bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure investigation of rapidly solidified Al–V–Fe alloys
Authors: He G. , Shek C. H. , Lai Joseph K. L. , Bian Z. , Hui X. D. , Chen G. L.
Published: March 2008

The microstructures and their thermal behaviors of quenched Al94V4Fe2, Al90V8Fe2, Al86V8Fe6, and Al85V9Fe2Ni4 alloys were investigated by x-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The as-quenched microstructures of the four alloys consist of quasicrystal particles and a fcc-α–Al matrix. The as-quenched Al86V8Fe6 and Al85V9Fe2Ni4 alloys also contain a small volume fraction of amorphous phase. All phases observed have fine morphologies with grain sizes of less than 100 nm. With the increase in V from 4 to 8 at.% at 2 at.% Fe, the average grain size decreases from 100 to 70 nm and the melting temperature of α–Al solid solution increases from 640 to 653 °C. The alloy with 8 at.% V has a finer and more stable microstructure than that of the alloy with 4 at.% V. The Fe addition has minor effect on grain size but improves the glass-forming ability. The Ni addition significantly improves the glass-forming ability and refines the microstructure. The metastable amorphous and quasicrystalline phases transform into a stable crystalline phase during continuous heating and cooling. The stable phases in these Al–V–Fe alloys include α–Al(V, Fe), Al10V, and Al80V12.5Fe7.5.
Synthesis and hydrogen reduction of tungsten–copper composite oxides
Authors: Dorfman L. P. , Houck D. L. , Scheithauer M. J. , Frisk T. A.
Published: March 2008

Cupric tungstate (CuWO4) can be synthesized at high rates of conversion from a variety of solid reactants. However, the fixed copper content in the metal phase of CuWO4 limits its use as an oxide precursor for making W–Cu composite powders. This paper presents test results on synthesis of CuWO4-based composite oxides with a variable content of copper in the metal phase (5–25.7%). Hydrogen reduction converts the oxides to W–Cu composite powders with a unique phase distribution: each individual particle consists of a tungsten phase and a copper phase in which the tungsten phase substantially encapsulates the copper phase. These powders, when pressed and sintered without activators, yield high-density parts with a very fine microstructure and high electrical and thermal conductivity.
Morphological and phase composition changes during sintering of ultralight Al2O3TiO2 foams
Authors: Mann M. , Shter G. E. , Grader G. S.
Published: March 2008

The morphological and phase composition changes during sintering of ultralight pure Al2O3 and Al2O3/TiO2 foams were investigated in the temperature range of 900–1600 °C in air. The titania (10 wt%) was incorporated during a nonhydrolytic foaming procedure to facilitate its uniform dispersion in the alumina matrix. The changes of linear shrinkage and related changes in effective density and porosity demonstrate a higher reactivity in the Al2O3/TiO2 foam. The formation of tialite phase in the Al2O3/TiO2 foams occurred below 1300 °C and remained stable during cooling under 1200 °C without stabilizers.
Magnetic structure of TbBaCo2O5.4 perovskite
Authors: Khalyavin D. D. , Troyanchuk I. O. , Kasper N. V. , Huang Q. , Lynn J. W. , Szymczak H.
Published: March 2008

In accordance with magnetization studies, the fast-cooled TbBaCo2O5.4 is characterized by spontaneous magnetization around 0.18 μB per cobalt ion, which develops below TN = 245 K. The neutron diffraction study of this compound revealed that magnetic moments of Co3+; ions adopting intermediate spine state are ordered antiferromagnetically. Both magnetization and neutron diffraction study showed that there is a spin reorientation process in the wide temperature range. The crystal and magnetic structures are discussed.
Lanthanide series doping effects in lead zirconate titanate (PLnZT) thin films
Authors: Boyle Timothy J. , Clem Paul G. , Tuttle Bruce A. , Brennecka Geoffrey L. , Dawley Jeffrey T. , Rodriguez Mark A. , Dunbar Timothy D. , Hammetter William F.
Published: March 2008

Lanthanide (Ln) doping of lead zirconate titanate (PLnZT 4/30/70) thin films was conducted to investigate effects on structural and electrical properties. Films were spin-coat deposited from precursor solutions made using a previously reported “basic route to PZT” chemistry. The remanent polarization (Pr), dielectric constant (ε), dielectric loss (tan δ), and lattice parameter values were obtained for each of the doped PLnZT films. Films doped with amphoteric cations (Tb, Dy, Y, and Ho) displayed high Pr values, square hysteresis loops, and enhanced fatigue resistance. Smaller radius Ln-doped films display an increased tendency toward (100) orientation in otherwise (111)-oriented films.
Continuous-wave InGaN laser diodes on copper and diamond substrates
Authors: Wong William S. , Kneissl Michael , Treat David W. , Teepe Mark , Miyashita Naoko , Salleo Alberto , Johnson Noble M.
Published: March 2008

InGaN-based optoelectronics were integrated with dissimilar substrate materials using a novel thin-film laser lift-off (LLO) process. The LLO process was employed to integrate InGaN-based laser diodes (LDs) with Cu and diamond substrates. Separation of InGaN-based thin-film devices from their typical sapphire growth substrates was accomplished using a pulsed excimer laser in the ultraviolet regime incident through the transparent substrate. Characterization of the LDs before and after the sapphire substrate removal revealed no measurable degradation in device performance. Reduced threshold currents and increased differential quantum efficiences were measured for LDs on Cu due to a 50% reduction of the thermal impedence. Light output for LDs on Cu was two times greater than comparable LDs on sapphire with a maximum output of 100 mW. Increased light output for LDs on diamond was also measured with a maximum output of 80 mW.
Sintering characteristics of Y–Ba–Cu oxide–Agx superconductors under argon atmosphere
Authors: Pathak L. C. , (Pathak) S. K. Mishra , Srikanth S.
Published: March 2008

Sintering studies on Y–Ba–Cu oxide (YBCO)–Agx (x = 0, 0.6, and 1.0 mol) powder were carried out in argon atmosphere to understand the role of silver addition on the densification behavior of these materials. The increase of sintered densities of the compacts with silver addition in argon atmosphere contradicted our earlier observation on sintering of YBCO–Agx powder compacts in air, where the densities decreased for x > 0.6. Thermogravimetric (TG) studies under argon atmosphere indicate a continuous decrease of mass on heating suggesting an enhanced rate of oxygen removal from the YBCO matrix that facilitated the sintering in argon atmosphere. Sintering studies of YBCO–Agx powder compacts in argon in conjunction with earlier observations in air has substantiated our claim that high-temperature oxygen desorption by the silver from the YBCO matrix to the sintering atmosphere controls the rate of densification for these superconducting composites. However, the apparent activation energies for sintering suggest that the sintering process is controlled by yttrium ion diffusion along bulk and grain boundaries.
Synthesis and characterization of red phosphor (Y,Gd)BO3:Eu by the coprecipitation method
Authors: Kim Kyung Nam , Jung Ha-Kyun , Park Hee Dong , Kim Dojin
Published: March 2008

The synthesis and luminescent properties of (Y,Gd)BO3:Eu phosphor were investigated. A coprecipitation method was designed for preparing Eu doped (Y,Gd)BO3. This method features a low-temperature formation of single phase with semi-spherical shape compared with the conventional method. Due to the homogeneous distribution of activator, the emission intensity of the (Y,Gd)BO3:Eu phosphor prepared by the coprecipitation method is higher than the commercially available red phosphor.
Formation of a Nanostructure in a Low-carbon Steel Under High Current Density Electropulsing
Authors: Zhou Yizhou , Zhang Wei , Sui Manling , Li Douxing , He Guanhu , Guo Jingdong
Published: March 2008

The microstructure of a low-carbon steel after high current density electropulsing treatment was characterized by high-resolution transmission electron microscopy. It was found that nanostructured γ-Fe could be formed in the coarse-grained steel after the electropulsing treatment. The mechanism of the formation of a nanostructure was discussed. It was thought that change of the thermodynamic barrier during phase transformation under electropulsing was a factor that cannot be neglected. It was reasonable to anticipate that a new method might be developed to produce nanostructured materials directly from the conventional coarse-grained crystalline materials by applying high current density electropulsing.
Contrast Mechanism Maps for Piezoresponse Force Microscopy
Authors: Kalinin Sergei V. , Bonnell Dawn A.
Published: March 2008

Piezoresponse force microscopy (PFM) is one of the most established techniques for the observation and local modification of ferroelectric domain structures on the submicron level. Both electrostatic and electromechanical interactions contribute at the tip-surface junction in a complex manner, which has resulted in multiple controversies in the interpretation of PFM. Here we analyze the influence of experimental conditions such as tip radius of curvature, indentation force, and cantilever stiffness on PFM image contrast. These results are used to construct contrast mechanism maps, which correlate the imaging conditions with the dominant contrast mechanisms. Conditions under which materials properties can be determined quantitatively are elucidated.
Phase Evolution of Turbostratic Boron Nitride During the Deposition of Cubic Boron Nitride Film
Authors: Kim Hong-Suk , Choi In-Hoon , Baik Young-Joon
Published: March 2008

The formation of turbostratic boron nitride (tBN) phase on the cubic boron nitride (cBN) phase was investigated at specific conditions. The cBN film was deposited on the Si substrate by unbalanced magnetron sputtering. When the bias voltage at the substrate was adjusted to –85 V, the tBN phase nucleated on the cBN phase and grew simultaneously with the cBN phase. This was a critical bias voltage below which only the tBN phase was formed. The surface morphology of this film was typically shown as nodules dispersed on a very flat surface. The formation of nodulelike tBN phases seemed to be caused by a small variation of local stress on the growth surface. Once the nucleation of the nodulelike tBN phase occurred, the growth of tBN phase was accelerated. Transmission electron microscopy result showed evidence of the stress relaxation of the film caused by the formation of tBN phase at the interface of the tBN and cBN phases.
Oxidation and Resulting Mechanical Properties of Ni/8Y2O3-stabilized Zirconia Anode Substrate for Solid-oxide Fuel Cells
Authors: Stathis George , Simwonis Dimitrios , Tietz Frank , Moropoulou Antonia , Naoumides Aristides
Published: March 2008

Ni/8 mol% Y2O3-stabilized zirconia cermets are used in thin-film electrolyte solid-oxide fuel cells as support substrates. Rapid oxidation of the metallic Ni can cause failure of the substrate and of the whole system. The rate of Ni oxidation in air and in an inert atmosphere containing water vapor was determined as a function of temperature between 500 and 950 °C. A logarithmic rate law describes the oxidation kinetics in air, whereas a linear rate law fits the first branch of the curve of the experimental data in a humidified inert atmosphere. The substrate exhibits no significant mechanical degradation after uniform oxidation under moderate conditions. However, the observed bending of the samples after oxidation in humidified argon, due to the nonuniform oxidation, can cause damage to fuel cell
Microstructures and Mechanical Behavior of Bulk Nanocrystalline γ–Ni–Fe Produced by a Mechanochemical Method
Authors: Qin X. Y. , Lee J. S. , Lee C. S.
Published: March 2008

The microstructures and mechanical behavior of bulk nanocrystalline γ–Ni–xFe (n-Ni–Fe) with x = ∼19–21 wt%, synthesized by a mechanochemical method plus hot-isostatic pressing, were investigated using microstructural analysis [x-ray diffraction, energy-dispersive spectroscopy, light emission spectrum, atomic force microscopy (AFM), and optical microscopy (OM)], and mechanical (indentation and compression) tests, respectively. The results indicated that the yield strength (σ0.2) of n-Ni–Fe (d ∼ 33 nm) is about 13 times greater than that of conventional counterpart. The change of yield strength with grain size was basically in agreement with Hall–Petch relation in the size range (33–100 nm) investigated. OM observations demonstrated the existence of two sets of macroscopic bandlike deformation traces mostly orienting at 45–55° to the compression axis, while AFM observations revealed that these bandlike traces consist of ultrafine lines. The cause for high strength and the possible deformation mechanisms were discussed based on the characteristics of microstructures and deformation morphology of n-Ni–Fe.
Etching-enhanced Ablation and the Formation of a Microstructure in Silicon by Laser Irradiation in an SF6 Atmosphere
Authors: Jesse S. , Pedraza A. J. , Fowlkes J. D. , Budai J. D.
Published: March 2008

Sequential pulsed-laser irradiation of silicon in SF6 atmospheres induced the formation of an ensemble of microholes and microcones. Profilometry measurements and direct imaging with an intensifying charge-coupled device camera were used to study the evolution of this microstructure and the laser-generated plume. Both the partial pressure of SF6 and the total pressure of an SF6-inert gas mixture strongly influenced the maximum height that the microcones attained over the initial surface. The cones first grew continuously with the number of pulses, reached a maximum, and then began to recede as the number of laser pulses increased further. The growth of the cones was closely connected with the evolution of the laser-generated plume.
Investigation of Structure and Properties of the Al–Y–Ni–Co–Cu Metallic Glasses
Authors: Louzguine Dmitri V. , Inoue Akihisa
Published: March 2008

The present paper reports the effect of partial replacement of Ni by Cu in the Al85Y8Ni5Co2 alloy. The studied alloys were produced by rapid solidification. Glass-formation, crystallization behavior, and stability of the supercooled liquid were studied by x-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. Partial replacement of Ni by Cu in the Al85Y8Ni5Co2 metallic glass caused formation of the nanoscale α–Al particles and resulted in a decrease in the crystallization temperature and disappearance of the supercooled liquid.
Intercalation of Rhodamine 6G and Oxazine 4 into Oriented Clay Films and Their Alignment
Authors: Chen Guangming , Iyi Nobuo , Sasai Ryo , Fujita Taketoshi , Kitamura Kenji
Published: March 2008

The cationic dyes rhodamine 6G (R6G) and oxazine 4 (Ox4) were intercalated into oriented lithium hectorite (LiHT, a synthetic fluor-mica) films by ion-exchange, and their orientation was studied by x-ray and polarized spectroscopy. Orientation of dyes was determined by basal spacing obtained by x-ray diffraction data, showing that angles of the long axis were 60° for R6G and 47° for Ox4 against the layer. Polarized ultraviolet-visible spectroscopy showed that the high-order H-aggregate of R6G and Ox4 were oriented at 64° and 52° against layers, respectively; other states of dyes were oriented at much lower angles. The interlayer distance was mostly determined by dimensions of the high-order H-aggregate.
Anisotropic Thermal Expansion in CaAl4O7
Authors: Fukuda Koichiro , Yamauchi Kaori
Published: March 2008

Crystals of CaAl4O7(space groupC2/c) have been examined by high-temperature powder x-ray diffractometry to determine the change in unit-cell dimensions with temperature up to 1473 K. The lattice deformation induced by thermal expansion has been investigated by matrix algebra analysis to determine the directions and magnitudes of the principal distortions. During heating from 298 K, two of the three principal distortions, λ1 and λ2, invariably showed a positive thermal expansion, the magnitudes of which at 1473 K are respectively approximately 1.0% and approximately 0.8%. The direction of λ1 was nearly parallel to [304], and the λ2 axis invariably coincides with the crystallographic b axis. On the other hand, the distortion λ3 showed a negative thermal expansion below approximately 1173 K; the maximum contraction of approximately 0.2% occurred at approximately 673 K nearly along [207]. During further heating to 1473 K, λ3 showed, to the contrary, a positive expansion of approximately 0.2% nearly along [50, 16]. The negative thermal expansion along the λ3 axis substantially accounts for the mean linear thermal expansion being very low at temperatures below approximately 473 K.
Evaluation of Weak Interface Effect on the Residual Stresses in Layered SiC/TiC Composites by the Finite Element Method and x-ray Diffraction
Authors: Qin Shuyi , Jiang Dongliang , Zhang Jingxian , Qin Jining
Published: March 2008

A symmetrically layered SiC/TiC ceramic with a gradual structure was designed by the finite element method (FEM). After sintering, proper thermal residual stress was introduced into the ceramic due to the coefficients of thermal expansion mismatch between the different layers. After different SiC + C interlayers were inserted into the layers to weaken the interface, the effect of the composition of the SiC + C interlayers between the layers on the residual stress was evaluated. It was found that the weak SiC + C interlayer had little relaxation effect on the residual stress distribution. These ceramics were then fabricated by aqueous tape casting, stacking, and hot-press sintering. An x-ray stress analyzer was used to test the surface stress conditions of the sintered materials. The tested surface stress of the layered SiC/TiC ceramic without interlayer was very close to the FEM calculation. However, there were differences between the tested and calculated results of the layered SiC/TiC ceramics with interlayers; the reason for this was analyzed.
Dielectric Behavior of Mn-doped Morphotropic Phase Boundary Composition in the Pb(Zn1/3Nb2/3)O3–BaTiO3– PbTiO3 System
Authors: Zhu W. Z. , Yan M. , Kholkin A. L. , Mantas P. Q. , Baptista J. L.
Published: March 2008

The dielectric behavior of manganese-doped morphotropic phase boundary (MPB) composition in the Pb(Zn1/3Nb2/3)O3–BaTiO3–PbTiO3 (PZN–BT–PT) system is described in this paper. Materials with perovskite structure were fabricated using the precursor approach. Addition of Mn stabilized the rhombohedral phase against the tetragonal one, moving the MPB territory toward the PbTiO3-rich side. Both the dielectric permittivity maximum (∈′m) and phase transition temperature (Tmax) were reduced by increasing Mn2+ content. Frequency-dispersion characteristics of Tmax were weakened while the frequency spectrum of the dielectric permittivity (∈′) was broadened, reflecting different underlying mechanisms. The broadness of paraelectric to ferroelectric phase transition was significantly enhanced by Mn-doping. This was associated with progressive increase in the degree of chemical heterogeneity on B-site cations. The observed proximity of the non-Curie–Weiss region to Tmax as well as shrinkage of this region for doped compositions suggest increased stability of the ferroelectric phase.
Cross Effect Between Ion and Electron Flows in Fe3–δO4
Authors: Hong Jeong-Oh , Yoo Han-Ill
Published: March 2008

The effective valence,of mobile cations (Fe2+, Fe3+) in semiconducting Fe3O4was determined at elevated temperatures via Tubandt-type electrotransport experiments in association with the literature data on the cation diffusivity and total electrical conductivity. It has been found that the value forvaries systematically from below 2 up to 3 with oxygen partial pressure at a fixed temperature. The effective valence is determined not only by the mobility difference of Fe2+and Fe3+ionsbut also by the cross effect between the cations and electrons upon their transfer. A value ofbetween 2 and 3 may be attributed to the mobility difference between Fe2+and Fe3+ions even in the absence of the cross effect, but the values of< 2 clearly indicate that the cross effect is in play in Fe3O4.
Deposition of diamond/β–SiC Gradient Composite Films by Microwave Plasma-assisted Chemical Vapor Deposition
Authors: Shi Yulong , Tan Minhui , Jiang X.
Published: March 2008

Mixed-phase diamond/β–SiC composite films with compositional gradient were prepared by microwave plasma-assisted chemical vapor deposition using a gas mixture of hydrogen, methane and tetramethylsilane (TMS). Single-crystalline silicon wafers, pretreated with diamond nanoparticles before deposition, were used as substrates. The film characterization by scanning electron microscopy, electron probe microanalysis, and energy-dispersive x-ray analysis shows that the contents of diamond and silicon carbide in the films vary with TMS flow rate. Diamond/β–SiC composite films with compositional gradients are achievable by varying the TMS flow rate during the film growth process.
Effects of a Nanothin Al2O3 Cathode Buffer Layer on the Characteristics of Organic Light-emitting Diodes with Sputter-deposited Cathodes
Authors: Kho Samil , Bae Sungjun , Jung Donggeun
Published: March 2008

Effects of an Al2O3 nanothin film between the emitting layer and the sputterdeposited cathode were studied for organic light-emitting diodes (OLEDs) with indium–tin–oxide, NN′-dephenyl-NN′-bis)(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine, tris(8-hydroxyquinoline)aluminum (Alq3), and aluminum (Al) as an anode, a hole transport layer, an emitting layer (EML), and a cathode, respectively. The performance of the OLEDs with sputter-deposited Al cathodes was inferior to that of the OLED with the evaporated Al cathode. However, the insertion of an Al2O3 nanothin film with a proper thickness between the EML and the sputter-deposited Al cathode was effective to alleviate performance degradation of the OLEDs with sputter-deposited Al cathodes in current flow and light emission. It is considered that both protection of EML by Al2O3 from the sputtering damage and higher luminance by the presence of a thin insulating layer between the EML and the cathode alleviated performance degradation of the OLED with an Al2O3 cathode buffer layer. The Al2O3 buffer layer could not alleviate quantum efficiency reduction caused by the sputtering damage.
Magnetic Patterns in Hydrothermal Ferrites by Magnetic Force Microscopy
Authors: Dias A. , Vilela J. M. C. , Andrade M. S.
Published: March 2008

Magnetic structure and domains of hydrothermal NiZn ferrites were studied through magnetic force microscopy by using different magnetically characterized tips. The magnetic patterns varied according to the tip employed and were correlated to the magnetic induced field generated by these different coated tips. Low-moment tips were found to be the most adequate to study magnetic domains in these hydrothermal ferrites.
Elastic Recovery Measurements Performed by Atomic Force Microscopy and Standard Nanoindentation on a Co(10.1) Monocrystal
Authors: Arnault J. C. , Mosser A. , Zamfirescu M. , Pelletier H.
Published: March 2008

Atomic force microscopy (AFM) nanoindentation experiments were performed on a Co(10.1) monocrystal. Using AFM line scans, we deduced the elastic recovery, which is an intrinsic parameter of the studied material. The comparison of these elastic recovery values with those calculated by standard nanoindentation shows a fair agreement for forces higher than 400 μN with an important discrepancy for lower forces. This difference is attributed to tip shape effects and to the AFM cantilever elastic deformation. Furthermore, the material hardness was measured from AFM images of the imprint by considering the lateral dimension L. In this case, the obtained values are practically independent from the applied load. Moreover, a simple model based on geometrical considerations is proposed to correct hardness values calculated from the residual depth.
Strong Quantum Confinement in Ordered PbSe Nanowire Arrays
Authors: Peng X. S. , Meng G. W. , Zhang J. , Wang X. F. , Wang C. Z. , Liu X. , Zhang L. D.
Published: March 2008

Ordered PbSe crystalline nanowire arrays have been successfully fabricated in the nanochannels of porous anodic alumina membrane by direct current electrodeposition. X-ray diffraction and selected area electron diffraction investigations demonstrate that the PbSe nanowires have a uniform cubic structure. Electromicroscopy results show that the nanowires are quite ordered with diameters of about 50 nm and lengths up to 5 micrometers. X-ray energy dispersion analysis indicate that Pb:Se is very close to 1:1. The optical absorption spectrum of these PbSe nanowires show that there exist two peaks at 280 and 434 nm, respectively, attribute to excitonic absorption peaks.
Electrolyzed Water as an Alternative for Environmentally Benign Semiconductor Cleaning
Authors: Ryoo Kunkul , Kang Byeongdoo , Sumita Osao
Published: March 2008

The present semiconductor cleaning technology is based upon RCA cleaning [W. Kern and D.A. Puotinen, Cleaning Solutions Based on Hydrogen Peroxide for use in Silicon Semiconductor Technology (RCA Rev., 1970) pp. 187–206], a high-temperature process that consumes vast amounts of chemicals and ultrapure water (UPW) [T. Futatsuki, T. Imaoka, Y. Yamashita, and K. Mitsumori, J. Electrochem. Soc., 142, 966 (1995)]. Therefore, this technology gives rise to many environmental issues, and some alternatives such as electrolyzed water (EW) are being studied. In this work, intentionally contaminated Si wafers were cleaned using electrolyzed water. The electrolyzed water was generated by an electrolysis system that consists of anode, cathode, and middle chambers. Oxidative water and reductive water were obtained in the anode and cathode chambers, respectively. When a NH4Cl electrolyte was supplied in the middle chamber, the oxidation–reduction potential and pH for anode water (AW) and cathode water (CW) were +1050 mV and 4.8, and −750 mV and 10.0, respectively. AW and CW deterioriated after electrolysis but maintained their characteristics for more than 40 min, which was sufficient for cleaning. Their deterioration was correlated with CO2 concentration changes dissolved from air. Contact angles of UPW, AW, and CW on DHF-treated Si wafer surfaces were 65.9°, 66.5°, and 56.8°, respectively, which characterizes clearly the electrolyzed water. To analyze the amount of metallic impurities on Si wafer surface, inductively coupled plasma, mass spectroscopy was introduced. AW was effective for Cu removal, while CW was more effective for Fe removal. To analyze the number of particles on Si wafer surfaces, we used the particle measurement Tencor 6220. The particle distributions after various particle removal processes maintained the same pattern. Overflow of EW during cleaning particles resulted in the same cleanness as that obtained with the RCA cleaning process. The roughness of patterned wafer surfaces after EW cleaning was similar to that of as-received wafers. Regardless of process sequence in this work, RCA consumed about 9 l of chemicals, while EW consumed only 400 ml HCl electrolyte or 600 ml NH4Cl electrolyte to clean 8-in. wafers. It was thus concluded that EW cleaning technology would be very effective for releasing environmental safety, and health issues in the next generation of semiconductor manufacturing.
Adhesion of Cu and low-k Dielectric Thin Films with Tungsten Carbide
Authors: Lemonds A. M. , Kershen K. , Bennett J. , Pfeifer K. , Sun Y-M. , White J. M. , Ekerdt J. G.
Published: March 2008

The adhesion of copper and various dielectric materials to tungsten carbide was studied using interfacial critical debond energies obtained by the four-point flexure method. Tungsten carbide (W2C), films 33.3 nm thick, were vapor deposited onto SiO2, spin-on carbon polymer resin (CPR), chemically vapor deposited organosilicate glass (OSG), and spin-on siloxane-organic polymer (SOP) surfaces using direct-current magnetron sputtering of a W metal target and a methane substrate plasma. Thick copper films (42.5 nm) were vapor deposited onto W2C. Some interfaces were modified by an Ar plasma, 1-nm W deposition, or O2 plasma treatment prior to Cu deposition. A W2C film deposited onto a CPR substrate was annealed for 2 h at 673 K in a 99% N2/1% H2gas mixture. For the untreated dielectric surfaces, the debond energy ranged from 39.9 to 3.95 J/m2. In order of descending adhesion energy, the substrates are ranked CPR, SiO2, SOP, and OSG. Ar plasma treatment of the SiO2 surface increased the debond energy from 20.3 to 41.3 J/m2. The Cu/W2C debond energy was 20.4 J/m2. Ar plasma or 1-nm W deposition treatment to the carbide surface moved the point of delamination from the Cu/W2C interface to the W2C/CPR interface for a Cu/W2C/CPR multilayer structure.
Interfacial Structure and Electrical Characteristics of LaNiO3/Si Contacts
Authors: Wu Tai-Bor , Liu Chin-Lin , Liu Yu-Wen
Published: March 2008

The LaNiO3 (LNO) thin films were deposited on Si substrate by rf magnetron sputtering. The interface and electrical properties of LNO/Si contacts were investigated. For the deposition at room temperature, an amorphous LNO film with a clean interface was formed on the Si. However, a thin silicon oxide layer of approximately 2.5 nm was formed at the interface between LNO and Si after rapid thermal annealing (RTA) at temperatures ≥450 °C. On the other hand, a highly (100)-textured LNO film along with an interfacial oxide layer of approximately 6.0 nm was obtained for the deposition at 400–450 °C. Nevertheless, if an ion beam etching was applied prior to the high temperature deposition at 400–450 °C, a clean interface at the interface could be obtained for the LNO/Si contacts. Moreover, crystallites with (111) planes grown epitaxially along the (111) planes of Si were found in the LNO films. All the contacts had shown good current–voltage characteristics of a Schottky diode with a barrier height of 0.69–0.78 eV for the LNO/n-Si contacts and 0.60–0.67 eV for the LNO/p-Si contacts, and the barrier height increased with the thickening of interfacial oxide layer. From the measurement of capacitance (C) under reverse bias (Vr) of the contacts made with LNO deposited on the ion-etched Si substrates, a linear relation was observed in the plot of C−2 against Vr except a deviation of linearity in the low-bias part of the curve. This deviation is most likely due to the segregation and inward diffusion of La and Ni near the interface of LNO/Si contacts. Nevertheless, the barrier heights evaluated from an extrapolation of linear part of the plots are reasonably consistent with those obtained from the I–V measurement.
Structural and Mechanical Properties of TiC/Ti and TiC/B4C Multilayers Deposited by Pulsed Laser Deposition
Authors: Phani A. R. , Krzanowski J. E. , Nainaparampil J. J.
Published: March 2008

Multilayers of TiC/Ti and TiC/B4C have been deposited by pulsed laser deposition. Ti, B4C, and TiC targets were used to deposit multilayer films onto 440C steel and silicon substrates at 40 °C. The structural, compositional, and mechanical properties of the multilayers were examined by x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, and nanoindentation techniques. Tribological properties were also evaluated using a pin-on-disc friction and wear test. The TiC/Ti films were found to have a crystalline structure, and both (200)TiC/(100)Ti and (111)TiC/(101)Ti orientation relationships were found in these films. In the TiC/B4C films, only the sample with the largest bilayer thickness (25 nm) had significant crystallinity and only the TiC layer was crystalline. X-ray photoelectron spectroscopy depth profiles confirmed the presence of composition modulations in these films. Nanoindentation tests of the TiC/Ti multilayers showed hardness levels exceeding that predicted by the rule-of-mixtures. The TiC/B4C multilayers showed increasing hardness with decreasing bilayer thickness but reached only 22 GPa. The pin-on-disc tests gave friction values ranging from 0.3 to 0.9 for both sets of films. These results were correlated with the degree of crystallinity and grain structure of the films.
Synthesis and Characterization of Particle-reinforced Ni/Al2O3Nanocomposites
Authors: Shao I. , Vereecken P. M. , Chien C. L. , Searson P. C. , Cammarata R. C.
Published: March 2008

Nanocomposite Ni/Al2O3films were electrodeposited from a suspension of Al2O3nanoparticles in aqueous nickel sulfamate solution. The volume fraction of particles incorporated increased with electrode rotation rate and decreased with deposition current density. The composition, microstructure, hardness, and magnetic properties of these nanocomposite films were characterized. The mechanical strengthening due to particle dispersion in the films was interpreted by considering an Orowan dislocation bowing mechanism. The coercivity of the films increased with increasing particle concentration in the film. The saturation magnetization showed a weak dependence on particle concentration.
Effect of Ni Substitution on the Structure and Photocatalytic Activity of InTaO4 Under Visible Light Irradiation
Authors: Zou Zhigang , Ye Jinhua , Arakawa Hironori
Published: March 2008

The effect of Ni substitution on the structure and photocatalytic H2 and O2 evolutions of InTaO4 under visible light irradiation (λ > 420 nm) from aqueous CH3OH/H2O and AgNO3/H2O solutions were investigated. The photocatalysts were prepared by the solid-state reaction method and characterized by powder x-ray diffraction and Rietveld structure refinement. These photocatalysts crystallize in the same wolframite structure, but lattice parameters decrease with increase of x in In1−xNixTaO4 (0 ≤x ≤ 0.2). The photocatalytic activity changed with the variation of x in In1−xNixTaO4and the photocatalyst at x = 0.1 showed the highest activity, which increased 8 times compared with nonsubstituted photocatalyst.
Crystallization Kinetics of Sol-gel-derived (1x)SrBi2Ta2O9–xBi3TiTaO9Ferroelectric Thin Films
Authors: Kwak Woo-Chul , Sung Yun-Mo
Published: March 2008

The crystallization kinetics of Sr0.7Bi2.3Ta2O9(SBT) and 0.7SrBi2Ta2O9–0.3Bi3TiTaO9(SBT-BTT) thin films formed by the sol-gel and spin coating techniques were studied. Phase formation and crystal growth are greatly affected by the film composition and crystallization temperature. Isothermal kinetic analysis was performed on the x-ray diffraction results of the thin films heated in the range of 730 to 760 °C at 10 °C intervals. Activation energy and Avrami exponent values were determined for the fluorite-to-Aurivillus phase transformation. A reduction of approximately 51 kJ/mol in activation energy was observed for the SBT-BTT thin films, and an Avrami exponent value of approximately 1.0 was obtained for both the SBT and SBT-BTT. A comparison is made, and the possible crystallization mechanism is discussed.
Optical Properties of Laser-dye-doped Polyvinylcarbazole Films Coated with Polycarbonate
Authors: Arena A. , Bonsignore F. , Patanè S. , Saitta G.
Published: March 2008

Spectrophotometry in the ultraviolet-visible-infrared range was used to investigate the optical properties of polymer bilayers obtained by spin coating polycarbonate films about 1 μm thick on top of pyrromethene-doped polyvinylcarbazole (PVK) layers deposited on glass. Due to the light confinement in the PVK plane, the laser-dye photoluminescence collected along the polymer plane was linearly polarized and shifted from green to yellow according to the active film thickness. To laterally contain light, microstructures were imprinted on laser-dye-doped PVK films by soft lithography. The photoluminescence coming out of a microstructured film and the film topography were analyzed by scanning near-field optical microscopy.
Direct Conversion of TiO2 Sol to Nanocrystalline Anatase at 85 °C
Authors: Gnanasekar K. I. , Subramanian V. , Robinson J. , Gnanasekar K. I. , Gnanasekar K. I. , Gnanasekar K. I. , Jiang J. C. , Posey Fanney E. , Rambabu B.
Published: March 2008

Nanocrystalline TiO2 anatase with particle size in the range of 5–7 nm has been prepared by in situ cracking of the sol at 85 °C, thereby avoiding the intermediate gel formation process. Hydrolysis of Ti(O-isoPr)4 was carried out in excess of 2-propanol to keep the suspension of fine particles from agglomeration. Differential thermal analysis, thermogravimetric analysis, differential scanning calorimetry, powder x-ray diffraction (XRD), and electron microscopy have been used to characterize the samples. Gel to crystalline conversion, which requires a temperature of at least 400 °C, can be achieved by digesting the TiO2 sol at 85 °C. XRD and selected area electron diffraction patterns show the presence of a small amount of brookite phase along with the major anatase phase. High-resolution transmission electron microscopy shows that the average grain size of TiO2 particle remains around 5–9 nm even when heated at 510 °C.
Sn-doped BaO–TiO2–ZnO Microwave Ceramics
Authors: Shunhua Wu , Guoqing Wang , Yushuang Zhao
Published: March 2008

Sn-doped BaO–TiO2–ZnO (BTZ) microwave ceramic materials were investigated as a function of SnO2 content. Addition of a small amount of SnO2 (0.01–0.06 wt%) lowered the sintering temperature of the system to 1160 °C and also greatly reduced the dielectric loss (tan δ), which is closely related to the insulation resistivity. The Sn-doped BTZ materials were found to have excellent dielectric properties at 1 GHz with dielectric constant Ε ≈tangent tan δ ≤ 1 × 10−4, temperature coefficient of dielectric constant, αΕ = 0 ± 30 ppm/°C, and volume resistivity ρv ≥ 1013 ω cm.
Novel Time-modulated Chemical Vapor Deposition Process for Growing Diamond Films
Authors: Fan Q. H. , Ali N. , Kousar Y. , Ahmed W. , Gracio J.
Published: March 2008

Smooth polycrystalline diamond films were deposited onto silicon substrates using a newly developed time-modulated chemical vapor deposition (TMCVD) process. The distinctive feature of the TMCVD process involves pulsing the hydrocarbon gas, methane, at different flow rates for varying durations into the vacuum reactor during the chemical vapor deposition (CVD) process. Generally, CVD diamond films display nonuniformity in the crystal sizes and surface roughness along the film growth profile. The TMCVD method was specifically developed to (i) deposit smooth films, (ii) control film microstructure and morphology, and (iii) improve film reliability. We show that the TMCVD process produces diamond films with improved surface smoothness as compared to films of similar thickness produced by conventional CVD method under similar conditions. Surprisingly perhaps, the TMCVD method gave growth rates much higher than the conventional CVD method without reducing the film quality as revealed by the SEM micrographs and micro-Raman spectra.
Structure of Milled Galena (PbS) Particles as a Result of Grinding: Observations by Electron Microscopy
Authors: Martinetto P. , Castaing J. , Walter P. , Penhoud P. , Veyssière P.
Published: March 2008

We have examined galena powders with the aim of providing information about the preparation mode of such powders from ancient Egyptian burial objects. Two extreme conditions of milling have been used to prepare galena powders in the laboratory, and the resulting products have been examined using scanning electron microscopy and transmission electron microscopy (TEM). The microstructure of hand-crushed coarse particles consists mainly of dislocation tangles. Annealing at 300 °C promotes a substantial recovery of the dislocation structure with the formation of subboundaries. Energetic ball milling produces a large variety of particle sizes, from 10 nm to several micrometers, with grains containing very high dislocation densities. Although PbS is a soft plastic compound, its fragmentation occurs down to very small sizes along various fracture regimes like in many brittle materials. Comparisons are made between TEM observations and the data obtained from x-ray diffraction peak profile analysis.
Surface Structural Characterization and Mechanical Testing by Nanoindentation Measurements of Hybrid Polymer/clay Nanostructured Multilayer Films
Authors: Fan Xiaowu , Park Mi-Kyoung , Xia Chuanjun , Advincula Rigoberto
Published: March 2008

Nanostructured montmorillonite/poly(diallyldimethylammonium chloride) multilayer thin films were fabricated up to 100 layers thick by stepwise alternating polyelectrolyte and clay deposition from solution. The structure and morphology of the films were characterized by x-ray diffraction, ellipsometry, atomic force microscopy, and quartz crystal microbalance ex situ and in situ measurements. The mechanical properties were tested by nanoindentation. The hardness of the multilayer thin film was 0.46 GPa. The thin film's modulus was correlated to its ordering and anisotropic structure. Both hardness and modulus of this composite film were higher than those of several other types of polymer thin films.
Fabrication of Device-grade Separation-by-implantation-of-oxygen Materials by Optimizing Dose-energy Match
Authors: Chen Meng , Yu Yuehui , Wang Xi , Wang Xiang , Chen Jing , Liu Xianghua , Dong Yeming
Published: March 2008

In this article, we report formation of separation-by-implantation-of-oxygen (SIMOX) silicon-on-insulator (SOI) materials with doses ranging from (2.5 to 13.5) × 1017 cm−2 at acceleration energies of 70–160 keV and subsequent annealing at temperatures over 1300 °C in oxygen + argon atmosphere for 5 h. The microstructure evolution of SIMOX wafers was characterized by Rutherford backscattering spectroscopy, cross-sectional transmission electron microscopy, high-resolution transmission electron microscopy, Secco, and Cu-plating. This study revealed a series of good matches of dose-energy combination at acceleration energies of 70–160 keV with doses of (2.5–5.5) × 1017 cm−2, in which SIMOX wafers had good crystallinity of the top silicon, sharp Si/SiO2 interfaces, high-integrity buried oxide layers with low pinhole density, and low detectable silicon islands. Furthermore, the higher the oxygen dose, the higher the implanted energy required for the formation of a buried oxide free from Si islands. The mechanism of the optimum dose-energy match is discussed.
Textured ZnO Thin Films on (0001) Sapphire Produced by Chemical Solution Deposition
Authors: Wessler B. , Lange F. F. , Mader W.
Published: March 2008

Highly textured zinc oxide films were produced on basal plane sapphire substrates by chemical solution deposition. Films with oriented growth were achieved by spin coating a 0.75 M precursor solution of zinc acetate dihydrate and ethanolamine in 2-methoxyethanol, heated at 300 °C/10 min, then at 500 °C/5 h, and finally at 850 °C/12 h. Films were characterized with x-ray diffraction (XRD) and scanning and transmission electron microscopy. The films exhibited only the (0002) ZnO line in XRD diagrams, proving a very well-developed out-of-plane texture. At temperatures above 700 °C the ZnAl2O4 spinel was observed, which formed as a reaction layer between sapphire and ZnO. Few specimens produced both in-plane and out-of-plane oriented growth of ZnO on basal plane sapphire. It was hypothesized that the substrate miscut, uncontrolled for the current experiments, could be the cause of the infrequent growth of epitaxial films.
Combustion Synthesis of TiN Induced by High-energy Ball Milling of Ti Under Nitrogen Atmosphere
Authors: Gotor F. J. , Alcalá M. D. , Real C. , Criado J. M.
Published: March 2008

A planetary ball-mill device that enables one to perform solid-gas reactions at constant pressure was developed. Titanium powders were ball milled under nitrogen at a spinning rate of 960 rpm. The influence of the nitrogen pressure on the mechanochemical reactivity of titanium was analyzed at 1.5 and 11 bars. A spontaneous combustion took place during the grinding process, leading to a high yield of TiN for short milling times. The conversion of titanium into titanium nitride was facilitated by increasing the nitrogen pressure. At 11 bars, full conversion was reached for grinding times shorter than 5 h. Titanium nitride obtained in this way exhibited a high sintering activity.
Chemical Solution Deposition of <100>-oriented SrTiO3 Buffer Layers on Ni Substrates
Authors: Dawley J. T. , Ong R. J. , Clem P. G.
Published: March 2008

Biaxially textured <100>-oriented SrTiO3 films were solution deposited on <100> LaAlO3 single crystals and <100>-oriented polycrystalline Ni tapes. Solution variables including varying titanium alkoxide chain length, inclusion of chelating agents, and inclusion of donor dopant, were investigated for their effect on film orientation, morphology, and oxygen diffusivity. The best <100> SrTiO3 orientation on high lattice mismatch (11%) Ni substrates was achieved through use of a discontinuous nucleation seed layer, which provided nucleation sites for subsequent continuous SrTiO3 films. Increased titanium alkoxide chain lengths appeared to suppress titanium hydrolysis reactions and improve film orientation. 13C nuclear magnetic resonance showed that significant quantities of water were generated due to esterification reactions, which appeared to cause hydrolysis and subsequent orientation degradation in the absence of chelating agents such as acetylacetone.
Electron Cyclotron Resonance Plasma-assisted Reactive Pulsed Laser Deposition of Compound Films
Authors: Sun J. , Wu J. D. , Ling H. , Shi W. , Ying Z. F. , Li F. M.
Published: March 2008

A novel method was developed for low-temperature preparation of thin films. Pulsed laser ablation was combined with electron cyclotron resonance microwave discharge, constituting a novel hybrid film preparation method called electron cyclotron resonance plasma–assisted reactive pulsed laser deposition. We demonstrated the feasibility of the method by preparing compound films of silicon nitride, silicon dioxide, and aluminum nitride from elemental starting materials. The mechanisms responsible for efficient compound formation and film growth are discussed, together with characterization of the prepared films, analysis of the plasma composition, and comparison of the films prepared with and without assistance of the plasma. The unique features of the method make it suitable for one-step preparation of compound thin films at low temperatures.
Highly Ordered and Well-oriented Single-crystal CdTe Nanowire Arrays by Direct-current Electrodeposition
Authors: Xu Dongsheng , Guo Yuguo , Yu Dapeng , Guo Guolin , Tang Youqi , Yu D. P.
Published: March 2008

Highly ordered CdTe nanowire arrays were prepared by electrochemical deposition into the pores of anodic aluminum oxide templates from an ethylene glycol bath containing CdCl2, TeCl4, and KI. Electron microscopy results showed that the length, diameter, and direction of growth of the nanowires were quite uniform. X-ray diffraction, transmission electron microscopy, and high-resolution electron microscopy investigations showed that these nanowires had a crystalline structure of hexagonal CdTe single crystal with a uniform [001] growth direction.
Surface and Bulk Properties of Alumina Recovered Under Various Conditions from Aluminum Dross Tailings Chemical Waste Versus Bauxite Ore
Authors: El Ezzat A. , Halawy Samih A. , Mohamed Mohamed A. , Zaki Mohamed I.
Published: March 2008

Bauxite ore (industrial raw material) and aluminum dross tailings (a local industrial waste material of the Aluminium Company of Egypt, Egyptalum) were used as two different parent materials to produce alumina. A set of six different preparation methods was applied to aluminum extracts from both materials. X-ray powder diffractometry, thermal and chemical analyses, and surface area and charge measurements were used to characterize the alumina products. The results indicate that catalytic grade, high-purity alumina products of uniform particle sizes could be obtained in large yields, depending solely on the preparation method applied, i.e., irrespective of the raw material used. Thus, aluminum dross tailings chemical waste is proved to be a feasible parent material for specialty alumina, which is an important finding both economically and environmentally.