bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability of Ultra-Thin Gate Oxides with Boron Doped Polysilicon Gate Structures After Rapid Thermal Annealing
Authors: Zhang Bojun , Maher Dennis M. , Denker Mark S. , Ray Mark A.
Published: March 2011

We report a systematic study of dopant diffusion behavior for thin gate oxides and polysilicon implanted gate structures. Boron behavior is emphasized and its behavior is compared to that of As+ and BF2+. Dopant activation is achieved by rapid thermal annealing. Test structures with 100 Å, 60 Å and 30 Å gate oxides and ion implanted polysilicon gate electrodes were fabricated and characterized after annealing by SIMS, SEM, TEM, and C-V rpeasurements. For arsenic implanted structures, no dopant diffusion through a gate oxide of 30 Å thickness and an annealing condition as high as 1 100*C/1Os was observed. For boron implanted structures, as indicated by SIMS depth profiling, structures annealed at 1000*C/10s exhibit a so-called critical condition for boron diffusion through a 30 Å gate oxide. Boron dopant penetration is clearly observed for 60 Å gate oxides at an annealing condition of 1050 0C/10s. The flatband voltage shift can be as high as 0.56 volts as indicated by C-V measurements for boron penetrated gate oxides. However, 100 Å gate oxides are good diffusion barriers for boron at an annealing condition of 1100°C/10s. For BF2 implanted structures, the diffusion behavior is consistent with behavior reported in the literature.
Enhanced Boron Diffusion in Silicon with BF2-Implanted CoSi2 AS Diffusion Source and Under Rapid Thermal Annealing
Authors: Lin J. , Chen W. , Sultan A. , Banerjee S. , Lee J.
Published: March 2011

In this paper, B diffusion in Si with BF2-implanted CoSi2 as a diffusion source has been studied using SIMS analysis. The concentration-dependent diffusivity of B in single crystal Si is obtained by Boltzmann-Matano analysis. The data show that the B diffusivity in single crystal Si is more than one order of magnitude higher than the published data where a conventional B diffusion source (BN or B2H2) is used. Anomalous concentration dependence of the B diffusivity in Si for ultra-shallow B SIMS profiles was also observed. Possible physical mechanisms which involve implant damage in the Si substrate, the generation of point defects such as Si vacancies and interstitials during silicide formation, and B-defect interactions are discussed.
Using CoSi2 /Polysilicon Polycide Structure as a Gate Diffusion Source in Rapid Thermal Processing
Authors: Chen W. , Lin J. , Banerjee S. , Lee J.
Published: March 2011

Ion implanted CoSi2 as a gate doping source has been studied as a compatible process to the Silicide-As Diffusion-Source (SADS) process which has been widely considered for shallow source/drain junction formation. The effects of the polysilicon gate microstructure on diffusion behavior and the thermal stability of CoSi2 has been investigated. It has been found that CoSi2 formed on reoxidized polysilicon gates has poor thermal stability but requires short time to achieve degenerate doping near the polysilicon/gate oxide interface. On the other hand, CoSi2 formed on as-deposited amorphous silicon has excellent thermal stability but requires longer time to achieve degenerate doping near the polysilicon/gate oxide interface. The trade-off between the required thermal budget to achieve degenerate doping and thermal stability of the CoSi2/polysilicon gate structure will be discussed. In optimizing the process, our results indicated that reoxidized amorphous Si gates have both good thermal stability as well requiring short time to achieve degenerate doping. The thermal degradation of CoSi2 was found to have little effect on the gate oxide breakdown voltage.
Semi-Empirical Model for Boron Diffusion During Rapid Thermal Annealing of BF2 Implanted Silicon
Authors: Huang Tzu-Hsin , Kinoshita H. , Kwong D. L.
Published: March 2011

The mechanism of the enhanced diffusion of boron during rapid thermal annealing (RTA) of BF2-implanted Si has been investigated, and a diffusion model is accordingly developed for a wide range of implant and annealing conditions. Simulation results are in excellent agreement with experiments for BF2 implant doses from 2×1013 to 5×1015cm−2, implant energies from 6 to 45 keV, and annealing temperatures from 950 to 1100°C. This model not only accounts for the transient enhanced diffusion due to the annealing of point-defect clusters and dislocation loops, but also for the retarded diffusion due to dopant precipitation. All the parameters used in this model are analytically determined.
Nitrogen-Atom Bonding at Sio2/SI Interfaces in Metalinsulator-Semiconductor (MIS) Stacked Gates Made by Integration of Plasma Assisted Oxidation-Deposition and Rapid Thermal Processing
Authors: Ma Y. , YAsuda T. , Lucovsky G.
Published: March 2011

SiO2 thin films were deposited by remote PECVD on Si surfaces exposed to species generated in O2/N2 and O2/NH3 plasmas. The surface chemistry was studied by Auger Electron Spectroscopy, AES, and the electrical properties of the SiO2/Si interface by high frequency and quasi-static Capacitance-Voltage, C-V, measurements. The AES results showed that Ccontamination was removed by exposure to both plasma-excited gas mixtures, but that N-atoms were incorporated into the SiO2 film, and Si-N bonds were formed at the SiO2/Si interface. C-V measurements indicated that the Si-N bonding structure, rather than the N-atom concentration, is critical in determining the interface electrical properties. The effects of Rapid Thermal Annealing, RTA, on the electrical properties of these SiO2/Si interfaces were also studied.
Substrate Doping and Orientation Effects on Dielectric Growth on Siucon in a Nitrous Oxide Environment
Authors: Harrison H.B. , Dimitrijev S. , Sweatman D. , Misiura A. , Reeves G.K.
Published: March 2011

In this paper both the substrate doping concentration and single crystal silicon orientation are considered when dielectrics are grown on silicon in a nitrous oxide environment. Our initial preliminary findings show that for heavily doped subtrates thicker layers of dielectric result compared to their lower doped counterparts. Furthermore we find a crossover point of temperature for growth rate for <111> compared to <100>. We believe that the different growth rates are attributable to nitrogen build up at the dielectric interface.
Formation of TiSi2 During Rapid Thermal Annealing: In Situ Resistance Measurements at Heating Rates From 1°C/S to 100°C/S.
Authors: Ganapathiraman Ramanath , Koh S. , Ma Z. , Allen L. H. , Lee S.
Published: March 2011

In VLSI technology, there is interest in monitoring the sequence of phase formation of TiSi2 (c-Ti ⇒ a-TiSi ⇒ C49 TiSi2 ⇒ C54 TiSi2), with the prospect of reducing the temperature of formation of the stable C54 TiSi2 phase. In this study, phase formation characteristics of TiSi2 during rapid thermal annealing(RTA) of Ti-Si bilayers are investigated by means of in situ four point probe resistance measurements. Ex situ X-ray diffraction(XRD) was used for phase identification and characterization. Results indicate that the same multi-step sequence of transformations precede the formation of the C54 TiSi2 phase for heating rates from 1°C/s to 100°C/s. Also, all intermediate and metastable phases which occur at l°C/s also occur at 100°C/s. Temperature dependence and kinetics of the C49 TiSi2 and the C54 TiSi2 phase formation were studied over a wide range of heating rates. Activation energies estimated for the two processes were ∼2eV and ∼5eV respectively. Finally, a new Electrical Thermal Annealing(ETA) technique for heating at rates up to 30000°C/s is introduced. Preliminary in situ resistivity measurement results of TiSi2 formation at these high heating rates are also presented.
Rapid Titanium Silicidation: A Comparative Study of two Rta Reactors
Authors: Bariatro M. , Fontes A. , Quacchia J. Q. , Furlan R. , Santiago-Aviles J. J.
Published: March 2011

In this work we studied titanium silicide formation by cosputtering onto silicon dioxide. Samples deposited with various (Si/Ti) atomic ratios were analyzed by Rutherford Backscattering Spectrometry (RBS). Isocronal annealings were conducted by means of Rapid Thermal Processing (RTP) in two types of furnaces: a vacuum and an atmospheric pressure (argon). Phase formation was monitored by resistivity measurements, X-Ray diffraction (XRD), and Scanning Electron Microscopy (SEM). It is observed that the final phase formation follows the thennodynamic equilibrium diagram, determined by stoichiometry, occurring at 800°C for the vacuum furnace, and at 900°C for the atmospheric RTP furnace. Sequential thermal treatments indicated the formation of TiSi2-C49 and/or TiSi after 400°C.
X-Ray Absorption Studies of Ti/Polymer and Cr/Polymer Interfaces
Authors: Opila R. L. , Konstadinidis K. , Ibidunni A. O. , Davenport A. J. , Isaacs H. S.
Published: March 2011

The interface formed between metals, Ti and Cr, and polymers, epoxy and triazine, have been studied, nondestructively, using x-ray absorption spectroscopy. The metals were sputtered onto the polymer surfaces. Titanium reacts extensively, up to Ti thicknesses of 100 Å while Cr remains primarily metallic. In situ heating at 200°C increases the extent of reaction for both metals. Heating has a greater effect on metal/epoxy interfaces than metal/triazine. Titanium and Cr were ion implanted into the polymer in order to determine the interactions of isolated metal atoms with the polymer. Titanium and Cr appear to form oxides as the final reaction product, and the Ti is tetrahedrally coordinated.
In Situ Kinetics and Thermodynamics of Polymer Adsorption on Chemically Modified Silica
Authors: Zazzera Lawrence A. , Tirrell Matt , Evans John F.
Published: March 2011

In situ Fourier transform infrared (FT-IR) spectroscopy in an attenuated total reflection mode has been employed to examine the chemical modification of ozone-cleaned, native oxide on single crystal Si(100). This planar model for silica is subjected to solution modification using silane reagents which impart variable polarity to the modified surface through different termini of the modifier. These chemical modifications are followed in real time using FT-IR as a diagnostic of surface preparation; either by examining the appearance of a band for an IR chromophore of the modifier which is attached, or by monitoring the loss of the surface silanol groups consumed in the reaction. Following modification, polymer solutions (acrylates, siloxanes) are introduced into the cell and the dynamics of the adsorption followed by a chromophore of the polymer. Not only can the total amount of bound polymer be determined, but also in cases of strong interactions between the polymer and surface modified (e.g. OH... O=C) the bound fraction can be determined. Correlations between surface polarity and these experimentally determined quantities give insight in to the configuration(s) of the adsorbed polymers.
Solvent Induced Morphological Changes to Polycarbonate
Authors: Briscoe B. J. , Stuart B. H. , Thomas P. S.
Published: March 2011

The interface shear properties of thin bisphenol-A-poly(carbonate) films are measured and interpreted in terms of the effects of the morphology induced by solvent plasticisation. The variations in the interface rheology are discussed in terms of the Eyring stress modified thermally activated flow model. The changes in the molecular architecture, induced by plasticisation, are also examined using vibrational spectroscopy. A correlation is made between the proposed mechanism for microshear and the conveyed morphological properties of the polymer film at the molecular level.
Thickness Measurements and Optical Characterization of Thin Polymer Films
Authors: Wall J. F. , Brumfield J. C. , Murray R. W. , Irene E. A.
Published: March 2011

Polyphenylene oxide (PPO) films have been investigated as protective coatings and as selective inhibitors to permeants.1,2,3 These films have been shown to be passivating materials and therefore are potentially interesting for a variety of applications. It is important for further applications to be able to measure the thickness of thin films by nondestructive techniques, which is the subject of this report. In this study PPO films of various thicknesses were electrodeposited on highly oriented pyrolytic graphite (HOPG) electrodes and examined by spectroscopic ellipsometry (SE) and atomic force microscopy (AFM). These techniques are combined to yield the thickness of the polymer film and the optical properties of the HOPG substrate and the PPO overlayer in the visible and near ultraviolet spectral region.
Characterization of the Interphase in Model Associative Polymer/Titanium Dioxide and Polystyrene Latex Systems
Authors: Heck Connie S. , Roberts J. E.
Published: March 2011

The adsorption behavior of model associative polymers in aqueous titanium dioxide (TiO2) and polystyrene latex (PS) particle dispersions has been studied using liquid-state Nuclear Magnetic Resonance (NMR) and a modified serum replacement technique (SRT). The structure of the associative polymer is a linear, water soluble, A-B-A block copolymer with a polyethylene oxide backbone and hydroxyl (H) or hexadecyl (C16H33) endgroups.

Absolute intensity NMR measurements allow the determination of the adsorbed polymer configuration at the solid-solution interface and adsorption isotherms for comparison to the SRT results. Both the SRT and NMR results demonstrate that the adsorption/desorption of the C16 and H polymers is strongly affected by the substrate. For the polymer/PS particle systems, there is good agreement in complete surface saturation values for the SRT and NMR methods. In the polymer/TiO2 systems, the H polymer plateau as determined by NMR differs slightly from that determined by SRT. For the C16/TiO2 system the interpretation is less straightforward. Either the NMR saturation value is at least double that of the SRT value or the C16 and H polymers have very similar isotherms by NMR. This would suggest that on TiO2 the effect of the hydrophobe is minimal. For all the polymers the polymer/particle interaction on PS is strong and desorption is difficult while on TiO2 it is weak and completely reversible. A pancake-to-brush conformation change on the PS surface is evident for the C16 polymers and probably for the H polymer as well. The H polymer seems to form a multi-layered structure on PS from the NMR and laser light scattering results. The contribution of the hydrophobe and the effect of increasing the backbone molecular weight are clearly illustrated.
Interfacial Water Transport and Embrittlement in Polymer-Matrix Composites
Authors: Lekatou A. , Qian Y. , Faidi S. E. , Lyon S. B. , Islam N. , Newman R. C.
Published: March 2011

Disordered glass microsphere-epoxy composites have been used in a study of diffusional, electrical and mechanical effects of interfaces in polymer-matrix composites exposed to pure water. Mass gain measurements on composites manufactured from 10 μm silane-treated microspheres indicate initial near-Fickian diffusion with water saturation times on the order of 500 h. However, electrical measurements indicate water transport at rates at least 100 times more rapid. This behaviour is interpreted in terms of a cellular microstructure with areas of low cross-link density separating highly cross-linked areas. Rapid water transport can thus occur in areas of low cross-linking, even without the contribution of connected clusters of particles where rapid interfacial water transport occurs substantially ahead of the main diffusion front. Reductions in ultimate tensile strength and fracture energy in dry and water-saturated tensile test specimens are observed with increasing volume fraction of glass spheres but with a distinct plateau between about 6% and 12% Vf. This can be explained in terms of secondary cracking below the percolation threshold which causes toughening of the composite. However, a few % above pc (≍ 16%), most particles belong to the percolating cluster and the primary crack can grow without hindrance.
Plasma Polymerization of Allylamine onto Pan-Based Carbon Fibers
Authors: Smiley R. J. , Delgass W. N.
Published: March 2011

The plasma polymerization of allylamine onto PAN-based carbon fibers has been investigated by XPS and SEM. Fiber surfaces were cleaned and oxidized by treating in an O2 plasma for 5 minutes. XPS characterization of pretreated samples showed surfaces functionalized with COH, C=O, and COOH species. Fibers were coated with poly(allylamine) by introducing a monomer-saturated stream of Ar gas into the plasma chamber and reacting for 2–30 minutes. Some samples were further treated in an O2 plasma to determine the stability of the polymer coating. N(1s) spectra from the fiber surfaces showed two nitrogen peaks at 399.9 eV and 400.7 eV, which may be assigned to amine and amide groups, respectively. C(1s) spectra showed a decrease with treatment in the amine carbon peak at 287.2 eV and a corresponding increase in the peak at 288.7 eV, assigned to carboxyl and/or amide carbon. The increase in higher binding energy carbon corresponded with an increase in the 400.7 eV N(1s) peak and gave evidence for the conversion of amines to amides. Total O(1s) intensity initially decreased following 2 minutes of allylamine treatment but increased with further treatment. In addition to the carbon fiber samples, a silica wafer was coated and analyzed by XPS. Quantitative XPS results revealed that all the nitrogen present on the surface was in the form of amine and not amide species. Oxygen in the form of carboxyl species was also present on coated silica surfaces. Most likely, oxygen dissolved in the allylamine monomer was carried into the plasma chamber by the Ar gas. Comparing the silica wafer with the fiber samples revealed treatments were strongly sample dependent. Even after only 2 minutes of treatment, fiber samples showed the presence of amide and substituted amide species. SEM revealed coatings filled in the fiber grooves and left clumps of material on the surface. Micrographs of fibers treated for longer times revealed surfaces covered with particles < 0.25 μm in diameter. Finally, the XPS N(1s)/C(1s) and O(1s)/C(1s) intensity ratios indicated that some polymer remained on the fiber surface even after 15 minute post O2 plasma treatment. These experiments illustrate that plasma polymerization can be effective for functionalizing carbon fiber surfaces, but that optimization of conditions is necessary to improve wetting and control amine/amide functionality.
Electro-Active Polymer-Ceramic Composites for Piezoelectric and Pyroelectric Applications
Authors: Dias C. , Das-Gupta D. K.
Published: March 2011

Present work reports the results of a study of characterization of dielectric, piezoelectric and pyroelectric properties of calcium modified lead titanate ceramic/poly (vinylidene-trifluorethylene) composites with zero-three connectivity. The paper also presents a theoretical model to optimize such properties with respect to particle size, dielectric constant and composition.
Ultimate Properties of Polymer Chains
Authors: Adams W. Wade , Pachter Ruth , Haaland Peter D. , Horn Thomas R. , Wierschke Scott G. , Crane Robert L.
Published: March 2011

New polymers with exceptional properties are needed for applications in high-performance structures, novel electrical, optical and electro-optical devices, and for multi-functional smart materials. Concurrently, new computational capabilities and methods for properties prediction and analysis have enabled the study of a variety of polymer chain architectures to examine the principles that govern their high-performance properties. By semi-empirical and ab initio computational methods, flexible, stiff-chain, rigid-rod, and biological structures could be analyzed. Single chain molecular stress-strain curves for axial tension and compression were calculated, and the strain dependence of the molecular modulus and vibrational frequencies were compared to measurements of molecular deformation, such as IR and Raman spectroscopy. However, of special interest is the distinctly different response of alpha-helical biopolymer chains to strain. Indeed, in this study we compare on a theoretical basis the ‘spring-like’ microscopic mechanical response of alpha-helical biopolymers having a reinforcing intra-molecular hydrogen bonding network to analogous synthetic extended chain polymers, especially poly(para-phenylene terephthalamide) (PPTA) [KEVLARTM]. The theoretical verification of the absence of compressive buckling in alpha-helical biopolymer chains rationalizes the molecular elasticity and resistance to ‘kinking’ of those strands, manifested by the prevalence in Nature for coiled coils. The understanding of the structure-tofunction relationship in biopolymers explaining the role of the alpha-helix in these systems as a requirement for superior compressive mechanical properties, may enable new guidance for the synthesis of motifs consistent with molecular frameworks optimized by Nature.
Characterization Of Capillary-Optic Materials For Use In X-Ray Lithography
Authors: Dozier C. M. , Bell M. I. , Newman D. A. , Freitag R. K. , Brown D. B. , Rosenstock H. B.
Published: March 2011

Capillary optics appear to permit the fabrication of practical collimator systems for laserdriven x-ray point sources. With such collimators, the illumination of wafers can meet the tight requirements for lithographic patterning of sub-micron device structures. However, the use of x-radiation with photon energies between 800–1200 eV makes capillaries of conventional silica-based glass capillaries marginal due to their low reflectivity. The reflectivity of various materials were examined with the goal of finding alternate glasses, elements for doping glasses or surface coatings that may enhance these collimators for lithographic applications. Coating capillary surfaces with more reflective materials may be the most viable method for improving the radiation transport properties for capillary optics to be used in x-ray lithography.
Mask Technology For X-Ray Nanolithography
Authors: Schattenburg M. L. , Carter J. , Chu W. , Fleming R. C. , Ghanbari R. A. , Mondol M. , Polce N. , Smith Henry I.
Published: March 2011

In this report we describe a system of technologies we have developed for fabricating, patterning, and replicating x-ray masks with linewidths as fine as 50 nm (0.05 μm). This effort has evolved into a fairly routine service supporting a growing community of researchers at MIT interested in fabricating sub-micron and nanometer scale structures and devices. Strong, transparent, silicon-rich nitride (SiN) membranes bonded to optically-flat Pyrex rings and patterned with gold absorbers form the basic x-ray mask structure. We have recently completed the installation of a vertical thermal reactor (VTR) for the deposition of SiN coatings. Results indicate superb film uniformity, decreased defect counts, and increased strength over previously available nitrides. Patterning of the masks is performed at an off-site location by electron-beam lithography followed by development and gold electroplating at MIT. We describe a new fountain plating bath and mask chuck which allows us to obtain clean, uniform gold films of low stress. Once completed, the so-called “master” masks are replicated onto new x-ray mask substrates which are then processed into “daughter” masks. The resulting polarity-reversed patterns are required in order to achieve the desired pattern in positive resist when printed onto substrates. We will describe our in-house built x-ray aligner which features a high-power electron bombardment source and SiN vacuum isolation window to achieve exposures in a helium environment.
Interfacial Structure of Lattice Mismatched bcc(110)/bcc(110) Transition Metal Superlattices
Authors: Fullerton Eric E. , Mini S. M. , Bommannavar A. S. , Sowers C. H. , Ehrlich S. N. , Bader S. D.
Published: March 2011

We present structural characterizations of a series of sputtered Fe/Nb and V/Nb superlattices by high-angle x-ray diffraction. Diffraction scans were performed with the scattering vector at various angles (χ) with respect to the layers. χ=0° diffraction spectra (normal to the layers) were fitted to a general structural model to determine the (110) lattice strains, interfacial disorder and interdiffusion. χ>0° spectra probe the lattice strain of the individual layers and the in-plane interfacial coherence. Both systems form incoherent interfaces above a critical modulation wavelength (ΛC). At ΛC, the Fe/Nb system undergoes a crystalline-to-amorphous transition while the V/Nb forms in-plane coherent interfaces.
Synchrotron Radiation Induced Surface Reactions: A New Method for Metal Film Deposition on Semiconductors
Authors: Zanoni Roberto , Piancastelli Maria Novella
Published: March 2011

A systematic investigation of the adsorption properties of several organometallic compounds on silicon surfaces is reported. In this framework, a new method to deposit thin metal films on silicon surfaces is described, which is based on a synchrotron radiation induced photodecomposition reaction. The precursors are metal carbonyls adsorbed on single-crystal Si surfaces in ultrahigh vacuum conditions. Irradiation of these adsorbatesubstrate systems with unmonochromatized synchrotron radiation (“white light”) induces a chemical reaction leading to a thin metal film on the surface. This process has been monitored in situ by photoemission. The fingerprint for the film formation is the appearance of a clear Fermi edge in the valence band. We have been able to deposit thin films of Mo, W and Fe on Si(111) surfaces. This method offers several advantages over traditional techniques, and namely the mild conditions and the limited number of process steps. An intriguing future development under testing is the possibility of creating ordered patterns on the surface.
Diffraction Anomalous Fine Structure: A New Technique for Probing Local Atomic Environment
Authors: Pickering Ingrid J. , Sansone Michael , Marsch James , George Graham N.
Published: March 2011

Diffraction anomalous fine structure (DAFS) is the fine structure in the intensity of an X-ray diffraction peak in the vicinity of an absorption edge. DAFS is measured by monitoring the intensity of a diffraction peak as a function of the incident X-ray energy as it is scanned through an absorption edge. It combines the short range structural sensitivity of X-ray absorption spectroscopy with the long range periodicity of X-ray diffraction, and can provide structural information which is not available from these techniques alone, or in combination. We present a methodology which allows extraction of a specific X-ray absorbance spectrum from the DAFS spectrum, and illustrate it for KMnO4. We also demonstrate the ability of DAFS to separate the contributions to the X-ray absorption spectrum of the tetrahedral and octahedral cobalt sites in the spinel Co3O4.
X-Ray Observation of Stress Gradients and Precipitation in Passivated AL-0.5% Cu Films
Authors: Besser Paul R. , Brennan Sean , Bravman John C.
Published: March 2011

Grazing incidence x-ray scattering has been used with a synchrotron source to characterize the stress gradients during thermal cycling in 1.0 μm thick Al-0.5%Cu films passivated with silicon nitride. The films were cycled between room temperature and 400°C. The stress-temperature behavior is quantitatively similar to that measured for unpassivated films. The presence of an inhomogeneous strain is documented at low temperatures. The dissolution and precipitation of Al2Cu is suggested as an explanation for the gradients and asymmetric x-ray peak broadening.
High Resolution Photoelectron Study of the Optimum Oxygen Doping Levels in High TcSuperconductors
Authors: Kelley R. J. , Cai X. C. , Ma Jian , Larbalestier D. C. , Onellion M.
Published: March 2011

The materials and electronic properties of the new cuprate superconductors are critically dependent upon both the oxygen stoichiometry and annealing history of the material. Improving Jc, Tc, and determining the underlying mechanism of superconductivity depend on a better understanding of these effects. In the study of Bi2Sr2CaCu2O8-δwe have combined standard material characterization techniques with high resolution angle resolved photoemission spectroscopy and resonant photoemission spectroscopy to illuminate these issues. Specifically, we make high quality single crystals of BSCCO and then anneal in different atmospheres and pressures. We correlate this withc-axisresistivity, a, b-plane resistivity, and resonant photoemission spectroscopy. In this way we can explain the macroscopic transport properties in terms of the electronic properties of the material determined from photoemission. We find that we can change the c-axis resistivity from non-metallic to metallic by adding oxygen and that this correlates with increased oscillator strength in thec-axisdirection at the Fermi level.
Electronic Structure of Cr2O3 Studied by Photoemission Spectroscopies
Authors: Li Xiaomei , Henrich Victor E. , Saitoh Tomohiko , Fujimori Atsushi
Published: March 2011

The electronic structure of single-crystal Cr2O3 has been studied by Cr 2p core-level XPS and valence-band UPS spectroscopies. A cluster configuration-interaction analysis was applied to investigate the nature of the satellite in the Cr 2p core-level photoemission spectrum. It is argued that the satellite can be understood as a charge-transfer satellite, and Cr2O3 is found to be situated at the boundary between the Mott-Hubbard and the charge-transfer regimes. The values of the charge-transfer energy, Δ, the Coulomb correlation energy, U, and the ligand 2p-cation 3d hybridization energy, T, found from fitting the Cr 2p XPS spectrum were also used to analyze the valence-band UPS spectrum. The comparison between the experimental spectrum and the spectrum from theoretical fitting is fair.
In-Situ Quasi-Real Time Observations of the Deformation of α-Brass Bicrystals via Synchrotron X-Ray Topography
Authors: Zeng Z. , Rek Z. , Bilello J. C.
Published: March 2011

Real-time studies of the deformation behavior of a-brass bicrystals were conducted via in-situ synchrotron white beam X-ray topography (SWBXRT). The object of this work was to understand the role of internal interfaces such as grain boundaries, in controlling the mechanical behavior of materials. A brass bicrystal, in which the two grains made 5° of tilt and 11° of twist with respect to each other was grown by the Bridgman method. Observations were performed by straining the bicrystal in a microtensile stage while stop-action X-ray diffraction topographs were taken. Slip initiated in the grain with the most favorable Schmid factor at a stress level of 1.4MPa which was 5% of the macroyield stress. Since the grain boundary acted as a barrier to slip, the next grain did not slip until the dislocation pile-up at the grain boundary reached a critical value.
Anisotropic Phase Separation in Amorphous Fe-Ge Alloys
Authors: Regan Michael J. , Bienenstock Arthur
Published: March 2011

Magnetron sputtered amorphous FexGe100-x films have been examined with anomalous small-angle x-ray scattering (ASAXS) in an attempt to characterize composition fluctuations which have been previously reported in this system. Films grown under various deposition conditions have been studied, with the scattering vector both in and oblique to the plane of the films, to search for anisotropy. By manipulating the deposited power flux and rates of growth, films which have the same composition can be grown to different states of phase separation. The total correlation functions have been calculated from the oblique scattering experiments. The anisotropy can be successfully modeled as a close-packing of oriented prolate ellipsoidal particles, with the elongated axis along the direction of film growth. A method for using these measurements to determine the compositions of the phase-separating species has been developed and utilized. The results indicate phase separation into a-Ge and a-FeGe2 for the a-FexGe100-x (x<33) alloy.
X-Ray Absorption Spectroscopic Study of Copper in an Amorphous Copper-Silicate: Chrysocolla
Authors: McKeown David A.
Published: March 2011

XANES and EXAFS data indicate that chrysocolla does not contain domains of Cu-metal or Cu-oxides as previously hypothesized, but is most similar to dioptase, a chemically homogeneous crystalline Cu-silicate. The first shell around Cu in chrysocolla is similar to that in dioptase, indicating Cu is coordinated by four oxygens. However, the second shell around Cu in chrysocolla is significantly different than the second shell surrounding Cu in dioptase. The larger amplitude second shell for chrysocolla compared with dioptase is found to be primarily due to differences in the Cu-Cu environments between these two materials.
X-Ray Absorption Spectroscopy of Nitrogenase Mo-Fe Protein
Authors: Chen J. , Christiansen J. , George S. , Tittsworth R. , Hales B. , Campobasso N. , Bolin J. , Cramer S. P.
Published: March 2011

We have studied both the atomic and electronic structures of nitrogenase Mo-Fe proteins using EXAFS and L-edge spectroscopy. The Mo and Fe K-edge EXAFS data show not only 2.37, 2.70, 2.29, and 2.63 Å first shell Mo-S, Mo-Fe, Fe-S, and Fe-Fe distances, but also 3.8, 4.3 and 5.1 Å second shell Fe-Fe, Fe-S, and Mo-Fe interactions. These observed distances are consistent with recent crystallographic models for the M-center. The average Mcenter distances have been defined with unprecedented accuracy. The nitrogenase Fe L-edge spectra have been obtained for the first time, and the result suggests that the Fe exists in both Fe2+and Fe3+states.
Ionic Transport in Silicate Glasses Modelled from the Local Structure
Authors: Greaves G. Neville , Baker G. J. , Dent A. J. , Oversluizen M. , Ngai K. L.
Published: March 2011

Comprehensive studies using X-ray Absorption Fine Structure (XAFS) spectroscopy of the local environments in oxide glasses of alkalis like Na point to the existence of channels of modifying oxide within the glass forming network - a Modified Random Network or MRN. It has been proposed that these are the primary pathways for ionic conduction. Such microsegregation demands a high alkali coordination for non-bridging oxygens. This has now been confirmed from analysis of the O near edge XAFS of silica and sodium disilicate glass. Dielectric relaxation in oxide glasses provides considerable evidence for the cooperative action of alkali ions. The MRN has been used to develop specific microscopic models for ionic transport based on XAFS and incorporating correlated ionic movement. These quantitatively predict the ionic conductivity of silicate and aluminosilicate glasses and the compositional dependence of the activation energy with alkali concentration.
High Resolution Tem Studies of Defects Near Si-SiO2 Interface
Authors: Mazur J. H. , Washburn J.
Published: March 2011

Small defects with habit parallel to {100} and {311} matrix planes were observed using high resolution transmission electron microscopy (HREM) within 100 nm from the Si-Si02 interfaces after one step oxidation in dry O2 at 900°C, 1000°C and 1150°C of Czochralski (CZ) grown [100] p type boron doped, 1.5 − 20 Ω cm Si wafers with concentrations of oxygen1.4 × 10 18cm−3 and carbon 4. − 10. × 10 16 cm−3.The defects were less than 10 nm wide and I nm thick. The {100} and {311} defect are interpreted tentatively as thin silica plateletes and {311} stacking faults respectively. Distribution of defects near the interface was random although their density appeared to be lower for higher oxidation temperatures. It is not yet clear whether the defects were formed during the oxidation treatments or were present near the surfaces of the asreceived wafers.
Electron Microscopy of Semiconductors Reconstructed Surfaces
Authors: Petroff Pierre M.
Published: March 2011

Surface sensitive transmission electron microscopy (SSTEM) and reflection electron microscopy (REM) have been used to analyze the Si (111) 1×1 → 7×7 surface reconstruction. The SSTEM and transmission electron diffraction results for the Si (111) 7×7 surface are interpreted using several possible “surface dislocation” models. The SSTEM and REM techniques have also been applied to the GaAs (100) MBE deposited surfaces. The rough surface topography for the c(4×4) reconstructed surface is attributed to surface steps motions and bunching upon interruption of the MBE deposition.
Tem Observation of defects in InGaAsP and InGaP Crystals on GaAs Substrates Grown by Liquid Phase Epitaxy
Authors: Ueda O. , Isozumi S. , Komiya S. , Kusunoki T. , Umebu I.
Published: March 2011

Defects in InGaAsP and InGaP crystals lattice-matched to (001)-oriented GaAs substrate successfully grown by liquid phase epitaxy, have been investigated by TEM and STEM/EDX. Typical defects observed by TEM are composition-modulated structures, dislocation loops, non-structural microdefects, and stacking faults.
Epitaxy of Bcc and Hexagonal Metals on Fcc(001) Substrates
Authors: Grovenor C.R.M. , Smith D.A.
Published: March 2011

A variety of bcc and hexagonal metals have been deposited onto fcc(001) surfaces held at between 150 and 350°C. The epitaxial relationships developed between deposit and fcc substrate have been investigated , and the application of current theories of the energy of interphase boundaries to explaining these results is critically discussed.
Microanalysis with high Spatial Resolution
Authors: Batson P. E. , Grovenor C. R. M. , Smith D. A. , Wong C.
Published: March 2011

Elemental microanalysis, using x-rays and electron energy loss scattering, has been shown to be possible with electron beam probe sizes down to 0.5nm. This paper will discuss some practical problems, such as specimen drift, signal magnitude, and probe-specimen interaction when the probe is made very small. These problems have arisen in two studies: 1) an investigation of as segregation in poly-crystalline Si and 2) imaging of metal spheres with surface and bulk plasmon inelastic scattering.
Electron Microscopy and Analysis at Higher Voltages: The Philips EM430 300kV Microscope
Authors: Hagemann Peter N. , Fahy John S.
Published: March 2011

The past decade has seen the evolution of the Philips TEM from a “microscope”to an integrated microanalytical system. A current example of this trend is the EM 420*, an instrument whose design concepts are reflected in the most recently offered TEM, the compact, high kV, high resolution EM430.
Reversible Photo-Induced Currents in Epitaxial Pb(Zr0.52Ti0.48)O3 Thin Films
Authors: Lee J. , Esayan S. , Prohaska J. , Safari A.
Published: March 2011

The pyroelectric and photogalvanic effects have been studied extensively in epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin films. For the first time, photo-induced currents, which were completely reversible by electrical voltage, were observed in ferroelectric thin films. The photo-induced currents exhibited transient and steady state components. The transient component, in turn, consisted of two components with fast (<1 µs) and slow (∼hours) relaxation times. The mechanisms of the photo-induced currents in PZT films and their possible application in non-destructive readout ferroelectric memory are discussed.
Reactive ion Etching of Pt/PbZrxTi1−xO3/Pt Integrated Ferroelectric Capacitors
Authors: Van Glabbeek J.J. , Spierings G.A.C.M. , Ulenaers M.J.E. , Dormans G.J.M. , Larsen P.K.
Published: March 2011

Dry etching of a Pt/PbZrxTi1−xO3/Pt (Pt/PZT/Pt) ferroelectric capacitor stack with CF4/Ar plasmas with a reactive ion etching process for the fabrication of micrometer-sized integrated ferroelectric capacitors is described. The etch rate for both Pt and PZT is determined as a function of the process settings: Power, pressure and CF4-Ar gas flow ratio. A chemical enhancement of the etch rate is found for PZT. It is shown that it is possible to etch the Pt/PZT/Pt ferroelectric capacitor stack in a CF4/Ar plasma in a single lithographic process using patterning by photoresist masking. Redeposition processes occurring during etching are described.
Deposition, Structural Characterization, and Broadband (1KHz-40GHz) Dielectric Behavior of BaxTi2-xOy Thin Films
Authors: Liu W.-T. , Cochrane S. , Beckage P. , Knorr D. B. , Lu T.-M. , Borrego J. M. , Rymaszewski E. J.
Published: March 2011

An ion assisted deposition technique, called Reactive Partially Ionized Beam (RPIB) deposition, was used to prepare amorphous BaxTi2-xOy thin films at a low substrate temperature (<60°C). The stoichiometry of the films varied from ×=l.0 for BaTiO3 to ×=0.2 for Ti-rich films. The optical, thermal, and broadband electrical properties of this class of thin film dielectrics were systematically studied. A lμm BaxTi2-xOy film is optically transparent with a band gap of 4.6eV. Both transmittance and bandgap decrease when the films are increasingly enriched with Ti. The Ti rich films remain amorphous at 600°C while the stoichiometric BaTiO3 crystallizes into the perovskite structure. Annealed Ti rich films are thermally stable (>700°C) with low leakage (<0.lμ/cm2 at 0.5MV/cm) and moderately high dielectric constant (εr = 15-35). Polycrystalline BaTiO 3 deposited at 600°C on a Pt/Ta/SiO2/Si substrate has an εr = 400. Capacitor structures with various metallizations were used to evaluate the dielectric properties, such as breakdown strength, leakage, εr and tanδ from DC to 600MHz. A generic test vehicle was designed and fabricated to extend the frequency domain characterization of the dielectrics up to 40GHz. No dispersion of εr was observed in this frequency range for amorphous BaxTi2-xOy.
Correlations Among Degradations in Lead Zirconate Titanate thin Film Capacitors
Authors: Yoo In K. , Desu Seshu B. , Xing Jimmy
Published: March 2011

Many attempts have been made to reduce degradation properties of Lead Zirconate Titanate (PZT) thin film capacitors. Although each degradation property has been studied extensively for the sake of material improvement, it is desired that they be understood in a unified manner in order to reduce degradation properties simultaneously. This can be achieved if a common source(s) of degradations is identified and controlled. In the past it was noticed that oxygen vacancies play a key role in fatigue, leakage current, and electrical degradation/breakdown of PZT films. It is now known that space charges (oxygen vacancies, mainly) affect ageing, too. Therefore, a quantitative ageing mechanism is proposed based on oxygen vacancy migration under internal field generated by either remanent polarization or spontaneous polarization. Fatigue, leakage current, electrical degradation, and polarization reversal mechanisms are correlated with the ageing mechanism in order to establish guidelines for simultaneous degradation control of PZT thin film capacitors. In addition, the current pitfalls in the ferroelectric test circuit is discussed, which may cause false retention, imprint, and ageing.
Ferroelectric La-Sr-Co-O / Pb-Zr-TI-O / La-Sr-Co-O Heterostructures on Silicon: Reliability Testing
Authors: Ramesh R. , Sands T. , Keramidas V. G. , Fork D.K.
Published: March 2011

We report results of pulsed electrical testing of ferroelectric Pb0.9La0.1Zr0.2Ti0.8O3 thin film capacitors with symmetrical La-Sr-Co-O top and bottom electrodes at room temperature and at 100°C. They have been grown on [001] Si with a Yttria stabilized zirconia (YSZ) buffer layer. A layered perovskite “template” layer (200-300Å thick), grown between the YSZ buffer layer and the bottom La-Sr-Co-O electrode, is critical for obtaining the required orientation of the subsequent layers. When compared to the capacitors grown with Y-Ba-Cu-O (YBCO) top and bottom electrodes, these structures possess two advantages : (1) the growth temperatures are lower by 60-150°C; (ii) the capacitors show a large remnant polarization, δP, ( δP = switched polarization -non-switched polarization), 25-30 μC/cm2, for an applied voltage of only 2V (applied field of 70kV/cm). The fatigue, retention and aging characteristics of these new structures are excellent at both room temperature and at 100°C.
Plasma Enhanced Metalorganic Chemical Vapor Deposition of Conductive Oxide Electrodes for Ferroelectric BaTiO3 Capacitors
Authors: Zhang Jiming , Cui Guang-Ji , Gordon Douglas , Buskirk Peter Van , Steinbeck John
Published: March 2011

Thin film heterostructures of BaTiO3/YBa2Cu3O7-x (YBCO) and BaTiO3/LaxSrl-xCoO3 (LSCO) have been prepared by a novel single liquid source plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) process. Both YBCO and LSCO are conductive oxides with perovskite structure and lattice parameters closely matched to BaTiO3. YBCO films were found to deteriorate after the deposition of BaTiO3 under the PE-MOCVD conditions as revealed by X-ray diffraction and electrical characterization. LSCO thin films prepared by PE-MOCVD have a mirror-like surface, exhibit low electrical resistivity (p = 200 μΩ-cm at room temperature) and are robust to BaTiO3 deposition. These characteristics make LSCO a promising electrode material for ferroelectric capacitors.
Growth, Microstructures and Optical Properties of KNbO3 Thin Films
Authors: Graettinger Thomas M. , Morris P. A. , Woolcotit R. R. , Zumsteg F. C. , Chow A. F. , Kingon A. I.
Published: March 2011

Potassium niobate, KNbO3, possesses high nonlinear optical coefficients making it a promising material for frequency conversion into the visible wavelength range. While epitaxial thin films of KNbO3 have been reported [1,2], only limited data exists concerning the optical loss mechanisms and nonlinear optical properties of these films. In this study, epitaxial thin films of KNbO3 have been grown using ion beam sputter deposition and evaluated in terms of their microstructures and optical properties. Characterization of the microstructures of these films includes the in-plane epitaxial relationship to the substrate. The relationships between the growth parameters and microstructures developed to the indices of refraction and the optical losses (absorption and scattering) are discussed.
Aerosol Routes to Perovskite Phase Mixed Metal Oxides
Authors: Chandler C.D. , Powell Q. , Hampden-Smith M.J. , Kodas T.T.
Published: March 2011

Sub-micron sized metal oxide particles were formed via aerosol decomposition using single-source mixed metal-organic precursors specifically designed to decompose at low temperatures. The advantage of these single-source precursors over mixtures of individual precursors is that each particle contains a fixed stoichiometry and molecular level homogeneity. Furthermore, the loss of volatile intermediates (such as PbO) may be avoided. Aerosol processing routes can produce uniform sub-micron sized powder that can be sintered at low temperatures for various thin film and membrane applications. The single-source precursors were prepared in pyridine by reaction of divalent metal α-hydroxycarboxylates of general empirical formula A(O2CCMe2OH)2 (where A = Pb, Ca, Sr, Ba; Me = methyl) with metal alkoxides (for example, Ti(O-i-Pr)4) with the elimination of two equivalents of alcohol. These species were then hydrolyzed in solution and yellow powders were isolated by removal of the pyridine solvent in vacuo. These powders were dissolved in water and used to prepare mixed metal oxide powders via spray pyrolysis. Phase-pure submicron-sized particles of PbTiO3 and BaTiO3 were produced at temperatures of 600-900 °C. The particles were hollow, ranged in size from 0.1 to 1 μm and consisted of 30-50 nm crystallites.
Dry Etching of PZT Films in an Ecr Plasma
Authors: Charlet Barbara , Davies Kerrie E.
Published: March 2011

PZT films were etched in an ECR microwave reactor with RF polarization.The etch rate was evaluated using various gas mixtures including combinations of two of the following: C12, NF3, SF6 and HBr. The etch rate was measured as a function of the percentage of one gas in the mixture. Other parameters investigated included gas pressure, bias voltage on the electrode and substrate temperature.Results of the effect of temperature show that etch rates are higher on high temperature substrates than on low temperature substrates. A mixture of C12 and SF2 provided a PZT etch rate of 750 Å / min on a substrate, at approximately 100 °C. We evaluated the resultant etch profile and surface roughness