bluuebunny/crossref_metadata_2025 huggingface dataset:
Allotaxy: A New Method for Epitaxial Growth of Compound Thin Films
Authors: Mantl S. , Bay H. L. , Dieker Ch.
Published: March 2011

A new method for the growth of epitaxial compound thin films, termed allotaxy, is proposed and the fabrication of the silicide heterostructure Si/CoSi2/Si(100) Is demonstrated. Allotaxy is a two. step process. In our example, Si is deposited on a heated Si substrate and then Co is coevaporated at varying rates such that a peaked Co-depth profile in Si is generated. At appropriate deposition conditions CoSi2 precipitates embedded in single crystalline Si are formed. These precipitates coarsen and coalesce into a buried, uniform, epitaxial CoSi2 layer during the second processing step, a high temperature anneal. Allotaxy should allow not only the epitaxial growth of silicides but also that of other binary, precipitates forming systems.
Formation of Heterogeneous Thickness Modulations During Epitaxial Growth of LPCVD-Si1−xGex/Si Quantum Well Structures
Authors: Vescan L. , Jäger W. , Dieker C. , Schmidt K. , Hartmann A. , Lüth H.
Published: March 2011

Transmission electron microscopy and photoluminescence studies were performed to determine the critical thickness for generation of misfit dislocations in Sil-xGex layers grown by low pressure chemical vapor deposition. Above a certain Ge content the transition from two dimensional to three-dimensional growth occurs before generation of misfit dislocations. For instance, for x ∼0.3 and a substrate temperature around 700°C island formation was observed to start at 1.8 nm. The formation of islands is attributed to the preferential growth of SiGe in areas with less lattice strain. Islands were observed to broaden the exciton photoluminescence of the quantum well structures.
Observation of the Ordered CoPt3 Alloy in Co-Pt Multilayers
Authors: Toney M.F. , Farrow R.F.C. , Marks R.F. , Harp G. , Rabedeau T.A.
Published: March 2011

We report results of a synchrotron X-ray diffraction study of Co-Pt multilayers, with Pt[111] as the growth axis. The multilayers were grown by MBE on Pt seedfilms on basal-plane sapphire substrates at growth temperatures of 100 and 200ºC.The multilayers comprised 15 periods of Co 3Å, Pt 15Å and both exhibited perpendicular anisotropy. Grazing-incidence radial- and phi-scans revealed a set of {110{ peaks indicating doubling of real space periodicity consistent with the presence of the ordered alloy CoPt3. This supports the results of other studies which indicate interdiffused interfaces in Co-Pt multilayers and shows that chemical ordering can occur at much lower temperatures than in bulk alloys where annealing times of several days at ∼ 700ºC are required to stimulate ordering.
Atomic Structure of Interfaces in Epitaxial NiSi2 on (001) Silicon
Authors: Chen W.J. , Chen F.R. , Chen L.J.
Published: March 2011

High resolution transmission electron microscopy (HRTEM) has been applied to study the atomic structure of NiSi2 /(001)Si interface. Previous HRTEM result suggested that Ni atoms in the boundary core are six-fold coordinated and Si atoms are everywhere tetrahedrally coordinated. In this work, high resolution imaging technique and computer image simulation were used to study the atomic structure of NiSi2 /(001)Si interfaces and a new interface structure was found. For the new interface structure, Ni and Si atoms are also six-fold and tetrahedrally coordinated, respectively, with an extra layer of fourfold planar bonded Si atoms present at the interface.
Relationship between Self-Texture and Interfacial Restriction on the Epitaxy of (Ca,Sr)CuO2 Thin Films
Authors: Nagai Satoshi , Tanaka Hideaki , Fujimura Norifumi , Ito Taichiro
Published: March 2011

The Orientation control of (Ca,Sr)CuO2 film has been investigated under various sputtering conditions from the view point of controlling the “self-texture” and epitaxy. The films with (001), (110) and (101) orientations were able to be obtained by changing partial gas pressure during sputtering. These orientations were observed on glass and MgO(100) single crystal substrates. The cohesive energy between the film and the MgO single crystal substrate was calculated to evaluate the change in orientation on glass and MgO substrates.
Growth and Characterization Of GexSi1−x/ Si Multiple Quantum Well Structures
Authors: Greve D.W. , Misra R. , Capano M.A. , Schlesinger T.E.
Published: March 2011

We report on the growth and characterization of multiple quantum well structures by UHV/ CVD epitaxy. X- ray diffraction is used to verify the expected layer periodicity and to determine the quantum well thickness. Photoluminescence measurements show peaks which we associate with recombination of excitons in the quantum wells. The measurements are consistent with high quality layers with small variation in quantum well thickness across a wafer.
Dependence on MOCVD Growth Temperature of The Photoluminescence Properties of ZnSe, ZnTe, and ZnSe(1-x)Te(x) Alloys and ZnSe/ZnTe Superlattices
Authors: Ponga B.E. , Calas J. , Averous M. , Cloitre T. , Briot O. , Gil B. , Aulombard R.L.
Published: March 2011

It has been recently shown that high quality ZnSe and ZnTc filns can be grown on GaAs using low temperature growth techniques such as Metal-Organic Chemical Vapor Deposition ( MOCVD). All samples: ZnSe, ZnTe, ZnSc(l−x)Tc(x) epilayers and ZnSe/ZnTc superlattices were grown using a novel zinc precursor, the Tri-Ethyl-Amine Di-Methyl-Zinc, while we used the classical precursors H2Se and Di-Isopropyl-Tellurium for selenium and tellurium. Investigation of the photoluminescence (PL) properties of ZnSc and ZnTe single layers enabled us to optimize the growth conditions of these compounds. The crystal growth conditions for mixed alloys and superlattices were determined by direct comparison to the aspect of low-temperature PL features. Strong PL spectra were obtained from these materials, suggesting us that tellurium has the ability to behave like an iso-clectronic center. At low concentration of tellurium in ZnSe, an interesting physical situation is observed, which we have interpreted in terms of extrinsic exciton “self-trapping” mechanism.
Anisotropic Electron Mobility of Two-Dimensional-Electron-Gas in Modulation Doped Inx.Ga1−y As/InyAl1−yAs Heterostructures
Authors: Chen Jianhui , Fernandez J.M. , Wieder H.H.
Published: March 2011

We have investigated the electrical properties of the two-dimensional-electron-gas (2DEG) present in strain relaxed heterojunctions with InxGa1−xAs channels (x<0.4). These were grown by molecular beam epitaxy on misoriented (001) GaAs substrates using compositionally step graded buffer layers, … x' = 0.1 per step, each step 0.3 µm thick. The 2DEG is produced by modulation doping using lattice matched InyAl1−yAs as the carrier supply layer. We find typical electron densities and mobilities, for x=0.3, of ns(300 K) = 1.3 × 1012 cm−2 and µH(300 K) = 9300 cm2/V-s; and for ns(1.6 K) = 1.2 × 1012 cm−2, µH(1.6 K) = 37800 cm2/V-s. While the room temperature electron mobility shows negligible anisotropy, an <110>-orientation dependent low temperature electron mobility of the 2DEG is observed and attributed to dislocation scattering.
Strain Relief Mechanisms in The Growth of GexSi1−x/Si(110) Heterostructures
Authors: Hull R. , Bean J.C. , Weir B. , Peticolas L.J. , Bahnck D. , Feldman L.C.
Published: March 2011

We describe a detailed quantitative theoretical and experimental analysis of strain relief mechanisms in GexSi1−x/Si(110). For this interface, both partial and total glide dislocations may effect strain relief. Detailed comparison between experimental measurement and theoretical prediction of the regimes in which the two types of dislocations are observed allows a very accurate determination of the stacking fault energy in GexSi1−x alloys.
Properties and Strain Relaxation below Room Temperature of Epitaxial Pbse and Pb(Se,Te) on Fluoride-Covered Silicon Substrates
Authors: Maissen C. , Zogg H. , Blunier S. , Sultan A. , Teodoropol S. , Richmond T. , Tomm J.W. , Kostorz G.
Published: March 2011

Narrow-gap PbSe and PbSe1−xTex films were grown by MBE on 3n-Si(111) wafers. The layers are used for IR-sensor array applications. Epitaxy was achieved by using an intermediate CaF2/BaF2 bilayer to overcome the large difference in lattice constants (14%) and thermal expansion coefficients (700%). While PbSe is rather soft, the hardness increases with x (x<0.5) in PbSe1−xTex. Thermal stresses are relieved by dislocation glide on (100)-planes, leading to slip lines on the surface. The surface morphology and step heights were studied with the scanning tunneling microscopy technique, and a model for the resulting (111)-surface structure is presented. The value of the remaining strain was determined with precision Rutherford backscattering spectrometry absolute angle measurements, X-ray diffraction and photoluminescence in the temperature range down to 10 K. It is found that no appreciable strain builds up even at cryogenic temperatures and after many temperature cycles. In contrast to PbSe, ternary PbSe1−xTex layers are strained elastically below room temperature owing to solid solution strengthening, and plastic deformation occurs only at higher temperatures.
Quaternary Alloys InxAlyGa1−x-yAs Grown on GaAs with A Compositionally-Step-Graded Buffer
Authors: Fan C. , Shih D. W. , Hansen M. W. , Chen J. , Lee P. Z. , Esener S. C.
Published: March 2011

Fundamental bandgaps and Schottky barrier heights of strain-relaxed quaternary InxAlyGa1−x-yAs alloys with 0 < x < 0.35 and 0 < y < 0.30 were studied. The alloys were grown on GaAs substrates by molecular beam epitaxy. The lattice mismatch (up to 2.5%) and mismatch strain were accommodated by a compositionally-step-graded buffer. A residual compressive strain of less than 0.5% was determined by x-ray diffraction. Measured Schottky barrier heights v.s. bandgap deviate from the values predicted by the “commonanion” rule. This behavior is attributed to the compositional inhomogeneities and chemical reactivity of the air-exposed InAlGaAs surfaces.
X-Ray Diffraction Determination of Critical Thickness of InAs and InP on GaAs Grown by Atomic Layer Molecular Beam Epitaxy
Authors: Mazuelas A. , Gonzalez L. , Tapfer L. , Briones F.
Published: March 2011

Two series of samples consisting in a strained layer of InAs (InP) of different thickness, InAs N monolayers (ML) with N=1,2,3, and 4, and, InP M ML with M=2,3,4,5,6 and 7, covered by a GaAs cap layer of 200 nm were grown by Atomic Layer Molecular Beam Epitaxy (ALMBE).

The samples have been characterized by X-ray diffraction in order to measure the critical thickness of InAs and InP on GaAs.

Computer simulation using dynamical theory of X-ray diffraction is used to fit the experimental patterns. In this way we determine the composition, thickness, and strain both in the strained layer of InAs or InP and in the cap layer of GaAs.

A disagreement between simulated and experimental curves is reached at a thickness where the beginning of relaxation takes place (i.e. critical thickness). We have found that the critical thickness of InAs on GaAs(001) is 2.3 ML (0.75 nm) and the critical thickness of InP on GaAs(001) is 5.6–5.7 ML (1.71-1.74 nm), both grown by ALMBE.
Tem Study of Temperature Influence on The Crystalline Quality of InGaAs/Si Epilayers
Authors: Vila A. , Cornet A. , Morante J.R. , Westwood D.I.
Published: March 2011

A Transmission Electron Microscopy (TEM) study of In0.53Ga0.47As Molecular Beam Epitaxy films grown at different temperatures onto misoriented Si (100) substrates is presented. The evolution of the density of the different kind of defects is discussed as a function of the growth temperature in the range between 200 and 500° C. The results are compared with the characterization techniques of Double Crystal X-Ray Diffraction and Hall effect.
The Chemical Interaction of Disilane on Ge(100)
Authors: Lapiano-Smith D. A. , McFeely F. R.
Published: March 2011

The room temperature chemisorption of disilane on Ge(100) and subsequent reaction at elevated temperatures was investigated by core level photoemission spectroscopy. At room temperature Si2H6 chemisorbs dissociatively on Ge(100) forming a surface populated largely by Si-H groups. Annealing the sample to 300°C effectively reduces the Si-H species to elemental Si. An additional anneal to 580°C promotes the diffusion of Si into the bulk and restores the Ge surface to an atomically clean state.
VLPCVD Heteroepitaxial Growth of Very Thin GE-Layers on Si-Substrates
Authors: Caymax Matty R. , Poortmans J. , Ammel A. Van , Nus J. , Vandervorst W. , Vanhellemont J. , Brus B.
Published: March 2011

By Pulsed Gas CVD-growth, heteroepitaxial growth of pure Ge-layers from pure GeH4 has been accomplished at 650 °C on Si-substrates without intermediate Si1−xGex-bufferlayers. The material has been studied by means of RBS, SEM, ECP, XRD and cross-sectional, highresolution and plan-view TEM. The thickness of the Ge-layers varied between 2 and 24 monolayers. From 5 monolayers on, some part of the Ge appears to be fully relaxed. Uptill 12 monolayers, the growth is fully 2-dimensional and results in specular, flat surfaces; for thicker layers islanding starts (Stranski-Krastanow growth). The material is completely defect-free. According to XRD-measurements, the perpendicular strained Ge-cell dimension is 5.748 Å, which is very reproducible for all layer-thicknesses. Nevertheless, from linear elastic theory considerations, it should be 5.83 Å. The Ge-layers so formed appear to be suitable for use in short-period (SinGem)p-superlattices.
Uni-Directional Shrinkage Sintering for Ceramic Packaging Substrates with Low Dimensional Tolerances
Authors: Kodama Hironori
Published: March 2011

Uni-directional shrinkage sintering technology was studied to fabricate ceramic packaging substrates which meet requirements of very low dimensional tolerances (high dimensional accuracy). Three methods were considered. The first method used laminating of long fiber sheet materials and showed restraining effects on X, Y-directional (plane dimensional) shrinkage. However, the restricting ability was not sufficient for thicker laminates of the green sheets. The second method incorporated short fibers with a planar arrangement in green sheets, and some constraining effects on X, Y-directional shrinkage were observed with increasing short fiber content and modification of the fiber mixing method. But there was concurrent lowering of densification. The third method applied pressure lightly during sintering without using a mold. Control of the sintering shrinkage was relatively easy and X, Y-directional shrinkage of less than 0.1% was achieved by selecting a suitable pressure for the process. This method is very simple and easy to control, ensuring products of high dimensional accuracy.
Characterization of Polyimide Thin Films on Metals
Authors: Lu Jiong-Ping , Nagarkar Pradnya V. , Volfson David , Jensen Klavs F. , Senturia Stephen D.
Published: March 2011

We describe an approach using thin films on metals as models to study interfacial interactions. Thin films of biphenyl-tetracarboxylic dianhydride (BPDA) - p-phenylene diamine (PPD) based polyimide on Cr and Au surfaces have been investigated using infrared reflection absorption spectroscopy (IRRAS) and x-ray photoelectron spectroscopy (XPS). IRRAS was used for in-situ monitoring of polymer curing processes. Cured polyimide thin films on metals were characterized ex-situ by both XPS and IRRAS. Anhydride was observed to be an intermediate during chemical transformation of polyamic acid to polyimide. Imidization processes were found to be completed after curing at 250°C for thin films. Strong chemical modification of polyimide thin films resulting from interaction with Cr substrates were observed by infrared spectroscopy. These observations were consistent with angle-resolved XPS data showing a different C 1s emission spectrum of polyimide-Cr interfacial region, compared to the polyimide spectrum.
Waxd Study of Low TCE Polyimide Films Formed from Polyamic Acid Blends and Copolymers.
Authors: Nunes Thomas L. , Sachdev Krishna G.
Published: March 2011

Low TCE polyimides, typically BPDA-PDA and related materials are well known for their special properties which include low in-plane TCE, up to 3X higher elastic modulus and ultimate tensile strength, and lower moisture uptake relative to the commonly known flexible chain polyimides [1]. These differences are due to the rod-like orientation and highly organized molecular structure of the polyimides that are derived from linear-planar precursors resulting in more anisotropic properties such as the X-Y vs Z-direction TCE [2], and optical as well as dielectric properties.

In the present study, we have measured the WAXD patterns of polyimide films formed from BPDA-PDA and BTDA-PDA polyamic acid mixtures and BPDA-BTDA-PDA random copolyamic acids. In order to examine the effect of a highly flexible chain segment on the molecular anisotropy of rod-like polyimides, preliminary WAXD patterns were recorded for films of BPDA-BDAF and a BPDA-PDA-BDAF copolyimide.

An in-plane and an out-of-plane crystallinity index, measures of molecular order within the polyimide films studied were estimated from the WAXD patterns. The data are correlated with the various blends and copolymer compositions and discussed in terms of structural implications.
Chemistry Of Solid/Solid Interfaces
Authors: Opila R. L.
Published: March 2011

The chemistry that occurs at buried interfaces often determines the performance and reliability of multi-chip modules (MCM's). For example, chemical reactions between sputter deposited metals and polymers may ultimately determine the interlayer adhesion of multilevel metallizations for MCM's. Both destructive and non-destructive probes can used to study these interfaces, and the interfaces may be studied as they are formed or as they age. Complicating the interpretation of any of the results of these techniques is the inherent complexity of the chemistry and, often, the non-planarity of the interface. Several examples of complex interfaces will be described along with strategies for elucidating the chemistry and their reliability.
Characterization and Use of Polyfluorosiloxanes in Automotive Applications
Authors: Polak Anthony
Published: March 2011

Polysiloxanes are routinely used in the semiconductor industry as die encapsulants. Thermal analysis, NMR, ion chromatography, and dielectric spectroscopy was used to characterize these polymers. The dielectric loss spectrum was found to be directly related to the long term electrical stability of the encapsulated die, and was also found to be a more sensitive technique for determining the concentration of electronically active impurities than GC/MS, and ion chromatography. Dielectric spectroscopy was also used to study the diffusion of acids, and water, through these polymers. While the solubility of acids and water in these materials is low, their diffusion constants are high, on the order of 10−4 cm2/s. In addition, the interaction of the encapsulant with the silicon nitride passivation used on the die surface was found to have an effect on the long term stability of the device. This is believed to be due to the formation of a conductive layer at the silicon nitride/polymer interface which ultimately forms a leakage path between the bond pads, or into the silicon nitride passivation layer.
The Application of Surface Mount Technology in Consumer Products
Authors: Hakuta Tatsuo , Ishikawa Minoru
Published: March 2011

This is an introduction to Sony's pocket-sized computer “The palmtop”, an example of surface mounting technology applied to a consumer product.
An Overview of Multichip Module Technology for low Power Applications
Authors: Ho Chung W. , McAfee-Hunter Sharon
Published: March 2011

Thin-film multichip modules (i.e. MCM-D) can provide simple, low-cost packaging and interconnect options for interconnecting high-density, high-performance devices. The following is an overview of an MCM-D technology that can be implemented on top of several substrate materials. Tradeoffs will be discussed related to using different substrate materials and the corresponding implications from the assembly point of view. The MCM-D manufacturing process is reviewed and the subsequent reliability results are discussed.
Coupling of Light into Single-Mode Optical Fiber for Data Communications
Authors: Lasky Ronald C. , Mackay Janet L. , Österberg Ulf , Jen Keh-Chee , Carlson Kurt D.
Published: March 2011

Single-mode optoelectronic communication is the technology of choice in the telecommunication industry, due to the long distances and high data rates that are achievable. These benefits are now being exploited in the field of data communications. However, the demands of the data communication application are somewhat different from those of telecommunication. This paper discusses these differences.

Typical optical performance parameters for the data link are also considered. The two most important of these parameters are the laser safety limit and the minimum launched power. The methodologies which assure both of these parameters are presented.

The physics of single-mode fiber-to-fiber and laser-to-fiber coupling is reviewed, including an overview of various theoretical models which have been used. Results of ongoing experimental studies are presented and compared to a theoretical model. Discrepancies between the experimental results and the model are discussed.
Fluorinated Parylene as an Interlayer Dielectric for Thin Film MCM's
Authors: Dabral S. , Zhang X. , Wu X.M. , Yang G.-R. , Lang C.-I. , Bakhrut H. , Olson R. , Lu T.-M. , McDonald J. F.
Published: March 2011

Aliphatic tetrafluoro-poly-p-xylylene (PA-f), has been evaluated as an interlayer dielectric and its properties reported. It has a lower dielectric constant (2.38) and higher thermal stability (480°C) than Parylene-n. The as-deposited films are of very low crystallinity. The crystallinity increases as the film is annealed. Thermo-Gravimetric Analysis has shown that these films loose weight at temperatures > 480°C. A shrinkage in the films of about 10% was observed when annealed in vacuum at a temperature of 425°C. The as-deposited films were measured to have low dielectric constant of 2.38 and a volume resistivity of 1.3×1016 ohm-cm. The refractive index in the optical wavelengths was measured to be 1.3 for as-deposited samples which increased with anneal temperatures. The stress levels observed are also lower (19 MPa) than PA-n (40 MPa) after annealing. Diffusion of Cu into PA-f is comparable with Cu diffusion in PMDA-ODA polyimide. Scanning Electron Microscopy of film cross-section shows microstructure change above temperatures of 350°C.
Surface Energy Compatibilites of Cellulose and Polypropylene
Authors: Quillin Daniel T. , Caulfield Daniel F. , Koutsky James A.
Published: March 2011

In addition to its use in recycled paper products, recovered lignocellulosic fiber can be used as a reinforcement filler in composites with polyolefins. However, problems in both processing and product performance are often caused by the incompatibilities of surface energies between hydrophilic cellulose and non-polar polyolefin. This poor match in surface polarities is detrimental to strong adhesive bonding between olefin and cellulose. This work examines the effect of surface energy on the adhesion properties of polypropylene and cellulose. In particular, three materials accepted as paper-sizing agents were used to change the cellulosic fiber's surface energy to make it more compatible withthe surface energy of polypropylene.

Cellulose fibers were treated by various methods with (1) alkyl ketene dimer, (2) alkenyl succinic anhydride, and (3) stearic acid and were characterized by their surface energies as determined by single fiber wettability measurements using the Wilhelmy technique. These measurements are discussed in detail. Results from these measurments can be related to differences in adhesion between treated cellulose and polypropylene, which can be measured by internal bond tests on hot-pressed composite sheets.

Results indicate that the use of sizing agents reduces the acid/base (hydrogen bonding) character of the cellulose surface. Interactions involving hydrogen bonding are important in cellulose/modified-polypropylene composites. Reduction of these interactions appears to lead to a corresponding reduction in adhesion between cellulose and polypropylene.
Polypropylene Crystallization on Maleated Polypropylene-Treated Wood Surfaces: Effects on Interfacial Adhesion in Wood Polypropylene Composites
Authors: Kolosick Paul C. , Myers George E. , Koutsky James A.
Published: March 2011

Polypropylene (PP)-wood veneer laminates were used as a model system to investigate adhesion in wood-polypropylene composites. Wood veneers were treated with maleated polypropylene waxes (MA-PP). PP films were then compression molded to the wood surfaces and peel forces were measured.

Low MA-PP treatment levels increased the peel adhesion over that for untreated surfaces. High MA-PP treatment levels decreased the peel adhesion and intermediate MA-PP levels had no effect on the peel adhesion. Microscopy of the fracture surfaces indicated PP penetration into lumens in both treated and untreated wood veneer. Untreated surfaces also exhibited PP penetration into pits and intercellular spaces, while treated surfaces exhibited only hindered penetration on this scale. The penetrated PP formed tendrils during fracture. DSC of PP on wood and cellulose surfaces showed higher PP crystallization temperatures on untreated surfaces than on treated surfaces.
Application of Solubility Parameters to Lignocellulosic/Thermoplastic Composites
Authors: White Don H. , Park S. C.
Published: March 2011

The usefulness of solubility parameters in identifying miscible polymer blends is reviewed. The use of wood fibers in mixtures of recycled thermoplastics is of current interest. These composites do not require miscible blends of polymers, but must exhibit compatibility in order to have good adhesion and physical properties. The use of solubility parameters to design improved composites is cited. This approach is then applied to wood fiber/polyolefin thermoplastic composites.
Enzymatic Solutions to Enhance Bonding, Bleaching and Contaminant Removal,
Authors: Jeffries Thomas W. , Patel Rajesh N. , Sykes Marguerite S. , Klungness John
Published: March 2011

Microbial enzymes can enhance the properties of virgin pulps and secondary fibers. Enzymes added to pulp slurries at key steps during fiber processing alter structure and composition of native substrates in specific ways. Lipases hydrolyze fatty acid esters thereby facilitating depitching and deinking. Cellulases remove fines and change surface properties, thereby enhancing drainage, deinking, and contaminant removal of secondary fibers. The binding domains of cellulases exfoliate or roughen the surface of cellulose fibers. This feature may be used to enhance inter-fiber bonding. Xylanases and ligninases enhance lignin and chromophore removal thereby facilitating bleaching of kraft pulps. Microbial xylanases reduce chemical demand for bleaching by 35 to 50% in softwood and hardwood pulps, respectively. Many extracellular microbial enzymes are stable at 50 to 60°C and between pH 4 and 7, and some function well at greater extremes. In some instances crude enzymes can be used, but by cloning and expressing pure enzymes at high titers more precise and economical applications can be achieved.
Micro and Macromorphology of Recycled Fiber and Wood
Authors: Stokke Douglas D.
Published: March 2011

Wood is a major industrial raw material, with U.S. consumption approaching that of aluminum, plastics, cement, and steel combined. Partially as a result of the magnitude of wood and wood products in use, these products constitute a substantial portion of the solid waste stream. In order to reduce the amount of wood and wood fiber disposed in landfills, efforts to recycle these materials into useful products such as structural composites are needed. The success of such conversion depends in part on knowledge of the morphological characteristics of various sources of secondary wood and wood fibers, and the influence of wood element morphology on composite properties. An overview of wood and fiber morphology representative of major sources of secondary material is provided, with a discussion of how these morphological features may influence the properties of conventional wood composites and wood fiber/plastic composites.
Interpretation of Bronze Disease and Related Copper Corrosion Mechanisms in Terms of Log-Activity Diagrams
Authors: McNeil Michael B. , Mohr D. W.
Published: March 2011

Thermochemical data are used to construct a modified log-activity diagram for the system Cu-H-O-Cl-(C02) at standard temperature and pressure(STP). In these diagrams, coordinate axes represent activities of aqueous copper species and chloride ions other thermodynamic variables are collapsed onto the diagram. Modified log-activity diagrams are used as a supplement to study Pourbaix diagrams for the equilibria relevant to bronze disease and copper pitting and to show the relation between them.
A New Corrosion-Protective Polymer for Artifact Display and Storage Applications
Authors: Franey J. P. , Donaldson Keith
Published: March 2011

Corrosion of artifacts from atmospheric trace gases occur continuously. A new polymeric system which provides atmospheric trace gas corrosion protection has been developed. These polymers are called Reactive Polymers. The polymers consist of a blend of polymer resin (eg. polyethylene, polypropylene, ABS, PVC) with stable solid-state additives. These polymers can be formed into bags, tubing, sheets, bubble-pack, trays, etc. Corrosion protection is provided for artifacts from ancient periods, such as chinese mirrors, and the Freer Chinese Bronzes, to fine silver items from Colonial times in the USA. This protection from corrosion or tarnish by atmospheric H2S, COS, and HCl is provided for extended periods of time.
Croatian Monuments as Targets, 1991/92
Authors: Belamarić Jošgko
Published: March 2011

The purpose of this talk is to give a brief account of the current situation in Croatia—a small country located between the Adriatic sea and the Danube, along the south-eastern spur of the Alps. I would like to begin with some general remarks about the Croatian cultural heritage and the damage that has been inflicted on it by nine months of exceptionally brutal warfare. I will give some rather dry statistics, but it is important to keep in mind that each of these statistics represent an act of appalling vandalism of a kind that has not been seen in Europe for a generation. I will then focus on the specific cases of Dubrovnik and Zadar. Since both of these cities are under the jurisdiction of my Institute I can report about them in some detail from personal experience. Finally I have some concrete proposals for what could be done to mitigate the effects of the damage already caused to cultural monuments by the war in Croatia. Croatia desperately needs immediate international help to preserve its cultural heritage. I will report on some initiatives already under way.
A Holistic Approach to the Analysis of Archaeological Deposits, Illustrated Using a Late Roman Urban Sequence From Northwest Europe
Authors: Farrington Orpah S. , Bateman Richard M.
Published: March 2011

Dark Earth deposits immediately overlie late Roman urban stratigraphy across northwest Europe, representing the crucial but poorly documented collapse of provincial Roman urbanism. Deficient in artefacts, they have proved recalcitrant to traditional methods of archaeological interpretation. Here, they are used as a vehicle to promote a more integrated, holistic approach to scientific archaeology. This recognises the great potential value of applying a wide range of geoanalytical techniques to the finer-grained matrices that enclose (or, more precisely, grade into) artefacts in archaeological sequences. As this multifaceted approach is time-consuming, deposits chosen for analysis should contain potential answers to profound historical questions. Comparative studies are necessary, in which samples of known age, provenance, environment and mode of deposition outnumber those of a more equivocal nature. Considerable knowledge is required to select the optimal range of complementary techniques for application to a particular suite of materials; this case study outlines the relative merits of analyses for fabric orientation, particle size, micromorphology, bulk geochemistry (ICP), particle geochemistry (microprobe), heavy mineralogy, plant remains (pollen, phytoliths, wood), animal remains, macroscopic artefacts, and radiometric dating. The resulting large bodies of data are best summarised by multivariate analyses (notably ordination algorithms), together with semivariograms for spatial data. Interpretations should take full account of the range of anthropogenic processes and products inherent in archaeological deposits.
A Technical Examination of the Chinese Buddhist Bronzes in the Freer Gallery of Art, Part B: Stable Lead Isotope Analysis
Authors: Sayre Edward V. , Jett Paul , Joel Emile C.
Published: March 2011

Stable lead isotope ratios were determined on sixty-four samples taken from sixty of the Buddhist bronze images which were examined and chemically analyzed by Jett and Douglas [preceding paper]. The data were grouped using multivariate techniques and were compared with an accumulated data base of lead isotope measurements on more than 700 ancient Chinese artifacts and more than 200 Chinese and Korean ores. One group of ten images which were all datable to a period of less than one century, Eastern Wei through Sui dynasties, form a nearly unique isotopic group which coincides only with an unusual group of Lengshuichong bronze drums. A second large group of thirty-two isotopically matching images contains almost all, fifteen out of sixteen, of the images attributed to the Northern Wei dynasty. The remaining members of this group are of later date, extending into the Tang dynasty, or are animal figures attributed more generally to the Six Dynasties. This group partially overlaps somewhat the isotope fields of some Western and Eastern Han mirrors and some of the Sackler ritual bronze vessels of the Shang and Zhou dynasties, but appears to have been derived from a different ore source from them. The remaining specimens break up into some very tentatively defined small groups of two to four specimens each and a small residue of four unique, unmatched specimens.
Effects of Drying on the Mechanical Properties of Paper and their Relationship to the Treatment Of Paper
Authors: Vitale Timothy
Published: March 2011

The effects of drying on paper after water immersion are explored by evaluating mechanical properties. When paper is wet, structural interfiber hydrogen bonds are disrupted; drying reverses this process. However, some “as manufactured” mechanical properties are lost after wetting and drying. The method of drying was found to be critical for regaining the mechanical properties of a dried sheet.

The effects of (1) wet-pressing (weight on paper during drying) and (2) wet-straining during drying are assessed. Application of incremental increases of the two variables results in changes of the mechanical properties which eventally reach and exceed the original mechanical properties which are lost during standard water immersion and drying treatments.

The treatment method which most closely reproduces the “as manufactured” properties involves wet-pressing and wet-stretching. In particular, friction stretch-drying in an air-bag press can approximate original drying conditions. However, alterations of optical properties of the paper and design media due to elevated pressure prevents endorsement of the methodology.
Changes in the Infrared Absorbance and Color of Aged Cellulose Film
Authors: Mayhew Frances Whitaker , Block Ira
Published: March 2011

The accelerated aging of unplasticized Cellophane film specimens was conducted at tempe:atures ranging from 80 to 150 °C in a dry, forced-air convection oven for various periods of time. Colorimetric evaluation showed increasing discoloration which could be partially reversed by rinsing in deionized water. The infrared spectra of samples aged within this temperature range show the same changes, dependent upon aging time. This indicates that the species formed in the films at temperatures above and below the boiling point of water are the same, and that the moisture content of the films may affect the reaction rate, but not the mechanisms. The observed data in the visible region fit the standard pseudofirst-order kinetics model and are in excellent agreement with those determined for both the color change of cotton and the UV absorbance of Cellophane under similar conditions.
The Work of the Potter in Ancient Mesopotamia During the Second Millennium B.C.
Authors: As Abraham Van , Jacobs Loe
Published: March 2011

In the beginning of the second millennium B.C. Babylon became the centre of power in Mesopotamia. Hammurapi (1792-1750 B.C.) was one of the most important kings of the First Dynasty of Babylon. He is above all known for his law code (Codex Hammurapi). At the height of his power the Old Babylonian Empire extended as far as Sumer in the south and to Nineveh in the north. After the Old Babylonian times a dark period followed in the history of Mesopotamia. The conquest of Babylon in 1595 B.C. by the Hittite king Mursilis I ended the First Dynasty of Babylon. His allies, the Kassites from the Zagros Mountains, occupied Babylon without breaking the Babylonian traditions. Dur Kurigalzu became their capital. In 1157 B.C. the Kassite Dynasty was attacked from Elam (southwestern Iran) and came to an end.
Metalworking at Hengistbury Head, Dorset and the Durotrigan Coinage: A Reinterpretation of an Iron Age and Roman Industrial Site
Authors: Salter Chris J. , Northover J. Peter
Published: March 2011

The excavation of the metalworking areas of the late Iron Age and early Roman port of Hengistbury Head in southern England revealed evidence of a wide range of processes. These involved gold, silver and copper alloys and their connections with the local Iron Age coinage as well as the casting of bronze artefacts and ironworking. Since publication, in 1987 re-analysis of some material coupled with an extensive analysis of the associated coinage has led to a re-interpretation of the material. This paper presents the new perspective on the site as a metallurgical centre that has emerged as a result of our analyses.
Porcelain on Display Decorative and other Uses of Oriental Porcelain in Europe
Authors: Impey Oliver R.
Published: March 2011

Chinese porcelain began to reach Europe in quantity in the late fifteenth century, Japanese in the mid seventeenth. Apart from a brief interlude in the mid seventeenth century, Chinese porcelain was imported until well into the nineteenth century, Japanese only until the 1740s. This porcelain was at first a rarity, to be mounted in precious-metal mounts or kept in the Cabinet of Curiosities. Soon it was to be displayed as part of the decorative effect in a room, while in some cases it became the decorative effect; the porcelain room. Porcelain was imitated in Europe and not much used until it was cheap enough. As the “China-mania” died, porcelain was kept as part of room decoration, often in the new china cupboards.
Understanding Post-Depositional Processes Through Electron Microbeam Analysis of Archaeological Bone From Se Missouri
Authors: Greenlee Diana M. , Dunnell Robert C.
Published: March 2011

Archaic period bone in Southeast Missouri characteristically displays a patchy black and reddish brown staining not found on bone from other-aged sites in the area. The stained areas appear to be post-depositional additions to the bone matrix. Preliminary tests suggest that the stain is inorganic and is rich in Mn and Fe. Here, electron microbeam analysis is used in conjunction with SEM imaging to identify elements specifically linked to the staining. Comparisons are made between the elemental composition of bone and associated sediments from several different-aged occupations. Variability in postdepositional environment between occupations is documented and related to the presence of the staining.
Suppression of Island Formation During Initial Stages of Ge/Si(100) Growth by Ion-Assisted Molecular Beam Epitaxy
Authors: Tsai C.J. , Atwater H.A.
Published: March 2011

We have observed a suppression of island formation and an increase in the thickness limit for layer-by-layer growth of Ge on Si (100) by ion-assisted molecular beam epitaxy. Island suppression is observed both for ion energies at which surface defect generation dominates bulk defect generation and at which the majority of defects generated are bulk defects. This experiment, in conjunction with results of a linear elastic stability model for islanding, reveals that the kinetic mechanism for the suppression of island formation via ion bombardment is the reduction of surface amplitude fluctuations during the early stages of growth.
Some Properties of a-SixC1−xH Films Prepared by a Mixed Frequency PECVD Process
Authors: Minkiewicz V.J. , Stasiak J. , Moore J.O. , Eaton R. , Eldridge J.M.
Published: March 2011

The purpose of this paper is to discuss the results of experiments that were done to develop a process to reliably produce low-stress a-SixC1−x:H films by PECVD. The films were deposited at 380 °C in a horizontal hot wall reactor using mixtures of silane and methane. The unique feature of the reactor is that, In contrast to others, the plasma was powered by two power sources; one was operated at 450 kHz, the other at 13.56 MHz. The plasma was maintaired in a mixed frequency mode during deposition. The total energy input to the plasma during a duty cycle was kept fixed while the properties of the films were altered by adjusting the relative energy output of each power supply. The energy output of each generator was adjusted by changing their on-times and peak powers. The composition of the films, their Initial stress, and the behavior of their stress during a temperature anneal were studied extensively. The Si/C ratio of the films varied from 0.3 to 3.0. The hydrogen concentration varied from 24 to 32 atomic percent. The initial stress was controlled by frequency mixing, and varied from −400 MPa to + 100 MPa.
Microstructural and Magnetic Characterization of Ni Films with In-Plane Anisotropy Induced by Ion Bombardment During Growth
Authors: Lewis W. A. , Saffari H. , Farle M. , Kay E. , Hagstrom S. B.
Published: March 2011

Ni films 250 to 1500 Å thick are prepared on polished amorphous quartz substrates in ultrahigh vacuum by ion beam sputter deposition. The growing film is bombarded simultaneously with Xe+ ions at an oblique angle of incidence. The structural and magnetic modifications are studied for different film thicknesses as a function of Xe+ ion energies (50–200 eV) and relative flux of arriving Ni atoms/Xe ions at the substrate. Lattice spacings and degree of texturing are determined by x-ray diffraction. Magnetic in-plane anisotropy is determined by longitudinal magneto-optic Kerr effect measurements. Our results show that an uniaxial in-plane magnetic anisotropy is induced with the hard magnetization direction parallel to the plane of incidence of the secondary Xe+ ions, and a (111) texture with an increased plane spacing of 0.5% is measured. The microstructure of the film and the magnitude of the anisotropy is sensitive to film thickness and flux ratio. For films prepared without secondary ion bombardment, the plane spacings correspond to those for bulk Ni, and isotropic magnetic behavior is observed.
Effect of Concurrent Ion Bombardment on Structure and Composition of Ion Sputter-Deposited Ni-Ti Thin Films
Authors: Grummon D. S. , Chang L.
Published: March 2011

Thin films of approximately equiatomic NiTi have been produced by ion beam sputtering, and by ion beam assisted deposition (IBAD), using 0.1 and 0.5 keV argon ions at fluences giving ion/atom arrival ratios (R-ratios) ranging between 0.26 and 2.21. Ion beam sputtering produced amorphous films which showed several percent titanium loss relative to the alloy target composition. Concurrent irradiation of the growing films with argon ions accentuated the titanium depletion, and R-ratios greater than approximately 1.4 at an assist-beam energy of 0.5keV produced resputtering rates that exceeded the deposition rate. Analysis of experiments with assist-beam energies of 0.5 keV produced a value of 1.75 for εTi/εNi, the ratio of sputteryields for titanium and nickel, in an amorphous alloy film at approximately 325K. Though data for 0.1 keV assist-beam irradiation could be interpreted to yield a similar value for εTi/εNi, resputtering at these energies displayed unexpected dependencies on R-ratio, and is apparently sensitive to the assist-beam incidence angle as well as the R-ratio. No evidence of crystallization of the films was found for the R-ratios examined. However, concurrent ion irradiation produced phenomenological evidence of short range ordering. Nanophase precipitates observed in TEM foils from films produced by ion beam assisted deposition, discovered in previous work and there identified as Ni3Ti, have been found in fact to be titanium nitride.
Effects of Nitrogen Ion Energy on the Growth Mode of WN Films Deposited by Reactive Ion Beam Sputtering
Authors: Benhocine A.H. , Meyer F. , Eizenberg M. , Bouchier D. , Kianfar S.
Published: March 2011

WN films were deposited on clean Si substrates by Reactive Ion Beam Sputtering in a UHV system. The growth mode of the films as a function of the nitrogen ion energy was investigated by in situ Auger Electron Spectrometry. The energy of the incident ions was varied from 250 eV to 3 keV. We observed a significant nitridation of the silicon at the very beginning of the deposition. This nitridation is more pronounced for the lower energy and is more reduced for 2 keV-ions. It seems to follow the trend of the film composition: 250 eV-ions and 2 keV-ions result in N-rich films (N/W≈1) and W-rich films (N/W≈0.5), respectively. All these results are discussed in terms of sputtering yield, backscattering and sticking coefficient and are explained by taking into account: first, the interaction between the incident ions and the target, and second, the interaction between the species emitted by the target and the growing film.
Thermal and Collisional Effects on the Intrinsic Stress in Nitride Layers Deposited by Ion-Beam Based Techniques
Authors: Djouadi M.A. , BOUCHIER D.
Published: March 2011

In IBAD BN and RIBSD Si3N4 layers deposited at room temperature, the internal stress can always be reduced below -1 GPa by a post-deposition annealing. When the deposition temperature is increased up to 600°C, the stress in Si3N4 layers is not significantly reduced and, in IBAD BN films, it is even greater than expected from the development of the thermal stress, which indicates that no relaxation of the stress occurs during deposition. This implies that the spatial extent of the ion peening effect may largely exceed the penetration depth of ions and of recoil atoms in the solid. In order to confirm this hypothesis, sequences of deposition/in situ annealing/deposition have been performed. In RIBSD films, the relaxation of the annealed sublayer can be observed. In IBAD films, the deposition of the upper layer results in an increase of the stress in the superficial zone of the annealed sublayer.
Investigation of titanium nitride films prepared by ion-beam-assisted deposition at high Ar+/Ti ratio
Authors: Hsieh J. H. , Bush D. E. , Erck R. A. , Fenske G. R. , Nichols F. A.
Published: March 2011

Titanium nitride films were prepared by reactive ion beam assisted deposition (RIBAD) with Ar+/Ti ratios ranging from 1.0 to 2.3. The compositions, phases and textures of these films were studied by AES and XRD as a function of Ar+/Ti ratio and nitrogen partial pressure. The results indicate that the IBAD titanium nitride films deposited at high Ar+/Ti ratio and low nitrogen partial pressure may have reduced nitrogen concentration, (200) preferred orientation, and possibly contain the Ti2N phase.