bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactive Ion Etching of the fluorinated polyimide film
Authors: Lee Y. K. , Murarka S. P. 
Published: April 2011

AbstractThe etch conditions affecting the etching of the fluorinated polyimide films in RF plasma using oxygen or fluorine-containing oxygen has been investigated. The effect of power, oxygen gas flow rate, and gas composition on the etch rate of fluorinated polyimide have been determined. The etch rate of the fluorinated polyimide increases linearly with the power and oxygen gas flow. The saturation at high oxygen flow rate indicates a saturation or steady state achieved at the polyimide-oxygen reaction interface. However, the etch rate increases when CF4 is added to oxygen, up to about 10% CF4 in O2, and then decreases to a smaller and CF4 concentration independent value. The etch selectivity of hard mask against fluorinated polyimide has been determined. The PECVD silicon nitride and PETEOS are found to be excellent hard mask for pattering these polyimides. The trench profile of the polyimide film also has been examined by patterning and etching the different trench sizes in fluorinated polyimide. It is concluded that this fluorinated polyimide can be etched with oxygen or fluorine containing oxygen plasma.
Evaluation of Lpcvd Boron Nitride as a Low Dielectric Constant Material
Authors: Levy R. A. , Narayan M. , Karim M. Z. , Hsu S. T. 
Published: April 2011

AbstractThis study characterizes low pressure chemically vapor deposited B-N-C-H as a low dielectric constant material for interlevel dielectric applications. These films are synthesized over a temperature range of 400 to 600 °C and various flow rate ratios using triethylamine borane complex (TEAB) and NH3 as precursors. The dielectric constant of these films exhibit values which varied in the range of 2.6 to 3.5 depending on processing conditions. Low dielectric constant values are achieved at film compositions which approached stoichiometry and have minimal carbon content. The variations in the structural, optical, mechanical, and chemical properties of these films as a function of deposition conditions are also discussed.
Cobalt and Titanium Metallization of SiGeC for Shallow Contacts
Authors: Bair A. E , Alford T. L. , Atzmon Z. , Marcus S. D. , Doller D. C. , Morton R. , Lau S. S. , Mayer J. W. 
Published: April 2011

AbstractShallow contact metallization of SiGeC was studied in anticipation of this alloys use in low power applications. It has been shown that in the solid state reaction of Co on (100) Si, that Co is the moving species with proper annealing conditions. This prevents the formation of Kirkendal voiding in certain device structures. This work studies the Co and Ti metallization of SiGeC. A bilayer of 44 nm of Co on 7 nm of Ti, were electron beam evaporated onto epitaxially grown Si0.77Ge0.21C0.02. The samples were rapid thermal processed at 600 and 900 °C for up to two minutes in a nitrogen ambient. The analysis techniques used were Rutherford backscattering spectrometry which included the used of the 4.27 MeV 12C(α,α) 12C resonance reaction, glancing angle x-ray diffraction, During annealing at all temperatures, Co diffused through the Ti layer and formed CoSi. This phase was confirmed by x-ray diffraction. The Co displaced the Ti to the surface. At 600 °C, Ge diffused to the surface layer, while at 900 °C it was rejected back into the original SiGeC. The sample annealed at 600 °C was subsequently annealed at 900 °C. The Ge in the surface layer was rejected from the surface layer, diffused across the CoSi and back into the SiGeC.
Angle Resolved Photoemission from Ultrathin Films of Cu/Ni(001)
Authors: Subramanian K. , Mankey G. J. , Stockbauer R. L. , Kurtz R. L. 
Published: April 2011

AbstractWe present a study of the quantum well states observed in Cu/Ni(001). Several reports in the recent past have shown that these states, which are derived from the bulk, disperse through the Fermi level at a thickness of about 6 ML. Using angle-resolved photoemission, we have imaged the photoelectron angular distributions from several thicknesses of Cu/Ni(001). We observe that these states have s,p like symmetry and are located near the zone edge.
Mesoporous TIO2 Electrodes for Photovoltaic Applications
Authors: Barbé C. J. , Graetzel M. 
Published: April 2011

AbstractDuring the past five years, we have developed in our laboratory a new type of solar cell based on a photo-electrochemical process. A respectable photovoltaic efficiency (i.e. 10%) is obtained by the use of mesoporous, nanostructured films of anatase particles. We will show how the TiO2 electrode microstructure influences the photovoltaic response of the cell. More specifically, we will focus on how processing parameters such as hydrothermal growth temperature, binder addition and sintering conditions influence the film porosity, pore size distribution, and consequently affect the solar cell efficiency.
Potentialities of an Innovative Technique Like 129Xe NMR and of Saxs for the Characterization of Microporous Sol-Gel Derived SiO2
Authors: de Menorval L. C. , Julbe A. , Jobic H. , Dalmon J. A. , Guizard C. 
Published: April 2011

AbstractAddition of surfactants in TEOS derived sols leads to micro- or mesoporous materials whose porous texture can be varied by changing the surfactant quantity and/or chain length. This series of materials, with a relatively narrow pore size distribution, is well adapted to study the potentialities of an innovative characterization technique like 129Xe Nuclear Magnetic Resonance in comparison with Small Angle X-ray Scattering and N2 adsorption. SAXS revealed a high surface rugosity of the materials and a good correlation with pore hydraulic radius distributions measured by N2 adsorption. Using 129Xe NMR, we have studied the Xe chemical shifts (δXe,) as a function of pXe, and have pointed out several original results showing the importance, for microporous materials, of the NMR line shapes and of the slope of the lines δXe.=f(pXe).
Spectroscopy of Iron Germanium Sulfide Open-Framework Materials and Precursors
Authors: Kirkby Scott J. , Ozin Geoffrey A. 
Published: April 2011

AbstractThe electronic and vibrational spectroscopy of one family of metal germanium sulfide open-framework materials, designated Cat2FeGe4S10 (Cat = (CH 3)4N, Cs), along with their precursor Cat4Ge4S10 germanium sulfide clusters have been studied. Ultraviolet-visible and midinfrared reflectance spectroscopy has been used to study the electronic states. The reflectance spectroscopy of the frameworks is dominated by the d-d transitions of the Fe(II) in a S4 symmetry site. The vibrational spectroscopy has been analyzed by Fourier transform Raman. The frameworks are weakly vibrationally coupled. Their spectra contain vibrational modes that are nearly identical in frequency to those of the isolated cluster. There is a fortuitous window in the cluster vibrations in which framework modes of the Fe(II) center can be observed. In addition computational methods have been used to model the experimental results.
Microstructural Analysis and Modelling of Thin Porous Silicon Layers with Variable Angle Spectroscopic Ellipsometry
Authors: Pettersson L. A. A. , Zangooie S. , Bjorklund R. , ARWIN H. 
Published: April 2011

AbstractThin porous silicon (PS) layers (30–1000 nm) have been produced by electrochemical anodization of highly p-doped silicon in a hydrofluoric acid electrolyte at constant current density. Variable angle spectroscopic ellipsometry was used for characterization in the spectral range 1.24–5.00 eV. Four multilayer models were developed for the PS layers. Ellipsometric spectra were fitted for three of these models by utilizing an effective medium approximation for each sublayer containing crystalline silicon and voids. A third constituent, amorphous silicon, was added in the fourth model. Excellent fits to experimental data were obtained in the entire spectral range and thickness and composition of each individual sublayer in the models were determined. The analyses revealed a compositional gradient normal to the surface. The porosity and the fraction of amorphous silicon decreased with film depth, whereas the fraction of crystalline silicon increased. The mean porosity of a PS layer was obtained as the thickness weighted average of the porosities of the sublayers. The proposed multilayer models allow a more detailed analysis of PS layers compared to single layer models.
Proteins Encapsulated in Porous Sol-Gels: Biomolecules as Pore Structure Templates
Authors: Dave B. C. , Dunn B. , Valentine J. S. , Zink J. I. 
Published: April 2011

AbstractPorous inorganic SiO2 glasses obtained by the sol-gel route represent a unique matrix for encapsulation of biomolecules wherein the pores act as enclosures for high molecular weight proteins. These hybrid materials are characterized by a pore-biomolecule interface between the pore walls and the protein surface. As a specific model protein, cytochrome c (cyt c) is used to elucidate the nature of physical and chemical interactions between the pores of the matrix and the protein. Evidence from optical absorption, and resonance Raman (RR) spectroscopy methods indicates that the dopant protein alters the structural features of the pore walls. The optical and vibrational measurements strongly suggest that the pores that contain the trapped protein undergo little or no structural change during aging and drying as compared to protein-free pores. Vibrational RR analysis of the trapped cyt c also suggests that the protein resides in a pore where the pore dimensions conform to the shape of the protein. The results indicate that noncovalent interactions between the surface of the protein and the pore walls govern the dynamics of pore formation during gelation and individual biomolecules act as structural templates to design local pore structure.
Aerogel Synthesis Using Extractive Drying
Authors: Smith D. M. , Ackerman W. C. , Roth R. , Zimmerman A. , Schwertfeger F. 
Published: April 2011

AbstractThe advent of ambient pressure aerogel technology may offer process advantages compared to supercritical drying. Since low density is required for most applications of interest, precursor gels must be very dilute (e.g. 6–8% SiO2). The remaining 92–94% is solvent which must be carried along for the entire process, then evaporated, condensed, separated, and recycled to be reused. These steps and associated unit operations represent a major cost (capital and operating). The drying step is problematic because of the large mass of solvent and the inherently low thermal conductivity of the gel. A new approach for drying aerogels is described whereby a wet gel containing a solvent is submerged in hot water or similar fluid which results in removal of the solvent without the drying fluid penetrating the gel. This results in a dried gel with aerogel properties but with the advantages of having a high heat transfer rate without using large temperature gradients as well as providing inherent separation of the dried material. We explore the effects of different solvents and drying temperature gradients on resulting gel microstructure.
Macroporous Thermosets via Chemically Induced Phase Separation
Authors: Kiefer J. , Porouchani R. , Mendels D. , Ferrer J. B. , Fond C. , Hedrick J. L. , Kausch H. H. , Hilborn J. G. 
Published: April 2011

AbstractWe have explored a new technology based on chemically induced phase separation that yields porous epoxies and cyanurates with a closed cell morphology and micrometer sized pores with a narrow pore size distribution. When the precursor monomers are cured in the presence of a low molecular weight liquid, the desired morphology results from a phase separation and a chemical quench. After phase separation, the porosity is achieved by thermal removal of the secondary liquid phase, specifically by diffusion through the crosslinked matrix. In respect to the thermodynamics and kinetics, the origin of the phase separation process can be identified as nucleation and growth. The influence of internal and external reaction parameters, such as chemical nature of the low molecular weight liquid, its concentration and the curing temperature on the final morphology are presented. Thus, the morphology can be controlled ranging from a monomodal to bimodal pore size distribution with pore sizes inbetween 1 to 10 μm. These porous thermosets are characterized by a significantly lower density, without any loss in thermal stability compared to the neat matrix. Such new materials demonstrate great interest for lowering the dielectric constant and for improving the fundamental understanding of the role of voids in stress relaxation and toughening.
Ulm-12 and Ulm-19: The Hydrated and Anhydrous Forms of the First Synthetic Oxyfluorinated Iron Phosphate with an Open Structure
Authors: Cavellec Myriam , Riou Didier , Grenèche Jean Marc , Férey Gérard 
Published: April 2011

AbstractULM-19 or [Fe4(PO4)4F2], [C6H14N2], was obtained in a monocrystalline form from the dehydration of single crystals of ULM-12, or [Fe4(PO4)4F2(H2O)3], [C6H14N2] at 260°C. It is monoclinic (S.G. P21/n) with a = 10.009(7), b = 12.235(8), c = 17.28(2) Å, β = 106.04(5)°, V = 2034(3) Å3, Z = 4. Its structure, which can be described from the corner sharing of hexameric Fe3P3 and dimeric FeP units, directly derives from that of ULM- 12 by the loss, on three of the four Fe(III) polyhedral sites of the structure of ULM-12, of the terminal water molecules. This induces drastic changes in the coordination polyhedra of Fe(III): three octahedra and one square pyramid in ULM-12, and one octahedron, one square pyramid, one trigonal bipyramid and one tetrahedron in ULM-19. These evolutions were confirmed and characterized by in situ Mössbauer spectrometry measurements using a cryofurnace. The loss of water opens 6-ring channels beside the 12-ring tunnels already existing in ULM-12.
Precipitation of Spinel Iron Oxide : Nanoparticle Size Control
Authors: Jolivet J. P. , Vayssieres L. , Chaneac C. , Tronc E. 
Published: April 2011

AbstractThe mean particle size of magnetite precipitated in aqueous solution can be adjusted and stabilized against ripening over a large nanometric range (1.5 to 12.5 nm) by controlling the pH and the ionic strength imposed by a non-complexing salt in the precipitation medium. The higher the pH and the ionic strength are, the smaller the particle size is. An explanation for this phenomenon is based on the lowering of the oxide-solution interracial tension due to the surface electrostatic charge increase. A critical pH value corresponding to the saturation of the interface is defined and calculated. When the precipitation is effected above this critical pH value, the spontaneous decrease in surface area by ripening is avoided and, for a given ionic strength, the particle size depends only on the acidity. This model correlates well with the experimental results. This provides the first experimental example of thermodynamic stabilization of oxide nanoparticles.
Low Temperature Hydrothermal Processing (<100°C) of Stoichiometric BaxSr1-xTiO3 Thin Films and Powders
Authors: Roeder Ryan K. , Slamovich Elliott B. 
Published: April 2011

AbstractBaxSr1-xTiO3 (BST) thin films and powders were processed below 100°C by hydrolyzing Ti metal-organic precursors and TiO2 powder in alkaline Ba/Sr containing aqueous solutions. Film and powder stoichiometries were examined by x-ray diffraction (XRD), and powder stoichiometries were measured by wavelength dispersive spectroscopy (WDS). Both XRD and WDS results showed that Sr cations were more readily incorporated in BST than Ba cations. A thermodynamic model is introduced to predict BST stoichiometry for pH and solution composition. The model is demonstrated for carbonates that also form hydrothermally with Ba and Sr in solid solution, showing good agreement with experimentally measured stoichiometries and confirming a higher reactivity of the Sr cation.
Mixed-Metal Templated Phosphate Phases
Authors: Nenoff Tina M. , Jackson Nancy B. , Harrison William T. A. , Thoma Steven G. , Kohler Steven D. 
Published: April 2011

AbstractIn an effort to direct the structure formation and subsequently the catalytic properties of novel materials, both organic molecules and transition metals have been systematically incorporated into zinc phosphate materials, and various transition metals into zirconium phosphate materials. The resultant phases in the Zn/P experiments are determined not by the organic template, but by the type and stoichiometric amount of metal incorporated and by the organic template's anion. Furthermore, only one of the phases, a Ni/Zn/P, shows any acidic catalytic behavior. Similarly, the transition metals incorporated in stoichiometric amounts into the catalytically active novel zirconium phosphate are highly structure directing. Their presence inhibits the formation of the phosphate phase, instead promoting the formation of tetragonal ZrO2. The catalytic activity of the products are greatly diminished from the baseline material.The synthesis and characterization methods for each phase will be presented. Characterization techniques employed include single-crystal and powder X-ray diffraction, magnetic susceptibility, thermal analysis, DCP and FTIR.
Colloidal Chemistry of Mineral Coagulants as Influenced by Organic Ligands
Authors: Molis E. , Thomas F. , Bottero JY. 
Published: April 2011

AbstractIn the present work, we examine the transformations of aggregated Al13 polycations interacting in suspension with low-molecular-weight organic acids at near neutral pH. The consequences of the interaction strongly depend on the complexing power and concentration of ligands. The most striking feature is the existence of two domains separated by a characteristic adsorbed ligand concentration, corresponding to charge neutralisation by ligands. In the lower concentration domain, ligands interact with the surface aluminum atoms by forming complexes, decreasing the surface charge. In this domain, no soluble aluminum is released from the aggregates. At higher concentration, ligands are adsorbed in excess by ligand exchange and hydrogen bonding, which results in charge reversal. Simultaneously, ligand promoted dissolution of the aggregates occurs, in the form of soluble complexes. It is assumed that dissolution originates from the initially neutral sites. In aquatic media, such radical insitu changes are able to strongly influence the transport and sedimentation of colloids and associated species.
17O NMR Studies of Titanate Repolymerization in Water
Authors: Bunker B. C. , Peden C. H. F. , Kirkpatrick R. J. , Turner G. L. 
Published: April 2011

AbstractLocal structures of high surface area sodium titanate materials have been examined as a function of pH using solid state 17O nuclear magnetic resonance (NMR) spectroscopy. Using 17O NMR, it is possible to determine the relative populations of nonbridging oxygens as well as oxygens bridging between two, three, and four titanium atoms. Results show that protonation of ion exchange sites in titanate materials is not a simple ion exchange process but involves a repolymerization and restructuring of the titanate network. The observed structural changes are consistent with reported phase stabilities of titanates in water as well as with known hydrolysis and condensation reactions.
Effects of Sputter-Deposited LaNiO3 Electrode on the Deposition and Properties of Ferroelectric Thin Films
Authors: Wu T. B. , Wu J. M. , Wu C. M. , Shyu M. J. , Chen M. S. , Doing J. S. , Yang C. C. 
Published: April 2011

AbstractHighly (100)-textured thin film of metallic LaNiO3 (LNO) was grown on the Pt/Ti/SiO2/Si substrates by rf magnetron sputtering at ˜300°C, which was used as a bottom electrode to prepare highly (100)-textured ferroelectric films. Examples on the deposition of PbTiO3, (Pbl−xLax)TiO3, Pb(Zr0.53Ti0.47)O3, Pb[(Mg1/3Nb2/3)1−xTix]O3, and (Ba1−xSrx)TiO3 thin films by rf magnetron sputtering or sol-gel method are shown. A reduction of temperature for perovskite phase formation can be achieved, especially for those difficult to crystallize. The surface roughness of the ferroelectric films is also improved as compared to that of films deposited on conventional Pt electrode. Although the electrical properties of the ferroelectric films are affected by the out-diffusion of LNO when a higher temperature was used in the preparation of the films, under an appropriate processing condition, the highly (100)-textured films can have satisfactory electrical characteristics for application. Moreover, the polarization-fatigue property can be also improved by the use of LNO electrode.
Preparation of PbZrxTi1−xO3 Thin Films by KrF Excimer Laser Ablation Technique
Authors: Kurogi Hiromitsu , Yamagata Yukihiko , Ikegami Tomoaki , Ebihara Kenji , Tong Bok Yin 
Published: April 2011

AbstractPb(ZrxTi1−x)O3(PZT) thin films have excellent ferroelectric, optical, piezoelectric and pyroelectric properties. We prepared PZT thin films using the excimer laser ablation technique. A pulsed KrF excimer laser was used to ablate PZT bulk targets. We have studied optimum preparation conditions such as an oxygen pressure, a laser energy fluence and a substrate temperature.In this paper, we investigated the composition, crystallization and ferroelectric properties of the PZT films prepared under various deposition conditions.The X-ray diffraction (XRD) patterns showed that the PZT films prepared on MgO(100) substrates at 600°C and with a laser fluence of 2J/cm2 had a perovskite - pyrochlore mixed structure. The condition of 100 mTorr oxygen pressure provided high quality perovskite films. It is found that the stoichiometric composition of the deposited films is obtained in ambient oxygen of 100˜400 mTorr. The ferroelectric properties of the Pt/PZT/Pt/MgO structure were studied. The capacitance-voltage characteristics and the corresponding hysteresis loop of the dielectric-electric field curve were discussed.We also studied optical emission of the PZT plasma plume to understand quantitative relation between the PZT film quality and the ablation plume plasma. We identified spectral lines originated in Pb, Pb+, Zr, Zr+, Ti, Ti+, PbO and TiO. These spectral intensities have remarkable dependence on the ambient O2 pressure.
Photoelectric Properties of PbTiO3/Si Heterostructures
Authors: Alexe M. , Pintilie L. , Pintilie I. , Pignolet A. , Senz S. , Hesse D. 
Published: April 2011

AbstractPhotoelectric properties of PbTiO3/Si heterostructures were investigated over a broad range of wavelengths. The spectral distribution of the a.c. open-circuit voltage was measured for wavelengths ranging from 0.35 μm to 4 μm. Two local peaks are observed at 0.38 μm and 0.9 μm which can be attributed to band-to-band excitations in PbTiO3 and Si respectively. The shape of the a.c. signal depends both on the light intensity and on the wavelength. When the heterojunction is reverse-biased, a d.c. photocurrent was observed which has a similar spectral distribution as the a.c. open-circuit voltage.
Preparation of Self-Patterned SrBi2Ta2O9 Thin Films from Photo-Sensitive Solutions
Authors: Soyama Nobuyuki , Uchida Hiroto , Kageyama Kensuke , Ogi Katsumi , Scotit Michael C. , Cuchiaro J. D. , Derbenwick G. F. , Mcmillan Larry D. , Araujo Carlos A. Paz De 
Published: April 2011

AbstractPhoto-sensitive SrBi2Ta2O9 (SBT) solutions were evaluated and the patterning process flow for SBT films using the solutions was optimized. By adding a soft-bake process before UVirradiation, self-patterned SBT films were successfully prepared from the solutions and the cross sectional shape of the patterned films was improved. The photo-sensitivity of the solutions was estimated to be 900 mJ/cm2. The photo-reaction in the precursor gel film formed from the solution was traced by measuring IR absorption spectra. The obtained films had excellent ferroelectric properties comparable to conventional SBT films.