overlap. The increase in interstitials and antisite defects with increasing dose suggests that the primary driving force for the crystalline-to-amorphous transition under these ion irradiation conditions in SiC is due to the accumulation of both Frenkel pairs and antisite defects.
Atomic Level Characterization of Neutron Irradiated Pressure Vessel Steels
Authors: Miller M. K. , Pareige P.
Published: April 2011

Atom probe tomography provides one of the most effective tools to characterize the solute distribution and precipitation that occurs in pressure vessel steels and associated model alloys during irradiation. The three-dimensional atom probe is able to experimentally determine the elemental identities of the atoms and their spatial coordinates with near atomic resolution so that their distribution within small volumes of the specimen can be reconstructed and analyzed. This technique together with conventional atom probe field ion microscopy has been applied to many different types of pressure vessel steels and model alloys and has revealed and characterized several different nanostructural transformations. These radiation induced or enhanced processes lead to the formation of copper-nickel-manganese-silicon-enriched precipitates, and solute segregation to dislocations, dislocation loops, nanovoids and boundaries.
On the Effect of Neutron Flux and Composition on Hardening of Reactor Pressure Vessel Steels and Model Alloys
Authors: Odette G. R. , Lucas G. E. , Klingensmith D.
Published: April 2011

Single variable experiments on a set of reactor pressure vessel and model alloys with a range of controlled compositions show a systematic effect of neutron flux (ϕ) on hardening in the intermediate fluence (ϕt) regime. The data suggest that high ϕ and enhanced recombination by vacancy trapping by solutes delays the onset of radiation-enhanced precipitation hardening.
Ion Beam Enhanced Formation and Luminescence of Si Nanoclusters from a-SiOx
Authors: Sun Yohan , Seo Se-Young , Shin Jung H. , Kim T. G. , Whang C. N. , Song J. H.
Published: April 2011

The effect of ion beams on the formation of Si nanoclusters from a-SiOx films and their luminescence properties is investigated. a-SiOx films with Si content ranging from 33 to 50 at. % were deposited by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition (ECR-PECVD) of SiH4 and O2. Prior to anneal, some samples were implanted with 380 keV Si to a dose ranging from 5.7 × 1014 cm-2 to 5.7 × 1016 cm-2. All films were rapid thermal annealed under flowing Ar environment, and hydrogenated after anneals to passivate defects and to enhance the luminescence of Si nanoclusters. For films with Si content less than 40 at. %, ion beam slightly reduces the photoluminescence (PL) intensity and induces a slight blueshift of the luminescence. For films with Si content greater than 40 at. %, ion beam greatly increases the PL intensity. Based on the effect of the ion beams dose and the ion specie, we propose that ion beams damage greatly promotes nucleation of small Si clusters from the a-SiOx matrix.
Ion-implantation Generated Nanovoids in Si and MgO Monitored by High Resolution Positron Beam Analysis
Authors: Eijt S.W.H. , Falub C.V. , van Veen A. , Schut H. , Mijnarends P.E. , van Huis M.A. , Fedorov A.V.
Published: April 2011

The formation of nanovoids in Si(100) and MgO(100) by 3He ion implantation has been studied. Contrary to Si in which the voids are generally almost spherical, in MgO nearly perfectly rectangular nanosize voids are created. Recently, the 2D-ACAR setup at the Delft Positron Research Center has been coupled to the intense reactor-based variable-energy positron beam POSH. This allows a new method of monitoring thin layers containing nanovoids or defects by depth-selective high-resolution positron beam analysis. The 2D-ACAR spectra of Si with a buried layer of nanocavities reveal the presence of two additional components, the first related to para-positronium (p-Ps) formation in the nanovoids, and a second one most likely related to unsaturated Si-bonds at the internal surface of the voids. The positronium is present in excited kinetic states with an average energy of 0.3 eV. Refilling of the cavities by means of low dose 3He implantation (1×1014 cm-2) followed by annealing reduces the formation of Ps and the width of the Ps peak in the ACAR spectrum. This width reduction is due to collisions of Ps with He atoms in the voids. In MgO, p-Ps formed with an initial energy of ∼3 eV shows a final average energy of 1.6 eV at annihilation due to collisions with the cavity walls. Possibilities of this new, non-destructive method of monitoring the sizes of cavities and the evolution of nanovoid layers will be discussed.
Atomistic models of triple junctions and the origin of topological changes in microstructural evolution
Authors: Satta Alessandra , Colombo Luciano , Cleri Fabrizio
Published: April 2011

Triple junctions are crucial elements in microstructural evolution: for example, their mobility can be rate-limiting if lower than that of grain boundaries. However, very little is known about their atomic-level structure and properties. We studied the atomic structure of multiple-twin triple junctions in silicon, formed by the convergence of two {111} and one {221} symmetric-tilt grain boundaries. Molecular dynamics simulations with the Stillinger-Weber potential and constant-traction border conditions were performed on several triple junction configurations, obtained by different combinations of the three grain boundaries. All the configurations have a positive excess line energy, a measurable volume contraction and display regions of opposite, tensile and compressive, residual stress. Moreover, we tried to elucidate the role of triple junctions as being the seeds of theonlymicroscopic events that can lead to topological changes in the microstructure. Such events, usually dubbedT1andT2in mesoscopic models, correspond to grain switching (in the Ashby-Verrall sense) and grain-disappearance events, respectively. We present preliminary results for the atomic-scale modelling of both classes of topological events and discuss the connection between atomistic and mesoscopic modelling of microstructural evolution.
From the Electronic Structure to the Macroscopic Behavior: A Multi-scale Analysis of Plasticity in Intermetallic Compounds
Authors: Fähnle Manfred , Kohlhammer Susanne , Bester Gabriel
Published: April 2011

The influence of crystal interfaces related to stacking faults on the properties of >110< superdislocations and hence on the temperature dependences of the yield stress in intermetallic compounds is investigated. This is achieved by a combination of the ab-initio density functional electron theory (which describes the electronic scale) with the generalized Peierls-Nabarro model (which describes the atomistic scale). For Pt3Al and doped Al3Ti our data do not support the hypothesis that the strong increase of the yield stress with decreasing T at low T results from sessile SISF-bound dislocation dissociations. Alternative explanations are suggested. For Ni3Al our results do not rule out the idea that Kear-Wilsdorf locks are responsible for the experimentally observed anomalous temperature dependence of the yield stress.
Simulation of the Rheology of Semisolid Alloys by Using a Two-phase Flow Approach
Authors: Ludwig A. , Wu M. , Hofmeister T.
Published: April 2011

Semisolid alloys exhibit a shear rate history dependent flow behavior. The increasing interest on numerical modeling of thixo-casting processes makes it quite important to understand the flow behavior of semisolids. Its apparent viscosity is the key parameter for the numerical models. In this paper a two phase approach is used to investigate the rheology of semisolid alloys. It is assumed that both, liquid and solid phase, can be regarded as inter-penetrating continua with its own viscosity. Thus, each phase is thought to behave as a Newtonian fluid. The simulation results show that the rheology of the two-phase flow is determined by the interaction between the solid and the liquid, i.e. the momentum exchange between the two phases. Non-Newtonian flow behavior of the solid-liquid mixture is predicted although both phases are considered as Newtonian fluids.
Critical Beha vior of a Depinning Dislocation
Authors: Zapperi Stefano , Zaiser Michael
Published: April 2011

The dynamics of dislocations at yield can be understood within the framew ork of the depinning transition of elastic manifolds in random media. Close to the threshold stress for their long-range motion, the geometry and dynamics of dislocations are characterized by a set of critical exponents. We consider a single flexible dislocation gliding through a random stress field, taking in to account long-range self stresses, and estimate the critical stress where depinning takes place. Simulations of a discretized lattice model confirm the analytical estimate and yield numerical values of the critical exponents which are in agreement with theoretical predictions for an elastic string mo ving on a plane.
Simulation of a Grain Boundary in Zirconia
Authors: Finnis Michael W. , Paxton Anthony T.
Published: April 2011

Tetragonal zirconia, (t′–ZrO2) a ferroelastic material, readily forms domains with domain boundaries on {011}. For example, by compressing a single crystal along [100] the formation and movement of such domain walls has been demonstrated experimentally. We have made atomistic simulations of a domain wall with a self-consistent tight-binding model which cor- rectly reproduces both the high temperature tetragonal to cubic phase transition exhibited by zirconia, and its low temperature monoclinic phase. We analyse the results of our simulation, in particular the width of the domain wall, in terms of a Landau–Ginzburg theory in which the order parameter measures the degree of tetragonality of the lattice
Interface Reactions in LiNbO3 Based Optoelectronics Devices
Authors: Nagata Hirotoshi , Miyama Yasuyuki , Higuma Kaoru , Hashimoto Yoshihiro , Yamamoto Futoshi , Yamane Yuuji , Yatsuki Miki
Published: April 2011

We present secondary ion mass spectrometry (SIMS) study results on interfaces of LiNbO3 based optoelectronic devices, which have been performed in order to examine the cause of device failures. The devices are widely used in current high-speed optical fiber communication systems, and such investigation from a materials-viewpoint is important to improve the device quality. Especially, the device long-term stability is strongly affected by alkali-contaminants diffused into the SiO2 buffer layer of device, and here we confirmed that an adoption of common Si3N4 passivation is effective in preventing the process-induced contamination without any influence to device performance.
Effect of Substrate Surface Structure and Deposition Conditions on the Microstructure of Tin Dioxide Thin Films Synthesized by Femtosecond Pulsed Laser Deposition
Authors: Dominguez J. E. , Fu L. , Van Rompay P. A. , Zhang Z. Y. , Nees J. A. , Pronko P. P. , Pan X. Q.
Published: April 2011

Tin oxide films were deposited on sapphire and silicon substrates using reactive femtosecond pulsed laser deposition at temperatures ranging from room temperature to 700°C. The effect of electrical discharge and background oxygen pressure on the thin film microstructure was studied. The microstructure of the films was characterized by transmission electron microscopy and x-ray diffraction. SnO2 films fabricated consist of different textures in microstructures that depend on the deposition conditions and substrate surface structures. For instance, films deposited on the (1012) sapphire (R-cut) are amorphous if deposited at room temperature, whereas films deposited at 700°C were epitaxial, single crystalline. Discharge and oxygen pressure had a strong effect on the ion/neutral ratio of the ablated plasma plume of SnO2.
Al Doped Ta2O5 Thin Films for Microelectronic Applications
Authors: Joshi P. C , Cole M. W. , Hubbard C. W. , Ngo E.
Published: April 2011

In this paper, we report on the fabrication and characterization of pure and Al doped Ta2O5 thin films fabricated by metalorganic solution deposition (MOSD) technique. The pure and Aldoped Ta2O5 thin films were fabricated by spin-coating technique using room temperature processed carboxylate-alkoxide precursor solution. The structure of the films was analyzed by xray diffraction (XRD). The surface and cross-sectional morphology of the films were examined by field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). The electrical measurements were conducted on films in MIM configuration using Pt as the top and bottom electrode. The effects of Al concentration and the post-deposition annealing temperature on the structural, dielectric, and insulating properties were analyzed. The effects of the applied bias and the measurement temperature on the dielectric and insulating properties were also analyzed to establish the stability and reliability of Al doped Ta2O5 thin films.
Electrical Properties of Doped Tin Dioxide Thin Films Deposited Using Femtosecond Pulsed Laser Ablation.
Authors: Dominguez J. E. , Fu L. , Pan X. Q.
Published: April 2011

Tin dioxide thin films are widely used as chemical sensors. The mechanism for gas sensitivity depends on the chemisorption characteristics of the oxide surface and on the electronic characteristics of thefilm. Chemical doping and the film microstructure can influence the electronic properties. In this paper tin dioxide thin films doped with rare earth and transition metals were deposited on the (1012 -oriented sapphire substrates by femtosecond pulsed laser deposition. The resulting films were single crystalline with a thickness of about 15 nm and 30 nm. The response of the films to reducing gases was measured in a gas reactor at high temperature. The electrical transport properties of the films were determined by Hall effect measurements within the gas reactor. The valence and ionic radius of dopants have strong influence on the mobility and concentration of electrical carriers (i.e. electrons) and thus affect the response of the thin films to reducing gases. A model correlating the dopant characteristics to the electrical properties was developed.
Photochemical Reduction and Oxidation Reactions on Barium Titanate Surfaces
Authors: Giocondi Jennifer L. , Rohrer Gregory S.
Published: April 2011

The influence of the ferroelectric domain structure of BaTiO3 on the photochemical reactions that occur on its surface has been examined using atomic force microscopy. Both the photochemical reduction of aqueous silver cations and the oxidation of steric acid thin films were studied. During reduction, silver selectively deposits on the surface in patterns determined by the ferroelectric domain structure. Based on the analysis of domain polarization in single crystals, we find that the photochemical reduction reaction occurs preferentially on the positive ends of the dipoles. The most likely explanation for this phenomenon is that when the static dipolar field is oriented with the positive end of the dipole on the surface, photogenerated electrons are driven to the solid-liquid interface where they reduce metal cations. The oxidation of steric acid films, on the other hand, is not spatially selective. During oxidation, the films dissipate uniformly as they are converted to CO2 and H2O. In this case, we conclude that the oxidation occurs indirectly. Photogenerated holes create hydroxyl radicals which can migrate on the surface before reacting with the steric acid molecules.
Response of the Electric Field Gradient in Ion implanted BaTiO3 to an External Electric Field
Authors: Dietrich Marc , Bartels Jörn , Deicher Manfred , Freitag Kristian , Samokhvalov Vyacheslav , Unterricker Sepp
Published: April 2011

Single crystalline, ferroelectric BaTiO3 as material with the highest piezoelectric constants among the perovskites with ordered sublattices was implanted with 111In(111Cd). The electric field gradient at the Ti position was measured with perturbed γγ-angular correlation spectroscopy (PAC) while the crystal was exposed to an external electric field. A quadratic dependence could be observed: νQ(E) = (34.8(1) + 0.16(4) E/kV/mm + 0.080(2) E2/kV2/mm2) MHz. Point charge model calculations reproduce the linear change of Vzz, but not the quadratic term. The polarizability of the host ions of BaTiO3 is known to be nonlinear with respect to an electric field. The resulting quadratic shift of the electron density is reflected in the strength of the EFG.
Preparations and Characterizations of Epitaxial SrBi2Ta2O9 Thin Films
Authors: Saito Keisuke , Mitsuya Masatoshi , Suzuki Toshimasa , Nishi Yuji , Fujimoto Masayuki , Nukaga Masanori , Yamaji Isao , Akai Takao , Funakubo Hiroshi
Published: April 2011

Epitaxial (001)-, (116)- and pseudo (103)-oriented Sr0.35Bi2.2Ta2O9 (SBT (0.35/2.2/2.0)) films were successfully grown on (001), (110) and (111) SrTiO3 substrates, respectively. High-resolution X-ray diffraction reciprocal space mapping (HRXRD-RSM) measurements and pole figure measurements clearly indicated that the (116)-oriented SBT (0.35/2.2/2.0) film consisted of two growth domains those c-axis are separated 180° apart in in-plane and pseudo (103)-oriented SBT film consisted of three growth domains those c-axis are separated 120° apart in in-plane. Moreover, lattice parameter measurements indicated that SBT films grew in fully relaxed state.
Use of an External Electric Field to Convert the Paraelectric Phase to the Ferroelectric Phase in Ultra-thin Copolymer Films of P(VDF-TrFE)
Authors: Poulsen Matt , Adenwalla S. , Ducharme Stephen , Fridkin V.M. , Palto S.P. , Petukhova N.N. , Yudin S.G.
Published: April 2011

X-ray diffraction was used to probe the structural changes associated with the conversion of the paraelectric phase to the ferroelectric phase that results from the application of a large external electric field. The samples under study are ultrathin (150 to 250 Å) Langmuir-Blodgett films of the copolymer vinylidene fluoride (70%) with trifluoroethylene (30%) deposited on aluminum-coated silicon. Theta-2theta X-ray diffraction was used to measure the change in inter-layer spacing perpendicular to the film surface. Upon heating at zero external electric field, the crystalline films undergo a structural phase transition, at 100± 5°C, from the all-trans ferroelectric phase to the trans-gauche paraelectric phase. [1,2] Above the phase transition temperature, the non-polar paraelectric phase can be converted back to the polar ferroelectric phase, in a smooth continuous process, using a large external electric field (∼1 GV/m). For example, at 100° C the ferroelectric phase first appears above 0.2 GV/m and increases steadily in proportion while the paraelectric phase decreases until complete conversion to the ferroelectric phase is achieved at approximately 0.6 GV/m.
The Physics of Electric Field Effect Thermoelectric Devices
Authors: Sandomirsky V. , Butenko A. V. , Levin R. , Schlesinger Y.
Published: April 2011

We describe here a novel approach to the subject of thermoelectric devices. The current best thermoelectrics are based on heavily doped semiconductors or semimetal alloys. We show that utilization of electric field effect or ferroelectric field effect, not only provides a new route to this problem, bypassing the drawbacks of conventional doping, but also offers significantly improved thermoelectric characteristics. We present here model calculation of the thermoelectric figure of merit in thin films of Bi and PbTe, and also discuss several realistic device designs.
Crystalline and Electrical Properties of Ferroelectric Silver Niobate-tantalate thin Films
Authors: Koh Jung-Hyuk , Khartsev S.I. , Grishin Alex , Petrovsky Vladimir
Published: April 2011

For the first time AgTa0.38Nb0.62O3 (ATN) films have been grown on the La0.7Sr0.3CoO3 (LSCO)/LaAlO3 single crystal as well as onto Pt80Ir20 (PtIr) polycrystalline substrate. Comprehensive X-ray diffraction analyses reveal epitaxial quality of ATN and LSCO films on the LaAlO3(001) substrate, while ATN/PtIr films have been found to be (001) preferentially oriented. Dielectric spectroscopy performed for ATN films and bulk ceramics in a wide temperature range 77 to 420 K shows the structural monoclinic M1-to-monoclinic M2 phase transition occurs in films at the temperature 60 °C lower than in ceramics. The tracing of the ferroelectric hysteresis P-E loops indicates the ferroelectric state in ATN films at temperatures below 125 K and yields remnant polarization of 0.4 μC/cm2 @ 77 K. Weak frequency dispersion, high temperature stability of dielectric properties as well as low processing temperature of 550 °C make ATN films to be attractive for various applications.
Thin Film Superlattices of Lead Based Relaxors
Authors: Corbett M. H. , Gregg J. M. , Bowman R. M.
Published: April 2011

Thin film capacitor structures in which the dielectric is composed of superlattices of the relaxors [0.2Pb(Zn1/3Nb2/3)O3 – 0.8BaTiO3] and Pb(Mg1/3Nb2/3)O3 have been fabricated on MgO {100} substrates by Pulsed Laser Deposition. Structural studies show dielectrics to be 100% perovskite, with strong chemical distinction between individual relaxor layers. The dielectric properties of the superlattices were investigated as a function of periodicity. Significant enhancement of the dielectric constant was observed in relatively fine-scale superlattices, consistent with previous studies. However, unlike previous work, in these relaxor superlattices dielectric enhancement is not associated with increased loss. Rather tan δ is low across the entire superlattice series. Polarisation measurements as a function of temperature suggest that the observed enhancement in dielectric constant is associated with the onset of coupled behaviour. The thickness of the individual layers in the superlattice at which coupled functional behaviour becomes apparent is ∼10nm and is comparable to that found in literature for coupled structural behaviour.
Etching Characteristics of Noble Metal Electrode
Authors: Schneider St. , Kohlstedt H. , Waser R.
Published: April 2011

The objective of this work was to develop a process to pattern noble metal electrodes. To systematically investigate possible reactive etch process regions, characterized by volatile etch products, we used a reactive ion beam etching (RIBE) tool with a filament free ICP source. This configuration gives us exact control over the beam energy and the current density, and allows to use reactive gases. An energy dispersive quadrupole mass spectrometer is fitted to the chamber for in situ monitoring.

We study the influence of the beam energy and the beam current impinging on the wafer surface as well as it's angular dependence. Several additives to the chlorinated process chemistry are investigated and characterized in terms of their role to help to increase the etch rate, maintain a vertical profile, or to enhance process selectivity.

The main focus of the study is on Platinum. Blanket films were used to describe the influence of the material, and analysis were carried out to characterize the process in terms of etch rate, residues and selectivity.
New Pt/(Bi,La)4Ti3O12/Si3N4/Si MFIS Structure for FET-Type Ferroelectric Memories by the Sol-Gel Method
Authors: Kijima Takeshi , Fujisaki Yoshihisa , Ishiwara Hiroshi
Published: April 2011

The well c-axis-oriented Bi3.25La0.75Ti3O12 films with good crystallinity and good surface morphology were obtained at temperatures higher than 600°C It was also found in a Pt / 100nm-Bi3.25La0.75Ti3O12 / 3nm-Si3N4 / Si ( metal / ferroelectric / insulator / semiconductor ) structure that C-V characteristics showed a hysteresis loop with a memory window of about 1V and both the high and low capacitance values kept at zero bias voltage did not change for more than 3 hours.
Preparation and Characterization of Ba and Nb Substituted SrBi2Ta2O9 Compounds
Authors: Das Rasmi R. , Dobal P. S. , Dixit A. , Perez W. , Tomar M.S. , Melgarejo R. E. , Katiyar Ram S.
Published: April 2011

Bi-layered ferroelectric compounds are considered most promising for non-volatile memory applications due to their high fatigue endurance. We have prepared SrBi2Ta2O9 powders with Ba (A sites) and Nb (B sites) substitutions using a novel solution based route. The powders were pressed and sintered at 1050°C to obtain high quality targets. Thin films were prepared using these ceramic targets on Pt/TiO2/SiO2/Si substrates using pulsed laser deposition (PLD) technique. The effects of growth conditions on phase formation as well as structural and electrical properties in films are studied. Initial results on films show good hysteretic characteristics. Though phase formation begins at much lower temperature, these films crystallize in a complete layered perovskite phase when prepared at 700°C. Optical phonon modes in these materials exhibit systematic variations with changing compositions. The changes in the Raman spectra are explained in terms of Ba and Nb substitutions at A and B sites, respectively. The temperature dependence of Raman spectra exhibits the substitution induced changes in the transition temperatures of these materials.
Improved Deposition Process of CVD-(Ba,Sr)TiO3 on Ru
Authors: Tarutani M. , Sato T. , Yamamuka M. , Kawahara T. , Horikawa T. , Takenaga T. , Yoneda Y. , Kuroiwa T. , Matsuno S. , Shibano T.
Published: April 2011

(Ba,Sr)TiO3 [BST] films were deposited by the flash vaporization CVD method with a unique liquid delivery system. An inductively coupled plasma mass spectrometry [ICP-MS] analysis revealed the decline of (Ba+Sr)/Ti molar ratio of the initial BST-layer on Ru. By readjusting the flow ratio of liquid sources and using a two-step deposition method, we obtained 30-nm-thick BST films with uniform composition profile, exhibiting good electrical properties. The leakage property, however, was severely deteriorated in BST films less than 24 nm thick. A SEM observation showed the presence of micro-roughness or micro-hillocks in these films, which were confirmed to be caused by Ru oxidation. Therefore, an annealing process of the Ru electrode was added for its planarization, and the CVD process was also improved. As a result, we obtained smooth and finely crystallized ∼ 20-nm-thick BST films with good electrical properties of equivalent SiO2 thickness (teq) ∼ 0.45 nm and leakage current < 1 × 10−7 A/cm2. We also measured properties of BST films deposited on the 3-D Ru electrode. The results are briefly discussed.
Transient Behavior of the Polarization in Ferroelectric Thin Film Capacitors
Authors: Lohse Oliver , Grossmann Michael , Bolten Dierk , Boettger Ulrich , Waser Rainer
Published: April 2011

The understanding of the polarization switching process of ferroelectric capacitors is highly relevant for the development and optimization of FeRAM devices. We report on the characterization of Pb(Zr,Ti)O3 thin films which have been studied by means of dedicated rectangle pulse measurements. Decreasing the voltage level of the excitation pulses decelerates the polarization switching significantly to the range of milliseconds and reduces the switchable polarization. In this work the influence of niobium (Nb) doping on the switching properties of PZT thin films prepared by CSD are investigated to reach the aspired conditions of low voltage operation, read and write access pulses in the range of nanoseconds. For the implementation of the transient behavior of ferroelectric capacitors in circuit design and simulation tools it is necessary to develop a model which precisely describes the polarization hysteresis, the pulse switching behavior as well as the small signal capacitance. The fundamental considerations for this model are presented, based on an ideal ferroelectric capacitor, taking into account the Curie-von Schweidler behavior. The latter is observed in non-ferroelectric high-K materials as well as in ferroelectric thin films.
Deformation Mechanisms of a Micro-Sized Austenitic Stainless Steel with Fine Grains
Authors: Zhang G. P. , Takashima K. , Shimojo M. , Higo Y.
Published: April 2011

In this study, deformation behavior of fine-grained austenitic stainless steel micro-cantilever beams was investigated using a newly developed testing machine for micro-sized specimens. The microbeams were deformed to different strain hardening stages of the material, and then the detailed deformation behavior on the specimen surface at the corresponding strain hardening stage was examined by scanning electron microscopy. Two deformation mechanisms corresponding to different strain hardening stages were found in the micro-sized austenitic stainless steel with fine grains. The dislocation slip mechanism characterized by the extensive dislocation slips and their interaction with grain boundaries resulted in the stage I strain hardening. With increasing deformation, the grain boundary sliding (GBS) mechanism at the stage II and subsequently intergranular cracking occurred. The differences in stress condition and work-hardening behavior on the top tension-side and rear compression-side surfaces of the micro-cantilever beam resulted in the different deformation behavior.
Corrosion Fatigue Tests of Micro-Sized Specimens
Authors: Mizutani Y. , Higo Y. , Ichikawa Y. , Morita A. , Takashima K. , Swain M.V.
Published: April 2011

Corrosion fatigue properties of micro-sized materials are extremely important to design MEMS devices and micro-machines used in corrosive environments. However, there have been few studies that investigate corrosion fatigue properties of micro-sized materials. Thus, it is necessary to develop a corrosion fatigue test method for micro-sized materials. However, there are several difficulties in corrosion fatigue tests on micro-sized specimens. It is also necessary to clarify the problems for the method and to find their solutions. In this investigation, a corrosion fatigue test method for micro-sized specimens has been developed and corrosion fatigue tests for micro-sized Ni-P amorphous alloy specimens have been carried out in a 0.9% NaCl solution. Specimens of cantilever-beam-type with dimensions of 10 × 12 × 50 μm3 were prepared from a Ni-P amorphous thin film by focused ion beam machining. Corrosion fatigue tests on the micro-sized specimens were succeeded, and environmental effects on fatigue properties of micro-sized specimens were clearly observed. Several problems and solutions for the method were described.