bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of CH4 Plasma Treatment on O2 Plasma Ashed Organosilicate Low-k Dielectrics
Authors: Shi Hualiang , Bao Junjing , liu Junjun , Huang Huai , Ho Paul S. , Goodner Michael D , Moinpour Mansour , Kloster Grant M
Published: April 2011

During an O2 plasma ashing process, carbon depletion and subsequent moisture uptake caused increase of keff and the leakage current in an organosilicate (OSG) low-k dielectric. For dielectric restoration, additional CH4 plasma treatment on the O2 plasma ashed OSG low-k dielectric was investigated using angle resolved x-ray photoelectron spectroscopy (ARXPS), XPS depth profiling, x-ray reflectivity (XRR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and contact angle goniometer. After CH4 plasma treatment on the O2 plasma ashed OSG, the surface carbon concentration and surface hydrophobicity were partially recovered. A dense surface layer containing C=C bonds was found to have formed on the top of the damaged OSG. The C-V hysteresis and the leakage current were reduced as a result of the CH4 plasma treatment. XPS depth profiling revealed that the recovery effect was limited to the surface region.
Organic-and Bio-Based Digital Memory Devices
Authors: Tseng Ricky J. , Ma Liping , Shao Yan , Yang Yang
Published: April 2011

Organic memory devices are considered as a viable approach for future information processing. We demonstrate this type of memory devices evolving from multiple layers structure to solution synthesis hybrid biomolecule structure. By forming a thin organic-nanoparticle layer or virus-nanoparticle layer in the crossbar junction, electronic memory effect based on electrical bistable states with a large on/off ratio, and long retention time is achieved. Temperature dependent data retention shows the nanoparticle formation determines the charge storage activation energy. Such organic, bio-inorganic nanostructures are promising for future memory technology.
Self-aligned TiSi2/Si Hetero-nanocrystal Nonvolatile Memory
Authors: Zhu Yan , Li Bei , Liu Jianlin
Published: April 2011

This work describes a novel nonvolatile memory device with self-aligned TiSi2/Si hetero-nanocrystal charge storage nodes. The TiSi2/Si hetero-nanocrystals can be readily fabricated using industrial standard self-aligned silicidation technique based on Si nanocrystals deposited on ultra-thin tunnel oxide with LPCVD. As compared with a Si nanocrystal memory device, a TiSi2/Si hetero-nanocrystal memory device exhibits faster programming and erasing, and longer retention time.
Memory window in ferroelectric PVDF copolymer gate integrated MOSFET devices for nondestructive readout memory application
Authors: Lim Sang-Hyun , Rastogi Alok C , Desu Seshu B
Published: April 2011

Metal-Ferroelectric-Oxide-Si (MFEOS) field effect transistor (FET) with ferroelectric polyvinylidene fluoride trifluoroethylene copolymer (PVDF-TrFE) gate for nonvolatile memory application is demonstrated. Memory window ascribed to ferroelectric polarization switching has been quantified by shift of threshold voltage are ~ 4-5V. Non saturating IDS is due to free ionic polarization field. IDS-VDS characteristics of functional FET are realized after AC poling.
Nonvolatile Memory Device Based On Nanoparticle Functionalized Tobacco Mosaic Virus
Authors: Tsai Chunglin , Tseng Ricky J. , Yang Yang , Ozkan Cengiz S.
Published: April 2011

Hybrid virus/inorganic nanoscrystals are considered as important building blocks towards new types of functionality for electronic devices. We use tobacco mosaic viruses to assemble platinum nanoparticles and conjugate with quantum dots. By forming a thin hybrid nanocomposite layer in the crossbar junction, we show electronic memory effect based on electrical bistable states with a large on/off ratio, and long retention time. Such hybrid bio-inorganic nanostructures for the first time are promising for future bio-inspired nanoelectronics.
Oxygen Bonding in Bismuth Layered Compounds SrBi2Ta2O9
Authors: Su Dong , Jiang Nan , Wen Jianguo , Liu Jianshe
Published: April 2011

With the help of the high resolution Z-contrast scanning transmission electron microscopy (STEM), the near edge fine structures of the electron loss spectroscopy (EELS) arises from different layers are investigated in SBT. The EELS spectra are interpreted by comparing with the calculation using linearnized augment plane wave (LAPW) method within the local density approximation (LDA). The oxygen bonding nature in different layers are discussed. In Bi2O2 layer, oxygen 2p state interacted with the Bi 6p state leads to a high t2g state in density of state while in SrTa2O7 layer, oxygen 2p state hybridized with Ta 5d and Sr 5d, which leads a higher eg state than t2g state.
Study of the Effect of Metal/Semiconductor Interface Properties on a Resistance Switching Device
Authors: Villafuerte Manuel , Heluani Silvia P. , Juárez Gabriel , Comedi David , Braunstein Gabriel , Golmar Federico
Published: April 2011

N-doped ZnO thin films were deposited by pulsed laser deposition on SiO2/Si substrates. X-ray diffraction analysis revealed that the films had the wurtzite structure, and were highly oriented along the c-axis direction. Au and Al electrical contacts were deposited by sputtering on the top surface of the samples, forming a two-terminal structure in each case. The current-voltage characteristics of the two terminal structure, and the temperature dependence of the resistance switching effect, were studied in the 125-300 K temperature range. The results of these measurements are presented and discussed in terms of the different Schottky barrier heights, as well as in terms of interfacial defect-induced gap states.
Reproducible Resistance Switching in Ni/NiO/Ni Trilayer
Authors: Shima Hisashi , Takano Fumiyoshi , Akinaga Hiro , Inoue Isao H , Takagi Hidenori
Published: April 2011

The resistance random access memory is attracting much attention as a high-density and high-speed non-volatile memory, having large resistance switching ration and good affinity with the conventional CMOS technologies. We demonstrate the resistance switching in the NiO thin film without using Pt electrode.
Adhesion of Crystalline GeSbTe/TiN Interface Characterized by Four Point Bend, Nanoindentation, and Nanoscratch
Authors: Wei guohua , Liu Jun , Fillmore David , Violette Mike , Lu Shifeng
Published: April 2011

Reversible structural phase change phenomenon of certain chalcogenide materials has been investigated extensively in the past decades. Among various phase change chalcogenide materials, Ge2Sb2Te5 (GST) is the most studied material due to its superior optical, electrical and mechanical properties. One of the challenges in using GST is the poor adhesion between crystalline GeSbTe (c-GST) and the substrate, such as TiN. In this work, the adhesion of the c-GST/TiN interface of two samples deposited by different techniques was characterized using four-point bend, nanoindentation and nanoscratch techniques. The nanoindentation and nanoscratch data agree well with the four point bend data. The paper also discusses the application potential of nanoindentation and nanoscratch techniques as qualitative methods for adhesion evaluation in semiconductor process development.
Energy Band States of an Oxygen-doped GeSbTe Phase-change Memory Cell; Mechanism of Low-voltage Operation
Authors: Fujisaki Yoshihisa , Matsuzaki Nozomu , Kurotsuchi Kenzo , Morikawa T , Kinoshita M , Kitai N , Hanzawa Satoru , Moriya H , Takaura Norikatsu , Terao M , Matsuoka M , Koga Tsuyoshi , Moniwa M
Published: April 2011

Phase-change memory is promising because it has a simple structure and has scalability that originates from its unique operating mechanism. However, the programming current should be reduced in accordance with the scaling of cell size [1,2]. We previously reported PCM (Phase Change Memory) cells that operate under 1.5-V/100-μA writing pulses [3, 4]. This PCM had a cell structure composed of 180-nm-W (tungsten) bottom contact to an O-GST (Oxygen-doped GeSbTe) film. Its low-power characteristic is suitable for 0.13-μm generation embedded applications. In the present study, we introduced a new W/O-GST/TaO/W cell structure and found further decrease of programming current the improved stability in the fabrication process. We analyzed the mechanism by which oxygen in GST and the additional TaO layer reduce the power consumption during SET/RESET operations.
Effects of mass, energy and temperature on amorphization in ion implanted Ge2Sb2Te5 thin films
Authors: De Bastiani Riccardo , Piro Alberto Maria , Lombardo Salvatore , Grimaldi Maria Grazia , Rimini Emanuele
Published: April 2011

The paper reports on the amorphization kinetics of chalcogenides ternary alloy induced by Ar or Sb ion irradiation. The reflectivity data, obtained “in situ” during irradiation, allow a description of the amorphization process in terms of a threshold fluence. The results demonstrate that amorphization is caused by the elastic collisions of the projectiles with target nuclei. The influence of the ion mass and energy, of the target temperature in the amorphization is also reported.
In situ SEM Observation of Grain Formation and Growth Induced by Electrical Pulses in Lateral Ge2Sb2Te5 Phase-change Memory
Authors: Yin You , Niida Daisuke , Ohta Kazuhiro , Miyachi Akihira , Asai Masahiro , Higano Naoya , Sone Hayato , Hosaka Sumio
Published: April 2011

A study of electric-pulse-induced crystallization of Ge2Sb2Te5 (GST) was conducted by in situ scanning electron microscopy observation and resistance measurement. A lateral phase-change memory with a top GST channel connected by two separate underlying electrodes was adopted in this study to easily observe the crystallization process. At a low voltage pulse, randomly distributed nuclei were initiated. At the first growth stage, these nuclei grew fast with the pulse amplitude at a rate of around 60 nm/V and then growth rate slowed down to around 14 nm/V when the grain diameter was closed to film thickness. Device resistance during crystallization dropped by around one order of magnitude, which should be due to amorphous to face-centered-cubic transition.
Growth and Characterization of Chalcopyrite Nanocrystals: Beyond Conventional Thin Films
Authors: Fuertes Marrón David , Lehmann Sebastian , Kosk Justyna , Sadewasser Sascha , Lux-Steiner Martha Ch.
Published: April 2011

A dry method for the growth of highly-structured Cu-containing chalcopyrite material on solid substrates, based on the use of metallic precursors, is described. Nanocrystals, sub-micrometer polycrystalline dots, and macroscopic clusters have be grown, either as isolated units or alternatively as embedded structures in a matrix of a binary chalcogenide compound, by adjusting processing parameters. Vapor-liquid-solid (VLS) induced growth has been used for the growth of chalcopyrite nanowires. Examples of material characterization by scanning probe techniques are shown, demonstrating the suitability of the proposed growth method.
Study of CIGS Solar Cells Back Contact
Authors: Marsillac Sylvain , Khatri Himal
Published: April 2011

Molybdenum thin films were deposited by r.f. magnetron sputtering. The strain in the films was mostly tensile and varied, with the Argon pressure and the r.f. power, along a bell curve, reaching a maximum at 8 mTorr (80 W) and 6 mTorr (100 W). The grain size deduced from the X-Ray diffraction measurements (FWHM) decreased with increasing Argon pressure and, to a lower extent, with decreasing r.f power. The change in grain size, as well as in morphology, was confirmed by AFM imaging. Finally, the resistivity of the films was found to increase with increasing Argon pressure, while the films maintained good adhesion to the soda-lime glass substrates for all Argon pressures and r.f. power.
Comparative Studies of the Structure and Microstructure of Zn2x(CuBIII)1-xX2 Semiconductors (BIII=Ga,In; X=S,Se,Te)
Authors: Schorr Susan , Wagner Gerald , Tovar Michael , Sheptyakov Denis
Published: April 2011

Powder samples of (ZnX)2x(CuBX2)1-x mixed crystals (B=Ga,In; X=S,Se,Te) were prepared by solid state reaction of the elements and annealed with cooling rates between 2 - 42 K/h in the entire composition range. Structural parameters (e. g. lattice parameter, tetragonal deformation η) were investigated by X-ray and neutron diffraction studies. The microstructure was studied by transmission electron microscopy (TEM) and HRTEM. The chemical composition was determined by EDX analysis on the transmission electron microscope.

The chemical disorder process in the 2(ZnX)x(CuBX2)1-x solid solution series leads to a phase separation, i. e. in a certain composition range (2-phase field) two phases, tetragonal domains and a cubic matrix, coexist. Its width depends on the three-valent cation only and is independent from the size of anion. The habit of the tetragonal domains is like a flat discus, its short extension lies always parallel to their tetragonal c-axis. They are simultaneously arranged on the (100),(010) and (001) planes within the cubic matrix. After nucleation of the domains, their growth obeys t1/2, i.e. it is controlled by diffusion. In the sulfides and selenides systems with In as three-valent cation the tetragonal domains are 'infected' by stannite type (or CuAuI type) cation ordering independently of their orientation, whereas in the tellurides system CuPt type cation ordering was obtained. The tetragonal (ZnX)2x(CuGaX2)1-x mixed crystals exhibit only chalcopyrite type structure and orientation domains without another type of cation ordering.

In the single phase regions the lattice parameter follows Vegrads rule, whereas in the 2-phase field the both phases try to match in the a-b-plane (atetr∼acub), causing an increase of the tetragonal lattice parameter c and herewith a strong increase of the tetragonal deformation η.
Quantum Efficiency Measurements to Deduce Non-Ideal Solar-Cell Features
Authors: Nagle Timothy J. , Davies Alan R. , Sites James R.
Published: April 2011

Appropriate interpretation of quantum-efficiency (QE) measurements made on non-ideal solar cells often reveal subtle features of the photodiodes. QE measurements on CIGS and CdTe thin-film solar cells with CdS buffer layers demonstrate some of these features, and in each case we identify the electrical processes responsible. One well-known complication in cells with CdS buffer layers is “photodoping”, where blue light exposure increases the n-type CdS carrier density. The resulting modification of the p-n junction alters the carrier collection for all wavelengths and can lead to misinterpretation of results. The use of a white, DC-bias light during QE measurements generally solves this problem, but it has not been clear what bias light level is sufficient for accurate results. Measurements with varying intensities of DC-bias light show that complications due to CdS photoconductivity are generally mitigated near 0.05 sun intensity. Other factors which can cause misinterpretation of QE measurements include the presence of secondary barriers, and photoconductivity in the absorber layer. Numerical simulations of band profiles under various light-bias conditions are consistent with the experimental data. The analysis is used to suggest a standard set of measurement conditions for reliable QE analysis.
Electron-Backscatter Diffraction of Photovoltaic Thin Films
Authors: Moutinho Helio , Dhere Ramesh , Jiang Chun-Sheng , To Bobby , Al-Jassim Mowafak
Published: April 2011

In electron-backscatter diffraction, crystalline orientation maps are formed while the electron beam of an SEM scans the sample surface. EBSD requires a flat sample to avoid shadowing of the electrons from the detector by surface features. In this work, we investigate the preparation of CdTe samples deposited by close-spaced sublimation for EBSD analysis. Untreated samples were rough, resulting in areas with no EBSD signal. We processed the samples by polishing and ion-beam milling. Polishing produced flat samples, but low-quality EBDS data, because the top surface of the samples had poor crystallinity. In contrast, ion-beam milling proved to be suitable for producing flat samples with minimal surface damage, yielding good EBSD data. We also analyzed the samples with atomic force microscopy, and correlated the quality of the EBSD data with sample roughness. The EBSD data showed that the CdTe films were randomly oriented and had columnar growth and a high density of <111> twin boundaries.
Kinetics of Charge Trapping and Emission in CIGS Solar Cells
Authors: Urbaniak Aleksander , Igalson Malgorzata , Siebentritt Susanne
Published: April 2011

In this work we investigate bias - induced metastability in CIGS solar cells. Long - term capacitance transients have been measured for two baseline CIGS devices with different efficiencies and a CGS cell in order to analyze carrier trapping processes. Based on the results we discuss hole emission process which leads to metastable increase of net acceptor density and also hole capture related to its relaxation. Time constants and activation energies for hole emission and capture have been obtained. Apart of carrier trapping processes we have also distinguished an interface-related change of capacitance. Our results indicate processes involving thermal lattice relaxation. We explain them in light of properties of (VSe+VCu) divacancy, defect with negative correlation energy, which can exist in both donor and acceptor configuration.
The Technology That Began Steuben Glass
Authors: Favela Jacob Israel , Vandiver Pamela
Published: April 2011

Frederick Carder popularized art glass in America and is remembered as the founder of Steuben Glass. He was a designer and glass technologist whose factory produced colored and highly decorated glass vessels that competed with but were less expensive than those of Tiffany Studios. To understand the differences in technology between the competing products of Carder and Tiffany, opalescent white glass formulations, fumed gold lusters and silver-containing glasses used in trailed decoration were analyzed and compared by electron beam microprobe analysis and scanning-electron microscopy with simultaneous energy dispersive x-ray analysis. Analytical results show standardized processing that includes opalescent compositions in a narrow range of soda-lime-silicate and lead-alkali-silicate glasses, fumed “golden” lusters made from tin and silver, and iridized surface layers formed by multiple heat treatments.
Growth Promotion and Etching of Carbon Nanotubes by Carbon Dioxide in Chemical Vapor Deposition using Methane Gas
Authors: Suda Yoshiyuki , Takayama Junichi , Saito Takeshi , Okita Atsushi , Nakamura Junji , Sakai Yosuke , Sugawara Hirotake
Published: April 2011

We report the effect of CO2 addition to CO4 gas on carbon nanotube (CNT) growth by chemical vapor deposition. CO2 gas was introduced during the growth of CNTs on Fe0.05Mo0.025MgO0.925 and Ni0.05Mo0.025MgO0.925 catalysts by CO4 gas at a temperature of 800–850°C, and its concentration in a fraction of the gas flow rate was varied from 5×10−3 to 50%. In the experimental condition of the preferential growth of multi-walled CNTs, the carbon yield and the G/D ratio in the Raman spectra of the CNTs grown in 10%-CO2/CO4 were slightly higher than that grown in CO4 only. However, CNTs hardly grew when the CO2 concentration was more than 10%. We then prepared CO2 gas diluted with Ar gas (CO2/Ar) and varied its flow rate between 0 and 10 sccm. As the CO2/Ar gas flow rate was increased, the number of RBM peaks decreased even though the G/D ratio gradually decreased. The decrease in the RBM intensities of CNTs on the FeMoMgO catalyst was more significant than that of NiMoMgO.
Carbon Nanotube Growth on Different Types of Tool Steel Substrates
Authors: Nasuf Gulfem Ipek , Yen Max
Published: April 2011

This paper investigates the effectiveness of different pretreatment methods applied on M50, M35, and W4 type of tool steel substrates for direct growth of carbon nanotubes. The pretreatments explored include treatment with sand paper polishing, nitric acid (HNO3) etching, and high temperature hydrogen gas treatment. Furthermore, in order to establish a correlation between the steel surface average roughness value and the carbon nanotube growth, surface topography of steel substrates created by mechanical polishing were measured before actual growth process. Grown carbon nanostructures were shown by SEM and TEM to be multi-walled carbon nanotubes (MWCNTs) and vapor grown carbon nanofibers (VGCFs). It was found that under the same pretreatment conditions, even when the same roughness values were achieved and the same thermal chemical vapor deposition conditions were applied, grown nanostructures on different types of tool steel substrates showed dissimilarity.
Gas Phase Electronic Sensing Using Single Wall Carbon Nanotube/Boipolymer Hybrids
Authors: Khamis Samuel M , Chen Michelle , Johnson A.T. Charlie
Published: April 2011

We report on a class of hybrid sensors involving single-walled carbon nanotube field effect transistors (SWNT FET's) functionalized with various oligonucleotides. These oligonucleotides include ten sequences of single stranded DNA and two sequences of single stranded. We show that the sequence of the adsorbed oligonucleotide is the key component in determining the response that the hybrid will experience upon exposure to a panel of five volatile organic compounds (VOC's). Our sensors present a change in conductance, which is specific to the analyte being tested, and the adsorbed species. Our devices respond and recover quickly (seconds), and are reproducible over ∼100 cycles. These traits are highly desirable for the creation of a technology for use as an electronic nose. We present a database of responses involving hundreds of devices.
Nanotubules from a Self-Assembling Small Molecule
Authors: Johnson Ross S. , Moralez Jesus G. , Fenniri Hicham
Published: April 2011

Control over the dimensions of nanostructured materials is of critical importance for proper utilization in devices. There has been a number of systems reported that utilize amphiphilic molecules that organize themselves into nanotubes or tubules, as well as various polymers that can assemble into tubular nanoscale structures. The organization of these components into nanotubes is mainly driven by hydrophobic effects of the substituents in particular solvents, which contain polar and apolar portions. While studying a modification to a previously reported GC module that normally forms rosette nanotubes (RNTs) with diameters in the 4nm range, we discovered that a small modification led to the formation of nanotubes with diameters 10 times of that expected. These structures were studied by SEM, TEM, and AFM in an attempt to uncover the mechanism of their formation. It was determined that these chiral organic molecules first self-assemble into sheet-like structures, but due to an inherent curvature of the sheet, they roll into large nanotubules. This new type of self-assembled nanotube may have applications in host-guest chemistry and as templates for other nanoparticles and materials.
Epitaxial Growth of III-V Nanowires on Group IV Substrates
Authors: Bakkers Erik , Borgstrom Magnus , Verheijen Marcel
Published: April 2011

Semiconducting nanowires are emerging as a route to combine heavily mismatched materials. The high level of control on wire dimensions and chemical composition makes them promising materials to be integrated in future silicon technologies as well as to be the active element in optoelectronic devices.

In this article, we review the recent progress in epitaxial growth of nanowires on non-corresponding substrates. We highlight the advantage of using small dimensions to facilitate accommodation of the lattice strain at the surface of the structures. More specifically, we will focus on the growth of III–V nanowires on group IV substrates. This approach enables the integration of high-performance III–V semiconductors monolithically into mature silicon technology, since fundamental issues of III–V integration on Si such as lattice and thermal expansion mismatch can be overcome. Moreover, as there will only be one nucleation site per crystallite, the system will not suffer from antiphase boundaries.

Issues that affect the electronic properties of the heterojunction, such as the crystallographic quality and diffusion of elements across the heterointerface will be discussed. Finally, we address potential applications of vertical III–V nanowires grown on silicon.
InGaN Growth with Indium Content Controlled by GaN Growth Plane
Authors: Kanie Hisashi , Akashi Kenichi
Published: April 2011

Highly spatially resolved cathodoluminescence (HRCL) imaging and electron backscattering pattern (EBSP) study of InGaN microcrystals were achieved. InGaN grown by the nitridation of a mixture of GaN microcrystals and indium sulfide powders with ammonia at 1000°C had crystal habit with twelve prismatic planes. The prismatic planes were grouped into two groups: the first group is pentagonal shaped planes yielding blue CL (420nm) and rectangular planes without luminescence. EBSP showed that the pentagonal shaped planes are indexed to the {11-20} a-plane and the rectangular plane to the {1-100} m-plane. HRCL imaging showed InGaN accumulated at the V pits on the basal plane. The obevation indicated that the crystal qualty of InGaN and the indium contents incorpated were controlled by the indices of GaN growth planes on which InGaN grew.
Substantial Reduction of Reset Current in CoO RRAM with Ta Bottom Electrode
Authors: Shima Hisashi , Takano Fumiyoshi , Tamai Yukio , Muramatsu Hidenobu , Akinaga Hiroyuki , Inoue Isao H , Takagi Hidenori
Published: April 2011

The resistance switching in Pt/Co-O/Pt and Ta/Co-O/Pt has been investigated. Compared to Pt/Co-O/Pt, the reset current was more efficiently decreased in Ta/Co-O/Pt by using the load resistor in the forming process, indicating that the embedded resistance component with little parasitic capacitance effectively limits the current in the forming process. The reset process with the reset current lower than 0.15 mA was successfully demonstrated in Ta/Co-O/Pt. In addition, the high speed resistance switching by the voltage pulse with the pulse width of 20 ns was carried out, by investigating the pulse voltage height dependence of reset speed in Ta/Co-O/Pt.
From Micro to Nanometric Grain Size CVD Diamond Tools
Authors: Almeida Flávia A. , Amaral Margarida , Salgueiredo Ermelinda , Fernandes António J.S. , Costa Florinda M. , Oliveira Filipe J. , Silva Rui F.
Published: April 2011

CVD diamond coated tools are developed for applications as different as turning of cemented carbides and bone drilling. The diamond films are deposited by Hot Filament Chemical Vapor Deposition (HFCVD), with grain sizes varying from conventional micrometric (12 μm) to nanometric (< 100 nm) and film thickness up to 50 μm. Silicon nitride (Si3N4) ceramics are chosen for the base material in order to guarantee maximal adhesion. Both the micrometric and nanometric CVD diamond grades endure the cemented carbide turning showing slight cratering, having flank wear as the main wear mode. However, nanocrystalline diamond present the best behavior regarding cutting forces (<150 N) and tool wear (KM=30 μm, KT=2 μm and VB=110 μm) and workpiece surface finishing (Ra=0.2 μm). In the case of the dental drilling experiments, a polymeric laminated test block is used to simulate the human mandible and maxilla. The temperature rise during drilling is monitored to prevent overheating above 42–47 °C that is known to cause tissue death and implant failure. It is possible to drill with a CVD diamond Si3N4 coated tool with significantly lower forces (fourfold smaller), lower rise in temperature (4°C less), lower spindle speeds (100 rpm) and higher infeed rates (30 mm/min), when compared to the commercial steel (AISI 420) drill bits.
Trace Analysis of Nanoscale Materials by Analytical Electron Microscopy
Authors: Newbury Dale E. , Leapman Richard D.
Published: April 2011

Trace analysis of nanometer-scale objects can be performed with parallel-detection electron energy loss spectrometry in the analytical electron microscope. Spectra are collected in the second difference mode with the beam current chosen to maximize the spectral count rate. Numerous elements can be detected at trace levels below 100 parts per million atomic, including transition metal, alkali metal, alkaline earth, and rare earth elements, provided they have a “white line” resonance structure at the ionization edge. Trace nanoanalysis by AEM/PEELS permits direct examination of the microscopic distribution of trace constituents.
Selective Imaging of Metal Atoms in the Semiconducting Layered Compound MoS2 by STM/STS
Authors: Inoue S. , Kawami H. , Yoshimura M. , Yao T.
Published: April 2011

We have investigated the valence band structure of MoS2, a transition-metal dichalcogenide, using scannino tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) for the first time. We have found characteristic peaks in the (dl/dV)/(I/V)-V characteristic at −1.0 and −1.4V below the fermi level, which correspond to the S Pz state and Mo dz2 state, respectively. Mo atoms are accessible only at the sampfe voltage of −1.4V in the range of −1.0 through − 1.5V, due to the strong localization of the Mo dz2 state with very small bandwidth.
Relationships Between Photoluminescence Spectra and Porosity of Porous Silicon
Authors: Song H.Z. , Zhang L.Z. , Zhang B.R. , Qin G.G.
Published: April 2011

It was found that porous silicon (PS) layers formed on 0.01 Ωcm (111) and 0.02 Ωcm (100) Si substrates show high photoluminescence (PL) peak energies on both lower and higher porosity sides and a minimum of PL peak energy at the moderate porosity, while those formed on 0.8 and 10Ωcm (111) p-type Si substrates show an increase of PL peak energy with porosity on the lower side and a saturation of PL peak energy with porosity on the higher side. These experimental facts are not consistent with the quantum confinement model for light emission of PS, which predicts a monotonous increase of PL peak energy with PS porosity.
Grazing Incidence X-Ray Reflectance Measurement of Surface and Interface Roughness on the Sub-Nanometre Scale
Authors: Wormington M. , Sakurai K. , Bowen D.K. , Tanner B.K.
Published: April 2011

Grazing incidence X-ray reflectivity may be used to measure surface topography including roughness and correlation lengths to sub-nanometre precision. A study is made of a technically important surface, a carefully-polished specimen of Zerodur glass-ceramic, which has been measured by diffuse scatter of CuKα X-radiation and atomic-force profilometry methods. The data have been analysed in terms of a fractal representation of the surface correlation function. Results from the two methods agreed within their estimated errors, with the X-ray data showing roughnesses of 1.3 nm, correlation length of 1 μm and fractal parameter (bandwidth) of 0.35. The X-ray methods have a lower cut-off length, are much more rapid for averaged information and are both non-contacting and non-destructive. They also show potential for the study of interface roughness in thin films.
Molecular Dynamics Simulation of the Elastic Deformation of Nanometer Diameter Metal Clusters
Authors: Paithankar Dilip Y. , Talbot Julian , Andres Ronald P.
Published: April 2011

Indentation using the AFM is a powerful method for determining elastic properties of small supported clusters. However, a theoretical framework has yet to be developed to interpret such measurements. The elastic deformation of nanometer sized gold clusters are modeled using the Embedded Atom Method (EAM) potential of Foiles et al. [1]. Force versus deformation curves are obtained for a series of truncated octahedral clusters having FCC symmetry (N=38, 201, 586, 1289, 2406). It is found that the MD results both for static compression and for harmonic vibration can be analytically estimated by using an elastic constant for the clusters analogous to the elastic modulus of a bulk material. However MD predictions for static compression are not in agreement with the deformation results of Schaefer et al. [2].
Effects of Residual Stress on the Measurement of Hardness and Elastic Modulus using Nanoindentation
Authors: Pharr G.M. , Tsui T.Y. , Bolshakov A. , Oliver W.C.
Published: April 2011

The effects of stress on the measurement of hardness and elastic modulus in aluminum alloy 8009 have been studied experimentally and by finite element simulation. The experiments were performed by making a linear array of nanoindentations on the side of a stressed bend bar, sampling regions of high uniaxial tension, high uniaxial compression, and a variety of stresses in between. When analyzed according to standard methods, the nanoindentation data reveal a decrease in both hardness and modulus with increasing stress from compression to tension. While the decrease in hardness is consistent with previous observations made in conventional hardness testing, the modulus decrease was unexpected. Finite element simulation revealed that the drops in hardness and modulus are not real, but occur because the procedure for determining contact area from the nanoindentation load-displacement data does not account for pileup around the indentation. The finite element simulation shows that large compressive stresses promote pileup while tensile stresses reduce it, and this must be properly accounted for if accurate hardnesses and moduli are to be obtained. Experimental results are presented which further support this point of view.
Modeling Electromigration-Induced Stress Buildup Due to Nonuniform Temperature
Authors: Clement J. J. , Thompson C. V. , Enver A.
Published: April 2011

Atomic transport due to electromigration in interconnect lines in integrated circuits depends strongly on temperature. Therefore temperature nonuniformities can create sites of atomic flux divergence resulting in material accumulation or depletion leading to failure. The mechanical stress which will evolve at the sites of material flux divergence will oppose the electromigration driving force. A model is developed to describe the stress evolution during electromigration in the presence of temperature nonuniformnities. Solutions of the differential equations describing the electromigration-induced stress buildup are calculated numerically. The solutions are compared to experimental data in the literature.
Anisotropy in Thermal, Electrical and Mechanical Properties of Spin-Coated Polymer Dielectrics
Authors: Bidstrup Sue Ann , Hodge Thomas C. , Lin Linda , Kohl Paul A. , Lee J.B. , Allen Mark G.
Published: April 2011

In MCM-D applications, interlayer dielectrics separate and insulate metal conductors to form a three-dimensional interconnection structure. Due to the three-dimensional nature of these structures, the thermal, electrical and mechanical properties of the dielectricmaterials must be known for all orientations in order to correctly design and simulate devices. The most commonly used polymer in microelectronics, polyimide, exists in formulations which have been shown to have a high degree of orientation and exhibit anisotropicproperties.
Defect Analysis In Substrate Materials for High Tc Superconducting Thin Films
Authors: Fletcher P. R. , Leach C. , Wellhofer F. , Woodall P.
Published: April 2011

Many defects in high Tc superconducting films propagate from the substrate through to the film surface, disturbing the epitaxy at the interface and adversely affecting the physical properties of the film, particularly Jc. In this study the surface of Magnesium Oxide (100) single crystal substrates with different preparative treatments have been investigated using optical cathodoluminescence microscopy (CL), with a view to establishing its effect on the deposition of thin films of YBa2Cu3O7-δ superconductors.

CL excitations due to mechanically and chemically induced defects in the MgO substrate crystals are observed by optical CL microscopy. Several pre-deposition treatments have been compared in this way to determine the best preparation route for the substrates. Jc measurements indicate that the substrate surface quality is an important parameter in the production of high quality thin films especially for the fabrication of devices.

It is concluded that CL provides a powerful and rapid tool for MgO quality assessment before thin film deposition.
Epitaxial Thin Films And Heterostrcutures of Various Isotropic Metallic Oxides for Device Applications
Authors: Eom C. B. , Phillips Julia M. , Cava R. J.
Published: April 2011

We have grown epitaxial thin films of various isotropic metallic oxides such as Sr1-xCaxRuO3 and La8-xSrxCu8O2Oin situ by 90° off-axis sputtering. These metallic oxides are pseudo-cubic perovskites with essentially isotropic properties, which could be ideal normal metals for SNS junctions in superconducting devices and for electrodes in ferroelectric devices. We have fabricated epitaxial ferroelectric heterostructures [SrRuO3/Pb(Zr0. 52 Ti0.4 8) O3 /SrRuO3] employing isotropic metallic oxide (SrRuO3) electrodes on substrates of (100) SrTiO3 and (100) Si with an yttria stabilized zirconia buffer layer. They exhibit superior fatigue characteristics over those made with metal electrodes, showing little degradation over 10 cycles, with a large remnant polarization (27 μC/cm2 ). We have also grown epitaxial superconducting heterostructures (YBa2Cu3O7 / La8-xSrxCu8O2O / YBa2Cu3O7 ) with a copper-oxide-based isotropic metallic oxide (La8-xSrxCu8O20) normal metal barrier. X-ray diffraction and cross-sectional transmission electron microscopy reveal these heterostructures to have high crystalline quality and clean interfaces. This material will facilitate fabrication of ideal SNS Josephson junctions with low boundary resistance due to its excellent chemical compatibility and lattice match with cuprate superconductors and will be useful for determining the source of interface resistance in such heterostructures.
Epitaxial Growth of CoO (001) and Co3O4 (001) Films on MgO (001) by Pulsed Laser Deposition
Authors: Feeler David , Williams R. Stanley
Published: April 2011

Single crystal films of both rocksalt CoO and spinel Co3O4 were epitaxially grown with (001) orientations on MgO(001) substrates by pulsed laser deposition from CoO targets. The samples were characterized with low energy electron diffraction to determine the parallel orientation of the films with respect to the substrate, and x-ray diffraction to determine the perpendicular structure of the films. Both films were determined to have undergone tetragonal distortions, although to different degrees, due to the biaxial stress present in these epitaxial films.
Growth and Characterization of Epitaxial PbTiO3Thin Films On Mgo
Authors: Zhang K. , Pashmakov B. , Mogilevsky R. , Jaeger H. M. , Xu Ming , Kramer M. J. , Goldman A.
Published: April 2011

Epitaxial PbTiO3 thin films have been grown on single-crystal MgO (100) substrates using metalorganic chemical vapor deposition technique. The energy gap was determined from optical absorption data to be Eg= 3,425 eV. Secondary ion mass spectrometry data showed uniform distribution of Pb, Ti and O atoms with no traces of carbon contamination. Atomic force microscopy studies showed different surface morphology for different film growth rates. In-situ X-ray diffraction data indicate that the tetragonal-to-cubic structural phase transition occurs at about 500–520°C. Above 750 °C the films exhibit multi-phase character, the textured PbTiO3 phase co-existing with a polycrystalline Pb2Ti2O6 structure and a possible Mg-containing impurity phase.
Properties of Yttrium Oxide Thin Films on Silicon (100) Prepared by Evaporation of Yttrium in Atomic Oxygen
Authors: Hudner J. , Ohlsén H. , Fredriksson E.
Published: April 2011

Thin layers of Y2O3 have been prepared on silicon (100) by an activated reactive evaporation process involving evaporation of metal Y in an atomic oxygen plasma. The presence of the oxygen plasma was found to be crucial for the formation of homogeneous Y2O3 films on Si. The formation of Y2O3 films on Si (100) at different substrate temperatures was investigated. X-ray diffraction analysis showed that Y2O3 films formed between 300 °C and 650 °C were (111) textured while Y2O3 prepared at lower substrate temperatures (80 °C) exhibited mixed orientations. Rutherford backscattering spectrometry indicated that films were stoichiometric. No pronounced channeling was observed in films grown at 350 °C, suggesting polycrystalline film structures. Atomic force microscopy revealed very smooth surface morphologies with average surface roughness < 20 Å for films 700 Å thick deposited at 350 °C. Secondary ion mass spectroscopy indicated the abundance of intermediate layers in the film-substrate interface.
Rapid Thermal Oxidation of Lightly Doped Silicon in N2O
Authors: Sun S.C. , Wang L.S. , Yeh F.L. , Lai T.S. , Lin Y.H.
Published: April 2011

In this paper, a detailed study is presented for the growth kinetics of rapid thermal oxidation of lightly-doped silicon in N2O and O2 on (100), (110), and (111) oriented substrates. It was found that (110)-oriented Si has the highest growth rate in both N2O and dry O2, and (100) Si has the lowest rate. There is no “crossover” on the growth rate of rapid thermal N2O oxidation between (110) Si and (111) Si as compared to oxides grown in furnace N2O. Pressure dependence of rapid thermal N2O oxidation is reported for the first time. MOS capacitor results show that the low-pressure (40 Torr) N2O-grown oxides have much less interface state generation and charge trapping under constant current stress as compared to oxides grown in either 760 Torr N2O or O2 ambient.
Ultrathin Gate Dielectric Growth at Reduced Pressure
Authors: McIntosh Robert , Galewski Carl , Grant John
Published: April 2011

The Growth of ultrathin oxides in N2O ambient has been a subject of extensive research for submicron CMOS technology. Oxides grown in N2O tend to have a higher charge-to-breakdown, less charge trapping under constant current stress, and less interface state generation under current stress and radiation than conventional oxides grown in oxygen [1,2]. In addition the penetration of boron through N2O oxides is significantly less than through conventional thermal oxides [3]. The improved characteristics of N2O are due to an interfacial pileup of nitrogen atoms [1-3]. Thus the growth of thermal oxides in N2O provides a method for obtaining many of the more favorable aspects of reoxidized-nitrided silicon dioxides, with a much simpler process.
Nanocrystalline Doped Cerium Oxide as a Catalyst for SO2 Reduction by Co
Authors: Tschöpe Andreas , Ying J. Y. , Liu W. , Flytzani-Stephanopoulos M.
Published: April 2011

Nanocrystalline processing by inert gas condensation has the inherent advantages of generating: (1) high surface area nanoclusters, (2) non-stoichiometric oxides, and (3) high dispersions of dopants. This approach is exploited in the synthesis of fluorite-structured catalysts for SO2 reduction by CO. Nanocrystalline CeO2-x, La-doped CeO2-x, and Cu-doped CeO2-x were produced by magnetron sputtering from a pure or mixed metal target, followed by controlled oxidation of the metallic clusters. The as-prepared doped and undoped nanocrystalline CeO2-x materials were found to be excellent catalysts for complete SO2 conversion to elemental sulfur. Undoped nanocrystalline CeO2-x enabled light-off at 460 °C, a temperature ∼120 °C lower than that over polycrystalline CeO2, which is a novel effective catalyst itself. The high catalytic activity of the nanocrystals was associated with their high concentration of oxygen vacancies. Excellent poisoning resistance was also exhibited by the nanocrystalline CeO2-x samples. These materials have stable activity in the presence of excess CO2.
Microstructural Studies of the WO3/TiO2 Monolayer Catalyst System Using High Resolution Electron Microscopy
Authors: Burrows A. , Kiely C. J. , Joyner R. W. , Knözinger H. , Lange F.
Published: April 2011

We have characterised the WO3T'iO2 (anatase) catalyst system using High Resolution Electron Microscopy. We will show that the overlayer preserves the surface roughness of titania and consists of 2D-hexagonal clusters that have a definite orientation relationship with the support. The contrast observed from these clusters is discussed in terms of existing structural models. A comparison between traditional chemical methods of preparation and simple mechanical mixing is made to assess the effectiveness of the latter to disperse WO3.
The Catalytic Reduction of Nitrogen Oxide Over the Catalysts Supported on Activated Carbon Fibers
Authors: Lu Yun , Fu Ruowen , Chen Yishan , Zeng Hanmin
Published: April 2011

Copper-series, nickel-series, and copper-cobalt composite-series catalysts supported on activated carbon fiber were prepared in this paper. Their structures and catalytic activities for the reduction of nitric oxide with ammonia were investigated simultaneously.
Sol-Gel Synthesis of Hybrid Organic-Inorganic Tin Oxide Based
Materials
Authors: Ribot Francois O. , Banse F. , Sanchez C.
Published: April 2011

RSn(OAmt)3 with R = n-butyl, n-butenyl or para-styryl, which are
monomeric precursors, have been hydrolyzed. The so-obtained products have
been characterized mainly by 119Sn NMR. In every cases, tin
expands its coordination from 4 to 5 and 6, and hydrolysis yields tin
oxo-hydroxo species of small size. For n-butyl and n-butenyl, a cage-like
tin oxo-hydroxo cluster,
{(RSn)12(μ3–O)14(μ2-OH)6}2+,
was evidenced as the major compound formed. Organic polymerization of the
unsaturated organic groups linked to tin was initiated on the hydrolysis
products and yielded hybrid systems which can be pictured as tin oxo-hydroxo
oligomers attached together by polymeric chains.
Titanate Ceramics from Wet-Chemically Prepared
Powders
Authors: Lin C.H. , Yan T.S.
Published: April 2011

A simple method of producing very fine, homogeneous
BaxSr1-xTiO3 powders was
developed in this study by wet-chemically reacting
Ti(0H)4-xH2O, Ba(OH)2, and
Sr(OH)2 as raw materials under 100°C. Relationships were
obtained between particle size, composition, and reaction temperatures,
reaction tunes, Sr/Ba ratios, and (Ba+Sr)/Ti ratios of the solution.

Experimental results indicated that the particle size, which was around 40
nm, was both proportional to the reaction temperature as well as independant
of the reaction time. In light of the varying reactivities of Ba and Sr
towards Ti, reaction time was found to be a primary factor which controls
the precise Ba/Sr ratio and (Ba+Sr)/Ti ratio of the titanate powder. A
suitable reaction condition was observed to have prevented by-products
Ba6Ti17O40 or
Ba2Ti04 from being formed.

The titanate powders were compressed and sintered for various temperatures.
The compressibility and the sinterability of the powders were obtained. The
microstrucure, dielectric constant and dissipation factor of the titanate
ceramics ware observed and measured. These values sufficiently correlated
with those of the titanate ceramics produced from the powders by the
solid-state sintering method.
Hydroxyapatite Ceramics from Hydrothermally Prepared
Powders
Authors: Lin C.H. , Huang C.W. , Chang S.C.
Published: April 2011

Hydroxyapatite (Ca5(P04)3(0H)) is an
effective material for artificial human bone production. Hydroxyapatite
powders were hydrothermally produced in this work by reacting
Ca(OH)2 with Na3PO4·12H2O in
an autoclave at various temperature and for various times. The particle size
of hydroxyapatite was observed to be very fine, uniform, around 50 nm, as
well as independent of reaction time.

The hydroxyapatite powders were compacted and sintered at various
temperatures for 2 hrs. The density, grain size, and hardness of the
hydroxyapatite ceramics were measured and compared with those of the
hydroxyapatite ceramics produced by the powders from the commercial source.
The hydroxyapatite ceramics from the hydrothermal powders were found to have
a higher density, smaller grain size, and higher hardness.

After the hydroxyapatite ceramics were dipped in a simulated biological body
liquid for 10 days, the density and hardness of the hydrooxyapatite ceramics
from the hydrothermal powders were less deteriorated than those of the
hydroxyapatite ceramics from the commercial powder.