bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tantalum-Nitride Diffusion Barrier Studies Using the Transient-Ion-Drift Technique for Copper Detection
Authors: Heiser T. , Brochard C. , Swaanen M. 
Published: April 2011

AbstractThe permeability of 5 nm thick TaN, Ta and TiN diffusion barriers has been studied by monitoring the bulk copper concentration in silicon after isothermal and isochronal annealing experiments with a transient-ion-drift (TID) technique. The method estimates quantitatively the bulk copper concentration in silicon from capacitance transients of a Schottky barrier which arise when copper ions drift out of the depletion region towards the quasi-neutral region. The correlation between the copper lateral distribution and the position of the copper metal is used to distinguish between background contamination and copper originating from barrier leakage. The TID detection limit is found lower than 1012at/cm3, which makes this technique particularly well adapted for quantitative diffusion barrier studies. Isothermal and isochronal annealing experiments show that TaN fails at a higher temperature than Ta barriers. The copper concentration does not exceed the solubility limit, indicating that copper precipitates nucleate rapidly at the interface. The opposite is found in TiN covered samples where a large copper supersaturation is obtained even after short annealing times.
Study of Ta as a Diffusion Barrier in Cu/SiO2 Structure
Authors: Pan J. S. , Wee A. T. S. , Huan C. H. A. , Chai J. W. , Zhang J. H. 
Published: April 2011

AbstractTantalum (Ta) thin films of 35 nm thickness were investigated as diffusion barriers as well as adhesion-promoting layers between Cu and SiO2 using X-ray diffractometry (XRD), Scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). After annealing at 600°C for 1h in vacuum, no evidence of interdiffusion was observed. However, XPS depth profiling indicates that elemental Si appears at the Ta/SiO2 interface after annealing. In-situ XPS studies show that the Ta/SiO2 interface was stable until 500°C, but about 32% of the interfacial SiO2 was reduced to elemental Si at 600°C. Upon cooling to room temperature, some elemental Si recombined to form SiO2 again, leaving only 6.5% elemental Si. Comparative studies on the interface chemical states of Cu/SiO2 and Ta/SiO2 indicate that the stability of the Cu/Ta/SiO2/Si system may be ascribed to the strong bonding of Ta and SiO2, due to the reduction of SiO2 through Ta oxide formation.
Bonding and Cohesive Properties of Cobalt/Alumina Magnetic Tunnel Junctions
Authors: Oleinik I.I. , Tsymbal E.Yu. , Pettifor D.G. 
Published: April 2011

AbstractMagnetic tunnel junctions (MTJs) are promising candidates for applications in spintronic devices such as magnetic random access memories, read heads and sensors. Previous studies have revealed the critical influence of the chemistry and structure of the ferromagnet metal/alumina interface on both sign and magnitude of the tunneling current in MTJs. We have performed a detailed first-principles study of the structure and bonding at the cobalt/alumina interface in order to understand the relationship between magnetic properties, local bonding environment and cohesion at the interface. Both Al- and 0- terminated interfaces were considered and full geometry optimization of the structure was done by selfconsistent spin-polarized calculations within density functional theory and the generalized gradient approximation. We found that the relaxed atomic structure of the 0-terminated interface is characterized by a rippling of the Co interfacial plane, the average Co-O bond length being 2.04 Å which is within 5% of that in bulk CoO and it is characterized by the covalent bonding between the 0 2p and Co 3d orbitals. The Al-terminated interface contains Co-Al bonds with an average bond length of 2.49 Å compared to 2.48 Å in bulk CoAl and it is characterized by metallic behaviour of the first aluminium layer. As a consequence of different character of bonding, the cohesion at the O-terminated interface is stronger as that at the Al-terminated interface, the work of separation being equal to 6.35 J/m2 and 3.64 J/m2 respectively.
Excimer Pulsed Laser Ablated Molecular Beam Evaporation for the Deposition of Binary Skutterudites
Authors: Durand H.-A. , Suzuki A. , Nishimoto K. , Ito K. , Kataoka I. 
Published: April 2011

AbstractThe family of materials bearing the skutterudite crystallographic structure have recently attracted interest because of their extra-ordinary electrical and thermal transport properties, as well as their peculiar magnetic qualities [1]. Particularly, the group of cobalt antimonide skutterudites has been referred to as electron crystals and phonon glasses. With the goal to prepare skutterudite thin films, laser ablation is unique in its capacity to transfer skutterudite target's complex composition untouched to substrates while providing an hype thermal beam that has a positive influence on thin film growth. We use a pulsed excimer laser at 193 nm to evaporate skutterudites targets in ultra-high vacuum and deposit thins films on silicon wafers and fused silica substrate. We have studied the composition and crystallographic structure of the deposits as a function of substrate temperature and target to substrate distance. Deposits are skutterudite policrystals of several hundreds nanometers. We investigated the electrical as well as the thermal transport properties of thin films having the desired phase and compare these with value reported for the bulk mono-crystals.
Strongly (111) Oriented Metallization by Ion Plating Method
Authors: Kudo T. , Sakuragi S. , Masui S. , Kinoshita K. , Makino H. , Tanaka M. 
Published: April 2011

AbstractWe have succeeded in the synthesis of strong Cu(111) textured films by means of the novel ion plating method(URT-IP). This URT-IP method combines the Cu deposition with the surface cleaning (self-cleaning). In the Cu film synthesis, the cations play a main role: the self-cleaning of underlying Cu seed and TaN barrier surfaces at the first stage of Cu deposition and the promotion of (111) texture. The two growth processes dependent on underlying materials cause the strong (111) orientation; the epitaxial growth on the same (111) oriented underlayer and the promotion of thermodynamically stable (111) texture on the amorphous underlayer. The in-situ Ar+ cleaning of underlayer surfaces by the URT-IP improves the (11) orientation to be much stronger. The URT-IP method is applied also to the synthesis of strong Pt(111) textured films with the same fcc system.
Surface Catalyzed Photo-Assisted Mocvd of Cobalt Thin Films for Enhanced Control of Magnetic Properties
Authors: Chioncel M.F. , Haycock P.W. , Ogrin F.Y. , Ruthven B.L. , Bull J.W. 
Published: April 2011

AbstractThin films of cobalt have been deposited by photo-assisted metal-organic chemical vapour deposition. Samples of thickness less than 60 nm, grown at 110 °C, exhibit inverse hysteresis when an external magnetic field is applied in a particular direction normal to the plane of the film. These films are a mixture of crystalline and, possibly, amorphous phases with a grain size of about 130 nm and a significant oxygen content throughout. The potential roles of the various physical characteristics, as well as that of the photolytic deposition process itself, in the origin of the inverse hysteresis are discussed, as is a possible self-limiting growth mechanism.
Thermodynamics of Paracrystalline Silicon
Authors: Voyles P. M. , Treacy M. M. J. , Gibson J. M. 
Published: April 2011

AbstractFluctuation microscopy experiments have shown that the as-deposited structure of amorphous silicon thin films is paracrystalline. A paracrystal consists of small (< 3 nm in diameter) topologically crystalline grains separated by a disordered matrix. Here we consider the thermodynamics of paracrystalline silicon as a function of the grain size and the temperature. We offer a simple model that qualitatively explains the observed metastability of the ordered structure at low temperature (300 K), the relaxation towards a more disordered structure at intermediate temperatures (600 K), and the recrystallization at high temperatures (1000 K).
Surface and Microstructural Characterization of Homoepitaxial Silicon Grown by Pulsed Laser Deposition
Authors: Pelt J.S. , Magahñ;a R. , Ramsey M.E. , Poindexter E. , Atwell S. , Zheng J.P. , Durbin S.M. , Kobayashi M. 
Published: April 2011

AbstractThere is a great deal of interest in thin film deposition techniques which can achieve good crystal quality at low substrate temperatures. Pulsed laser deposition (PLD), well-known as a reliable technique for fabrication of high critical temperature superconductor thin films, has a number of characteristics which may make it suitable for such applications. In particular, PLD is characterized by a relatively large average species energy, which can be controlled by the laser fluence at the target. This paper describes the growth of silicon on silicon films using PLD over substrate temperatures between 500 and 700 °C, and in-situ characterization using reflection high-energy electron diffraction (RHEED). Transmission electron microscopy confirms the growth of single crystal oriented films, and atomic force microscopy indicates smooth films with an rms surface roughness of less than 2 Å
Novel Nanocrystalline Materials by Pulsed Laser Deposition
Authors: Narayan J. , Sharma A.K. , Kvit A. , Kumar D. , Muth J.F. 
Published: April 2011

AbstractWe have developed a novel method based upon pulsed laser deposition to produce nanocrystalline metal, semiconductor and magnetic material thin films and composites. The size of nanocrystals was controlled by interfacial energy, number of monolayers and substrate temperature. By incorporating a few monolayers of W during PLD, the grain size of copper nanocrystals was reduced from 160nm (Cu on Si (100)) to 4nm for a multilayer (Cu/W/Cu/W/Si (100)) thin film. The hardness increased with decreasing grain size up to a certain value (7nm in the case of copper) and then decreased below this value. While the former is consistent with Hall-Petch model, the latter involves a new model based upon grain boundary sliding.We have used the same PLD approach to form nanocrystalline metal (Ni, Co, Fe embedded in α-A12O3 and MgO) and semiconductor (Si, Ge, ZnO, GaN embedded in AIN and α-A12O3) thin films. These nanocrystalline composites exhibit novel magnetic properties and novel optoelectronic properties with quantum confinement of electrons, holes and excitons in semiconductors. We review advanced PLD processing, detailed characterization, structureproperty correlations and potential applications of these materials.
Amelogenin Nanospheres Modulate Crystal Habit of Octacalcium Phosphate and Hydroxyapatite Crystals in In Vitro Model Systems
Authors: J. Moradian-Oldak , H.B. Wen , A.G. Fincham , M. Iijima 
Published: April 2011

ABSTRACTThis paper is a short review of recent studies, which were undertaken to investigate interactions of amelogenin with octacalcium phosphate (OCP), and apatite. OCP crystals were grown using two independent experimental systems; (a) in a 10% gelatin gel, containing 0-2% amelogenin, where the crystals were formed in a double-diffusion chamber, and (b) in a 10% pure amelogenin gel, where crystal growth took place in between a cation-selective and a dialysis membrane. Apatite crystals were grown from a supersaturated calcifying solution on a bioactive glass in the absence (SCSB) and the presence of amelogenin (SCSrM179). It was found that OCP crystals formed in 10% gelatin gel containing 1-2% amelogenin were longer (3-5 times larger in aspect ratio) than the OCP crystals formed in 10% gelatin without amelogenin. A profound effect was that found in the cation selective membrane system when 10% amelogenin inhibited the growth morphology in a specific manner. Affected crystals had a length to width ratio twice larger than that of control crystals while the width to thickness ratio was about 1/12 of that of the control crystals. Amelogenin promoted the formation of bundles of lengthwise apatite crystals, which were all oriented parallel to their c axes when grown on SCSrM179. It was found that individual apatite crystals within those bundles adopted an elongated, curved shape. The data presented here suggest that amelogenin nanospheres modulate the growth morphology of apatite and OCP crystals and indicate significant functional roles for amelogenin proteins during the in vivo oriented growth of enamel crystallites.
Intrasectoral Zoning of Proteins and Nucleotides in Simple Crystalline Hosts
Authors: Kurimoto Miki , Bastin Loyd D. , Fredrickson Daniel , Gustafson Pamela N. , Jang Sei-Hum , Kaminsky Werner , Lovell Scott , Mitchell Christine A. , Chmielewski Jean , Kahr Bart 
Published: April 2011

ABSTRACTOriented gases of biopolymers in simple, single crystal hosts might be used to measure anisotropic molecular properties of analytes that could not otherwise be crystallized. Here we show two types of crystals as examples of the single crystal matrix isolation of biopolymers: green fluorescent protein in α-lactose monohydrate as a model system for studying the kinetic stabilization of biopharmaceuticals, and adenosine phosphates in potassium dihydrogen phosphate, a first step in the matrix isolation of oligonucleotides. In each case, the hosts undergo compositional zoning – both intersectoral and intrasectoral – during growth from solution. Intrasectoral zoning is evident by the selective luminescence of adjacent vicinal slopes of growth active hillocks. Nucleotides furthermore distinguish between symmetry related growth sectors enantioselectively.
Growth of the {101} face of KDP crystals in the presence of dye Chicago Sky Blue
Authors: Gliko Olga A. , Zaitseva Natalia P. , Rashkovich Leonid N. 
Published: April 2011

ABSTRACTIn situ interference technique is used for a study of morphology and growth kinetics of a pyramidal face of KDP crystals with dye Chicago Sky Blue. It is shown that the impurity is captured by a crystal when its concentration in the solution exceeds a certain temperature depended value. In the presence of impurity the face loses its stability with increasing of supersaturation. Further increase of supersaturation leads to the restore and subsequent loss of stability. The experimental results are interpreted in the framework of earlier developed model for a crystal growth in the presence of the easily desorbed mobile impurity. The parameters characterizing the adsorption behavior of mobile impurity and its capture have been determined.
Low-Temperature CVD Carbon Coatings on Glass Plates for Flat Panel Display Applications
Authors: Tzeng Yonhua , Liu Chao , Cutshaw Calvin , Chen Zheng 
Published: April 2011

ABSTRACTLow-temperature chemical vapor deposition processes were studied for coating carbon films on metal-coated glass plates. Thermal CVD in hydrocarbon mixtures was used for carbon deposition at temperatures between 300°C and 550°C. Carbon deposited on metal coated glass plates were examined by SEM and analyzed using a pin to disk setup in an ultra high vacuum chamber for measuring the electron emission characteristics. Using a one-millimeter diameter tungsten rod with a hemispherical tip as the anode while the carbon coatings as the cathode, current-voltage characteristics of the carbon coatings were measured and used for calculating the electric field at which electron emission started as well as calculating the field enhancement factor of the carbon coatings. Field emission of electrons from carbon coatings starting from an electric field as low as 1.4 volts per micrometer has been achieved.
Very low field electron emission from Hot Filament CVD grown microcrystalline diamond
Authors: Satyanarayana B.S. , Peng X.L. , Adamopoulos G. , Robertson J. , Milne W.I. , Clyne T.W. 
Published: April 2011

ABSTRACTVery low threshold field emission from undoped microcrystalline diamond films grown by the hot filament chemical vapour deposition process (HFCVD) is reported. The effect of crystal size, methane concentration and the temperature has been studied. The microcrystalline diamond films grown using 3% methane (CH4) / hydrogen (H2) gas mixture ratio under varying deposition temperatures exhibit very low emission threshold fields. The threshold fields varied from 0.4 V/ [.proportional]m to 1 V/[.proportional]m for an emission current density of 1 [.proportional]A/cm2. A correlation between the emission characteristics and the material properties is presented. These films exhibit an emission site density of ∼ 104−105/cm2 at an applied field of 3 V/[.proportional]m.
Single-Shot Excimer-Laser Crystallization of an Ultra-Large Si Thin-Film Disk
Authors: Nakata Mitsuru , Oh Chang-Ho , Matsumura Masakiyo 
Published: April 2011

ABSTRACTAn excimer-laser-induced large-grain growth method has been proposed which utilizes non-uniform heat diffusion along the Si thin-film and also along the underlayer. A single-shot of KrF excimer-laser light pulse with uniform intensity could crystallize a circularly pre-patterned Si thin-film of 20νm in diameter, much larger than TFT feature size in present AM-LCD panels.
Sub-grain Boundary Spacing in Directionally Crystallized Si Films Obtained via Sequential Lateral Solidification
Authors: Crowder M. A. , Limanov A. B. , Im James S. 
Published: April 2011

ABSTRACTIn this paper, we report on the average linear density of sub-grain boundaries that are found in directionally solidified microstructures obtained via sequential lateral solidification of Si thin films. Specifically, we have characterized the dependence of the sub-grain boundary density on the film thickness, incident energy density, and per-pulse translation distance. The investigation was confined to analyzing directionally solidified microstructures obtained using straight-line beamlets. It is found that the average spacing of the sub-grain boundaries depended approximately linearly on the film thickness, where it varied from 0.28m at a thickeness of 550Å to ∼0.75μm at 2,000 Å. In contrast, variations in either the energy density or the per-pulse translation distance within the investigated SLS process parameter domain were found to have a negligible effect on the spacing. Discussion is provided on a preliminary model that invokes polygonization of thermal-stress generated dislocations, and on implications of the dependence of device performance on the film thickness.
Applications of Ion Track Lithography in Vacuum Microelectronics
Authors: Musket Ronald G. 
Published: April 2011

ABSTRACTWhen a high-velocity (i.e., typically > 0.1 MeV/amu) ion passes through a material it can change the properties of the material within a cylindrical zone centered on the essentially straight trajectory of the ion. The electronic bonding, phase, and density are among the properties modified in the zone, which is called a latent nuclear, or ion, track. Because the diameters of latent ion tracks are typically less than 20 nm, selective chemical etching is generally employed to improve the detection and assessment of the tracks. Historically, etched nuclear tracks have been used mainly for nuclear particle identification, geochronology, measurement of extremely low-dose radiation levels, and creation of membrane filters.
Fabrication and Characterization of Singly-Addressable Arrays of Polysilicon Field-Emission Cathodes.
Authors: Chubun N.N. , Chakhovskoi A.G. , Hunt C.E. , Hajra M. 
Published: April 2011

ABSTRACTPolysilicon is a promising candidate material for field-emission microelectronics devices. It can be competitive for large-size, cost-sensitive applications such as flat-panel displays and micro electro-mechanical systems. Singly-addressable arrays of field-emission cells were fabricated in a matrix configuration using a subtractive process on Polysilicon-On-Insulator substrates. Matrix rows were fabricated as insulated polycrystalline silicon strips with sharp emission tips; and matrix columns were deposited as gold thin film electrodes with round gate openings. Ion implantation has been used to provide the required conductivity of the poly-Si layer. To reduce radius of curvature of the polysilicon tips, a sharpening oxidation process was used. The final device had polysilicon emission tips with end radii smaller than 15 nm, surrounded by gate apertures of 0.4 μm in diameter. Field emission properties of the cathodes were measured at a pressure of about 10-8 Torr, to emulate vacuum conditions available in sealed vacuum microelectronics devices. It was found that an emission current of 1 nA appears at a gate voltage of 25 V and can be increased up to 1μA at 70 V. Over this range of current, no “semiconductor” deviation from the Fowler-Nordheim equation was observed. I-V characteristics measured in cells of a 10x10 matrix, with a cell spacing of 50 μm demonstrated good uniformity and reproducibility.
Theory and Modelling of Field-Induced Electron Emission
Authors: Forbes Richard G. 
Published: April 2011

ABSTRACTThis paper addresses issues in the theory of field-induced electron emission. First, it summarises our present understanding of the theory of Fowler-Nordheim (FN) plots, and shows the relationship between a recent precise (in standard FN theory) approach to the interpretation of the FN-plot intercept and older approximate approaches. Second, it comments on the interpretation of FN plots taken from semiconductor field emitters. Third, it summarises the main points of a recent hypothesis about the mechanism of field-induced emission from carbonbased films and other electrically nanostructured heterogeneous (ENH) materials. Weaknesses in previous hypotheses are noted. It is hypothesised that thin films of all ENH materials, when deposited on a conducting substrate, will emit electrons in appropriate circumstances. Such films emit electrons at low macroscopic fields because they contain conducting nanostructureinsidethem: this structure generates sufficient geometrical field enhancement near the film/vacuum interface that more-or-less normal Fowler-Nordheim emission can occur. In connection with experiments on amorphous carbon films carried out by a group in Fribourg, it is shown that nanostructure of the size measured by scanning probe techniques should be able to generate field enhancement of the size measured in field electron spectroscopy experiments. This result provides a quantitative corroboration of other work suggesting that emission from amorphous carbon films is primarily due to geometrical field enhancement by nanostructures inside the film. Some counter-arguments to the internal-field-enhancement hypothesis are considered and disposed of. Some advantages of ENH materials as broad-area field emission electron sources are noted; these include control of material design.
Silicon Field Emission Arrays Coated with CoSi2 Layer Grown by Reactive Chemical Vapor Deposition
Authors: Han Byung Wook , Rhee Hwa Sung , Ahn Byung Tae , Lee Nam Yang 
Published: April 2011

ABSTRACTWe prepared Si emitters coated with an MOCVD CoSi2 layer to improve the emission properties. The CoSi2 layer was grown in situ by reactive chemical vapor deposition of cyclopentadienyl dicarbonyl cobalt at 650 °C. The CoSi2 layer was conformally coated on the Si emitter tips and had a twinned structure at the epitaxial CoSi2/Si interface. The CoSi2-coated Si emitters showed an enhanced emission due to the increase of the number of emitting site from Fowler-Nordheim plot. The fluctuation of emission current was reduced by CoSi2 coating. But the long-term stability was not much improved.