bluuebunny/crossref_metadata_2025 huggingface dataset:
Large Lattice Mismatch Epitaxy
Authors: Mahajan S.
Published: April 2011

During the early stages of lattice mismatch epitaxy, island growth is observed in several systems. The evolution of this morphology is attributed to a large value of the substrate/layer interface energy. Origins of misfit and threading dislocations are also considered. Nucleation of misfit dislocations could occur either from steps present on surfaces of islands or from substrate/island edges. Arms of glide loops terminating at the surface in the first case form threading segments in the layer, whereas the coalescence of islands in which misfit dislocations are not aligned with respect to each other lead to threading dislocations in the second case. Existing approaches for lowering threading dislocation densities are also evaluated. A novel approach involving controlled, self-assembly of islands is presented to achieve the preceding objective.
Multilayer Enzyme Assembly for the Development of a Novel Fiber Optic Biosensor
Authors: Gao Harry H. , Chen Zhongping , Kumar Jayant , Marx Kenneth A. , Tripathy Sukant K. , Kaplan David L.
Published: April 2011

We have developed a technique to immobilize a multilayer enzyme assembly on an optical fiber surface. The technique utilizes a bifunctional amino coupling agent to link between different layers of enzymes. The method offers the flexibility of controlling the number of enzymes on a fiber surface. Multilayers of enzyme — Alkaline Phosphatase have been characterized using ellipsometry and surface plasma resonance. Chemiluminecence experiments have been conducted as a function of number of enzyme layers. The results indicated that at least 3 layers of enzyme can be assembled on a fiber surface. Utilising the new immobilization technique, a novel fiber optic biosensor system for the detection of organophosphorous-based pesticide has been developed. The detection mechanism is the pesticide inhibition of alkaline phosphatase catalyzed chemiluminescence. As a model analyte, paraoxon with ppb level concentration has been detected.
A Dual Constant Composition Study of the Kinetics of Mineralization and Demineralization of Bone Substitutes
Authors: Tucker B.E. , Gorlinea G.L. , Carney D.E. , Nancollas G.H. , Bearcroft J.A.
Published: April 2011

Calcium phosphates are widely used as implantable materials in both dental andorthopaedic applications. Seven different bone substitutes (BS), including Interpore CorallineHAP, Cortical Bio-Oss, Endobon, Cancellous Bio-Oss, Dense HAP (hydroxyapatite), Collagraftgranules, and Porous HAP, have been evaluated using the Dual Constant Composition (DCC)kinetics methods. DCC measurements of the kinetics of dissolution and re-mineralization of theBS materials offer considerable advantages for the characterization of minor calcium-containingsurface species due to the insensitivity of conventional physical chemical methods such as X-raydiffraction and ESCA. Each sample was pre-conditioned (PC) in 0.15 M NaCl prior to the DCCkinetics procedures. The fastest dissolving material, Collagraft granules, showed a dissolution ratemore than two orders of magnitude larger than Dense HAP. Interestingly, the relativesupersaturation with respect to HAP (σ) following PC was normally negative, whereas withplasma sprayed HAP coated implants, these a values were as high as 20. Surface impurities mayplay a major role following in vivo implantation, since resorption is probably a major reparativemechanism. It is therefore essential to understand the dissolution behavior. Moreover, in a remineralizationmode, trace surface phases may determine the phase and morphology of the newlydeposited bone mineral.
Growth of GaAs/AlGaAs Quantum Dots Using Self-Organized InP Stressors
Authors: Hanna M. C. , Lu Z. H. , Cahill A. F. , Heben M. J. , Nozik A. J.
Published: April 2011

GaAs quantum dots were formed in a near surface quantum well (QW) by producing lateral confinement with self-organized InP stressors grown in situ by metal organic chemical vapor deposition (MOCVD). We report here the influence of growth conditions on InP island formation on AlGaAs/GaAs single QW structures and also the influence of the QW structure on the optical properties of the GaAs quantum dots. We observe strong photoluminscence up to room temperature from the strain-induced quantum dots with energy redshifts of 70 meV below the QW peak.
Growth and Characterization of BRS GaInAsp-GaAs Laser Emitting At 0.8μm by Gas-Source Molecular Beam Epitaxy
Authors: Jelen C. , Slivken S. , Diaz J. , Erdtmann M. , Kim S. , Wu D. , Razeghi M.
Published: April 2011

GaInAsP-GaAs buried ridge structure lasers emitting at 0.8μm have been fabricated on material grown in two steps by low pressure metalorganic chemical vapor deposition and gas-source molecular beam epitaxy. Preliminary laser results are reported, and the feasibility of using gas-source molecular beam epitaxy for the regrowth of sophisticated laser system is demonstrated.
Growth and Capacitance Spectroscopy of Self Assembled Quantum Dots
Authors: Medeiros-Ribeiro G. , Schmidt K. H. , Leonard D. , Cheng Y. M. , Petroff P. M.
Published: April 2011

The growth of InAs on GaAs self assembled quantum dots and their electronic properties is studied. The limit for coherent island growth is calculated with a simple model and compared to the experimentally observed values. Cross section transmission electron micrography and atomic force micrography are used to investigate this limit. The electronic properties studies involved the use of capacitance spectroscopy to map out the density of states in these structures as well as to probe the temperature dependence of the Coulomb Blockade effect in this system. It was found that Coulomb Blockade could be observed at temperatures in excess of 77K, representing an attractive approach for single electronics operating at high temperatures.
On the Moss-Burstein Shift in Quantum Confined Optoelectronic Ternary and Quaternary Materials
Authors: Ghatajc Kamakhya P. , Nag B. , Biswas S. N.
Published: April 2011

In this paper we have studied, the Burstein-Moss shift (BMS) in quantum wires (QWs) and quantum dots (QDs) of ternary and quaternary types of optoelectronic materials on the basis of a newly formulated electron dispersion law which occours as a result of heavy doping. It has been found, taking Hg1−xCdx.Te and In1−x.Gax.AsyP1−y lattice matched to InP as examples, that the BMS increases with :Lncreasing electron concentration and decreases with increasing film thickness in oscillatory manners for both types of quantum confinements, although the variations are totally band structure dependent. The numerical values of BMS is greatest in QDs and least in QWs together with the fact that the BMS in quaternary materials is greater than that of ternary comupounds. In addition the theoretical analysis is a quantitative agreement with the experimental datas as given elsewhere.
Influence of Structure on the Formation of Dislocation in LBO Crystal
Authors: Hu X. B. , Jiang S. S. , Huang X. R. , Zeng W. , Liu W. J. , Zheng Y. D. , Zhao Q. L. , Chen C. T.
Published: April 2011

Dislocations in LiB3O5(LBO) single crystal were investigated by white-beam synchrotron radiation topography(WBSRT). The WBSRT revealed that the grown-in dislocations are mainly pure screw or edge types with the Burgers vectors in the low index directions on (010) lattice plane. Based on the structure analysis, the formation cause of dislocations can be interpreted in terms of the loose packing of B-O rings and the low density of Li+on (010) lattice plane.
Theory of Surface Dimerization-induced Ordering in GaInP Alloys
Authors: Zhang S. B. , Froyen Sverre , Zunger Alex
Published: April 2011

We identify via thermodynamic energy minimization the role of subsurface strain (caused by surface reconstruction and dimerization) in the ordering of Ga0.51n0.5P alloys. Depending on the growth conditions, the alloy surfaces can have either β2(2×4), c(4×4) or c(8×6) reconstructions, with characteristic 2×1, 1×2 and 2×3 RHEED patterns. We show that (i) the 1×2 reconstruction will lead to a CUPtA surface ordering, (ii) a 2×1 reconstruction will lead to a CuPtB ordering, (iii) a 2×3 reconstruction will lead to a 3-period ordering, and (iv) single (double) bilayer steps are stable at low (high) anion chemical potential. These results are in good agreement with recent experimental observations.
A Polarization Study of Ordered GaInP2
Authors: Zhang Yong , Ernst P. , Driessen F. A. J. M. , Mascarenhas A. , Geng C. , Scholz F. , Schweizer H.
Published: April 2011

Optical polarization in ordered GaInP2 has been studied by low-temperature photoluminescence. By comparing our experimental results to the theoretical predictions, we show that to obtain quantitative information about ordering from the polarization of near-band-gap transitions, the effects of lattice mismatch, substrate misorientation, and excitonic transitions should be taken into account.
Ultra-low Contact Resistivity by High Concentration Germanium and Boron Ion Implantation Combined with Low Temperature Annealing
Authors: Murakoshi A. , Iwase M. , Koike M. , Niiyama H. , Suguro K.
Published: April 2011

A new formation method for an ultra-low resistivity contact and structural analysis are discussed. In this study, a minimum contact resistivity of 6.9× 10−9 Ω·cm2 has been successfully obtained in an AlSi(lwt%)Cu(0.5wt%) alloy / Si system by using heavy dose ion implantations of Ge and B combined with low temperature annealing as low as 550°C. Structural analysis on the Si surface layer has been carried out. As a result, it was found that the crystal lattice was expanded in-plane by 6% in the Si layer near the surface because of the high concentration of Ge and no relaxation of lattice strain at such a low temperature. It was also found that super-saturation of B was stably formed in this system. An ultra-low resistivity contact is considered to be a result of these combined effects.
Current Issues and Future Trends in CMP Consumables for Oxide and Metal Polish
Authors: Moinpour M. , Philipossian A.
Published: April 2011

Introduction

The recent advent of Chemical Mechanical Planarization (CMP) as a major process technology has had a significant impact on the semiconductor industry. Oxide CMP is a technology enabler for logic and DRAM devices with feature sizes less than (or equal to) 0.75 micrometer [1]. Similarly, tungsten CMP has become a technology enabler for 0.35 micron devices [2,3], and current trends indicate that it will continue to play a major role in future generations of IC technologies [4,5]. CMP can also provide a technological advantage in front-end process modules such as Shallow Trench Isolation [6].
Optimization of PVD Ti/CVD TiN Liner for 0.35 μm Tungsten Plug Technology
Authors: Wang C.-K. , Liu L. M. , Liao D. M. , Smith D. C. , Danek M.
Published: April 2011

A novel plasma enhanced CVD TiN process was integrated with high density plasma sputter etch preclean (PCII) and 1:1.5 collimated PVD Ti (c-PVD Ti) process to deposit a Ti/TiN liner for tungsten contact and via plugs. The integrated liner process was optimized for a 0.35 μm nonsalicide CMOS device application. RF power and sputter depth used for contact preclean were the major process variants affecting the contact resistance, junction leakage and transistor threshold voltage. Low contact resistance was obtained for a c-PVD Ti thickness of ∼375 Å. Via resistance was significantly lower with c-PVD Ti/CVD TiN liner as compared to only a TiN liner. Contact resistance for c-PVD Ti/c-PVD TiN and c-PVD Ti/CVD TiN liners were comparable while contacts with conventional PVD Ti/TiN liner showed significantly higher values due to poor step coverage. Low junction leakage current was obtained for integrated c- PVD Ti/CVD TiN stack.
Growth and Properties of W-Si-N Diffusion Barriers Deposited by Chemical Vapor Deposition
Authors: Fleming J. G. , Roherty-Osmun E. , Custer J. S.
Published: April 2011

We have used chemical vapor deposition to grow ternary tungsten based diffusion barriers to determine if they exhibit properties similar to those of sputter deposited ternaries. A range of different W-Si-N compositions were produced. The deposition temperature was low, 350°C, and the precursors used are accepted by the industry. Deposition rates are acceptable for a diffusion barrier application. Resistivities range from 350 to 20000 μΩ-cm, depending on composition. Step coverage of films with compositions expected to be of interest for diffusion barrier applications is 100%.
Electrical Characterization of Ultra-Shallow Junctions Formed by Diffusion From a CoSi2 Diffusion Source
Authors: Via F. La , Rimini E.
Published: April 2011

Ultra-Shallow p+/n and n+/p junctions were fabricated using a Silicide-As-Diffusion-Source (SADS) process and a low thermal budget (800÷900 °C). A thin layer (50 nm) of CoSi2 was implanted with As and BF2 and subsequently diffused at different temperatures and times to form two Ultra-Shallow junctions with a junction depth of 14 and 20 nm. These diodes were extensively investigated by I-V and C-V measurements in the range of temperature between 80 and 500 K. TEM delineation was used to controll the junction uniformity.
Amorphous Phase Formation of Titanium Silicide on The 4° off-Axis and on-Axis Si(100) Substrates
Authors: Jeon Hyeongtag , Lee Sukjae , Lee Hwackjoo , Ruh Hyun
Published: April 2011

Two different Si(100) substrates, the 4°off-axis and the on-axis Si(100), were prepared. Ti thin films were deposited in an e-beam evaporation system and the amorphous layers of Ti-silicide were formed at different annealing temperatures. The Si(100) substrates before Ti film deposition were examined with AFM to verify the atomic scale roughness of the initial Si substrates. The amorphous layer was observed by HRTEM and TEM. And the chemical analysis and phase identification were examined by AES and XRD. The Si(100) substrate after HF clean shows the atomic scale microroughness such as atomic steps and pits on the Si surface. The on-axis Si(100) substrate exhibits much rougher surface morphologies than those of the off-axis Si(100). These differences of atomic scale roughnesses of Si substrates result in the difference of the thicknesses of amorphous Ti-silicide layers. The amorphous layer thicknesses on the on-axis exhibit thicker than those of the off-axis Si(100) and these differences inamorphous layer thicknesses became decreased as annealing temperatures increased. These indicate that the role of the atomic scale roughness on the amorphous layer thickness is much significant at low temperatures. In this study, the correlation between the atomic scale roughness and the amorphous layer thickness is discussed in terms of the atomic steps and pits based on the observation with using analysis tools such as AFM, TEM and HRTEM.
Shallow and Low-Resistive Ohmic Contacts to p-In0.53Ga0. 47As Based on Pd/Au and Pd/Sb Metallizations
Authors: Ressel P. , Wang L. C. , Park M. H. , Leech P. W. , Reeves G. K. , Kuphal E.
Published: April 2011

InP/In0.53Ga0.47As heterojunction bipolar transistors with high current gain for optoelectronic applications place stringent requirements on the ohmic contact to the base layer of moderately doped (p < 1×1019 cm−3) In0.53Ga0.47As. Contact resistivity should be <l×10−6 Ωcm2 and low depth of penetration is necessary considering the small base thickness of approximately 100 nm. The authors have recently presented data on Pd/Zn/Au/LaB6/Au contacts on p-In0.53Ga0.47As (doped to 4×1018 cm−3) with low contact resistivities of l×10−6 Ωcm2. In this paper, details are given on the optimization of the contact composition and annealing conditions of the metallization that resulted in shallow and low-resistive contacts. Alternatively, it is shown that Au-free Pd/Zn/Sb/Pd contacts on p-In0.53Ga0.47As have exhibited even lower resistivities, i.e. 3-6×10−7 Ωcm2. Backside SIMS measurements revealed a depth of penetration as low as 20 nm for this contact scheme. Aging tests at temperatures of 300 - 400 °C have demonstrated that the electrical characteristics of both types of metallization were sufficiently stable to withstand the typical processing steps for device passivation.
Growth and Engineering of Microporous Zeolite Films and Coatings
Authors: Yan Y. , Chaudhuri S. Ray. , Sarkar A.
Published: April 2011

Developing very thin molecular sieve films (<lμm), required by many zeolite filmbased applications, has been found continually to be a technical challenge. The synthesis strategy of this work is to elucidate some of the parameters that influence the morphology, orientation, surface coverage density and thickness of Si-ZSM-5 films on supported substrates. Three different methods to grow zeolite coatings on fused silica have be studied and compared. The zeolite films have been characterized by field emission-SEM, XRD, sorption study and transmitting spectroscopy. At the early stage of crystal growth, the gel layer spontaneously condensed on the substrate surface may have a large porosity of 15%. The strong affinity to grow the (010) faces along the substrate surface is possibly responsible for the preferred orientation of the films. The conditions for synthesis of closely packed coatings, consisting of sub-micron crystals with preferred orientation, are also identified. Engineering issues for fabrication of low optical scattering zeolitic films will also be discussed for designing molecular sieve optical devices.
Gas Permeation and Microstructure of Silica Membranes Prepared Using an Organic Template Approach by Sol-Gel Processing
Authors: Cao G. Z. , Brinker C. J.
Published: April 2011

This paper investigates microporous amorphous silica membranes prepared using an organic template sol-gel approach. We find that the introduction of organic methacryloxypropyl ligands results in a reduced average condensation rate and a lower extent of branching that promotes the collapse of the hybrid network upon drying leading to relatively dense hybrid organic-inorganic xerogels and films. Microporous silica xerogels and membranes, prepared by oxidative pyrolysis of the organic templates at 300 °C for 5 hours in oxygen, contained pores with constrictions of approximately 0.35 nm in diameter with a very narrow size distribution, as evidenced by single gas permeation measurements of a series of probe molecules.
Gas Sensing Behavior of Porous ZnO Varistors Densified via Rate Controlled Sintering
Authors: Agarwal Gaurav , Speyer Robert F.
Published: April 2011

A hydrogen gas sensor based on shift in breakdown voltage of a ZnO varistor was developed. Changes in rate controlled sintering schedules resulted in significant variations in microstructure. Microstructures showing more intergranular porosity and finer grain size demonstrated a comparatively more linear and broad response to H2 concentration. A mechanism for the shift in breakdown voltage based on adsorbed oxygen is suggested for this unique and potentially very useful sensor.
A Comparison of the Electrochemical Behavior of Carbon Aerogels and Activated Carbon Fiber Cloths
Authors: Tran T. D. , Alviso C. T. , Hulsey S. S. , Nielsen J. K. , Pekala R. W.
Published: April 2011

The electrochemical capacitative behavior of carbon aerogels and selected commercial carbon fiber cloths was studied in 5M potassium hydroxide, 3M sulfuric acid, and 0.5M tetraethylammonium tetrafluoroborate/propylene carbonate electrolytes. The resorcinolformaldehyde based carbon aerogels with a range of density (0.2–0.85 g/cc) have open-cell structures with ultrafine pore sizes (∼5–50 nm), high surface area (400–700 m2/g), and a solid matrix composed of interconnected particles or fibers with characteristic diameters of 10 nm. The commercial fiber cloths in the density range 0.2–0.4g/cc have high surface areas (1000–2500 m2/g). The volumetric capacitances of high-density aerogels are shown to be comparable to or exceeding those obtained from activated carbon fibers. The electrochemical behavior of these types of materials in various electrolytes is compared and related to their physical properties.
Electronic Doping in Porous Nano-Crystalline ZnO Films
Authors: Könenkamp R. , Wahi A.
Published: April 2011

Porous nano-crystalline ZnO films were prepared in sol-gel technique, using spin coating and sintering at modest temperatures. The films consist of loosely-packed ZnO clusters. For films with clusters smaller than ∼ 50 Å we find a blue-shifted absorption edge indicative of quantum confinement in the clusters. The electronic properties of the films are largely controlled by surface processes. We have studied photo-induced conductance changes due to CO2 desorption using mass spectrometry and concomitant electrical measurements.
Nanofoam Porosity Measured by Infrared Spectroscopy and Refractive Index
Authors: Sanchez M. I. , Hedrick J. L. , Russell T. P.
Published: April 2011

Infrared spectroscopy and optical waveguide were used to determine the porosity of polymer nanofoams produced from block copolymers of an aromatic polyimide endcapped with either poly(propylene oxide) or poly(a-methylstyrene). The infrared absorption bands and film thickness were compared to those of the neat homopolymer to yield an accurate measure of the void content. The porosity was also determined by measuring the refractive index and using the Maxwell-Garnett effective medium theory for spherical particles. Both techniques are in quantitative agreement with density gradient methods.
Nucleation and Growth of Fe(III)/PO4 Clusters
Authors: Rose J. , Flank A. M. , Manceau A. , Masion A. , Bottero J. Y. , Tchoubar D. , Garcia F.
Published: April 2011

The first stages of the hydrolysis of Fe(III) in presence of PO4 were studied at the local (P k-edge and Fe k-edge EXAFS spectroscopy) and semi-local scale (SAXS). The presence of PO4 hinders the polymerization of iron at the edge sharing dimer step. Phosphate probably governs the local structure leading to the formation of small and dense clusters. The fitting of both k-edge EXAFS spectroscopies requiered the use of a new 3D model of each nucleation step.
The Interaction of Liquid and Vapor Water with Nearly Defect-Free and Defective TiO2(100) Surfaces
Authors: Wang Li-Qiong , Skiba P. X. , Shultz A. N. , Baer Don R. , Engelhard Mark H.
Published: April 2011

The interaction of both liquid and vapor water on nearly defect-free and defective TiO2(100) surfaces has been investigated using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). The study has focused on examining electronic or chemical defects as created in vacuum and after exposure to both liquid and vapor water. Defective surfaces were prepared by electron-beam exposure and Ar+ bombardment. For a nearly defect-free (100)1×1 surface, water coverage was ∼0.02 ML (1ML = 2.9×1015/cm2) at 104 L exposure to low vapor pressure water, ∼0.08 ML at 108 L exposure to higher vapor pressure water, and ∼0.12 ML with liquid water exposure, respectively. Defect intensities were greatly reduced after exposing defective surfaces to ∼102 L low vapor pressure water. More significantly, electron-beam induced defects were completely removed upon higher-pressure vapor exposure (>104 L) or liquid water exposure, while defects created by Ar+ bombardment were only partially removed. The adsorption behavior and surface defect reactivity for TiO2(100) 1×1 surfaces were compared with those for TiO2(110) surfaces. The adsorption rates for nearly defect-free (100) 1×1 and (110) surfaces are comparable. However, the rate of defect “healing” for a defective (100) surface is much faster than that for a defective (110) surface.
Rf Magnetron Sputter-Deposition of La0.5Sr0.5CoO3//Pt Composite Electrodes for Pb(Zr, Ti)O3 Thin Film Capacitors
Authors: Raymond M. V. , Al-Shareef H. N. , Tuttle B. A. , DiMos D. , Evans J. T.
Published: April 2011

La0.5Sr0.5CoO3 (LSCO) thin films have been deposited using RF magnetron sputterdeposition for use as an electrode material for Pb(Zr, Ti)O3 (PZT) thin film capacitors. The effect of the O2:Ar sputter gas ratio during deposition, on the LSCO film properties was investigated. It was found that the resistivity of the LSCO films deposited at ambient temperature decreases as the O2:Ar ratio was increased for both the as-deposited and annealed films. In addition, it was found that thin overlayers of LSCO tend to stabilize the underlying Pt//Ti electrode structure during subsequent thermal processing. The LSCO//Pt//Ti composite electrode stack has a low resistivity and provides excellent fatigue performance for PZT capacitors. Furthermore, the LSCO//Pt//Ti electrode sheet resistance does not degrade with annealing temperature and the electrode does not display hillock formation. Possible mechanisms for the stabilization of the Pt//Ti electrode with LSCO overlayers will be discussed.
Microstructure of Pulsed-Laser Deposited Pzt on Polished and Annealed Mgo Substrates
Authors: King Simon L. , Coccia Luigi G. , Gardeniers J.G.E. , Boyd Ian W.
Published: April 2011

Thin films of Lead-Zirconate-Titanate (PZT) have been grown by pulsed-laserdeposition (PLD) onto polished MgO substrates both with and without pre-annealing.

The surface morphology of polished MgO substrates, which are widely used for deposition, is examined by AFM. Commercially available, mechanically-polished substrates are shown to be microscopically very rough and seem unlikely to present a surface suitable for the growth of the highest quality thin films. Annealed MgO substrates, on the other hand, comprise atomically flat terraces. The use of annealed substrates is found to enhance considerably the crystalline quality of PZT films deposited thereon.
Microstructural Characterization of Pt/Ti and RuO2 Electrodes on SiO2/Si Annealed in the Oxygen Ambient
Authors: Lee Jeong Soo , Kwon Hyun JA , Jeong Young Woo , Kim Hyun HA , Park Kyu HO , Kim Cha Yeon
Published: April 2011

Microstructures and interdiffusions of Pt/Ti/SiO2/Si and RuO2/SiO2/Si during annealing in O2 were investigated using x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The degree of oxidation and the interdiffusion of elements have remarkably increased with increasing temperature above 500 °C for the Pt/Ti/SiO2/Si case. The generation of Pt hillocks commenced at 500 °C. The Pt-silicide phase was also observed near the TiOx/SiO2 interface. The microstructural variations occurred to only a small amount for the RuO2/SiO2/Si case over the temperature range 300 – 700 °C. While there was no hillock formation, the RuO2 film surface was roughened by the thermal grooving phenomenon. A thin interlayer phase was found at the RuO2/SiO2 interface.
Defects and Electronic Transport in Rare Earth Doped Epitaxial SrTiO3 Thin Films
Authors: Gilbert S.R. , Wessels B.W. , Brazis P.W. , Hogan T.P. , Kannewurf C.R.
Published: April 2011

Semiconducting, epitaxial SrTiO3 thin films doped with Eu3+ donors were analyzed using transient photocapacitance spectroscopy to determine the nature of the charge compensating defects. Deep level defects were detected with optical thresholds at Ec - 0.6 eV, Ec - 0.8 eV, and Ec - 2.05 eV. The level at Ec - 0.8 eV was the dominant defect in all of the films examined, with concentrations ranging from 1.6×1015 to 1.2×1017 cm−3 that increased as the square of donor concentration. The level was attributed to the strontium vacancy.
Microstructural Characterisation of Pb(Zr0.52Ti0.48)O3 Thin Films Deposited on RuO2 Electrodes by Laser Ablation
Authors: Benedittis A De , Cristoforo A. Di , Mengucci P. , Majni G. , Diodati A. , Leccabue F. , Watts B.E. , Seuret D. , Smeets J.
Published: April 2011

An aspect which has hindered the development of ferroelectric memories is dielectric fatigue and to resolve this conducting oxides are promising candidates as an electrode material for lead zirconate titanate thin films. In this work ferroelectric films have been grown by pulsed laser deposition on ruthenium oxide electrodes. The phase distribution, microstructure and the effect of subsequent heat treatment have been studied by grazing angle X ray diffraction and electron microscopy; the results and implications for use of RuO2 as the bottom electrode during vapour phase deposition are discussed.
Low Temperature Fabrication of (Ba, Sr)TiO3 Thin Films by ECR Plasma CVD
Authors: Kato Y. , Yabuta H. , Sone S. , Yamaguchi H. , Iizuka T. , Yamamichi S. , Lesaicherre P-Y. , Nishimoto S. , Yoshida M.
Published: April 2011

Physical and electrical properties are investigated for (Ba, Sr)TiO3 (BST) films prepared by electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) at relatively low temperatures, between 450 °C and 500 °C. The crystallinity of BST, estimated by X-ray diffraction and from the grain size, is greatly improved when the temperature is raised from 450 °C to 500 °C. Also better crystallinity is obtained for films grown at a deposition rate of 1.1 nn/min than at 2.7 nm/min. The mass transport rates of metal organic sources under our deposition conditions are estimated. The BST film composition is precisely controlled using the results of the investigation on mass transport. At near stoichiometric composition, i.e., (Ba+Sr)/Ti=0.97, and Ba/(Ba+Sr)=0.4, the films grown at 500 °C are found to have the largest dielectric constant, measured using flat capacitors with Pt bottom electrodes. A dielectric constant of 160 is obtained for 27 nm thick films grown at 500 °C and at 1.1 nm/min, without post-deposition annealing. These films exhibit the smallest SiO2 equivalent thickness of 0.65 nm and a leakage current density of 4.6x10−7 A/cm2 at plus IV.
Thickness-Dependent Electrical Properties in Lanthanum-Doped Pzt Thick Films
Authors: Chen H.D. , Li K.K. , Gaskey C.J. , Cross L.E.
Published: April 2011

Lanthanum-doped lead zirconate titanate (PLZT) films, with thickness up to 10 μm, are fabricated on platinized silicon substrates through a modified sol-gel technique. Thicknessdependent piezoelectric properties measured with a double-beam laser interferometer show piezoelectric relaxation in field-induced strain as the ac driving field exceeds 10 kV/cm. In addition, the strain levels of PLZT thick films are approximately one third of those of undoped PZT films under the same fabrication and measurement conditions. For 1 μm PZT(55/45) films doped with 0, 2, and 4 mole% La, the P-E hysteresis exhibits decreasing squareness with increasing lanthanum content while the piezoelectric d33 coefficient reduces from 130 to 52 pC/N. Residual (tensile) stress in these films and resulted depoling effect may be responsible for this phenomenon.
Interfacial Diffusion Effects and Non-Stability of Disperse Layered Structures
Authors: Paritskaya L. N. , Bogdanov V. V.
Published: April 2011

The kinetics and atomic mechanism of the low temperature phase formation and accompanying effects in disperse multilayered structures of the binary systems Ni – Cr and Ni – Al have been studied under the conditions when volume diffusion is practically “frozen”.
An Analysis of Ductile Brittle Fracture Transition in Layered Composites
Authors: Biner S. B.
Published: April 2011

In this study the failure of the ductile layers in laminated composite systems was studied numerically. The results indicate that similar maximum stress values develop in the ductile layers as in the fracture test of the same ductile material if the crack tip in the brittle layer is already at the interface. For nondebonding interfaces brittle behavior of the ductile layers is dependent upon the extent of the cracks and the fracture characteristic of the brittle layers.
Inherently Smart Laminates of Carbon Fibers in a Polymer Matrix
Authors: Ang Xiaojun W , Chung D. D. L.
Published: April 2011

Real-time monitoring of fatigue damage and dynamic strain in inherently smart andcontinuous unidirectional (0° and 90°) and bidirectional (0°/90°) carbon fiber epoxy-matrix composites by electrical resistance (R) measurement was achieved. Upon cyclic tension (0°) of 0° or 0°/90° composites, R (0°) decreased reversibly, while R perpendicular to the fiber layers increased reversibly, though R in both directions changed irreversibly by a small amount after the first cycle. Upon fatigue testing of the 0° composite at a maximum stress of 57–58% of the fracture stress, the peak R (0°) in a cycle irreversibly increased both in spurts and continuously, due to fiber breakage, which started at 30% of the fatigue life. For the 90° composite, R(0°) increased reversibly upon tension (0°) and decreased reversibly upon compression (0°).
Advanced Aircraft Engine Microlaminated Intermetallic Composite Turbine Technology
Authors: Rowe R. G. , Skelly D. W. , Jackson M. R. , Larsen M. , Lachapelle D.
Published: April 2011

Higher gas path temperatures for greater aircraft engine thrust and efficiency will require both higher temperature gas turbine airfoil materials and optimization of internal cooling technology. Microlaminated composites consisting of very high temperature intermetallic compounds and ductile refractory metals offer a means of achieving higher temperature turbine airfoil capability without sacrificing low temperature fracture resistance. Physical vapor deposition, used to synthesize microlaminated composites, also offers a means of fabricating advanced turbine blade internal cooling designs. The low temperature fracture resistance of microlaminated Nb(Cr)-Cr2Nb microlaminated composites approached 20 MPa√m in fracture resistance curves, but the fine grain size of vapor deposited intermetallics indicates a need to develop creep resistant microstructures.
Analysis of Stresses and Strains In Passivated Metal Lines
Authors: Eppler I. , Schroeder H. , Burges U. , Schilling W.
Published: April 2011

Passivated metal lines, commonly used in integrated circuits, show thermally induced stresses due to the difference of the thermal expansion coefficients of the lines and their surroundings. These stresses cause voidage and plastic flow of the lines. Aim of the analysis was to derive equations connecting experimentally measured strains or stresses by the X-ray diffraction and wafer curvature techniques with the magnitude of voidage and plastic shear deformation of the lines.

Using the concepts of linear elasticity the volume averaged stresses of an array of parallel interconnects embedded in a passivation layer on a flat substrate are analysed. Equations are derived connecting the volume averaged stresses in the metal and in the passivation with the “Heigen-strains” of the metal which characterize the true (stress free) thermal strains and plastic deformation strains of the metal. The coefficients entering these equations are determined from (elastic) finite element method (FEM) calculations performed for various geometries and aspect ratios of the metal lines. Choosing the proper values of the coefficients allows the eigen- strains to be determined from the experimental data.

By comparison of the evaluated eigen-strains with the purely elastic eigen-strains ΔαΔT the extent of voidage and/or plastic shear deformation of passivated metal lines caused by thermally induced stresses can be determined model independently.
Processing-Induced Stresses and Curvature in Patterned Lines on Silicon Wafers
Authors: Shen Y. -L. , Suresh S. , Blech I. A.
Published: April 2011

The evolution of stresses due to the patterning and thermal loading of thin lines on Si wafers, and the consequent changes in the overall curvature of the wafer are studied theoretically and experimentally. The analysis involves finite element simulations within the context of generalized plane strain models. The analysis is capable of predicting the wafer curvature in directions parallel and perpendicular to the lines. These predictions compare reasonably well with experimental measurements of curvature made on model systems. The thickness, width and spacing of the patterned lines have been varied systematically, and the associated changes in the evolution of stresses and curvature have been determined. The non-uniform stress field within the fine lines is also analyzed.
Stress Analysis of Titanium Dioxide Films by Raman Scattering and X-Ray Diffraction Methods
Authors: Meng Li-Jian , Santos M. P. dos
Published: April 2011

Titanium dioxide films have been deposited onto glass substrates by dc reactive magnetron sputtering at different sputtering pressures (2×10−3 -- 2×10−2 mbar). The films have been characterized by measuring their Raman scattering and X-ray diffraction (XRD). The films stress have been calculated by analyzing their Raman spectra and X-ray diffraction spectra. Two methods give similar results which films prepared at low sputtering pressure have high stress values.
Effect of Thickness and Annealing on Stress in Tantalum and Tantalum Nitride Thin Film Hard Coatings
Authors: Saha Ranjana , Inturi Rama B. , Barnard John A.
Published: April 2011

An understanding of the relationship between stress and the other properties of thin films is extremely useful in the design of hard coatings for long term performance. In our earlier study, sputtered Ta and Ta(N) films were found to exhibit promising hard coating properties. For example, nano hardness as high as 30 GPa was observed in the nitride (pN2 = 0.100 mTorr) films. In this work, we study the variation in the stress in these films with respect to film thickness and annealing. Films in six different thicknesses (50, 250, 350, 500, 750, and 1000 nm) were deposited on oxide coated Si (111) wafers. Stresses in the films in the as-deposited state and as a function of temperature (300°C) were determined using a thin film stress measuring unit.
Effect of in and Out of Plane Stresses During Indentation of Diamond Films on Metal Substrates
Authors: Bahr D. F. , Gerberich W. W.
Published: April 2011

Diamond films grown on molybdenum substrates are indented with conical diamond indenters to depths more than 5 times the thickness of the film. This causes delamination and spalling of the film. The effects of variations in indenter angle and film thickness are demonstrated. Using a radius of the delaminated area to the residual contact radius, sharper indenters are shown to cause a 10 to 20% change in that ratio. For films greater than 5 μm thick, there is no apparent film thickness effect. Possibilities for this observation are cracking due to bending stresses or the interfacial crack kinking out of the interface due to a reduction in compressive stresses, leading to mixed mode loading. The strain energy release rate of the interface for an 800 nm diamond film on molybdenum is between 2.4 and 7 J/m2.
Phase Transitions and Local Structure of PbZrO3
Authors: Teslic S. , Egami T.
Published: April 2011

The local atomic structure of PbZrO3 (PZ) as a function of temperature has been examined using the atomic pair distribution function (PDF) analysis of the pulsed neutron powder-diffraction data. The local structure was found to be deviated significantly from the crystallographic average structure, and to vary less with the composition than the crystallographic average structure. Disordered oxygen octahedral rotations have been observed in the low-temperature antiferroelectric state. With heating the M-type rotation of octahedra becomes dominant and it persists through the intermediate phase into the high-temperature paraelectric state. The Pb displacements reflect these strong deviations, and locally have a large z-component. At room temperature, deviation of Pb displacements from the antiparallel [110] pattern was found. With increasing temperature disorder in the Pb displacement increases.
Angle-Resolved Photoemission Extended Fine Structure Study Of Chemisorbed c(2×2)P/Fe(100): Comparison With Self-Consistent-Field Xα Scattered Wave Calculations
Authors: Huff W.R.A. , Chen Y. , Zhang X.S. , Terminello L.J. , Tao F.M. , Pan Y.K. , Kellar S.A. , Moler E.J. , Hussain Z. , Wu H. , Zheng Y. , Zhou X. , Wittenau A.E. Schach von , Kim S. , Huang Z.Q. , Yang Z.Z. , Shirley D.A.
Published: April 2011

Angle-resolved photoemission extended fine structure (ARPEFS) was used to determine the structure of c(2×2)P/Fe(100) for the first time. P 1s core-level photoemission data were collected normal to the (100) surface and 45° off-normal along the [011] direction at room temperature. A close analysis of the auto-regressive linear prediction based Fourier transform and multiple-scattering spherical-wave calculations indicate that the P atoms adsorb in the high-coordination four-fold hollow sites. The P atoms bond 1.02 Å above the first layer of Fe atoms and the Fe-P-Fe bond angle is 140.6°. Additionally, it was determined that there is no expansion of the Fe surface. Self-consistent-field Xα scattered wave calculations were performed for the c(2×2)P/Fe(100) and the c(2×2)S/Fe(100) systems. These independent results are in excellent agreement with this P/Fe structure and the S/Fe structure previously published, confirming the ARPEFS determination that the Fe1-Fe2 interlayer spacing is contracted from the bulk value for S/Fe but not for P/Fe.
Formation and Properties of Roughened Poly-Si Electrodes for High-Density Drams
Authors: Liu H. W. , Lin Z. J. , Yu S. Y. , Huang S. C. , Cheng H. C.
Published: April 2011

A novel structure, based upon phosphorus-implanted poly-Si films treated with phosphoric acid (H3P 4) and the standard RCA cleaning process, has been demonstrated as the bottom electrodes of DRAMs' stacked capacitors. After the H3PO4 treatment and the RCA cleaning process, micro-islands are formed on the poly-Si surface of the electrodes. For the capacitors with this novel structure, the capacitance value is 18.17 fF/μm2 and the effective oxide thickness is 18.9 Å in comparison with conventional capacitors of 5.77 fFW/μm2 and 59.5 Å. The roughened poly-Si electrode can achieve a surface enlargement of 3.15 times. The leakage current density at +1.65V and −1.65V are 7.24 × 10−8 A/cm2 and −3.31 × 10−8 A/cm2, respectively, fulfilling the requirements of 256Mb DRAMs. Weibull plots of time-zero-dielectric-breakdown (TZDB) characteristics under ramping voltage test also show tight distribution and good electrical properties. It indicates that the phosphorus-implanted poly-Si films etched by H3PO4 and then cleaned with the standard RCA process can easily and simply increase the surface area and have good electrical properties fulfilling the requirements of 256Mb DRAMs and beyond.
Phase Selection by Competitive Growth in Ti/Al Thin Film Diffusion Couples
Authors: Wöhlert S. , Michaelsen C. , Bormann R.
Published: April 2011

The early stages of the solid-state reaction between Ti and Al are characterized by a distinct phase selection in favor of TiAl3. In order to understand the selection mechanism which leads to the absence of phases other than TiAl3, trilayers were prepared by sputtering with a layer of α2-Ti3Al or γ-TiA1 being sandwiched between the Ti and Al layers. The growth of TiA13 in competition with α2 or γ was observed by transmission electron microscopy investigations. Upon annealing, the α2 and the γ layers were consumed by growth of TiA13.

The results indicate that the absence of phases other than TiAl3 is not due to the existence of nucleation barriers for α2 and γ, but is caused by a growth selection. A kinetic model is presented which quantitatively explains the observed phase selection on the basis of different growth velocities which result from different diffusion rates in the competing phases.
SnO2:F Thin Films with High Fluorine Contents Produced by Spray Pyrolysis at Constant Substrate Temperature
Authors: Acosta D. R. , Zironi E. , Estrada W. , Montoya E.
Published: April 2011

Fluorine doped tin oxide thin films were prepared from solutions with high fluorine contents using the spray pyrolysis technique; the resulting films were studied by electron and X-ray diffraction methods; the resonant nuclear reaction (RNR) method was used to determine the final concentration of fluorine atoms in our films for different doping levels. Also, electrical and optical properties of SnO2:F films were measured and correlated with deposition and structural parameters obtained from X-Ray diffraction and electron microscopy studies.
In-Situ x-Ray Diffraction Analysis of TiSi2 Phase Formation from a Titanium-Molybdenum Bilayer
Authors: Cabral C. , Clevenger L. A. , Harper J. M. E. , Roy R. A. , Saenger K. L. , Miles G. L. , Mann R. W.
Published: April 2011

We demonstrate that the addition of a molybdenum interlayer between titanium and silicon enhances the formation of C54 TiSi2, without bypassing the formation of the C49 TiSi2 phase. In situ x-ray diffraction analysis during rapid thermal annealing, at a rate of 3 °C/s, was used to study the phase formation sequence of TiSi2 starting from a blanket bilayer of Ti on Mo on a polycrystalline Si substrate. It was shown, as in the case without the Mo layer, that the C49 TiSi2 phase forms first, followed by the C54 TiSi2 phase. The results were similar for undoped or arsenic, boron, and phosphorous doped polycrystalline silicon substrates. The temperature range over which the C49 phase is stable is reduced, on average, by 80 °C. The lower end of the range (appearance of C49) is increased by approximately 60 °C and the upper end of the range (disappearance of C49) is decreased by about 20 0C. The orientation of the C49 phase differs in that both the C49(131) and C49(060) orientations are observed, compared to the case without the Mo layer where only the C49(131) orientation is observed.
Phase Transformation and Microstructural Properties in Sputtered Vs. CVD WSi, Films
Authors: Dornenicucci A. , Dehm C. , Loh S. , Clevenger L. A. , Dziobkowski C. , Cabral C. , Lavole C. , Jorden-Sweet J.
Published: April 2011

CVD WSi, films produced by dichlorosilane reduction at 570°C and WSi, films sputter deposited at 50°C were characterized by in situ x-ray diffraction (IS-XRD), in situ resistivity (ISRes), in situ stress (IS-stress), ex situ/in situ transmission electron microscopy (EX/IS-TEM) and ex situ Auger electron spectrometry (EX-AES) over the temperature range 25–1100°C. The CVD films were crystalline after deposition, with columnar grains in the hexagonal phase and a Si:W atomic ratio of 2.6:1. The CVD films exhibited a sharp hexagonal to tetragonal phase transformation near 750°C. The final grain size was greater than the film thickness, with no evidence of voiding. Avrami analyses gave traditional curves with n values of 2 for the phase transition in the CVD films. In comparison, the sputtered films were amorphous as deposited (Si:W atomic ratio of 2.8:1 ) and crystallized to a different hexagonal phase microstructure than did the CVD films. The sputtered films showed a broad hexagonal to tetragonal phase transformation near 800°C, and a final grain size that was less than the fihn thickness with much voiding. A low Avrami exponent of 0.2 to 0.4 was obtained for the transformation of the sputtered films.