bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Synthesis and Characterization of Group IV Nanocrystals
Authors: Nikolova L. , Riabinina D. , Kadari B. , MacLeod J. M. , Chaker M. , Rosei Federico
Published: April 2010

The first reports that nanostructured silicon emits radiation in the visible wavelength date back twenty years. This observation is interesting from a fundamental point of view and is potentially important for device engineering, as it points to the opportunity of combining microelectronics and optoelectronics on the same silicon chip. This combination is becoming increasingly attractive due to the intrinsic limitations that are being met by the microelectronics industry in its attempt to progressively reduce device features. In this review, we describe and compare the structure and properties of group IV nanocrystals (mostly silicon, with some references to germanium) grown by ion implantation and reactive pulsed laser deposition. Particular emphasis is placed on structural and spectroscopic characterization, as well as size-dependent optical properties. The origin of the luminescence signal and the role of defects and interfaces are discussed in detail.
Luminescent Metal-Organic Frameworks: A Nanolaboratory for Probing Energy Transfer via Interchromophore Interactions
Authors: Meek Scott , Houk Ronald , Doty Patrick , Allendorf Mark
Published: April 2010

The spectroscopic properties IRMOF-1, -8, -9, -10, -15, and -16 have been explored. Analysis of the excitation and emission spectra and crystal structures of these compounds suggests several structure-to-properties relationships. The spectra of IRMOF-8 support previous conclusions that extending π-conjugation decreases linker-metal charge transfer. Comparison of interpenetrated IRMOF-9 and -15 and non-interpenetrated IRMOF -10 and -16 suggest that interpenetration induces greater charge transfer, due to smaller linker-linker and linker-to-metal distances. IRMOF-9 displays wavelength-dependent emission, which we believe arises from asymmetries in its crystal structure, allowing for multiple charge transfer interactions.
Synthesis and Photoluminescence Properties of InVO4:Eu3+ Phosphors Prepared Using Sol-Gel Method
Authors: Shi Zhao-Rong , Chen Hao-Long , Tsai Yeou-Yih , Wu Sean , Chang Yee-Shin
Published: April 2010

InVO4 doped with Eu3+ ions had been synthesized at 950° for 6 hr in air using the sol-gel method. XRD results indicate that the crystallinity of InVO4:Eu3+ powders decreases with increasing Eu3+ ion concentrations. From the SEM images, the shapes of the InVO4 particles are uniform and like pebbles. With increasing Eu3+ ion concentrations, the shapes of the InVO4:Eu3+ particles become smaller and irregular. In the PL studies, the sharp excitation peaks between 300 and 600 nm correspond to the Eu3+ intra-4f transitions. For (In1-xEux)VO4 system, excitation at 326 nm shows that the (In1-xEux)VO4 phosphors display bright red luminescence at about 615 nm belonging to the 5D0→7F2 electric dipole transition, and the time-resolved 5D0→7F2 transition presents a single exponential decay behavior. The saturation of emission intensity excited by intra-4f transitions occurs at a concentration of x = 0.3, indicating that the concentration quenching is active when x > 0.3.
Bilayer Graphene System: Transport and Reliability
Authors: Yu Tianhua , Lee Eun-Kyu , Briggs Benjamin , Nagabhirava Bhaskar , Yu Bin
Published: April 2010

We investigate the key reliability limiting factors of bilayer graphene (BLG) under current stressing by examining the breakdown characteristics of BLG with CMP-copper contacts. It is observed that DC current-induced thermal annealing helps to reduce the BLG-to-Cu contact resistance. Breakdown occurs with two noticeably different failure modes depending on stressing current level, while contact damage dominates in scaled contact structure. The measured linear dependence of breakdown current on graphene width/length aspect ratio suggests Joule heating as the primary breakdown mechanism.
Thermal Transport in Graphene Nanostructures: Experiments and Simulations
Authors: Jauregui Luis A. , Yue Yanan , Sidorov Anton N. , Hu Jiuning , Yu Qingkai , Lopez Gabriel , Jalilian Romaneh , Benjamin Daniel K. , Delkd Derek A. , Wu Wei , Liu Zhihong , Wang Xinwei , Jiang Zhigang , Ruan Xiulin , Bao Jiming , Pei Steven S. , Chen Yong P.
Published: April 2010

Thermal transport in graphene and graphene nanostructures have been studied experimentally and theoretically. Methods and previous work to measure and calculate the thermal conductivities of graphene and related nanostructures are briefly reviewed. We demonstrate that combining Raman spectroscopy for thermometry and electrical transport for Joule heating is an effective approach to measure both graphene thermal conductivity and graphene-substrate interface thermal resistance. This technique has been applied to a variety of exfoliated or CVD-grown graphene samples (both suspended and substrate-supported), yielding values comparable with those measured using all-optical or all-electrical techniques. We have also employed classical molecular dynamics simulation to study thermal transport in graphene nanostructures and suggest such structures may be used as promising building blocks for nanoscale thermal engineering.
Scanning Tunneling Spectroscopic Studies of the Effects of Dielectrics and Metallic Substrates on the Local Electronic Characteristics of Graphene
Authors: Yeh Nai-Chang , Teague Marcus L. , Boyd David A. , Bockrath Marc W. , Velasco Jairo , Lau C. N.
Published: April 2010

Atomically resolved imaging and spectroscopic characteristics of graphene grown by chemical vapor deposition (CVD) on copper foils are investigated and compared with those of mechanical exfoliated graphene on SiO2. For exfoliated graphene, the local spectral deviations from ideal behavior may be attributed to strain induced by the SiO2 substrate. For CVD grown graphene, the lattice structure appears strongly distorted by the underlying copper, with regions in direct contact with copper showing nearly square lattices whereas suspended regions from thermal relaxation exhibiting nearly honeycomb or hexagonal lattice structures. The electronic density of states (DOS) correlates closely with the atomic arrangements of carbon, showing excess zero-bias tunneling conductance and nearly energy-independent DOS for strongly distorted graphene, in contrast to the linearly dispersive DOS for suspended graphene. These results suggest that graphene can interact strongly with both metallic and dielectric materials in close proximity, leading to non-negligible modifications to the electronic properties.
Sputtering Behavior and Evolution of Depth Resolution upon Low Energy Ion Irradiation of GaAs
Authors: Hopstaken Marinus J. , Pfeiffer Dirk , Gordon Michael S. , Kiewra Edward W. , Sun Yanning , Sadana Devendra K. , Topuria Teya , Rice Philip M. , Ronsheim Paul , Gerl Christian , Marchiori Chiara , Richter Mirja , Sousa Marilyne , Fompeyrine Jean
Published: April 2010

We investigate the sputtering behavior and depth resolution upon low energy ion irradiation during Secondary Ion Mass Spectrometry (SIMS) depth profiling of GaAs. We present a systematic and quantitative study of the impact of ion species, primary ion impact energy, and incident angle on the evolution of depth resolution, using a well-defined InGaAs/GaAs multilayer structure with highly abrupt hetero-interfaces. We demonstrate that for low energy O2+ ion beam irradiation, SIMS depth resolution becomes progressively degraded by (transient) incorporation of high surface O-concentration levels in the altered layer, leading to detrimental ion-beam induced formation of topography. In case of low energy oblique Cs+ ion beam irradiation, sputtering behavior of GaAs is well-behaved with no significant transient yield changes and a constant depth resolution. This enables SIMS depth profiling of sharp hetero-epitaxial III-V compound semiconductor structures and shallow dopant profiles with sufficiently good depth resolution with good detection efficiency.
Growth of III/V Materials on Large Area Silicon
Authors: Schineller Bernd , Nguyen N.D. , Heuken Michael
Published: April 2010

The compound semiconductor industry has seen tremen-dous progress in applications ranging from high-power electronics to optoelectronics. However, most of the de-vices being produced today are discrete due to the com-paratively high cost of wafer area and the low level of integration experience compared to the silicon industry. Hence, co-integration with mainstream silicon manufac-turing processes in which the compound semiconductor device is selectively deposited in areas where needed while the rest of the chip is kept in standard silicon VLSI technology is seen as one of the most promising ways to harvest the potential of III-V compounds.
Cross-Sectional UV-Raman Measurement for Obtaining Two-Dimensional Channel Stress Profile in Extremely High-Performance pMOSFETs
Authors: Akamatsu Hiroaki , Takei Munehisa , Kosemura Daisuke , Nagata Kohki , Mayuzumi Satoru , Yamakawa Shinya , Wakabayashi Hitoshi , Ogura Atsushi
Published: April 2010

The two-dimensional channel-stress profiles in extremely high performance p-type metal-oxide-semiconductor field-effect transistors (pMOSFETs) were evaluated by cross-sectional UV-Raman spectroscopy. We found the channel length dependence; the compressive stress in channel Si induced by compressive stress liner and SiGe embedded in the source and drain regions increased with reducing channel length from 5 um to 0.5 um. The compressive stress promoted the electrical properties of pMOSFET. The effect of high-k and metal gate on the channel stress was investigated by measuring the stress before and after the gate stack fabrication. Furthermore, we confirmed the difference of the two-dimensional channel-stress profile between (100) Si and (110) Si. This was achieved by the combination of cleavage and focused ion beam etching.
Investigation of the New Physical Model of Ohmic Contact for Future Nanoscale Contacts
Authors: Takada Yukihiro , Muraguchi Masakazu , Endoh Tetsuo , Nomura Shintaro , Shiraishi Kenji
Published: April 2010

Fabrication of good Ohmic contacts is quite important not only for device application but also for fundamental physics. In accordance with the device scaling, it is inevitable to prepare nano-scale Ohmic contacts for future LSIs technology. In this study, we hereby propose a new electronic structure model for Ohmic contacts, with which it is possible to describe the real situation precisely. Our proposed model contains many discrete levels that, originate from vacancies and impurities located in the vicinity of the metal and the semiconductor interface, within the energy range of the Schottky barrier height. We calculate the current-voltage characteristics based on our proposed model. Calculated results show that our proposed model reveals linear Ohmic I-V characteristics without conventional band alignment for the Ohmic contacts. Moreover, we found that energy distribution of the discrete levels is important for obtaining Ohmic characteristics.
(Invited) Ultimate EOT Scaling (< 5Aå) Using Hf-Based High-κ Gate Dielectrics and Impact on Carrier Mobility
Authors: Ando Takashi , Frank Martin M. , Choi Kisik , Choi Changhwan , Bruley John , Hopstaken Marinus J. , Haight Richard , Copel Matthew , Arimura Hiroaki , Watanabe Heiji , Narayanan Vijay
Published: April 2010

We demonstrate a novel remote interfacial layer (IL) scavenging technique yielding a record-setting equivalent oxide thickness (EOT) of 0.42 nm using a HfO2-based high-k gate dielectric. The remote IL scavenging shows advantages in carrier mobility and gate leakage current over conventional IL scaling schemes. Moreover, this method enables intrinsic EOT scaling without introducing additional charges and interface degradation. It is shown that the mobility degradation observed for a La-containing high-k is not due to the La-induced dipole but due to the intrinsic IL scaling effect, whereas an Al-induced dipole brings about additional mobility degradation. This unique nature of the La-induced dipole in conjunction with the IL scaling enables aggressive EOT scaling toward the end of the road map.
Transformation of Crystalline Structure of HfO2 by La- or Y-Oxide Capping and Annealing
Authors: Suzuki Takayuki , Matsuki Takeo , Morooka Tetsu , Sato Motoyuki , Yugami Jiro , Ikeda Kazuto , Ohji Yuzuru
Published: April 2010

Using X-ray diffraction (XRD) technique, we have investigated the crystallinity of La- or Y-doped HfO2, formed with a capping process achieved by varying the crystallinity of the base-HfO2. In the capping process, high temperature annealing was performed after the deposition of La-oxide or Y-oxide on the base-HfO2. After the annealing, we found that the crystallinity of the La-doped HfO2 depended on the crystallinity of the base-HfO2, although the Y-doped HfO2 exhibits only a small dependency. To achieve crystalline La-doped HfO2 having higher-k with capping process, the base-HfO2 should be amorphous.
Impact of the Metal Gate on Carrier Transport in HK/MG Transistors
Authors: Cassé Mikaël , Garros Xavier , Brunet Laurent , Reimbold Gilles
Published: April 2010

We have investigated the effect of the nitrided metal gate (such as TiN or TaN) on the carrier mobility in high-k/metal gate transistors. N-induced defects are evidenced and correlated to the electron mobility degradation. Hole behavior is compared and found to differ significantly. Al integration in advanced metal gate is also found to degrade the electron mobility in a similar way as N.
(Invited) High Performance and Highly Uniform Metal Hi-K Gate-All-Around Silicon Nanowire MOSFETs
Authors: Sleight Jeffrey W. , Bangsaruntip Sarunya , Cohen Guy , Majumdar Amlan , Zhang Ying , Engelmann Sebastian , Fuller Nicholas , Gignac Lynne , Mittal Surbhi , Newbury Joseph , Barwicz Tymon , Frank Martin M. , Guillorn Michael
Published: April 2010

We demonstrate undoped-body, gate-all-around (GAA) Si nanowire (NW) MOSFETs with excellent electrostatic scaling. These NW devices, with a TaN/Hf-based gate stack, have high drive-current performance with NFET/PFET IDSAT = 825/950 uA/um (circumference-normalized) or 2592/2985 uA/um (diameter-normalized) at supply voltage VDD = 1 V and off-current IOFF = 15 nA/um. Superior NW uniformity is obtained through the use of a combined hydrogen annealing and oxidation process. Clear scaling of short-channel effects versus NW size is observed.
Effect of Ozone Concentration on Atomic Layer Deposited HfO2 on Si
Authors: Chung Keum Jee , Park Tae Joo , Sivasubramani Prasanna , Kim Jiyoung , Ahn Jinho
Published: April 2010

Effect of ozone concentration (200-400 g/Nm3) on atomic layer deposition of HfO2 thin films on Si wafers using tetrakis (dimethylamino)hafnium (TDMAHf) as Hf precursor was systematically studied. High-resolution transmission electron microscopy and x-ray photoelectron spectroscopy analyses show that oxidation of the Si substrate enhances with ozone concentration which leads to an increase in interfacial layer (IL) thickness between the high-k dielectric and the substrate. The relatively thicker IL successfully suppresses additional growth of itself and Si out-diffusion into the dielectric during post deposition annealing (PDA). Corresponding electrical characteristics such as capacitance-voltage, leakage current density and time zero dielectric breakdown display significant improvement for HfO2 film prepared using higher ozone concentration after PDA.
(Invited) Interface Investigation of ALD Dielectrics on III-N Substrates for RF, Mixed Signal and Power Applications
Authors: Misra Veena , Suri Rahul , Kirkpatrick Casey
Published: April 2010

It is believed that nitride-based field effect transistors will play a dominant role in nextgeneration high-frequency and high-power electronics. The III-nitride family of wide bandgap semiconductors exhibits spontaneous polarization which is exploited in electronic devices such as AlGaN/GaN heterostructure field effect transistors (HFETs), where polarization charges create a 2D electron gas at the heterointerface. Though promising, these devices also present several technical challenges. These include (i) I-V dispersion and drain current collapse [1], (ii) gate- and drain-lag [2], and (iii) large gate leakage [3]. To address this, several dielectrics have been investigated on III-N surfaces [4-6]. However, fundamental insight into surface states between the dielectric layer and the semiconductor, dielectric properties such as bandgap, band offsets and defects, interaction of metal electrodes in further modulating leakage and threshold and overall reliability is still lacking and is critical in overcoming these barriers. Furthermore, the evaluation of alternate dielectrics for III-N devices is highly timely since (i) the recent transition of Si CMOS to high-K has demonstrated that deposited oxides can be of high quality, (ii) the emergence of atomic layer deposition as a manufacturable, scalable, monolayer-control technique to deposit dielectrics and (iii) the successful demonstration of high-K on GaAs, InGaAs and InSb has provided insight into compound surface chemistries with dielectrics.
(NH4)2S Passivation of High-k/In0.53Ga0.47As Interfaces: A Systematic Study of (NH4)2S Concentration
Authors: O'Connor Eamon , Brennan Barry , Contreras Rocio , Milojevic Marko , Cherkaoui Karim , Monaghan Scott , Newcomb S. B. , Pemble Martyn E. , Hughes Greg , Wallace Robert M. , Hurley Paul K.
Published: April 2010

In this work we present the results of an investigation into the effectiveness of varying (NH4)2S concentrations in the passivation of n-type and p-type In0.53Ga0.47As, as determined through analysis of electrical properties. Samples were degreased and immersed in aqueous (NH4)2S solutions of concentrations 22%, 10%, 5%, or 1% for 20 minutes at 295K, immediately prior to ALD growth. Capacitance-voltage results on capacitor structures indicate that the lowest frequency dispersion over the bias range examined occurs for n and p-type devices treated in 10% (NH4)2S solution. The deleterious effect on interface state density of increased ambient exposure time after removal from (NH4)2S solution is also presented. Estimations of peak interface state density, Dit, extracted from the equivalent parallel conductance Gp, using an approximation to the conductance method, are used for comparison of the different passivation conditions.
SiO Emission and Incorporation in Silicon Oxidation Process Using Molecular Dynamics Method
Authors: Takahashi Norihiko , Yamasaki Takahiro , Kaneta Chioko
Published: April 2010

We investigated the dynamics of oxidation processes with stress relaxation in the Si/SiO2 interface by using variable charge molecular dynamics methods. An SiO molecule is emitted from the Si/SiO2 interface into the SiO2 region in order to release the accumulated stress in the interface. The emitted SiO molecule moves into the SiO2 network having Si dangling bonds. The SiO molecule is completely incorporated into the SiO2 network after an oxygen atom (oxygen vacancy) diffuses to be bonded with these Si dangling bonds.
Quasi-Ballistic Hole Transport in an AlGaN/GaN Nanowire
Authors: Mastro Michael , Kim H.-Y. , Ahn J. , Kim J. , Hite Jennifer , Eddy Charles
Published: April 2010

An AlGaN/GaN nanowire, with an isosceles-triangle cross-section, was designed to create a large negative polarization at the (000-1) facet. The resultant band bending at this interface formed a two-dimensional potential well that accumulated a hole gas. Transistor operation based on the two-dimensional hole gas showed characteristics of quasi-ballistic transport. A small number of elastic scattering sites were evident from quantum interference characteristics in the current-voltage data.
Light Extraction Enhancement of n-Side Up Light-Emitting Diodes Without Electrodes Covering by Wafer Bonding and Textured Surfaces
Authors: Horng Ray-Hua , Lu Yi-An , Wuu Dong Sing
Published: April 2010

Textured n-side-up GaN LED with interdigitated imbedded electrodes (IIE) eliminating the electrode-shading loss with high reflection mirror and double-side roughening on both p-GaN and undoped-GaN layers have been investigated. The epitaxial layers of the device are grown on (0001) sapphire substrates by metal-organic chemical vapor deposition. The devices are subsequently fabricated with wafer-bonding, laser lift-off, chemical dry/wet etching techniques. This n-side up structure was useful to enhance light extraction and increase the light output power. We compared the performance of the luminance intensity(at 350 mA injection current), which is 78.85 % and 115.38 % higher than those of the conventional structure and the p-side up structure with high reflection mirror on silicon substrate with electrode shading, respectively.
Drain Leakage Current in MuGFETs at High Temperatures
Authors: Giroldo Jorge , Bellodi Marcello
Published: April 2010

This paper will show the drain leakage current (IDLeak) behavior in SOI Multiple-Gate devices (MuGFET) for double-gate (DGFinFET) and triple-gate (TGFinFET) configurations, operating since room temperature up to 300°C. Through three dimensional (3D) numerical simulations results is observed that IDLeak is composed mainly by electrons for all devices operating at same conditions. Besides it, lower IDLeak values are observed for all TGFinFET, when compared to DGFinFETs, analyzed in this investigation.
Cuprous Oxide Solution Preparation and Application to Cu2O-ZnO Solar Cells
Authors: Du Pasquier Aurelien , Duan Ziquing , Pereira Nathalie , Lu Yicheng
Published: April 2010

Preparation of photoactive cuprous oxide (Cu2O) is achieved via simple solution treatment of copper foils in copper sulfate aqueous solution. XRD indicates that pure Cu2O phase is obtained, and gel electrolyte is used to probe high photocurrent on the film. Zinc oxide layer is deposited via MOCVD or spin coating, and the resulting Cu2O-ZnO heterojunction solar cells are characterized with transparent Au or gallium doped zinc oxide (GZO) top contacts.
Thermophysical Properties of Binary Aliphatic Quaternary Ammonium Ionic Liquids: TMPAFSAxTFSA1-x
Authors: Mizuhata Minoru , Kunikata Nobuaki , Deki Shigehito
Published: April 2010

The anionic binary Ionic liquids; TMPAFSAxTFSA1-x were prepared as mixture of TMPATFSA and TMPAFSA. From the results of DSC analysis, the binary system showed the simple binary eutectic phase diagram and the eutectic point was found at the composition point of x = 0.33. In this system, each anion vibrated independently and showed isomerization equilibria displacement with temperature change. It was suggested that the equilibria displacements affected to the liquid structure and cis-trans isomerization of each anion played an important role in the solidification of TMPAFSAxTFSA1-x.
Ion Mobility of 1-Ethyl-3-methylimidazolium Tetrafluoroborate and 1-Ethyl-3-methylimidazolium Bis(trifluorosulfonyl)amide Ionic Liquids
Authors: Umecky Tatsuya , Saito Yuria , Matsumoto Hajime
Published: April 2010

The mobilities of the cation and anion species in 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids were measured at four different temperatures from 298.2 to 313.2 K on the basis of electrophoretic NMR method. The comparison between the mobilities and the NMR diffusion coefficients showed that the cation and anion mobilities become larger as the diffusion coefficients increase and are almost equal to each other unlike in the case of the diffusion coefficients. Moreover, all the experimentally obtained mobilities are found to be appreciably higher than the calculated ones from the diffusion coefficients with the Einstein relation. The deviation of the experimental mobilities from the Einstein relation was discussed in terms of the ion transport mechanisms.
Protons: Affinity and Reduction in Ionic Liquids
Authors: Johnson Keith E. , Driver Gordon
Published: April 2010

Proton affinities dictate that protic salts are dissociated into molecules in the gas phase. In the liquid phase, protons are associated with charge neutral base molecules or homoconjugate/heteroconjugate anions. For example, liquids prepared from a base and a hydrogen halide contain the protonated base and either the halide or the halohydrogenate(I) anion; thus 2 classes of proton may be available for reduction. It happens that the anionic protic species are more readily reduced. This situation extends to complex hydrogen halides and anhydrous carboxylic acids. NMR data provide evidence of proton transfer and spectrophotometry can give a measure of acidity. Protic species alone may or may not ionize, depending on the proton affinity of the species itself. The formation of salts from base and protic species is discussed in terms of the pair of dissociation constants for dimethylsulphoxide, acetonitrile, water, and the gas phase, with limitations imposed by solvent leveling noted.
Electroanalytical Chemistry in Polymer-RTIL Composite with an In Situ Electrochemical SEM System
Authors: Tsuda Tetsuya , Sato Yuichi , Kuwabata Susumu
Published: April 2010

The specific conductivity of a polymer-room-temperature ionic liquid (RTIL) composite composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and 1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (BuMeImTf2N) was less than neat RTIL because of an increase in activation energy estimated from Arrhenius plot, which implies that there is an unignorable interaction between the polymer matrix and the RTIL. Electrochemical reactions in the PVdF-HFP-BuMeImTf2N composite with negligible vapor pressure were investigated by the use of in situ electrochemical scanning electron microscope (ECSEM) system. Those reactions include Ag electrodeposition and actuation behavior. The results suggested that in situ ECSEM technique has the great possibility to be a future electroanalytical chemical method.
(Invited) Integration Challenges for Copper Damascene Electroplating
Authors: Stöckgen Uwe G. , Wehner Susanne , Heinrich Jens , Kiesel Axel , Liske Romy
Published: April 2010

Copper electroplating has become the commonly used technology to manufacture interconnects in semiconductor products. The art of copper damascene electroplating is to provide a void-free fill for all design features, but to avoid high topography on top of those structures at the same time. The desired direction is superfill. The most widely published way to control this is to find the right electrolyte additive type and concentration for the features that have to be filled. However, there is a variety structures on a semiconductor chip and in a high-volume manufacturing there is a variety of products that may have different optimal fill conditions. In this paper, fill and topography control by current density modification and its implication to CMP will be shown.
Chemical Repair of Plasma Damaged Porous Ultra Low-k SiOCH Film using a Vapor Phase Process
Authors: Oszinda Thomas , Schaller Matthias , Schulz Stefan E.
Published: April 2010

A vapor phase based silylation process was used to restore plasma damaged porous ultra low-κ SiOCH dielectric films. The process was carried out with eleven different silylation agents. After processing of blanked wafers, the restoration performance was characterized by different analytic techniques like Fourier Infrared and Auger electron spectroscopy as well as contact angle and mercury probe measurements. Quantum mechanics calculations and practical results suggest three repair chemicals having two reactive groups to be most promising. However, a comparable electrical improvement, i.e. κ-value improvement was achieved with chemicals having one reactive group. A thin dielectric layer formation was found to be one explanation for this effect. This is supported by a high surface free energy recovery after the repair process, without carbon incorporation near the surface. Hence, depending on the requirement to the restoration (κ-value, carbon restoration, etc.) chemicals having one reactive group can be sufficient as well.
Miniaturization of a Wireless Sensor Node by Means of 3D Interconnects
Authors: Prainsack Josef , Stolle Joern , Weber Josef , Dielacher Markus , Flatscher Martin , Herndl Thomas , Matischek Rainer , Ramm P. , Weber Werner
Published: April 2010

This work presents an advanced sensor node for direct tire pressure monitoring with an overall size below 1 cm3, where the applied components are arranged in a 3D integrated stack for high compactness, improved thermal behavior, and enhanced robustness for pressure, inertia, and temperature sensing. The utilized through silicon via (TSV) technology is introduced and the wide range of resulting issues for the design of a sensor node are considered. In particular, the radio frequency (RF) characteristics of TSVs are investigated in detail focusing on their electrical efficiency. Finally an optimized TSV design is presented, which allows the connection of a Bulk Acoustic Wave (BAW) resonator with an impedance of 2 kΩ at 2.1 GHz. Thus, all required types of interconnections within the sensor node can be realized by means of the TSV technology.
(Invited) 3D Interconnect Technologies for Advanced MEMS/NEMS Applications
Authors: Lietaer Nicolas , Taklo Maaike , Schjo̸lberg-Henriksen Kari , Ramm P.
Published: April 2010

3D integration and wafer level packaging (WLP) with through-silicon vias offer benefits like reduced footprint and improved performance. CMOS imaging sensors is one of the first successful introductions of a product with TSVs on the market, and 3D integrated memory stacks are expected to follow soon. Also sensor and actuator systems based on micro- and nano-electromechanical systems (MEMS/NEMS) will greatly benefit from WLP and 3D integration of the transducers and their readout and controller ICs. Ultimately, heterogeneous integration of different device technologies will allow the fabrication of MEMS/IC and NEMS/IC products with new and improved functionalities. For this to become a reality, cost-effective and reliable 3D integration technologies need to be developed. This paper gives an overview and reports on the current status of 3D interconnect technologies that will enable 3D integration for advanced MEMS/NEMS applications.
(Invited) Electrolytes, SEI and Charge Discharge Kinetics in Li-Ion Batteries
Authors: Jow T. Richard , Allen Jan , Marx Michelle , Nechev Kamen , Deveney Bridget , Rickman Sarah
Published: April 2010

Charge discharge kinetics of Li-ion batteries is dominated by the lithium ion (Li+) charge transfer kinetics, which involves the process of transporting the solvated Li+ in the electrolyte to the insertion of Li+ and the accepting of an electron at the same time in the electrode active materials. The importance of electrolytes and recent studies of Li+ charge transfer kinetics were briefly reviewed. Using 3-electrode cells and a DC Pulse Current Impedance method, we examined the charge discharge kinetics of the anode and the cathode in the same electrolyte at the same time. We observed a slower kinetics at the graphitic carbon anode as indicated by higher activation energy than that at the lithium nickel cobalt aluminum mixed oxide (LiNi0.80Co0.15Al0.05O2) cathode. While desolvation is a dominating step as concluded in recent studies on the Li+ charge transfer kinetics, this study suggests that the nature of SEIs and electrode materials play crucial roles on Li+ charge discharge kinetics.
(Invited) LiFSI-PYR1AFSI Binary Electrolyte Mixtures for Lithium Batteries
Authors: Appetecchi Giovanni B. , Carewska Maria , Montanino Maria , Alessandrini Fabrizio , Passerini Stefano
Published: April 2010

A physicochemical and electrochemical investigation on lithium batteries binary electrolyte mixtures, based on N-alkyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ionic liquids (PYR1AFSI) and lithium bis(fluorosulfonyl)imide (LiFSI) as salt, is presented and discussed. The melting point of PYR1AFSI decreases with the addition of LiFSI, this allowing to obtain low-temperature (-20{degree sign}C) highly conductive (0.5 mScm-1) and non volatile electrolytes. The ionic transport properties were found well correlated with the thermal behavior. The incorporation of LiFSI resulted in a decreased thermal stability and the appearance of minor parasitic cathodic reactions with respect the neat PYR1AFSI materials, likely due to impurities in the LiFSI salt. Despite this issue, the electrochemical stability window was found to exceed 5 Volt.
Single Walled Carbon Nanotubes for Efficient Electronic and Ionic Transport in the Lithium-Ion Batteries
Authors: Dettlaff-Weglikowska Ursula , Yoshida Jun , Sato Norio , Roth Siegmar
Published: April 2010

We investigated the electrochemical properties of LiCoO2 composites with single walled carbon nanotubes (SWNTs) in order to apply them as cathode material in Li-ion batteries. Purified SWNTs, produced by catalytic conversion of high-pressure CO (HiPco) have been selected as conductive additives. Reference composites based on the carbon black have also been prepared and evaluated. We found out that the 0.5 weight % of Hipco tubes can sufficiently replace 10 weight % of carbon black in the composite considering the internal resistance of the assembled electrochemical cell as well as the battery performance. Our experiments provide the proof of principle that inorganic particles of LiCoO2 in a composite with conducting SWNTs can be electrically wired in a network for efficient electronic and ionic transport in the Li-ion battery.
Thermal Stability of Delithiated Al-substituted Li(Ni1/3Co1/3Mn1/3)O2 Cathodes
Authors: Love Corey T. , Johannes Michelle D. , Swider-Lyons Karen
Published: April 2010

The thermal stability of a layered transition metal oxide with complete Al-substitution, Li1-xNi1/3Co1/3Al1/3O2 (NCA1/3), is studied in comparison to its better understood analogue, Li1-xNi1/3Co1/3Mn1/3O2 (NCM), to elucidate information critical to the safety of lithium-ion batteries. NCA1/3 and NCM have crystalline structures with the R-3m space group by high temperature synthesis from coprecipitate precursors. The specific capacities for NCA1/3 and NCM are 115 mAh/g and 180 mAh/g within 2.5-4.5 V. Thermogravimetric analysis coupled with mass spectrometry confirms the loss of oxygen at 271°C and 292°C for NCM and NCA1/3 delithiated to 4.4 V, respectively. The heat generation reaction of delithiated NCM is 91.7 J/g compared to 10.5 J/g for NCA1/3. The improved thermal stability offered by NCA1/3 is attributed to its low Li+ capacity due to the substitution of Al3+ for Mn4+ and its low heat of reaction due to the stability of the intermediate crystalline phases during delithiation and annealing.
Lithium Plating Behavior in Lithium-Ion Cells
Authors: Bugga Ratnakumar V. , Smart Marshall C.
Published: April 2010

A Li-ion cell does not contain metallic lithium under normal conditions of operation. Under strenuous charge conditions, however, metallic lithium may deposit on the carbon anode in preference to lithium intercalation and may cause problems in terms of performance, reliability and safety of the cell. Factors that affect the anode polarization and also Li intercalation kinetics play a crucial role in determining the propensity for such lithium deposition. Such factors include the nature of electrolyte, anode/cathode capacity ration, which have been studied with specific examples here. Further, various prototype cells from different manufacturers have been examined for their susceptibility towards lithium plating from a set of systematic charge/discharge tests at different charge rates and temperatures.
(Invited) Na-CMC as Possible Binder for LiFePO4/C Composite Electrodes: The Role of the Drying Procedure
Authors: Lux Simon F. , Balducci Andrea , Schappacher Falko M. , Passerini Stefano , Winter M.
Published: April 2010

The use of sodium carboxymethylcellulose as possible binder for positive LiFePO4/C composite electrodes in Li-ion batteries has been investigated. The influence of two different drying procedures on the structure and on the electrochemical performance of the LiFePO4/C composite electrodes has been evaluated. The results of this investigation are presented in this manuscript.
Dissolution Behavior of α and γ Phases of a Duplex Stainless Steel in a Simulated Crevice Solution
Authors: Aoki So , Yakuwa Hiroshi , Mitsuhashi Katsuhiro , Sakai Jun'ichi
Published: April 2010

The purpose of this study is to clarify corrosion mechanism of a duplex stainless steel (DSS) through dissolution behavior of a ferritic phase and austenitic phase, respectively. A single phase specimen ([α] or [γ] phase specimen) which has chemical composition of each phase of a DSS was prepared by preferential dissolution of the DSS, and dissolution behavior of each phase specimen was investigated. The [α] specimen showed a less-noble corrosion potential compared to the [γ] specimen. The change of the corrosion potential of the DSS was located somewhere between those of each phase specimen. The [α] specimen showed a less-noble active peak compared to the [γ] specimen. The current density value of the DSS was located between the current values of the each phase specimen. It was clarified that corrosion mechanism of a DSS could be described through the dissolution behavior of the single phases such as α phase and γ phase.
Anodic Dissolution of Titanium in Ethylene Glycol Solution Containing Chloride Salt
Authors: Fushimi Koji , Kondo Hirofumi , Konno Hidetaka
Published: April 2010

Anodic dissolution behaviour of titanium in ethylene glycol solution containing chloride salt was examined using a rotating disk electrode. A potential-independent dissolution current flowed depending on the rotation speed, species and concentration of chloride salts. The current controlled by the mass transfer process could flow in concentrated chloride solutions, but decreased with increase in chloride concentration. A smaller current flowed in solution with a high concentration of titanium species, indicating that the diffusion-controlling species are titanium species, not chloride ions. Electrochemical impedance spectroscopy revealed that a titanium chloride salt layer was formed between the titanium substrate and diffusion layer during the mass transfer-controlling anodic dissolution of titanium.
Towards the 3-D Microfabrication and Integration of a Complete Power Unit Used for Energy Autonomous Wireless System
Authors: Pichonat Tristan , Lethien Christophe , Hourlier Djamila , Tiercelin Nicolas , Troadec David , Rolland Paul Alain
Published: April 2010

This paper deals with the fabrication of an all-solid lithium-ion microbattery for autonomous wireless sensors networks nodes, focusing especially on the solid electrolyte and the negative electrode made of silicon nanowires. Regarding the electrolyte, amorphous thin solid films of lithium phosphorus oxynitride (LiPON) were prepared by radio-frequency sputtering of a mixture target of P2O5-Li2O in ambient nitrogen atmosphere. The morphology, composition, and ionic conductivity were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and A.C. impedance spectroscopy. A microstructuring process is proposed, including a double masking with silicon oxide and silicon nitride layers. Finally, the combination of silicon nanowires and LiPON is presented.
Development of Multifunctional Catalysts for Electrooxidation of Ethanol
Authors: Zurowski Artur , Kolary-Zurowska Aneta , Marassi Roberto , Kulesza Pawel J.
Published: April 2010

This study describes the activity of Pt40%/Vulcan XC-72 carbon catalyst modified with Rb2.5H0.5PW12O40 zeolite-type matrix prepared by a mixing method. The catalyst is used to induce the anodic oxidation of ethanol in an acidic medium as well as to investigate its suitability for use in direct ethanol fuel cells (DEFCs). Under the same Pt-loading, mass, and experimental conditions for ethanol oxidation, the catalysts containing the above mentioned zeolite-type supports display significantly enhanced electrocatalytic activity in comparison to unmodified Pt40%/Vulcan XC-72 carbon. Our new system containing the Nafion-treated rubidium salt of Keggin-type heteropolyacid as a matrix and the Pt40%/Vulcan XC-72 carbon catalyst was characterized with respect to its electrochemical properties and its electrocatalytic activity towards the ethanol oxidation. Results clearly indicate that proposed catalyst containing Rb2.5H0.5PW12O40 (RbPW) matrix is of potential utility to direct ethanol fuel cell.
Electrochemical Double Layer Capacitance in Activated Carbon: Ion Size Effects
Authors: Kirk Donald W. , Graydon John W.
Published: April 2010

Supercapacitors are ideal devices for rapid storage and release of energy. They can provide an electrical energy buffer between a rapidly changing load and a battery or fuel cell which work best under steady state conditions. Activated carbon is an important substrate for many of the commercially available double layer supercapacitors. Despite the research and commercialization work that has been carried out, there is still a need to understand some of the fundamental characteristics of the role of activated carbon in the double layer charging. The effect of cation size in an aqueous electrolyte on capacitance was investigated. The results showed capacitance decreased with hydrated ion size for an activated carbon with a significant micropore surface area.
Charge-Discharge Behavior of Electric Double-Layer Capacitor with Alginate/Ionic Liquid Gel Electrolyte
Authors: Yamagata Masaki , Soeda Kazunari , Yamazaki Shigeaki , Ishikawa Masashi
Published: April 2010

Non-aqueous gel electrolytes based on an alginate (Alg) and 1-ethyl-3-methylimidazolim tetrafluoroborate (EMImBF4) were prepared for electric double layer capacitors (EDLCs). The transparent colorless gel sheet has high mechanical intensity and high retentivity of ionic liquids enough to construct EDLC cells. According to charge/discharge measurements, the model EDLC cell with an Alg/EMImBF4 gel shows high discharge capacitance in spite of using a gel-state electrolyte, implying that high affinity of alginate for an activated carbon electrode leads to a decrease in the electrode/electrolyte interfacial resistance. A test cell with Alg(3%)/EMImBF4 maintains its coulombic efficiency over 99.8 % during 4,000 cycles.
Nafion Hybrid Membranes for Use in Vanadium Redox Flow Batteries
Authors: Schulte Dominik , Drillkens Julia , Schulte Bjoern , Sauer Dirk Uwe
Published: April 2010

The membrane is the key component of a redox flow system, as it has to avoid cross-contamination of the ions of the active material as well as to permit high proton conductivity. A membrane with drastically reduced cross-contamination ability would overcome a main problem of several redox couples and in consequence a wider variety of redox couple would potentially allow redox flow systems with higher energy densities or lower material costs.. This work deals with modifications of Nafion membranes to decrease the cross-contamination ability without affecting the proton conductivity. Several in situ-gel reactions were used for modification of the membranes.
CO Induced Reconstruction of PtxCoy Electrocatalytic Nanoparticles in a PEM Fuel Cell Anode under Transportation Operating Conditions
Authors: Cheah Seng Kian , Lemaire Olivier , Gélin Patrick , Franco Alejandro A.
Published: April 2010

In this paper, based on a multiscale modelling framework, we focus on understanding the impact of CO adsorption on the intrinsic stability properties of PtxCoy nanoparticles under PEMFC anode operating conditions. First, CO adsorption effect on PtxCoy has been studied by using Monte Carlo (MC) simulation. Then, the MC results are coupled with an ab initio based kinetic model to simulate the effect of CO poisoning on the activity and durability of the PtxCoy nanoparticles as HOR catalysts. The results are compared with simulations carried out with pure Pt, where potential self-oscillatory behaviour is detected and experimentally confirmed. The PtxCoy HOR activity and stability reveals to be strongly dependent on the nanoparticle size and composition. For some nanoparticle sizes, simulations show that PtCo nanoparticles provide better CO tolerance than Pt3Co. CO adsorption on PtCo slows down Co dissolution in short-term operation. However, this effect is overcome by the increase of the anode potential due to CO adsorption. Thus, CO adsorption enhances Co dissolution in long-term operation. Due to this Co dissolution, the HOR activity of PtCo degrades faster than Pt3Co in long-term operation.
Generation of Hydrogen Peroxide in DMFC
Authors: Agladze Giorgi R. , Nikoleishvili Paata , Tsurtsumia Gigla , Kveselava Valemtina , Gorelishvili Giorgi , Latsusbaia Roman
Published: April 2010

The novel process of H2O2 generation in the direct methanol fuel cell (DMFC) composed from the "Black Pearls 2000" gas-diffusion cathode (GDE), washed by sodium chloride brine or sea water for O2 electro-reduction and the half-membrane-electrode assembly (MEA) with the Nafion 115® cation-exchange membrane (CEM), hot pressed on one side with the carbonic gas-diffusion anode impregnated by Pt/Ru catalyst for methanol oxidation, has been developed. The effect of NaCl concentration in the catholyte, methanol and the KOH concentration in the anolyte, electrolyte temperature and circulation flow rate on the generated cell voltage, current and H2O2 current efficiency have been studied in 2 hour trials. 87-95 % current efficiency for H2O2 generation with a 5.286 -9.44 mg h-1 cm-2 rate and at 15 mA cm-2 current density was achieved in the DMFC with 1 M CH3OH +7M KOH in the anolyte and 30 g L-1 NaCl in the catholyte.
Studies of Energy Efficiency and a Control of High-Pressure Hydrogen Production
Authors: Hazeki Kenta , Katayama Noboru , Kudo Yusuke , Kogoshi Sumio
Published: April 2010

We developed a high-pressure electrolyzer system (HPESes) using LabVIEW. HPESes play a very important role for hydrogen stations and independent distributed power sources, which store hydrogen gases in high-pressure cylinders or hydrogen storing alloys. The experimental results show that this system can automatically rise the pressure of hydrogen up to 0.7MPa. The energy efficiency of this system is higher than that of a typical system using a compressor.
The MATLAB/Simlink Model of an Electrolyzer System for High-Pressure Hydrogen Production
Authors: Katayama Noboru , Hazeki Kenta , Kudo Yusuke , Kogoshi Sumio
Published: April 2010

A model using MATLAB/Simlink for a high-pressure electrolyzer system has been developed. The model includes the gas state equation, the motion dynamics model of a gas cylinder which eliminates the differential pressure between hydrogen and oxygen, and the controller that observes the position of the piston. The simulation results closely agree with the experimental ones on the pressures of the generated hydrogen and oxygen, the position of the piston quantitatively.
Electropolymerization of Polyanile Films under Magnetic Field Control
Authors: Aaboubi Omar , Douglade Jacques , Jbara Omar
Published: April 2010

Cyclic Voltammetry, electrochemical impedance spectroscopy (EIS) and magnetohydrodynamic transfer function (MHD-TF) measurements have been carried out to study the magnetic field influence on the electropolymerisation of polyaniline (Pani) films from hydrochloric acid media. In the potentiostatic regime the EIS measurements and the MHD-TF (ΔI/ΔB)E of the doped Pani-film are directly connected to its low frequency capacitance, however, in the galvanostatic mode, the calculated MHD-TF (ΔE/ΔB)I confirms that the response is related to the induced electromotive force due to the high frequency modulation of the magnetic field.