bluuebunny/crossref_metadata_2025 huggingface dataset:
Columnar and Subsurface Silicide Growth with Novel Molecular Beam Epitaxy Techniques
Authors: Fathauer Robert W. , George Thomas , Pike W. Thomas
Published: March 2011

Molecular beam epitaxy of silicides is conventionally carried out at temperatures ≤500°C, with stoichiometric Si:metal flux ratios or deposition of pure metal. We have found novel growth modes for epitaxial CoSi2 at high temperatures coupled with Si-rich flux ratios or low deposition rates. In the first of these modes, codeposition of metal and Si at 600-800°C with excess Si leads to the formation of epitaxial silicide columns surrounded by single-crystal Si. During the initial stages of the deposition, the excess Si grows homoepitaxially in between the silicide, which forms islands, so that the lateral growth of the islands is confined. Once a template layer is established by this process, columns of silicide form as a result of selective epitaxy of silicide on silicide and Si on Si. This growth process allows nanometer control over silicide particles in three dimensions. In the second of these modes, a columnar silicide seed layer is used as a template to nucleate subsurface growth of CoSi2. With a 100 nm Si layer covering CoSi2 seeds, Co deposited at 800°C and 0.01 nm/s diffuses down to grow on the buried seeds rather than nucleating surface silicide islands. For thicker Si caps or higher deposition rates, the surface concentration of Co exceeds the critical concentration for nucleation of islands, preventing this subsurface growth mode from occurring. Using this technique, single-crystal layers of CoSi2 buried under single-crystal Si caps have been grown.
Relaxed Si1−xGex Layers on Simox Avoiding a Lattice Mismatched Heterointerface
Authors: Holländer B. , Mantl S. , Butz R. , Michelsen W. , Dieker Ch.
Published: March 2011

For the first time, Si1 xGex layers on amorphous SiO 2 were produced by modification of the Si surface layer of a SIMOX wafer. We used two alternative methods. An additional Si1.. Gey layer was deposited epitaxially on a SIMOX wafer followed by rapid thermal annealing. Diffusional intermixing of the layers produced a homogeneous Si1 xGex layer on SiO 2. In a second attempt, Ge was implanted into the Si surface layer and thermally treated. In both cases epitaxial Si1 xGex layers on SiO2 with minimum yield values around 9% were obtained. Rutherford backscattering and cross sectional transmission electron microscopy were used to characterize the new structures.
The Influence of Surfactants on the Growth of Germanium Layers on Silicon Surfaces by MBE
Authors: Osten H.J. , Klatt J. , Lippert G. , Bugiel E. , Dietrich B.
Published: March 2011

Deliberate introduction of a surfactant can drastically influence the growth mode of germanium on silicon. Without a surfactant germanium growth proceeds in a typical Stranski-Krastanov mode. The system is minimizing its built-in energy by undergoing strain relaxation through a clustering mechanism (islanding). In all surfactant-mediated growth processes it was possible to obtain smooth layers without island formation. The influence of different ways for introducing the surfactant layer (at the interface between substrate and growing film, in the growing film below the critical Stranski-Krastanov thickness, or on top of the grown Ge film) will be presented. Especially in surfactant-controlled solid phase epitaxy (SPE) the smooth epitaxial germanium layer was obtained by passing through an island formation stage. These islands formed below 400 °C are of different structure than the ones formed without a surfactant. Possible mechanism for the “smoothing out” of islands developed in the beginning stage of surfactant-controlled SPE will be proposed. The island formation stage can be completely suppressed by depositing the surfactant on top of the amorphous Ge layer before increasing the temperature.
Modeling of Silicon Deposition Yield at Low Temperature by ArF Excimer Laser Photolysis of Disilane
Authors: Fowler B. , Lian S. , Krishnan S. , Li C. , Jung L. , Samara D. , Manna I. , Banerjee S.
Published: March 2011

Non-thermal Chemical Vapor Deposition (CVD) such as laser-enhanced photo-CVD of Si at low temperatures is important for Si-based heterostructures and doping superlattices. Growth kinetic models must be developed to allow these processes to be fully exploited. Intrinsic Si epitaxial layers were deposited at low substrate temperatures of 250-350ºC using the 193 nm output of an ArF excimer laser to directly dissociate Si2H6. The intrinsic film deposition rate can be described by a kinetic model that considers the gas phase reactions of the primary photolysis products and diffusion ofsilicon-bearing molecules to the growth surface. With the laser beam tangential to the substrate surface, growth rates as a function of beam-to-substrate distance have been characterized and indicate that very little gas phase reaction occurs for the dominant Si growth precursor. In order for intrinsic film deposition to result solely from Si2H6 photolysis products, a sticking coefficient ≥ 0.6 must be assigned to the dominant growth precursor in order to fit the observed yield of Si deposited in the films, indicating that the dominant growth precursor in 193 nm Si2H6 photolysis is perhaps H2SiSiH2.
Heteroepitaxial Growth of GexSi1−x Strained Layer on Si by RRH/VLP—CVD
Authors: Youdou Zheng , Rong Zhang , Liqun Hu , Shulin Gu , Ronghua Wang , Ping Han , Ruolian Jiang
Published: March 2011

A rapid radiant heating, very low pressure CVD (RRH/VLP—CVD) has been successfully applied to GexSi1−x strained layer epitaxy on Si using SiH4' GeH4' B2H6 and PH3 as reaction gases at low temperature ranging from 550 to 650ĉ for operation pressure around mTorr. High quality GexSi1−x/Si strained layer heterostructure and superlattice were fabricated and high electrically active in—situ boron doping in GexSi1−x epilayer was also successfully achieved.
On Microfaceting Instability of Pt(110) Under Catalytic Oxidation of Adsorbed Co
Authors: Papoular M.
Published: March 2011

As demonstrated by recent STM [1] and LEED [2] experiments the platinum (110) surface undergoes, at carbon monoxide submonolayer coverages, a phase transition from the 1 x 2 “missing-row” (reconstructed) state to the 1 x 1(bulk-like) state under specific temperature and partial-pressure conditions. The catalytic oxidation reaction CO + 1/2 → CO2 drives a microfaceting instability [3] [4] of the Pt(110) surface which ends up in a regular sawtooth profile with a period ≈ 200 Å, along the [110] direction.

We introduce the idea that the rather extensive Pt mass transport, as involved in the process, could be energetically assisted by the reaction itself. Energy and momentum-balance considerations lead us to expect an energy ≲ 0.5 eV to be transferrable to thesubstrate. This should efficiently contribute to initiating the “scraping”process that leads to the microfaceted pattern.

A simple model for nucleation and growth of facets is presented (see ref. 5), yielding characteristic times of order minutes (at T = 500 K), in fair agreement with experiment.

Independently of the structural/catalytic problem, adsorption of CO at submonolayer coverages on, e.g., Pt(110) might be of interest from a surfactantphysics point of view (see ref. 6 for a very recent study on layer-by-layer homoepitaxial metal growth).
Interdiffusion in MBE-Grown Symmetrically and Asymmetrically Strained Si/Si1−xGex Superlattices Investigated by Ion Scattering
Authors: Holländer B. , Butz R. , Mantl S.
Published: March 2011

The interdiffusion in MBE-grown Si/Si1−xGex superlattices was measured by Rutherford backscattering spectrometry. The superlattices consisted of 5 periods of 100 !A Si and 100 !A Si1−xGex layers with Ge concentrations, x, between 0.20 and 0.70. Both, asymmetrically strained superlattices, grown on Si(100), as well as symmetrically strained superlattices, grown on relaxed Si1−y.Gey buffer layers were investigated. Rapid thermal annealing in the temperature range between 900°C and 1125°C leads to significant interdiffusion between the individual layers, indicated by a decrease of the amplitudes of the backscattering spectra. Interdiffusion coefficients were deduced using a Fourier algorithm. The interdiffusion coefficients follow an Arrhenius law for a given Ge concentration. The interdiffusivity increases significantly with increasing Ge concentration.
A Study of Interdiffusion, Crystallinity, Strain and Thermal Stability of Si1−xGex/Si Created Using Pulsed Laser Induced Epitaxy (PLIE)
Authors: Kramer K.-Josef , Talwar S. , Weiner K. H. , Sigmon T. W.
Published: March 2011

Heteroepitaxy of Sil−xGex alloy layers on Si(100) and Si(111) has been achieved using Pulsed Laser Induced Epitaxy (PLIE). The energy of 1-50 pulses from a spatially homogenized XeCl excimer laser is used to melt a structure of electron beam evaporated Germanium on Silicon substrates. On Si(100) substrates alloys with Germanium fractions between 6 and 22% are investigated and exhibit very good crystallinity, as confirmed by MeV-Ion Channeling along the <100> - direction. Heteroepitaxy on Si(l11) yields similar results. MeV-Ion Channeling is also used to determine the level of strain in the layers. This is done by comparing angular yield curves around the <110> - direction for substrate and alloy layer. The obtained strain values are close to calculations for an ideally strained layer state. The strain is also measured for layers that have been subjected to different thermal cycles. As a result of this, predictions of feasibility for subsequent device fabrication can be made for the layers.
Differences in The Growth Mechanism of InxGa1−xAs on GaAs Studied by The Electrical Properties of Al0.3Ga0.7As/InxGa1−xAs Heterostructures (0.2 ≤ × ≤ 0.4)
Authors: Schweizer T. , Köhler K. , Ganser P. , Hiesinger P. , Rothemund W.
Published: March 2011

Lattice mismatched InxGa1−xAs layers with InAs mole fractions below 0.25 grow in a two dimensional growth mode on GaAs. If the thickness of these layers is beyond the critical layer thickness the strain relaxes through misfit dislocations. The misfit dislocation density in the <011> and <01-1> direction differs for n-type layers. This results in a highly anisotropic electron mobility for GaAs/InxGa1−xAs/Al0.3Ga0.7As inverted HEMT structures. A higher electron mobility in the < 011 > direction is measured in comparison to the <01-1> direction. The resistance ratio in the two perpendicular directions exceeds 105. For a three dimensional growth mode, the InxGa1−xAs layer shows interface roughness which degrades the transport properties of the normal Al0.3Ga0.7As/ InxGa1−xAs/ GaAs HEMT structures more than the inverted GaAs/InxGa1−xAs/ Al0.3Ga0.7As HEMT structures. For a three dimensional growth mode, an anisotropic electron mobility for Al0.3Ga0.7As/InxGal, As/GaAs HEMT structures is also observed. For these structures the highest electron mobility is measured in the < 01-1 > direction. This anisotropy could be explained by anisotropic growth rates in the <011> and < 01-1 > directions which results in growth islands with asymmetric extensions.
Selected-Area Epitaxy of CdTe on GaAs with A Cantilever Shadow Mask
Authors: Dhar N.K , Boyd P. , Martinka M. , Benson J.D. , Dinan J.H. , Iliadis A.A.
Published: March 2011

A cantilever shadow masking technique has been used for the first time to grow CdTe in recesses of GaAs wafers. The use of this technique eliminated the deleterious effects of side wall growth. Scanning electron microscopy, electron channeling, Auger spectroscopy and photoluminescence were used to characterize these structures. An application to planar monolithic infrared focal plane arrays is discussed.
Dopant Distribution and Electrical Characteristics of Boron-Doped Si1−xGex/Si p+/N Heterojunction Diodes Produced by Gas Immersion Laser Doping (GILD) / Pulsed Laser-Induced Epitaxy (PLIE)
Authors: Kramer K.-Josef , Ishida E. , Talwar S. , Weiner K. H. , Carey P. G. , McCarthy A. M. , Sigmon T. W.
Published: March 2011

Pulsed Laser-Induced Epitaxy / Gas Immersion Laser Doping is used to create borondoped heteroepitaxial p+/N Si1−xGex/Si layers and diodes. Borontriflouride is used as the gaseous dopant source. The mechanisms of heteroepitaxial layer growth of Si1−xGex using PLIE are described and impurity incorporation from the gas phase into the molten layer is investigated. Compared to other heteroepitaxial techniques, very different process parameters determine the growth. The energy fluence of the pulsed laser beam determines the melt depth and thus the layer thickness; Si and Ge intermix in the liquid phase, the diffusion of B dopant also depends on its diffusivity in the liquid phase. Boron incorporation is investigated as a function of laser energy fluence and number of laser pulses using SIMS and Hall-effect measurements. The dose of incorporated dopant is on the order of 1013cm−2 per pulse. The obtained boron profiles are flat except for a pile-up at the interface which is due to segregation. Boron and Germanium distribution are compared to turn-on voltage shifts obtained from p+/N Si1-xGex/Si heterojunction diodes fabricated with the technique. A two-step Laser process to independently control metallurgical and electrical junction depth of the diodes has been implemented. The selective nature of the epitaxial process is emphasized.
Initial Stage of InGaAs Growth on GaAs(100)
Authors: Gerthsen D. , Lentzen M. , Förster A.
Published: March 2011

The growth mode and the relaxation of MBE grown InxGa1-xiAs layers (0.13 ≦ x ≦ 1.0, nominal film thickness 5 nm) on GaAs(100) substrates with a lattice-parameter mismatch were investigated by transmission electron microscopy (TEM). The transition between two- and three-dimensional growth occurs at x ≈ 0.4. The three-dimensional growth mode for x ≥ 0.6 results in a wide spectrum of island sizes. In contrast to the two-dimensional growth mode, the strain state of a three-dimensionally growing layer is completely inhomogeneous because the relaxation of the strain is correlated with the island size. The reduction of elastic strain for islands is reasonably described by an energy balance model.
Strain Relief in SrF2 Epitaxial Films on Si(111) Substrates
Authors: Li Weidan , Taylor Anthony P. , Schowalter Leo J.
Published: March 2011

Molecular beam epitaxial (MBE) growth condition of SrF2 directly on Si(111) substrates has been optimized in terms of both Xmin and the surface morphology. Lattice distortion measurements were carried out with ion channeling along off-normal channeling directions in the strained layers grown at the optimal condition. The relationship of residual strain vs. film thickness for SrF2 on Si(111) was provided by the first time. The experimental data demonstrated a special thickness in this relation, at which the derivative of strain vs. film thickness changes its sign. This unique behavior was understood as the result of competition between the large lattice mismatch and the large thermal mismatch between SrF2 and Si.
Strain Relief in InxGa1−xAs/GaAs Multiple Layer Systems
Authors: Krishnamoorthy V. , Lin Y.W. , Park R.M.
Published: March 2011

In a recent paper[l] we presented the notion of a “critical composition” of InxGa1−xAs (x=0.18) which when exceeded results in threading dislocation evolution in InxGa1−xAs (x ≥ 0.18) material grown on GaAs. For InxGa1−xAs compositions below x=0.18, threading dislocation evolution occurs in the GaAs substrate material but not in the InxGa1−xAs epitaxial layer material, this phenomenon being attributed to a yield strength mismatch in favor of InxGa1−xAs at the epilayer growth temperature.

In this paper we describe recent results concerning an extension of this work to the study of strain relief in multiple layer systems. It was found that large x (x-0.5) InxGa1−xAs/GaAs layers can be grown having extremely low dislocation densities (<104/cm2 ) by step increasing the InxGa1−xAs composition at a series of InxGa1−xAs/InyGa1-yAs heterointerfaces such that a “critical composition difference” is not exceeded at each heterointerface. High resolution x-ray diffraction analysis was used to determine the extent of relaxation in each layer of these multilayer systems. As evidenced by cross-sectional TEM analysis, dislocations propagate only in the underlying material at each heterointerface for suitably selected compositional differences which results in the top InxGa1−xAs layer in such multiple layer schemes having a low dislocation density. It is to be noted that conventional methods for blocking dislocations such as strained layer superlattices and compositionally graded layers were not employed in our multilayer systems.
Tem Assessment of Different Mechanisms Contributing to Stress Relaxation in Strained InGaAs/InAlAs Systems
Authors: Peiro F. , Cornet A. , Morante J.R. , Clark S. A. , Williams R.H.
Published: March 2011

A study by Transmission Electron microscopy (TEM) of strained InGaAs/InAlAs systems on InP substrates is presented. The influence of the lattice mismatch, epilayer thickness and modulation of the lattice parameter on the morphology of the system is analyzed. A discussion of the strain relaxation mechanisms occurring for each growth morphology is also presented.
Strain Relaxation Via Interface Nucleation of Misfit Dislocations in Intermixing Layers
Authors: Park Hyo-Hoon , Lee Jung Kee , Lee El-Hang , Lee Jeong Yong , Hong Soon-Ku
Published: March 2011

The strain relaxation mechanism via the homogeneous nucleation of misfit dislocations from interface during interdiffusion in lattice-matched semiconductor heterostructures has been investigated. Transmission electron microscopy studies in intermixed GaInAsP/InP heterostructures revealed that the critical interdiffusion depth for the nucleation of 90° 1/6<112> partial dislocations from a tensile interface is much shallower than that of 60° 1/2<110> perfect dislocations from a compressive interface. A critical thickness model for the interface nucleation of these dislocations is developed as a modification of the classical surface nucleation'model.
AFM Study of Film Growth Kinetics in Heteroepitaxy
Authors: Tong William M. , Snyder Eric J. , Williams R. Stanley , Yanase Akihisa , Segawa Yusaburo , Anderson Mark S.
Published: March 2011

The growth of CuCl/CaF2 heterostructures has been studied with an atomic force microscope (AFM). We have grown by molecular beam epitaxy (MBE) CuCl thin films at various substrate temperatures and thicknesses on CaF2(111) substrates. AFM studies reveal that islanding is the dominant growth mechanism. We calculated the height-height correlation function, 〈lh(qt)|2〉, for each of our films and compared them to the predictions made by the Shadowing Growth Theory, a preexisting growth model that enabled us to extract the important kinetic parameter of surface diffusion length for the growth condition of each of the four films.
MBE Growth and Characterization of CdTe, ZnTe Epilayers and CdTe/ZnCdTe Superlattices on GaAs Substrates
Authors: Milokhin A.E. , Trofimov I.E. , Petrov M.V. , Balakirev F.F. , Kuzmin V.D. , Kalinin V.V. , Sidorov U.G.
Published: March 2011

Semiconductor heterostuctures ZnxCd1−xTe/CdTe were found to be of interest recently due to their potential practical usage. The reason for this is the beautiful variety of electrical heterostucture properties which arise from the strong influence of elastic deformation distribution. Thin epilayer films and superlattices ZnxCd1−xTe/CdTe were prepared on GaAs semi-isolator substrates by MBE technology with RHEED oscillation measurements of the deposited layers. X-ray measurements have shown high crystalline quality of the samples.

We have performed Raman scattering studies of ZnxZnxCd1−xTe/CdTe structures. The data obtained were interpreted as a proff of the pseudomorphous growth model. That is, ZnxCd1−xTe/CdTe SLS keeps the lattice constant of the buffer layer.
Experimental Measurement and Analysis of Microelectronics Application Polymer Materials Properties
Authors: Jeng Y.H. , Lii Mirng-Ji
Published: March 2011

A laser based surface scanning technique was utilized to measure the polyimide coated silicon wafer curvature resulting from thermal cycling and mismatch, Meanwhile, mechanical properties of polyimide thin film were characterized by DMA, TMA and tensile test. Based on the obtained material properties, A FEA model was developed to analyze the experimental results -reasonable correlation was obtained.

Similar approaches were taken one step further in the MCM silicon substrate curvature measurement. In a MCM package with silicon substrate, epoxy adhesive, and ceramic package, substrate warpage was developed in a thermal cycle due to thermal mismatch between the substrate and the package and coupling effect linked by epoxy adhesive. Three different substrate curvature measurement techniques were applied to identify the substrate curvature and epoxy thin film properties were also well characterized. A 3D FEA model incorporating with the epoxy material properties was developed to analyze the substrate warpage and investigate an optimal package design.
X-Ray Determination of Residual Stresses of Encapsulated Thin Aluminum Lines
Authors: Radler M. J. , Crowder C.E. , Shaffer E.O. , Townsend P.H.
Published: March 2011

Differences in thermal expansion coefficients between the dielectric layers, the substrate, the metallizations, and the circuit chips generate complex residual stress fields within multichip module (MCM) packages. For example, encapsulated interconnect lines in a typical MCM are under triaxial stress. Quantifying the triaxial stress is needed to understand critical issues such as stress relaxation, stress-induced voiding, as well as providing benchmarks for finite element calculations. Employing a novel sample design, triaxial residual stresses have been determined in thin aluminum lines encapsulated in benzocyclobutene dielectric layers by x-ray diffraction techniques. Significant differences are observed in the stresses if the lines are deposited on the Si substrate or on intervening polymer layers. The stress level is constant with intervening polymer layer thickness. The results suggest a fundamental difference between the strain transfer across the silicon oxide-aluminum interface relative to the silicon oxide-polymer interface.
Effects of Electronics Assembly Processes on Benzotriazoletreated Printed Wiring Board Copper Surfaces.
Authors: Evans Howard E. , Partridge Julian P. , Miller Allen G. , Jackson Marc W.
Published: March 2011

The performance and reliability of personal computers, workstations and other electronic products depend on the effective soldering of electronic components to printed wiring oards (PWBs). The copper surfaces of PWBs are frequently treated with benzotriazole (or similar organic complexes) to preserve solderability by preventing copper oxide formation. However, new assembly process techniques and more complex processes may degrade protective organo-copper surface complexes and allow copper oxidation to occur, thus inhibiting subsequent solder operations. This study uses Auger electron spectroscopy (AES) in conjunction with meniscograph wettability results to determine the effects of processing conditions on the solderability of PWB surfaces. Effects are characterized for aging up to 19 months; Infrared (IR) reflow in air and nitrogen; cleaning; and temperature cycles associated with adhesive or encapsulant cure. Surface compositions, oxide thicknesses, and solderability measurements are correlated to the above process steps. For example, IR reflow in air increases oxide thickness from ∼10 Å to ∼150Å (relative to sputtering rates in Ta2O5 with an attendant increase in the meniscograph time-to-neutral-buoyancy from <2 seconds to >10 seconds, relative to unprocessed PWBs. Such fundamental information serves as an invaluable complement to standard phenomenological observations of defective solder joints, and can aid in guiding processing decisions for improved yield and reliability.
Properties and Microstructure of Mullite-Glass Ceramics for Multilayer Ceramic Substrates
Authors: Ushifusa N. , Sakamoto K. , Ogihara S. , Fujita T.
Published: March 2011

Mullite (3Al2O3·2SiO2) has a low thermal expansion coefficient and a low dielectric constant making it a favorable material for substrate applications. Sintering of pure mullite ceramics is difficult, however, even above 1700°C. Thus, mullite-glass ceramics containing glass additives (Al2O3-MgO-SiO2 glass) which could be sintered at about 1600°;C were fabricated and their properties were investigated. The ternary system diagram of Al2O3-MgO-SiO2 shows that high SiO2 content glass depos its cristobalite at 200 to 270°C, which causes a substantial volume change, resulting in ceramic substrate cracking. Therefore it is particularly important to prevent crystallization of cristobalite from the glass phase in mullite-glass ceramics. The glass phase softens or partially fuses above 1600°C, and cristobalite formation in the glass phase occurs in the cooling process during firing. In order to obtain good substrates of mullite-glass ceramics, a higher temperature for sintering and faster cooling rate after firing are preferable. Analytical results by X-ray, SEM and EPMA show that mullite dissolves in the glass phase at a higher sintering temperature and more mullite crystallizes in the cooling process with a lower rate. The content of Al2O3 in the glass phase, therefore, increases with the increased sintering temperature and cooling rate, which may restrain crystallization of cristobalite. By adjusting of the composition of mullite and glass phase, mullite-glass ceramics with low dielectric constant (5.9), thermal expansion coefficient (3.5×10−6/°C) close to that of silicon chips, and high bending strength (210MPa) have been developed. These substrates made of mullite-glass ceramics are suitable for mounting silicon devices of computer processors.
Passive Polymeric Waveguide Materials for Optical Interconnects
Authors: Hutcheson Lynn D. , Arrington John P. , Powell Stephen F.
Published: March 2011

The need for higher bandwidth interconnect schemes to relieve the communications bottleneck caused by the ever increasing speeds of discreet electronic devices has led to a renewed interest in thin film optical waveguides as interconnect media. This paper reviews some of the polymeric materials that have been investigated for use as thin film passive optical waveguides over the past ten years. Several proposed applications for these waveguides are presented and the specific material requirements of these applications are discussed. The strengths and weaknesses of specific polymeric materials are considered in view of these requirements. While reference is made to a variety of polymers that have been considered for these applications, emphasis is placed on the relative merits of polyimide and acrylate polymer based systems.
New Patternable Materials for Electronic Packaging
Authors: Popall Michael , Kappel Jürgen , Pilz Monika , Schulz Jochen
Published: March 2011

New inorganic-organic copolymers (ORMOCERs – ORganically MOdified CERamics) were developed as protective coatings for electronic and optical devices, as patternable insulation and passivation layers for electronics, e. g. MCM's, and as possible interconnects and waveguides for micro optics.

Depending on the chemical composition and the processing parameters, their important features are low permittivity constants (eR ≤ 3.2), high bulk resistance (RD > 1016 Ωcm), high dielectric strength (ED ≤ 400 V/μm), refractive index around 1.48, optical transparency in the range of 400 – 1300 nm, and good adhesion to numerous substrates, such as Al2O3, glass, silicon, copper, aluminum, steel, polyimides, polyesters and epoxides.

The materials can be applied using standard technology. They are patterned by laser direct writing, photolithographic, screen printing or embossing technologies.
Process Dependence of Microstructure and Properties of Sintered Aluminum Nitride for Electronic Packaging
Authors: Dutta I. , Mitra S. , Cooper J.
Published: March 2011

The development of secondary phases due to additions of Y2O3 during sintering of aluminum nitride was studied. Depending on the heat treatment conditions and the amount of Y2O3 added, different proportions of AlYO3, Al5Y3O12 and Al2Y4O9 were found at the grain boundaries. Temperatures ≳1850°C also resulted in loss of Y2O3 and/or Y-aluminate, yielding some γAl2O3. The mechanical properties and the thermal conductivity of the sintered product were observed to be dependent on the grain boundary phase constitution and hence the specific heat treatment condition.
Enhancing the Interfacial Bond Strength of Lignocellulosic Fiber Dispersed in Synthetic Polymer Matrices
Authors: Simonsen John , Rials Tim
Published: March 2011

Wood-plastic composites have been produced utilizing a phenol-formaldehyde pretreatment of the wood. The use of additives to cross link the plastics and increase the interfacial bond between the wood and plastic were also investigated. These preliminary results suggest that pretreatment of the wood with a thermosetting resin may increase the stiffness of the composite. The use of an octylphenol as a plastic compatabilizer did not reliably increase stiffness in this system, although additional study is warranted. An interaction between the wood and the polystyrene in the plastic mixture may be indicated.
Transition Time for the Paper Industry
Authors: Driscoll William V.
Published: March 2011

Recycling is not new to the paper industry. A lot of work was done during World War II, but following the war, the paper industry, for economic and technical reasons, moved away from recycling. The reasons are obvious. We have the trees, and we have them in great profusion. However, recycling came back to us with a vengeance along with the solid waste problem in the late ‘60’s and early ‘70’s. It was a big issue then largely in the federal, state and local government jurisdictions, but the general public did not really perceive it as a major issue until, Senator Gary Hart attempted to levy a tax on virgin materials in 1978. After that it went back on the back burner. It came back again in 1987 and 1988, when people started to pay more attention to the environment and when costs for waste disposal began increasing.
Recycling Lignin for Engineering Applications
Authors: Feldman D. , Banu D. , Lacasse M. , Wang J.
Published: March 2011

Lignin, a complex natural polymer produced by all vascular terrestrial plants is second in abundance only to cellulose and is the matrix holding plant fibres together. Lignins are recovered mainly as byproducts from woodpulping processes with about 100 million tons produced annually worldwide.

Large volume uses for lignin byproduct other than for generation of energy (kraft process) are most likely to be in materials applications.

In the last decades many studies aimed to the recycling of different lignins (sulfite, kraft, organosolv, steam exploded, hydrolytic, etc.) in polymeric systems based on thermoplastics, thermosettings, elastomers, adhesives, sealants, etc.

Among all the technical lignins, sulfate lignins are chemically the most reactive and are therefore used to modify polymers. The oldest and the most familiar application of lignin as a component of polymeric materials involves the reinforcement of rubber. Multicomponent materials can be created by combination with other macromolecules like polyethylene, polypropylene, or poly(vinyl alcohol) to produce polyblends, block copolymers or interpenetrating polymer networks.

The present communication will try to present such examples of polymeric systems based on recycled lignin, and synthetic polymers such as: polyurethane, epoxy, acrylics, silicones.
Structural Changes in Cellulose During Papermaking and Recycling
Authors: Atalla Rajai H.
Published: March 2011

Recent advances in understanding the structure of cellulose are used as the basis for analyzing the structural changes that occur in pulp fibers during papermaking, particularly in the drying stage. These changes are responsible for the degradation of papermaking properties, and they must be reversed during recycling if the maximum papermaking potential of the virgin fibers is to be recovered. A number of studies have assessed the structural transformations that can occur in cellulosic fibers upon exposure to elevated temperatures. The researchers have invariably observed that the changes occur at the secondary and tertiary levels of structure, the levels that can have significant effects on the properties of fibers. In addition, some studies have focused specifically on the structural effects of recycling; clear correlations of structural change with changes in paper characteristics have been reported. The results of the various studies point to directions for further investigations into enhancing the recovery of papermaking value from recycled fibers.
Recycling of Paper and Bulk Properties of Recycled Fiber
Authors: Silveri Luigi
Published: March 2011

There are several clear trends in the recycling of paper. Firstly, the amount of recycle is increasing and will continue to do so. Secondly, recycled fiber is being used in greater quantities. Finally the recycled fiber is being introduced into higher quality paper grades which previously did not have any recycled content.

This means that on the one hand the quality of the recycled furnish is deteriorating in terms of contaminant level and strength, while on the other hand there is an increased expectation in terms of properties of the end product, the recycled fiber.

The major unit operations of recycling and general principles of system design are reviewed, methods for enhancing these properties and limits which can be achieved are discussed.
Recycling Bleach Technologies
Authors: Minor James L.
Published: March 2011

When faced with bleaching recycled fibers, the technologist must consider the usual factors associated with the bleaching of virgin fibers plus additional factors introduced by recycling. The lignin content of the furnish and the products to be made determine whether delignifying or lignin-preserving agents are to be used. Factors introduced by recycling include mixed lignin contents, dyes, residual ink particles and carrier chemicals, contaminants, color reversion, and hornification (which affects accessibility of chromophores to bleaching reagents). In addition, the technologist must be concerned with the environmental impact of the bleaching operation.

Dithionite and formamidine sulfinic acid are effective lignin-preserving reductive bleaching agents for recycled fibers. Hydrogen peroxide is an effective lignin-preserving oxidative agent, but heavy metals and enzymes catalyze its decomposition. Chelating agents have an important role in decreasing metal content. For some delignification and effective removal of organic chromophores, oxygen and ozone show promise. Research on the use of oxygen-based oxidative bleaching agents is intense because of their favorable environmental attributes.
Filler Pigments Designed for Recyclability
Authors: Passaretti June D. , Young Trudy D. , Herman Mick J. , Evans D. Bruce
Published: March 2011

This paper discusses the use of a new rhombohedral precipitated calcium carbonate (PCC) morphology and existing PCC morphologies in wood free, wood containing, and recycled paper. The new material has properties that mimic TiO2 with respect to morphology, particle size, particle size distribution, and surface area. TiO2 is widely used by the paper industry as a functional filler for opacity and brightness. The new PCC rhombohedral morphology can be used in place of TiO2 for many applications greatly reducing the cost of production.

The physical properties of the new PCC morphology as well as application as a paper filling pigment will be discussed.
Estimation of Fiber-Matrix Interfacial Shear Strengths in Lignocellulosic-Thermoplastic Composites
Authors: Sanadi A. R. , Rowell R. M. , Young R. A.
Published: March 2011

The interaction and adhesion between fibers and the matrix in composite materials have a significant influence on the properties of the fiber composite. It is, therefore, of utmost importance to be able to evaluate the properties of the interface/ interphase of the fiber-matrix for optimization of the properties of the composites. Techniques that are currently used to evaluate the properties of this region will be discussed with special attention to lignocellulosicthermoplastic composites. Sample preparation, applicability, problems and advantages of each technique will be highlighted. Results obtained at our laboratory for wood-low molecular weight polyethylene systems using the pull-out test will be discussed.
The National Gallery at War
Authors: Saunders David
Published: March 2011

With the outbreak of the First World War in 1914, Britain found herself involved in a European war for the first time in nearly a century. The National Gallery had thus been immune to the possibility of attack by hostile forces, although it is interesting to note that when war was declared, the Gallery had only recently reopened to the public following an attack on a Bellini by a suffragette.
Evaluation of the Effectiveness and the Potential Damage of Cleaning Methods for the Restoration of Stained Glass Windows
Authors: RÖMICH Hannelore , Fuchs Dieter R.
Published: March 2011

A comparative study on the effects of restorational cleaning methods for stained glass windows was carried out using corrosion sensitive model glasses. Typical deterioration phenomena like crusting, leaching and microcracking could be simulated using accelerated weathering in climatic test cabinets. The sensibilization of such samples caused by cleaning was assessed by infrared spectroscopy and light microscopy after re-weathering.
Status Report: Assessment of Cultural Losses Suffered by American Aleuts During World War II
Authors: Smith Barbara Sweetland
Published: March 2011

In 1988, the U. S. Congress provided $1.4 million to six Aleut communities in Alaska as restitution for damage done to their churches by U. S. forces stationed in the Aleutians during World War II. The residents of these communities had been forcibly evacuated and interned for up to three years in camps in southeast Alaska where many died. At the request of the Aleuts, restitution to the Orthodox churches was given a special place in the U. S. decision to make reparations. The Aleutian/Pribilof Islands Association, a non-profit organization, has been charged by Congress with assessing the damage and estimating the cost of restoration. The assessment project, begun in November 1991, has utilized the expertise of an architect and art conservator to examine structures and church furnishings of these churches and has reached some preliminary conclusions: 1) The stress of travel for those icons and liturgical vessels which accompanied the evacuees was significant and damage related to that travel is evident today; 2) The churches themselves were often targets of vandalism and looting by the American troops; 3) the churches were left without regular maintenance in the harsh climate of the Aleutians for three years; 4) the Aleuts were destitute on their return and could not restore the buildings to their former condition; 5) the results of makeshift repairs in the immediate post-war era are evident today in a general state of deterioriation. The final report to Congress on this project is due in the Spring 1993.
Understanding Art Through Technical Analysis Inferences From Pigment Identification
Authors: Berrie Barbara H.
Published: March 2011

Pigment identification and technical analysis of works of art provide the historian and conservator with information that allows a new view of an object. The methods the analyst chooses depends on the nature of the sample and the materials and method expected for the age of the object being examined. Several analytical methods are used frequently in the museum field with great success; these include x-ray fluorescence spectroscopy, x-ray powder diffraction methods and optical microscopy. Results from the analysis of pigments in paintings by Derain, Beckmann, El Greco, G. David, and Gentileschi are given. The results include discovery of an unpublished formulation of cobalt violet, example of the use of particle size to change the appearance of color, and the use of x-ray fluorescence to determine artists' palettes without removing samples from the works of art. The study of the El Greco and the Gentileschi show how technical investigations can complement art historical research.
Non-Destructive Spectroscopic Investigations on Paintings Using Optical Fibers
Authors: Bacci M. , Baronti S. , Casini A. , Lotti F. , Picollo M. , Casazza O.
Published: March 2011

The main objective of our research is the development of totally non-destructive methodologies for the investigation of art works. We propose the use of fiber optic reflectance spectroscopy (FORS) in the visible and near-infrared region as a tool for the identification of the pigments used in painting. We have considered several representative inorganic artists' pigments (mainly till the Renaissance period); powder X-ray diffractograms and diffuse reflectance spectra in the visible, near-, middle- and far-infrared range were recorded for pure pigments. Then we prepared suitable samples with the same pigments using fresco, tempera and oil techniques. The visible and near-infrared spectra of these samples were recorded using an optical fiber spectrum analyzer; color analysis (chromaticity, dominant wavelength and purity) was also performed. The obtained results were used in the interpretation of the spectra obtained from some paintings collected in the Uffizi Gallery, Florence (Giotto and Luca Signorelli). The pointwise information obtained by FORS analysis was also used to calibrate and tune an image spectroscopy system, based on sequences of band-pass filtered images in the near infrared range.
Application of Surface and Bulk Analytical Techniques for the Study of Iron Metallurgy Slags at Tell Afis (N-W Syria)
Authors: Ingo G.M. , Scoppio L. , Mazzoni S. , Mattogno G. , Scandurra A.
Published: March 2011

By a combined use of small area X-ray photoelectron spectroscopy (SA-XPS),X-ray induced Auger electron spectroscopy (XAES), scanning electron microscopy (SEM) and electron probe for microanalysis (EPMA), the microchemistry of a group of slags from Tell Afis (North-Western Syria), dating back to Iron Age II (750 B.C.), have investigated. The results show and localize the presence of different iron oxides and hydroxides as well of various glassy and crystalline silicates, whose chemical structure and morphology have determined.
The Protection of National Treasures at the British Museum During the First and Second World Wars
Authors: Caygill Marjorie L.
Published: March 2011

With the emergence in the 20th century of long-range methods of destruction, museums and galleries have had to develop appropriate measures to protect their collections. The British Museum first took such measures on site in 1914 and followed this by evacuating some of its most valuable objects in 1918. Similar procedures were followed in the Second World War and, despite major damage to the building, no significant items (apart from books) were lost.
Investigation of Decorative Coating on Kongo Ceramics Using U. V. Light and Ftir Analysis
Authors: Hexter Madeleine R. , Hopwood Walter R.
Published: March 2011

The ethnographic and art historical literature reports the use of vegetable resins on Central African ceramics, specifically those made by the Kongo peoples. The purpose of this investigation was to develop a procedure for determining the nature of decorative coatings generally on African ceramics. The investigation focused on a group of Kongo ceramics. FTIR spectra of known resins were obtained and compared with several samples taken from Kongo ceramics. The ceramics were also examined under U.V. light. This paper discusses the results of the examinations and analysis.
Protection of Archival Record From Pollutants the Diffusion of SO2 Through Archival Boxboard
Authors: Guttman Charles M. , Jewett Kenneth L.
Published: March 2011

The diffusion constants of sulfur dioxide in boxboards, commonly used to store archival documents, have been measured. For the most common boxes used by National Archives and Record Administration a diffusion constant of about 0.001 cm2 / sec was determined independent of gas concentration. These results are discussed in terms of a model of the microenvironment provided by these boxboards as used in archival storage.
Further Study of the Process of Technological Evolution of Ancient Chinese Pottery and Porcelain
Authors: Jiazhi Li , Hongjie Luo , Liming Gao
Published: March 2011

The chemical compositions and firing temperatures of seventy-four stamped pottery and proto-porcelain fragments which were excavated from Jiangxi, Zhejiang, Henan and Fujian were studied. Their chemical compositions, together with a database of more than 600 pottery and porcelain bodies and 100 protoporcelain and porcelain glazes previously investigated, were processed and evaluated by correspondence analysis. Their firing temperatures and those of more than 200 pottery and porcelain samples were compared as well. The results of this investigation yield a more objective and comprehensive view of the process of technological evolution of ancient Chinese pottery and porcelain than heretofore possible. The place of stamped pottery and proto-porcelain in the evolution process is better understood, and the differences between the patterns of continuity and change in the north and the south of China is further discussed in this paper.
Cleaning with Laser Radiation on Istria Stone
Authors: Maravelaki Pagona , Biscontin G. , Zendri E. , Polloni R. , Cecchetti W.
Published: March 2011

Cleaning treatments necessary for stone conservation consist of removing compounds that were superimposed on the original material by means of physico-chemical processes.,The purpose of this work is to identify the transformation of stone surface by the LASER treatment. Cleaning test on Istria stone with LASER radiation at different energies and in different regimes have been performed. The depletion of the original material has been evaluated by means of SEM microprobe analyses.
Intercalated Two-Dimensional Ceramic Nanocomposites
Authors: Giannelis E.P. , Mehrotra V. , Tse O. , Vaia R.A. , Sung T.-C.
Published: March 2011

New generations of polymer-ceramic nanocomposites are being developed by intercalation of layered solids. Synthetic approaches include intercalative polymerization, direct polymer intercalation and molecular dispersion of the host layers in the polymer matrix. The unique physical and mechanical properties of the hybrids are attributed to the molecular dispersion and the synergism between the individual components.
Mass Spectrometric Study of ECR Microwave Plasma Etching of Si3N4 Films
Authors: Jin Ming , Kao Kwan C.
Published: March 2011

The effects of ion impinging energy on the etching of Si3N4 films in an electron cyclotron resonance (ECR) microwave plasma etching system have been studied. An alternating frequency (10 MHz) bias voltage was used to control the ion impinging energy. The experimental results show that the etching rate in the initial period (less than 3 min) of the etching process is noticeably lower than that in the following period for bias voltage Va > 10 V. The length of the initial period depends on the plasma density. The etching rate in the following period depends on the bias voltage. But the above dependence disappears for Va < 10V. It is found that the surface oxide contribution to the bias effects is negligible. The mass spectrometric measurement of the transient of the etching product SiF4 confirms these bias effects. The effects may be attributed to the ion radiation damage to the subregion lattice even at low ion energies.