bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Gold Thin Films Evaporated on Polyethylene Naphthalate Films toward the Fabrication of Quantum Cross Devices
Authors: Kaiju Hideo , Ono Akito , Kawaguchi Nobuyoshi , Kondo Kenji , Ishibashi Akira
Published: April 2011

Molecular electronics devices continue to be pursued as a technology that offers the prospect of scaling device dimensions down to a few nanometers and also promote a practical introduction for high-density memory applications. One of several molecular devices is a cross-bar memory device fabricated by nanoimprint lithography process, which has achieved the production of 30-nm half-pitch patterning. However, today's production procedures such as nanoimprint lithography, optical lithography, and electron-beam lithography, do not allow for the resolution to achieve sub-10-nm line-width structures. Recently we have proposed a double nano-“baumkuchen” (DNB) structure, composed of two thin slices of alternating metal/insulator nano-“baumkuchen” as a lithography-free nano-structure fabrication technology. The DNB has potential application in a high-density memory device, the cross point of which can scale down to ultimately a few nanometers feature sizes because the pattering resolution is determined by the metal-deposition rate, ranging from 0.01 nm/s to the order of 0.1 nm/s. One element of the DNB structure is called a quantum cross (QC) device that consists of two metal nano-ribbons having edge-to-edge configuration. In the area of edge-to-edge QC devices there has been no experimental reports, meanwhile face-to-face devices such as cross-bar devices and spin tunneling devices, have been widely studied both theoretically and experimentally. In our present work, as the first experimental attempt toward the fabrication of QC devices, we have studied gold thin films evaporated on polyethylene naphtalate (PEN) organic films, which can be a candidate of metal/insulator part used for QC devices, by using the atomic force microscope (AFM). Au thin films were thermally evaporated on PEN films in the high vacuum chamber including the film-rolled-up system. The Au thickness was measured by a mechanical method using the stylus surface profiler and an optical method using the diode pumped solid state (DPSS) green laser. Surface morphologies of Au thin films on PEN films were analyzed by the AFM at room temperature. As the thickness of Au films evaporated on PEN films decreases from 20 nm to 5 nm, the AFM surface roughness is reduced from 4.8 nm down to 1.5 nm in the scanning area of 500~500 nm2. The Au grain size is 28.0-4.6 nm for 5-nm-thick Au films and 45.8-5.8 nm for 10-nm-thick Au films, respectively. As a result of the scaling investigation of the surface roughness, the surface roughness of 5-nm-thick Au films is 0.22 nm, corresponding to one atomic size, in the scanning scale of 5 nm. These experimental results indicate that Au thin films on PEN films are suitable as a candidate of metal/insulator(organic films) hybrid materials used for QC devices, and may open up a noble research field to clarify the electric characterization of QC devices using a few atoms or molecules leading to high-density memories.
Mechanical Evaluation of Thermal Transitions in Polymer Nanofibres Using SPM
Authors: Wang Wei , Li Shuangwu , Barber Asa H.
Published: April 2011

Polymer nanofibres produced by electrospinning techniques have unique mechanical properties due to their large surface area to volume ratio and potentially high molecular orientation. The effects of temperature on mechanical properties is challenging to measure due to the small fibre diameters produced. In this paper, scanning probe microscopy (SPM) is successfully used to elucidate the mechanical performance of individual electrospun polyvinyl alcohol (PVA) nanofibres over a range of temperatures. As observed in the results, thermal transitions have a dramatic effect on the mechanical behaviour of the nanofibres and are highlighted using SPM techniques analogous to dynamic mechanical thermal analysis but at the nanoscale. Interestingly, nanofibre thermal transitions are shown to be mediated by fibre diameter and the driving force of reducing the surface area of the nanofibre.
Nanoscale Analysis of Defects in Semiconductors and Dielectrics by Means of Charge-transient Spectroscopy/microscopy
Authors: Lányi Štefan , Nádaždy Vojtech , Hruškovic Miloslav , Hribik Ján
Published: April 2011

We discuss the possibilities of analysis of electrically active defects in semiconductors and dielectrics by means of Isothermal Capacitance-Transient Spectroscopy and Isothermal Charge-Transient Spectroscopy, applied on sub-micrometer scale. While the first of them utilizes the relaxation of the depletion layer, caused by emission of trapped charges and requires sufficient conductivity, the second directly integrates the transient current and can be applied also to low-conductivity materials like dielectrics.

We present some results obtained on pentacene thin films. By means of our charge-transient spectrometer we have achieved a resolution of hundreds of electrons but we believe it can be further improved approximately by one order of magnitude. In materials with relatively high defect concentration, using optimal shape of the probe, a resolution on the order of tens of manometers can be achieved. At low defect concentrations, e.g. in device quality silicon, a resolution on the hundred-nm level is expected.
Sublimation Growth and Defect Characterization of AlN Single Crystals
Authors: Wang Shaoping , Raghothamachar Balaji , Dudley Michael , Ren Zaiyuan , Han Jung , Timmerman Andrew G.
Published: April 2011

In this paper, we report results from AlN single crystal growth experiments using a sublimation physical vapor transport growth technique. AlN single crystal boules up to 7mm in diameter were demonstrated. Characterization of polished AlN single crystal samples was carried out using various techniques, including synchrotron X-ray topography.
“For Whom the Bell Tolls” Mexican Copper Bells from the Templo Mayor Offerings: Analysis of the Production Process and its Cultural Context
Authors: Schulze Niklas
Published: April 2011

The 3389 copper (alloy) bells from offerings included in successive building phases of Late Postclassic Templo Mayor (A.D. 1325 – 1520) of Tenochtitlan (Mexico City) are the results of production processes influenced by social, economic, ideological and technological factors. The compositional and morphological variability of the bells in the earlier construction phases of the Templo Mayor suggests the presence of several workshops in or around Tenochtitlan, while the reduction of this spectrum on one bell type made of copper-tin bronze, points towards a standardization of the production process and a decrease in the number of workshops that supplied the Templo Mayor in later phases. The compositional and morphological information, as well as contextual analysis and comparison with other Mexican bells, give insights into the bells' symbolism, the mechanisms used to supply the Templo Mayor with offerings, the organization of metalwork and the rationale behind some of the technological choices of the artisans. The detected changes through time seem to point to important shifts in the social, technological, economic and ideological influences on the choices of the artisans in the latter half of Aztec rule.
Painted Decoration Studies in a Fourth Century BC Vergina Tomb
Authors: Pavlidou Eleni , Kyriakou A. , Mirtsou E. , Anastasiou L. , Zorba T. , Hatzikraniotis E. , Paraskevopoulos K. M.
Published: April 2011

Aegae, the first capital of the Macedonians, in Northern Greece, is being excavated since 1938. The most impressive finds come from the unlooted tombs of the Great Tumulus, where the grave of Philip II, father of Alexander the Great, was discovered. Not far from the Great Tumulus, in the “Tumuli cemetery”, the most ancient part of the graveyard (1000-700 B.C.), recent excavations brought to light three looted graves dated in the mid-fourth century B.C., with very interesting finds such as weapons, gilded wreaths, pieces of jewelry, remains of decoration of wooden furniture, ceramic vases broken in small pieces and wall paintings. This paper describes studies carried out on the binding and the painting materials used for the decoration of the above wall paintings and ceramic vases. The characterization was performed through Optical Microscopy, Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Microscopy (SEM-EDS). It was found that the fresco technique was used, while all the pigments were identified. The results are discussed and related with other findings in that period in the Greek area
Silver Nanoparticle Films as Sulfide Gas Sensors in Oddy Tests
Authors: Chen Rui , Moussa Laura , Morris Hannah R. , Whitmore Paul M.
Published: April 2011

The preparation and performance of a silver nanoparticle-based sensor for use in Oddy tests are reported. A suspension of spherical silver nanoparticles (Ag NPs) (mean diameter of 30 nm, absorption of surface plasmon resonance (SPR) at 428 nm) in methanol was synthesized and the Ag NPs were self-assembled into monolayer films on glass slides, using polyethylenimine as a linking agent. UV-vis spectrophotometry was employed to measure the SPR intensity of the Ag NP films in order to evaluate the extent of reaction. It was observed that the Ag NP films were quite stable under Oddy test conditions in a blank test, after a brief alteration of the spectrum due to particle dispersal, with no significant decrease in the SPR intensity after 1.5 months at 60°C and 100% RH. The sensitivity of Ag NP films to sulfide gases emitted from a test wool fabric in the Oddy test was investigated. UV-vis spectra taken after the Oddy tests showed the disappearance of the Ag NP SPR peak and the growth of the UV absorption due to Ag2S. Elemental analysis with energy dispersive x-ray spectroscopy confirmed that sulfur had been incorporated into the Ag NP film. Ag NP assemblies of lower NP density were created that indicated the presence of sulfide gases prior to significant tarnishing of a Ag foil. The results demonstrate that the Ag NP films can be used as sensitive, quantitative optical sensors to replace Ag foils in the Oddy test system.
Effects of Ambient Oxygen on Initial Stage of Carbon Nanotube Formation in Surface Decomposition of 6H-SiC(000-1)
Authors: Maruyama Takahiro , Fujita Naomi , Naritsuka Shigeya , Kusunoki Michiko
Published: April 2011

It has been reported that carbon nanotubes (CNTs) were formed through the decomposition of SiC(000-1) surfaces by heating in a vacuum. By this growth technique, well aligned zigzag-type CNTs can be selectively formed without any catalysts and the diameters of the CNTs are fairly uniform. Moreover, this growth technique has an advantage in fabrication of CNT devices, since CNTs grow into the inside of SiC, facilitating the application of semiconductor process. So far, we have reported that ambient oxygen enhances the CNT growth rate [1]. However, the optimum oxygen pressure has never been investigated enough. It has also been reported that SiO2 layer is formed on SiC surface after annealing under high oxygen pressure [2]. In this study, we investigated the relation between surface oxide formation and CNT growth under various annealing conditions. After HF etching, 6H-SiC(000-1) (Carbon-face) samples were introduced into an ultra-high vacuum (UHV) chamber and annealed at various temperatures between 800 and 1250°C. During the annealing, oxygen partial pressure was controlled by supply of oxygen gas. The oxygen pressure was set between 10-4 and 1 Pa. For comparison, we also annealed several samples under UHV (10-6 Pa). Scanning tunneling microscopy (STM) observation and X-ray photoelectron spectroscopy (XPS) measurements were carried out to analyze their surface structures and chemical species. It was observed that the surface decomposition of SiC had occurred after annealing at 800°C under UHV, and carbon nanocaps were formed on the SiC surface at 1200°C, which subsequently transformed into CNTs. When oxygen pressure was below 10-2 Pa, the nanocap formation was observed between 1150 and 1200°C irrespective of oxygen pressure. However, at 1 Pa of oxygen pressure, SiO2 layer was observed on the SiC surface after annealing at 1200°C and no carbon nanocaps were observed. These results indicate that it is necessary to anneal SiC below 1 Pa to form CNT, although the presence of oxygen enhances CNT formation below 10-3 Pa. The boundary between the active oxidation and the passive oxidation in SiC oxidation estimated from our results was well consistent with previous studies for SiC oxidation under higher oxygen pressure (>1 Pa)[2]. From our results, in order to grow CNT effectively, it is important to minutely control oxygen pressure.
General Elasticity Theory for Graphene Membranes Based on Molecular Dynamics
Authors: Samadikhah Kaveh , Atalaya Juan , Huldt Caroline , Isacsson Andreas , Kinaret Jari
Published: April 2011

We have studied the mechanical properties of suspended graphene membranes using molecular dynamics (MD) and generalized continuum elasticity theory (GE) in order to develop and assess a continuum description for graphene. The MD simulations are based on a valence force field model which is used to determine the deformation and the elastic energy of the membrane (EMD) as a function of external forces. For the continuum description, we use the expression Econt = Estretching + Ebending for the elastic energy functional. The elastic parameters (tensile rigidity and Poisson ratio) entering Econt are determined by requiring that Econt = EMD for a set of deformations.

Comparisons with the MD results show excellent agreement. We find that the elastic energy of a supported graphene sheets is typically dominated by the nonlinear stretching terms whereas a linear description is valid only for very small deflections. This implies that in some applications, i.e. NEMS, a linear description is of limited applicability.
Carbon Nanotube Dispersion in Epoxy Nanocomposites with Clay
Authors: Liu Lei , Grunlan Jaime
Published: April 2011

Clay particles were used to facilitate the dispersion and network formation of single-walled carbon nanotubes (SWNTs) in an epoxy matrix. In the presence of clay, electrical conductivity increase and percolation threshold reduction for SWNT/epoxy composites were achieved simultaneously. These improvements are due to better SWNT dispersion, as evidenced by optical microscopy and scanning electron microscopy. Dynamic mechanical analysis (DMA) shows that mechanical properties of the composites without clay could be improved by clay addition. SWNTs appear to have an affinity for clay that causes them to become more exfoliated and better networked.
Effect of Graded AlxGa1-xN Interlayer Buffer on the Strain of GaN Grown on Si (111) Using MOCVD Method
Authors: Lin KungLiang , Chang Edward-Yi , Li Tingkai , Huang Wei-Ching , Hsiao Yu-Lin , Tweet Douglas , Maa Jer-shen , Hsu Sheng-Teng
Published: April 2011

GaN film grown on Si substrate with AlN/AlxGa1−xN buffer is studied by low pressure metal organic chemical vapor deposition (MOCVD) method. The AlxGa1−xN film with Al composition varying from 0∼ 0.66 was used. The correlation of the Al composition in the AlxGa1−xN film with the stress of the GaN film grown was studied using high resolution X-ray diffraction including symmetrical and asymmetrical ω/2θscans and reciprocal space maps. It is found that with proper design of the Al composition in the AlxGa1−xN buffer layer, crack-free GaN films can be successfully grown on Si (111) substrates using AlN and AlxGa1−xN buffer layers.
InGaN Thin Films Grown by ENABLE and MBE Techniques on Silicon Substrates
Authors: Reichertz Lothar A. , Yu Kin Man , Cui Yi , Hawkridge Michael E , Beeman Jeffrey W , Liliental-Weber Zuzanna , Ager III Joel W , Walukiewicz Wladyslaw , Schaff William J , Williamson Todd L , Hoffbauer Mark A.
Published: April 2011

The prospect of developing electronic and optoelectronic devices, including solar cells, that utilize the wide range of energy gaps of InGaN has led to a considerable research interest in the electronic and optical properties of InN and In-rich nitride alloys. Recently, significant progress has been achieved in the growth and doping of InGaN over the entire composition range. In this paper we present structural, optical, and electrical characterization results from InGaN films grown on Si (111) wafers. The films were grown over a large composition range by both molecular beam epitaxy (MBE) and the newly developed “energetic neutral atomic-beam lithography & epitaxy” (ENABLE) techniques. ENABLE utilizes a collimated beam of ∼2 eV nitrogen atoms as the active species which are reacted with thermally evaporated Ga and In metals. The technique provides a larger N atom flux compared to MBE and reduces the need for high substrate temperatures, making isothermal growth over the entire InGaN alloy composition range possible. Electrical characteristics of the junctions between n- and p-type InGaN films and n- and p-type Si substrates were measured and compared with theoretical predictions based on the band edge alignment between those two materials. The predicted existence of a low resistance tunnel junction between p-type Si and n-type InGaN was experimentally confirmed.
A Comprehensive Study of Growth Techniques & Characterization of Epitaxial Ge1−xCx (111) Layers Grown Directly on Si (111) for MOS Applications
Authors: Jamil Mustafa , Donnelly Joseph P , Lee Se-Hoon , Shahrjerdi Davood , Akyol Tarik , Tutuc Emanuel , Banerjee Sanjay K
Published: April 2011

We report the growth and characterization of thin germanium-carbon layers grown directly on Si (111) by ultra high-vacuum chemical vapor deposition. The thickness of the films studied is 8-20 nm. The incorporation of small amount (less than 0.5%) of carbon facilitates 2D growth of high quality Ge crystals grown directly on Si (111) without the need of a buffer layer. The Ge1−xCx layers were grown in ultra high vacuum chemical vapor deposition chamber, at a typical pressure of 50 mTorr and at a growth temperature of 440 °C. CH3GeH3 and GeH4 gases were used as the precursors for the epitaxial growth. The Ge1−xCx films were characterized by atomic force microscopy (AFM), secondary ion mass spectroscopy, x-ray diffraction, cross-sectional transmission electron microscopy and Raman spectroscopy. The AFM rms roughness of Ge1−xCx grown directly on Si (111) is only 0.34 nm, which is by far the lowest rms roughness of Ge films grown directly on Si (111). The dependence of growth rate and rms roughness of the films on temperature, C incorporation and deposition pressure was studied. In Ge, (111) surface orientation has the highest electron mobility; however, compressive strain in Ge degrades electron mobility. The technique of C incorporation leads to a low defect density Ge layer on Si (111), well above the critical thickness. Hence high quality crystalline layer of Ge directly on Si (111) can be achieved without compressive strain. The fabricated MOS capacitors exhibit well-behaved electrical characteristics. Thus demonstrate the feasibility of Ge1−xCx layers on Si (111) for future high-carrier-mobility MOS devices that take advantage of high electron mobility in Ge (111).
Concentric Metallic-Piezoelectric Microtube Arrays
Authors: Fan Hongjin , Kawasaki S. , Gregg J. M. , Langner A. , Leedham T. , Scott J. F.
Published: April 2011

Trilayer concentric metallic-piezoelectric-metallic microtubes are fabricated by infiltrating porous Si templates with sol precursors. LaNiO3(LNO) is used as the inner and outer electrode material and PbZrTiO3(PZT) is the middle piezoelectric layer. Structure of the microtubes is characterized in details using scanning and transmission electron microscopy which are equipped with energy dispersive X-ray spectroscopy for elemental mapping. The hysteresis of a trilayered thin film structure of LNO-PZT-LNO is shown. This trilayered tubes might find applications in inkjet printing.
Fused Heterocyclic Aromatics as Potential Organic Semiconductors: a Theoretical Study
Authors: Tal Faleh Al , Pham Phuong-T T. , Al-Maadeed Mariam Ali , Bader Mamoun M.
Published: April 2011

We report herein the results of density functional theory calculations of the geometric and electronic structure for a series of fused heterocyclic compounds. These molecules were compared with the corresponding carbocyclic oligoacenes, which are currently being experimentally investigated for use as organic semiconductors. The impact of various structural modifications on this class of compounds on the calculated structures is examined. The results of our calculations reveal that such materials hold exceptional promise as organic semiconductors.
Variable Temperature Measurement on Operating Pentacene-Based OTFT
Authors: Chen Hung-Keng , Liu Po-Tsun , Chang Ting-Chang , Shy S.-L.
Published: April 2011

Variable temperature electrical measurement is well-established and used for determining the conduction mechanism in semiconductors. There is a Meyer¡VNeldel relationship between the activation energy and the prefactor with a Meyer¡VNeldel energy of 30.03 meV, which corresponds well with the isokinetic temperature of about 350 K. Therefore, the multiple trapping and release model is properly used to explain the thermally activated phenomenon. By the method, an exponential distribution of traps is assumed to be a better representation of trap states in band tail. Samples with higher temperature during measurement are observed to show better mobility, higher on-current and lower resistance, which agree well with the multiple trapping and release model proposed to explain the conduction mechanism in pentacene-based OTFTs.
Anisotropic and Enhanced FET Performance in Rubbing-Aligned CuPc Thin Film Transistor with Top Gate Structure
Authors: Goto Masanao , Watakabe Yohei , Takezoe Hideo , Ishikawa Ken
Published: April 2011

the proceeding of the poster session
Inter Laboratory Comparison and Analysis on Mechanical Properties by Nanoindentation
Authors: Alvarado-Orozco J. M. , Cárdenas-Jaramillo C. , Torres-Torres D. , Herrera-Basurto R. , Hurtado-Macias A. , Muñoz-Saldaña J. , Trápaga-Martinez G.
Published: April 2011

This contribution presents the results obtained by a Mexican laboratory in the Asia-Pacific Economy Cooperation Interlaboratory Comparison (IC) on mechanical properties by nanoindentation from 2008 using fused silica and polycarbonate as samples. Reduced modulus and indentation hardness are the parameters asked to be measured and compared. The aim for this paper is to show and to discuss the so called “indentation size effect” (ISE) on the indentation hardness of fused silica. Using the spherical formulation of the ISE model for crystalline materials, the macroscopic hardness and material length scale of fused silica are determined as (7.34 ± 0.085) GPa and (166.36 ± 14) nm, respectively.
Synthesis and Mechanical Characterization of Aluminum Based Composites Prepared by Powder Metallurgy
Authors: Estrada-Guel I. , Cardoso J. L. , Careño-Gallardo C. , Herrera-Ramírez J. M. , Martínez-Sánchez R.
Published: April 2011

Aluminum-based composites prepared from pure Al powder and previously Cu metallized graphite are fabricated by a solid state route and are characterized by X-ray diffraction and scanning electron microscopy in order to follow their microstructural evolution. Composites are processed using powder metallurgy technique in order to obtain cylindrical samples to carry out mechanical testing. Microstructural and mechanical characterizations reveal that, by milling, a homogeneous dispersion of insoluble particles into the Al matrix is obtained; this produces an important improvement in hardness and strength with respect to an un-milled sample. Milling intensity and particle concentration have an important effect on the mechanical properties of the synthesized composites.
High-Temperature Oxidation Resistant Nanocoatings on Austenitic Stainless Steels
Authors: Lopez Hugo F.
Published: April 2011

In recent years, the increasing energy costs have lead to power utility industries to seek/develop high efficiency systems of production and of energy utilization. In addition, environmental concerns regarding greenhouse gas emissions are playing a major role in the development of clean energy systems. The development of metallic materials that can withstand elevated temperatures is among the viable alternatives to increase energy efficiency. Nevertheless, for this to happen, the corrosion and oxidation resistance of Fe- and Ni-based alloys needs to be significantly improved. Among the possible ways to enhance the life of high temperature alloys is the application of protective ceramic coatings. Conventional coatings are expensive and the protective effects controversial at times. An alternative which offers a great potential is the application of nano-ceramic coatings. Hence, in this work nanocrystalline coatings based on nano-CeO2 are applied to an austenitic stainless steel 304L and then exposed to elevated temperatures. Weight changes are monitored as a function of time and the results are compared with uncoated alloys tested under similar conditions. In addition, computer simulations of possible rate limiting diffusion mechanisms are carried out. It is found that the nanocoatings provided remarkable high-temperature oxidation resistance and improved scale adhesion. In particular, it is found that the smaller the nanoparticles are, the more effective the nanocoatings in providing oxidation resistance.
A Thermal Stage for Nanoscale Structure Studies with the Scanning Force Microscope
Authors: Kulnis W. J. , Unertl W. N.
Published: April 2011

We have constructed an inexpensive sample mounting stage for studies of temperature dependent processes in a surface force microscope (SFM). The stage is constructed from a Peltier thermoelectric heater secured to a standard SFM mounting stage with silver paint. The sample temperature can be varied from room temperature to about 100°C thus making it possible to use the SFM to observe thermally activated processes at lateral spatial resolutions of 10-20 nm. Approximately 10 minutes is required to reach thermal equilibrium following a 5°C temperature change. The lateral magnification must be calibrated at each temperature. We illustrate the capabilities of the stage with images of polystyrene spheres just below their glass transition temperature of 100°C.
Stm Studies at Electrochemically Controlled Interfaces
Authors: Lindsay S.M. , Pan J. , Jing T.W.
Published: April 2011

We use electrochemical methods to control the adsorption of molecules onto an electrode for imagingin-situby scanning tunneling microscopy. Measurements of the barrier for electron tunneling show that the mechanism of electron transfer differs from vacuum tunneling. Barriers depend upon the direction of electron tunneling, indicating the presence of permanently aligned dipoles in the tunnel gap. We attribute a sharp dip in the barrier near zero field to induced polarization. We propose a ‘tunneling’ process consisting of two parts: One is delocalization of quantum-coherent states in parts of the molecular adlayer that hybridize strongly (interaction ≥kT) with Bloch states in the metal. This gives rise to a quantum-point-contact conductance,Gc≤ 2e2/hat a height zo. The other part comes from the exponential decay of the tails of localized states, G =Gcexp{−2K(z − z0)}. Because measured decay lengths, (2K‘)−1, are small (≈ 1 Å), STM contrast is dominated by the contour along which G[z0(x,y)] = Gc. Measured changes in z0are used to calculate images which are in reasonable agreement with observations. We illustrate this with images of synthetic DNA oligomers.
Nanometer Scale Structures Resulting from Graphite Oxidation
Authors: Nowakowski Marilyn J. , Vohs John M. , Bonnell Dawn A.
Published: April 2011

Scanning tunneling microscopy (STM) and spectroscopy (STS) were used to characterize highly oriented pyrolytic graphite (HOPG) which was oxidized by two different methods, furnace heating in atmosphere and immersion in oxygen plasma. The character of the surfaces was found to be dissimilar on a micron scale but comparable on a nanometer scale, at which both appear to be comprised of sharp step edges. Variations in local electronic structure near a step edge were compared.
Cross-Sectional Scanning Tunneling Microscopy of III-V Quantum Structures
Authors: Johnson M.B. , Pfister M. , Alvarado S.F. , Salemink H.W.M.
Published: April 2011

In this paper, we report on the use of cross-sectional scanning tunneling microscopy (XSTM) to analyze several aspects of MBE-grown III-V quantum structures on an atomic scale. In particular, we discuss our recent work to identify various atomic species within the same chemical group (e.g. Al and Ga within the group Ill sublattice of AlGaAs) thereby allowing the determination of atomic roughness at GaAs/A1GaAs interfaces and alloy clustering in AlGaAs. We demonstrate and discuss the sensitivity of the STM to individual dopants in the near surface layers, as well as to the local carrier concentration. Lastly, we use XSTM to obtain images of cross-sectioned GaAs/AIGaAs quantum well wires with atomic detail.
An Analysis by Scanning Acoustic Microscopy of the Mechanical Stability of PSG and Si3N4 Passivation Films
Authors: Scafidi P. , Ignat M. , Mortini P. , Marty M.
Published: April 2011

Two types of mechanical tests associated with acoustic microscopy characterizations were performed to investigate the mechanical stability of PSG and Si3N4 passivation films. An in situ tensile test micro-device was installed under a scanning acoustic microscope to study the damage development in the passivation films deposited on A1,1%Si substrates. The analysis of the attenuation of the acoustic signature of the film/substrate systems and the variations of the leaky surface acoustic wave velocity permitted detection of the cracking and decohesion of the passivation films. The four-point bending test was used to submit passivated aluminum multilayers deposited on silicon substrates to cyclic compression. Then subsurface acoustic images revealed decohered zones in the passivation.
Plasticity, Microstructure and the Thermal Dependence of Flow Stresses in Aluminum Thin Film Interconnects
Authors: Venkatraman Ramnath
Published: April 2011

A study was conducted towards fundamentally understanding the nature and magnitude of thermal stresses in aluminum thin films on silicon and correlating them with deformation mechanisms that serve to relax the stresses imposed by the thermal strain. A number of experiments and theoretical considerations are described in order to describe the sources of strengthening and stress relaxation in such films. It is shown that the flow stress of an aluminum film corresponds to the critical stress required to drive dislocation glide events. This mechanism entails an inverse flow stress dependence on the film thickness and grain size. A novel set of experiments in which the effects of strengthening due to finite film thickness and the grain size were separated and quantified is described. The variation of these strengthening components with temperature during heating and cooling were noted. Theoretical considerations of diffusional relaxation combined with the results of grazing incidence X-ray scattering (GIXS) experiments suggest that grain boundary diffusion is much less effective in limiting film flow stress than would be expected from the strain rate relation derived for a free-standing film. Line broadening observations in the GIXS experiments suggested large changes in dislocation density in the tested films during thermal cycling. The nature of these variations are qualitatively consistent with those of the film flow stress, suggesting that strain hardening could be an additional strengthening mechanism in Al films during thermal cycling.
Stress Relaxation and Electromigration Kinetics in Short Metal Lines: Transition to Creep Controlled Regime
Authors: Glickman E. , Klinger L. , Katsman A. , Levin L.
Published: April 2011

An analysis of transition from the electrotransport controlled to the creep controlled electromigration (EM) is made for the Blech test geometry. The analysis rests on the approach developed by the authors with relaxation of electromigration induced stress by diffusional creep and non-linear stress distribution along the line. The derived solution confirms the idea of Glickman and Vilenkin that for high current density as the length of the line decreases the transition from the electrotransport controlled to the creep controlled electromigration kinetics must occur. The value of introduced parameter r that relates electromigration behavior to the creep viscosity is estimated by the comparison with experimental observations for aluminum stripes and discussed in terms of the Coble creep mechanisms.
The Roles of Several E′ Variants in Thermal Gate Oxide Reliability
Authors: Conley John F. , Lenahan P.M. , Evans H.L. , Lowry R.K. , Morthorst T.J.
Published: April 2011

We combine electron spin resonance measurements with vacuum ultraviolet, ultraviolet, and corona bias charge injection schemes to examine the properties and charge trapping roles of three E′ variants in conventionally processed thermally grown thin film SiO2 on Si.
Early Failure Sites and Electromigration
Authors: Ramseyer George O. , Beasock Joseph V. , Renz Thomas E. , Walsh Lois H.
Published: April 2011

By definition, half of all interconnects fail before the measured mean time to failure (t50) is reached. To predict early failures the basic reactions occurring in the metallization and its environment must be understood. To this end, fatal interconnect failure sites were characterized by Auger electron spectroscopy, atomic force microscopy and backscattered scanning electron microscopy. CVD silicon dioxide passivation layer/fatal void interfaces of typical early failure voids were characterized and compared to a typical late failure void interface. The topographies of these fatal voids were also quantitatively compared to increase our understanding of early failure sites and electromigration.
Interpretation of Resistance Changes during Interconnect Reliability Testing
Authors: Sanchez John E. , Pham Van
Published: April 2011

Accelerated reliability testing of VLSI layered metallizations involves monitoring the resistance of interconnect test structures under the assumption that changes in the resistance are due to processes (i.e., damage) which are induced by the test conditions (current and/or temperature.) “Failure” of the interconnect is defined as a somewhat arbitrary increase in fractional resistance ΔR/Ro ≈ +10% to +30%, where Ro is the initial resistance. However interpretation of the measured ΔR/Ro (both positive and negative) is complicated by other processes, the test conditions, and the test structure itself which all contribute to ΔR/Ro. We estimate the magnitude of intrinsic factors, such as vacancies and solute effects, as well as extrinsic factors, such as interconnect strain and voiding, on measured on ΔR/Ro. We also show that localized joule heating at voids (a mixed intrinsic + extrinsic effect) principally accounts for the large ΔR/Ro measured during electromigration (i.e., high current) testing. These results suggest improved methods for the detection of interconnect voids induced by the stresses of passivation confinement. We outline the considerations which allow for more rigorous failure criteria which are scalable to any metallization layer scheme, interconnect length and test condition. Finally, we discuss the interpretation of resistance changes at interlevel via structures.
Effect of TiN ARC on Electromigration Performance of Tungsten Plug Via
Authors: Bui Nguyen D. , Pham Van H. , Forsythe D. David , Lee Raymond T. , Yue John T.
Published: April 2011

The effect of TiN Anti-Reflective Coating (ARC) layer capping of metal, in a multilevel interconnect system, on the reliability of the tungsten (W) plug has been investigated. EM study on Kelvin via showed that the thin TiN ARC Kelvin via lifetime exhibited a reduction of one order of magnitude compared to that of the thicker ARC thickness (1000Å) when they were stressed in a certain direction. A new testing technique, used to investigate the effect of ARC thickness on the W-plug electromigration (EM) performance, is discussed. The simulation results of current distribution confirmed the proposed failure model of EM performance of W-plug via with different ARC thickness.
Fracture Strength of Thin Ceramic Membranes
Authors: Liddle J. Alexander , Huggins H.A. , Mulgrew P. , Harriott L.R. , Wade H.H. , Bolan K.
Published: April 2011

The bulge test provides a convenient way to measure the mechanical properties, including fracture strength, of thin ceramic membranes. Thin (≈ 3000Å) films of non-stoichiometric SiNx, nominally defect-free and containing flaws introduced byfocused ion-beam machining, were examined. The use of such membranes in masks for projection electron-beam lithography systems makes it important to determine their ultimate strength and reliability. The mean fracture strength of the defect-free membranes was found to be 1.79±0.04GPa, and the Weibull modulus was estimated to be 49±15, giving a safe operating stress of 1.5GPa. The results of fracturing the samples containing flaws indicated that holes smaller than 15x0.5μm had no effect on the fracture strength of the membranes. By estimating the stress concentration factor for the slots, it was determined that the critical fracture stress was 16±3GPa.
Epitaxial CeO2 Growth on Si (111) for SOI
Authors: Tye L. , Chikyow T. , El-Masry N. A. , Bedair S. M.
Published: April 2011

Epitaxial growth of CeO2 was obtained on the Si(111) surface by laser ablation in UHV atmosphere. However, a dual amorphous layer formed at the interface, yielding a CeO2/α:-CeOx/α-SiO2/Si(111) structure. This structure is speculated to be caused by a reaction occurring between Ce oxide and Si. Post annealing in O2 ambient caused the regrowth of CeO2, eliminated the α-CeOx layer, and increased the thickness of the SiO2 layer. The new CeO2/SiO2/Si(111) structure shows improved breakdown voltage and fewer interfacial states as observed by C-V and I-V measurements. The SiO2 is expected to tie surface states with Si, whereas the single crystal CeO2 will allow the epitaxial growth of lattice-matched Si on this insulating film. The effect of growth conditions and O2 annealing on both the structural and the electrical properties of this epitaxial oxide will be presented.
Effects of Deposition Parameters on the Structure, Morphology and Chemical Composition of PLZT Thin Films
Authors: Ribeiro R. M. , Gomes M. J. M. , Gomes E. De Matos , Ferreira J. A. , Mantas P. L. Q. , Baptista J. L. , Costa M. M. R. R.
Published: April 2011

PLZT thin films from a stoichiometric (9/65/35) commercial target were laser deposited using the second and third harmonics of a nanosecond Nd:YAG laser. The films were grown on oriented sapphire substrates and analysed by X-ray diffraction, SEM and EDX techniques. The influence of the deposition parameters laser fluence and substrate temperature on the physical characteristics of the films is presented.
Positron Annihilation and X-Ray Photoelectron Spectroscopy Analyses of TiN/Si and TiN/SiO2/Si Films
Authors: Issar A. K. , Sharma S. C. , Chourasia A. R. , Chopra D. R.
Published: April 2011

We have characterized TiN/Si and TiN/SiO2/Si structures by utilizing the variable energy positron beam spectroscopy (VEPBS) and x-ray photoelectron spectroscopy (XPS). Thin films of TiN were grown on SiO2/Si and Si by chemical vapor deposition and sputtering. Details of the electronic structure, microstructural defects, and interface are probed by implanting monoenergetic positrons at varying depths and analyzing the resulting positron-electron annihilation gamma rays. This analysis provides results for the positron diffusion length in different parts of the layered structure. Being sensitive to the presence of lattice defects, the positron diffusion length can be used to assess the quality of the film. The XPS measurements provide details about the elemental composition and interface in these materials.
Deposition of Oxide Based Advanced Electronic and Optical Materials by Rapid Isothermal Processing (RIP) Assisted Metalorganic Chemical Vapor Deposition (MOCVD)
Authors: Mavoori J. , Singh R. , Sharangpani R. , Gong C. , Poole K. F. , Singh R. K. , Natarajan R.
Published: April 2011

Metalorganic chemical vapor deposition (MOCVD) is an ideal technique for the deposition of conducting and non-conducting oxide based thin film materials. In this paper we present our study of RIP assisted MOCVD for the low temperature deposition of a number of oxide based advanced materials which are useful for the development of the next generation of microelectronic and optoelectronic devices. We have designed several experiments to understand the role of photoeffects in RIP assisted MOCVD. The vacuum ultraviolet, ultraviolet and visible (λ ≤ 0.7–0.8μm) photons can have several beneficial effects including the enhancement of the surface reactions of the absorbed molecules through the perturbation of the electronic state of binding between the absorbed molecules and the solid surface. We have shown a direct relationship between the structural and electrical characteristics of the deposited oxide and the spectral contents of the energy source.
The High Dispersion of CuCl2in ZSM-5 by Using Microwave Method
Authors: Xiao Feng-Shou , Xu Wenguo , Qru Shilun , Xu Ruren
Published: April 2011

Three preparation methods of ZSM-5 supported copper were studied. The first sample is the mechanical mixture of CuCl2·2H2O with NaZSM-5 (Cu+ZSM-5), the second sample is the mechanical mixture of CuCl2·2H2O with NaZSM-5 followed by microwave treatment (Cu/ZSM-5), and the third sample is copper ion exchanged with NaZSM-5 (CuZSM-5). All the samples were characterized by XRD, DTA, and n-hexane adsorption. Cu+ZSM-5 samples showed characteristic XRD peaks of both NaZSM-5 and CuCl2·2H2O and Cu/ZSM-5 samples showed only NaZSM-5 XRD peaks; these results suggest that CuCl2·2H2O no longer exists in the crystalline state in Cu/ZSM-5 samples, possibly in a highly dispersed state. DTA experiments showed that Cu+ZSM-5 samples did exhibit the melting point of CuCl2and Cu/ZSM-5 did not. Furthermore, as compared with Cu+ZSM-5 and CuZSM-5, the n-hexane adsorption on Cu/ZSM-5 samples require higher n-hexane pressure to reach the saturated adsorption; these results suggest that the copper salt has entered the zeolite channels during microwave treatment, resulting in the change of channel circumstance for ZSM-5 zeolite. All these results suggest that microwave technique is a potential method for preparing highly dispersed metal salts in the channels or cages of zeolites.
PFC Concentration and Recycle
Authors: Tom Glenn M. , McManus James , Knolle William , Stoll Ilse
Published: April 2011

The semiconductor industry uses PFC gases such as CF4 and C2F6 as etchant and cleaning gases during plasma processes. The gases do not fully react within the reactor chamber. The unused gases enter the atmosphere through the process effluent. These gases have long persistence in the atmosphere and absorb infrared radiation. The PFC gases are, therefore, potential global warming gases. A method is described that will recover and recycle PFC gases.
Advanced Ceramics for Environmental Protection
Authors: Chambers Jeffrey A.
Published: April 2011

Advanced ceramic materials offer significant thermodynamic efficiency advantages over metals and alloys because of their higher use temperatures. Using ceramic components results in higher temperature industrial processes which convert fuels to energy more efficiently, reducing environmental emissions. Ceramics have always offered high temperature strength and superior corrosion and erosion resistance. However, brittleness, poor thermal shock resistance and catastrophic failure have slowed industrial adoptions of ceramics in environmental applications.

This paper will focus on environmental applications of three new advanced ceramic materials that are overcoming these barriers to industrial utilization through improved toughness, reliability, and thermal shock performance. PRD-66, a layered oxide ceramic with outstanding thermal shock resistance and high use temperature with utility in catalyst support, insulation, and hot gas filtration applications, is discussed. Tough silicon carbide fiber reinforced silicon carbide (SiC/SiC) and carbon fiber reinforced silicon carbide (C/SiC) ceramic composites made by chemical vapor infiltration, and silicon carbide particulate reinforced alumina (SiCp/A12O3) composites made through Lanxide Corporation's DIMOX™ directed metal oxidation process are described. Applications of these materials to pollution reduction and energy efficiency in medical and municipal waste incineration, heat management, aluminum remelting, pyrolysis, coal combustion and gasification, catalytic pollution control, and hot gas filtration, will be discussed.
Kinetic Study For The Formation Of The Oxygendeficient Magnetite
Authors: Togawa T. , Wada Y. , Yoshida T. , Tsuji M. , Tamaura Y.
Published: April 2011

An oxygendeficient magnetite (Fe3O4–8) has been found to exist in the range of (0<Δ<0.12) in the course of H2-reduction of magnetite to αFe at 300°C. The formation of the oxygendeficient magnetite was studied kinetically. In the temperature range of 250 350°C, the rate constants, k1, and k2, were determined for the forward and reverse reactions, respectively. The rate of formation of the oxygendeficient magnetite depended on the partial pressure of H2 gas. The rate constant, k1, was 109.58 at 300°C and the reaction order was 1.11 with respect to the partial pressure of H2 gas. The rate of reverse reaction depended on the partial pressure H2O gas and the oxygen deficiency of magnetite, Δ. The rate constant of the reverse reaction, k2, was 10−2.54 at 300°C, and the reaction orders were 0.45 and 0.99 with respect to the partial pressure of H2O gas and the Δ value respectively. The activation energies for the forward and reverse reactions were determined to be 63.8 kJ.mol−1 and 25.5 kJ.mol−1 from the Arrhenius' equation.
New Generation Reaction Of H2 From H2O With Carbon-Bearing Ferrites At 300 °C
Authors: Hasegawa Noriko , Akanuma Kazuhiro , Sano Taizo , Tsuji Masamichi , Tamaura Yutaka
Published: April 2011

The carbon-bearing magnetite (CBM) was prepared by the carbon-deposition on the H2- treated magnetite with CO2 at 300 °C. The CBM reacted with H2O and evolved H2 gas at 300- 350 °C. The surface of the CBM was composed of a new iron(II)oxide / carbon layer (CIOlayer). X-ray diffractometry and chemical analysis showed that the CIOlayer was transformed to an amorphous carbide phase by allowing to stand in Ar stream at 300 °C, which is so reactive as to decompose H2O into H2. The mole ratio of the evolved H2 gas to the evolved CO2 was nearly equal to that in the carbide (Fe3C) decomposition reaction with H2O. During the H2O decomposition, oxygen ions are transferred to the surface layer forming iron oxide. When the carbon-bearing Ni(II)-ferrite (CBNF) was used as the solid phase, the hydrogen evolution reaction takes place without decreasing in the carbon content in the CBNF, and the evolved H2 volume was approximately 8 times higher than that evaluated from the oxidized amount of the iron ions in the CBNF. This result suggests that some amount of oxygen in the CBNF is released while allowing to stand the sample in Ar stream at 300 °C. These H2 evolution reactions can proceed at low temperature of around 300 °C. This will provide us the way to establish a unique chemical heat pump system, where the waste heat around 300 °C be transferred to chemical energy of H2. The surface layer composed of iron(II) oxide/carbon is the key compound for this reaction.
Catalytic Conversion of CCl2F2 on γ-A12O3 Catalyst Systems
Authors: Bell T. N. , Kirszensztejnt P. , Czajkat B.
Published: April 2011

The reaction of CC12F2 (CFC 12) has been studied on a γ- A12O3 catalyst with and,withoutH2 and with H2 on a Pt/γ-A12O3 catalyst containing 0.5, 2 and 5 wt % of Pt at a temperature of 300°C. The extent of conversion, was shown to be highly dependent both on the metal coverage; and on the temperature.