bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Thermal Conductivity through the Development of Nanofluids
Authors: Eastman J. A. , Choi U. S. , Li S. , Thompson L. J. , Lee S.
Published: April 2011

Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids required in many industrial applications. To overcome this limitation, a new class of heat transfer fluids is being developed by suspending nanocry stalline particles in liquids such as water or oil. The resulting “nanofluids” possess extremely high thermal conductivities compared to the liquids without dispersed nanocrystalline particles. For example, 5 volume % of nanocrystalline copper oxide particles suspended in water results in an improvement in thermal conductivity of almost 60% compared to water without nanoparticles. Excellent suspension properties are also observed, with no significant settling of nanocrystalline oxide particles occurring in stationary fluids over time periods longer than several days. Direct evaporation of Cu nano-particles into pump oil results in similar improvements in thermal conductivity compared to oxide-in-water systems, but importantly, requires far smaller concentrations of dispersed nanocrystalline powder.
Polymerizable Complex Synthesis of Nanocomposite BaTi4/O9 Photo-Catalytic Materials
Authors: Kakihana Masato
Published: April 2011

The “polymerizable complex (PC)” technique, a kind of gel technologies, is based on formation of a polyester resin precursor in which various metal ions can be uniformly distributed keeping their initial stoichiometric ratio. The approach allows for the synthesis of multicomponent oxides at reduced temperatures. Feasibility of the PC method is demonstrated for the synthesis of BaTi4O9 at 700–900 °C. BaTi4O9 was subsequently converted to nanocomposite materials by modifying its surface with ultrafine particles of RuO2, and they were used as photocatalysts for decomposition of water into H2 and O2 under irradiation of light from a high-pressure Hg lamp operated at 100 W. High-resolution transmission electron microscopic observations indicates uniform dispersion of spherical RuO2 particles of ∼2 nm in diameter on the host BaTi4O9 surface. The nanocomposite BaTiO9/RuO2 (1 wt % Ru relative to BaTi4O9) material prepared by the PC method at 800 “C showed a photo-catalytic activity ∼3 times higher than that of a material prepared by the conventional ceramic technique at 1100 °C.
Preparation and Sintering of Silica-Doped Zirconia by Colloidal Processing
Authors: Uchikoshi T. , Sakka Y. , Ozawa K. , Hiraga K.
Published: April 2011

Silica-doped (SiO2= 0–1.0 mass%) zirconia (3 mol% Y2O3-doped tetragonal ZrO2) compacts are prepared from hetero-coagulated and well-dispersed suspensions by colloidal processing. The suspensions are consolidated by a pressure filtration technique. The green density of the compacts consolidated from the well-dispersed suspensions is higher than that from the hetero-coagulated suspensions. The lower density of the latter compacts is improved by a subsequent cold isostatic pressing (CIP) at 400 MPa. The sinterability of the compacts at 1200 °C is greatly affected by the amount of doped silica. The densification and grain growth are hindered by silica doping above 0.3 wt% at 1200 °C. All the compacts are densificated to a relative density of above 99% by sintering at 1300 °C for 2 h.
Ferroelectric Lead Zirconate Titanate Nanocomposites for Thick-Film Applications
Authors: Yao Kui , Zhu Weiguang , Yao Xi
Published: April 2011

In this paper, we report our experimental results of lead zirconate titanate (PZT) thick-films prepared from the sol-gel derived nanocomposites. Transparent Pb-Zr-Ti-B-Si gels were synthesized from various metal organic precursors. PZT grains with the size of one hundred nanometers were homogeneously grown from the gels in the annealing process. Then PZT thick-films were prepared using the gel-derived glass-ceramic powders with average particle size below 300 nm. Surficial morphology, dielectric and ferroelectric properties of the films were studied. The characteristics of such films are attributed to the nano-sized composite structure of the gel-derived PZT glass-ceramic precursors.
Low Temperature Synthesis of Lamellar Transition Metal Oxides Containing Surfactant Ions
Authors: Janauer Gerald G. , Chen Rongji , Dobley Arthur D. , Zavalij Peter Y. , Whittingham M. Stanley
Published: April 2011

Recently there has been much interest in reacting vanadium oxides hydrothermally with cationic surfactants to form novel layered compounds. A series of new transition metal oxides, however, has also been formed at or near room temperature in open containers. Synthesis, characterization, and proposed mechanisms of formation are the focus of this work. Low temperature reactions of vanadium pentoxide and ammonium (DTA) transition metal oxides with long chain amine surfactants, such as dodecyltrimethylammonium bromide yielded interesting new products many of which are layered phases. DTA4H2V10O28•8H2O, a layered highly crystalline phase, is the first such phase for which a single crystal X-ray structure has been determined. The unit cell for this material was found to be triclinic with space group P1and dimensions a=9.895(1)Å, b=11.596(1)Å, c=21.924(1)Å, α=95.153(2)°, β=93.778(1)°, and γ= 101.360(1)°. Additionally, we synthesized a dichromate phase and a manganese chloride layered phase, with interlayer spacings of 26.8Å, and 28.7Å respectively. The structure, composition, and synthesis of the vanadium compound are described, as well as the synthesis and preliminary characterization of the new chromium and manganese materials.
Computer Simulation of the Structure of Nanocrystals
Authors: Sasajima Y. , Okuda Shigeo
Published: April 2011

Structural characteristics of nanocrystals were investigated by molecular dynamics simulation. The structural models were constructed in two dimension, assuming the Lennard-Jones type potential as interaction between atoms. The nanocrystal model consisted of ultra-fine particles as a unit structure, like atoms in normal crystals. In the present study, the diameter of the ultra-fine particles is assumed to be constant and the unit particles are assembled in densely packed structure to form a nanocrystal. The orientations of the unit particles were varied randomly to form various kinds of interfaces between their nearest-neighbor particles. This initial structure was relaxed by the molecular dynamics method with controlling the system temperature by rescaling the velocities of the atoms. The system temperature was set to be so high as to accelerate the relaxation process in the nanocrystal structure. If the diameter of the fine particle is less than 6 (the unit length is nearest-neighbor distance between atoms), the assembled particles were relaxed to form single crystal structure. When the diameter increased larger than 10, the nanocrystal structure was stable and the grain boundaries, vacancies and edge dislocations were remained in the system.
Low Temperature Hydrothermal Synthesis of Nanophase BaTiO3 and BaFe12O19 Powders
Authors: Dogan Fatih , O'rourke Shawn , Qian Mao-Xu , Sarikaya Mehmet
Published: April 2011

Nanocrystalline powders with an average particle size of 50 nm has been synthesized in two materials systems under hydrothermal conditions below 100°C. Processing variables, such as temperature, concentration and molar ratio of reactants and reaction time were optimized to obtain particles of reduced size and stoichiometric compositions. Hydrothermal reaction takes place between Ba(OH)2 solution and titanium/iron precursors in sealed polyethylene bottles in the BaTiO3 and BaFe12O19 systems, respectively. While crystalline BaTiO3 forms relatively fast within a few hours, formation of fully crystalline and stoichiometric BaFei20i9 require considerably longer reaction times up to several weeks and strongly dependent on the Ba:Fe ratio of the precursors. The structural and compositional evaluation of the nanophase powders were studied by XRD and TEM techniques.
Processing-Property-Microstructure Relationships in Tial-Based Alloys
Authors: Loretto M H , Hu D , Godfrey A
Published: April 2011

A range of TiAl-based alloys have been produced by plasma melting either small buttons (1kg samples) or ingots (up to 50kg). Some of the ingots have been atomised. The influence of thermomechanical processing on the microstructure of these materials has been assessed using optical and electron microscopy and the room temperature mechanical properties and creep strengths determined. It has been found that either through appropriate processing and/or through alloy development, it is possible to obtain alloys with room temperature strengths up to 1000MPa. Elongations of about 1% at room temperature have been obtained for alloys with this strength and this is coupled with significant improvements in creep strength over the reference alloy, Ti-48Al-2Mn-2Nb. The influence of the difficulty of slip transfer between gamma and alpha 2 has been assessed as one of the factors limiting ductility. Regions which are low in aluminium, which are present in the atomised powders initiate fracture at very low strains. These results are discussed in terms of the factors that control the strength and fracture behaviour of TiAl-based alloys.
Deformation of Polysynthetically Twinned (PST) TiAl Crystals at High Strain Rate and High Temperature
Authors: Jin Zhe , Gray George T. , Yamaguchi Masaharu
Published: April 2011

Deformation microstructures in a 45°<321> oriented (the lamellar interface was tilted 45° from the loading axis about the <321> direction in the lamellar interface) poly synthetically twinned (PST) TiAl crystal deformed in compression at 3000 s-1 and 800 °C was studied. Deformation of this PST crystal is characterized as follows: 1) Deformation of domains [III] and [IV] is dominated by 1/6 [112] parallel twinning (twinning parallel to lamellar interfaces). Ordinary dislocations observed in these domains are found to be a complementary deformation mode. 2) Deformation of domains [II], [V] and [VI] is controlled by a 1/2<110] ordinary dislocation slip. Complementary deformation modes in these domains are ordinary dislocation slip, superdislocation slip and cross-twinning. 3) Domain [I] is not deformed after the specimen deforms up to ∼7% strain.
The Charpy Impact Behavior of Fe3Al and Fe3Al-20 at % Mn Alloys
Authors: Liu J. N. , Yan W. , Ma J. L. , Wu K. H.
Published: April 2011

A series of experiments were conducted to investigate the impact fracture behavior of Fe3Al and Fe3Al-20 Mn alloys. The results of this study indicated that: (i) The addition of Mn introduces an ordered Ll2-type phase in the Fe3Al-based alloys. On the other hand, the addition of Mn decreases the order parameter of the DO3 a phase, (ii) The total- impact energy of an Fe3Al alloy increases with the temperature at the low-temperature range (<600°C), then drops around 700°C, and finally increases again as the temperature further elevates, (iii) The trend of the variation of the impact energy of Fe3Al-20 at % Mn alloy with temperature is the same as that of the Fe3Al alloy, (iv) And the addition of Mn significantly improves the impact energy of the Fe3Al-based alloy, and changes the variation of the crack-growth energy with the testing temperature when the temperature is above 700°C.
The Effect of Ti Addition on Oxidation Behavior of FeAl Intermetallic Alloy
Authors: Li Dingqiang , Lin Dongliang , Lin T. L.
Published: April 2011

The influence of Ti addition on the high temperature oxidation behaviors of FeAl intermetallic alloys in air at 1000°C and 1100°C have been investigated. The oxidation kinetics of FeAl alloys were examined by the weight gain method and oxide products were examined by XRI), SEM, EDS and EPMA. The results showed that the oxidation kinetic curves of both Ti-doped and binary Fe-36.5A1 alloys were described as different parabolas followed the formula: (ΔW/S)2 =Kpt. The parabolic rate constant, Kp values are about 2.4 and 3.3 mg2cm-4h-1 for Fe-36.5A1 alloy and about 1.3 and 2.0 mg2cm-4V-1 for Fe-36.5Al-2Ti alloy when oxidizing at 1000°C and 1100°C respectively. The difference between Fe-36.5Al and Fe-36.5Al-2Ti alloy is not only in the surface morphology but also in the phase components. In the surface there is only α-Al2O3 oxide for the Fe-36.5Al alloy while there are α-Al2O3 and TiO oxide for the Fe-36.5Al-2Ti alloy. The effects of Ti addition on the oxidation resistance of FeAl alloy were discussed based on the micro structural evidence.
Assessment of the Compositional Influences on the Toughness of TiCr2-Base Laves Phase Alloys
Authors: Chen Katherine C. , Allen Samuel M. , Livingston James D.
Published: April 2011

Systematic studies of alloys based on TiCr2 have been performed in order to improve the toughness of Laves phase intermetallics. The extent to which alloy compositions and annealing treatments influence the toughness was quantified by Vickers indentation. The single-phase Laves behavior was first established by studying stoichiometric and nonstoichiometric TiCr2. Next, alloying effects were investigated with ternary Laves phases based on TiCr2. Different microstructures of two-phase alloys consisting of (Ti,Cr)-bcc+TiCr2 were also examined. Various toughening theories based on vacancies, site-substitutions, crystal structure (C14, C36, or C15) stabilization, and the presence of a second phase were evaluated. The most effective factors improving the toughness of TiCr2 were determined, and toughening mechanisms are suggested.
Ductility Improvement of Direct-Cast Gamma TiAl-Based Alloy Sheet
Authors: Hanamura Toshihiro , Hashimoto Keizo
Published: April 2011

For improving the room temperature tensile ductility of direct-cast gamma TiAl sheets without affecting their high-temperature strength, direct sheet casting with T1B2 particle dispersion is employed and conducted. The T1B2 addition and rapid cooling results in the formation of a fine equiaxed grain microstructure with an average grain size of ∼10μm, contributing to the increase in the room temperature ductility to 2.1% with the high-temperature tensile strength kept at about 200MPa. This improvement of room-temperature ductility is attributable to the following fact. The high oxygen content of this material, about 2500wt. ppm, is not harmful to the tensile ductility when the oxygen is in the solid solution of the 0:2 lamellar phase or in oxide particles, which are fine enough not to cause brittleness to the matrix. From these findings, a principle is proposed that oxygen is not harmful to the ductility of gamma TiAl when its microstructure containing oxygen is fine enough.
Reactive Infiltration Processing of Bulk and Fiber-Reinforced NiAl
Authors: Venkatesh T. A. , Sanmarchi C. W. , Mortensen A. , Dunand D. C.
Published: April 2011

Reactive infiltration processing was investigated in the NiAl system using nickel-powder and nickel-wire preforms. Inhomogeneous microstructures were often obtained with powder preforms which had high surface-to-volume ratio, low permeability and irregular infiltration paths. Homogenous NiAl could be obtained with nickel-wire preforms which had lower surface-to-volume ratio, higher permeability and regular infiltration paths. NiAl composites reinforced with short molybdenum fibers and long tungsten and sapphire fibers were also fabricated by reactive infiltration.
Key Microstructures Controlling the Mechanical Properties of Two-Phase TiAl Alloys with Lamellar Structures
Authors: Liu C. T. , Maziasz P. J. , Wright J. L.
Published: April 2011

The objective of this study is to identify key microstructural parameters which control the mechanical properties of two-phase γ-TiAl alloys with lamellar structures. TiAl alloys with the base composition of Ti-47Al-2Cr-2Nb (at. %) were prepared by arc melting and drop casting, followed by hot extrusion at temperatures above the oc-transus temperature, Tα. The hot extruded materials were then heat treated at various temperatures above and below Tα in order to control microstructural features in these lamellar structures. The mechanical properties of these alloys were determined by tensile testing at temperatures to 1000° C. The tensile elongation at room temperature is strongly dependent on grain size, showing an increase in ductility with decreasing grain size. The strength at room and elevated temperatures is sensitive to interlamellar spacing, showing an increase in strength with decreasing lamellar spacing. Hall-Petch relationships hold well for the yield strength at room and elevated temperatures and for the tensile elongation at room temperature. Tensile elongations of about 5% and yield strengths around 900 MPa are achieved by controlling both colony size and interlamellar spacing. The mechanical properties of the TiAl alloys with controlled lamellar structures produced directly by hot extrusion are much superior to those produced by conventional thermomechanical treatments.
Simulations of Polymer Blends and Interfaces
Authors: Laasse Martin-D. , Grest Gary S.
Published: April 2011

An efficient continuum-space model for simulating polymer blends and copolymers is presented. In this model, the interactions are short-range and purely repulsive, thus allowing for excellent computational performances. The driving force for phase separation is a difference in the repulsive interaction strength between like and unlike mers. To demonstrate the effectiveness of the model, we study the phase behavior of a symmetric binary blend of polymers as well as the interface between the two immiscible phases. As predicted by theory, we find the critical interaction parameter to scaie with the inverse of the chain length of the polymers. The structure of the interface between two immiscible phases is investigated as a function of chain length and immiscibility. Capillary waves are observed and their measurementallows us to determine the surface tension accurately. Finally, the surface tension is related to the interface width.
Structure Pinning During Phase-Separation of Polyamide/Ionomer Blends
Authors: Weiss R. A. , Feng Y. , Tucker R. , Xie R. , Han C. C. , Karim A.
Published: April 2011

Blends of lightly sulfonated polystyrene and poly(N,N'-dimethylethylene sebacamide) (Li-SPS/mPA) are miscible as a result of strong ion-amide complexation. The blends exhibit LCST phase behavior and an increase of the sulfonation level from 4 to 9.5 mol% raises the critical temperature by 150°C. Phase separation may be thermally induced and isthermodynamically reversible. The phase separation kinetics that occur following a temperature-jump deep into the spinodal region of the phase diagram deviate from conventional Cahn-Hilliard theory and the phase separation process stalls after a couple of hours, essentially pinning the structure at that point. The extent of phase-separation that occurs before pinning is temperature-dependent.
Crucible Steel in South India-Preliminary Investigations on Crucibles from Some Newly Identified Sites
Authors: Srinivasan Sharada
Published: April 2011

European accounts from the 17th century onwards have referred to the repute and manufacture of “wootz’, a traditional crucible steel made especially in parts of southern India in the former provinces of Golconda, Mysore and Salem. Pliny's Natural History mentions the import of iron and steel from the Seres which have been thought to refer to the ancient southern Indian kingdom of the Cheras. As yet the scale of excavations and surface surveys is too limited to link the literary accounts to archaeometallurgical evidence, although pioneering exploratory investigations have been made by scholars, especially on the pre-industrial production sites of Konasamudram and Gatihosahalli discussed in 18th-19th century European accounts. In 1991–2 during preliminary surveys of ancient base metal mining sites, Srinivasan came across unreported dumps with crucible fragments at Mel-Siruvalur in Tamil Nadu, and Tintini and Machnur in Karnataka and she collected surface specimens from these sites as well as from the known site of Gatihosahalli. She was also given crucible fragments by the Tamil University, Tanjavur, from an excavated megalithic site at Kodumanal, dated to ca 2nd c. Bc, mentioned in Tamil Sangam literature (ca 3rd c. BC-3rd c. AD), and very near Karur, the ancient capital of the Sangam Cheras. Analyses of crucible fragments from the surface collection at Mel-Siruvalur showed several iron prills with a uniform pearlitic structure of high-carbon hypereutectoid steel (∼1–1.5% C) suggesting that the end product was uniformly a high-carbon steel of a structure consistent with those of high-carbon steels used successfully to experimentally replicate the watered steel patterns on ‘Damascus’ swords. Investigations indicate that the process was of carburisation of molten low carbon iron (m.p. 1400° C) in crucibles packed with carbonaceous matter. The fabric of crucibles from all the above mentioned sites appears similar. Preliminary investigations on these crucibles are thus reported to establish their relationship to crucible production of carbon steel and to thereby extend the known horizons of this technology further.
Analyses of Archaeological Ceramics From Classic Period Teotihuacan, Mexico, A.D. 150–750
Authors: Kolb Charles C.
Published: April 2011

From ca. A.D. 150–750 Classic period civilization in Central Mexico was dominated by the city-state of Teotihuacan, a metropolis of at least 125,000 inhabitants located in a northeastern valley of the Basin of Mexico. This polity exercised economic and religious control over a wide area, regulated obsidian tool resources and production, and locally fabricated and also imported a variety of ceramic artifacts. In this report I shall summarize the status of current and ongoing investigations of Classic Teotihuacan period archaeological ceramics by surveying briefly the regional geology, reviewing previous research employing petrography and INAA, and examining the salient results of the analyses to date on two foreign and seven domestic ceramic wares. Lastly, I consider important research problems and suggest cautions for future investigations of ceramics and clay sources.
Crushed Brick / Lime Mortars of Justinian's Hagia Sophia
Authors: Moropoulou A. , Cakmak A. , Biscontin G.
Published: April 2011

Structural studies to determine the earthquake worthiness of Hagia Sophia in Istanbul have proved that the monument's static and dynamic behavior depends very strongly on the mechanical and chemical properties of these mortars and bricks used in its masonry. So, the cementrtious nature of the mortars not only explains the fact that the monument still stands but also the very large static deformations which it has undergone, since such mortars have a very long curig period from one to two years. According to the analysis of the dynamic data, the strong motion data from a 4.8R magnitude earthquake about 120 Km south of the building was used to determine the first three natural frequencies of the building. These results show a decrease of about 5–10% in the natural frequencies, as the amplitude of the accelerations increases and returns to their initial values, due to the non-linear nature of the masonry. The above mentioned behavior allows the structure to absorb energy without effecting its material properties, irreversibly. The properties of the mortars and bricks leaded to an extensive study, employing several experimental techniques (FOM, OM, XRD, SEM, TEM, TG/DTA). The results indicated mortars with considerable mechanical strength along with longevity. The model used proved to be resistant to the environmental pollution and to the presence of sah, while the gel phase as binder allows for greater energy absorption and the compatibility of the mortar to the original ones allows continuous stresses and strains. Hence, the recreation of the Hagia Sophia is attempted through a reverse engineering approach to simulate the historical mortars.
Modeling Damage to Limestone Exposed to Atmospheric Pollutants
Authors: Leith S.D. , Reddy M.M. , Ramirez W.F.
Published: April 2011

Preservation of building and monument stone exposed to acidic environments relies on the understanding of acidic precipitation deposition processes and damage mechanisms. Presented here is a model which predicts sulfur accumulation in porous limestone subjected to dry deposition of SO2. The model assumes deposition and reaction of SO2 to form a thin gypsum crust on the moist surface of the stone, and subsequent sulfur (as aqueous sulfate) transport and accumulation in the stone interior driven by diurnal wetting and drying of the stone surface. Characterization of the limestone pore structure contributes significantly to the evaluation and interpretation of modeled sulfate transport and accumulation in porous building materials. Predicted sulfur accumulation in the stone interior is dependent on the surface boundary conditions, the stone pore geometry and structure, and the rates and mechanisms of aqueous/solid sulfur partitioning (i.e. adsorption, precipitation and dissolution). Model results are compared to moisture content and sulfur accumulation measured in limestone briquettes exposed to a natural dry deposition environment. The model successfully predicts moisture transport in field-exposed limestone, but overestimates the rate of sulfur accumulation. The model may be improved by quantification of the time dependence of the surface sulfate concentration and better understanding of the sulfate partitioning mechanisms.
The Presence and Role of Paramagnetic Impurities in the Degradation of Paper
Authors: Attanasio Donato , Capitani Donatella , Emanuele Maria C.
Published: April 2011

Electron Spin Resonance spectroscopy has been used to carry out a systematic investigation of the paramagnetic impurities present in antique and modern paper. Up to eleven different paramagnetic centres, which include different transition ions (Fe3+, Mn2+, Cu2+), organic free radicals, and paramagnetic point defects have been detected, in concentrations ranging from few ppm to several hundreds. Experiments performed on new and deteriorated samples strongly indicate that some of these impurities participate directly or are produced during the aging and degradation processes. They can be used as quality indicators or probes for quantitative monitoring of the degradation of paper.
The Scattering Distribution from Semiconductors as a Function of Angle and Energy Loss in the Electron Microscope
Authors: Boothroyd C. B. , Dunin-Borkowski R. E. , Walther T.
Published: April 2011

We examine the scattering distribution from thin C, Ge and thick Si specimens as a function of scattering angle and energy loss, in order to gain insight into the relative contributions to both low and high angle annular dark field images from elastically and inelastically scattered elections.
Grain Boundary Dislocation Structure and Motion in an Aluminum Σ=3 [011] Bicrystal
Authors: Medlin D. L. , Foiles S. M. , Carter C. B.
Published: April 2011

High-resolution transmission electron microscopy (HRTEM) observations are presented of a/3[111] grain-boundary dislocations in an aluminum Σ=3[011] bicrystal. These dislocations are present on both (111) (coherent twin) and (211) (incoherent twin) facets of the bicrystal boundary. The dislocations on the coherent twin facet migrate by a climb process that increases the thickness of the twinned material. These dislocations originate on a Σ=3 (211) incoherent twin boundary where they are closely spaced and dissociated in a wide core configuration. Atomistic calculations of the defect structure and interaction of multiple a/3[111] grain boundary dislocations are discussed.
Atomic Structure of 66° [110] Asymmetric Tilt Grain Boundary in Aluminum
Authors: Shamsuzzoha M. , Deymier P. A. , Smith David J.
Published: April 2011

A 66° [110] asymmetric tilt grain boundary in Al prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. Due to a 4.5° deviation from the perfect Σ3 misorientation, the boundary is heavily faceted with straight segments running parallel to (111) and (112) planes. All atomic sites across the (111) facets appear to be coincident with the (111) planes at an angle of 66°. The line defects which accommodate the deviation from the perfect twin orientation result in grain boundary stepping. The observed structural features can be described in terms of secondary grain boundary dislocations with Burgers vectors of the type ⅓<111>, and ⅙<112> as well as their interactions.
Kinetic Investigations of the Initial Oxidation Stage of Copper by In-Situ UHV-TEM
Authors: Yang J. C. , Yeadon M. , Kolasa B. , Olynick D. , Gibson J. M.
Published: April 2011

We have examined the nucleation and growth of copper oxides formed by in-situ oxidation of copper thin films inside a modified transmission electron microscope (TEM). Based on this data, we have developed a semi-quantitative model of the initial oxidation stage where the dominant mechanism for transport, nucleation and growth of oxide islands is oxygen diffusion on the surface. The copper oxide can be desorbed by annealing and introducing methanol vapor into the chamber. The clean copper film can be oxidized by introducing oxygen gas. Both the desorption and oxidation processes were observed by planar TEM techniques. The copper film was oxidized in-situ at a partial pressure of 5×104torr. Cu2O islands, which formed epitaxially to the copper film, nucleated and grew into the copper film.
Grain Boundaries In Diamond Films On Si(001)
Authors: Wittorf D. , Jia C. L. , Jäger W. , Grushko B. , Urban K. , Jiang X. , Paul M. , Klages C.-P.
Published: April 2011

Grain boundaries in [001]-oriented diamond films deposited on Si(001) by microwave-assisted chemical vapor deposition have been investigated in plan-view and cross-section samples using high-resolution electron microscopy. The poly-crystalline diamond films used in this study had large fractions of [001]-oriented grains with typical lateral dimensions of 2 μm at film thicknesses beyond 10 μm. Grains with growth orientations near (001) exhibit generally small-angle orientation deviations between their crystal lattices. Small-angle grain boundaries of symmetric and asymmetric geometry with misorientation angles below 15° are investigated in both [110]- and [001]-directions. It is found that the structures of such small-angle grain boundaries can be described by a dislocation model. These grain boundaries are on average parallel to the {110}-plane and contain in many cases micro-facets parallel to {lll}-planes. Large-angle grain boundaries with tilt angles up to 40° are also observed in interconnected films of smaller thickness. In all cases structural units with large open volumes and additional second phases are not found at the grain boundaries.
Metal-ZnO Interfaces Studied by High Resolution Transmission Electron Microscopy
Authors: De Hosson J.Th.M. , Vellinga W. P. , Groen H. B. , Kooi B. J.
Published: April 2011

This paper reports on investigations of Ag-ZnO and Cu-ZnO interfaces, produced by internal oxidation. ZnO precipitates with the wurtzite structure were found showing mainly one orientation relationship (OR) with the matrix. However, closely related ORs were found, rotated by small angles from that orientation relation. The atomic structure of several interfaces surrounding these precipitates was studied and compared using high resolution transmission electron microscopy. This paper focuses on interfaces between low index facets of ZnO and vicinal planes of Ag. These interfaces clearly show relaxations. An interpretation of these relaxations in terms of dissociation of partial dislocations at the interface is put forward.
STM Study of Initial Growth of Titanium Silicide on Si(III)
Authors: Kuriyama H. , Ohara S. , Ezoe K. , Yamamoto T. , Tatsukawa S. , Umekawa M. , Matsumoto S.
Published: April 2011

The nucleation and initial growth of titanium suicide on Si(111)7×7 surface has been studied using the scanning tunneling microscopy(STM) in ultrahigh vacuum. At room temperature Ti atoms react with Si atoms and preferentially adsorb on faulted half of the 7×7 surface. By annealing at 600°C, islandlike structures(amorphous titanium suicide) and striplike structures(crystalline titanium suicide) are formed. Annealing at 700°C drives the growth of striplike structures from islandlike structures. The striplike structures grow parallel to specific directions on the 7×7 surface.
Native Defects and their Interactions with Impurities in Silicon
Authors: Watkins G. D.
Published: April 2011

A review is given of what has been learned from EPR studies over the last ∼35 years concerning vacancies and interstitials in silicon. Lattice vacancies are well understood, their diffusional migration energies determined vs charge state and electronic excitation, and their interactions with most of the common impurities established. The isolated interstitial has not been observed by EPR but a great deal has been learned concerning it from studies of its interactions with impurities, and more recently from theory. The properties of these two intrinsic defects and their progeny will be analyzed to help clarify their role in both the normal thermally activated diffusion processes and the transient-enhanced ones, which are of particular current concern.
Fully Atomistic Analysis of Diffuse X-Ray Scattering Spectra of Silicon Defects
Authors: Nordlund K. , Partyka P. , Averback R. S.
Published: April 2011

Diffuse X-ray scattering is a useful method for studying defects in silicon and metals. Although the traditional approaches of analyzing experimental diffuse X-ray scattering data have given much information about the size of defects and defect clusters, they are not very well suited for determining the atomic configuration. We present a fully atomistic computational method to calculate the diffuse X-ray scattering line profile of an arbitrary atomic configuration, and compare line profiles of point defects and Frenkel pair configurations with experiment.
Effect of Implant Energy on Silicon Defect Evolution
Authors: Desroches J. , Krishnamoorthy V. , Jones K. S. , Jasper C.
Published: April 2011

Recent studies on the relationship between defect evolution and transient enhanced diffusion (TED) have lead to the discovery that, for sub-amorphous Si+ implants, atoms released by extended defects (i.e. {311}'s) are a primary source of interstitials for TED. In this paper, the effect of implant energy on the interstitials stored in {311} defects is reported. Silicon wafers were implanted with Si+ at fluences of 1×1014/cm2 and 2×1014/cm2 and energies of 30, 50 and 100 keV. Rapid thermal anneals (RTA) and furnace anneals were performed at times ranging from a few minutes to several hours, at temperatures of 700°, 750° and 800°C. Cross-sectional and plan-view TEM was used to obtain microstructural information. The extended defects observed upon annealing consisted of both {311} defects and dislocation loops. It was found that the ratio of the interstitials bound by extended defects and the implant dose was 0.3. Changing the implant energy did not change the total number of interstitials trapped in both types of defects combined. There was a noticeable variation in the type of defect that dominated each implant regime, despite the constant value of the trapped interstitial to dose ratio. For an RTA of 5 min. at 750°C, the ratio of {311} “rod-like” defects to dislocation loops in the 2×1014/cm2 sample unexpectedly increased as the energy increased from 30 to 50 keV.

Longer furnace anneals were employed to determine the activation energy of {311} dissolution. Our data suggests a slightly higher activation energy for {311} dissolution of approximately 4.2 eV versus the previously reported 3.6 eV, however, this difference may be within experimental error.
Defects and Diffusion issues for the Manufacturing of Semiconductors in the 21st Century
Authors: Plummer J. D.
Published: April 2011

Within the past decade, process simulation has become an essential part of new technology development in the silicon IC industry. The use of TCAD (technology computer aided design) tools has been driven by the enormous cost of purely experimental approaches to technology development. Yet the power of these tools and their predictive capability are still greatly limited by the models they use. TCAD models for doping processes are universally based today on point defects. These models have evolved considerably in the past decade to incorporate additional understanding. The state-of-the-art today includes concentration dependent diffusion through Fermi level effects on defect concentrations, full coupling between defects and dopants which allows prediction of non-local diffusion effects, basic models for the effects of ion implantation damage (the +1 model), surface and interface effects (through effective recombination velocities and segregation), and full 2D and 3D simulations.

As devices continue to shrink, better models will certainly be required. Challenges for the future include more detailed information about damage resulting from ion implantation, better understanding of point defect properties (equilibrium populations, diffusivities, transient response to temperatures changes), better models for point defect behavior at interfaces, and finally, development of accurate methods to actually measure 2D and 3D dopant profiles. This paper will attempt to describe where we are and where we need to be in the future.
Enhanced Diffusion of Dopants in Vacancy Supersaturation Produced by MeV Implantation
Authors: Venezia V. C. , Haynes T. E. , Agarwal A. , Gossmann H. -J. , Eaglesham D. J.
Published: April 2011

The diffusion of Sb and B markers has been studied in vacancy supersaturations produced by MeV Si implantation in float zone (FZ) silicon and bonded etch-back silicon-on-insulator (BESOI) substrates. MeV Si implantation produces a vacancy supersaturated near-surface region and an interstitial-rich region at the projected ion range. Transient enhanced diffusion (TED) of Sb in the near surface layer was observed as a result of a 2 MeV Si+, 1×1016/cm2, implant. A 4× larger TED of Sb was observed in BESOI than in FZ silicon, demonstrating that the vacancy supersaturation persists longer in BESOI than in FZ. B markers in samples with MeV Si implant showed a factor of 10× smaller diffusion relative to markers without the MeV Si+ implant. This data demonstrates that a 2 MeV Si+ implant injects vacancies into the near surface region.
Influence of dynamic annealing on the depth distribution of germanium implanted in (100) silicon at elevated temperatures
Authors: Nejim A , Jeynes C , Webb R P , Cowern Neb , Patel C J
Published: April 2011

(100) silicon wafers were implanted at elevated temperatures up to 600°C with l×lO15-5×1015 Ge+/cm2 using 120 keV. The wafers were tilted by 5–7° and rotated by 5–15°. The implanted germanium profile was monitored as a function of implant temperature using RBS-channelling. Considerable profile broadening was seen together with apparent mass germanium migration away from the surface in samples implanted at 300°C and above. Control implants into hot and cold samples simultaneously rule out excess loss of germanium from the heated wafers. Channelling data indicate that while room temperature implants lead to amorphisation, with hot implants good quality layers are obtained in which the germanium atoms occupy substitutional sites. Hot implants into a sample previously implanted with germanium at room temperature does not lead to any redistribution in the original germanium profile. This result indicates that the apparent enhanced indiffusion of germanium is not a radiation assisted phenomenon and could be explained by a considerable channelling of the implanted germaniumatoms along the <100> direction.
Lattice Sites and Damage Annealing of Implanted Tm and Er IN Si
Authors: Wahl U. , Correia J. G. , De Wachter J. , Langouche G. , Marques J. G. , Moons R. , Vantomme A. ,   ISOLDE collaboration
Published: April 2011

We have studied the lattice sites of Er in CZ Si single crystals by using conversion electron emission channeling from the isotope 167mEr (2.27 s) which is the decay product of radioactive Tm 167m(9.25 d). Following 60 keV implantation of 167Tm at a dose of 4×1013 cm−2 and annealing at 600°C, more than 90% of 167mEr is found close to tetrahedral insterstitial(T) sites. The tetra-hedral fraction of 167mEr decreases considerably after 10min annealing at 800°C and above. We attribute this to the onset of diffusion of the parent 167Tm and its trapping at other defects, presumably oxygen atoms or clusters of Tm/Er.
Internal Friction in Ion-Implanted Silicon
Authors: Liu Xiao , Pohl R. O. , Crandall Richard S. , Jones K. M.
Published: April 2011

Using a double-paddle oscillator, we have studied the internal friction of thin Si layers which have been disordered by ion implantation. We have identified the temperature-independent internal friction common to all amorphous solids below 10K, and also a narrow relaxation peak at ∼ 48K. This peak has been shown to be caused by divacancies in the damaged crystalline region underneath the amorphous layer. Thermal, rapid thermal, and laser-flash annealing have been compared. The minimum disorder is left after rapid thermal annealing.
Tem Observations of AG-TI Bilayers After Thermal Aging Treatment in a Reducing Ambient
Authors: Amali Adam I. , Mayer J.W. , Zeng Yuxiao , Zou Y.L. , Alford T.L. , Deng F. , Lau S.S.
Published: April 2011

Transmission electron microscopy (TEM) in both cross sectional and plan view is used to study the effect of annealing Ag-Ti bilayers deposited on SiO2/Si substrates in an NH3 ambient. The resulting structure, texture and grain size are investigated. Comparisons are made between films annealed at 400, 500 and 600 °C. Silver films show increasingly strong <111> texture with annealing temperature while exhibiting a bamboo-like grain structure at 600 °C. Considerable grain growth with lateral grain sizes of up to 5 times the thickness of the Ag film is observed at 600 °C. The grains typically extend through the Ag film thickness. The Ti/SiO2 interface uniformity and the absence of voids at the substrate surface are positive indicators of the role of titanium as a good adhesion promoter. At 600 °C, a uniform TiN encapsulation layer is observed on the Ag surface.
Change From Polycrystalline to Amorphous Growth in Sputtered CoZr/Cu Multilayers
Authors: Langer J. , Mattheis R. , Schmidt S. , Senz St. , Hesse D. , Schuhrke Th. , Fischer R. , Zweck J.
Published: April 2011

We present an investigation of structural changes occurring in bilayer stacks with crystalline columnar growth when one of the layers is substituted by layers known to grow amorphous. In Co/Cu multilayers the Co layers were substituted by CoZr layers of varying Zr content and layer thickness. Structural characterisation was performed by transmission electron microscopy (TEM). We show that the amorphisation of the CoZr layers leading to a destruction of the columnar growth depends both on the Zr content and on the thickness of the CoZr layers. Additionally a change to textured growth with a <111> normal to the substrate occurs with increasing Zr content. We explain our observations by a simple picture based on the hard sphere model.
Morphology and Texture of Chemical-Vapour-Deposited TiN Films
Authors: Yoshikawa Noboru , Taniguchi Shoji , Kikuchi Atsushi
Published: April 2011

TiN films were obtained by Chemical Vapour Depositon (CVD) under different deposition conditions. Their grain structure, morphology and preferred crystal orientation were investigated. It was observed that well-defined columnar grams developed under conditions of atmospheric thermal CVD, giving rise to strong preferred orientations. In this study, grain structures of CVD-TiN films were classified with respect to the substrate temperature. Films of zone I structure were obtained at 1173K (0.35Tm), and those of zone II were obtained at 1223K (0.38Tm). Crystal shape of the zone II columnar grains was influenced by the partial pressure of TiCl4 (PTiCl4), and the crystal orientation of films was related to the crystal shapes. Columnar grains increased their thickness during deposition process under conditions of low PTiC14 and high temperature (>1250K). The increase rate of grain size had a similar time dependence to that of normal grain growth. The “quadrangular-shaped” and “star-shaped” columnar crystals were formed. They consisted of several crystals and contained twins. Their microstructures were observed in relation to their crystallographic features.
Stress Control in Sputtered Silicon Nitride Films
Authors: Mescher M. J. , Reed M. L. , Schlesinger T. E.
Published: April 2011

We show that stress in sputter-deposited silicon nitride films can be controlled, making either compressive or tensile stress films achievable. These films were deposited via reactive rf magnetron sputtering using an elemental Si target and N2 as a reactive gas in an Ar ambient. Variation of stress as a function of deposition pressure and N2/Ar gas mixture ratio was examined over a wider range of these two parameters than in previous work. More importantly, this parameter space includes conditions which produce near-stoichiometric Si3N4 films over a wide range of deposition pressures. We demonstrated that both low compressive stress and even tensile stress can be achieved at the proper deposition conditions. The film stresses as a function of deposition pressure or N2/Ar gas flow ratio are explained in the context of previously developed peening models.
Heteroepitaxial Growth of Cubic Boron Nitride Single Crystal on Diamond Seed Under High Pressure
Authors: Taniguchi T. , Yamaoka S.
Published: April 2011

Single crystal cubic boron nitride(cBN) was heteroepitaxially grown on a seed crystal of diamond under static high pressure and high temperature of 5.5GPa and 1600–1700°C, respectively, for 10–100 hour. A temperature gradient method was employed for the crystal growth by using lithium boron nitride as a solvent. Initial growth feature of cBN crystal was found on the diamond seed surface after the growing time of 10 minutes. The nucleation sites of the crystals seem to be near the etch pits on the diamond surface which were introduced by the surface dissolution by the solvent for cBN growth. Two types of growth features, island and step growth were typically shown on the surface. It can be seen that grown crystal appearing as a (111) nitrogen face was exhibited with the step growth feature, while the (11n) face exhibited the island growth feature. Considering the growth process under constant P-T growing condition, growth rate of cBN crystal was significantly small as compared to that of diamond.
Practical considerations in Megasonic Wafer
Cleaning
Authors: Hall R. Mark , Jarvis Taura , Parry Thad
Published: April 2011

In this study, critical hardware and process parameters are evaluated for
their effect on performance in megasonic cleaning applications. Experimental
data is presented which shows the impact of transducer design, bath
temperature, process time, SC1 chemistry, and wafer gap spacing on particle
removal and surface roughness. The ability to remove particles smaller than
0.1 um in size is also demonstrated.
A Novel Surface Preparation and Post-Etch Removal Technique for
InGaAs Sidewalls
Authors: Tabatabaei S. A. , Porkolab G. A. , Agarwala S. , Johnson F. G. , Merritt S. A. , King O. , Dagenais M. , Chen Y. J. , Stone D. R.
Published: April 2011

This paper describes in detail a surface preparation, and post-etch removal
technique developed for InGaAs sidewalls. It illustrates the results
demonstrating the effect of sidewall post-etch, surface preparation, and
surface passivation on the performance of high speed InGaAs detectors. Dark
current density for circular diodes with a diameter size varying between 10
and 100 μm was measured at a reverse bias voltage of −5 V. The effectiveness
of various surface preparation techniques was studied by measuring the
immediate improvement in dark current density, as well as its long-term
stability. The benefits of this new technique compared to other techniques
we have investigated include improved device characteristics, long-term
stability, as well as a much less critical process to achieve optimum
surface properties.