bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic Property Estimation in Polycrystalline Films with Crystallographic Texture and Grain Shape
Authors: Hendrix B. C. , Yu L. G. , Xu K. W. , He J. W.
Published: April 2011

Although methods of measuring the elastic properties of thin films have made great advances with the use of bulge testing of membranes, deflection of micromachined beams, and nanoindentation, most results are still being compared to either isotropic or single crystal elastic constants, neither of which are, in general, appropriate for textured polycrystalline films. This paper uses recent results of a self-consistent model (after Krbner and Kneer) which calculates the elastic anisotropy arising from crystallographic texture and which has been extended to predict the anisotropy resulting from grain shape. These results are compared to the various Voigt, Reuss, and Hill approximations that are appropriate for different crystallographic textures. The accuracies of the different models are evaluated in terms of their ability to predict the biaxial modulus and indentation compliance that are most commonly measured in thin films.
Investigation of Aluminum Thin Films Using Electron Backscatter Diffraction and the New Technique of Orientation Imaging Microscopy
Authors: Dingley D. J. , Field D. P.
Published: April 2011

Aluminum thin films deposited onto silicon substrates coated with silicon dioxide or a layered structure of titanium and titanium nitride have been investigated using the combined techniques of electron backscatter diffraction and orientation imaging microscopy. By these methods the local texture and spatial distribution of texture components was established. It was observed that whereas the material exhibited an overall <111> texture with the in-plane direction <110> uniformly distributed, there were variations in the local texture and distribution of orientations with clustering of grains of similar orientation. Individual grains within the clusters were nearly perfect and varied in orientation by only a few degrees. The effective grain size differed greatly on whether the cluster size of similarly oriented grains or the diameter of individual grains within the cluster was considered to constitute the grain structure. No strong bias was found in favor of coincident site oriented grain pairs though in some cases the frequency of occurrence of low angle boundaries was less than is expected on a purely random basis. Additional experiments were carried out in order to establish the suitability of orientation imaging microscopy for microstructure characterization of interconnect lines in integrated semiconductor device technology.
Rodrigues-Frank Space Representations of Fiber Texture
Authors: Rajan Krishna , Petkie Ronald
Published: April 2011

The concept of fcc fiber texture is examined in the context of Rodrigues-Frank (R-F) representations. Using fiber texture in thin films as the basis of our analysis, it is shown that this approach when combined with grain specific determination of crystallographic orientation provides a useful means of detecting a number of texture components with relatively small grain sampling densities. The application of R-F representations is also shown to be a useful methodology to couple grain boundary structure information with microtexture data.
Characterizing Surfaces and Overlying Multilayer Structures Using Grazing Incidence X-Ray Reflectivity
Authors: Pedulla Joseph , Deslates Richard D. , Joensen Karsten D. , Gorenstein Paul
Published: April 2011

A proposed hard x-ray (>10 keV) telescope design uses multilayers on gold coated replica substrates. We investigated the grazing incidence x-ray reflectivity (0.154 nm) of super polished fused silica, gold coated fused silica, and mutilayers deposited on each. Gold coatings of 100 nm were deposited by both magnetron sputtering and ion beam sputtering. Carbon/nickel multilayers (20 layer pair with 4.0 nm d-spacing) were deposited by ion beam sputtering. We report the results of specular and diffuse reflectivity characterizations of these samples. The easured x-ray reflectivities are compared to model calculations evaluating film thickness, ensity, optical properties, and interface roughness/diffusion. It is concluded that substrate and film quality (roughness and density) can be determined by grazing incidence reflectivity measurements and correlated to final multilayer reflectivity and model calculations.
Synthesis and Properties of Crystalline Carbon Nitride Composite Superhard Coatings
Authors: Chung Yip-Wah
Published: April 2011

Multilayer carbon nitride/TiN coatings were synthesized using a dual-cathode dc magnetron sputtering system. Fully crystalline films can be obtained when the thickness of the carbon nitride component is on the order of one nm. There appears to be a strong correlation between the occurrence of strong TiN(111) texture and the hardness of these multilayer coatings, as controlled by target powers, nitrogen partial pressure and substrate bias. These coatings can be synthesized at near room temperatures, with smooth surface morphology and hardness in the range of 45–55 GPa.
Surface Morphology and Microstructure of Al-O Alloys Grown by ECR Plasma Deposition
Authors: Marshall D. A. , Barbour J. C. , Follstaedt D. M. , Howard A. J. , Lad R. J.
Published: April 2011

The growth of polycrystalline and amorphous aluminum-oxygen alloy films using electronbeam evaporation of Al in the presence of an O2 electron-cyclotron-resonance (ECR) plasma was investigated for film compositions varying from 40% Al (A12O3) to near 100% Al (A1Ox). Processing parameters such as deposition temperature and ion energy were varied to study their effects on surface texture and film microstructure. The Al-rich films (AlOx) contain polycrystalline fcc Al grains with finely dispersed second-phase particles of γ-A12O3 (1–2 nm in size). The surface roughness of these films was measured by atomic force microscopy and found to increase with sample bias and deposition temperature. Stoichiometric A12O3 films grown at 100°C and 400°C without an applied bias were amorphous, while an applied bias of -140 V formed a nanocrystalline γ-A12O3 film at 400°C. The surface roughness of the A12O3 increased with temperature while ion irradiation produced a smoother surface
On Superstoichiometric Ti-C, Si-C and Ta-C PVD Coatings
Authors: Knotek O. , Lugscheider E. , Löffler F. , Barimani C.
Published: April 2011

Different PVD coatings are used to reduce the wear of tools and other machine parts, and to improve their service life [1]. During the last years, a number of developments have been made in the field of carbon coatings. These coatings show a low friction coefficient, e.g. against steel, and therefore have a high potential in decreasing the friction and wear of coatings in tribological applications. This PVD process can be stabilised by using a metallic target which is vaporised in a carbon and hydrogen atmosphere. The carbon rich side of the metal/carbon system is object of this study.
Slightly superstoichiometric coatings in the range of 50–60% carbon content have very good friction properties too and with the potential to better film properties (coating adhesion due to internal stress, microhardness). In this paper the mechanical properties of coatings in the systems Ti-C, Si-C and Ta-C are described and the different microstructures are discussed.
Microstructural Characterization of a Zirconia-Titania-Yttria Thermal Barrier Coating
Authors: Diaz P. , Ralph B. , Edirisinghe M. J.
Published: April 2011

The phase transformations in a plasma sprayed zirconia-titania-yttria thermal barrier coating (TBC), subjected to different thermal treatments, in the temperature range 900–1400°C, were characterized by X-ray diffraction (XRD). Different transformation trends dependent on the cooling rate of the specimens from the treatment temperature, were observed. The study of the fracture surfaces of the as-sprayed and thermally treated ceramic coatings, using scanning electron microscopy (SEM), allows elucidation of the changes in the microstructure and the fracture mechanisms. The as-sprayed and thermally treated (1400°C) ceramic microstructures were also studied using transmission electron microscopy (TEM).
Rapid Thermal Chemical Vapor Deposition of Polycrystalline Silicon-Germanium Films on SiO2 and Their Properties
Authors: Li V. Z-Q , Mirabedini M. R. , Kuehn R. T. , Gladden D. , Batchelor D. , Christenson K. , Wortman J. J. , Ozturk M. C. , Maher D. M.
Published: April 2011

In this work, polycrystalline SiGe has been viewed as an alternative gate material to polysilicon in single wafer processing for the deep submicrometer VLSI applications. We studied deposition of the silicon-germanium (SiGe) films with different germanium concentrations (up to 85%) on SiO2 in a rapid thermal chemical vapor deposition reactor using GeH4 and SiH4/H2 gas mixture with the temperature ranging from 550°C to 625°C. Since the SiGe RTCVD process is selective toward oxide and does not form nucleation sites on the oxide easily, an in-situ polysilicon flash technique is used to provide the necessary nucleation sites for the deposition of SiGe films with high germanium content. It was observed that with the in-situ polysilicon flash as a pre-nucleation seed, the SiGe deposited on SiO2 forms a continuous polycrystalline layer. Polycrystalline SiGe films of about 2000Å in thickness have a columnar grain structure with a grain size of approximately 1000Å. Compositional analyses from Auger Electron Spectroscopy (AES) and Rutherford backscattering (RBS) show that the high germanium incorporation in the SiGe films has a weak dependence on the deposition temperature. It is also noted that the germanium content across the film thickness is fairly constant which is a critical factor for the application of SiGe films as the gate material. Lastly, we found that the surface morphology of SiGe films become smoother at lower deposition temperature.
Crystalline Grains and Electrical Properties of Vacuumevaporated SnO2Thin Films
Authors: Man W. K. , Yan H. , Wong S. P. , Wong T. K. S. , Wilson I. H.
Published: April 2011

We have studied grain growth and electrical properties of polycrystalline tin oxide (SnO2) thin films prepared by vacuum-evaporation with a two-step process: evaporation of tin metal films and then oxidation of these metal films. Surface morphology of the SnO2thin films was observed by atomic force microscopy. The grain size of the SnO2thin films is found to increase with the film thickness and oxidation temperature. Kinetics of the grain growth is discussed in terms of a 3-dimensional diffusion limited process. The diode current-voltage (I-V) characteristic of the SnO2/Si heterojunctions (isotype and anisotype) was measured in the temperature range of 14K-383K. Changes in the diode ideality factor and threshold voltage with temperature are discussed. In addition, we present ambient tunnelling I-V results measured from individual SnO2grains.
Reactive Phase Formation in Thin Films: Evolution of Grain Structure
Authors: Barmak K. , Michaelsent C. , Rickman J. , Dahmstt M.
Published: April 2011

It is a well known fact that the properties and performance of polycrystalline materials, including polycrystalline thin films, are strongly affected by the grain structure. Therefore, in treating reactive phase formation in these films, it is (or it will inevitably be) necessary to quantify the grain structure of reactant and product phases and its evolution during the course of the reaction. Theoretical models and the conventional view of thin film reactions, however, have been largely extensions, to small and finite dimensions, of theories and descriptions developed for bulk diffusion couples. These models and descriptions primarily focus on the growth stage and to a much lesser extent on the nucleation stage. Consequently, these models and descriptions are not able to treat the development of product phase grain structure. Recent calorimetric investigations of several thin film systems demonstrate the importance of nucleation kinetics (and hence nucleation barriers) in product phase formation and provide quantitative measures of the thermodynamics and kinetics of formation of the product phases, thereby allowing some degree of comparison with reaction models. Furthermore, microstructural investigations of thin-film reactions demonstrate the non-planarity of the growth front and highlight the role of reactant-phase grain boundaries. In this paper, a summary of these experimental studies and recent theoretical treatments, which combine nucleation and growth in an integrated manner, is presented, with particular emphasis on the Nb/Al system. These experiments and models lead to a new view of reactive phase formation and grain structure evolution as one in which the latter is an integral part of the former. Based on this view, directions for future research are discussed.
Stress Induced During the Solid-phase Crystallization of Amorphous Silicon Deposited by LPCVD
Authors: Mohammed-Brahim T. , Kis-Sion K. , Briand D. , Sarret M. , Lebihan F. , Fortin B.
Published: April 2011

The Solid Phase Crystallization (SPC) of amorphous silicon films deposited by Low Pressure Chemical Vapor phase Deposition (LPCVD) using pure silane at 550'C was studied by in-situ monitoring the film conductance. The saturation of the conductance at the end of the crystallization process is found transient. The conductance decreases slowly after the onset of the saturation. This degradation is also observed from other analyses such as ellipsometry spectra, optical transmission and Arrhenius plots of the conductivity between 250 and 570K. Hall effect measurements show that the degradation is due to a decrease of the free carrier concentration n and not to a decrease of the mobility. This indicates a constant barrier height at the grain boundaries. The decrease of n is then due to a defect creation in the grain. Hence, whatever the substrate used, an optimum crystallization time exists. It depends on the amorphous quality film which is determined by the deposition techniques and conditions and on the crystallization parameters.
Optical Transmittance of Thin Films of SrFeO2.5+x at Elevated Temperatures and Applications to Gas Sensing
Authors: Post Michael , Yao Jianhua
Published: April 2011

Non-stoichiometric perovskites with the general formula SrFeO2.5+x have potential in oxygen sensing applications. Thin films of these compositions have been grown onto various substrates by pulsed laser deposition techniques. At elevated temperatures, (T > 550K), the films react rapidly and reversibly with oxygen and the bulk oxygen content, x, of the films changes. Accompanying the change in oxygen stoichiometry are significant changes in the optical transmittance and reflectance of the films. Transmission spectrophotometry in the uv-vis region has been used to determine the relationship of transmittance with oxygen composition in the gas phase. Spectrophotometric data have been obtained by a batch method and also in-situ in a flow cell at T = 690K. The data show a large variation in transmittance, exceeding 103 for the batch measurements, with SrFeO3 showing the highest opacity. The design of the flow cell is also described.
Structural and Magnetic Properties of γ-Fe2O3 Particles Coated with TiO2
Authors: Borodko Y. G. , Bokhimi  , Acosta D. , Ioffe L. M. , Viveros T. , Bosch P. , Nava N.
Published: April 2011

The surface of single-domain acicular magnetic gamma-Fe203 particles was coated with titania shell and the effect of this coating on the remanent induction and coercive force was measured.
Mechanism of Thermally Assisted Creep Crack Growth
Authors: Golubović Leonardo , Moldovan Dorel
Published: April 2011

We use atomistic Monte-Carlo simulations to investigate the dynamics of cracks which sizes are smaller than the Griffith length. We demonstrate that such cracks can irreversibly grow proviso their size is larger than a certain critical length which is smaller than the Griffith length, as recently suggested [ L. Golubović and A. Peredera, Phys. Rev. E51, 2799 (1995)]. We show here that this thermally assisted creep crack growth is dominated by irreversible changes in the region of the crack tip, primarily in the form of dislocation emissions and nucleation of microcavities and voids. These processes act together during the crack growth: the crack tip region acts as a source for emissions of dislocations which subsequently serve as seeds for creation of vacancy clusters in a region away but still close to the crack tip. Eventually, passages between these vacancy clusters and the mother crack are formed and the crack thus increases in size. As this process repeats, the crack grows.
Bonding and Vibrational Properties of CO-Adsorbed Copper
Authors: Lewis Steven P. , Rapp Andrew M.
Published: April 2011

Accurate density functional calculations are performed to investigate the structure and vibrational dynamics of carbon monoxide adsorbed to the (100) surface of copper. The adsorbate and substrate are considered as a unified system, with atoms of each treated on an equal footing. Coupling between the two components is found to have a significant effect. In particular, frustrated translational motion mixes strongly with transverse phonons of the substrate to form a broad resonance. Direct computation of anharmonic coupling between the internal CO bond stretching mode and other adsorbate-weighted modes confirms the experimental conclusion that the transient CO-stretch response seen in recent pump-probe studies is an indirect probe of the transient dynamics of frustrated translations. In this light, the computed resonance between this mode and substrate phonons suggests a dephasing mechanism to account for the observed relaxation dynamics.
Spatial Redistribution of Niobium Additives Near Nickel Surfaces
Authors: Muratov Leonid S. , Cooper Bernard R.
Published: April 2011

The spatial redistribution of niobium atoms near the surface of pure nickel has been considered in the low niobium concentration limit. The calculation of free energy includes lattice relaxation around niobium atoms by using molecular dynamics (MD) incorporating atomistic potentials based on ab-initio quantum mechanical calculations and includes vibrational entropy phenomenologically within the local harmonic approximation.
First-Principles Simulations of Interstitial Atoms in Ionic Solids
Authors: Kotomin E. A. , Svane A. , Brudevoll T. , Schulz W. , Christensen N. E.
Published: April 2011

The atomic and electronic structure of the radiation-induced interstitial atoms in MgO and KCl crystals representing two broad classes of ionic solids are calculated and compared. The first-principles full potential LMTO method is applied to a 16-atom supercell. For both crystals the energetically most favourable configuration is a dumbbell centered at a regular anion site. Its (110) and (111) orientations are very close in energy which permits the dumbbell to rotate easily on a lattice site. The mechanism and the relevant activation energy for thermally activated diffusion hops from the dumbbell equilibrium position to the cube face and cube center are discussed in the light of the available experimental data for MgO. In order to interpret recent experimental data on Raman spectroscopy, the local vibrational frequences are calculated for the dumbbell in KCl (the so-called H center). A strong coupling is found between its stretching molecular mode and the breathing mode of the nearest cations whose frequency is predicted.
High Toughness Alumina/Aluminate: The Role Of Hetero-Interfaces
Authors: Brito M. E. , Yasuoka M. , Kanzaki S.
Published: April 2011

Silica doped alumina/aluminate materials present a combination of high strength and high toughness not achieved before in other alumina systems, except for transformation toughened alumina. We have associated the increase in toughness to crack bridging by anisotropically grown alumina grains with concurrent interfacial debonding of these grains. A HREM study of grain boundaries and hetero-interface structures in this material shows the absence of amorphous phases at grain boundaries. Local Auger electron analysis of fractured surfaces revealed the coexistence of Si and La at the grain facets exposed by the noticeable intergranular fracture mode of this material. It is concluded that a certain and important degree of boundaries weakness is related to both, presence of Si at the interfaces and existence of alumina/aluminate hetero-interfaces.
Scaling Of Fracture In Quasibrittle Materials And The Question Of Possible Influence Of Fractal Morphology
Authors: Bažant Zdeněk P.
Published: April 2011

The paper presents a review of recent results on the problem of size effect (or the scaling problem) in nonlinear fracture mechanics of quasibrittle materials and on the validity or recent claims that the observed size effect may be caused by the fractal nature of crack surfaces. The problem of scaling is approached through dimensional analysis and asymptotic matching. Large-size and small-size asymptotic expansions of the size effect on the nominal strength of structures are presented, considering not only specimens with large notches (or traction-free cracks) but also structures with no notches. Simple size effect formulas matching the required asymptotic properties are given. Regarding the fractal nature of crack surfaces, it is concluded that it cannot be the cause of the observed size effect.
Fracture Surfaces in 3D Fuse Networks
Authors: Räisänen V. I. , Alava M. J. , Nieminen R. M.
Published: April 2011

We study a 3D random fuse network model with computer simulations. The breaking thresholds are distributed randomly, corresponding to quenched disorder. We find for the roughness exponent of the final fracture surface ζ = 0.47 ± 0.19, which is close both the minimum energy surface value and the directed percolation depinning model value in 2+1 dimensions. It is also similar to results from measurements of fracture surfaces at nanometer scale, and from experiments in which the fracture process occurs slowly as in fatique. The traditional measure of damage, the number of broken bonds grows faster than the area effect (nb ˜ L2.28), with no signs of a trivally brittle regime.
Crack Growth and Propagation in Metallic Alloys
Authors: Morrey W. C. , Wille L. T.
Published: April 2011

Using large-scale molecular dynamics simulation on a massively parallel computer, we have studied the initiation of cracking in a Monel-like alloy of Cu-Ni. In a low temperature 2D sample, fracture from a notch starts at a little beyond 2.5% critical strain when the propagation direction is perpendicular to a cleavage plane. We discuss a method of characterizing crack tip position using a measure of area around the crack tip.
New Polymer Precursors To SiNCB Materials
Authors: Wideman T. , SU K. , Remsen E. E. , Zank G. A. , Sneddon L. G.
Published: April 2011

The first borazine/silazane backbone copolymers derived from the parent borazine, B3N3H6, have been obtained by the thermal condensation of borazine with either of two silazanes, tris(trimethylsilylamino)silane (TTS) or 1,1,3,3,5,5- hexamethylcyclotrisilazane (HCT), to yield copolymers of typical composition (B3N3H4)1.00(N)1.17(SiMe 3)1.16 (SiH)0.34 and (B3N3H4) 1.00(N) 1.67(SiMe 2)1.49(H) 1.5, respectively. Despite their similar compositions, upon pyrolysis the TTS copolymers yield B1.0N1.0Si<0.2 ceramics, while the ceramics derived from the HCT copolymers showed greater retention of silicon and carbon with typical compositions of B1.0N1.5Si0.4C0.2 The XRD spectra show the materials are amorphous to 1400 °C, but show crystalline phases of β-Si3N4, °C, with no diffraction from any boron-containing species. The DRIFT spectra of the ceramics, however, indicate the presence of boron nitride.
Qualitative and Quantitative Analysis of Stacking Disorder in α-and β-SiC by X-ray Diffraction and Structure Modeling
Authors: Palosz Bogdan , Stel'makh Svetlana , Gierlotka Stanislaw
Published: April 2011

A method of analysis of disordering in α- and β-SiC polycrystals by numerical modeling, and a simulation of X-ray diffraction profiles are presented. The diffraction patterns of nonperiodic structures were simulated for models of 2000 layer fragments of the structure. Computer generation of the models was based on the Poisson function describing the size distribution of the domains of basic polytypes and faults. The models were quantified by a set of input probability parameters describing relative frequencies of the occurrence of the domains of polytypes and faults. Implementation of a correlation parameter that characterizes coherence of sequential domains of a given polytype assures a good reproducibility of the simulated diffraction profiles obtained for the same set of the model parameters. Based on this method, a quantitative analysis of disordering in polycrystals of SiC annealed in the temperature range 1100–2200 °C was performed.
Plasma Enhanced Chemical Vapor Deposition of Zirconium Nitride Thin Films
Authors: Atagi Lauren M. , Samuels John A. , Smith David C. , Hoffman David M.
Published: April 2011

Depositions of high quality zirconium nitride, (Zr3N4), films using the metal-organic precursor Zr(Net2)4 were carried out in a microwave argon/ammonia plasma (2.45 GHz). The films were deposited on crystalline silicon wafers and quartz substrates at temperatures of 200–400 °C. The transparent yellow films have resistivity values greater than MΩ cm. The stoichiometry is N/Zr = 1.3, with less than 5 atom % carbon and little of no oxygen. The hydrogen content is less than 9 atom %, and it does not vary with deposition temperature. The growth rates range from 600 to 1200 Å/min, depending on the flow rates and precursor bubbler temperature. X-ray diffraction studies show a Zr3N4 film deposited at 400 °C is polycrystalline with some (220) orientation. The crystallite size is approximately 30 Å. The band gap, as estimated from transmission spectra, is 3.1 eV.
Ternary Bismuth Chalcogenides for Thermoelectric Applications. Synthesis and Charge Transport Properties of New Compounds in the K-BI-S System.
Authors: Kanatzidis Mercouri G. , McCarthy Timothy J. , Tanzer Troy A. , Chen Li-H. , Hogan Tim , Kannewurf Carl R. , Iordanidis Lykourgos
Published: April 2011

KBi6.33S10 and K2Bi8S13 were synthesized by the direct combination of K2S/Bi2S3 at high temperature (>700°C). The reaction of K2S/3.3Bi2S3 at 800°C revealed the presence of a new ternary sulfide KBi6.33S10 (I) (92% yield). The structure consists of blocks of Bi2Te3 and Cdl2-type units that are connected to form a three-dimensional network with K+ ions located in the channels that run along the b-axis. The same reaction but with a different ratio, at 750°C, gave the new ternary sulfide K2Bi8S13 (II) (94% yield). The structure of the shiny rod-like crystals is closely related to that of I. As in I, it also consists of Bi2Te3 and Cdl2-type fragments that connect to form K+-filled channels. The two potassium atoms and one bismuth atom are disordered over three sites. Some preliminary electrical and optical properties of these materials are discussed.
Kinetics of Reactions Between Silica and Carbon and the Formation of Silicon Carbide
Authors: Wiik Kjell , Motzfeldt Ketil
Published: April 2011

The reactions taking place between coarse grained mixtures of silica (cristobalite) and carbon (graphite) at 1558°C in pure CO as well as mixtures of CO and Ar, have been subjected to a thermogravimetric investigation. A model is developed in the regime where the formation of SiC does not take place. The primary steps are assumed to be: Reaction betweefn SiO2 and CO to give SiO(g) and CO2 followed by the reaction between CO2 and C to give CO. The model predicts the prevailing partial pressure of SiO throughout the charge, and the correlation between observations and model strongly supports the above given reaction mechanism.

Enhanced and accelerating reaction rates were observed when the formation of β-SiC took place. It is suggested that this is due to the continuous formation of stable SiC-nucleus on the Csurface and the subsequent shortening of the diffusion path for SiO.
Silicon Nanotechnology for Biofiltration and Immunoisolated Cell Xenografts
Authors: Ferrari M. , Chu IW. , Desai IT. , Hansford D. , Mazzoni G. , Huen T. , Zhang M.
Published: April 2011

Silicon-based clean-room technology is employed for the microfabrication of a particle filter with uniform pore dimensions in the 20-40-nm range. Surface and bulk micromachining are integrated in the fabrication process, resulting in a filtering membrane with large active area, flow rate and resistance to pressure. The microfabricated membrane is especially suitable for biofluid purification, including viral elimination. The nanofilter is a technological precursor for a microfabricated, silicon-based capsule to be employed in the reaction-free xenotransplantation of cells. Results are presented below that address the issue of biocompatibility of the microfabricated capsule components and materials.
Osteoconduction on, and Bonding to, Calcium Phosphate Ceramic Implants
Authors: Dziedzic D. M. , Savva I. H. , Wilkinson D. S. , Davies J. E.
Published: April 2011

Calcium phosphate ceramic blocks of three different densities, porous, intermediate and dense, were prepared by tape casting (total = 18), and implanted in the femora of 9 Wistar rats for 1 to 3 weeks. Following fixation, the tissue was prepared for examination by scanning electron microscopy (SEM) of freeze fractured specimens, or back-scattered electron imaging (BSEI) of polymethylmethacrylate (PMMA) embedded, undecalcified, sections. The results demonstrated that while all ceramics were osteoconductive, the 93 % dense implants showed no evidence of bone bonding as judged by the plane at which specimens separated or cracked during preparation for microscopy. The porous ceramics, on whose surfaces both multinucleated cells and osteoid tissue were observed at all implantation times, exhibited less bone contact than the other two groups. Both SEM and BSEI showed that there was bone growth into the microporosity of both intermediate and porous ceramics, pore size range 1−2μ m, to a depth of about 6μm. The latter corresponds to the thickness of natural bone lamellae. In all implants examined,de novobone formed on the ceramic surface by the initial production of a biological cement-line like interfacial extracellular matrix. The results clearly show that osteoconduction and bone-bonding are distinct mechanistic phenomena. While we assume the former to be a consequence of protein adsorption events culminating in anchorage of osteoblasts to the implant surface, the latter is the result of mechanical interdigitation of the extracellular matrix, produced by osteoblasts, with the microtopography of the implant surface.
Self-Assembling Peptide Monolayers: Endothelial Cell Behavior on Functionalized Metal Substrates
Authors: Chaikof E.L. , Wang H. S. , Wingert T. M. , Stephens S. , Dluhy R. A.
Published: April 2011

Despite the high initial success rate with metallic stents for the treatment of a variety of vascular lesions, problems have included occlusion due to thrombus formation or intimal proliferation. Improving the biological behavior of these and other other implantable metallic devices may require the use of biomimetic peptide coatings which promote specific cellular responses at the biological-materials interface.

Thiol-terminated peptides, without the addition of a cysteine residue, were synthesized by a modification of standard solid phase methodology. Gold/mica or gold/glass surfaces were exposed for 6 hours at 23 °C to one of three peptide solutions: GRGD(βA)3YNH(CH2)2SH (RGD); (βA)6NH (CH2)2SH (bAla); or a 1:1 mix of both peptides. Peptide films were examined by external reflectance infrared (IR) spectroscopy and atomic force microscopy (AFM) which confirmed the presence of unique close-packed structures for bAla and the 1:1 mix. Endothelial cell proliferative, migratory, and adhesive behavior were evaluated using 3H-thymidine and 51Cr labeling techniques, respectively. Cell proliferation, migration, and adhesion were significantly higher on RGD containing peptide films.

Well-ordered protein assemblies on metallic substrates can be produced with the proper choice of peptide chain structure and terminal residues. Biological activity is a function of film composition and oligopeptide pendant structure.
Apatite Nucleation on Low Porosity Silicon in Acellular Simulated Body Fluids
Authors: Canham L T , Reeves C L
Published: April 2011

The response of a range of porous Si films to acellular simulated body fluids has been monitored by SEM, EDX and FTIR analyses. Quite low levels of porosity are shown here to induce hydroxyapatite growth both on top of the film, and even on neighbouring areas of bulk Si, which in isolation have no such effect. The in-vitro demonstration of hydroxyapatite nucleation by a porous semiconductor could provide further insight into the phenomenon of bioactivity and help realise a broader range of bioactive materials.
Method for Calculation of Dielectric Properties of Modulated Semiconducting Structures
Authors: Mirovitskii V. Yu. , Mashtakov O. Yu.
Published: April 2011

A new method for calculation the effects of composition modulation upon the dielectric properties of semiconductors is proposed. Specific consideration is carried out for ultrathin [001] oriented (AIIICV)m(BIIICV)n superlattices (SL). These SL are formally considered to result from complete A(B) atoms orderiig over a-sublattice in a hypothetical initial structure –bulk mixed crystal (AxB1−x)C with zincblende lattice and x = m/(m + n). From this point of view a variation in dielectric constants tensor (DCT) induced by the ordering can be calculated nearly in a spirit of the phenomenological Landau theory of second-order phase transitions. It is shown that the changes in spatial dispersion of the DCT are expressed through the coefficients at invariants in the expansion of SL thermodynamic potential in a power series of the order parameter components. The way is described for numerical estimation of the thermodynamic potential coefficients from microscopic model of the initial alloy which take account of spatial correlations in A(B) atoms distribution.
Growth of Uniform InGaAs Bulk Crystal by Multi-Component Zone Melting Method
Authors: Kusunoki T. , Nakajima K. , Shoji H. , Suzuki T.
Published: April 2011

We have developed a Multi-component Zone Melting method to grow a ternary compound crystal which has a uniform composition. A 4.5 mm long InGaAs bulk crystal with a uniform InAs composition of 0.3 has been successfully grown using this method. InGaAlAs/InGaAs strained quantum well lasers were fabricated on an In0. 2Ga0.8As substrate which was grown by this method. A minimum threshold current density of 280 A/cm2 was achieved.
A New Structure Design “Multiple-Quantum Barrier in Active Region” for High Temperature Operation of AlGaAs Superluminescent Diode
Authors: Kumar Rajesh , Kuno Hironari , Tomita Kazuyoshi , Hara Kunihiko
Published: April 2011

A multiple-quantum barrier (MQB) structure has been applied to AlGaAs superluminescent diode (SLD) to suppress the electron overflow from active to cladding region at elevated temperatures. It was found that the presence of MQB in the p-cladding region leads to stagnant hole transport to the active region. To improve the hole transportation, we propose a new quantum structure for active region. In this design, the superlattice structure MQB is located in the middle of active region which allows smooth hole injection to the active from the cladding region. Carriers can reach both side of the MQB structure in the active region by tunneling phenomenon which critically depends on the barrier thickness. Simulation results show that low energy electrons can tunnel through the MQB barriers, while high energy electrons are reflected back by effective barrier. Finally, multiple-quantum well (MQW) structure is integrated at each side of MQB to minimize the possible over-flow of tunneled electrons and to improve the radiative efficiency of the SLD device. Experimental data support the visibility of the proposed ‘MQB+MQW in Active’ structure at elevated temperatures.
The Role of Adsorbed Water Molecules in Bulk Restructuring of Amorphous Tungsten Trioxide Films
Authors: Shiyanovskaya I. V.
Published: April 2011

The influence of water molecules adsorbed at the surface of electrochromic WO3 films on film stability in aqueous electrolyte has been studied by scanning electron microscopy and high energy electron diffraction.
Sputtered SiO2:C Films Showing Visible Photoluminescence
Authors: Sendova-Vassileva M. , Tzenov N. , Dimova-Malinovska D. , Josepovits K. V.
Published: April 2011

Luminescent a-Si:O:C layers were obtained by magnetron co-sputtering and annealing. Maximum photoluminescence intensity is comparable to that of porous silicon. Luminescence maximum is between 1.8 eV and 2.2 eV. X-ray photoelectron spectroscopy (XPS) finds Si-O, C-Si and C-C bonding. Secondary ion mass spectrometry(SIMS) data are presented.
New Technique for Ohmic Formation
Authors: Hara S. , Teraji T. , Okushi H. , Kajimura K.
Published: April 2011

We propose a new systematical method to control Schottky barrier heights of metal/semiconductor interfaces by controlling the density of interface electronic states and the number of charges in the states. The density of interface states is controlled by changing the density of surface electronic states, which is controlled by surface hydrogenation and flattening the surface atomically. We apply establishing hydrogen termination techniques using a chemical solution, pH controlled buffered HF or hot water. Also, slow oxidation by oxygen gas was used to flatten resultant semiconductor surfaces. The density of interface charges is changeable by controlling a metal work function. When the density of surface states is reduced enough to unpin the Fermi level, the barrier height is determined simply by the difference between the work function of a metal φm and the flat-band semiconductor ØsFB. In such an interface with the low density of interface states, an Ohmic contact with a zero barrier height is formed when we select a metal with φm < φsFB. We have already demonstrated controlling Schottky and Ohmic properties by changing the pinning degree on silicon carbide (0001) surfaces. Further, on an atomically-flat Si(111) surface with monohydride termination, we have observed the lowering of an Al barrier height.
Comparison of TiN films produced by TDEAT (Ti[N(C2H5)2]4), TDMAT (Ti[N(CH3)2]4), and a new precursor TEMAT (Ti[N(CH3)C2H5]4)
Authors: Lee J-G , Kim J-H , Shin H-K , Park S-J , Yun S-J , Kim G-H
Published: April 2011

TiN films have been deposited by chemical vapor deposition (CVD) from a new TiN precursor, tetrakis(ethylmethylamino)titanium (TEMAT), and compared with those from tetrakis(diethylamino)titanium (TDEAT) and tetrakis(dimethylamino)titanium (TDMAT) in terms of film quality and conformality. The TDEAT process at 350°C provides films with low resistivity of ˜2500μΩ-cm and 30% carbon. In addition, films deposited from TDEAT contain no oxygen and show good stability in resistivity with time. Furthermore, this process provides bottom-coverage ranging from 65% at 275°C to 30% at 350°C. In contrast, excellent bottom-coverage of ˜90% over 0.5μΩ contact holes is obtained by the TDMAT process. However, films deposited from TDMAT are air-reactive upon air-exposure, resulting in a large increase in resistivity when exposed to air. The use of TEMAT, possessing physical properties between those of TDMAT and TDEAT, allows less air-reactive and better crystalline films, compared with TiN films from TDMAT. It is also observed that the carbon level is ˜2x lower than that in TiN films from TDEAT. Futhermore, this process provides good step-coverage in 0.35μΩ contacts with an aspect ratio of 2.9. Consequently, the TEMAT process can be an attractive choice for sub-0.5 μΩ application.
Fabrication of Dual-Damascene Structures in Low Dielectric Constant Polymers for Multilevel Interconnects
Authors: Tacito R. , Steinbrüchel C.
Published: April 2011

Parylene-n (pa-n) and benzocyclobutene (BCB) are novel candidate materials for interlevel dielectrics in future multilevel interconnects, due to their dielectric constant being much lower than that of silicon dioxide. We describe the fine line patterning of these materials by reactive ion etching in O2/CF4 plasmas. Examples of high aspect ratio trenches and dual damascene structures are presented involving processes with single and double hardmasks.
Epitaxial Growth of NiSi2 on (111)Si Inside 0.1-0.6 μM in Size Oxide Openings Prepared by Electron Beam Lithography
Authors: Yew J. Y. , Chen L. J. , Nakamura K.
Published: April 2011

Epitaxial growth of NiSi2 on (111)Si inside 0.1-0.6 4m in size oxide openings prepared by electron beam lithography has been studied by field emission scanning electron microscopy, transmission electron microscopy and thin film stress measurement. Striking effects of size and shape of deep submicron oxide openings on the growth of NiSi2 epitaxy were observed. Epitaxial growth of NiSi2 of single orientation on (111)Si was found to occur at a temperature as low as 400 °C inside both contact holes and linear openings of 0.3. μm or smaller in size. Contact holes were found to be more effective in inducing the epitaxial growth of NiSi2 of single orientation than that of linear openings of the same size. The effects of size and shape of lateral confinement on the epitaxial growth of NiSi2 on (111)Si are correlated with the stress level inside oxide openings.
Effect of Ni-Si Disordered Layer on the Electronic Properties of Ni Silicide Barrier Contacts on Silicon
Authors: Rastogi A. C. , John P. K.
Published: April 2011

Changes in current transport and barrier heights of Ni-Si contacts as it undergoes atomic rearrangement and redistribution of charges under transient light annealing is studied with time resolution of 0.6 msec. Formation of an intermixed Ni-Si disordered layer by Ni-diffusion is shown by Auger data. Intrinsic barrier height of 0.7 eV increases to 0.82 eV as the spatial extent, disorder and density of Ni atoms which introduce new localized ststes at Ev+0.7 eV increases. Electronic properties of silicide contacts are affected by local interfacial bonds than by the characteristic of later grown silicide.
Sims and Moke Studies of Fe/Gd Multilayers on Si
Authors: Hsu Li-Shing , Lo C.-K. , Yao Y.-D. , Yang C.-S.
Published: April 2011

Two Fe/Gd/Fe/Gd multilayers with different layer thicknesses were grown on Si (100) by magnetron sputtering. The as-deposited samples were vacuum-annealed at 100°C, 200°C, and 300°C. They were studied by grazing incidence x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), vibrating sample magnetometer (VSM) and magneto-optical Kerr effect (MOKE). The deposition rates for Fe and for Gd are (1-2) and 4 Å s−1, respectively. The XRD and SIMS data show that interdiffusion occurs between Fe and Gd layers, and between Gd and Si layers. The thicker multilayers show strong in-plane uniaxial anisotropy.
Magnetic Properties of Uniform Nanowire arrays
Authors: Nguyen P. P. , Tonucci R. J.
Published: April 2011

Fabrication and magnetic measurements of ferromagnetic (Ni and Co) nanowire arrays using nanochannel glass templates are presented. These nanowire arrays have novel characteristics: The nanowires are very parallel (to within a fraction of a degree) and regularly placed. They are circular with extremely uniform diameter (of less than 80 nm for some samples) both along individual wire's length and among different wires within an array. Magnetic measurements show enhanced coercivities compared to the bulk values. The saturation magnetization for Ni nanowires depends much more strongly on temperature than that for Co nanowires. The coercivities are also dependent strongly on temperature and can be explained by a thermal-activation model.
Tailoring the Pore Size of Hypercrosslinked Polymer Foams
Authors: Steckle W. P. , Mitchell M. A. , Apen P. G.
Published: April 2011

Organic analogues to inorganic zeolites would be a significant step forward in engineered porous materials and would provide advantages in range, selectivity, tailorability and processing. Rigid molecular foams or “organic zeolites” would not be crystalline materials and could be tailored over a broader range of pore sizes and volumes. A novel process for preparing hypercrosslinked polymeric foams has been developed via a Friedel-Crafts polycondensation reaction. A series of rigid hypercrosslinked foams have been prepared using simple rigid polyaromatic hydrocarbons including benzene, biphenyl, m-terphenyl, diphenylmethane, and polystyrene, with p-dichloroxylene (DCX) or divinylbenzene (DVB) as the crosslinking agent. Transparent gels are formed suggesting a very small pore size. After drying the foams are robust and rigid. Densities of the resulting foams can range from 0.15g/cc to 0.75g/cc. Nitrogen adsorption studies have shown that by judiciously selecting monomers and crosslinking agent along with the level of crosslinking and the cure time of the resulting gel, the pore size, pore size distribution, and the total surface area of the foam can be tailored. Surface areas range from 160 to 1,200 m2/g with pore sizes ranging from 6Å to 2,000Å. Further evidence of the uniformity of the foams and their pore sizes has been confirmed by high resolution TEM.
The Synthesis and Characterisation of Ordered Mesoporous Materials Incorporating Organo-Siloxanes
Authors: Sims Stephen D. , Burkett Sandra L. , Mann Stephen
Published: April 2011

Organically-functionalized mesoporous silicas have been prepared at room temperature, in a base-catalysed reaction, by the co-condensation of tetraethoxysilane and organosiloxanes ((C2H5O)3Si-R; R = C6H5 or n-C8H17) in the presence of surfactant (C16H33N(CH3)3Br) templates. The resulting materials are covalently linked, hexagonally ordered, hybrid inorganicorganic networks.
Mixed Carbon-Aluminum Oxide Coatings from Aqueous Sols and Solutions
Authors: Boakye E. , Hay R.S. , Petry M. D.
Published: April 2011

3M Nextel 720 fiber tows were continuously coated with carbon-alumina mixtures. Water soluble hydrocarbons such as sucrose and ammonium polymethacrylate (Darvan C) were used as carbon sources. Bridging of coating between filaments was reduced by displacing excess sol in the fiber tow with 1 -octanol. The effect of carbon-alumina association (sucrose or polyelectrolyte and alumina interaction) on the homogeneity of the alumina/oxide coatings are presented and discussed.
C-Axis Oriented Thin Films of PbZrO3 on Silicon Substrate by Pulsed Laser Ablation
Authors: Chattopadhyay S. , Palkar V. R. , Ayyub P. , Purandare S. C. , Pam S. P. , Apte P. R. , Pinto R. , Multani M. S.
Published: April 2011

We report the successful deposition of single phase c-axis oriented films of lead zirconate (PbZrO3) on a silicon substrate by pulsed laser ablation. The formation of the film at different substrate temperatures was studied using atomic force microscopy and scanning electron microscopy. We also measured the temperature dependence of the dielectric constant of the films and their dielectric hysteresis behavior.
Low Temperature Growth of PZT(52/48) Thin Films using Rf Magnetron Sputtering Method
Authors: Kim Tae Song , Kim Dong Joo , Lee Jeon Kook , Jung Hyung Jin
Published: April 2011

Comparatively low temperature growth of Pb(Zr0.52Ti0.48)O3 thin films was accomplished by using rf magnetron sputtering process. Well crystallized PZT thin films (4000Å thickness) were synthesized on Pt/Ti/SiO2/Si(100) substrate at the temperature as low as 5200°C. The polycrystalline PZT perovskite phase formation was confirmed with XRD analysis. Remanent polarization(Pr) and coercive field(Ec) of as-grown film (4000Å) were 8–30 μC/cm2 and 24–64 kV/cm with the applied voltage variation(5–17 V). The post annealing enhances the electrical properties even at 500°C, which is below the as-grown temperature(520°C). The increase of annealing temperature resulted in the consequent increase of remanent polarization and the decrease of coercive field. The values of dielectric constant(ε′ ) and tan δ measured with small signal sign wave(1V, 10kHz) were 1207 and 0.066 in case of as-grown film (4000Å).