bluuebunny/crossref_metadata_2025 huggingface dataset:
A Complexed Precursor Approach To The Synthesis Of Ternary Transition Metal Nitrides
Authors: Weil K. S. , Kumta P. N.
Published: April 2011

A new chemical synthesis approach has been developed in which ternary transition metal nitride powders are synthesized from hydrolyzed alkanoamine complexed precursors. In this technique, two different metal chlorides are dissolved in a common solvent such as acetonitrile, then reacted with ethanolamine to form a highly viscous solution which settles out of the solvent phase. Simultaneous evaporation of the solvent and forced hydrolysis of the remaining liquid results in the formation of a precipitate which can be filtered and dried. The precursor is heat treated in ammonia to form the corresponding ternary nitride. The approach has been successfully used to synthesize Ni3Mo3N, FeWN2, and Ti3AlN powders, each of which have been characterized using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM).
Combustion synthesis of nanosized SiCxNy powders
Authors: Keil D. G. , Calcote H. F. , Gill R. J.
Published: April 2011

Silane/acetylene/ammonia flames were used to produce fine powders of composition SiCxNy The experiments were conducted in a spherical reactor at 1 atmosphere total pressure with spark ignition in the center of the chamber. The composition was determined from complete quantitative analysis of the gas products and elemental analysis of the solids. IR spectra indicate little bound hydrogen in the powders, but oxygen was adsorbed on the high surface area powders (60–80 m2/g, N2 BET). The experimental stoichiometries of the nascent powders can be represented as mixtures with weight ratios of Si3N4/SiC ranging from about 0.2 to 2, and variable amounts of excess carbon or silicon. The powders, from TEM, consist of chains of nearly symmetrical particles with diameters around 40 nm. Helium pycnometry densities in the range of 2.9 to 3.2 g/cc are consistent with the theoretical densities for the Si3N4/SiC stoichiometries. The powders were amorphous or nanocrystalline, from X-ray diffraction (Cu Kα). Annealing in argon at 1773 K for 8 h resulted in preferential growth of crystalline SiC domains.
Recent Progress in Gan Based Field Effect Transistors
Authors: Khan M. A. , Chen Q. , Sun C. J. , Yang J. W. , Shur M. S.
Published: April 2011

Most types of GaN based Field Effect Transistors – MESFETs, MISFETs, Heterostructure FETs (HFETs), and Doped Channel HFETs (DC-HFETs) have demonstrated a good performance at both room temperature and elevated temperatures. The DC-HFETs demonstrated the best direct current and microwave characteristics among all wide band gap semiconductor devices because of excellent transport properties of two dimensional electron gas at the AlGaN/GaN heterointerface and a large sheet carrier concentration in the device channel. Other advantages of GaN-based materials for FET applications include a very high breakdown field, a very high saturation field, a high peak velocity, a large conduction and valence band discontinuities at the AlN-GaN heterointerface, and a reasonable thermal conductivity (comparable to that of Si). In this paper, we review our recent results obtained for different types of GaN-based transistors.
Effects of Additives on the Stacking Fault Formation During Synthesis of β-Sic Particles by Carbothermal Reduction
Authors: Seo W. S. , Koumoto K.
Published: April 2011

Through the systematic addition of B, and Fe, additive effects on the stacking fault formation and the morphology of the formed particles during synthetic reaction of β-SiC were investigated in the present study. Stacking fault density of the synthesized powders decreased with increasing content of added B and Fe. Whisker content of the synthesized powders and formation mechanism of whiskers are the most closely related to the stacking fault density.
Cubic SiC the Forgotten Polytype
Authors: Jayatirtha H. N. , Spencer M. G.
Published: April 2011

The two most common and most studied forms of SiC are 6H-SiC and 3C-SiC. The 3C-SiC, or cubic modification shares the zincblend lattice structure with other well developed semiconductor materials, such as GaAs and InP. We have grown thick 3C-SiC by the sublimation method. Our results show that it is possible to maintain the 3C polytype even at growth temperatures of 2000°C. Using the sublimation technique we have obtained growth rates as high as 130 microns/hr.
Emissivity of Silicon Carbide Composites as a Function of Temperature and Microstructure
Authors: Sun Ming , Lloyd Isabel K.
Published: April 2011

Spectral emissivity normal to the sample surface was investigated as a potential intelligent control parameter for the manufacture of SiC fiber reinforced SiC composites by chemical vapor infiltration (CVI) and microwave assisted CVI. Results indicated that at temperatures between 600 and 1000°C and wavelengths between 1500 and 2100 nm emissivity was sensitive to the sample porosity. It also appeared to be sensitive to the thickness of the oxide layer on the composites. The emissivity was not very sensitive to temperature in this region. It was concluded that emissivity is promising as a probe of density during manufacturing. It may also be useful as a probe of oxide layer formation.
From Precursors to Non-Oxide Ceramics: Pyrolytic Mechanisms Studied by NMR
Authors: Sigmund W. M. , Feike M. , Spiess H. W. , Aldinger F.
Published: April 2011

The pyrolysis of a poly ethylsilazane was studied using a CO2-laser beam heated solid state MAS-NMR probe head. Chemical structures of the intermediate stages could be identified. The analogy of the pyrolysis evolution for the following two different methods could be shown: A) in an inert gas furnace conventionally prepared and B) laser irradiated in the NMR probe head under magic-angle spinning (MAS) conditions. Samples prepared by method A were studied by 29Si MAS-NMR and samples prepared by method B were studied with an appropriate cross polarization time by 29Si CP-MAS-NMR. Both experiments showed the same mechanisms for the pyrolysis as the polymer is transformed into a Si3N4/C ceramic.
New Method for Bonding Poly(Ethylene Oxide) PEO to Surfaces
Authors: Allgor S. J. S. , Merrill E.W.
Published: April 2011

A new method has been developed for the covalent attachment of poly(ethylene oxide) to various polymeric surfaces for use in biomedical applications. Methacrylic acid (MA) monomer was first grafted to low-density polyethylene (LDPE) or polystyrene (PS) sheets by placing them in a solution of 10–20% (v/v) methacrylic acid in water followed by electron beam irradiation of 2–4 megarads. The methacrylic acid was grafted to the surface and polymerized, resulting in the polymer surface being extremely hydrophilic. The MA-treated samples were placed in a solution of PEO in water (MW 8000 – lx106 g/mol, concentration 0.05–15 % w/v), where the PEO strongly hydrogen bonds to the MA on the surface. The pieces were either rinsed with water (monolayer formation) or drained of excess solution (multilayer formation), then placed under the electron beam for a dose of 2 megarads to graft the PEO to the MA-treated surface. The grafted PEO was stable on the surface, unable to be removed despite extensive washing with water, soaking in basic solution (which would break the hydrogen bonding of the PEO with the acid), or scraping of excess hydrogel from the surface. The monolayer thickness was found to have no dependence on the molecular weight or concentration of the PEO in solution, nor did it have any dependence on the time that the MA-treated samples were soaking in the PEO solution before the second irradiation. This indicates that the PEO molecules immediately lie flat on the surface with few loops or tails, with no exchange taking place after the initial adsorption. All surfaces were analyzed using X-ray photoelectron spectroscopy (XPS), with high resolution carbon Is scans being the principle means of MA and PEO detection in the top 50 angstroms of the surface.
Spatial Ordering of As Clusters Due to Indium Delta-Doping of LTMBE GaAs
Authors: Bert N. A. , Chaldyshev V. V. , Faleev N. N. , Kunitsyn A. E. , Tret'yakov V. V. , Lubyshev D. I. , Preobrazhenskii V. V. , Semyagin B R.
Published: April 2011

We have shown that two-dimensional layers of arsenic nano-clusters separated by cluster-free GaAs matrix can be formed using indium delta-doping of GaAs films grown by molecular beam epitaxy at low (200°C) temperature. Spatially ordered structures of As clusters have been obtained in the epitaxial LT GaAs films doped with Si donors, Be acceptors and undoped as well.
Optical Study of Carrier Transfer in Strain-induced Quantum Dots
Authors: Gu Yitong , Sturge M. D. , Kash K. , Gaag B. P. Van der , Gozdz A. S. , Florez L. T. , Harbison J. P.
Published: April 2011

We have studied excitation transfer from the host quantum well to strain-confined quantum dots. We find that there is a long-lived intermediate state acting as a reservoir, holding the excitation before it is thermally activated over a barrier to reach the quantum dot. The barrier height increases monotonically with dot size.
Compositional Ordering in GalnP for Heterostructure Formation
Authors: Stringfellow G. B. , Su L. C. , Murata H. , Chun Y. S. , Ho I. H. , Hsu T. C. , Hosokawa Y.
Published: April 2011

Compositional ordering is observed in essentially all IIIN semiconductor alloys. The mechanism leading to the specific ordered structures formed is only now beginning to be understood. It is intimately related to the atomic-scale physical processes occurring on the surface during epitaxial growth, specifically surface reconstruction and the attachment of atoms at steps. This paper will emphasize the use of surface analytic techniques to better understand the ordering processes during organometallic vapor phase epitaxial growth of GalnP. Surface photo absorption has been used to determine, for the first time, that the surface reconstruction is (2×4)-like during growth of GalnP with Cu-Pt ordering. By increasing the growth temperature and/or decreasing the V/Ill ratio the concentration of phosphorus dimers characteristic of the (2×4) structure is observed to decrease in tandem with a decrease in the degree of order measured in the epitaxial layers. This suggests that formation of the (2×4) reconstruction is necessary for formation of the Cu-Pt ordered structure.

Atomic force microscopy was used to examine the step structure. For exactly (001)-oriented substrates, growth at low V/Ill ratios produces islands surrounded by single monolayer steps. Increasing the V/Ill ratio leads to the formation of bilayer steps approximately 6 Å high. A similar change in the structure of steps is observed in the vicinal regions for substrates misoriented to produce [110] steps. This phenomenon is interpreted in terms of the stabilization, at high V/Ill ratios, of the (2×2) reconstruction on the (111)B regions of the bilayer steps. This may also have an effect on formation of the Cu-Pt ordered structure.

By changing the substrate temperature or the input partial pressure of the phosphorus precursor, the degree of order and, hence, the bandgap energy of GalnP, can be modulated during growth. This has allowed the production of a variety of single and double heterostructures. The heterostructures produced by changing the temperature from 740 to 620°C and from 620 to 520°C are abrupt. The heterostructures formed by changing the phosphine flow rate are not. The ordered structure in the lower layer persists into the upper layer. This may be an indication of the importance of the step structure.
Structural Characterization of Composition-Modulated ZnSel-xTex Epitaxial Films
Authors: Ahrenkiel S. P. , Bode M. H. , Al-Jassim M. M. , Luo H. , Xin S. H. , Furdyna J. K.
Published: April 2011

We examine the microstructure of short-period (14–31 Å) composition modulations in epitaxial ZnSel-xTex (x@0.5) films grown by molecular-beam epitaxy (MBE) on vicinal (001) GaAs. Transmission electron microscope (TEM) images of cross-sections reveal highly-periodic contrast along the growth direction throughout the full thicknesses of the films (over 2 μm) that corresponds to a nearly sinusoidal variation between Se- and Te-rich compositions. Growth of ZnSe1-xTex at 285°C on substrates tilted 4° toward [1111 maximizes the strength and regularity of the modulation. Using dynamical electron-diffraction simulations, we estimate a modulation amplitude of r@0.184(7) in a sample showing strong modulation. We assume a small amplitude of strain modulation to fit the experimental data.
The Formation of Radiative Defects at GaAs/GaInP Interface
Authors: Uchida Kazuo , Arai Takayuki , Matsumoto Koh
Published: April 2011

We report the optical characteristics of 100 A˚ thick GaAs/Ga0.521n0.48P single quantum wells grown by Metal Organic Vapor Phase Epitaxy. We have confirmed from the 77 K photoluminescence (PL) that an optimum growth sequence is necessary to achieve the emission from the well (1.52 eV), otherwise only the deep emission band (1.46 eV) is observed. From the time-resolved photoluminescence and temperature dependent PL measurements, we assign that this 1.46 eV deep emission is a recombination of electron-hole pair in a vacancy-related defect which is spatially distributed at the imperfect GaAs/Ga 0.521n0.48P interface.
Semiconductor Superlattices Studied by Grazing X-ray Scattering and Diffraction
Authors: Ming Z. H. , Soo Y. L. , Huang S , Kao Y. H. , Stair K. , Devane G. , Choifeng C. , Chang T. , Fu L. P. , Gilliland G. D. , Klem J. , Hafich M.
Published: April 2011

Semiconductor superlattices have been studied by grazing incidence x-ray scattering and x-ray diffraction. For superlattices of 100-period InGaAs/GaAs, lateral structural ordering has been found to occur in the material. For one particular sample (M1400), periodic thickness modulations have been observed in the InGaAs layers. X-ray results also provide evidence for an improvement of interface quality by using interrupt-growth method for 55-period AlAs/GaAs superlattices grown by MBE.
Mechanisms of Thin Film Ti And Co Silicide Phase Formation on Deep-Sub-Micron Geometries and Their Implications and Applications To 0.18 °m CMOS and Beyond
Authors: Kittl J. A. , Hong Q. Z. , Rodder M.
Published: April 2011

We studied the kinetics of the high resistivity to low resistivity phase transformation for Ti and Co silicides on deep-sub-micron geometries. Fundamental differences between the growth characteristics for Co and Ti result in different scaling behavior. While the the TiSi2 C54 phase grows by a random nucleation and growth process from the polymorphic TiSi2 C49 phase, CoSi 2 grows by a diffusion limited process from CoSi. A strong linewidth and C49 grain size dependence for the TiSi2 C49 to C54 transformation can be related to low nucleation density. A Johnson-Mehl-Avrami analysis was performed for the TiSi2 C49 to C54 transformation obtaining the distribution of Avrami exponents and transformation times for individual 0.26 μm lines, showing that all lines transformed with similar one-dimensional growth characteristics. We found a strong dependence of the half-transformation times on film thickness and linewidth. While activation energies depend strongly on film thickness, ranging from 4.2 to 5 eV for films 64 to 28 nm thick, they are insensitive to linewidth indicating a different nature for the effect of linewidth and thickness. We also found a reduction of agglomeration temperatures with decreasing linewidth or film thickness resulting on a narrower process window for deep-submicron devices. A small linewidth dependence was measured for CoSi to CoSi2 transformation rates, with activation energies of 2 to 2.2 eV for 0.27 μm and wider lines. Both Co and Ti selfaligned silicide processes were implemented successfully into a 0.18 μm technology.
Mesostructured Zirconium Oxide
Authors: Liu P. , Reddy J. S. , Adnot A. , Sayari A.
Published: April 2011

The supramolecular templating technique was used to synthesize both hexagonal (Hx- ZrO2) and lamellar (L-ZrO2) phases of zirconium oxide. Under the conditions used in this work, the use of long chain primary amines and quaternary ammonium surfactants resulted in the exclusive formation of lamellar and hexagonal phases, respectively. The use of long chain cetyldimethylamine afforded a mixture of a hexagonal and a lamellar phases. Effects of synthesis parameters such as the ZrO2/surfactant ratio, ZrO2/water ratio, the nature of surfactant, the crystallization temperature and time on the formation of mesostructured ZrO2 were also studied. Addition of 1,3,5-trimethylbenzene (TMB) as a swelling agent led, in the presence of cetyltrimethylammonium bromide, to the formation of a lamellar phase rather than to pore enlargement. These materials were characterized by XRD, FTIR, XPS and EDX techniques. Regardless of their structure, the as-synthesized materials collapsed upon calcination. Treatment with monobasic potassium phosphate followed by calcination at 350 °C led to the formation of a stable porous Zr–P oxide with a surface area as high as 540 m2/g.
Porous Silica Doping by Ion Bombardment
Authors: Cerofolini G. F. , Meda L. , Anselmino A. , Ranghino G.
Published: April 2011

A new approach to porous-silica doping is via ion bombardment and exposure of thedamaged structure to a controlled atmosphere. As a case study, SiO2 samples, bombarded with Ar2+ in a CO2 ambient and suitably processed, underwent an infrared spectroscopic investigation. The resulting data could be interpreted by assuming the addition of CO2 to the SiO2 skeleton at the diradical silicon defects produced by the bombardment. This addition takes place first via the formation of a carboxylate group, which evolves after heattreatment to an ester-like center, and eventually to a carboxilic acid after exposure to water vapour. Ab initio molecular-dynamics simulations of the interaction between CO2 and a silicon diradical are consistent with the above picture and suggest also the existence of anintermediate, in which tetrahedral carbon is bonded to the two silicon atoms and to two oxygen atoms.
Microporous Crosslinked Elastomers
Authors: Hedrick J. L. , Srinivasan S. , Miller R. D. , Shih D. Y. , Liao Y.-H. , Hilborn J. G. , Plummer C. J. G. , Martina A. Della
Published: April 2011

Elastomeric connectors have been developed for a wide variety of interconnection and test applications which include module-to-board, board-to-board interconnections, high density module, board and LCD testings, as well as chip/wafer testing and burn-in to produce known-good-die. The density, compliance, thickness, pattern and size of these structures can be tailored to meet the requirements of each application. The fabrication processes involve wire bonding and polymer encapsulation. To achieve high compliance with low contact force, alternative means of generating highly compliant elastomers has been developed. This approach involves the incorporation of voids, where the reduction in the compressive force is simply achieved by replacing a portion of the polymer with air. Two approaches of generating porous elastomers are described along with the details of the porosity and mechanical properties.
A Review of the Aqueous Chemistry of the Zirconium - Water System to 200°C
Authors: Adair James.H. , Krarup Henrik G. , Venigalla Sridhar , Tsukada Takayuki
Published: April 2011

The aqueous chemistry of the Zr-H2O system is reviewed. It is shown that the thermodynamically stable solid phase for the Zr-H2O system at 25°C is the monoclinic phase. After a review of the chemistry of the pure material in water, a summary of the solution equilibria of the Zr-H2O system is presented followed by a discussion of the aqueous phase stability of the monoclinic and tetragonal phases of the pure ZrO2 system. Last, a discussion of the phase stability of the complex metal oxides, particularly the Y2O3-containing TZP in aqueous solution will be reviewed. It will be shown that the phase stability for the complex metal oxide-zirconia systems may be best understood as corrosion with the alloying agent (e.g., Y2O3) subject to leaching from a zirconia-rich interface.
Ion Exchange Properties of Novel Hydrous Metal Oxide Materials
Authors: Gardner T. J. , McLaughlin L. I.
Published: April 2011

Hydrous metal oxide (HMO) materials are inorganic ion exchangers which have many desirable characteristics for catalyst support applications, including high cation exchange capacity, anion exchange capability, high surface area, ease of adjustment of acidity and basicity, bulk or thin film preparation, and similar chemistry for preparation of various transition metal oxides. Cation exchange capacity is engineered into these materials through the uniform incorporation of alkali cations via manipulation of alkoxide chemistry. Specific examples of the effects of Na stoichiometry and the addition of SiO2 to hydrous titanium oxide (HTO) on ion exchange behavior will be given. Acid titration and cationic metal precursor complex exchange will be used to characterize the ion exchange behavior of these novel materials.
A Glass Durability Model Based on Understanding Glass Chemistry and Structural Configurations of the Glass Constituents
Authors: Feng Xiangdong , Metzger Todd B.
Published: April 2011

An improved structural bond strength (SBS) model has been developed to quantify the correlation between glass compositions and their chemical durabilities. The SBS model assumes that the strengths of the bonds between cations and oxygens and the structural roles of the individual elements in the glass are the predominant factors controlling the composition dependence of the chemical durability of glasses. The structural roles of oxides in glass are classified as network formers, network breakers, and intermediates. The structural roles of the oxides depend on glass composition and the redox state of oxides. A12O3, ZrO2, Fe2O3, and B2O2 are assigned as network formers only when there are sufficient alkalis to bind with these oxides. CaO can also improve durability by sharing non-bridging oxygen with alkalis, relieving Si0 2 from alkalis. The binding order to alkalis is AI2O3>ZrO2>Fe2O 2>B2O2>CaO>SiO2. The percolation phenomenon in glass is also taken into account. The concentration of network formers has to reach a critical value for a glass to become durable; durable glasses are sufficient in network formers and have a complete network structure; poor durability glasses are deficient in network formers and the network is incomplete and discontinuous. The SBS model is capable of correlating the 7-day product consistency test durability of 42 low-level waste glasses with their composition with an R2 of 0.87, which is better than 0.81 obtained with an eight-coefficient empirical first-order mixture model on the same data set.
In Situ Infrared Study of Chemical Nature of Si Surface in Etching Solution and Water
Authors: Niwano Michio , Miura Taka-Aki , Kimura Yasuo , Tajima Ryo
Published: April 2011

The chemical nature of Si(100) and (111) surfaces during immersion in dilute hydrofluoric acid (HF) solution and water was investigated “in-situ” and in real time using infrared absorption spectroscopy in the multiple internal reflection geometry. We demonstrate that in dilute HF solution, Si surfaces are not perfectly terminated by hydrogen, but are covered in part with hydrogen-associated Si fluorides, such as SiH2(SiF). We find that the hydrogen coverage of the surface during storage in dilute HF solution depends on the HF concentration of the solution. It is shown that rinsing in water following HF treatment leads to complete hydrogen termination of the surface. We also show that hydrogen exchange reaction occurs on the hydrogen-terminated Si surface during storage in water.
X-Ray Texture Analysis of Oriented PZT Thin Films
Authors: Peterson C. R. , Medendorp N. W. , Slamovich E. B. , Bowman K. J.
Published: April 2011

PZT thin films with the composition Pb(Zr0.6Ti0 4)O3 were processed via metallo-organic decomposition (MOD) with {111} and {100} orientations. Ferroelectric measurements showed that the {111} and {100} oriented films had remanent polarizations of 19.5 μC/cm2 and 16 μC/cm2, respectively. Both x-ray pole figure analysis and the Harris texture index were used to quantify the degree of {100}, {110}, and {111} orientation in each film, with reasonable agreement between the two methods. The {100} oriented thin film was determined to be 582 times random for the Harris technique versus 522 times random for pole figure analysis, while the {111} oriented film was 41 times random for the Harris technique and 81 times random for pole figure analysis. The axisymmetric texture of the films allow 2-D pole figure analysis to provide a quantitative characterization of film texture.
Effect of Rapid Thermal Processing on the Crystallization Properties of PbTiO3 Ferroelectric Thin Film
Authors: Zhu Jianguo , Chen Meng , Peng Wenbing , Lan Fahua , Sviridov E.V. , Iao Dingquan
Published: April 2011

The fabrication methods of ferroelectric (FE) thin films have received special attention in recent years because of the needs of FE thin films integrated with semiconductor devices. Rapid thermal processing (RTP) has developed in fabrication of FE thin films because it can reduce processing temperature and time duration, and it also improves the properties of FE thin films compatible with semiconductor devices. The thin film samples used were prepared by a multi-ion-beam reactive cosputtering system (MIBRECS) at room temperature. The samples were then subjected to a post-deposition annealing in a RTP system. It was found that PbTiO3 (PT) thin film could grow on amorphous or polycrystal interfacial layer and the PT thin films annealed by RTP showed the prefered [110] and [100] textures. The effect of interfacial layer on the crystallization and microstructure of the films was also discussed.
Micromechanics of Deformation and Fracture in Low Symmetry Layered Materials
Authors: Kad Bimal K. , Dao Ming , Asaro Robert J.
Published: April 2011

Deformation microstructures in γ-TiAl + α2Ti3Al based low symmetry layered materials, with fully lamellar (FL) microstructures, have been simulated using micro-mechanical methods. In this particular effort we embed the specific contributions of scale and temperature dependent plastic anisotropies of individual colonies of Poly Synthetically Twinned (PST) lamellar TiAl and demonstrate their effect on overall defonnation and fracture response.
Coherency Strain and High Strength at High Temperature
Authors: Brenchley M. E. , Dunstan D. J. , Kidd P. , Kelly A.
Published: April 2011

We propose an athermal strengthening mechanism for high-temperature structural materials in which large coherency strains are built in to a layered structure in order to prevent dislocation mulitplication mechanism from functioning. A practical model system is provided by semiconductor strained-layer superlattices of InGaAs grown on InP. We report results from highresolution X-ray diffraction and from direct tensile testing which provide evidence for athermal strengthening. A discussion of methods of micro-mechanical testing is also included.
Effects of Mechanical Properties of Metal Films on The Adhesion Strength of Cr/Polyimide Interfaces
Authors: Choi Jin Won , Oh Tae Sung
Published: April 2011

Effects of mechanical properties of Cu/Cr metal films on the peel strength of Cr/PI interfaces have been studied. Cr and Cu thin films were successively sputter-deposited on in-situ RF plasma-treated polyimides, and 20 μm-thick Cu was electroplated. With increasing the yield strength of Cu/Cr films from 156 MPa to 325 MPa, peel strength of Cr/PMDA-ODA and Cr/BPDA-PDA were lowered from 75 g/mam to 57 g/mm and from 69 g/mm to 20 g/mm, respectively. With identical Cu/Cr metal films, lower peel strength was obtained on Cr/BPDA-PDA interfaces, compared to the values of Cr/PMDA-ODA. Peel strength was also decreased more pronouncedly on Cr/BPDA-PDA with increasing the yield strength of Cu/Cr metal films. With T/H (80°C/94% R.H.) exposure, however, peel strength was lowered much more pronouncedly on Cr/PMDA-ODA than on Cr/BPDA-PDA, especially for specimens with Cu/Cr metal films of lower yield strength.
Inaccuracies in Sneddon's Solution for Elastic Indentation by a Rigid Cone and their Implications for Nanoindentation Data Analysis
Authors: Bolshakov A. , Pharr G. M.
Published: April 2011

Methods currently used for analyzing nanoindentation load-displacement data to determine a material's hardness and elastic modulus are based on Sneddon's solution for the indentation of an elastic half-space by a rigid axisymmetric indenter. Although this solution is widely used, no attempts have been made to determine how well it works for conditions of finite deformation, as is the case in most nanoindentation experiments with sharp indenters. Analytical and finite element results are presented which show that corrections to Sneddon's solution are needed if it is to be accurately applied to the case of deformation by a rigid cone. Failure to make the corrections results in an underestimation of the load and contact stiffness and an overestimation of the elastic modulus, with the magnitude of the errors depending on the angle of the indenter and Poisson's ratio of the half-space. For a rigid conical indenter with a half-included tip angle of 70.3°, i.e., the angle giving the same area-to-depth ratio as the Berkovich indenter used commonly in nanoindentation experiments, the underestimation of the load and contact stiffness and overestimation of the elastic modulus may be as large as 13%. It is shown that a simple first order correction can be achieved by redefining the effective angle of the indenter in terms of the elastic constants. Implications for the interpretation of nanoindentation data are discussed.
Nano Scale Creep and the Role of Defects
Authors: Asif S. A. Syed , Pethica J. B.
Published: April 2011

The modulating force method in nanoindentation gives a direct measure of contact stiffness, and being insensitive to drift, allows the accurate observation of creep in small indents to be carried out over long time periods. We present results for a range of metals at room temperature. Strain rate indices similar to those for macroscopic creep are found. Reverse creep occurs for step unloading greater than about half the starting load. For electropolished tungsten, we find quite different behaviour before and after the sudden pop-in. Afterwards, creep is as in other metals, but beforehand, it is essentially zero. The slight changes of stiffness observed at the very smallest loads are due to diffusion of adsorbed surface films into the contact zone. Our results show that the dislocations nucleated and multiplied at pop-in provide the mechanism of creep.
Nonlinear Acoustic Response in thin Oxide Layers on Fused Silica
Authors: Ottermann C. R. , Fassbender S. U. , Arnold W. , Bange K.
Published: April 2011

Nonlinear mechanical properties of layered systems of Ta2O5 and TiO2 films deposited on fused silica by reactive evaporation (RE), reactive ion plating (IP) and spin coating (SC) are investigated by means of an ultrasonic technique. The coatings with thickness of 100 nm possess differences in density and crystal structure, due to the different deposition conditions. The nonlinear acoustic response of the film/substrate systems depends on film material. Differences are observed in respect to film density as obtained by the alternate deposition methods. The origin of the differences in nonlinear acoustic response of the samples is discussed. The results are correlated to adhesion properties of the films determined by a scratch-test method.
Measurement of Low-k Polymerimetal Interfacial Toughness Using 4-point Bending Method
Authors: Ma Qing , Pan Chuanbin , Fujimoto Harry , Triplett Baylor , Coon Peter , Chiang Chien
Published: April 2011

Four-point bending method offers significant advantages over more traditional techniques in measuring adhesion properties of thin polymer films. The former utilizes sandwich structure beams where the polymer film and the interface of interest are placed at the center of two elastic bulks. Such confined geometry closely resembles applications where polymer films are used as dielectric layers in IC interconnect technology. In this work, the bonding between a poly(arylene ether) (PAE) based polymer film and an Al film was studied. Ti layers of several different thickness were used as adhesion promoter. The sandwich samples were made by bonding bulk wafers using an epoxy. Fracture energies were seen to increase with the thickness of the Ti layer. Effects of heat treatment were also studied.
Stress in Sputtered Co90Fe10/Ag GMR Multilayers
Authors: Jarratt J. D. , Inturi V. R. , Weston J. L. , Barnard J. A.
Published: April 2011

Stress, giant magnetoresistance (GMR), structure, and magnetic properties of sputtered (Co90Fe10X Å/Ag Y Å)×20 multilayer films have been investigated at room temperature where X ranges from 7.5 to 25 Å and Y from 10 to 60 Å. These films exhibit distinct GMR behaviors dependent on individual layer thicknesses, including layered granular-type GMR in CoFe 7.5 Å samples and ‘discontinuous’ GMR (DGMR) in CoFe 15 and 25 Å samples with Ag thicknesses over 30 Å. No antiferromagnetic coupling was observed. CoFe 10 Å samples act as a transition between GMR behaviors. Compressive stress decreases with increasing Ag thickness in the CoFe 7.5 Å samples. In the CoFe 15 and 25 Å samples the stress fluctuates similarly depending on Ag thickness. The difference in stress and MR behavior between the CoFe 7.5 Å and the 15 and 25 Å samples is thought to be due to incomplete CoFe layering in the CoFe 7.5 Å samples. In the CoFe 15 Å DGMR samples, high temperature annealing resulted in tensile stresses large enough to cause film detachment. X-ray diffraction reveals a strong (111) growth texture as well as satellite peaks from coherent layering. This (111) texture is also evidenced by patterns with hexagonal symmetry formed by the detached films.
Calculation of Equilibrium Island Morphologies for Strained Epitaxial Systems
Authors: Kukta R. V. , Freund L. B.
Published: April 2011

Strained islands grown coherently on a relatively thick substrate with similar elastic properties are considered within the framework of continuum mechanics. The condition of uniform surface chemical potential is imposed to calculate two-dimensional equilibrium island shapes. The stress distribution in the equilibrium islands is shown to be highly nonhomogeneous. The effects of introducing a single misfit dislocation at the island-substrate interface are considered. It is found that there is critical island volume above which a dislocation decreases the total free energy of the system. The dislocation alters the stress distribution in the island, causing the island to relax via mass transport to an equilibrium shape with a lower height-to-width aspect ratio and a smaller surface chemical potential than the island prior to the introduction of the dislocation.
XPS-Study of Excimer Laser-Reconstructed Alumina Surface
Authors: Georgiev D. G. , Kolev K. , Laude L. D. , Brouxhon O.
Published: April 2011

Sintered alumina ceramics are recognized as important industrial materials. For many of their applications however, a suitable pretreatment is required aiming at improving the ceramic surface properties. Since excimer lasers have recently proved to be efficient in ceramic processing, a detailed investigation of sintered alumina surface modifications upon excimer irradiation has been performed. In a previous work the results of low-angle X-ray diffraction analysis reveal emergence of the alumina gamma-phase within the upper 10nm of the material. This presence is further demonstrated by the XPS-study reported here. The photoelectron data are compared with information obtained by optical methods.
Microstructure Control for Thin Film Metallization
Authors: Was G. S. , Srolovitz D. J. , Ma Z. , Liang D.
Published: April 2011

A strategy was developed for controlling hillock formation in thin metal films by controlling the fiber texture to be of a relatively “weak” orientation. Two-dimensional molecular dynamics (MD) simulations were performed to determine the parameter dependencies of texturing under ion beam assisted deposition. Simulations showed that even for film orientations that have a lower number of nearest neighbor surface bonds, the reduction in sputtering rate by ion channeling will favor the growth of the grains aligned with their channeling direction in the direction of the ion beam. Higher energies should result in greater sputtering and a higher surface roughness. Confirmatory experiments were performed by growing Al films using ion beam assisted deposition in which the Ne ion beam was normal to the substrate surface. For all energies above 0 eV/atom, the fiber texture contained a (220) component and, at high normalized energies, the fiber texture was heavily (220) dominated. Subsequent annealing at 450°C for 30 min. resulted in hillock formation in the PVD (physical vapor deposition) condition, a reduction in the hillock density by two orders of magnitude in the 120 eV/atom condition and complete elimination of hillocking above 800 eV/atom. Although the surface roughness increased with ion beam energy as modeled by MD, the surface became smoother during annealing. These results show that the fiber texture can be controlled in a thin metal film in such a way as to eliminate hillock formation, that molecular dynamics simulation is a valuable predictive tool for guiding experiments in the development of thin film microstructures and that ion beam assisted deposition is an effective, practical tool for controlling microstructures of thin metal films.
Structural Transition in Cu/Fe Multilayered Thin Films
Authors: Nguyen Tai D. , Chaiken Alison , Barbee Troy W.
Published: April 2011

Microstructural development of Fe and Cu in Cu/Fe multilayers of layer thickness 1.5–10 nm prepared on Si, Ge, and MgO substrates by ion beam sputtering has been studied using x-ray diffraction and cross-sectional transmission electron microscopy (TEM). High-angle x-ray results show an fcc Cu structure and a distorted bcc structure in the Fe layers at 5 nm-layer-thickness and smaller, and bcc Fe (110) and fcc Cu (111) peaks in the 10 nm-layer-thickness samples. Lowangle x-ray diffraction indicates that the layers in the samples grown on MgO substrates have a more uniform and smooth layered structure than the multilayers grown on Si and Ge substrates, which results from larger grains in the MgO substrate samples for the same layer thickness. Relationships among growth, microstructure, and interfaces with layer thickness are discussed.
Compliant Substrates for Reduction of Strain Relief in Mismatched Overlayers
Authors: Carter-Coman Carrie , Bicknell-Tassius Robert , Brown April S. , Jokerst Nan Marie
Published: April 2011

Thin film compliant substrates can be used to extend the critical thickness in mismatched overlayers. A metastability model has been coupled with recent experimental strain relief data to determine the critical thickness of InGaAs epilayers grown on GaAs compliant substrates of variable thickness. The results of this model are also compared to other compliant substrate critical thickness models.
Effect of Stress on Coherently Grown Au-Ni (001) Solid Solutions
Authors: Abadias G. , Gehanno V. , Marty A. , Gilles B. , Dynna M.
Published: April 2011

The effect of epitaxial stress on the stability of Au-Ni solid solutions grown by MBE on Au(001) is investigated. Experimental studies (TEM, GIXD) have shown that the elastic energy of the AuNi alloys is relaxed via two competing ways: twinning and an ordering process in which pseudo-periodic antiphase structures based on the L10 unit cell are found. The stabilisation of a metastable ordered L10 phase in the stressed Au-Ni system is explained using thermodynamic calculations based on the minimisation of free energy including elastic contributions.
Low Temperature Epitaxial Growth of CeO2(110) Layers on Si(100) Using Bias Evaporation
Authors: Inoue Tomoyasu , Yamamoto Yasuhiro , Satoh Masataka
Published: April 2011

Epitaxial growth of CeO2 layers on silicon (100) substrates is studied using electron-beam evaporation under substrate bias application in an ultrahigh vacuum. Both negative and positive biases are proved to be effective for lowering the epitaxial temperature. Sample current characteristics are measured as a function of the bias voltage. Under negative bias conditions, as the bias voltage increases, the sample current varies from negative to positive with a transition point at -42 V and then reaches a saturation value of ∼ +4 μA above -60 V. Use of a negative bias of -60 V leads to epitaxial growth temperature lowering of ∼, 40°C. Under a positive bias, the sample current is negative and its absolute value increases with the bias voltage, where the sample current components are to be anions and electrons (46°) as determined by mass separation with a magnetic field application. It is experimentally clarified that the degree of enhancement of epitaxial growth is greater than that in the negative bias experiment (750°C at +60 V bias, i. e., epitaxial growth temperature lowering of 70°C) and the enhancement is attributed to the electron component. It is found that a negative current of ∼ -0.15 mA flows at zero bias, indicating that even in conventional evaporation, electrons somewhat promote epitaxial growth.
Van Der Waals Epitaxy of II-Vi Semiconductors on Layered Chalcogenide (0001) Substrates: Towards Buffer Layers for Lattice Mismatched Systems?
Authors: Löher T. , Klein A. , Schaar-Gabriel E. , Rudolph R. , Tomm Y. , Giersig M. , Pettenkofer C. , Jaegermann W.
Published: April 2011

The II-VI semiconductor CdS was grown by molecular beam epitaxy on the van der Waals faces of the layered semiconductor InSe. Chemical, electronic and morphological properties of the deposited films were investigated by means of low energy electron diffraction (LEED), soft x-ray photoelectron spectroscopy (SXPS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). In contrast to observations made on other layered crystals, nucleation of CdS on InSe is possible also at elevated temperatures which is attributed to the small lattice mismatch. The growth front of CdS corresponds to the sulfur terminated polar (111)-B surface which has a strong tendency to form facets.
Diamond Growth on (a) Large Mo Cylinders at 30 Torr and (b) Flat Mo at One Atmospheric Pressure of H2 and CH4
Authors: Ramesham R. , Rose M. F.
Published: April 2011

(a) Polycrystalline diamond films have been grown on cylindrical Mo substrates by hot filament and microwave plasma CVD techniques using a gas mixture of hydrogen and methane. A single hot tungsten filament has been used to demonstrate the growth of adherent diamond films on large cylinders. To our knowledge this is the first report on such large cylindrical substrate (area: 41 cm2 ) using a single filament of active length of 3.75 cm. (b) Polycrystalline diamond films have been deposited by hot-filament technique for the first time using methane and hydrogen at an atmospheric pressure of hydrogen on flat substrates. The diamond growth has been performed at various pressures ranging from 34.5 to 750 Torr. The as-deposited films were analyzed by SEM and Raman to determine morphology and chemical nature, respectively.

A. Growth of Diamond Film on Molybdenum Cylinders
Ultraviolet Excimer Lamp Photoassisted Selective Palladium Activation of Coarse Grain 96% Alumina Ceramic for Selective Electroless Copper Plating
Authors: Macauley D.J. , Kelly P.V. , Crean G.M.
Published: April 2011

Selective electroless metallisation for electronic interconnect applications requires the selective activation of insulating substrate surfaces prior to plating. Photoselective activation has emerged as a solution with significant potential to minimise the number of activation process steps. This paper reports a photoselective activation process using ultraviolet excimer lamps to decompose a proprietary palladium‐based ultraviolet‐sensitive photochemical coating. The morphology of the photochemical coating, irradiation process conditions for decomposition to produce palladium metal activation sites, the morphology of the coating and activation, and the adhesion of electroless copper on coarse grain 96% alumina ceramic are reported. Copper feature resolution of better than 50 μm is demonstrated. The process is demonstrated to require photochemical solution concentrations an order of magnitude lower than reported palladium acetate activation processes.
Monitoring of indium x-ray peak to optimize InxGa1-xN layer grown by metalorganic chemical vapor deposition
Authors: Lu Hongqiang , Thothathiri Malathi , Wu Ziming , Bhat Ishwara
Published: April 2011

Indium droplet formation during the epitaxial growth of InxGa1-xN films is a serious problem for achieving high quality films with high indium mole fraction. In this paper, we studied the formation of indium droplets on the InxGa1-xN films grown by metalorganic chemical vapor deposition (MOCVD) using single crystal x-ray diffraction. It is found that the indium (101) peak in the x-ray diffraction spectra can be utilized as a quantitative measure to determine the amounts of indium droplets on the film. It is shown by monitoring the indium diffraction peak that the density of indium droplets increases at lower growth temperature. To suppress these indium droplets, a modulation growth technique is used. Indium droplet formation in the modulation growth is investigated and it is revealed in our study that the indium droplets problem has been partially relieved by the modulation growth technique.
Characteristics of InGaN Multiquantum-Well-Structure Laser Diodes
Authors: Nakamura Shuji
Published: April 2011

The continuous-wave (CW) operation of InGaN multi-quantum-well-structure laser diodes (LDs) was demonstrated at room temperature (RT) with a lifetime of 35 hours. The threshold current and the voltage of the LDs were 80 mA and 5.5 V, respectively. The threshold current density was 3.6 kA/cm2. Longitudinal modes with a mode separation of 0.042 nm were observed under CW operation at RT. When the temperature of the LDs was varied, large mode hopping of the emission wavelength was observed. The carrier lifetime and the threshold carrier density were estimated to be 10 ns and 2 × 1020/cm3, respectively. The beam full width at half-power values for the parallel and the perpendicular near-field patterns were 1.6 µm and 0.8 µm, respectively. Those of the far-field patterns were 6.8° and 33.6°, respectively.
Stimulated Emission and Gain Measurements from InGaN/GaN Heterostructures
Authors: Shmagin I. K. , Muth J. F. , Krishnankutty S. , Kolbas R. M. , Keller S. , Mishra U. K. , DenBaars S. P.
Published: April 2011

InGaN/GaN Heterostructures were deposited on c-plane sapphire substrates by atmospheric pressure Metalorganic Chemical Vapor Deposition (MOCVD). A frequency tripled modelocked Ti-sapphire laser with a 250 fs pulse operating at 280 nm was used for photoexcitation. Photopumped stimulated emission was observed from InGaN/GaN single heterostructures (SH’s) in both edge and surface emitting configurations. A sharp threshold at the onset of stimulated emission and a strong nonlinear dependence of output emission on input power density was observed. Distinct Fabry-Perot modes corresponding to both cavity configurations were also observed. Gain coefficients were measured from an In0. 14Ga0.86N film using the method developed by Shaklee and Leheny for the edge emitting configuration.