bluuebunny/crossref_metadata_2025 huggingface dataset:
FLUCTUATION-INDUCED CONDUCTIVITY OF POLYCRYSTALLINE Er1-xTbxBa2Cu3O7-δ SUPERCONDUCTORS
Authors: JURELO ALCIONE ROBERTO , RODRIGUES PEDRO , COSTA ROSÂNGELA MENEGOTTO
Published: May 2009

We have studied fluctuations on the electrical conductivity of granular compounds of Er 1-x Tb x Ba 2 Cu 3 O 7-δ(0 ≤ x ≤ 0.10) superconductors. From the temperature derivative of the resistivity, we have found that the transition proceeds in two intragranular–intergranular stages, with intergranular character accentuated for higher concentrations of terbium (x ≅ 0.10). The data also revealed the occurrence of critical regimes, as well as fluctuation regimes beyond 3D-XY. However, for higher concentrations of terbium, it was not possible to observe fluctuation regimes beyond 3D-XY, probably because TbBa 2 Cu 3 O 7-δ is a metastable phase. Below TC, on approaching the zero resistance state, our results showed a power-law behavior with critical exponents consistent with a phase transition from a paracoherent to a coherent state of the granular array.
DIELECTRIC STUDIES OF SAMARIUM MODIFIED (Pb)(Zr, Ti, Fe, Nb)O3 CERAMIC SYSTEM
Authors: SINGH PRATIBHA , SINGH SANGEETA , JUNEJA J. K. , PRAKASH CHANDRA , RAINA K. K.
Published: May 2009

Here we report the investigations on Sm -substituted PZTFN ( Pb 1-x Sm x Zr 0.588 Ti 0.392 Fe 0.01 Nb 0.01 O 3) (where x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) polycrystalline solid solutions fabricated by solid-state reaction method. XRD analysis shows all the samples to be single phase with tetragonal structure. Dielectric measurements were carried out in the temperature range 30°C–400°C at different frequencies in the range 100 Hz to 100 kHz. From the temperature variation of dielectric constant (ε), Curie temperature (TC) was determined which was found to decrease with increasing x. The room temperature dielectric constant (ε RT ) initially increases with increasing x and then starts decreasing. Dielectric loss improves with Sm -doping.
ACTIVE LATERAL FOOT PLACEMENT FOR 3D STABILIZATION OF A LIMIT CYCLE WALKER PROTOTYPE
Authors: HOBBELEN D. G. E. , WISSE M.
Published: May 2009

This study focuses on the application of active lateral foot placement for 3D stabilization of bipedal walkers. Within the paradigm of "limit cycle walking" foot placement is an important strategy as it can provide cyclic stability for walkers that are locally unstable. Moreover, human gait analysis studies suggest that the stability of human walking depends highly on lateral foot placement. Various simulation studies have already successfully implemented lateral foot placement in walking models, but this study demonstrates that an active lateral foot placement strategy can actually (cyclically) stabilize a physical walking robot that is locally unstable. In order to come to this result, first a study is performed on a simple 3D point mass walking model. This study establishes that, for a model with fixed step length, cyclic stability can already be obtained with a simple linear lateral foot placement strategy that only uses lateral state information (lateral position and velocity) of the center of mass. Moreover, it is found that increasing the walking speed and increasing the ankle roll stiffness enlarges the range of stable feedback gains. With this knowledge of stable feedback gains and parameter sensitivities, the same foot placement strategy is applied to the physical 3D walking prototype called Flame. Similar to the model, this prototype is shown to be unstable without foot placement and stable with the application of the simple, linear lateral foot placement strategy.
GENERALIZATION OF THE DESARGUES THEOREM FOR SPARSE 3D RECONSTRUCTION
Authors: FREMONT VINCENT , CHELLALI RYAD , FONTAINE JEAN-GUY
Published: May 2009

Visual perception for walking machines needs to handle more degrees of freedom than for wheeled robots. For humanoid, four- or six-legged robots, camera motion is 6D instead of 3D or planar motion. Classical 3D reconstruction methods cannot be applied directly, because explicit sensor motion is needed. In this paper, we propose an algorithm for 3D reconstruction of an unstructured environment using motion-free uncalibrated single camera. Computer vision techniques are employed to obtain an incremental geometrical reconstruction of the environment, therefore using vision as a sensor for robot control tasks like navigation, obstacle avoidance, manipulation, tracking, etc. and 3D model acquisition. The main contribution is that the offline 3D reconstruction problem is considered as a point trajectory search through the video stream. The algorithm takes into account the temporal aspect of the sequence of images in order to have an analytical expression of the geometrical locus of the point trajectories through the sequence of images. The approach is a generalization of the Desargues theorem applied to multiple views taken from nearby viewpoints. Experiments on both synthetic and real image sequences show the simplicity and efficiency of the proposed method. This method provides an alternative technical solution easy to use, flexible in the context of robotic applications and can significantly improve the 3D estimation accuracy.
DYNAMIC BALANCE OF HUMANOID SYSTEMS IN REGULAR AND IRREGULAR GAITS: AN EXPANDED INTERPRETATION
Authors: VUKOBRATOVIĆ MIOMIR , BOROVAC BRANISLAV , POTKONJAK VELJKO , JOVANOVIĆ MILOŠ
Published: May 2009

The development of humanoid robotics during the last decades has undoubtedly resulted in numerous successful realizations in this area. One of the most important tasks that have been in the research focus is bipedal walk, which, despite the progress that has been made, has still remained an intriguing research task. The problem is not only how to realize a sustainable walk in an unstructured environment, requiring on-line trajectory planning and changes of gait parameters (turning, stopping, acceleration and deceleration, switching from the walk on a flat ground to the walk on an inclined surface or staircases, etc.), but the gait realization that will allow some additional activities such as, e.g. manipulation tasks. A prerequisite for the fulfillment of such requirements is that the system is dynamically balanced. On the other hand, we are witnesses of the diverse realizations of locomotion systems, from those with human-like feet, aiming to mimic in full the human gait, passive walkers, which practically roll on specially profiled feet, to the footless locomotion systems. It is quite clear that any of these systems can realize a gait, but our present study shows that performances of such walking systems are essentially different. In this sense we consider the minimal conditions for the realization of a dynamically balanced gait, analyze some examples of irregular gaits, and indicate the conditions in which particular phases of such gates are dynamically balanced. We point out the fact that in the presence of disturbances the transition to a dynamically (or even statically) balanced mode of the gait may prevent the system from falling. Besides, it is shown that at the end of the single-support phase of a dynamically balanced gait it is possible to "allow" a temporary, preplanned beforehand, loss of the dynamic balance without jeopardizing the gait realization only if the system has been prepared in advance for such an event. Finally, the work points out the indispensability of the regular, fully dynamically balanced gait for the simultaneous realization of locomotion-manipulation activities, as well as for the walk in an unstructured environment.
BIPED WALKING PATTERN GENERATION USING REINFORCEMENT LEARNING
Authors: LEE JUNGHO , OH JUN HO
Published: May 2009

In this research, a stable biped walking pattern is generated using reinforcement learning. The biped walking pattern is chosen as a simple third order polynomial. To complete it, four boundary conditions are needed. The initial position and velocity and the final position and velocity of the joint are selected as boundary conditions. In order to find the proper boundary condition value, a reinforcement learning algorithm is used. Also desired motion or posture can be achieved using the initial and final positions. The final velocity of the walking pattern is chosen as a learning parameter. To test the algorithm, a simulator that takes into consideration the whole model of the robot and the environment is developed. The algorithm is verified through a simulation.
BUILDING A FRAMEWORK FOR NATIONAL SUSTAINABLE DEVELOPMENT ASSESSMENT AND APPLICATION FOR LITHUANIA: SUSTAINABILITY IN TRANSITION
Authors: MZAVANADZE NORA
Published: May 2009

This study aims to assess the outcomes of the transition period in terms of sustainable development in Lithuania in 1990–2004. The author aims to reveal the synergies and contradictions between the period of transition and the progress to sustainability. The research uses the conceptual framework for assessment of progress towards achieving sustainable development (APASD) for economies in transition (Kobus, 2005). The framework is based on three principles of sustainable development: the principle of carrying capacity, the principle of intergenerational equity and the principle of intragenerational equity. A three-tier system has been formed: each principle has been assigned two operational criteria and a number of sustainable development indicators. Finally, the framework has been applied to Lithuania unveiling the situation of sustainability and providing recommendations for policy response. The transition period has moved the national development closer to sustainability according to the principles of carrying capacity and intergenerational equity; however, it has not been so favourable for the principle of intragenerational equity.
Synthesis and Characterization of LiNi1/3Mn1/3Co1/3O2 by Wet-Chemical Method
Authors: Zhang Xiaoyu , Mauger Alain , Gendron Francois , Qi Lu , Groult Henri , Perrigaud Luc , Julien C. M.
Published: May 2009

A series of LiNi1/3Mn1/3Co1/3O2 samples with α-NaFeO2 structure were synthesized using tartaric acid as a chelating agent by wet chemical method. Different acid to metal-ion ratios R have been used to investigate the effect of this parameter on the physical and electrochemical properties. The cationic mixing (Ni on the 3a Li sites) have been evaluated by Rietveld refinement and magnetic measurements We determined that the LiNi1/3Mn1/3Co1/3O2 sintered at 900 {degree sign}C for 15 h with an acid to metal ion ratio R=2 was the optimum condition for this synthesis. For this optimized sample, only 1.26% of nickel-ions occupied the 3a Wyckoff site of the lithium-ion sublattice. This material delivered an initial discharge capacity of 172 mAh/g and displayed Coulomb efficiency of 94%.
Electrochemical Behavior of Li3-xM1xV2-yM2y(PO4)3 (M1=K, M2=Sc)/C Composite Cathode Material for Lithium-Ion Batteries
Authors: Mateyshina Yulia , Ulihin Artem S. , Uvarov Nikolai F.
Published: May 2009

Composites of monoclinic Li3-xM'xV2-yM"2y(PO4)3 (M'=K, M"=Sc, Mg+Ti) with carbon were synthesized by solid-state reaction using oxalic acid or 10% H2/Ar gas mixture as reducing agents at sintering temperature of 750{degree sign}C. The sample was characterized by X-ray diffraction (XRD), voltammetry and electrochemical galvanostatic cycling. The initial capacity of Li3V2(PO4)3 synthesized using hydrogen as the reducing agent was 127 mAh/g, the samples exhibit good cycling performance.
Ab Initio Study of Lithium Insertion in TiO2-Ramsdellite
Authors: Koudriachova Marina V.
Published: May 2009

Li-intercalation properties of titanium dioxide with the structure of ramsdellite have been studied using density functional calculations. Comparison of calculated energies reveals two domains of Li-intercalation. It has been shown that insertion of up to 0.5 Li/Ti proceeds through a sequence of single phase reactions, while insertion beyond 0.5Li/Ti proceeds through propagation of a stable LiTiO2 orthorhombic phase.
State of Chlorides in Rusts Formed on 3 mass% Ni-added Weathering Steel
Authors: Kimura Masao , Ohta Noriaki , Kihira Hiroshi
Published: May 2009

When weathering steel (WS) is exposed in a coastal atmosphere, rust containing chloride ions is formed. We investigated the state of chloride in rust formed on a new WS with 3 mass% Ni-added WS (NiA-WS), which showed an excellent corrosion resistance even in a coastal atmosphere. It was shown that two types of chloride states exist: (a) a stable one locating in an Fe(O,OH)6-octahedra linkage of rust, and (b) a less stable ionic one adsorbing on the surface of rust. The higher corrosion resistance of NiA-WS can be attributed to the fact that chloride in the inner part of rust is in the state (a) rather than the state (b).
Correlation Studies between Outdoor Exposure and Accelerated Laboratory Corrosion Tests for Galvanic and Non-Galvanic Ceramic-Aluminum Couples
Authors: Srinivasan Raghu , Hihara Lloyd H.
Published: May 2009

Correlation of outdoor exposure corrosion-rate data from a variety of microclimates (i.e., rain forest, alpine, marine, volcanic, industrial, agricultural, and arid) with a series of accelerated laboratory corrosion tests (controlled humidity-chamber and cyclic corrosion test chamber experiments) for both galvanic and non-galvanic ceramic-aluminum (Al) couples were studied. Due to galvanic effects by relatively conductive titanium diboride (TiB2) and boron carbide (B4C) ceramics, high corrosion rates were observed in 6061-T6 Al coupons coupled to these ceramics. Corrosion rates of the 6061-T6 Al coupons in the non-galvanic couples with silicon carbide (SiC), aluminum nitride (AlN), or silicon nitride (Si3N4) were lower. Accelerated laboratory corrosion tests conducted with chloride-containing solutions were aggressive and did not always represent the outdoor exposure results. Hence, the outdoor exposure test data were used to adjust the duration and treatment of the accelerated corrosion tests so that the corrosion damage accumulated in the accelerated tests could better represent the corrosion damage accumulated in the field. Accelerated laboratory corrosion experiments conducted with less aggressive sodium sulfate solution treatments more accurately simulated the outdoor corrosion trends.
Power Density Profile of Biofilm Battery Composed of Stainless Steel Cathode and Aluminum Anode
Authors: Motoda Shin-ichi , Strom Matthew J. , Dexter Stephen C.
Published: May 2009

The measurement of electrochemical characteristics of the biofilm battery composed of a biofilm-covered stainless steel cathode and bare aluminum anode was carried out in natural seawater. From the experimental results, it was found that the durability of the battery was at least 2 hours at 100Ω load, and two peaks in power density of 2.8μW/cm2 around both 0.2 and 0.7V cell voltage appeared. The later peak which did not appear for the bare cathode was considered due to the activity of the biofilm microorganisms.
Issues Associated to Rare Earth Silicide Integration in Ultra Thin FD SOI Schottky Barrier nMOSFETs
Authors: Larrieu Guilhem , Yarekha Dmytro A. , Dubois Emmanuel , Deresmes Dominique , Breil Nicolas , Reckinger Nicolas , Tang Xiaohui , Halimaoui Aomar
Published: May 2009

The paper focuses on specific issues associated to rare earth silicide integration on UTB-SOI substrate with a particular attention to erbium and ytterbium silicides. Due to the limited Si source, defects generation on SOI is prevented compared to bulk substrate. Reaction of RE with dielectric materials limits the temperature of silicidation. It is shown that RE S/D MOSFETs are still limited in current-drive by the Schottky barrier height.
Highly Reliable SRAM Circuit Technology Using FinFETs
Authors: Ouchi Shin-ichi , Endo Kazuhiko , Matsukawa Takashi , Liu Yongxun , Ishikawa Yuki , Tsukada Junichi , Yamauchi Hiromi , Sakamoto Kunihiro , Masahara Meishoku
Published: May 2009

This paper introduces a flex-pass-gate SRAM (Flex-PG SRAM), which is a FinFET-based SRAM to enhance both the read and write margins independently. The flip-flop in the Flex-PG SRAM consists of usual FinFETs, while the pass gates consist of double-"independent"-gate FinFETs, i.e., "four-terminal"- (4T-) FinFETs. By optimizing the current drivability in the 4T-FinFET pass gates according to operational conditions of read and write, both the read and write margins are enhanced. TCAD simulations revealed that the Flex-PG SRAM increases the read margin by 71 mV without the cell size penalty and decrease in the write margin, even when its 6σ tolerance is ensured. Also, a fabricated device proved its feasibility.
The "U" Shape Behavior of GIFBE in Function of Back Gate Bias in FinFETs
Authors: Agopian Paula G. , Martino Joao A. , Simoen Eddy , Claeys Cor
Published: May 2009

In this work the gate induced floating body effect (GIFBE) was analysed in FinFET devices in function of the substrate bias. This analysis was performed in strained and unstrained devices that were fabricated with and without selective epitaxial grow (SEG). For all evaluated devices, this analysis results in a "U" shape behavior of GIFBE onset. Strained devices present earlier GIFBE due to the band gap variation as well as the presence of SEG structure.
Quantization Effect in Capacitance Behavior of Nanoscale Silicon Multigate Mosfets
Authors: Afzalian Aryan , Lee Chi-Woo , Yan Ran , Dehdashti Akhavan Nima , Colinge Cindy , Colinge Jean-Pierre
Published: May 2009

An unusual bump in the gate capacitance characteristics of Si nanoscale MuGFETs is presented and explained here through 3D NEGF quantum simulations. The oscillations in the gate capacitance are shown to be related to the onset of occupation of subbands: due to the particular 1D density of state and through the migration of the charge centroid and quantum confinement. We also present a modeled gate capacitance that allows one to better understand the nature of the oscillation and show that it is mostly due to the variation of the 1D DOS. However, the migration of the charge centroid contributes to a few percents in the total variation of the gate capacitance. Also, the gate/oxide capacitance ratio remains low even at high gate voltage and worsen for decreasing oxide thickness.
Development of Low-Cost Ozone and Nitrogen Dioxide Measurement Instruments Suitable for Use in An Air Quality Monitoring Network
Authors: Williams David E. , Henshaw Geoff , Wells D. B. , Ding George , Wagner John , Wright Bryon , Yung Yu Fai , Akagi Jin , Salmond Jennifer
Published: May 2009

We demonstrate low-cost ozone and nitrogen dioxide measurement instruments suitable for use in an air quality monitoring network. The instruments are based on the gas response of semiconducting oxides at elevated temperature. Although there is a perception that the devices suffer from effects such as drifts of zero and calibration slope, and cross-sensitivities to other gases making them unsuitable for quantitative, long-term atmosphere measurement, we have shown that with careful attention to detail based on a thorough understanding of the mechanisms underpinning device operation, these perceived deficiencies can be overcome. The resultant instruments are small, robust, have sensitivity for O3 and NO2 less than 10 part-per-billion, and track reference analysers in the atmosphere to better than {plus minus}10% over periods of months, without recalibration.
Electrophoretic Integration of Conducting Polymer Nanostructures on MEMS Microsensor Arrays
Authors: Li Guofeng , Benkstein Kurt , Semancik Steve
Published: May 2009

We present a method for preparing colloidal suspension of various conducting polymer nanostructures in order to achieve better processability. The method utilizes the electrostatic repulsion that originates from the inherent positive charges carried on doped conducting polymer backbones for maintaining the stability of these colloidal suspensions. It was further demonstrated that these conducting polymer nanostructures in a colloidal state could be electrophoretically processed onto MEMS microsensor arrays with excellent control and precision.
Application-Specific Micro Gas Chromatographs
Authors: Zellers Edward T. , Kim Sun Kyu , Serrano Gustavo , Chang Hungwei , Bohrer Forest , Veeneman Rebecca , Covington Elizabeth , Kurdak Cagliyan
Published: May 2009

Progress toward the development of prototype microfabricated gas chromatographic instruments (microGC), and components thereof, for applications requiring the determination of trace-level organic vapors in complex mixtures is described. All prototypes use MEMS preconcentration, interconnection, separation, and detection components. Following a brief tribute to Professor Janata, a rationale for incorporating microsensor arrays into microsystems, and a review of key features of the microGC components developed at Michigan in recent years, we present our most recent results. Kinetic factors affecting the capacity of micropreconcentrators are characterized, the reproducibility and thermal stability of wall-coated, etched-Si/glass microcolumns used to separate mixture components are demonstrated, responses from nano-scale chemiresistor arrays with electron-beam patterned nanoparticle interface films are presented, and the design and preliminary test results from two application-specific prototype microGCs are described.
Actively Generated Flow Field Helps a Crayfish Robot Collect Chemical Signals
Authors: Ohashi Mari , Enomoto Satoshi , Ishida Hiroshi
Published: May 2009

This paper reports on an underwater wheeled robot designed to locate chemical sources by mimicking the behavior of a crayfish in still water. Crayfish in search of food generate water currents by waving their fan organs, i.e., the maxillipeds, to collect the food odors from the surroundings to the chemoreceptor organs. Similarly, the robot waves the arms mimicking the maxillipeds, and generates a flow field to collect chemicals to the four sensors. The generated flow field brings chemicals released from different areas to the different sensors. Therefore, the direction of the chemical source can be determined by simply comparing the sensor responses. Although the maximum range for drawing the chemical is approximately 5 cm, the chemical sensing ability of the robot is significantly improved. Experimental results show that the robot can localize a chemical source by employing the actively generated flow field.
Light up the Future of Silicon Microprocessors
Authors: Liu Jifeng , Beals Mark , Michel Jurgen , Kimerling Lionel
Published: May 2009

For decades, the performance of Si microprocessors has increased exponentially following "Moore's Law" by shrinking the dimensions of transistors. However, the progress in microchip performance has become stagnant since 2004 despite the continued device dimension shrinkage mainly due to power consumption and latency issues in traditional electronic interconnects that ended clock frequency scaling. It has become increasingly clear that parallelism is replacing traditional clock frequency scaling, and electronic-photonic synergy that takes the advantage of high bandwidth and energy-efficient photonic interconnects, is the key to high functionality extension of Moore's Law. We present an overview on the recent progress in Si photonic devices and their integration with CMOS fabrication process, including high performance waveguides, couplers, filters, modulators and photodetectors on a Si platform. Photonic data links based on these integrated photonic devices provide large bandwidth and low energy consumption for future generations of microprocessors.
Nanoelectromechanical Logic and Memory Devices
Authors: Akarvardar Kerem , Wong H.-S. Philip
Published: May 2009

Electromechanical relays exhibit inherently zero leakage and sharp hysteresis, which are compelling for logic and memory applications. We present an overview of the nano-scale electromechanical logic and memory devices, investigate their performance, and make a comparison with state-of-the-art logic and memory technologies. We show that nanoelectromechanical logic relays and memory cells can provide significant benefit in terms of operating voltage and energy dissipation -beyond the capability of current technologies- if the technological challenges related to surface adhesion and contact reliability can be overcome.
Ge/GeO2 Interface Control with High Pressure Oxidation for Improving Electrical Characteristics
Authors: Lee Choong Hyun , Tabata Toshiyuki , Nishimura Tomonori , Nagashio Kosuke , Kita Koji , Toriumi Akira
Published: May 2009

We have investigated High Pressure Oxidation (HPO) of Ge for improving Ge/GeO2 interface in terms of GeO desorption control. C-V characteristics in HPO-GeO2 MIS capacitors revealed the dramatic improvement with a very small hysteresis and frequency dispersion. Furthermore, the dielectric constant enhancement in GeO2 grown by HPO was observed. A sub-bandgap photo absorption was observed in GeO2 film grown by Atmospheric Pressure Oxidation (APO), while a sharp absorption edge at ~6 eV, corresponding to the bandgap of GeO2, was seen in the film by HPO. Based on the thermodynamic consideration, the effectiveness of HPO and low temperature oxygen annealing (LOA) in terms of the suppression of GeO desorption is discussed.
The Effect of NH3 on the Interface of HfO2 and Al2O3 Films on GaAs (100) Surfaces
Authors: Suh Dong Chan , Cho Young Dae , Ko Dae-Hong , Chung Kwun Bum , Cho Mann-Ho , Lee Yongshik
Published: May 2009

In this letter, we investigate the effects of heat treatment under NH3 ambient on the Ga-O at the interface between GaAs and high-k dielectric materials deposited by atomic layer deposition (ALD). Compared with the heat treatment results under N2 ambient, the monochromatic x-ray photoelectron spectroscopy (XPS) analysis reveal that the formation of Ga-O is greatly suppressed when under NH3 ambient, both at 500º C and 700º C, for HfO2. However, similar experiments for Al2O3 deposited by atomic layer deposition (ALD) show that the effect of NH3 heat treatment is minimal. We examine the different reaction mechanisms of the nitridation processes for the two different high-k dielectric materials on GaAs. Also, the capacitance-voltage (C-V) properties of metal-insulator-semiconductor capacitors (MISCAP) with Pt electrodes are experimentally examined for various annealing temperatures and ambient conditions.
Electrical and Materials Characterization of Reactive and Co-Sputtered Tantalum Carbide Metal Electrodes for High-K Gate Applications
Authors: Edge Lisa F. , Vo Tuan , Kellock Andrew J. , Linder Barry P. , Bruley John , Zhu Yu , DeHaven Patrick , Paruchuri Vamsi K. , Tsunoda Takaaki , Venkateshan Aarthi , Shinde Sanjay R.
Published: May 2009

In this work, co-sputtered TaC (tantalum + carbon targets + argon) and reactive sputtered TaC (tantalum + methane + argon) were evaluated and compared for application as metal electrodes in high-K/metal gate stacks aimed at 22 nm and beyond technology nodes. The electrical properties of field effect transistors (FETs) were evaluated as a function of TaC deposition conditions and optimized to achieve Tinv scaling. Controlling the deposition conditions as well as the composition of the TaC films was found to be critical to achieve Tinv < 11 Aå.
Low Voltage SILC Analysis for High-k/metal Gate Dielectrics
Authors: Rahim Nilufa , Misra D.
Published: May 2009

Conduction behavior of multi-layer structure of metal/high-k/interfacial layer gate stacks was investigated before and after constant voltage stress. It was found that stress-induced leakage current (SILC) strongly depends on the low sense voltages. Conduction mechanism of the low voltage SILC (LV-SILC) was analyzed systematically with gate stacks of different interfacial layer thicknesses and SiO2-only devices of identical processing condition. Based on the results of defect generation sensed by the LV-SILC, it is observed that discrete levels of trap generation in the interfacial layer primarily causes low voltage SILC in metal/high-k gate stacks and initiates the gate stack breakdown.
Graphene: The Magic of Flat Carbon
Authors: Novoselov Kostya S.
Published: May 2009

Graphene is the first example of a truly two-dimensional crystal. This opens many interesting directions of research concerning the thermodynamics, lattice dynamics, and structural properties of such systems. Being a gapless semiconductor with a linear energy spectrum, single-layer graphene realizes a two-dimensional, massless Dirac fermion system that is of crucial importance for understanding unusual electronic properties, such as an anomalous QHE, absence of the Anderson localization, etc. These peculiarities are important for developing new electronic devices such as carbon transistors. Recent developments in production of large quantities of graphene, as well as the possibility of its chemical modification make such developments very feasible.
Substrate-limited Mobility in Single- and Bi-layer Graphene on Dielectric Materials
Authors: Klekachev Alexander , Cantoro Mirco , Nourbakhsh Amirhasan , Van der Veen Marleen H. , Clemente Francesca , Stesmans Andre L. , Sels Bert , Heyns Marc , De Gendt Stefan
Published: May 2009

We report on the optical and electrical characterization of graphene supported on various dielectric substrates. Graphene single- and bilayer flakes were successfully isolated and Raman spectroscopy was performed to assess their crystalline quality. Temperaturedependent electrical characterization of graphene devices supported on SiO2 and Si3N4 films show the onset of scattering by interfacial phonons and limiting graphene mobility above 200 K.
Controlled III/V Nanowire Growth by Selective-Area Vapour Phase Epitaxy
Authors: Cantoro Mirco , Brammertz Guy , Richard Olivier , Bender Hugo , Clemente Francesca , Leys Marteen , Degroote Stefan , Caymax Matty R. , Heyns Marc , De Gendt Stefan
Published: May 2009

We report on the growth of surface-bound, vertically oriented 1-D III/V nanostructures, specifically GaAs and InAs nanowires, on lattice-matched and -mismatched substrates by selective-area vapour phase epitaxy. Control of nanowire features and growth directions is achieved by tuning of the growth conditions. Grown nanostructures are characterised by scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy.
Monolithic III-V/Si Integration
Authors: Fitzgerald Eugene , Bulsara M. T. , Bai Y. , Cheng C. , Liu W. K. , Lubyshev Dmitri , Fastenau Joel , Wu Y. , Urtega M. , Ha W. , Bergman J. , Briar B. , Drazek C. , Daval Nicolas , Letertre F. , Hoke W. E. , LaRoche J. R. , Herrick K. J. , Kazior T. E.
Published: May 2009

We summarize our work on creating substrate platforms, processes, and devices for the monolithic integration of silicon CMOS circuits with III-V optical and electronic devices. Visible LEDs and InP HBTs have been integrated on silicon materials platforms that lend themselves to process integration within silicon fabrication facilities. We also summarize research on tensile Ge, which could be a high mobility material for III-V MOS, and research on an in-situ MOCVD Al2O3/GaAs process for III-V MOS.
c-erbB-2 Sensing Using AlGaN/GaN High Electron Mobility Transistors For Breast Cancer Detection
Authors: Chen Ke-Hung , Kang Byoung Sam , Wang H. T. , Lele T.P. , Ren F , Wang Y.L. , Chang C.Y. , Pearton Stephen J. , Dennis D. M. , Johnson J. W. , Rajagopal P. , Roberts J.C. , Piner E.L. , Linthicum K.J.
Published: May 2009

Antibody-functionalized, Au-gated AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect c-erbB-2, a breast cancer marker. The antibody was anchored to the gate area through immobilized thioglycolic acid. The AlGaN/GaN HEMT drain-source current showed a rapid response of less than 5 seconds when target c-erbB-2 antigen in a buffer at clinically relevant concentrations was added to the antibody-immobilized surface. We could detect a range of concentrations from to 16.7 μg/ml to 0.25 μg/ml. These results clearly demonstrate the promise of portable electronic biological sensors based on AlGaN/GaN HEMTs for breast cancer screening.
Electrical Performance of Gate-recessed AlGaN/GaN MOS-HEMTs Fabricated using Photoelectrochemical Method
Authors: Chiou Ya-Lan , Shiau Nan-Teng , Huang Li-Hsien , Lou Li-Ren , Lee Ching-Ting
Published: May 2009

Gate-recessed AlGaN/GaN MOS-HEMTs were fabricated using a photoelectrochemical (PEC) method to form the recessed structure and to directly grow gate insulator on the recessed surface. The resulting devices exhibited better performances than conventional one without gate recess, including a saturation drain-source current of 642 mA/mm, and an off-state breakdown voltage larger than -100V. The normalized noise power spectra of both kinds of devices at the saturation region were well-fitted by the 1/f law and the Hooge's coefficient α in both devices was about 10−4, demonstrating that PEC wet etching is an effective way to achieve a damage-free surface and to improve the DC characteristics of the MOS-HEMTs.
Real-time Detection of Botulinum Toxin with AlGaN/GaN High Electron Mobility Transistors
Authors: Wang Yu-Lin , Chu Byung Hwan , Chen Ke-Hung , Chang C.Y. , Lele T.P. , Tseng Y. , Pearton Stephen J. , Ramage J. , Hooten D. , Dabiran A. , Chow P.P. , Ren F
Published: May 2009

AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect botulinum toxin. The gate area was deposited with Au and thioglycolic acid. The antibody was anchored on the gate area. The AlGaN/GaN HEMT drain-source current showed a rapid response of less than 5 seconds when the target toxin in a buffer was added to the antibody-immobilized surface. Different concentrations (from 0.1 ng/ml to 100 ng/ml) of the exposed target botulinum toxin in a buffer solution were detected. The sensor showed low detection limit of less than 1ng/ml and saturates above 10ng/ml of the toxin. The sensor was recycled with the phosphate buffered saline (PBS) after the toxin detection and still showed the same sensitivity.
Luminescent Properties of M-Al2O4:Eu2+ (M: Ca, Sr) Thin Films Prepared on Sapphire Substrates
Authors: Lee Jun Seong , Lee Choong Ki , Kim Young Jin
Published: May 2009

M-Al2O4:Eu2+ (M: Ca, Sr) thin films were deposited on c-plane sapphire substrates by rf magnetron sputtering, and growing behaviors and luminescent properties were investigated. As-deposited films were amorphous-like, but they were transformed to the epitaxial films by annealing at high temperatures. The epitaxial orientations and growing behaviors of CaAl2O4 and SrAl2O4 films were different each other due to the crystallographic distinction. PL spectra exhibited a blue and a green emission for CaAl2O4:Eu2+ and SrAl2O4:Eu2+, respectively.
Electrochemical Growth of CuInSe2 Compounds on Polycrystalline Mo Films Studied by Raman and Impedance Spectroscopy
Authors: Chassaing Elisabeth , Grand Pierre-Philippe , Saucedo Edgardo , Etcheberry Arnaud , Lincot Daniel
Published: May 2009

The growth process of Cu-In-Se compounds was investigated by in-situ electrochemical techniques and ex-situ XPS and Raman spectroscopy. The growth can be divided in three well separated steps. In a first stage, the Cu concentration is high, leading to the formation of a Cu-rich binary phase, Cu2Se, which acts as a precursor for Se(IV) reduction into elemental Se(0). When the surface concentration of elemental Se(0) is high enough, a new surface phase is formed with a stoichiometry close to CuSe2. It acts as a catalytic site for indium incorporation. This results in the formation of CuInSe2 and Cu-poor chalcopyrite phases. The proportions of the different phases evolve during the growth. This complex mechanism is in agreement with the compositional, structural and electrical properties of the samples as a function of the thickness.
In Situ Infrared Kinetic Study of Multistep Chemical Modifications of Organic Monolayers at Silicon Surfaces
Authors: Touahir Larbi , Moraillon Anne , Sam Sabrina , Gouget-Laemmel Anne Chantal , Allongue Philippe , Chazalviel Jean-Noël , Henry de Villeneuve Catherine , Ozanam Francois
Published: May 2009

The reaction of activation of acid-terminated organic monolayers grafted on (111)Si surfaces into succinimidyl-ester terminated monolayers by treatment in N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) has been studied by infrared spectroscopy and its kinetics have been followed in situ. The reaction exhibits non exponential kinetics, with an initial fast rise in the appearance of succinimidyl ester followed by a long reaction tail. The origin of this behavior can be ascribed either to the existence of a fast reaction pathway involving anhydride formation, or to the rate limitation by steric hindrance effects. The subsequent amidation of the succinimidyl ester layers by a primary amine has been studied similarly. Here, the kinetics are found to be exponential, but the reaction rate exhibits a sublinear dependence on the amine concentration. This behavior is ascribed to the effects of electrostatic interactions on the adsorption of the protonated amine onto the Si surface prior to reaction.
Effects of "P-N" Terminations on the Initial Stages of Pore Growth onto n-InP in HCl Aqueous Solution
Authors: Goncalves Anne-Marie , Santinacci Lionel , Simon Nathalie , Bouttemy Muriel , Mathieu Charles , Etcheberry Arnaud
Published: May 2009

In this paper we report, for the first time, a galvanostatic control in 1M HCl aqueous solution onto a InP surface that had been previously entirely nitrogenated. The surface nitrogenation required an anodic electrochemical treatment in acidic liquid ammonia (NH3 liq.). An homogeneous covering film with " P-N " terminations was obtained onto the InP surface properly deoxidized. This thin film is notable for its lack of air ageing and also for its chemical stability in HCl. A galvanostatic control at different current density (10 mA.cm-2, 100mA.cm-2 and 300 mA.cm-2) in 1M HCl was used to identify the effect of this " P-N " terminations on the porosification process. In comparison to a bare surface, a contrasted evolution of the interfacial potential was clearly observed for low current density. As expected, a crystal oriented pore morphology (CO) is obtained onto a bare InP surface whereas "oscillating" current line oriented pore morphology (CLO) is kept onto a surface entirely recovered by a " P-N " film. The presence of the nitrogenated film can therefore be significant on the pore growth evolution in 1M HCl aqueous solution.
Unexpected Dissolution Process at Porous n-InP Electrodes
Authors: Santinacci Lionel , Bouttemy Muriel , Gerard Isabelle , Etcheberry Arnaud
Published: May 2009

In this paper, we report an unexpected dissolution phenomenon at n-InP electrodes during porous etchiong in 1M HCl under potentiostatic consitions (5V vs. Ag/AgCl). Although the scanning electron microscope examinations show the typical tubular and regular pores that exhibit a depth proportional to the anodic charge, further chemical analyses of the dissolved material performed after the pores formation by atomic absorption spectroscopy reveal a dual dissolution process. An electrochemical etching process exhibiting a valence of 8 is evidenced. Howeverit is surprisingly coupled to a chemical dissolution that correspnds to the half the dissolved InP.
Growth Mode Transition of Crysto and Curro Pores in III-V Semiconductors
Authors: Föll Helmut , Leisner Malte , Carstensen Jürgen , Schauer Patrick
Published: May 2009

The formation of crystallographically oriented and current line oriented pores in n-type InP is reviewed and compared to other semiconductors in the light of some new results. A model for the formation of crystallographically oriented pores is presented that reproduced salient features of this pore type rather well. Impedance data together with their model-based evaluation are given and discussed. Some self-organization features of current line oriented pores and their possible relation to self-induced or externally triggered growth mode transitions between the two pore types conclude the paper.
Phase-Relations between Photocurrent and In Situ Reflectance during Photoelectrochemical Dissolution of Silicon
Authors: Lublow Michael , Lewerenz H. J.
Published: May 2009

The phase relation between local maxima of photocurrents and those of in-situ Brewster-angle reflectance (BAR) is investigated upon dissolution of silicon photoelectrodes in diluted NH4F. In the region of photocurrent oscillations, charge flow and optical response can be related by a linear equation which explains the observed positive phase shift of the reflectance. In the transition regime, between porous silicon formation and electropolishing, commencing surface oxidation results in a negative phase shift of the reflectance. It is shown that this observation points to a change in the dissolution mechanism of the surface-near region. A step-function, convoluted with the charge flow, is applied to model the optical behavior. This approach is compared to optical multi-layer analysis in which simultaneously increasing sub-surface porosity and surface roughness are considered.
UV-Raman Spectroscopy Study on SiO2/Si Interface
Authors: Hattori Maki , Yoshida Tetsuya , Kosemura Daisuke , Ogura Atsushi , Suwa Tomoyuki , Teramoto Akinobu , Hattori Takeo , Ohmi Tadahiro
Published: May 2009

We evaluated oxidation-induced stresses in Si crystal and qualities of Si crystal near the SiO2/Si interfaces formed in dry O2 and O radicals using UV-Raman spectroscopy with a 364 nm excitation laser. The compressive stresses were observed in Si near the SiO2/Si interfaces formed in dry O2 and O radicals. The stresses induced by the oxidation at 1050oC were higher than those at 900oC and 1000oC. It was also shown that the stress in Si crystal and the quality of Si crystal near the SiO2/Si interface formed in dry O2 depended on the degree of oxygen dilution and the oxidation time. The SiO2/Si interface formed in O radicals exhibited larger compressive stress and better crystal quality as compared with that formed in dry O2.
Material Dependence of Negative Bias Temperature Instability (NBTI) Stress and Recovery in SiON p-MOSFETs
Authors: Mahapatra Souvik , Maheta Vrajesh , Deora Shweta , Kumar E. N. , Purawat Shweta , Olsen Chris , Ahmed Khaled , Islam Ahmed , Alam M. A.
Published: May 2009

Negative Bias Temperature Instability (NBTI) is studied in Silicon Oxynitride (SiON) p-MOSFETs using a recently developed Ultra-Fast On-The-Fly linear drain current method. It is shown that both stress and recovery phases of NBTI are strongly influenced by SiON gate insulator process. Gate insulator nitrogen spatial distribution is shown to impact interface trap generation (NIT) and hole trapping (Nh) components of overall threshold voltage shift (VT). A simple, self consistent method is proposed to isolate NIT and Nh. It is shown that the time dynamics of stress and recovery phases are strongly correlated, at short time governed by trapping and detrapping of holes, and at long time by generation and passivation of interface traps.
Impact of Film Stress on Nanoidentation Fracture Toughness Measurements for PECVD SiNx:H Films
Authors: King Sean , Chu R. , Xu Jessica , Huening Jennifer
Published: May 2009

The apparent fracture toughness for a series of plasma enhanced chemical vapor deposition SiNx:H films with film stress skewed from 300 MPa tensile to 1 GPa compressive were measured using nanoindentation. The nanoindentation results show the measured fracture toughness for these films is a linear function of the intrinsic film stress and can cause the fracture toughness to vary from as high as > 8 MPa⋅√m for compressive films to as low as < 0.5 MPa⋅√m for tensile films. Other film properties such as density and modulus were also measured and not observed to correlate strongly with the measured fracture toughness values. Based on these results, we propose a simple method for adjusting the apparent fracture toughness measured by nanoindentation experiments to the actual intrinsic fracture toughness of the material.
Comparison of Interlevel Dielectric Processes Using PECVD Silicon Nitride, Polyimide, and Polybenzoxazole for GaAs HBT Technology
Authors: Yota Jiro
Published: May 2009

In this study, we have evaluated several interlevel dielectric materials for GaAs hetero-junction bipolar transistor (HBT) technology. This technology requires the material to have good gapfill and planarizing characteristics, as the various device and interconnect structures can have significant topography. Additionally, the process typically can only have a maximum temperature of <300oC, as device degradation can occur at higher temperatures. The dielectric materials evaluated are PECVD silicon nitride (Si3N4), polyimide, and photodefinable polybenzoxazole (PBO). The PECVD Si3N4 is mostly conformal when deposited. However, it has a high dielectric constant, cannot be used as gapfill material, and does not planarize the underlying topography, which makes multilevel metallization challenging. Polyimide and PBO, both of which need to be thermally cured, have lower dielectric constant than PECVD Si3N4. However, the polyimide has to be dry-etched, unlike the photosensitive PBO. Furthermore, the PBO has better gapfill and planarization capabilities than polyimide.
T-x-y Computer Models with SiC and SiO2
Authors: Lutsyk Vasily I. , Vorob'eva Vera P. , Zelenaya Anna E.
Published: May 2009

Method to design the computer models of T-x-y diagrams with SiC and SiO2 by means of kinematical surfaces has been considered. Templates for computer models of three Т-х-у diagrams are analyzed: 1) with the liquidus field of low-temperature polymorphous modification; 2) with the invariant 4-phase transformation of monotectic type; 3) with the liquidus surfaces of two modifications of component B and an invariant monotectic reaction of two immiscible liquids with solid phases C and A.
Time Evolution of Resistance Drift of Magnetic Tunnel Junctions with Ultrathin AlOx Films
Authors: Nakano Shinsuke , Taguchi Sho , Kamakura Yoshinari , Taniguchi Kenji
Published: May 2009

The degradation of magnetic tunnel junctions (MTJs) with AlOx barrier is investigated experimentally. Time evolution of current through MTJ during constant voltage stress is monitored under various stress conditions. We particularly focus on the degradation behavior, such as the power law exponent for the time evolution characteristics and degradation recovery phenomenon after the CVS interruption. The strong dependence on the stress bias polarity is observed, but we show that the common characteristics are confirmed in the data stressed under positive and negative bias stresses.
Dielectric Response of Ta2O5, NbTaO5 and Nb2O5 from First-Principles Investigations
Authors: Clima Sergiu , Pourtois Geoffrey , Van Elshocht Sven , De Gendt Stefan , Heyns Marc M. , Wouters Dirk J. , Kittl Jorge A.
Published: May 2009

High-κ dielectrics are intensively investigated as a replacement for SiO2 in integrated nanoelectronics. Ta and Nb based oxides are among the list of interesting candidates that display a relatively large dielectric constant with a band gap larger than 3 eV. In this paper, we show that it is possible to modulate the dielectric response of the Ta2O5 by admixing it with Nb2O5. The dynamical charges and dielectric constants of Ta2O5 and of Nb2O5 were calculated at the Density Functional Theory (DFT) level for different crystal phases. The averaged dielectric constants range between 27(38) and 42(77) for Ta2O5 (Nb2O5) in the hexagonal and orthorhombic varieties. Interestingly, a mixed NbTaO5 composition exhibits a directionally averaged dielectric constant of 54 and a relatively large band gap, close to the arithmetic mean value of the binary species. The origins of the dielectric permeability are discussed and confronted to experimental measurements.