bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimizing MIM Device Electrical Properties. Impact of Bottom Electrodes and High K Materials
Authors: Bonvalot Marceline , Vallée Christophe , Gourvest Emmanuel , Jorel Corentin , Gonon Patrice 
Published: February 2009

AbstractHigh quality MIM capacitors with improved capacitance density, low leakage currents and linear C(V) behaviour are the object of active research, with potential applications in CMOS, BICMOS and bipolar technologies as filters, analog to digital converters and related radio-frequency operating devices. Several high-k materials (Ta2O5, HfO2, Y2O3, Al2O3-HfTiO, HfON-SiO2) have been put on trial as possible candidates for SiO2 substitution which is required by the aggressive downscaling of electronic devices. Among those, HfO2- based materials seem to offer promising properties, combining a high chemical stability with Si and a high k value. However, HfO2 shows a strong ability to favour charge defects such as oxygen vacancies, which in turn affect the intrinsic properties of devices such as threshold voltage or leakage currents. These oxygen vacancies are actually thought to accumulate in the vicinity of the electrode, thus forming an oxidized interfacial layer and inducing a significant voltage linearity degradation of MIM capacitors.In this work, it will be shown that this oxide layer thickness can be strongly minimized by using appropriate bottom electrode material. Indeed, high work function materials can efficiently prevent oxygen vacancies charge stocking on their surface. Several MIM devices have been prepared based on HfO2, Al2O3 and SrTiO3 as dielectric materials, and TiN, WSi2.7 and Pt as bottom electrode material. All these devices have been fully characterized in terms of materials properties and electrical behaviour. These results have been analysed and show that a reduced dielectric thickness is preferred to achieve high capacitance density, but is also responsible for voltage linearity degradation. High work function electrode material can help improve this degraded linear behaviour, thanks to the formation of a reduced interfacial oxygen trap layer thickness. Leakage currents seem to be deeply correlated with the morphological state of the dielectric material, an amorphous state being obviously more efficient to prevent current pathways through grain boundaries.All these results will be presented in detail and discussed with regards to different models proposed in the literature to account for these data.
The effect of BCl3 pretreatment on the etching of AlN in Cl2-based plasma
Authors: Xu Xiaoyan , Kuryatkov Vladimir , Borisov Boris , Pandikunta Mahesh , Nikishin Sergey A , Holtz Mark 
Published: February 2009

AbstractThe effect of BCl3 and BCl3/Ar pretreatment on Cl2/Ar and Cl2/Ar/BCl3 dry etching of AlN is investigated using inductively coupled plasma reactive ion etching. The native AlN oxide can be effectively removed by a short exposure to BCl3 or BCl3/Ar plasma. Compared to the chlorine based plasma etching, BCl3/Ar is found to have the highest etch rate for both AlN and its native oxide. Following removal of the native oxide, Cl2/Ar/BCl3 plasma etching with 15% BCl3 fraction results in a high etch rate ˜ 87 nm/min and modest increases in the surface roughness.
Ambient Copper-Copper Thermocompression Bonding using Self Assembled Monolayers
Authors: Ang Xiaofang , Wei Jun , Chen Zhong , Wong Chee Cheong 
Published: February 2009

AbstractA typical copper-copper thermocompression bonding process is carried out in an ultrahigh vacuum (UHV) or inert environment at a bonding temperature >300°C. The ultraclean environment serves a single purpose – to maintain oxide-free copper surfaces, allowing intimate physical contact between copper atoms. This study investigates the temperature dependence of direct copper bonding from room temperature to 300°C under ambient condition. An anomalous thermal dependence of bond strength occurs between 80°C to 140°C where an increase in bonding temperature within this regime is in fact, detrimental to joint strength. This is interpreted as a thermal competition between oxidation and bond formation. This study also demonstrates that by simply coating the copper surface with a self assembled monolayer of 1-undecanethiol prior to bonding, Cu joints can be successfully formed at close to ambient temperature without a vacuum, yielding joint shear strengths on the order of 70MPa. The densely packed monolayer serves to passivate the copper surface against oxidation under ambient conditions. The ultrathin organic monolayer structure, as compared to a bulk oxide layer, could be easily displaced during the mechanical deformation at the bonding interface which accompanies thermocompression. This method could be an effective simple bonding solution for three-dimensional integrated chips.
Three-Dimensional Integration Technology Based on Self-Assembled Chip-to-Wafer Stacking
Authors: Fukushima Takafumi , Tanaka Tetsu , Koyanagi Mitsumasa 
Published: February 2009

AbstractWe have demonstrated that a number of known good dies (KGDs) can be precisely aligned in batch and stacked on LSI wafers by our chip-to-wafer three-dimensional (3D) integration technology using an innovative self-assembly technique. Compared with conventional robotic pick-and-place chip assembly, the fluidic self-assembly can provide high-throughput chip alignment and bonding, and the resulting self-assembled chips have high alignment accuracy of approximately 0.3 micron on average. Immediately after chip release, the chips are aligned onto the predetermined hydrophilic bonding areas in a short time within 0.1 sec by the surface tension of aqueous liquid used in our self-assembly. By using the self-assembly, a number of KGDs with different chip sizes, different materials and different devices can be stacked in high yield to give highly integrated 3D chips we call the 3D Super Chip.
Level Spectrum of a Single Gated Arsenic Donor in a Three Terminal Geometry
Authors: Lansbergen Gabriel P. , Rahman Rajib , Wellard Cameron J. , Caro Jaap , Woo Insoo , Colleart Nadine , Biesemans Serge , Klimeck Gerhard , Hollenberg Lloyd , Rogge Sven 
Published: February 2009

AbstractState of the art CMOS devices have been scaled to such dimensions that we need take atomistic approach to understand their operation for nano-electronics. From a bottoms-up perspective, the smallest functional element within a nano-device would be a single (dopant) atom itself. Control and understanding of the eigenenergies and wavefunctions of a single dopant in Si is a key ingredient for device technology beyond-CMOS like quantum-information processing. Here, we will discuss the eigenlevels of a single As donor in a three terminal configuration. The donor is incorporated in the channel of prototype transistors called FinFETs. The measured eigenlevels are shown to consist of levels associated with the donors Coulomb potential, levels associated with a triangular well at the gate interface and hybridized combinations of the two. The theoretical framework in which we describe this system (NEMO-3D) is based on a tight-binding approximation.
Magnetic Transitions in the Double Perovskite Sr2FeRe1-xFexO6(0≤X≤0.5)
Authors: Gao Haitao , Ksenofotov Vadim , Barth Joachim , Panthöefer Martin , Claudia Felser , Tremel Wolfgang 
Published: February 2009

AbstractThe synthesis, structure, and magnetic and transport properties of solid solutions Sr2FeRe1-xFexO6 (0≤x≤0.5) are reported. A structural evolution in the solid solutions from a double perovskite to perovskite is observed with increasing Fe/Re disorder. Except for the metallic parent compound all members of the series are semiconducting. For the Fe-doped samples a change from ferrimagnetic interactions in the parent compound to a complex superposition of ferrimagnetic and antiferromagnetic interactions was observed. The magnetic moment decreases with x, whereas the Curie temperature TC remains unaffected. The magnetic and Mössbauer data suggest Fe to act as a redox-buffer.
Charge-Transfer Properties of Dye-Sensitized Solar Cells via Long-Range-Corrected Density Functional Theory
Authors: Wong Bryan Matthew 
Published: February 2009

AbstractThe excited-state properties in a series of solar cell dyes are investigated with a long-range-corrected (LC) functional which provides a more accurate description of charge-transfer states. Using time-dependent density functional theory (TDDFT), the LC formalism correctly predicts a large increase in the excited-state electric dipole moment of the dyes with respect to that of the ground state, indicating a sizable charge separation associated with the S1 ← S0 excitation. The performance of the LC-TDDFT formalism, illustrated by computing excitation energies, oscillator strengths, and excited-state dipole moments, demonstrates that the LC technique provides a consistent picture of charge-transfer excitations as a function of molecular size. In contrast, the widely-used B3LYP functional severely overestimates excited-state dipole moments and underestimates the experimentally observed excitations, especially for larger dye molecules. The results of the present study emphasize the importance of long-range exchange corrections in TDDFT for investigating the charge-transfer dynamics in solar cell dyes.
Efficient Light Harvesting with LB Films for Application in Crystalline Silicon Solar Cells
Authors: Danos Lefteris , Markvart Tomas 
Published: February 2009

AbstractWe have carried out fluorescence lifetime measurements using time correlated single photon counting (TCSPC) for a cyanine dye near the silicon surface. The measurements have been carried out for both (100) and (111) crystal orientations of the silicon surface, showing the dependence of energy transfer rate as a function of the separation between the dye monolayer and the silicon surface. Langmuir Blodgett fatty acid layers were used to create a multistep structure and a monolayer of a cyanine dye was deposited on top of the stepped structure. Spectroscopic ellipsometry has been used to measure the thickness of the fatty acid steps and provide an accurate estimate of the distance of the dye monolayer to the silicon surface. Time resolved emission spectra and fluorescence decay curves were measured with a single photon picosecond time correlated system. We find that the fluorescence lifetime of the dye monolayer is significantly shortened when present close to the silicon surface signifying efficient energy transfer. The dissipation of the excitation energy near silicon is explained using the classical theory developed for metals and a deviation is observed for distances close to the silicon surface (d<5nm). The model can be reconciled with the observed data by modifying the value of the silicon extinction coefficient which can provide an insight into the energy transfer process in the near field dye-silicon interaction.
A Comparison of Electrochemical Performance of Double Perovskite REBaCo2O5+x Cathodes in Symmetrical Solid Oxide Fuel Cells
Authors: Gong Wenquan , Yadav Manoj , Jacobson Allan J. 
Published: February 2009

AbstractThe segregated vacancies in the A site-ordered oxygen-deficient double perovskites REBaCo2O5+x (RE = La, Pr, Nd, Sm, Eu) (RBCO) are thought to greatly enhance the diffusivity of oxide ions in the bulk of these materials and possibly supply surface defect sites with enhanced reactivity towards molecular oxygen. Some materials in this family of REBaCo2O5+x compounds, such as PrBaCo2O5+x, (PBCO), have already demonstrated high electronic conductivity, rapid oxygen ion diffusion and surface exchange kinetics. Therefore, the family of REBaCo2O5+x compounds were synthesized and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (SOFCs) based on gadolinium doped ceria (CGO) electrolytes. The electrochemical performance of symmetrical cells (REBaCo2O5+x + CGO composite cathodes on the CGO electrolytes) was evaluated by using AC impedance spectroscopy. The area specific resistance (ASR) performance was measured as a function of temperature as well as oxygen partial pressure.
Screening and Fabrication of Half-Heusler Phases for Thermoelectric Applications
Authors: Wunderlich Wilfried , Motoyama Yuichiro 
Published: February 2009

AbstractHalf-Heusler phases have gained recently much interest as thermoelectric materials. Screening of possible systems was performed by drawing their stability region in a three-dimensional Pettifor map. The fabrication of Half-Heusler phases requires three steps, surface activation of the raw material by ball milling, arc-melting of pressed pellets and finally long-term annealing treatment in a vacuum furnace. On doped TiCoSb specimens, Seebeck coefficients of 0.1 mV/K, on NiNbSn 0.16 mV/K were measured, although the microstructure was not yet optimized.
An overview of the ESA-ESRF-ILL collaboration in the framework of the IMPRESS Integrated Project
Authors: Reinhart G. , Iles G.N. , McIntyre G.J. , Fitch A.N. , Jarvis D.J. 
Published: February 2009

AbstractThree intergovernmental research organizations from the EIROforum collaboration: the European Space Agency (ESA), the European Synchrotron Radiation Facility (ESRF) and the Institut Laue-Langevin (ILL), are cooperating to perform advanced experimental characterization in the field of materials science within the framework of the IMPRESS Integrated Project. This project aims to develop and test two distinct prototype-based intermetallic materials: (i) γ-TiAl turbine blades for aero-engines and stationary gas turbines, and (ii) Raney-type Ni-Al catalytic powder for use in hydrogen fuel cell electrodes and hydrogenation reactions. The opportunity to carry out investigations combining the use of both synchrotron radiation at the ESRF and neutrons at the ILL provides unique experimental data to complement other benchmark experiments performed on the ground and in microgravity. We present an overview of the different synchrotron X-ray and neutron characterization techniques implemented at ESRF and ILL to study the solidification and subsequent processes leading to the final products for these two materials.
Phase Field Simulation of Coarsening Kinetics in Al-Sc and Al-Sc-Zr Alloys
Authors: Zapolsky H. , Boisse J. , Patte R. , Lecoq N. 
Published: February 2009

AbstractThe coarsening kinetics of γ’ precipitates in binary and ternary Al3Sc1-xZrx alloys is studied by using the two- and three-dimensional phase-field simulations. Our focus is on the influence of diffusion coefficients of Sc and Zr atoms on the transformation path kinetics from disordered f.c.c. matrix to two phases equilibrium state with γ’ precipitates and f.c.c. disordered matrix. Our simulation results demonstrate that in the case of binary alloys taking into account the concentration dependence of the mobility of atoms decreases the coarsening rate. In the case of ternary alloys we show that the Al3Sc particles precipitate first following by appearance of a Zr-rich shell. Our simulations results are in good agreement with experimental observations.
An Experimentally Validated Micromechanical Model for Elasticity and Strength of Hydroxyapatite Biomaterials
Authors: Fritsch Andreas , Dormieux Luc , Hellmich Christian , Sanahuja Julien 
Published: February 2009

ABSTRACTHydroxyapatite biomaterials production has been a major field in biomaterials science and biomechanical engineering. As concerns prediction of their stiffness and strength, we propose to go beyond statistical correlations with porosity or empirical structure-property relationships, as to resolve the material-immanent microstructures governing the overall mechanical behavior. The macroscopic mechanical properties are estimated from the microstructures of the materials and their composition, in a homogenization process based on continuum micromechanics. Thereby, biomaterials are envisioned as porous polycrystals consisting of hydroxyapatite needles and spherical pores. Validation of respective micromechanical models relies on two independent experimental sets: Biomaterial-specific macroscopic (homogenized) stiffness and uniaxial (tensile and compressive) strength predicted from biomaterial-specific porosities, on the basis of biomaterial-independent (‘universal') elastic and strength properties of hydroxyapatite, are compared to corresponding biomaterial-specific experimentally determined (acoustic and mechanical) stiffness and strength values. The good agreement between model predictions and the corresponding experiments underlines the potential of micromechanical modeling in improving biomaterial design, through optimization of key parameters such as porosities or geometries of microstructures, in order to reach desired values for biomaterial stiffness or strength.
Graphened IR Screens: A New Spectroscopic Platform For Bio-Species
Authors: Banerjee Amrita , Moeller Dieter , Grebel Haim 
Published: February 2009

Abstract
Metallo-dielectric screens are periodic structures, which are at resonance with the infrared (IR) wavelength of interest: a standing wave of surface charges is formed at resonance conditions, which enables transmission or, reflection of certain IR bands. Graphene is a monolayer thick crystal of carbon. It is chemically inert and exhibits very large electronic mobility. Recently, we succeeded in fabricating mono and a few-layered suspended graphene on top of these screens. We combined these two unique components in fabricating novel platforms, which enhance IR signals of soft bio-species. Specifically, we used these platforms to examine IR spectra of a model protein, cytochrome c from a bovine heart tissue. Clear Raman signal variation as a function of platform orientation has been demonstrated. Accentuation of the IR absorption spectra was shown as well.
Design of a Biocompatible and Optically-Stable Solution-Phase Substrate for SERS Detection
Authors: Roca Maryuri , Mackie Prescott M. , Hae Amanda J. 
Published: February 2009

Abstract
Detection of important biological molecules using surface-enhanced Raman scattering (SERS) has become widely used because of the highly sensitive and label free approach offered by SERS as well as the low cytotoxic response from some SERS substrates. Gold nanoparticles are commonly used in SERS studies; however, the inherent instability of these metal nanostructures in solution adversely influences the reproducibility and quantitative nature of these measurements. Furthermore, the metal surface often denatures biomolecules upon their direct interaction. To combat this incompatibility and improve optical stability, gold nanoparticles have been encapsulated in silica shells. These Au@SiO2 nanostructures have been used extensively in cellular studies, but their SERS capabilities are generally limited to uses that include silica-entrapped SERS reporter molecules rather than direct SERS detection. This work focuses on combating these limitations via the fabrication of Au@SiO2 nanoparticles with porous silica membranes for the direct detection of target molecules in solution. Gold nanoparticles have been designed and coated with a variety of silica morphologies and subsequently interrogated using extinction spectroscopy and SERS. It will be revealed that these gold nanoparticles entrapped in silica membranes serve as optically stable substrates for the quantitative and direct detection of target molecules. These advances in nanomaterial fabrication are envisioned to impact both fundamental and applied studies in a variety of research areas including catalysis, separations, and spectroscopy.
Identifying the limitation of Oliver and Pharr method in characterizing the viscoelastic-plastic materials with respect to indenter geometry
Authors: Balasundaram Keerthika , Cao Yanping , Raabe Dierk 
Published: February 2009

AbstractNanoindentation tests are widely used in recent years to characterize the mechanical properties of viscoelastic-plastic materials like polymers and biomaterials at the micro or nano-scale using the analysis method proposed by Oliver & Pharr (OP). However, recent studies revealed that the mechanical properties of viscoelastic-plastic (polymeric) materials determined using the OP method does not lead to a correct evaluation of Young's modulus. A systematic experimental study is performed with different indenter geometries like spherical and Berkovich geometries using various polymers in order to identify the limitations of the OP method.
Measurement and Analysis of Structural Damping in Silicon Carbide Microresonators
Authors: Prabhakar Sairam , Nabki Frederic , El-Gamal Mourad , Vengallatore Srikar 
Published: February 2009

AbstractThe design of microresonators with high natural frequencies (1 MHz to 1 GHz) and low structural damping is essential for devices used for applications in communications. Here, we report experimental measurements of damping at low pressure and ambient temperature in electrostatically-actuated, metallized silicon carbide microresonators. Comparison of the measured values with the predictions of a model for thermoelastic damping indicates that the contribution of this mechanism to the measured damping ranges from 10% to 50% over a broad frequency range (3 MHz to 30 MHz).
Effects of Aspect Ratio of Micro-sized Photoresist Patterns on Bond Strength between a Si Substrate with AFM Fracture Observation
Authors: Ishiyama Chiemi , Shibata Akinobu , Sone Masato , Higo Yakichi 
Published: February 2009

AbstractBond strength between three dimensional micro-sized cylindrical patterns and Si substrate has been evaluated to clarify the effects of the cylinder length vs. diameter ratio, i.e. the aspect ratio, on the bond strength. Cylindrical shape was employed for avoiding ambiguity of loading point under bend conditions. Multiple cylindrical specimens of an epoxy type photoresist, SU-8 with various lengths were fabricated on a silicon substrate under the same photolithographic condition. Bond strength between micro-sized SU-8 and Si substrate under bend loading mode was measured by a mechanical testing machine for micro-sized materials. The maximum bend moment is 9.6 × 10−6 Nm in average and lineally increases with increasing the aspect ratio. On the other hand, the maximum load, i.e. maximum shear load is 106 mN in average and almost constant with increasing aspect ratio. This result suggests that the shear stress near the interface may cause the initiation of delamination. This phenomenon is discussed with three dimensional fracture observation and quantitative analysis of the line profile around the initiation site by AFM.
Controlling the Wrinkling of the Bilayer Thin Films Electrothermally
Authors: Chintapatla Shravan , Muth John F. , Lunardi Leda M. 
Published: February 2009

AbstractWrinkling of thin sheets under strain is a universal phenomenon. The amplitude and period of the wrinkles formed in a thin sheet clamped at both ends are dependent on its strain and material parameters. In our study, wrinkling is observed in microscale for double clamped thin films (L>W>>t) consisting of 200nm deposited low stress silicon nitride bridges fabricated by bulk micromachining. A bilayer system is formed with 30nm aluminum evaporated on to these bridges. At room temperature the bridges are essentially flat. When an electrical current passes through the aluminum layer electrothermal, heating results in thermal expansion that wrinkles the bilayer. In addition we investigated various dimensions of the bridges and their correlation to the amplitude and the number of wrinkles. The observations are compared to existing wrinkling theory.