bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study on unique Crystal Morphology observed in the Polycrystalline Copper CVD
Authors: Chang Yuneng , Chen Yalian , Chen Kuanhon 
Published: April 2011

ABSTRACTNanostructure copper whisker growth was observed in an atmospheric pressure chemical vapor deposition (CVD) system, which used copper acetylacetonate vapor and 10-15 torr of water vapor as reactants, with 0.04-0.10 torr of chromium acetylacetonate vapor added as growth promoting catalyst. Water vapor initiated nucleation of these helical, spiral shape Cu(111) and (200) polycrystalline whiskers. While chromium acetylacetonate accelerated the growth rate. Copper whiskers had radii from 0.1 to 0.24 μm, lengths from 1 to 10 μm, and distribution density of 0.20-3.6 whiskers/μm2. Dependence of such whisker characteristics on temperature, partial pressures of H2O and chromium acetylacetonate was used to construct a kinetic model. From the Arrhenius equation, data analysis for whisker growth rate against deposition temperature showed that the activation energy for whisker growth along radial direction is 12.4 kcal/mol, and 19.6 kcal/mol for growth along axial direction. Based on such data and SEM observations, a base vapor-liquid-solid (VLS) model involving BCF theory was proposed to describe the governing mechanism for the axial growth. This model interpreted the competitive growth phenomena in both radial and axial directions, and controlling steps for radial and axial growth being assigned to mass transfer and surface reaction, respectively.
Effects of Non-Planar Surfaces on the Growth of RF Magnetron Sputtered ZnO
Authors: Holland A.S. , Reeves G.K. , Leech P.W. 
Published: April 2011

ABSTRACTThis paper describes the influence of the topography of a lithographically patterned substrate (aluminium electrodes on a CVD diamond film) on the uniformity of sputtered ZnO films. Diamond films with an average surface roughness of ∼1nm, had aluminium electrodes (thickness 80nm, linewidth/space 2.6μm) patterned on them. ZnO was RF sputtered on to the substrate and the uniformity of the ZnO grain structure was examined using SEM, XRD and AFM. Abrupt changes in topography at the edges of the aluminium electrodes resulted in poor alignment of ZnO grains. SEM/AFM micrographs show misalignment of ZnO grains at the edges of the raised electrodes. When the electrodes were recessed into the diamond film, using a damascene-like process, the SEM/AFM micrographs showed improved grain uniformity of ZnO. XRD showed a significant increase in the c-axis (002) orientation and an absence of the (101) orientation. AFM micrographs also showed the improvement in the ZnO surface topography. These results may be of significance to high frequency Surface Acoustic Wave (SAW) devices.
Preparation and characterization of (Ba,Sr)TiO3 thin films by liquid source chemical vapor deposition
Authors: Yang Cheol-Hoon , Han Young-Ki , Kim Dong-Hyun , Han Geun-Jo , Yang Doo-Young , Oh Ki-Young , Song Juho , Park Jaehoo , Hwang Cheol-Seong 
Published: April 2011

ABSTRACTThe cocktail source of BST was prepared by mixing of Ba, Sr, and Ti precursor solution with specific mole ratio. This cocktail source was vaporized and delivered into the warm wall reactor by liquid delivery system(LDS) and gaseous source was distributed by simple structure of gas injector instead of showerhead system. The thickness uniformity of BST on 8 inch wafers were less than 3%. The Ti composition uniformity of our films were less than the 1 at%(1σ ) at stoichiometric and near stoichiometric. Their dielectric constant was about 230 and leakage current density was lower than 10-8 A/cm2 under ±1V bias. Excellent step coverage and smooth (haze-free) surface morphology of BST films were obtained by a deposition using a noble dome type reactor. The merit of our warm wall type reactor also will be explained by excellent step coverage and the uniform composition with 3 dimensional structure. Our achievement should be applicable to the capacitor of next generation DRAM.
Evolution of Coherent InAs Quantum Dots Above the Coherent Critical Thickness Window by Metalorganic Chemical Vapor Deposition
Authors: Yeoh T. S. , Liu C. P. , Kim Y. W. , Coleman J. J. 
Published: April 2011

ABSTRACTInAs quantum dots were grown on GaAs substrates at various coverages and capped after varying the time of growth interruption. The evolution of this system was examined by correlating photoluminescence and transmission electron microscopy measurements. Results show for the first time the growth interruption to be a critical factor in generating defect-free quantum dot ensembles at coverages well above established metalorganic chemical vapor deposition coverage window for defect-free, Stranski-Krastanow self-organized growth. In addition, our results also support the absence of a stable, dislocation free 3D state and that the chemical potential eventually drives the system towards dislocated quantum dot clusters.
Synthesis of Tin Oxide Thin Films by Pulsed Laser Deposition Using SnO2Targets
Authors: Suda Yoshiaki , Kawasaki Hiroharu , Doi Kazuya , Nanba Jun , Wada Kenji , Ebihara Kenji , Ohshima Tamiko 
Published: April 2011

ABSTRACTTin oxide (SnO2) thin films have been grown on Si (100) and Al2O3 substrates by pulsed Nd:YAG (532nm) and KrF excimer (248 nm) laser deposition methods using SnO2 targets. X-ray diffraction measurement showed that the almost amorphous microstructure transformed into a crystalline SnO2 phase and preferred orientation varied from (101) to (110) on Si (100) with increasing oxygen gas pressure. This result suggests that oxygen gas pressure affects the phase formation, crystalline structure and preferred orientation of the films. Gas sensing properties of SnO2 thin films by PLD method were also investigated over the temperature range 300 – 600°C, using 0.31vol%H2 as a test gas. The oxygen gas pressure results in a notable change in gas sensing properties of SnO2 thin films.
Microstructure Origin for Thermal Fatigue of TiNi Films
Authors: Wen Shulin , He Jibao 
Published: April 2011

ABSTRACTIn order to improve the performance and prolong the life of shape memory alloy material (SMA), it is very important to trace and study the microstructure change on the fatigue of SMA. The microstructure features between the samples before and after thermal fatigue (about 100,000 thermal cycles) of the NiTi-SMA films were examined and compared with each other by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). It was found that there is no difference of microstructures between the two kinds of samples except some precipitates appeared in the fatigue specimen. These precipitates which may be identified as TiNi3phase with a grain size of 10-20 nm may impede transformation from martensite to austenite which works as mechanism of SMA during thermal fatigue. Therefore, these precipitates result in the serious decay on SMA performance and further fracture of the SMA material.
Plasma Diagnostics and the Evolution of a Novel Titanium Nitride Deposition Process
Authors: Muratore Chris , Moore John J. , Rees J. Alan , Carter Dan , Roche Greg 
Published: April 2011

ABSTRACTMeasurement of the ion energy distributions (IED's) of N2+ ions produced in an inductively coupled plasma (ICP) source revealed that adding argon to the nitrogen gas before excitation in the source increased the nitrogen ion current. Adding helium resulted in an increase of the most probable ion energy, and a higher-energy component of the N2+ IED at about 20 eV. Preliminary calculations of the electron energy distributions (EED's) correlate well to the IED's for both inert gas additions. Experiments were performed to determine the effect of these modified energy distributions of the reactive species on titanium nitride thin film growth rates, microstructure and mechanical properties. Deposition experiments were conducted using the ICP source and an unbalanced magnetron with a titanium cathode. Results showed that the argon inert gas addition resulted in increased deposition rate and reduced 3-D features. Film roughness was decreased to 1.61 nm from 2.05 nm when helium was mixed with the nitrogen. Mixing both argon and helium with the nitrogen yielded combined effects of deposition rate increase, reduced 3-D features and increased smoothness. The inert gas additions increased hardness of the TiN films from 17.3 GPa to 21.1 GPa with the argon addition and to 25.0 GPa with the helium addition
Texture Evolution in Al(Cu) Interconnect Materials
Authors: Murray C.E. , Rodbell K.P. 
Published: April 2011

ABSTRACTAn investigation of the microstructural evolution of Al(Cu) thin films deposited on a variety of interlevel dielectric (ILD) layers was performed. A combination of X-ray texture measurements and scanning electron microscopy (SEM) was employed to link the texture behavior of the as-deposited Al(Cu) films at different thicknesses to the observed morphological development within the films. Three regimes of texture were revealed, corresponding to (1): Al(Cu) island growth and individual island coalescence, (2): fully coalesced film and the onset of grain growth and (3): extensive grain growth. The first and last of these regimes exhibited offset (111) texture, in which the maximum diffracted intensity from Al (111) is offset from the substrate normal. However, the position of maximum offset texture differed between the first and third stages of growth, indicating that two different mechanisms were responsible. The offset (111) texture observed in the third regime of Al(Cu) film microstructure was due to the faceting of grain surfaces. The time required for the films to reach these three stages depended on the effective diffusivity of the Al atoms on the ILD surfaces, which differed in chemistry and topography.
Room-Temperature UHV-Deposited Titanium Monoxide Films on Oxidized Polycrystalline Copper
Authors: Fuenzalida V. M. , Grahmann C. R. , Herrera C. , Zárate R. A. , Avila C. , Pilleux M.E. 
Published: April 2011

ABSTRACTPolycrystalline copper films thicker than 100 nm were evaporated on silicon wafers with their native oxide under ultrahigh vacuum conditions leading to an rms roughness of ~2 nm of the copper film. X-ray photoelectron spectroscopy (XPS) revealed a clean copper surface with only traces of oxygen. The samples were exposed to air, leading to an oxide film consisting of CuO. TiO films were subsequently deposited onto the oxidized copper films from a resistively heated tungsten boat with the substrate at room temperature. The TiO films exhibited good adherence and were amorphous. XPS measurements revealed that the TiO films were contamination-free and that the first layers of TiO reduced the thin native oxide of the copper substrate from Cu(II) into Cu(I) or Cu(0) and transformed the TiO into TiO2 at the interface.
A Surface Insulator-to-Conductor Phase Transition in Colossal Magnetoresistive Manganese Perovskites Thin Films
Authors: Borca C.N. , Xu Bo , Komesu Takashi , Jeong Hae-Kyung , Liou S.-H. , Dowben P.A. 
Published: April 2011

ABSTRACTWe have observed a distinct surface phase transition for an important class of colossal magnetoresistive materials, La0.65D0.35MnO3 (with D = Sr, Pb) occurring in a surface layer compositionally different from the bulk. The surface phase transition occurs around 240 K compared to350 K for the bulk and is fundamentally different. In the bulk, a ferromagnetic metal to paramagnetic ‘bad metal’ occurs, while the lower-temperature surface transition is from an n-type (in case of La0.65D0.35MnO3) or a p-type (in case of La0.65D0.35MnO3) semiconductor to a semimetal with increasing temperature.
Magnetic characterization of (001) and (111) Ni films epitaxially grown on MgO
Authors: Lukaszew R. A. , Stoica V. , Clarke R. 
Published: April 2011

ABSTRACTOne interesting application of epitaxial magnetic thin films is to use them as one of the electrodes in a spin-dependent tunneling junction, in order to use the magnetocrystalline anisotropy to define the required two states of the magnetization. [1] In our preliminary work, we prepared epitaxial magnetic films on copper buffer layers grown on silicon substrates. [2] The single crystalline quality of the films was particularly evident in the magnetization hysteresis loops, showing a sharp reversal at fairly high fields (120 Oe), when the samples were magnetized along the crystallographic easy axis. One technological disadvantage in this type of samples is the chemical interaction between the metallic layers and the silicon substrate.In order to explore the possibility of epitaxial magnetic films on less reactive substrates, we studied the growth on MgO substrates. We have shown that it is possible to obtain epitaxial (001) and (111) Ni films grown on MgO substrates. [3] In particular we observed that the crystalline quality of the films improved considerably after 10 nm of film growth. We will now present our studies on the magnetic properties of these films, particularly the azimuthal dependence of the magnetization reversal using MOKRE, correlating our finding with the structural characterization obtained with RHEED, STM and XRD.
Magnetic Properties and Scaling Behavior in Perovskite–like La0.7(Ba1−xPbx)0.3CoO3 System
Authors: Chen Chiung-Hsiung , Huang Ting-Sheng , Tai Ming-Fong 
Published: April 2011

ABSTRACTIn this study, we used x-ray diffraction patterns and dc magnetic measurements to investigate the crystallographic structure, magnetic properties and scaling behavior of the distorted perovskite La0.7(Ba1−xPbx)0.3CoO3 (0 ≤ x ≤ 0.5) system with a constant ratio of Co4+/Co3+. Samples with x = 0.0 and 0.1 were crystallized in the cubic structure with a ∼ 7.76 Å whereas samples with x ≥ 0.2 were crystallized in an orthorhombic Pbnm space group with a ∼ b ∼ 5.50 Å and c ∼ 7.85 Å. For all our samples the spin-glass-like behavior were observed in low temperature and low field ranges. The Pb2+ substitution on Ba2+ site does not significantly affect the ferromagnetic transition temperature TC, but does introduce large variation in the magnetic strength. In both the ferromagnetic and paramagnetic states the minimum values of the average effective moments provided by every Co ion occur at x = 0.3. We also observed the scaling behaviors of magnetic data in all samples. The derived values of the critical exponents (β, γ, δ) were consistent with those predicted by mean field theory and a three-dimensional Heisenberg model.
A Landau-Ginzburg Description of Sb Overlayers
Authors: Skomski R. , Komesu T. , Jeong H.-K. , Borca C. N. , Dowben P. A. , Ristoiu D. , Nozieres J. P. 
Published: April 2011

ABSTRACTThe spin polarization of Sb overlayers on the semi-Heusler alloy NiMnSb is investigated in terms of the Landau-Ginzburg approach. The half-metallic semi-Heusler alloy NiMnSb acts as a ferromagnetic perturbation and induces a spin polarization in the semimetallic Sb overlayer. Using a Gaussian approximation, the propagation of the spin perturbation in the overlayer is calculated. The results are compared with spin-polarized inverse photoemission spectroscopy (SPIPES) results and with recent spin-dependent envelope-function approximation (SDEFA) predictions. The Landau-Ginzburg parameters are both band-structure and temperature dependent, and it is argued that thermal spin excitations lead to an injection depth decreasing as 1//T law at high temperatures.
Spontaneous Ac Field Induced Mechanical Rotation in Magnetostrictive Fesib-Based Wires Subjected to Thermal Treatments
Authors: Raposo V. , Mitra A. , Vázquez M. 
Published: April 2011

ABSTRACTAn astonishing new phenomenon has been recently observed in magnetic wires. It consists of the spontaneous rotation of the wires when submitted to an exciting AC axial field with frequency of the order of kHz and amplitude above some threshold. The rotation is believed to appear due to interaction between generated magnetoelastic standing waves and induced eddy currents. In the present work rotational characteristics of Fe77.5Si7.5B15 and Fe73.5Si13.5B9Cu1Nb3wires in their as-cast amorphous state and after heat treatments leading to devitrification has been investigated. It is proved that this rotational phenomenon is only observed in samples with large enough magnetostriction irrespective of their structural character. Moreover, changes in rotational characteristics are ascribed to the structural modifications accompanying the devitrification process.
Domain Structure of ‘Thick’ Amorphous Microwires with Nearly Zero Magnetostriction
Authors: Chiriac Horia , Óvári Tibor-Adrian , Takajo Minoru , Yamasaki Jiro , Zhukov Arcady 
Published: April 2011

ABSTRACTNearly zero magnetostrictive glass-coated amorphous microwires are suitable materials for sensor applications. Samples with metallic core diameters below 20 [.proportional]m exhibit almost nonhysteretic BH loop, related to the existence of a domain structure with azimuthal easy axis. The magnetic behavior of these microwires is changing drastically when the metallic core diameter increases over 25 [.proportional]m, i.e. they display a bistable magnetic behavior at low fields, that is a one step magnetization reversal at a certain value of the applied field, called switching field. Results on the direct domain observation in nearly zero magnetostrictive Co68.25Fe4.5Si12.25B15 glass-coated amorphous microwires by means of Kerr microscopy are reported for the first time. The effect of glass removal on the domain structure has been also studied. AC hysteresis loop measurements have been employed to establish a correlation between domain structure and magnetic behavior.Glass-coated microwires exhibit a single domain configuration with the magnetization pointing mostly to the wire axis. The domain structure does not change qualitatively after glass removal, but the parameters of the squared hysteresis loops are modified. The remanence to saturation ratio increases after glass removal, while the switching field decreases.The obtained results are of interest for sensor applications, and show that the metallic core diameter is a dimensional factor that contributes to important changes in the domain structure and magnetization process of such microwires.
Progress of the Phase-change Optical Disk Memory
Authors: Ohta Takeo , Yamada Noboru , Yamamoto Hiroaki , Mitsuyu Tsuneo , Kozaki Takashi , Qiu Jianrong , Hirao Kazuyuki 
Published: April 2011

ABSTRACTOptical memory has two recording modes: the photon-mode as a silver halide photograph and the heat-mode as a laser optical disk. Though laser heat-mode recording has the advantage of environmental stability, it has limitations due to thermal diffusion phenomena, which will be discussed in this paper.
Incorporation of Hydrogen and Oxygen into (t)a-C:H Thin Films Deposited using DECR plasma (*)
Authors: Piazza Fabrice , Grambole Dieter , Herrmann Folker , Relihan Gary , Barthe Marie France , Desgardin Pierre , Golanski André 
Published: April 2011

ABSTRACTA distributed electron cyclotron resonance (DECR) plasma reactor powered by a microwave generator operating at 2.45 GHz (800 W) was used to deposit (t)a-C:H thin films at RT on <100> Si substrates RF biased within the range 25≤|V0|≤600 V.C2H2 was used as precursor. The plasma pressure was varied within the range 0.1≤P≤1.5 mtorr. The films were analysed using spectroscopic ellipsometry (SE) and Fourier transform infrared (FTIR) spectroscopy. The hydrogen content NH and the density of the films were determined from nuclear reaction analysis (NRA) using the resonance at 6.385 MeV of the reaction: 15N + 1H → 12C + 4He + γ. Positron annihilation spectroscopy was used to detect the porosity. The evolutions of NH as a function of the substrate ion current density n+ and as a function of V0 show that the hydrogen incorporation results from the competition between chemisorption and deposited energy density related effects. The increase of the hydrogen incorporation leads to a decrease in the film density and a lower deposition rate. The porosity of the films deposited at low pressure (∼0.1 mTorr) with V0= −80 V has been detected. The comparison between results of SRIM-2000 simulations and the evolution of NH as a function of V0 shows that the porosity and the hydrogen content are not correlated. The absorption of oxygen and nitrogen for the low density films has been detected from the observation of the 3250–4000 cm-1infra-red (IR) band.
Preparation and properties of amorphous carbon oxynitrides a-CNxOy films made by a nitrogen radical sputter method and by the layer-by-layer method
Authors: Naruse Yohko , Nitta Shoji , Habuchi Hitoe 
Published: April 2011

ABSTRACTWe have tried to prepare amorphous carbon oxynitrides (a-CNxOy)films by the oxygen radical treatment (ORT) of amorphous carbon nitrides (a-CNx) and also by the layer-by-layer method. Properties of a-CNxOy films were studied with X-ray photoelectron spectroscopy (XPS), photothermal deflection spectroscopy (PDS), ultraviolet-visible (UV-VIS) optical transmittance spectra, Raman spectra and electron spin resonance (ESR). Oxygen radical affects to a-CNx by etching, termination of defects and oxidation. A-CNxOy films are interesting for the application to luminescent materials and also to low dielectric consta nt materials.
A Model to Interpret the Raman Spectra of Disordered, Amorphous and Nanostructured Carbons
Authors: Ferrari Andrea Carlo 
Published: April 2011

ABSTRACTRaman spectroscopy is a very popular, non-destructive tool for the structural characterisation of carbons. Raman scattering from carbons is always a resonant process, in which those configurations whose band gaps match the excitation energy are preferentially excited. The Raman spectra of carbons do not follow the vibration density of states, but consist of three basic features, the G and D peaks around 1600 and 1350 cm-1 and an extra T peak, for UV excitation, at ∼980–1060 cm-1. TheRaman spectra at any wavelength depend on 1) clustering of the sp2 phase, 2)bond length and bond angle disorder, 3) presence of sp2 rings or chains, and 4) the sp2/sp3 ratio. It will be shown how the basic features of the Raman spectra vary by rationalising them within a three-stage model of order of carbons. It is shown how the three-stage model can account for the vast range of experimental data available for Raman experiments at any excitation wavelength. This model can also account for apparently contradictory trends reported in literature, since the clustering of the sp2 phase and the sp3 to sp2 conversion are separately treated.
Electrical Property of Vertically Grown Carbon Nanotube and its Application to the Nanofunctional Devices
Authors: Chu Jaeuk , Jeong Kwangseok , Bae Eunju , Yoo Inkyeong , Choi Wonbong , Kim Jujin 
Published: April 2011

ABSTRACTA highly ordered porous alumina array which hole size is decreased down to 20nm was fabricated by a two step anodization method. Carbon Nanotube was grown vertically with thermal CVD at 600∼700 °C. By using rapid thermal annealing method, low-ohmic contact was formed between multi wall nanotubes and metal electrode and its resistance shows tens to hundreds Ω. The alumina layer which is existed between nanotube and electrode acts as a barrier for conductance. The resistance of carbon nanotube shows the temperature(T-1) dependence at 4.21K < T < 19.9K and semiconducting behavior at this temperature region.