bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Drastic Change in Structure and Property of TiO2 Thin Films Deposited by Metal-Organic Chemical Vapor Deposition With Deposition Temperature
Authors: Park Jeong-Hoon , Cho Woon-Jo , Hong Kug-Sun 
Published: April 2011

AbstractTiO2 thin films were deposited by metal-organic chemical vapor deposition (MOCVD) method using titanium tetraisopropoxide(TTIP). A drastic change in structural aspect and its property occurred when the deposition temperature increased above 400°C. Deposition kinetics was proved to transit from reaction controlled regime into diffusion controlled regime above about 400°C in Arrehnius plot. In X-ray diffraction (XRD)and infrared reflectance spectra, it was observed that the crystallinity was decreased significantly around 400°C. The surface microstructure has changed explicitly from dense structure with larger grains to porous one with smaller grains observed by scanning electron microscopy and transmission electron microscopy. Electrical resistance of the films jumped by 2 orders of magnitude, which is measured by the 4-point probe method. The refractive index calculated by Swanepoel's method has decreased from 2.45 to 2.28 at 630nm. The porous microstructure of films deposited at above 400°C was thought to be responsible for the significant decrease in electrical conductivity and refractive index of the films.
When A Mild Mannered 1-5 eV Photon Meets A Big 10 eV Bandgap: Studies Of Laser Desorption From Modified Surfaces of Ionic Single Crystals
Authors: Dickinson J. Thomas , Bandis Christos , Langford Stephen C. 
Published: April 2011

AbstractExposing wide-bandgap ionic materials to UV and IR photons can produce ion emissions with kinetic energies of several eV, well in excess of the photon energy. Electron emissions are also observed. This implies that these materials possess occupied electronic defect states within the band gap. We have investigated the consequences of a variety of defect-generating stimuli (electron irradiation, laser irradiation, mechanical treatments, and heating) on electron and ion emission from inorganic ionic crystals. These stimuli generate defects that strongly interact with the probe laser on a wide variety of ionic crystals, and dramatically decrease the probe laser intensities required for ion and neutral emissions, laser damage, and plume formation.
Plasma and DLC Film Characteristics from Pulsed Laser Ablation Of Single Crystal Graphite and Amorphous Carbon: A Comparative Study Employing Electrostatic Probe Measurements
Authors: Mayo R. M. , Newman J. W. , Sharma A. , Yamagata Y. , Narayan J. 
Published: April 2011

AbstractIn an ongoing effort to investigate plasma plume features yielding high quality DLC films, we have applied plasma plume diagnosis and film characterization to examine plume character distinction from KrF laser ablation of both amorphous carbon (a-C) and single crystal graphite (SCG) targets- The advancing plasma plume produced by these structurally different targets are observed to possess quantitatively similar total heavy particle inventory, ionized fraction, and electron thermal content, yet quite different ion kinetic energy, plume profile, C2 formation mechanism, and concentration of complex molecules. All data support the conclusion that the SCG target plasma plume is populated with heavier, more complex molecules than those in a-C which have been shown to be predominantly comprised of C and C+ under vacuum conditions with the addition of C2 at high fill pressure. Significantly smaller plume profile peaking factor, less energetic and slightly lower temperature plume conditions, laser energy (E1) dependent plume peaking, harder films produced at lower El strongly heterogeneous films, and lesser plume energy attenuation in high pressure background fill in SCG target plumes all support the conclusion of more massive plume species in SCG target plumes. Energy balance estimates indicate that ion kinetic energy dominates and that SCG target ablation liberates about twice the number of 12C atoms per unit El.
Photo-induced Large Area Growth Of Dielectrics With Excimer Lamps
Authors: Boyd Ian W. , Zhang Jun-Ying 
Published: April 2011

AbstractIn this paper, UV-induced large area growth of high dielectric constant (Ta2O5, TiO2and PZT) and low dielectric constant (polyimide and porous silica) thin films by photo-CVD and sol-gel processing using excimer lamps, as well as the effect of low temperature LW annealing, are discussed. Ellipsometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV spectrophotometry, atomic force microscope (AFM), capacitance-voltage (C-V) and current-voltage (I-V) measurements have been employed to characterize oxide films grown and indicate them to be high quality layers. Leakage current densities as low as 9.0×10−8 Acm−2 and 1.95×10−7 Acm−2 at 0.5 MV/cm have been obtained for the as-grown Ta2O5 films formed by photo-induced sol-gel processing and photo-CVD. respectively - several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) UV annealing step improves these to 2.0×10−9 Acm−2 and 6.4× 10−9 Acm−2, respectively. These values are essentially identical to those only previously formed for films annealed at temperatures between 600 and 1000°C. PZT thin films have also been deposited at low temperatures by photo-assisted decomposition of a PZT metal-organic sol-gel polymer using the 172 nm excimer lamp. Very low leakage current densities (10−7 A/cm2) can be achieved, which compared with layers grown by conventional thermal processing. Photo-induced deposition of low dielectric constant organic polymers for interlayer dielectrics has highlighted a significant role of photo effects on the curing of polyamic acid films. I-V measurements showed the leakage current density of the irradiated polymer films was over an order of magnitude smaller than has been obtained in the films prepared by thermal processing. Compared with conventional furnace processing, the photo-induced curing of the polyimide provided both reduced processing time and temperature, A new technique of low temperature photo-induced sol-gel process for the growth of low dielectric constant porous silicon dioxide thin films from TEOS sol-gel solutions with a 172 nm excimer lamp has also been successfully demonstrated. The dielectric constant values as low as 1.7 can be achieved at room temperature. The applications investigated so far clearly demonstrate that low cost high power excimer lamp systems can provide an interesting alternative to conventional UV lamps and excimer lasers for industrial large-scale low temperature materials processing.
Quantification of Melt Ejection Phenomena During Laser Drilling
Authors: Voisey K.T. , Cheng C.F. , Clyne T.W. 
Published: April 2011

AbstractDuring laser drilling, material removal in general occurs both by vaporisation and by the expulsion of molten material. The latter commonly arises as a result of the rapid build-up of gas pressure within the growing cavity as evaporation takes place, but the precise mechanisms responsible for the phenomenon are still unclear. The current work is aimed at gaining an insight into these mechanisms via measurements of the amount of material ejected from cavities during laser drilling under different conditions. Attention is first devoted to the issues which need to be considered when making experimental measurements of the fraction of material removed by melt ejection. These include the collection efficiency and the possibility of chemical changes occurring during the process. Results are then presented from work with a range of metallic substrates (mild steel, tungsten, copper, titanium, aluminium and nickel), drilled with a JK701 Nd-YAG laser under different conditions. Observed variations in the melt ejection levels have been studied for mild steel and aluminium and these are briefly considered in terms of the expected effects of certain material property values and the mechanisms of melt ejection. Results from an existing finite difference heat flow model are used to investigate the significance of melt ejection.
Preparation Of Crystalline Chromium Carbide Thin Films Synthesized By Pulsed Nd:YAG Laser Deposition
Authors: Doi Kazuya , Hiraishi Satoshi , Kawasaki Hiroharu , Suda Yoshiaki 
Published: April 2011

AbstractChromium carbide thin films are synthesized on Si(100) substrates by a pulsed Nd:YAG laser deposition (PLD) method as parameters of methane gas pressure. Glancing-angle X-ray diffraction patterns show that the film prepared by PLD method is a polycrystalline thin film composed of Cr3C2and Cr7C3, even in the base pressure. Diffraction patterns, however, are depended on the methane gas pressure. Grain size of the prepared film increases with increasing methane gas pressure. One of the reasons of these phenomena may be considered to the phase reaction between the ablated species, such as Cr, CrCx and CH4gas in the plasma plume.
Glass-Crystal Boundaries in Liquid-Phase Sintered Ceramics
Authors: Ravishankar N. , Carter C. Barry 
Published: April 2011

ABSTRACTThe interface between dewet glass droplets and the free surface of a crystal and the interface between the intergranular glass and adjoining crystalline grains have been examined with particular emphasis on the influence of the crystallography of the free surface and the grain boundary. The wetting of liquid on the free surface has been shown to depend on the surface structure. The migration of boundaries containing a liquid phase has been studied. The migration is initiated by the difference in surface energy of the bounding planes. Faceting of the grain boundary planes has been examined. It is proposed that the boundary migrates by the motion of the facets.
Preferential dissolution along misoriented boundaries in heterogenite
Authors: Penn R. Lee , Stone Alan T. , Veblen David R. 
Published: April 2011

ABSTRACTHigh-Resolution Transmission Electron Microscopy (HRTEM) results show a strong crystal-chemical and defect dependence on the mode of dissolution of synthetic heterogenite (CoOOH) particles. As-synthesized heterogenite particles are micron-size plates (aspect ratio ∼ 1/30) constructed of crystallographically oriented ∼ 3-nm primary particles or are single ∼ 21-nm unattached heterogenite platelets (aspect ratio ∼1/7). Reductive dissolution, using hydroquinone, was examined in order to evaluate morphology evolution as a function of reductant concentration. Two end-member modes of dissolution were observed: 1) non-specific dissolution of macroparticles and 2) preferential dissolution along misoriented boundaries. In the case of non-specific dissolution, average macrocrystal size and morphology are not altered as building block crystals are consumed. The result is web-like particles with similar breadth and shape as undissolved particles. Preferential dissolution involves the formation of channels or holes along boundaries of angular misorientation. Such boundaries involve only a few degrees of tilt, but dissolution occurs almost exclusively at such sites. Energy-Filtered TEM thickness maps show that the thickness of surrounding material is not significantly different from that of undissolved particles. Finally, natural heterogenite from Goodsprings, Nevada, shows morphology and microstructure similar to those of this synthetic heterogenite.
Thermionic FEEM, PEEM and I/V Measurements of N-Doped CVD Diamond Surfaces
Authors: Köck F.A.M. , Garguilo J.M. , Brown B. , Nemanich R.J. 
Published: April 2011

ABSTRACTImaging of field emission and photoemission from diamond surfaces is accomplished with a high resolution photo-electron emission microscope (PEEM). Measurements obtained as a function of sample temperature up to 1000°C display thermionic field emission images (TFEEM). The system can also record the emission current versus applied voltage. N-doped diamond films have been produced by MPCVD with a N/C gas phase ratio of 48. The surfaces display uniform emission in PEEM at all temperatures. No FEEM images are detectable below 500°C. At ∼680°C the T-FEEM and PEEM images are nearly identical in intensity and uniformity. This is to be contrasted with other carbon based cold cathodes in which the emission is observed from only a low density of highly emitting sites. The I/V measurements obtained from the N-doped films in the T-FEEM configuration show a component that depends linearly on voltage at low fields. At higher fields, an approximately exponential dependence is observed. At low temperatures employed (<700°C), the results indicate a thermionic component to the emitted current.
In-situ Plasma Diagnosis of Chemical Species in Microwave Plasma-assisted Chemical Vapor Deposition for the Growth of Carbon Nanotubes Using CH4/H2/NH3 Gases
Authors: Woo Y.S. , Han I.T. , Lee N.S. , Jung J.E. , Jeon D.Y. , Kim J.M. 
Published: April 2011

ABSTRACTSynthesis of multi-wall carbon nanotubes (MWNTs) was attempted by microwave plasma enhanced chemical vapor deposition using CH4/H2/NH3 gases on Ni/Cr-coated glass at low temperature. The synthesis was investigated by optical emission spectroscopy and quadrupole mass spectroscopy. It was observed that MWNTs could be grown within a very restrictive range of gas compositions. An addition of a small amount of NH3 resulted in a decrease of C2H2, which can be used to estimate the amount of carbon sources in plasma for the growth of MWNTs, and an increase of CN and Hα radicals acting as etching species of carbon phases. These results show that carbon nanotubes can be grown only under an appropriate condition that the growing process surpasses the etching process. The optimum C2H2 /Hα ratio in a gas mixture was found to be between 1 and 3 for the MWNT growth at low temperature.
The role of catalysts and temperature on morphology and field emission properties of decorated C:N nano-tubular structures
Authors: Kurt Ralph , Bonard Jean-Marc , Karimi Ayatollah 
Published: April 2011

AbstractA hot filament chemical vapour deposition (HF-CVD) process was used to synthesise nitrogenated carbon (C:N) nanotubes characterised by feather-like decoration of the tube surface. As a function of deposition temperature the diameter of the produced tubular structures could be adjusted in a controlled way ranging from 1 µm to 50 nm. The influence of catalysts was demonstrated comparing the morphology of catalytically grown tubes with tubes grown onto pure Si wafers. High resolution TEM reveals that the nanotubes are hollow with a wall structure consisting of inner ordered walls and an outer more disordered surface. A possible growth mechanism will be discussed. Furthermore, field emission in vacuum was studied and showed a spectacular correlation to the deposition temperature and therefore the diameter of the C:N tubes.
Energetics and Structural Investigation of Double-Walled Carbon and Silicon Nanotubes
Authors: Fagan Solange B. , Sartor Daniela S. , Mota R. , Baierle R. J. , da Silva Antônio J. R. , Fazzio A. 
Published: April 2011

AbstractUsing two different approaches: Monte Carlo simulations with Tersoff empirical potential and first principles calculations, the energetics and the structural properties of double-walled carbon and silicon nanotubes are investigated. Through Tersoff potential, the changes on cohesive energies for the Si and C systems are determined for several outer tubules for a fixed inner tube. Adopting first principles calculations, based on density functional theory, the trends, in terms of the cohesive energies, are compared with the corresponding obtained results using Tersoff empirical potential. The structures, specially of the most stable double-walled nanotubes, are discussed.
Comparison of the adsorption properties of krypton on multi-walled carbon nanotubes and on graphite.
Authors: Bougrine Abdelhafid , Varlot Karine , Dupont-Pavlovsky Nicole , Ghanbaja Jaafar , Billaud Denis , Béuin François 
Published: April 2011

AbstractKrypton adsorption has been investigated on multi-walled carbon nanotubes prepared by catalytic decomposition of acetylene. Isotherms measured between 77.5 and 83.7K from the first stages of adsorption to the adsorbate saturation vapor pressure are compared to those obtained in the same conditions on graphite. The results are discussed in the light of the nanotube morphology, as determined by transmission electron microscopy.Krypton adsorption proceeds, as on graphite, by successive monomolecular layer condensations on a same surface. From the morphology of the tubes, adsorption probably occurs only on their external surfaces. The first adsorbed layer is commensurate with the substrate. At its completion, it undergoes a transition into an incommensurate solid of higher density. The curvature of the graphene sheets, with respect to those of graphite, produces a stabilization of the commensurate film. The isosteric heat of adsorption Qst was measured to be 11.6 kJ/mol (ΔQst/Qst = 6%) and is lower than that of krypton on graphite.Moreover, the monolayer condensation pressures are higher than those observed with graphite, which probably leads to an incomplete wetting of the surface by limiting the number of krypton monomolecular layers adsorbed before its bulk condensation.
Direct Fabrication of All-Inorganic Logic Elements and Microelectromechanical Systems from Nanoparticle Precursors
Authors: Bulthaup Colin , Wilhelm Eric , Hubert Brian , Ridley Brent , Jacobson Joe 
Published: April 2011

AbstractHere we describe the fabrication of electrostatic motors by liquid embossing, a contact stamp-based method of patterning liquids with sub-micron resolution. We also demonstrate AFM nano-assembly which can produce sub-40 nm dots and lines by transferring either liquid or solid material from a reservoir to a deposition area. Both of these non-lithographic patterning techniques are applicable to nanocrystal, organic, and polymeric solutions and liquids.
DNA Electrophoresis on Two-dimensional Arrays of SiO2 Beads
Authors: Seo Young-Soo , Samuilov V.A. , Sokolov J. , Rafailovich M. , Gersappe D. , Chu B. 
Published: April 2011

AbstractA novel approach of fabricating 2-D arrays of SiO2 beads on a Si surface using the Langmuir-Blodgett (LB) technique is reported. The corrugated surfaces were tested as a separation media for surface electrophoresis of DNA molecules. The measured electrophoretic mobility for λ-DNA is only 20% slower than previously measured on a flat Si wafer. This indicates that the separation mechanism is due to surface friction rather than biased reptation as reported by Tinland in the three dimensional Silica bead matrix where the mobility is two orders of magnitude smaller.
Materials Challenges and Alternatives for Advanced Photolithographic Patterning: From 193 to 157 nm and Beyond
Authors: Reichmanis Elsa , Nalamasu Omkaram , Houlihan Francis M. 
Published: April 2011

AbstractIn the last decade, major advances in fabricating electronic devices have placed increasing demands on microlithography, the technology used to generate today's integrated circuits. Within the next few years, a new form of lithography will be required that routinely produces features of less than 0.1 μ. As the exposing wavelength of light decreases to facilitate higher resolution imaging, the opacity of traditional materials precludes their use; and major research efforts to develop alternate materials are underway. Through understanding of materials structure and its relationship to device process requirements and performance, cycloolefin based polymers provide for sub-0.1 μm imaging capability using 193 nm exposure. Alicyclic monomers such as norbornene are readily copolymerized with other units to afford a wide range of alternative matrices that exhibit transparency at the exposing wavelength and aqueous base solubility. Further reduction in imaging wavelength necessitates renewed research to define alternative materials platforms. Materials transparency is the key issue to be addressed for 157 nm or EUV lithography. Novel polymer architectures including fluorinated polymers will be required to effect sufficient transparency coupled with requisite solubility, sensitivity, contrast etching resistance, shelf life and purity. Each of these issues will be discussed from the perspective of polymer materials chemistry.
Micro-Structuring of Silicon by Pulsed-Laser Ablation Under Reactive Atmospheres
Authors: Jesse S. , Pedraza A. J. , Fowlkes J. D. , Budai J. D. , Lowndes D. H. 
Published: April 2011

AbstractMicro-holes hundreds of μm-deep below the initial surface surrounded by 40- μm-tall micro-cones protruding over the initial surface form in silicon as a response to multiple UV pulsed-laser irradiation in an SF6 atmosphere. The micro-holes and micro-cones are arranged in a characteristic ensemble displaying a self-organized pattern. Similarly, deep-holes and micro-column ensembles form when the irradiation is performed in an oxygen-rich atmosphere. The formation mechanism of microcolumns and microcones in these reactive atmospheres has been studied using scanning electron microscopy, profilometry and x-ray diffraction. The growth of cones under SF6 atmospheres was studied in-situ using an ICCD gated camera coupled to a long distance microscope. The images obtained with the ICCD camera show that the fluorescent plume is correlated with the amount of ablated material. There is also a strong correlation between the plume and the growth of the cones. The cones grow in the region where the laser-generated plume is intense. When the flux of silicon-rich material ceases because the holes are very deep the balance between redeposition and ablation is tilted toward the latter and the cones begin to recede. Laser ablation is not only a function of the nominal fluence but also of the surface roughness and microstructure. These results strongly support the growth mechanism whereby laser-ablated silicon-rich molecules and clusters are transported to the tip and side of the cones by the laser- generated plasma.
Electroreflectance Study of Porous Silicon made from Substrates with Different Resistivities
Authors: Toyama Toshihiko , Nakai Yasuharu , Okamoto Hiroaki 
Published: April 2011

AbstractEmploying electroreflectance (ER) spectroscopy, we have studied optical transitions in porous Si (PSi) with a thickness of 100±50 nm made from crystalline Si (c-Si) substrates with different resistivities, 4–10 ωcm (p-), 0.1–1 ωcm (p), and < 0.018 ωcm (p+). The ER features observed at 1.1–2.8 eV in p+ PSi are analyzed with a simple effective mass approximation (EMA) model for confined electron-hole (e-h) pairs in a spherical quantum dot as we have previously done for those observed at 1.2–3.1 eV in p- PSi. From the ER analysis with the EMA model, the effective crystal size is estimated without destruction, and the kinetic energy and the Coulomb attraction energy of the confined e-h pairs are also deduced.Furthermore, the ER features corresponding to the optical transitions at E1(E0') critical point (CP) are observed at 2.8–3.3 eV in p+ PSi. With an increase in the crystal size, the transition energy of E1(E0') CP in p+ PSi is decreased, while that in p- and p PSi is unchanged from that of 3.4 eV found in c-Si including the p+c-Si. From the Raman results, strain- and disorder-induced spectral changes are found to be negligible, so that the high doping induced effect is the most acceptable mechanism for the red-shift in E1(E0') transitions of Si nanocrystals with the crystal size of 2–3 nm.
Carrier Transport and Lateral Conductivity in Nanocrystalline Silicon Layers
Authors: Kim H. B. , Montes L. , Krishnan R. , Fauchet P. M. , Tsybeskov L. 
Published: April 2011

AbstractWe have studied carrier transport and lateral electrical properties of nanocrystalline Si layers containing size controlled Si nanocrystals. Using results from direct current (dc) and alternating current (ac) conductivity measurements, the charging of Si nanocrystals and Coulomb blockade effect are discussed.