bluuebunny/crossref_metadata_2025 huggingface dataset:
Flux Line Dynamics with Electron Holography
Authors: Tonomura Akira
Published: April 2011

Flux lines in superconducting thin films are observed statically in a holographic electron interference micrograph, and dynamically in a Lorentz micrograph with a “coherent” and 300kV electron beam. In interference microscopy, projected magnetic lines of force in a tilted Nb thin film are observed quantitatively as contour fringes drawn on an in-focus electron micrograph. Whereas in Lorentz microscopy, flux lines are observed as spots with bright and dark contrast pairs due to defocusing of the image. Although the image is blurred due to a large amount of defocusing, this method is suitable for real-time observation. By making the best use of this feature, flux line movement can be observed when the applied magnetic field or the film temperature changes.
Calculation of Stresses in Strained Semiconductor Layers
Authors: Nakajima K.
Published: April 2011

A stress calculation method is proposed by improving the force and moment balance method to calculate the stress in semiconductor layers. The following three points are improved. The first point is that the vertically precise stress distribution in multilayers can be calculated by using imaginary thin layers. The second point is that the stress can be calculated on the basis of threedimensional deformation. The third point is that the stress can be calculated in strained layers with interfacial misfit dislocations. The stress distribution in strained semiconductor layers such as InGaAs/GaAs multilayers, InGaAs/graded lnGaAs/GaAs layers and GaAs/Si structures is calculated using this improved method.
X-Ray Spectrometer with a Submicron X-Ray Beam for Ulsi Microanalysis
Authors: Yamamoto Naoki , Homma Yoshio , Sakata Shinji , Hosokawa Yoshinori
Published: April 2011

A fluorescent and diffraction X-ray spectrometer with a 0.8 μmϕ Xray beam has been developed. It allows simultaneous measurement of local strains and minute amounts of metal contaminants in fine ULSI devices. The minimum sample size for X-ray diffraction measurement with it is a 0.3 μm diameter by 0.2 μm deep volume. It is applied to analyze strain in Al lines, showing that strain in Al single-layer lines (no barrier) increases significantly as the line width is reduced below 1.5 μm. Introducing barrier metals reduces this dependence of strain on line width. It is also found that hillock and void formation has a very strong correlation to strain.
Measurement and Interpretation of Strain Relaxation in Passivated Al-0.5%Cu Lines
Authors: Besser Paul R. , Marieb Thomas N. , Bravman John C. , Flinnt Paul A.
Published: April 2011

X-ray diffraction was used to measure the strain relaxation in passivated Al-0.5%Cu lines at 200°C after cooling directly from an anneal at the passivation deposition temperature. The strain decay is fit with a stress-assisted, thermally-activated relaxation model. A high-voltage scanning electron microscope was used to image the presence and growth of voids through the passivation. The time scale of the void growth is not the same as that of the hydrostatic relaxation, indicating that voiding is not solely responsible for the observed relaxation. The relaxation of the line is modeled using a von Mises yield criterion and allowing elastic compliance of the passivation. The magnitude of the calculated relaxation agrees with the measurements. It is suggested that a combination of voiding and passivation compliance is responsible for the measured hydrostatic strain relaxation.
Electromigration Lifetimes of Single Crystal Aluminum Lines with Different Crystallographic Orientations
Authors: Joo Y.-C. , Thompson C.V.
Published: April 2011

Near-bamboo interconnects are susceptible to failure either at polygranular clusters or within bamboo grains (transgranular failure). Polygranular failure mechanisms are often dominant in lines with near-bamboo structures at test conditions, but at service conditions, transgranular failure mechanisms are expected to dominate. In order to study the temperature and current density dependence as well as the crystallographic dependence of these transgranular failure mechanisms, it is necessary to isolate them from other mechanisms. To do this, we have studied single crystal Al lines on oxidized silicon.

We have tested lifetimes of passivated and unpassivated Al single crystal lines with various textures. In both passivated and unpassivated lines, the median time to failure, t50, was found to be texture-dependent, with t50(l11) > t50(133) > t50(110), and with t50(111) ∼ 10×t50(110). The activation energy for failure for both passivated and unpassivated (110) single crystal lines was about 1 eV. This value differs from that of aluminum bulk diffusion (1.4 eV), suggesting that interface diffusion is the dominant diffusion mechanism in these lines, and perhaps in bamboo regions of near-bamboo lines as well.
Stress Distribution and Mass Transport Along Grain Boundaries During Steady-State Electromigration
Authors: Scherge M. , Bauer C. L. , Mullins W. W.
Published: April 2011

Stress distribution and mass flux in the plane of each grain boundary within a polycrystalline thin-film conductor have been calculated during electromigration for zero flux divergence (steady state) and various boundary conditions. Steady state, representing a balance between the (applied) electric and (induced) stress driving forces, is assumed to develop after a short transient time. Boundary conditions at the intersection of grain boundaries with the top and bottom conductor surfaces (surface junctions) and with the conductor edges (edge junctions) are assumed to be of two types: open (flux passes freely) and closed (zero flux). Flux is assumed to pass freely at the intersection of grain boundaries with each other (triple Junctions). Several grain boundary configurations are considered, including individual boundaries, single triple junctions, and combinations thereof, assuming that bottom surface junctions (conductor/ substrate interface) are closed and that top surface junctions are either open (bare conductor) or closed (passivation layer). Results clearly show the formation of incipient holes and hillocks near the intersection of triple junctions and/or closed (blocked) edge junctions with open surface junctions.
Early Electromigration Failure in Submicron width, Multilayer Al Alloy Conductors: Sensitivity to Stripe Length
Authors: Oates A. S.
Published: April 2011

The microstructure of Al alloy integrated circuit conductors strongly affects electromigration failure of the metallization. For submicron linewidths, the microstructure is usually near - bamboo, consisting of alternate polycrystalline and bamboo segments. These polycrystalline segments appear to be much more susceptible to electromigration - induced voiding than the bamboo regions. As a result, microstructural related early failures are a significant concern. In this study we systematically vary line - length to investigate the impact of random microstructural variations on the failure distribution parameters of narrow, multilayer (Ti/TiN/Al/TiN) Al alloy conductors. We show that early failures can occur in 0.6 μm wide stripes. The impact of early void formation on conductor failure, however, is dependent on the resistance failure criterion. By increasing the value, early failures may be eliminated in long line - lengths, suggesting that the resistance failure criterion may provide a means to control the impact of early voiding on the electromigration failure.
Large Area Pulsed Laser Deposition of YBCO Thin Films and Buffer Layers on 3-Inch Wafers
Authors: Lorenz M. , Hochmuth H. , Börner H. , Natusch D. , Kreher K.
Published: April 2011

An arrangement for large area PLD on 3-inch wafers is proposed. In order to get a homogeneous stoichiometry and thickness distribution and small variations of superconducting properties on the 3-inch diameter, the substrate is foreseen to be rotated and additionally laterally moved up to 45 mm during deposition whereas the laser plume remains fixed.

YSZ buffer layers showed thickness homogeneity of 1% within 10 mm, of 4% within 2 inch and of 8% within 3 inch diameter, respectively. For in-situ deposited YBCO thin films on r-plane sapphire with YSZ buffer layer we inductively measured within 3 inch diameter values of the critical temperature Tc(90%) from 85.9 K to 86.7 K and values of the critical current density jc(77 K) from 1 × 106 to 2 × 106 A/cm2. However, up to now the degree of epitaxy of the YBCO thin films on r-plane sapphire with YSZ buffer layer is lower compared to YBCO on MgO(100) as determined by Raman spectroscopy. Nevertheless, large area PLD seems to be a very promising technique for homogeneous coating of 3-inch wafers by epitaxial oxide thin films.
Cluster Models for Point Defect Structure in La2CuO4+δ
Authors: Wu Yue , Ellis D. E. , Mason T. O.
Published: April 2011

We report theoretical studies on oxygen excess defect structure of lanthanum cuprate, La2CuO4+δ, using the Local Density formalism. The self-consistent Discrete Variational method has been used to find energy levels, densities of states, charge transfer, wavefunctions and potentials for a fragment consisting of N atoms embedded in the infinite crystal. Various possible interstitial oxygen positions and relative stability have been studied, including the structure suggested by Chaillout, et al. on the basis of neutron diffraction. Calculated electronic structures have been used to predict defect-related spectroscopic consequences.
Applications of Nonlinear Optical Thin Films
Authors: Brueck S. R. J. , Myers R. A.
Published: April 2011

Many approaches to fabrication of nonlinear optical and electro-optical thin-film materials are currently under investigation including: epitaxial inorganic films; polycrystalline inorganic materials; organic nonlinear moieties poled in polymer hosts; and poled amorphous inorganic materials. For each of these approaches there are a variety of characteristics and constraints that impact the ultimate uses. These are discussed in the context of signal processing and transmission applications such as optical interconnects and integrated optics. Almost universally, integration with the Si materials and processing that dominates current computer technology, or with the III-V materials that dominate optoelectronics technology, are major factors in the attractiveness of a technology direction. A relatively recent development is the observation of a strong nonlinearity in fused silica, χ(2) ∼ 1 pm/V, poled by modest temperature and electric-field stress. Temperature-dependent dynamic and spectroscopic measurements suggest that mobile-ion species such as Na+, as well as non-bridging oxygen bond re-orientation under a strong field, play a role in the nonlinearity.
Raman Spectroscopy of Barium Titanate Thin Films
Authors: Robins Lawrence H. , Kaiser Debra L. , Rotter Lawrence D. , Stauf Gregory T.
Published: April 2011

Raman spectroscopy was used to examine the structure of polycrystalline and epitaxial barium titanium oxide thin films grown by metal-organic chemical vapor deposition. The Raman spectra confirmed the presence of the tetragonal ferroelectric phase of BaTiO3 and also revealed several other Ba-Ti-O phases. These films were also characterized by X-ray diffraction and TEM imaging. The structural information provided by the Raman spectra was qualitatively consistent with the X-ray and TEM results. The temperature dependencies of the Raman spectra of two films were examined in the range 25°C-175°C. Raman peaks due to tetragonal BaTiO3 were observed at temperatures well above 132°C, which is the tetragonal-cubic phase transition temperature for bulk single-crystal BaTiO3. This may indicate stabilization of the tetragonal phase by an anisotropic film-substrate interaction or by inter-grain stresses.
Incorporation of Iron Cations Into Epitaxial Sapphire Thin Films by CO-Evaporation and Subsequent Thermal Annealing
Authors: Yu Ning , Kung Harriet , Nastasi Michael , Li DeQuan
Published: April 2011

Iron-doped sapphire thin films have been successfully epitaxially grown onto sapphire single crystal substrates by electron beam deposition and subsequent thermal annealing. Amorphous A12O3 thin films, about 280–390 nm thick, cation doped with iron have been deposited on [0001] oriented sapphire substrates. Iron doping with cation concentrations (a ratio of Fe content to total cation content) up to 5 at.% can be incorporated into the octahedral sites of Al-cation sublattice during the epitaxial regrowth process at 1000–1400 C, as determined by Rutherford Backscattering Spectrometry and ion channeling measurements. Cross-sectional Transmission Electron Microscopy shows the presence of two distinct regions in the annealed films. One exhibits the epitaxial relationship with the sapphire substrate and the second region has amorphous type of contrast. External optical transmittance measurements in the ultra violet and visible light range have exhibited the absorption associated with Fe3+. This study has demonstrated a simple method of incorporating dopants into single crystal sapphire, which has potential in the fabrications of thin film planar optical waveguiles.
In-Situ Thin Film Growth of PbTiO3 By Multi Target Sputtering
Authors: Maeder Thomas , Muralt Paul
Published: April 2011

The in-situ reactive sputter deposition of PbTiO3 on Pt/Ti/SiO2/Si from two metallic targets was investigated. A minimal lead oxide flux of two to three times the titanium oxide flux is needed in order to obtain stoichiometric films with the perovskite structure. For higher fluxes, the Pb/Ti ratio in the film stays at the stoichiometric value 1; the orientation changes from random to <100>; and the film morphology transforms from a rough to a smooth polycrystalline film. The obtained dielectric constants vary between 40 and 150, the losses between 2 and 4 % (10 kHz). The method could be extended to PbZrxTi1-xO3 for x ≤0.7. The orientation is lost when the Pt electrodes are replaced by RuO2 electrodes.
Catalytic Combustion for Ultra-Low Emissions
Authors: Farrauto Robert J. , Larkin Matthew , Fu James , Feeley Jennifer
Published: April 2011

Catalytic combustion is an emerging technology in which fuels can be combusted homogeneously supported by a catalyst. The catalyst allows non-flammable mixtures of fuel and air to be oxidized with the resulting heat generated used to initiate thermal or homogeneous combustion. With the proper catalysts the fuel can be combusted with efficiencies so high that unburned CO or HC emissions are less than 10 ppm. Furthermore, because the fuel-air mixtures are relatively lean compared to conventional processes the adiabatic temperatures are below that required for the formation of NOx i.e. > 1500°C. The success of this technology would eliminate the need for expensive after-treatment of emissions from gas fired power plants and boilers.

This is a very demanding application, especially for natural gas fueled combustors, since the catalyst will have to initiate reaction between 400 and 500°C, at linear velocities exceeding 50 ft/sec, and retain its activity after experiencing temperatures up to 1400°C. Furthermore, the monolithic ceramic or metallic support upon which the catalyst is deposited must also retain structural integrity after experiencing high temperatures and severe thermal shock.

This paper will describe the fundamental concepts of this new technology, the major technical problems being addressed and the progress being made.
Environmentally Conscious Materials and Manufacturing Processes
Authors: Narayan C. , Fenton J. , Datta M.
Published: April 2011

Environmental and safety issues are becoming increasingly critical for the selection of materials and their processing techniques. While the choice of “green” materials is important from the perspective of disposal of spent or used products, the choice of environmentally sound processes is important to cut down manufacturing waste and limit the use of toxic solvents and solids. Some examples from the electronics and the aerospace industry are described.
Catalytic Decomposition of N2OON ZrO2and Co/Ni/ZrO2Systems
Authors: Zeng H. C. , Lin J. , Teo W. K. , Wu J. , Tan K. L.
Published: April 2011

Monoclinic ZrO2and its supported catalysts Co/Ni/ZrO2for catalytic decomposition of N2O have been studied with FTIR, EDAX, XPS, and the evaluation of activity of the catalysts. It is found that monoclinic ZrO2alone has the catalytic effect for N2O decomposition although the gas decomposes on Co/Ni/ZrO2more efficiently. The XPS study shows that only Co exists in the surface region of ZrO2. In evaluation experiments, it is found that when Co/Ni exceeds a threshold concentration, the conversion of N2O is no longer accelerated with the increase of Co/Ni content. The gas decomposition on Co/Ni/ZrO2can be described as first order with respect to partial pressure of N2O. No nitrogen N(ls) photoelectrons were detected for the catalysts after N2O decomposition. Surface reactions on ZrO2and Co/Ni/ZrO2, including the behaviour of retained carbon (Cls) and N2O decomposition mechanism, will also be addressed.
Biosurfactant Production Using Mixed Cultures Under Non-Aseptic Conditions
Authors: Vipulanandan C. , Ghurye G. L. , Willson R. C.
Published: April 2011

Surfactants increase the accessibility of adsorbed hydrocarbons and mobilize immiscible petroleum hydrocarbons for treatment. Biosurfactants have the advantage of biodegradability and non-toxicity over their synthetic counterparts, and can be produced from renewable sources. In this study the production of biosurfactant from molasses was investigated in continuously stirred batch reactors. The effects of substrate concentration, yeast extract and peptone on biomass accumulation and biosurfactant production were investigated. Biosurfactant production was quantified by surface tension reduction and critical micelle dilution (CMD). Biosurfactant production was directly correlated with biomass production, and was improved with the addition of yeast extract. Centrifugation of the whole broth reduced surface tension. The performance of the biosurfactant produced from molasses under non-aseptic condition is comparable to other published results.
Laser Cleaning - A New Surface Cleaning Method Without Pollutions
Authors: Lu Y. F. , Aoyagi Y.
Published: April 2011

Surface contaminations are removed by laser irradiation with pulse output and short wavelength from various substrate such as magnetic head slide, glass and metals. Laser cleaning is a new dry process to remove surface organic contaminations without using ultrasonic cleaning in organic solvents. This provides a new dry process to clean different substrate surfaces and can take the place of conventional wet cleaning processes such as ultrasonic cleaning with CFC and other organic solvents. The mechanisms of laser cleaning may include laser photodecomposition, laser ablation and surface vibration due to the impact of laser pulse. It is found that short wavelength and short pulse duration are necessary for effective cleaning. It is also found that an appropriate energy density is critical to achieve effective cleaning without causing surface oxidation and secondary contamination.
Solid Freebody Forming of Ceramics from Polymerizable
Slurry
Authors: Stuffle Kevin , Mulligan Anthony , Lombardi John , Calvert Paul , Fabes Brian
Published: April 2011

A system is described for forming three-dimensional parts from a
polymerizable slurry. This liquid is delivered from a fine nozzle to build
up the component as a series of layers described from a CAD drawing of the
part. This is one of a family of solid freebody forming methods. The
layerwise process lends itself particularly to chemically syntheized
materials where shrinkage and mass transport are major problems. The
technique also has considerable potential for combining various materials
into a single component.
Cycloaliphatic Epoxide Based Sol-Gel Derived
Materials
Authors: Sigel G. A. , Domszy R.C. , Welch W. C.
Published: April 2011

Scratch resistant transparent organically modified sol-gel materials
typically utilize organics as acrylates, or pre-polymer silicon or carbon
backbone material. The use of diepoxide monomers within a sol-gel matrix has
yet to be described as a means of obtaining high performance coating
materials. This paper describes the preparation and characterization of UV
curable inorganic-organic hybrid glass materials based on the incorporation
of cycloaliphatic diepoxide monomers into a sol-gel composition of TEOS and
the epoxide silane coupling agent glycidoxypropyl-trimethoxysilane. We
report aging and humidity studies along with processing conditions that
affect the silicate distribution and cationic cure of the diepoxide resin
based on solution and solid state NMR experiments. Mechanical analysis of
thin films prepared by varying processing conditions and length of the
diepoxide backbone are also discussed.
Modification of Sol-Gel Thin Films By Ion
Implantation
Authors: Hirashima Hiroshi , Adachi Kenji , Imai Hiroaki
Published: April 2011

In order to densify and to improve the physical properties, TiO2
sol-gel films, about 100 nm in thickness, on silica glass or silicon wafer
were implanted with Ar+ or B+ ions. The refractive
index of the as-dried films increased and the IR absorption band of OH
disappeared after Ar+ implantation. Drying and densification of
sol-gel films were enhanced by Ar+ implantation. On the other
hand, the refractive index and the thickness of the films hardly changed
with B+ implantation. However, IR absorption bands of B-O bond
were observed after B+ implantation. This suggests that sol-gel
films could be chemically modified by ion implantation with reactive ion
species.
Hollow Mullite Ceramic Microspheres by Water Extraction of
Emulsified Aqueous Droplets
Authors: Liu Guoxu , Wilcox David L.
Published: April 2011

This paper describes a novel colloidal route for the preparation of hollow
mullite ceramic microspheres with sizes in the range of 10 μm. An emulsion
technique was combined with a water extraction sol-gel process, to form an
aqueous droplet dispersion and gel the resulting droplets by extracting
water with a dehydrating liquid. The liquid-filled gelled microcapsules were
then dried and fired to form hollow ceramic microspheres. Important
processing variables controlling the microspherc morphology were determined
and a formation mechanism was proposed. Due to its potential applications in
microelectronic packaging, mullite was selected as the model material for
the present work, but the synthesis technique may be used for making other
single or multiphase ceramic compositions
Preparation of Transition Metal Oxides By A Nonhydrolytic
Sol-Gel Process
Authors: Arnal Pascal , Corriu Robert J.P. , Leclercq Dominique , Mutin P. Hubert , Vioux Andre
Published: April 2011

Etherolysis of metal chlorides offers a versatile, simple nonhydrolytic
sol-gel route to transition metal oxides. The main limitation of the process
results from the insolubility of some metal chlorides in non aqueous
solvents. The general tendency of this nonhydrolytic process is to delay
crystallization of metal oxides.
The Metal - Oxide Composite
[Fe0.2Co0.8]0.8[Fe2.38Co0.62O4]:
Hrtem and EDX Characterization
Authors: Noubeyo J. C Yamegni , Riera A. Malats I , Werckmann J. , Pourroy G. , Ehret G. , Poix P.
Published: April 2011

The new metal-ferrite composite
[Fe0.2Co0.8]0.8[Fe2.38Co0.62O4]
is obtained by precipitation of ferrous and cobalt chloride in KOH. Further
heating under vacuum above 400°C shows a cationic exchange between metal and
spinel leading to a new composite made up of cobalt metal and cobalt doped
magnetite.

HTERM and EDX observations have been carried out on both composites, i.e.,
before and after vacuum annealing, We show that cationic exchange occurs
mainly in crystals made up of spinel, CoO and amorphous nanoparticles.
Chemically Bonded Ceramics as an Alternative to High Temperature
Composite Processing
Authors: Gulgun Mehmet A. , Johnson Bradley R. , Kriven Waltraud M.
Published: April 2011

Processing of multi-phase ceramic composite materials using chemically
bonded ceramics as a binding agent appears to be a promising route for
fabricating complex-shaped structures. In a zirconia-calcium aluminate
ceramic matrix composite, the hydraulic property of fine, monocalcium
aluminate (CaAl2O4) powders was used to prepare strong
prefired bodies.

The changes in the physical characteristics of the composite during the
conversion from a chemically bonded compact into a sintered composite were
studied using thermogravimetric analyses (TGA), X-ray diffraction and
scanning electron microscopy. The density and the hardness of the chemically
bonded and sintered composite were measured.
The Use of Superlattice Reactants in The Synthesis of Ternary
CU‐NB‐SE Compounds
Authors: Hornbostel Marc D. , Fukuto Masafumi , Johnson David C.
Published: April 2011

The low temperature interdiffusion of superlattice reactants of the binary
systems niobium‐selenium and copper‐selenium and the ternary
copper‐niobium‐selenium were explored to synthesize amorphous reaction
intermediates. Controlled crystallization of this intermediate, which
depends upon nucleation energetics rather than the thermodynamic stability
of the final product, was used as we attempted to prepare ternary niobium
cluster compounds. We present data demonstrating the ability to prepare
amorphous ternary intermediates without the formation of crystalline binary
compounds as reaction intermediates. Crystallization of the amorphous
intermediate resulted in the formation of known ternary compounds directly,
also without the formation of binary compounds.
Preparation And Characterization Of Ultra-Small Sized Metal And
Semiconductor Particles In Sol-Gel Materials
Authors: Choi Kyung Moon , Shea Kenneth J.
Published: April 2011

Poly(l,4-phenylene)-bridged and poly(1,6-hexylene)-bridged silsesquioxanes
(PPS and HPS) were prepared by the sol-gel process. The surface areas and
pore diameters of these porous xerogels were obtained by BET and BJH
methods, respectively. These porous materials were used as a confinement
matrix for the growth of small-sized semiconductor and transition metal
clusters. Quantum-sized CdS particles in PPS (approximately 58+12 Â) and HPS
(91+16 Â) matrices were prepared by first soaking the xerogel in a
CdCl2 solution. Following a washing with water, a Na2S
solution was then added. EDAX and electron diffraction techniques were used
to identify the CdS particles. The particle sizes of CdS in PPS and HPS were
determined by both UV measurements and from TEM images. Small-sized Cr
clusters were prepared in dried xerogels by an internal doping method. Mixed
Cr/CdS phases were also prepared by internal loading of a chromium metal
precursor. Following deposition of CdS the xerogel was heated at 120 °C
under high vacuum, resulting in formation of intimately mixed phases of Cr
metal and CdS. Changes in morphology, in particular the surface area and
pore size distribution were noted. A decrease in surface area and an
increase in pore size were observed as a result of Cr metal deposition.
Micrqporous Silica Gels from Alkylsilicate-Water Two Phase
Hydrolysis
Authors: Chu L. , Tejedor-Tejedor M. I. , Anderson M. A.
Published: April 2011

Microporous silica gels have been synthesized through a nano-particulate
sol-gel route. These gels have uniformly distributed and extremely small
pores(< 15Â in diameter). Hydrolysis and condensation reactions leading
to these gels were carried out in an alkyl silicate-water (ammonia) two
phase system. These reactions took place at the alkyl silicate droplet-water
interfacial boundary. No alcohol was added. A clear, stable and uniformly
distributed colloidal silica suspension having an average particle size less
than 6 nm was prepared by this method. Fast hydrolysis, slow condensation
and low solubility all contribute to a high supersaturation level and result
in the formation of small particles. This process is consistent with classic
nucleation theory. When the particles are produced under acidic rather than
under basic reaction conditions, smaller particles are formed due to the
slower condensation rate and lower solubility of these silica particles in
acidic conditions. At the same pH, alkylsilicates having smaller alkyl
groups react faster with water leading to smaller primary particles.
Homogeneous nucleation conditions are achieved when the water/alkylsilicate
ratio is high.
Dynamics of Liquids in Confined Geometries
Authors: Xu Shu , Korb J.-P. , Jonas J.
Published: April 2011

An overview of several NMR studies of liquids in confined geometries is
presented. First, the NMR relaxation rates, 1/T1,
1/T1ρ , and 1/T2 were measured for several
molecular liquids confined to porous silica glasses with pore radii in the
range from 12 Å to 100 Å as a function of temperature, pore size, and
frequency. The experimental relaxation data were interpreted in terms of
bulk, surface, and topological contributions using the following
expression:

where 1/Tib and 1/Tis are the bulk and the surface
layer relaxation rates, ε is the thickness of the surface layer, R is the
pore radius, and Ai(ω) represents the pure topological
effect.

Second, the pressure effects on the dynamics of the confined liquid of
acetonitrile-d3 were also investigated. Third, the natural
abundance of 13C spin lattice relaxation rates for CS2
confined to porous silica glasses provided information about confinement
effects on the angular momentum behavior of this simple liquid.
Fullerenes Entrapped in Porous Glass
Authors: Borrelli N.F. , Smith C. , Smith D.W.
Published: April 2011

Fullerenes have been impregnated in porous glass with little interaction with the glass noted. Concentrations as high as 3mg/ml of C60 or C70 were obtained. It was shown that the fullerenes can enhance the photo-induced charge transfer reaction of DEA with the porous glass.
Studies of C60 Films Deposited Using Ionized Cluster Beam Deposition Technique
Authors: Ren Zhong-Min , Du Yuan-Cheng , Ying Zhi-Feng , Xiong Xia-Xing , He Mao-Qi , Li Yu-Fen , Li Fu-Ming
Published: April 2011

Films (with thicknesses about thousands A) of a new form of carbon allotrope, CIO also known as Fullerenes, are deposited on Si(111) substrates using ionized cluster beam deposition (ICBD) technique at low (65V) accelerating voltage V. X-ray &-20 diffraction (XRD) have been used to investigate the structural properties of C6Ofi lms, indicating hexagonal close-packed structure with strong (002) XRD assignment together with weak (100), (112) and(004) assignments. Raman spectra, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) are carried out to make detailed studies of the electronic properties of the films and to illustrate differences between CO films and amorphous carbon films which are deposited by ICBD at high accelerating voltage V >400V. Cio soccer-balls are found to be broken into fragments as accelerating field overtakes about 400V, indicated by the results of XPS, Raman spectra, XRD, and UV/visible absorption spectra.
Electronics Application for Fullerenes
Authors: McNally R.L. , Brotzen F R. , Griffin A.J. , Loos P.J. , Barrera E.V.
Published: April 2011

Thin-film Al-C60-Al trilayered structures were sublimated under ultra high vacuum (UHV) conditions for the purpose of investigating their current-voltage (I-V) properties. These metal-semiconductor-metal devices exhibited rapid and irreversible drop in resistance of about two orders of magnitude under an applied voltage of 0.67 to 0.75V. Approximate initial and final resistances were 1050 Ω and 8 Ω respectively. Wavelength Dispersive Spectroscopy (WDS) indicated no noticeable change in phase of the fullerene inter-layer after the irreversible drop in resistance. These results, SEM micrographs and concentration profiles were concordant with diffusion of top layer Al through the fullerene layer as the most likely cause of the change in resistance.
The Effects of Molecular Orientation on the Electronic Structure of the Solid Fullerites
Authors: Gu Bing-Lin , Maruyama Yutaka , Yu Jing-Zhi , Ohno Kaoru , Kawazoe Yoshiyuki
Published: April 2011

The effects of C60 molecular orientation and rotation on the electronic structure of fcc C60 solid have been investigated by performing a band structure calculation with self-consistent mixed-basis all electron and full-potential approach within local density approximation. We present an angle-dependent density of states of HOMO and LUMO bands, which should be compared to the angle-resolved photoemission data.
Highly Sensitive Analysis for Valence Band Edge of C60 Films by Total Yield Photoelectron Spectroscopy
Authors: Gonda S. , Kawasaki M. , Arakane T. , Koinuma H.
Published: April 2011

We have in-situ measured the density of states (DOS) around the top of valence band of pristine C60 films by means of total yield photoelectron spectroscopy. The top of valence band (TVB) of C60 was located at 5.00eV below the vacuum level. Considerable amplitude of gap states was observed up to 0.9eV above the TVB. Kelvin probe method revealed that the Fermi level of amorphous C60 film was located at 0.47eV above the TVB. The improvement of crystallinity in C60 films, which induced the increase in electrical conductivity as well, increased the DOS above the TVB. The electric conduction of C60 films cannot be explained with a simple picture for carrier conduction in semiconductors.
Synthesis of Carbo-Nitride Films Using High-Energy Shock Plasma Deposition
Authors: Gurarie V. N. , Orlov A. V. , Nugent K. W. , Weiser P. , Prawer S.
Published: April 2011

The present work reports on the properties of nitrogen rich carbon films produced by an intense gas discharge between carbon electrodes in a nitrogen atmosphere. The energy of the discharge, initial nitrogen pressure, number of discharges and geometry are varied to establish their effect on the nitrogen content and the mechanical, structural and morphological characteristics of the deposited carbon-nitride films. The structural diagnostics include optical and scanning electron microscopy, as well as Auger and Raman Spectroscopes and Rutherford Backscattering. The C-N films formed fell into two categories, differing in morphology and mechanical properties. Type I are C-N films, containing up to 35 at. % nitrogen, and which have an amorphous structure. These films are formed at relatively low plasma shock pressure and exhibit relatively low microhardness, ̴ 2 GPa. In a relatively narrow range of the plasma shock pressure and temperature the second type of C-N deposition is observed consisting of high density, closely-packed crystal-like grains growing perpendicular to the substrate surface and displaying a cauliflower-like morphology, The microhardness of these films reaches 15 GPa, as measured by the Vickers method.
On The Role of Penetration Twins in The Morphological Development of Vapor-Grown Diamond Films
Authors: Tamor Michael A. , Everson Mark P.
Published: April 2011

By control of deposition conditions, the morphologies of vapor-deposited polycrystalline diamond films may be varied deliberately from clean multi-micron crystallites to nanocrystalline ‘cauliflower’ nodules. Most attempts to connect diamond film ‘quality’ to growth conditions focus on competitive growth of non-diamond phases. In contrast, we propose that twinning is potentially the dominant factor. We develop a geometric parameterization of growth conditions to define conditions under which a common type of twin - the < 111> penetration twin - can outgrow and potentially bury the parent face on which it originated. We then show how the full range of CVD diamond crystal and film morphologies might be explained entirely in terms of penetration twins. This explanation does not entail reference to the actual mechanism of diamond growth. The geometric parameterization also suggests a ‘reactor map’ which serves as a powerful tool in process development and control.
Novel Structure of Microporous Activated Carbon Fibers and Their Gas Adsorption
Authors: Enoki Toshiaki , Kobayashi Norikazu , Nakayama Atsuko , Suzuki Kazuya , Ishii Chiaki , Kaneko Katsumi , Hosokoshi Yuko , Kinoshita Minoru , Endo Morinobu , Shindo Norifumi
Published: April 2011

Activated carbon fibers are a kind of microporous carbon. Using dangling bond spins attached to the peripheries of the micropores, we investigated the microporous structures in relation to the heat-treatment and gas adsorption effects. Functional groups weakly bonded to the graphitic backbone are removed by the heat-treatment at moderate temperatures 200-400°C, resulting in the generation of a variety of dangling bond spins. The heattreatment above 500°C brings about homogenization of the dangling bond spins. For gas adsorption, the introduction of helium gas strongly enhances the spin-lattice relaxation rate for the dangling bond spins. In addition to a remarkably large condensation of helium gas in the microporous region, the enhancement proves the presence of ultra-micropores which can accommodate only the smallest diameter helium atoms.
Intrinsic Stress in Sputtered Thin Films
Authors: Nguyen Tai D. , Nguyen Tue , Underwood James H.
Published: April 2011

Understanding of the stress in thin films is important in controls of the properties of nanometer period x-ray multilayers. Stress evolution at the initial stages of thin film formation was studied by molecular dynamics simulation of Mo atoms impinging on a 5×5×5 unit cell Mo substrate. The simulation shows that the structure initially increases in a compressive state. The stress then decreases when the deposited atoms have covered the substrate surface. Measured stress of Ru films in Ru/C multilayers by laser curvature technique shows similar behavior to the simulated results.
Underlayer Effects on the Growth Stress of Titanium Films
Authors: Poppeller M. , Abermann R.
Published: April 2011

The growth stress of titanium films was measured in situ with a cantilever beam technique under UHV conditions at Ts ≥ 130°C. The substrate used in these experiments was a double layer consisting of a base layer of A12O3 or of MgF2 and as a second layer a titanium film evaporated at different H2O-partiaI pressures (Ti/TiOx). With both base layers the growth stress of the substrate Ti/TiOx layer is similar.

The main objective of this paper was the investigation of the effect of a variation in the chemical composition of the substrate Ti/TiOx layer on the growth stress and -by way of our stress model - on the growth mode of a clean titanium film always evaporated under identical vacuum conditions onto this bilayered substrate. At low water content of the substrate titanium layer (the substrate layer still consists of metallic titanium) the growth of the clean titanium film is a continuation of the growth of the second substrate layer. As soon as the substrate titanium film contains only a few percent of water the initial compressive stress is overcompensated by atensile stress contribution which increases as the water content of the substrate isincreased. We interprete this to indicate renewed nucleation for the clean titanium film on the substrate surface. A small part of the tensile stress is also due to gas interdiffusion (hydrogen) from the substrate film. This effect is rather small when the second substrate film consists of stoichiometric oxide. With a MgF2 base layer in the substrate bilayer the results indicate a diffusing species from the MgF2 base layer into the Ti/TiOx layer. This interdiffusion from the substrate significantly affects the growth stress of the clean titanium film on this substrate bilayer. However, the general trends due to the incorporation of water in the substrate Ti/TiOx film, seen in case of the A12O3 base layer, are the same.
Brillouin Light Scattering Investigation of the Elastic Properties of Ta/Al Metallic Superlattices
Authors: Carlotti G. , Fioretto D. , Socino G. , Xia Hua , Hu An , Jiang S. S.
Published: April 2011

The Brillouin light scattering technique has been exploited for investigating the elastic properties of periodic superlattices made by alternating layers of Ta and Al. These multilayers, deposited by d.c. sputtering on glass and Si substrates, present a polycrystalline structure with (110) and (111) texture for the Ta and Al layers, respectively. They have total thicknesses of about 0.5 μm and periods ranging from 4 to 10 nm. Measurement of the phase velocities of the Rayleigh and Sezawa acoustic modes from the frequency position of the corresponding Brillouin peaks, yielded informaton on the effective elastic constants of the superlattices. for large periods (8-10 nm) the values determined experimentally are in good agreement with those calculated from the elastic constants of the bulk materials, while for lower periods (4-6 nm) the estimated elastic constants exhibit a marked increase. This anomalous behavior has been attributed to the presence of a transition layer at each interface, where Ta and Al interdiffuse, as observed by x-ray and electron microscopy experiments.
Measurement of Residual Stress In TiO2 Sol-Gel Thin Films Using Raman Spectroscopy
Authors: Hess Nancy J. , Exarhos Gregory J.
Published: April 2011

The deposition of thin films can result in residual stresses that affect film properties such as optical properties, phase stability, chemical durability, and film adhesion. There are many components to the total residual stress measured in a film. These include interfacial stress, volume changes associated with phase transitions, film thickness, and film microstructure. For sol-gel films, some contributors to residual stress can be controlled by such variables as the precursor chemistry and gelation time or heat-treatment following deposition. Measurements of the state of stress during crystallization or as a function of processing conditions and sol-gel chemistry allows optimization of film deposition parameters that promote minimal residual stress. We have constructed a three-dimensional surface in Raman shift-pressure-temperature space from spectroscopic measurements on single crystal anatase at high pressure and temperature. Location of the Raman shift of the two Eg modes of anatase on this surface the state of stress (pressure) and temperature of the film can be determined. For materials with large Raman scattering cross-sections, such as anatase, time-resolved crystallization experiments on films as thin as 100 nm are possible. Using this technique, the evolution of the state of stress during isothermal thermal and laser-induced crystallization processes can be monitored in real time and compared to the residual stress upon cooling.
Error Analysis In Nanoindentation
Authors: Shafirstein G , Gee M G , Osgerby S , Saunders S R J
Published: April 2011

This paper describes the results of an analysis of the errors that can arise during nanoindentation, and their effect on the final results. The sources of errors that have been considered are calibration errors in load, displacement, instrument frame compliance and indenter shape assuming a Berkovich indenter with an error in the included angle, and operational errors such as thermal drift and specimen tilt. An assessment of calibration errors indicates that a simple summation of errors was not appropriate in this case, since compliance and area function are depended upon displacement. Thus the error analysis has been carried out using a cumulative approach. As expected it was found that the errors increased with decreasing load and displacement, and increasing hardness and Young’s modulus. However, minimum errors were observed at about 20 mN and were a function of the indented material

No appreciable error was found in the hardness or Young’s modulus calculated from load-displacement data at surface angles below 8°; above this value the indenter started moving sideways over the surface, resulting in significant errors.
Mechanical Properties of Platinum Films on Silicon and Glass Determined by Ultra-Microindentation
Authors: Mencik Jaroslav , Swain Michael V.
Published: April 2011

Platinum films of thickness 0.5 - 1.2 - 3.0 μm, deposited by magnetron sputtering onto glass and silicon, were investigated using ultra-microindentation. The tests were done with a pointed (Berkovich) indenter. The values of the hardness and elastic modulus of the composite “film + substrate” and the substrates alone were obtained for various loads and depths of penetration, and used to evaluate the hardness and elastic modulus of the films. The use of various film thicknesses and substrates has enabled us to investigate in more detail the influence of the contact radius/contact depth compared to the film thickness as well as the substrate properties on the total indentation behaviour. Various approaches to the data evaluation are discussed in the paper.
Effect of Stresses in Thin Films on Defect Nucleation
Authors: Nandedkar A. S.
Published: April 2011

Computer simulations were used to investigate the effect of stresses on the energy of defects in Ge, Ge7% Si93% (referred to as alloy) films on Si and encapsulated aluminum thin films. In Ge films, misfit dislocations were energetically favorable over coherent interfaces. Although the alloy films had lower energy compared to Ge films, they also formed dislocations at film thicknesses greater than 25 – 30 Å. The energy of vacancy insertion at the film surface, which nucleates a misfit dislocation, increased with tensile stress. In encapsulated aluminum, agglomeration of vacancies leads to formation of voids. Simulations indicate that the activation energy of vacancy migration increased with compressive stresses. Thus compressive stresses in aluminum may prevent formation of voids, while tensile stresses in Ge film may prevent formation of misfit dislocations.
Stress and Adhesion of CVD Copper and TiN
Authors: Nguyen Tue , Evans David R
Published: April 2011

The use of copper for interconnect metallization on advanced submicron integrated circuits is attractive because of its inherent low resistivity. To date, chemical vapor deposition (CVD) processes which produce copper films with nearly bulk resistivity and good uniformity have been produced. However, adhesion of the copper deposit to underlying barrier materials, in particular to titanium nitride (TiN), has been problematic. In this work, adhesion has been measured using both a qualitative and a semi-quantitative method and has been correlated with process conditions and precursor formulation.
Material Properties and Related Considerations for Magnetomechanical Sensing Devices
Authors: Garshelis Ivan J.
Published: April 2011

Suitability of specific materials for use in magnetomechanical sensors more often depends on combinations of properties than on an outstanding value of a single property. These combinations include ratios and products of properties from different physical families. While magnetic, magnetoelastic, electrical and strength properties often play key roles in determining the performance of the sensor, non-physical characteristics such as manufacturability, available forms, environmental compatibility, toxicity and costs strongly influence the device design and may well dominate the final choice of material. The development of materials specifically for use in this class of sensors is encouraged by their already broad and growing range of applicability.
Chemical Microsensors for Satellite Applications
Authors: Weiller B. H. , Barrie J. D. , Aitchison K. A. , Chaffee P. D.
Published: April 2011

We have been investigating several chemical microsensor technologies for the detection of chemicals found in propellant and rocket exhaust plumes and as contaminants for satellite components. In this work we have developed a catalytic metal sensor for the detection of H2contamination in electronic device packages. The sensor is based on the resistance of a thin film Pd/Ni alloy. Data have been obtained on its response at room temperature to various levels of H2as well as the effects of H2O and O2on its performance. Hydrogen levels to 10.5 ppm have been detected and the responsivity is about twice that of similar sensors. The sensor is insensitive to H2O but its response to H2is strongly inhibited by O2.