bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Microencapsulated Laccase as Enzyme Immobilization Template for Application in Bio-fuel Cell
Authors: Hébert Mathieu , Rochefort Dominic
Published: October 2008

The electrochemical behavior of microencapsulated laccase with a non-conductive polymer (poly(ethyleneimine), PEI) adsorbed on a glassy carbon electrode (GC) had been investigated. A Km value of 76 μM and a sensitivity of 16.6 {plus minus} 0.1 nA/μM with a response time of 7.5 s had been determined for a laccase microencapsulated with PEI that was deposited on a bare GC electrode in a McIlvaine buffer at pH = 5.75 with p-phenylenediamine (PPD). The bioelectrode has found to have a permeability, Pm, of 4.9 E-4 cm s^-1 for PPD and too strong interactions with 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonate) acid to observe any diffusion processes. The electrochemical and enzymatic oxidation of PPD was studied under various conditions to evaluate its reversibility and stability as a suitable redox mediator. RDE experiments showed a passivation for a glassy carbon electrode modified with empty poly(ethyleneimine) microcapsules under static conditions. Under hydrodynamic conditions however, the passivation was slowed down.
A Flexible and Wearable Biosensor for Continuous Glucose Monitoring on Eye Site
Authors: Kudo Hiroyuki , Iguchi Shigehito , Miyajima Kumiko , Saito Hirokazu , Mitsubayashi Kohji
Published: October 2008

A flexible electro-enzymatic glucose sensor using functional polymers was constructed and tested. The novelty of our biosensor is that the sensor itself is flexible and suitable for biomonitoring on eye sites. The biosensor consists of film electrode formed on a flexible gas-permeable polypropylene membrane and a non-permeable membrane. A membrane filter containing electrolytic solution was packed between the electrodes and the non-peameable membrane. Enzyme immobilized membrane was formed on the sensing region. Characterization of the flexible biosensor was also carried out. The flexible biosensor showed linear characteristics and utilized for biomonitoring on eye site. According to the result, the sensor was useful to measure kinetics of tear secretion.
Photothermal Spectroscopy using Microfabricated Cantilever Sensors
Authors: Thundat Thomas G. , Senesac Larry R. , Van Neste Charles , Krause Adam , Finot Eric
Published: October 2008

Microcantilever sensors offer high sensitivity for chemical vapor detection. However, microcantilever sensors suffer from poor selectivity due to the lack of sufficiently selective coatings. We show that combining the selectivity of photothermal spectroscopy with the high sensitivity of a bimaterial cantilever produces a platform for developing photothermal spectroscopy of adsorbed molecules. Here we discuss the high selectivity that can be achieved for explosives adsorbed on a microcantilever surface.
Microcantilever with Carboxyl-Functionalization for Mercury Ion Detection
Authors: Chou Yen-I , Tseng Wei-Shun , Wu Cheng-Yen , Lee Thomas Ming-Hung , Lai Shih-Ming
Published: October 2008

Microcantilevers with surface functionalizations have provided the possibility of mechanical transductions for chemical detections. In this work, the 15-mercaptopentadecanoic acid (HS(CH2)14COOH) was functionalized onto the Au-coated microcantilever for mercury ion detection. Experimental results revealed that the HS(CH2)14COOH-functionalized microcantilever exhibited the excellent sensing characteristics with a low detection limit of 10-10 M, a wide detectable regime of 4 orders of mercury concentration, and a good sensitivity within 1 hr.
Development of Self-contained Microelectrochemical Array Assays for Whole Organisms
Authors: Aguilar Z. , Sirisena Mali , Gertsch Jana , Pacsial-Ong Eden , Narasimhan Padhmodhbhava Y. , Wansapura Chamika , Kuzmicheva Galina , Henrichs Andrea , Aday Julie , Norman Mya , Aguilar Ysmael , Estorninos Leo
Published: October 2008

We report the results of our preliminary studies toward the development of assays for the detection of whole organism using a 1cm2 Au-coated silicon wafer chip for capture. Signal generation involved a VEG4x1{trade mark, serif} chip that contains an array of 16-picoliter geometric volume microwells with self-contained electrochemistry. The 50-μm diameter microwells contain a gold disk electrode at the bottom that serves to seal one end of the well, a 50 nm thick gold electrode embedded along its wall and the top gold layer that also serves as the rim of the well. The self-contained microelectrochemical cell-nature of the microcavity needs only very small volume for signal generation. Initial research on the application of our technology for the detection of C. parvum, G. lamblia, E. coli and B. globigii spores are discussed.
Microfabricated Magnetoelastic Biosensors for the Detection of Bacillus Anthracis Spores
Authors: Li Suiqiong , Johnson Michael , Wan Jiehui , Petrenko Valery , Chin Bryan A.
Published: October 2008

Phage based magnetoelastic biosensors for wireless detection of Bacillus anthracis spores were fabricated. The biosensor is composed of a magnetoelastic resonator platform, and JRB7 phage, a genetically engineered bacteriophage that specifically binds with Bacillus anthracis spores, as the bio-molecular recognition element. The phage was engineered at Auburn University and immobilized onto all surfaces of the sensors. To achieve high sensitivity, micro-scale magnetoelastic particle sensor platforms were manufactured using microelectronics fabrication techniques. Real-time in liquid tests were conducted to determine the sensitivity and detection limit of the biosensors by exposing the biosensors to static solutions containing known concentrations of spores. Experimental results showed that the biosensor has a detection limit of approximately 100 spores per ml of liquid and sensitivity of 13 KHz per decade for the detection of Bacillus anthracis spores. Additionally, the phage based biosensors showed high binding affinity and specificity, and superior stability compared with antibody based biosensors.
Sensors for Environmental Compliance of Diesel Engines
Authors: Zemskova Svetlana M. , Habeger Craig F. , Paulson Tom E. , Wimmer Eric , Mavromaras Alexander , Kolmakov Andrei
Published: October 2008

Nitrogen oxides generated from the combustion of fossil fuels contribute to ground level ozone formation and acid rain deposition. To minimize emissions the robust sensor technologies required. Solid-state electrochemical NOx and NH3 sensors evaluated in this study showed significant cross-interference issues. In contrast, the semiconductor nanowires of Cu and Pb Pthtalocyanine and CdS thin films functionalized with Fe and Mn Porphyrines (Ph) exhibited negligible cross-interferences. The computational molecular modeling was utilized to analyze equilibrium structures and binding energies of O2, CO, NO, NH3, and these were shown to control the selectivity. The FePh exhibited the highest selectivity for NO (-190 kJ/mol), while MnPh was most selective to NH3 (-46.7 kJ/mol). The binding energies of gas molecules to the hybrid Ph-CdS system were approximately 30 kJ/mol greater than binding to the Ph alone. Therefore, the semiconductor surface buried under the Ph layer enhanced sensitivity, but it did not alter the selectivity.
A New Solid Electrolyte Type Ammonia Gas Sensor Applying Praseodymium Ammonium Sulfate Based Auxiliary Sensing Electrode
Authors: Nagai Tsukasa , Tamura Shinji , Imanaka Nobuhito
Published: October 2008

A new solid electrolyte type ammonia gas sensor was fabricated by combining the trivalent aluminum cation conducting (Al0.2Zr0.8)20/19Nb(PO4)3 solid electrolyte and the praseodymium ammonium sulfate Pr2(SO4)3•(NH4)2SO4 auxiliary sensing electrode. Since the present sensor showed such a superior sensing performance of quantitative, continuous, and reproducible response with obeying the theoretical Nernst relationship, it is expected to be a practical NH3 gas sensor.
Hydrogen Gas Sensor using Nano-sized R-MnO2 Powder
Authors: Ueda Yoshikatsu , Tsujimoto Masahiko , Takeuchi Ken , Koyanaka Hideki , Takano Mikio
Published: October 2008

Nano-powder of R-type manganese dioxide (RMO) was used for a hydrogen gas sensor. We prepared a pellet (diameter: 2 cm, thickness: 0.5mm) of RMO, and set it in between a couple of Pt mesh sheets to make a SOFC cell. The cell showed a maximum output voltage of 0.3V with good response to hydrogen gas supplied at room temperature. We measured the variation of the output voltage by using different concentration of hydrogen gas (0.1- 99.9 %) and their flow rate (10- 100 ml/min). Furthermore, other crystal structure types of manganese dioxide were tested for comparison. Consequently, only RMO showed good suitability as a hydrogen gas sensor, usable over a wide range of hydrogen gas concentrations.
H2S Sensing Properties and Mechanism of Macroporous Semiconductor Sensors
Authors: Hyodo Takeo , Nonaka Shuhei , Shimizu Yasuhiro , Egashira Makoto
Published: October 2008

Macroporous (mp-) In2O3-based films with and without 1 wt% CuO loading were fabricated by a modified sol-gel technique employing polymethylmethacrylate microspheres as a template and their sensor responses to H2S and the reaction behavior of H2S over the sensor materials were investigated. Introduction of macropores into an In2O3 film and simultaneous loading of CuO on the In2O3 surface were enormously effective in improving the H2S response. The large surface area of mp-In2O3 loaded with CuO, which increased the reactivity of CuO with H2S, is probably the most important factor to enhance the H2S response.
Agricultural Ammonia Monitoring Technology
Authors: Carter M. , Faull John , Trimboli Joseph , Pierce Michael
Published: October 2008

We report on development of ammonia monitoring technology for confine animal feeding operations (CAFOs). The atmosphere within a CAFO is typically hot with high humidity and often considerable concentrations of ammonia. High levels of particulates are often also present. These conditions present a challenge to conventional ammonia monitoring technologies. Here, we discuss our recent progress on development of a fast, sensitive and robust colorimetric approach for ammonia in this challenging environment.
Enhanced Ammonia (NH3) Sensing Response of UV-Light Treated Organic Thin-Film Transistors(OTFTs)
Authors: Zan Hsiao-Wen , Tsai Wu Wei , Wu Yu-Mei , Yen Kuo-His , Lo Yen-Ren , Yang Yuh-Shyong
Published: October 2008

Pentacene thin-film transistors have great potential because of low cost, large-area circuits, and relatively high mobility. Due to active organic layers, OTFTs have suitable analyte response properties with high sensitivity in both gaseous(1) and aqueous(2) environments. Gas sensing mechanisms for OTFTs have been proposed that gas molecules interact with carriers in conduction channels at the dielectric interface. To increase the sensing ability and to establish sensing selectivity, many approaches have been proposed such as using OTFTs as multi-parameter sensors(3), changing the functional group or grain structure of the organic layer(4), and varying the device dimension(5). In our paper, a new method to increase the sensing sensitivity was demonstrated. The OTFTs sensitivity to ammonia can be successfully enhanced by the functional group on the dielectric. Sensing selectivity can be expected by comparing OTFTs with different functional group on the dielectric in our film.
Porous Silicon Gas Sensors for Room Temperature Detection of Ammonia and Phosphine
Authors: Ozdemir Serdar , Gole James L.
Published: October 2008

Nanopore covered microporous porous silicon (PS) interfaces have been formed to provide an active scaffolding for the creation of rapidly responding, reversible, and sensitive, (< 1ppm) PS gas sensors, operating at room temperature, and based on a uniquely formed highly efficient electrical contract to the nanopore covered microporous array. These sensors are modified on the basis of a general acid-base theory, introducing active nanoparticles to establish gas selectivity. NH3 and PH3 have been monitored well below the ppm level.
Development of High-sensitive Gas-sensor for B2H6 using Gas-permeable Conductive DLC Membrane
Authors: Tanaka Yoriko , Furata Masahiro , Mastuura Hiroaki , Nakano Nobuo , Fujishima Akira , Honda Kensuke
Published: October 2008

The gas-permeable DLC membrane was fabricated by nitrogen-doped DLC coating on the surface of the porous membrane. The application of conductive DLC membrane for the selective gas sensor was examined. The DLC sensor could selectively detect B2H6 among four toxic gases (PH3, AsH3, B2H6, SiH4) that were commonly used in the factory of the semiconductor materials. The response currents for B2H6 show the linear relation between 0.05 ppm to 0.5ppm of B2H6, and the low detection limit for the B2H6 detection was found to be 0.025 ppm at S/N = 3. The response speed of the DLC gas sensor was quite high. Therefore, it can be concluded that the gas-permeable N-doped DLC membrane is the promising electrode materials that can realize the selective B2H6 gas sensor.
Stability of Oxime Based Microsensor for Organo-Phosphate Vapor Detection
Authors: Londono Nicolas J. , Oh Ilwhan , Masel Richard I.
Published: October 2008

The purpose of this research was to develop a liquid medium in which the oxime would remain stable, while still being able to function as intented in the microsensor. Oxime solutions in pure organic solvents show no noticeable degradation and on average, had ~450 times greater solubility than the original aqueous buffer. However, the reaction between oxime and organo-phosphate requires hydroxide ions. As a result, pure organic solvents will not be compatible with the microsensor electrochemistry. To avoid the oxime degradation a concentrated organic oxime solution will be combined with the basic aqueous buffer just prior to being used in the detection process. Ethanol was chosen as the best organic solvent due to its stabilizing effect on the oxime and minimal interference with the aqueous electrochemistry. The sensor response utilizing the integrated micromixer was nearly identical to the response when the solutions were premixed and fed at the same rate.
Tunneling Junctions as Molecular Sensors
Authors: Prokopuk Nicholas , Son Kyung-Ah
Published: October 2008

Electron tunneling between nanospaced electrodes provides a mechanism for directly transducing the presence of molecular analytes into electrical signals. Crossbar junctions with vertical separations on the order of a few nanometers were fabricated using a combination of electron-beam lithography and selective chemical etching. The current-voltage properties of the nanojunctions are highly sensitive to the chemical environment. The tunneling currents increase over one order of magnitude in response to water vapor diluted with a background of pure nitrogen. The resistance of the junctions is also dependent on the concentration of the analyte. These results demonstrate that tunneling can be used to detect changes in the chemical environment.
Resonances of Soft Films under Liquid on the QCM
Authors: Kanazawa Kay K. , Frank Curt , Hardesty Joseph
Published: October 2008

Recent advances have made possible using the QCM, not only the mass of the deposit but also its mechanical properties. Unusual behaviors can be attributed to instrumental failures. Soft films under liquid have been shown to exhibit quite unexpected frequency changes and dissipative changes. We show that the behaviors, though unexpected, are rooted in the interaction between the film and liquid. This instrumental data can still be used to determine mass changes and property changes.
Long-term Stability of Oxygen Sensitive Membrane using Ruthenium Complex for Corrosion Monitoring of Radioactive-waste Repository
Authors: Nakamura Yuki , Koshiba Yusuke , Ito Daisuke , Yokoyama Takashi , Okazaki Shinji , Nakagawa Hidemoto , Arai Takashi
Published: October 2008

In order to monitor corrosion risk of radioactive-waste repository, a fiber-optic oxygen sensor for long-term use was proposed and its durability at high temperature was evaluated. The sensing mecha-nism is based on quenching of luminescence by oxygen. Many kinds of Ruthenium complexes which have different counter-anion and ligand were utilized as oxygen-sensitive dye. Several Ru-complexes were dispersed into silicone resin. Excitation is achieved with a blue LED (470 nm) and the emitted light at around 610 nm is collected by optical fiber. The sensing membranes showed high sensitivity and quick response to gaseous and dis-solved oxygen. Comparison of sensitivity and durability of the Ru-complexes were performed. Degradation behaviors of the sensors in air at 150 ºC were investigated. Also short-term degradation test in hot water (80 ºC) was conducted. Screening of the sensors is un-derway to find the most stable sensor in such environment by this test.
Discontinuous Palladium Nanostructures for H2 Sensing
Authors: Fournier Claire , Kiefer Thomas , Villanueva Guillermo , Fargier Frédéric , Penner Reginald , Brugger Juergen , Favier Frédéric
Published: October 2008

Various top-down, bottom-up, and hybrid fabrication routes of discontinuous palladium nano and mesostructures can be used for the fabrication of resistor based H2 sensing devices. 1D, 2D, and 3D structures can be achieved using appropriate material templating and self-organization methods. Sensing mechanism is based on reversible gap closing/opening under H2/H2-free atmospheres undergoing the conversion equilibrium between Pd and PdH0.7. Sensing performances depend on device designs and material microstructures and assembling/organizations.
High Sensitivity Electrochemical Detection of Hydrogen Peroxide at a Cobalt Phthalocyanine-Modified Boron-Doped Diamond Electrode
Authors: Kondo Takeshi , Tamura Akira , Fujishima Akira , Kawai Takeshi
Published: October 2008

A cobalt phthalocyanine-modified boron-doped diamond (CoPc-BDD) electrode was fabricated. The hydrogen-terminated BDD electrode surface was terminated with the pyridine moieties via photochemical modification with 4-vinylpyridine (4VP), followed by immobilization of CoPc on the surface by immersion of the 4VP-BDD samples in a CoPc solution. X-ray photoelectron spectroscopy studies suggested that coordination of the surface pyridine to the Co atom in CoPc contributes to the surface modification. Electrochemical detection of hydrogen peroxide at the modified electrode was also investigated. Cyclic voltammetry confirmed that the CoPc-BDD electrode exhibits catalytic activity for the electrochemical oxidation of H2O2. Using a flow-injection analysis-electrochemical detection (FIA-EC) system, CoPc-BDD electrode was estimated as being highly suitable for the detection of H2O2 with a practical detection limit in the order of several tens of nanomolars.
Nano Gold / Phytic Acid Layer-by-layer Assembly for Fabrication of Horseradish Peroxidase Biosensor
Authors: Ma Xiaoling , Zheng Yaqin , Duan Guoping , Zhang Zongrang , Yang Haifeng
Published: October 2008

We attempted to introduce phytic acid as a binder to construct the controllable structure. Phytic acid and Au NPs were assembled by layer-by-layer onto the surface of gold electrode to forming the three-dimensional mesoporous Au interface. And then high sensitive HRP biosensor was prepared based on the proposed mesoporous interface. Surface Enhanced Raman Scattering and electrochemical impedance are applied to characterizing the process of forming nano film. The resulting biosensor responses to H2O2 were linearly proportional to the concentrations from 2.5×10-5 ~1.0×10-4 mol L-1as well as 1×10-4 ~ 4×10-3 mol L-1 with a detection limit of 8.6×10-6 mol L-1 (S/N = 3).
Self-Assembled Monolayers of Non-Heme Diiron Model Complexes: Binding and Activating Dioxygen on a Gold Electrode Surface
Authors: Inomata Tomohiko , Hayashi Yuya , Shinozaki Kazuma , Funahashi Yasuhiro , Ozawa Tomohiro , Masuda Hideki
Published: October 2008

The self-assembled monolayers (SAMs) of dinuclear Fe complexes with the dinucleating ligand were prepared. Although these types of dinuclear Fe complexes were able to bind dioxygen in non-aqueous solution at low temperature (-30 ºC), the SAMs of these diiron complexes indicated the dioxygen-binding ability in aqueous solution at room temperature. These dinuclear Fe complexes were very stable by the modification onto Au electrode surfaces. Furthermore, the SAMs showed the reversible binding/releasing to dioxygen in aqueous media and the electrocatalytic activation of the binding dioxygen.
Experimental and Theoretical Studies for Optimization of Polythiophene Gas Sensor Arrays
Authors: Liao Frank , Subramanian Vivek
Published: October 2008

Polythiophene-based organic transistors are excellent candidates for gas sensor arrays in electronic nose applications, but there has not yet been a thorough understanding of the relevant factors that contribute to the sensing response. Experimental and theoretical investigation of polythiophenes show that relevant factors include: the functional group of the polythiophene side-chain, the length of the side chain, the functional group of the analyte, and the length of the analyte. Side-chains on the polythiophene can enhance discrimination of the analyte, while analyte functional groups are largely responsible in determining the sensitivity of the sensor response. Theoretical density functional theory (DFT) calculations show that the analyte polythiophene interaction is energetically favorable with energetic differences between different analytes.
Fabrication of Bisphenol A Sensor Utilizing Electrode Modified with Molecularly Imprinted Polymer
Authors: Yokota Nobuyuki , Fuchiwaki Yusuke , Kubo Izumi
Published: October 2008

Preparation of molecularly imprinted polymer (MIP) layer on a plate type gold electrode was investigated in order to establish a simple and rapid bisphenol A (BPA) sensor system. MIP for BPA was polymerized from pre-polymer cocktail composed of 4-vinylpyridine, ethylene glycol dimethacrylate and BPA. It was spin-coated on the surface of the gold electrode and polymerized as a thin layer by UV light- irradiation for 2-5 min. The surface of MIP modified electrode and bare gold electrode was observed with atomic force microscopy and the MIP modified electrode was apparently different from the gold electrode. BPA was electrochemically oxidized around 580 mV vs. Ag/AgCl reference electrode with the gold electrode and the MIP modified electrode prepared in this study. This electrode can be served as BPA sensor and the anodic current of BPA depended on its concentration at the range of 0.005-0.015 mM.
Bismuth/Glassy Carbon Composite Electrode for the Determination of Trace Lead and Cadmium
Authors: Hwang Gil-Ho , Hong Seok-Jun , Han Won-kyu , Park Joon-Shik , Kang Sung-Goon
Published: October 2008

We examined the use of a bismuth/glassy carbon (Bi/C) composite electrode for the determination of trace amounts of lead and cadmium. Incorporated bismuth powder in the composite electrode was electrochemically dissolved in 0.1 M acetate buffer (pH 4.5) where nanosized bismuth particles were deposited on the glassy carbon at the reduction potential. The anodic stripping voltammetry on the Bi/C composite electrode exhibited well-defined, sharp and undistorted peaks with a favorable resolution for lead and cadmium. Comparing a non-oxidized Bi/C composite electrode with an in-situ-plated bismuth film electrode, the Bi/C composite electrode exhibited superior performance due to its much larger surface area. The limit of detection was 0.41 μ/L for lead and 0.49 μ/L for cadmium. Based on this study, we are able to conclude that various types of composite electrodes for electroanalytical applications can be developed with a prudent combination of electrode materials.
Electrochemical Switching Driven by Structural Change in Secondary Structure and by Complexation to Ligand at the Modified Au(111) Electrode with Polylysine having Phenanthroline and Terpyridine as Ligands
Authors: Nishiyama Katsuhiko , Shimamura Kengo , Sakurai Toshihiko , Taniguchi Isao
Published: October 2008

We synthesized an α-helix forming peptide (LL-phen and LL-terpy) and a random-coiled peptide (DL-phen and DL-terpy) having ligands. By comparing the behavior of these peptide modified electrode, we have found, for the first time, the secondary structure of the peptide and the effect of complexation play roles to control the electrochemical reaction of Fe(CN)64-. The electrochemical responses of Fe(CN)64- were suppressed at the random coiled LL-phen and DL-phen SAMs modified electrodes, however, at the α-helical structured LL-phen SAM modified electrode, the reaction was almost reversible. By the complexation of La3+, the heterogeneous electron transfer rate increased at the random coiled LL-phen SAM and DL-phen SAM, on the other hand, decreased slightly at the α-helical coiled LL-phen SAM.
Single Metal/Dual High-k CMISFETs without High-k-induced Vth Variation by MgO or Al2O3 Incorporation
Authors: Mise Nobuyuki , Morooka Tetsu , Eimori Takahisa , Ono Tetsuo , Nara Yasuo , Ohji Yuzuru
Published: October 2008

We have proposed single metal/dual high-k (SMDH) CMISFETs for aggressively scaled devices. The low threshold voltage (Vth) for n- and pMISFETs are obtained by the dual high-k gate dielectrics. The common gate stack for n- and pMISFETs (single metal) is expected to suppress the variation of gate profile. We have successfully demonstrated low-Vth operation of TiN/HfMgO nMISFETs and TiN/HfAlO pMISFETs that were fabricated in a gate first process flow. We also investigated the high-k-induced Vth variation that can be another origin of the Vth variation. As a result, we found that TiN/HfMgO nMISFETs and TiN/HfAlO pMISFETs do not suffer from high-k-induced Vth variation, but that TiN/HfLaO nMISFETs fabricated by our current process suffer from it. Therefore, we need to optimize the La incorporation process, such as, post-deposition anneal, in order to suppress local high-k-induced Vth variation for TiN/HfLaO nMISFETs.
Universal Correlation Between Mobility and NBTI on Advanced High-k/Metal Gate Stacks
Authors: Reimbold Gilles , Garros Xavier , Casse Mikael , Rafik Mustapha , Leroux Charles , Ribes Guillaume , Martin François
Published: October 2008

Negative Bias Temperature Instabilities (NBTI) and mobility were extensively studied on a wide range of technological options for advanced CMOS gate stack technologies including pure HfO2, silicates, nitrided silicate, HfZr compounds; metal gates included TiN, TaN, TaC, WN with various deposition modes and thicknesses; bottom oxide was pure SiO2 or SiON. The effect of Nitrogen on the two main components of NBTI, fast reversible and slow, is first investigated. Then we show that NBTI and mobility show extensive process variations leading in worst case to bad drivability and reliability. The cause was clearly identified as the Nitrogen incorporated in the stack with cumulative effects with the various process steps. The importance of metal gate is particularly emphasized. By controlling the amount of N in the layers, it is possible to obtain a mobility close to 100% of the universal SiO2 mobility as well as a good reliability
Hot Carrier Reliability of ALD HfSiON Gated MOSFETs with Different Compositions
Authors: Chen H. W. , Chen S. Y. , Lu C. C. , Liu C. H. , Chiu F. C. , Hsieh Z. Y. , Huang H. S. , Cheng L. W. , Lin C. T. , Ma G. H. , Sun S. W.
Published: October 2008

Metal-oxide-semiconductor field-effect transistors (MOSFETs) in-corporating hafnium-silicate (HfSiON) dielectrics with different compositions were fabricated and investigated for hot carrier reli-ability. The experimental results reveal that the channel hot carrier (CHC) stress is worse than drain avalanche hot carrier (DAHC) stress. Moreover, the experimental results also show that the in-crease of oxide trapped charges (ΔNot) depends on Hf content and is about one order of magnitude larger than that of interface traps (ΔNit) after CHC or DAHC stress. Finally, some important interfa-cial parameters, including ΔNit, ΔDit and ΔNot, have also been characterized through the transconductance and subthrehsold swing (SS) methods.
Inversion Layer Mobility in High-k Dielectric MOSFETs - Intrinsic Mobility Degradation by Electric Dipoles at High-k/SiO2 Interface
Authors: Ota Hiroyuki , Hirano Akito , Watanabe Yukimune , Yashuda Naoki , Iwamoto Kunihiko , Okada Kenji , Migita Shinji , Nabatame Toshihide , Toriumi Akira
Published: October 2008

An intrinsic mobility degradation mechanism in high-k gate stacks is proposed. Scattering, due to the electric dipole potential formed at the high-k/SiO2 interface, strongly affects the electron mobility in a metal/high-k gate stack. Comparison of the mobilities in HfO2 gate stacks with different optical phonon structures also revealed that the contribution of remote phonon scattering to mobility degradation is rather small.
Trapping in 1nm EOT high-k / MG
Authors: Zahid Mohammed B , Pantisano Luigi , Degraeve Robin , Aoulaiche M , Trojman L , Ferain I , San Andres E , Shickova A , O'Connor R. , Groeseneken Guido , Heyns Marc M. , De Gendt Stefan
Published: October 2008

PFET's with EOT ~1 nm shows a large hysteresis at high field in the Id-Vg characteristics, while nothing is sensed for nmos devices. An advanced charge pumping technique proves that this hysteresis in pmos is caused by hole traps in the high-k. Furthermore, we show how NBTI defects are affected correlated with such hole traps. We will demonstrate how optimization of the nitridation process can strongly reduce the hole trap density. Phase separation in the HfSiON can be detected by this simple hole trap measurements.
Interface Engineering of a Metal/ High-k/ Ge Layered Structure by Water Vapor Discharge
Authors: Muraoka Kouichi
Published: October 2008

The suppression of interfacial reactions in a tungsten (W)/hafnia (HfO2)/germanium (Ge) structure by water (H2O) vapor discharge was demonstrated. In the case of a HfO2/Ge dioxide (GeO2)/Ge structure, it was confirmed that the thickness of the interfacial GeO2 layer was decreased by H2O vapor discharge. Moreover, in the case of a W/hafnium (Hf)/Ge structure, it was found that such discharge can also achieve the formation of a W/HfO2/Ge structure with abrupt interfaces, without the oxidation of W or Ge. These results suggest that the selective removal of interfacial reaction layers and residual oxygen atoms in metal gate electrodes by hydrogen (H) radicals and the selective repair of oxygen-deficient high-dielectric-constant (high-k) insulators by hydroxyl (OH) and oxygen (O) radicals occur simultaneously during H2O vapor discharge. This means that thermodynamically selective etching and oxidation conditions can be realized using only H2O discharge.
Interface Study in a "Metal / High-k" Gate Stack: Tantalum Nitride on Hafnium Oxide
Authors: Gaumer Clement , Martinez Eugenie , Lhostis Sandrine , Wiemer Claudia , Perego Michele , Loup Virginie , Lafond Dominique , Fabbri Jean-Marc
Published: October 2008

In this work, we investigate the crystalline structure and the chemical properties of a "metal / high-k" gate stack with TaN as gate electrode and HfO2 as dielectric. We show that 3 nm thick HfO2 is crystallized when it is integrated whereas it is amorphous as deposited. Increasing TaN thickness favors the presence of the TaN crystalline FCC phase. Concerning the gate stack chemistry, oxygen and nitrogen diffusion between the layers is evidenced. It occurs during the gate electrode deposition for any TaN thickness. We show that gate stack involving thicker TaN layer are not chemically stable under the spike anneal used for dopant activation, since oxygen and nitrogen diffusion is amplified by this thermal treatment. Gate stacks with a thin TaN layer exhibit a high chemical stability under annealing.
Extraction of Trap Parameters for High-Κ Gate Stacks
Authors: Kar Samares , Rawat S.
Published: October 2008

A small-signal steady state admittance technique, containing some new approaches, is outlined in this paper, for the extraction of the trap parameters, such as the trap density, the trap-energy, and the trap-capture-cross-section/trap-location in the direction perpendicular to the interface, for high-K gate stacks. This technique also yields the experimental values of the total gate-dielectric-stack capacitance, the flat-band voltage, and the surface potential. This technique is applied to p-Si/SiO2/HfO2/TaN MOS capacitors, and the results are presented and analyzed.
Dielectric and Interface Properties of TiO2/HfSiO/SiO2 Layered Structures Fabricated by in situ PVD Method
Authors: Arimura Hiroaki , Naitou Yuichi , Kitano Naomu , Oku Yudai , Yamaguchi Nobuo , Kosuda Motomu , Hosoi Takuji , Shimura Takayoshi , Watanabe Heiji
Published: October 2008

We proposed TiO2/HfSiO/SiO2 layered gate dielectrics and demonstrated the use of the layered structure for scaling equivalent oxide thickness (EOT) and reducing gate leakage current (Jg). Ti diffusion into the HfSiO/SiO2 underlayers, during Ti oxidation annealing for forming TiO2 caps on HfSiO/SiO2, was found to increase leakage current, positive fixed charges, interface state density, and additional charge traps after applying bias stress. By using low temperature Ti-oxidation annealing and forming gas annealing (FGA) treatment, we successfully controlled Ti diffusion and terminated Ti-induced defects. We achieved excellent EOT-Jg characteristics (EOT = 0.71 nm, Jg = 7.2 x 10-2 A/cm2), which are equal to the leakage merit of over five orders of magnitude compared with conventional poly-Si/SiO2/Si gate stacks, while maintaining a superior interface property (interface trap density: Dit = 9.9 x 1010 eV-1cm-2).
Interfacial and Electrical Characterization of HfO2-Gated MOSCs and MOSFETs by C-V and Gated-Diode Method
Authors: Chen S. Y. , Chen H. W. , Chen C. H. , Chiu F. C. , Liu C. H. , Hsieh Z. Y. , Huang H. S. , Hwang H. L.
Published: October 2008

Metal-oxide-semiconductor capacitors (MOSCs) and Metal-oxide-semiconductor field-effect transistors (MOSFETs) incorporating hafnium dioxide (HfO2) dielectrics were fabricated and investi-gated. The electrical and interfacial properties were characterized including C-V, IDS-VGS, the mean density of interface traps per unit area and energy (), energy of interface traps density distribution, interface traps density (Nit), density of near-interface oxide traps per unit area (NNIOT), effective capture cross-section area (σs), mi-nority carrier lifetime (τFIJ) and surface recombination velocity (so) were studied. Furthermore, a comparison with MOSFETs using conventional SiO2 as gate dielectrics was also made.
Fabrication of High-k/Si Structure Using Metal Deposition Followed by Oxidation
Authors: Oniki Yusuke , Iwazaki Yoshitaka , Hasumi Masahiko , Ueno Tomo , Kuroiwa Koichi
Published: October 2008

Hf-metal deposition followed by oxidation directly on Si substrate was presented for the fabrication of HfO2/Si gate stacks. During all of the HfO2/Si fabrication process, such as Hf-metal sputtering deposition and its ECR plasma oxidation, the substrate temperature was maintained at room temperature. HfO2 films fabricated using this process on Si substrates show lower leakage current level with a large k-value (~24). XPS measurements show no sub-oxide layer except Si2+ signal in the HfO2/Si structure. It suggests the HfO2/Si gate stack have an ideal abrupt interface with the presence of only Hf-O-Si bonds on atomically flat Si(100) plane, neither IL-SiO2 nor hafnium-silicide layer.
Electrical Properties of CeOX /La2O3 Stack as a Gate Dielectric for Advanced MOSFET Technology
Authors: Kouda Miyuki , Tachi Kiichi , Kakushima Kuniyuki , Ahmet Parhat , Tsutsui Kazuo , Sugii Nobuyuki , Chandorkar Arun , Hattori Takeo , Iwai H.
Published: October 2008

The electrical properties of CeOx/La2O3 gate stack have been investigated. The leakage current at the EOT around 1.0 nm was suppressed by one order of magnitude by introducing the CeOx/La2O3 stack, compared to that obtained in the La2O3 single layer. MOSFETs with gate stack of the CeOx/La2O3 stack were fabricated, and no significant degradation in mobility or interface state density has been observed.
Study of Kinetic Behaviors of GeO in GeO2/Ge Stacks
Authors: Kita Koji , Lee Choong Hyun , Nishimura Tomonori , Nagashio Kosuke , Toriumi Akira
Published: October 2008

The kinetic behaviors of GeO in GeO2/Ge stacks, which would be crucially important to control the qualities of both GeO2 film and GeO2/Ge interface, were investigated. It was clarified that the GeO volatilization was driven by GeO generation at GeO2/Ge interface, but the volatilization rate was limited by GeO diffusion process in GeO2 film. The volatilization from (111) surface was slower than that from (100), which would come from the difference of reactivity between those surfaces. It was found that the gap states in GeO2 films induced by GeO volatilization were detectable as sub-bandgap photo-absorption. The extinction coefficients of GeO2 films determined by spectroscopic ellipsometry indicated that the gap states were generated by annealing in both N2 and O2 under normal pressure. However, the annealing in high-pressure O2 effectively annihilates those gap states.
Electrical Characteristics of Metal/High-k MOS Devices Using Effective Oxygen Control for Sub-1nm EOT
Authors: Okamoto Koichi , Kakushima Kuniyuki , Ahmet Parhat , Tsutsui Kazuo , Sugii Nobuyuki , Chandorkar Arun , Hattori Takeo , Iwai H.
Published: October 2008

In this study, we have studied the mechanism of equivalent oxide thickness (EOT) increase after annealing using oxygen diffusion model from W gate electrode. It has been revealed that proper thickness W insertion into metal/high-k interface could depress EOT increase after post metallization annealing (PMA) and achieve small CV hysteresis.
Growth and Characterization of Alternative Gate Dielectrics by Molecular-Beam Epitaxy
Authors: Edge Lisa F. , Tian Wei , Vaithyanathan Venu , Heeg Tassilo , Schlom Darrell , Klenov Dmitri , Stemmer Susanne , Wang Jinguo , Kim Moon J.
Published: October 2008

In this work, we have investigated conditions to grow epitaxial La2O3 and Sc2O3 thin films directly on (111) Si as well as epitaxial LaScO3 thin films on (100) Si using an alkaline earth oxide buffer layer. The films were structurally characterized by reflection high-energy electron diffraction (RHEED) during growth and four-circle x-ray diffraction (XRD) and high-resolution plan-view and cross-section TEM, including Z-contrast TEM after growth. The epitaxial La2O3 thin films grew with the following epitaxial relationship (0001) La2O3 // (111) Si La2O3 // [112] Si with 1 additional rotational twin variant. Sc2O3 thin films grew epitaxially with a cube-on-cube orientation relationship on (111) silicon. It was not possible to achieve epitaxial LaScO3 thin films without the use of an alkaline earth buffer layer. The epitaxial orientation relationship between the orthorhombic LaScO3 and the underlying Si was (101) LaScO3 // (001) Si and [010] LaScO3 // [110] Si.
Evaluation of MOCVD Grown Niobium Nitride Films as Gate Electrode for Advanced CMOS Technology
Authors: Thiede Tobias , Parala Harish , Reuter Knud , Passing Gerd , Kirchmeyer Stephan , Hinz Jörn , Lemberger Martin , Bauer Anton , Fischer Roland
Published: October 2008

Niobium nitride films were deposited on Si(100) substrates using tert-butylamido-tris-(diethylamido)-niobium (TBTDEN) as the precursor in a commercial state-of-the-art MOCVD reactor. The depositions were carried out in the temperature range 400 - 800oC and the films were characterized for their crystallinity by X-ray diffraction (XRD) and surface morphology by scanning electron microscopy (SEM). Composition studies by secondary neutral mass spectrometry (SNMS) revealed that the films to be stoichiometric niobium nitride with very low concentrations of carbon or oxygen as impurities. Electrical characterization showed that the specific resistivity was strongly dependent on the substrate temperature during deposition. Furthermore, the work function of the as-deposited niobium nitride films and forming gas annealed films were determined.
MOCVD of Niobium Nitrides and Oxy-Nitrides using an All-Nitrogen-Coordinated Precursor: Thin-film Deposition and Mechanistic Study
Authors: Bekermann Daniela , Barreca Davide , Devi Anjana , Gasparotto Alberto , Fischer Roland
Published: October 2008

In this study, niobium nitride and oxy-nitride thin films were grown by metalorganic chemical vapor deposition (MOCVD) from the guanidinate based niobium compound [Nb(NtBu)(NMe2){C(NiPr)2(NMe2)}2] that served either as a single source precursor (SSP) for NbN or as a niobium and nitrogen source for the growth of niobium oxy-nitride thin films in oxygen atmospheres. The decomposition of this SSP precursor was studied using NMR and mass spectrometry. From the mechanistic studies, it was evident that diisopropylcarbodiimide deinsertion takes place at elevated temperatures. Pure niobium nitride films were obtained without any additional source of nitrogen during the MOCVD process, whereas in the presence of oxygen mixed phases of NbNx, NbOxNy and Nb2O5 were formed. The most relevant results are presented and discussed.
Atomic Layer Deposited Lanthanum-(Zirconate/Aluminate) Based High-K Dielectric Stacks For Future CMOS-Technology
Authors: Abermann Stephan , Henkel Christoph , Bethge Ole , Bertagnolli Emmerich
Published: October 2008

We present an atomic layer deposition (ALD)-process scheme that allows us to deposit ternary oxides such as LaxAlyOz and LaxZryOz at low process temperatures of 250 {degree sign}C. We combine these oxides with ALD-grown Al2O3 to fabricate various high-k dielectric stacks. By means of metal gate / high-k oxide / semiconductor capacitors we evaluate these materials regarding their electrical properties and thermodynamic stability on silicon and germanium substrates. Concerning the silicon substrates, we observe that superior electrical characteristics are achieved if a thin layer of LaxZryOz is sandwiched between two about 1 nm thick Al2O3 layers. By this approach, hydroxylation of the La-containing oxides is suppressed, minimizing leakage currents as well as oxide- and interface charges.
Effect of Ultrathin Si Passivation Layer for Ge MOS Structure with La2O3 Gate Dielectric
Authors: Song Jaeyeol , Kakushima Kuniyuki , Ahmet Parhat , Tsutsui Kazuo , Sugii Nobuyuki , Hattori Takeo , Iwai H.
Published: October 2008

The effect of ultrathin Si passivation layer on Ge MOS characteristics with La2O3 gate dielectric has been examined. Hysteresis on C-V curve was significantly reduced by inserting a Si passivation with thickness of over 1 nm due to suppression of Ge suboxide growth. On the other hand, positive flat-band voltage (Vfb) shift was observed for the samples with the Si layer. The excessive Vfb shift was relieved by increasing Si layer-thickness up to 2.0 nm. By using the 2.0-nm-thick Si passivation layer, superior p-MOSFET characteristics were obtained with little C-V hysteresis. This improvement would be attributed to reduction of oxide trap density by suppressing the Ge suboxide formation.
Gate Dielectrics for High Mobility Semiconductors
Authors: Dimoulas Athanasios , Panayiotatos Yerassimos , Tsipas Polychronis , Galata Sotiria , Mavrou Georgia , Sotiropoulos Andreas , Marchiori Chiara , Rossel Christophe , Webb David , Andersson Caroline , Sousa Marilyne , Richter M. , Fompeyrine Jean
Published: October 2008

In this paper we investigate the impact of charged surface defects on the electronic properties of Ge surface. In addition, we describe new ways of passivating the Ge surface by using reactive rare earth oxides, which catalyze the formation of stable germanates. Their chemical and thermal stability are thought to be responsible for the good electrical properties including very low Dit. In the case of GaAs surface passivation, we show that by optimally adjusting the amorphous Si spacer layer, it is possible to avoid oxidation of GaAs and achieve surface channel inversion.
Mechanism of Charge Storage in nc-RuO Embedded ZrHfO High-k Films
Authors: Lin Chen-Han , Kuo Yue
Published: October 2008

The charge trapping characteristics of the MOS capacitor composed of the nanocrystalline ruthenium oxide embedded Zr-doped HfO2 gate dielectric on the p-type silicon wafer has been studied. The memory function is contributed by hole trapping during the forward sweep as well as electron trapping during the backward sweep when the starting voltage is high. The trapped holes could not be totally eliminated unless a large positive voltage is applied in the backward sweep process. Holes are strongly trapped at the nanocrystal site and loosely trapped at its interface with the high-k material while most electrons are trapped at the nanocrystal site.
Thermally Stable Hf-silicate with Modification of Si Doping and Thermal Budget in MIM Capacitors
Authors: Tzeng Pei-Jer , Wu Tai-Yuan , Wang Ching-Chiun , Lin Cha-Hsin , Lee Lurng-Shehng , Tsai Ming-Jin
Published: October 2008

For the first time, modification of Si doping in Hf-silicates with respect to thermal budget is investigated. Tetragonal phase of HfO2 in Hf-silicate leads to higher dielectric constant after a critical point of thermal budget. Lower critical point (lower thermal budget) is needed for Hf-silicate with a lower Si doping. The tetragonal phase induced higher dielectric constant tends to remain constant even with longer annealing time while the leakage current tends to increase. The optimum condition is a trade-off between the pro of tetragonal phase and the con of the leakage current.
Dielectric Properties of SrTiO3 Thin Films on SrRuO3 Seed Prepared by Plasma-enhanced Atomic Layer Deposition
Authors: Ahn Jihoon , Kim Ja-Yong , Kim Jin-Hyock , Roh Jae-Sung , Kang Sang-Won
Published: October 2008

The dielectric properties of SrTiO3 thin films deposited on SrRuO3 seed layer was investigated. The SrTiO3 thin films were deposited by plasma enhanced atomic layer deposition using titanium tetra-isopropoxide and bis(dipivaloylmethanato) strontium as precursors and oxygen as an oxidant. The SrRuO3 seed layer was formed through deposition of ultra-thin SrO on RuO2 substrate and a post-annealing in O2 ambient. As the results of introducing SrRuO3 seed layer, the dielectric constants of SrTiO3 thin films were increased and the thickness dependency of dielectric properties was reduced compared with the SrTiO3 thin films deposited on Ru directly or seed formed on Ru substrate.
High Performance Ir/TiPrO/TaN MIM Capacitors for Analog ICs Application
Authors: Huang Ching-Chien C. , Cheng C. H. , Chin Albert , Chou C. P.
Published: October 2008

In this paper, we demonstrate high quality material TiPrO and high density TixPr1-xO (x~0.67) metal-insulator-metal (MIM) capacitors using high work function (~5.3 eV) Ir top electrode. Very low leakage current of 7x10-9 A/cm2 at -1 V and high 16 fF/μm2 capacitance density are achieved for 400 oC anneal TiPrO, which also meets the ITRS goals (at year 2018) of 10 fF/μm2 density and J/(C.V)<7 fA/(pF.V) . Furthermore, the improved high 20 fF/μm2 capacitance density TiPrO MIM is obtained at higher annealing temperature, where low leakage current 1.2x10-7 A/cm2 is measured at -1 V. These good performances indicate TiPrO MIM is suitable for analog/RF ICs Applications.