bluuebunny/crossref_metadata_2025 huggingface dataset:
Creating Thin-Film Silicon on Flexible Substrates using Adhesive Bonding and Wet Etching
Authors: Song Shin-Da , Holl Susan L. , Colinge Cynthia , Byun Ki Y. , Hobart K. D. , Kub Fritz
Published: October 2008

A 4" silicon-on-insulator wafer was bonded to a flexible plastic substrate using indirect bonding to fabricate thin-film silicon on a flexible substrate. The bonded materials were annealed at 150oC for 48 hours. The bonding process created stress in the silicon (~20 MPa) at the interface due to thermal mismatch. Thin-film silicon was created by removing substrate material. The interfacial stress increased as the silicon was thinned. Relaxation of the stress resulted in residual defects in the silicon.
Bonding of Multiple Wafers for High Throughput LED Production
Authors: Sood Sumant , Wong Angela
Published: October 2008

High-brightness light emitting diodes (HB LEDs) are quickly gaining momentum as the next generation devices for technical and general lighting. HB LEDs are normally grown on compound semiconductor or sapphire substrates that are 2" to 4" in diameter. The device wafers are then bonded to CTE mismatched Si substrates. The bonding process requires the post bond cool-down rate to be low (<2oC/minute) thereby considerably increasing the bond cycle time. We have developed a production-worthy wafer bonding solution where multiple 2", 3" and 4" wafer pairs are simultaneously bonded in one process cycle. Up to an 8-fold increase in throughput can be realized with minimal investment since the process is performed with one bond tool.
Effect of Wafer Bonding and Layer Splitting on Nanomechanical Properties of Standard and Strained SOI Films
Authors: Tapily Kandabara , Baumgart H. , Gu Diefeng , Elmustafa Abdelmageed , Krause Michael , Petzold Matthias
Published: October 2008

The response to mechanical deformation of bonded strained Si-on-Insulator (sSOI) wafers was investigated by nanoindentation. Both the hardness and elastic moduli were determined for the Si film on the surface of the bonded composite SOI wafers, the buried SiO2 and the bulk silicon using the continuous stiffness method (CSM) XP Nano Instruments Nanoindentation tester. The measured hardness values for biaxial tensile strained sSOI films were found to be 9.23 GPa and for standard non-strained SOI films 9.36 GPa. The moduli are 101.2 GPa and 105.6 GPa respectively. The thin bonded Si film values were measured to be considerably lower in comparison with single crystal Si bulk values of 12.5 GPa and 160.0 GPa for hardness and modulus.
Impact of Thermal Processing on Silicon Wafer Surface Roughness
Authors: Shive Larry W. , Gilmore Brian L.
Published: October 2008

Very flat silicon wafers with nanometer scale roughness are important during semiconductor device patterning onto the wafer. Recent reports have shown that thermal processing at high temperature in H2 or H2-Ar mixtures may be used to reduce roughness of silicon wafers at short length scales such as 1- 10um. This paper reports the impact upon roughness of high temperature heat treatment in a diffusion furnace in mixtures of hydrogen and argon. Experiments show surface roughness is reduced during high temperature processing and is independent of argon or argon-hydrogen processing environment for length scales in the range of 0.1-100um.
Germanium Bonding to AL2O3
Authors: Baine Paul T. , Gamble Harold , Armstrong Brian , Mitchell S. J. N. , McNeill David , Rainey Paul , Low Yee , Bain Mike
Published: October 2008

Germanium has been bonded to both single crystal Al2O3 (sapphire) as well as fine grain Al2O3. A germanium to sapphire bonding energy of 3 J/m2 has been measured after a 200 oC bond anneal. Micro voids formed between the germanium/sapphire interface can be removed by employing an interfacial layer of silicon dioxide on either surface. Patterning the sapphire into a grid pattern prior to bonding creates an escape path for trapped gas or moisture allowing micro void free direct bonding to be achieved. Modifying the surface of the fine grain Al2O3 surface with a polycrystalline silicon deposition and polish creates a surface, having an rms roughness of 1.5nm(measured over a 250µm square area), suitable for bonding. Techniques employed in the germanium sapphire bonding can then be used in the bonding of fine grain Al2O3 to germanium.
Characterization and Qualification of Wafer-Bonded MEMS Devices
Authors: Knechtel Roy
Published: October 2008

In this paper characterization and qualification methods of wafer- bonded MEMS devices are introduced. The main focus is on stud pull tests for bond strength measurement in real MEMS chips, in combination with a statistical Weibull diagram evaluation. The stud pull test covers all strength-related aspects from wafer bonding and dicing as well as from the whole wafer process and final dicing. Based on the results of this test, it was possible to optimize the wafer bonding quality regarding strength, and subsequently it was used to qualify the reliability of different wafer bonding techniques in complete MEMS technologies. In addition, the hermeticity of the wafer-bonding interface was tested and qualified by assessing the functionality of MEMS devices requiring hermetic sealing of a low pressure or vacuum.
Mechanical Characterization and Micro Structure Diagnostics of Glass Frit Bonded Interfaces
Authors: Boettge Bianca , Dresbach Christian , Graff Andreas , Petzold Matthias , Bagdahn Joerg
Published: October 2008

In this paper, results of mechanical strength investigations for glass frit bonded components using tensile and micro chevron testing are presented. Specific attention is given to the formation of lead precipitates close to the glass-silicon interface which affects the strength properties and form reliability risks. Results of the accompanying SEM and TEM investigations suggest that the lead precipitation can be understood in terms of a redox reaction involving the oxidation of the Si wafer and can be reduced by appropriate intermediate layers forming a barrier between glass and silicon.
A Standard Method for Measuring Wafer Bond Strength for MEMS Applications
Authors: Allen Richard A. , Marshall Janet , Baylies Win , Read David , Delrio Frank , Turner Kevin T. , Bernasch Michael , Baghdan Joerg
Published: October 2008

A round robin, to provide precision and bias data for SEMI standard MS5-1107, Test Method for Wafer Bond Strength Measurements Using Micro-Chevron Test Structures, is underway. The precision and bias data, combined with experience in applying the test instructions included in MS5-1107, will provide the basis for an updated version of MS5. Measurements at the pilot lab have been completed and the round robin is on-going at six additional laboratories.
Low Temperature Bonding Using In-Situ Radical Activation
Authors: Rogers Tony , Aitken Nick
Published: October 2008

A tool for performing surface activation using radicals (RAD activation), followed by the subsequent, in-situ, low temperature bonding of wafers, was presented previously (1). This paper reports on the further characterization of the (RAD) tool and the importance of water vapour in the activation / bond chamber. The tool uses the diffusion of radicals across the wafer surfaces to activate those surfaces. Because the activation is performed in-situ in an aligner-bonder, the activated surfaces do not get the opportunity to adsorb any atmospheric contaminants between activation and bonding and this results in more reproducible interfaces from bond to bond. Results for various bonded wafers are presented in terms of bond quality and bond strength. These results demonstrate the importance of the wafer separation during the activation process, in order to minimize the process time, and the need for a controllable / variable source of H2O in the activation gas in order to maximize bond strength.
Hybrid Bonding (Plasma activation and Anodic bonding) for Vacuum Sealing
Authors: Yamauchi Akira , Kagami Johji , Okada Hironao , Suga T.
Published: October 2008

Low temperature bonding by means of plasma activated bonding has been proposed. However there are the following problems for the mass-production of devices. 1) Voids occur due to small particles remaining at the interface, 2) Low bond strength in case of bonding in a vacuum. In this article we introduce the 'Hybrid Bonding' method, a combination of plasma activation and anodic bonding, which may overcome the problems and be suitable for mass-production of MEMS devices.
Fabrication Process for Double Barrier Si-Based Quantum Well Resonant Tunneling Diodes (RTD) by UHV Wafer Bonding
Authors: Lee Taehun , Floresca Herman , Kang SukJune , Sim J.J. , Song K.H. , Kang Hee-Bok , Lee Bo-Young , Wallace Robert M. , Gnade Bruce E. , Kim Moon J.
Published: October 2008

Double barrier Si-based Resonant Tunneling Diode (RTD) structures were fabricated by ultra high vacuum (UHV) wafer bonding. 300 mm ultra thin body silicon-on-insulator (SOI) wafers with 10 nm top Si layers were developed and used for the integration of Si/SiO2((<3nm)/Si(<10nm)/SiO2(<3nm)/Si RTD structures. The dielectric oxide/Si interfaces characterized by Capacitance-Voltage (C-V) measurements were of good quality. The bonded oxide/Si interfaces characterized by high resolution transmission electron microscopy (HRTEM) were atomically sharp.
High-Precision Alignment for Low Temperature Wafer Bonding
Authors: Wang Chenxi , Taniyama Shingo , Wang Ying-Hui , Suga T.
Published: October 2008

A novel wafer-to-wafer alignment method is developed using centrosymmetric moiré gratings. Moiré fringes produced by the two centrosymmetric square gratings are highly sensitive with the misalignments and misaligned directions without requiring any external reference. Using two pairs of these moiré square gratings, misalignments of the bonded wafers are determined in X-Y-theta direction simultaneously on wafer scale. In our experiment, the misalignments in the order of +/-0.5 um in X-Y direction can be easily identified using a simple infrared (IR) microscope. Moreover, these moiré gratings are suitable for being secondary alignment mark to achieve high-precision alignment as well. And the alignment accuracy assisted by these moiré gratings can be further improved to nanometer range if processing errors for the fabrication of the square centrosymmetric gratings are reduced.
Photodefinable Polybenzoxazole as Interlevel Dielectric and Buffer Layer for GaAs HBT Technology
Authors: Yota Jiro , Ly Hoa , Barone Dragana
Published: October 2008

Polybenzoxazole (PBO) has been investigated and used as interlevel dielectric and buffer layer for GaAs hetero-junction bipolar transistor (HBT) technology. The polymer film is applied by spin-coating, and is photosensitive and photodefinable. These film characteristics allow the simplification of the process flow and allow the elimination of various steps that are typically used to define the vias, streets, and bonding pads. Additionally, this PBO film can be cured at low temperature (>250oC) and the resulting film has good characteristics against moisture absorption and is stable thermally. Furthermore, the film has good planarity and gapfill characteristics, and has excellent mechanical properties. Results show that GaAs device wafers fabricated with this film as interlevel dielectric has good electrical characteristics. When used as buffer layer, the PBO film is shown to be effective in mechanically protecting the underlying devices and interconnections. The use of photodefinable PBO will result in improvement in device quality and reliability, in addition to in significant reduction in capital and consumable cost, and reduction in cycle time of wafers manufactured. All the above characteristics make this PBO film to be well-suited as interlevel dielectric and buffer layer for and compatible with GaAs HBT technology.
InP-Based HEMTs Suitable for Ultra-High-Speed MMICs Fabrication
Authors: Hara Naoki , Takahashi Tsuyoshi , Ohki Toshihiro , Makiyama Kozo
Published: October 2008

We have developed InP-based high electron mobility transistors (HEMTs) suitable for fabricating ultra-high-speed MMICs. Scaling of both vertical and horizontal directions was investigated for enhancing transconductance, which enables us to realize high-speed characteristics without ultra-short-length gate electrodes. Parasitic capacitance that originated from interlayer dielectric films for interconnection was reduced by using a cavity structure, which was formed by removing the interlayer dielectric film around the gate electrodes. We successfully fabricated a 45-nm gate InP HEMT with a cut-off frequency of 517 GHz by employing the above technologies even after the interconnection. These results indicate that the device technology reported in this paper is suitable for fabricating MMICs operating at millimeter-wave frequency.
RF Sputter Deposition of Indium Oxide - Iron Oxide Films for Photoelectrochemical Hydrogen Production
Authors: Ingler William B. , Ong Grace , Deng Xunming
Published: October 2008

This project focuses on using indium oxide and iron oxide to make a protective thin film (transparent, conductive, and corrosion resistant, TCCR) for amorphous silicon based solar cells. From the work completed, the results indicate that samples made at 228oC, with 28 W of indium and 100 W of iron oxide, and a sputter deposition time of two hours produced optimal results. At 1.7 V, the best sample displays a maximum current density of 23 mA/cm2. Subsequently, an x-ray diffraction scan confirmed that indium oxide and iron oxide were produced.
Mesoscopic Transport in Undoped Heterostructures
Authors: Sarkozy Stephen J. , Das Gupta Kantimay , Sfigakis Francois , Farrer Ian , Ritchie David , Jones Geb , Liu Po-Hsin , Quach Helen , Pepper Michael
Published: October 2008

Fully Undoped Heterostructures, by means of being an extremely clean system, are ideal for studying transport in mesoscopic regions at ultra-low densities. At low temperatures, effects in two and one dimensions are seen which cannot be explained within the framework of non-interacting particles. The insight offered by induced devices highlights the aspects of theories which require modification to fully explain the physics of these complex regions and effects.
Enhanced Photoresponse of Hydrogen-Modified (HM)-n-TiO2 for Water Splitting Reaction
Authors: Frites Mourad , Shaban Yasser A. , Khan Shahed U.
Published: October 2008

Hydrogen modified n-type titanium oxide (HM-n-TiO2) thin film photoelectrodes were synthesized by thermal oxidation of Ti metal sheet (Alfa Co. 0.25 mm thick) in an electric oven and then hydrogen was incorporated electrochemically by hydrogen evolution on it under cathodic polarization. The photoresponse of the HM-n-TiO2 was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which is proportional to photocurrent density jp. The optimized electric oven-made n-TiO2 and HM-n-TiO2 photoelectrodes showed photocurrent densities of 0.2 mA cm-2 and 1.60 mA cm-2 respectively at measured potential of -0.4 V/Pt at illumination intensity of 100 mW cm-2 from a 150 Watt Xenon Lamp. This indicated an eight fold increase in photocurrent density at the same measured electrode potential. The band gap energy of HM-n-TiO2 was found to be 2.7 eV (459 nm) and a mid-gap band at 1.67 eV (742 nm) above the valence band was observed. These HM-n-TiO2 photoelectrodes were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Investigation and Fabrication of AlGaN/GaN MOS-HEMTs with Gate Insulators Grown by Photoelectrochemical Oxidation Method
Authors: Lee Ching-Ting , Huang Li-Hsien
Published: October 2008

AlGaN/GaN MOS-HEMTs with gate insulators directly grown using photoelectrochemical (PEC) oxidation method were investigated. The gate length and the gate width is 1 μm and 50 μm, respectively. The drain-source saturation current (VGS=0 V) and the threshold voltage of AlGaN/GaN MOS-HEMTs is 580 mA/mm and -9 V, respectively. The maximum extrinsic transconductance is 76.72 mS/mm operated at VGS=- 5.1 V and VDS=10 V. The forward breakdown voltage and reverse breakdown voltage is 25 V and larger than -100 V, respectively. When the VGS=- 60 V and 20 V, the leakage current was 102 nA and 960 nA, respectively. The low frequency noise characteristics were also measured and studied. The Hooge′s coefficient estimated at VGS=0 V. When VDS is 10 V and 2 V at frequency of 100 Hz, the Hooge′s coefficient is 1.25×10-3 and 5.69×10-4, respectively.
Effect of Laser Sources on the Structural Damage Mechanisms and Reverse-bias Leakages of Laser Lift-off GaN-based LEDs
Authors: Cheng Ji-Hao , Liao Cheng , Huang Ping-Wei , Wu YewChung Sermon
Published: October 2008

The frequency-tripled Nd YAG laser (355nm) and the KrF pulsed excimer laser (248 nm) were used to separate GaN from sapphire substrates. The laser damage mechanism of these two laser sources and effects on the reverse-bias leakages of GaN-based light-emitting diodes (LEDs) were studied.
Strain Relaxation Induced Micro-Photoluminescence haracteristics of a Single InGaN-based Nanopillar Fabricated by Focused Ion Beam Milling
Authors: Chiu ChingHua , Yu Peichen , Chen J.R , Yen H. H. , Kao C.C. , Kuo H. C. , Lu T.C. , Wang S.C. , Wu Y.R. , Yang H.W. , Yeh W. Y.
Published: October 2008

A free-standing nanopillar with a diameter of 300 nm, and a height of 2 μm is successfully demonstrated by focused ion beam milling. The measured micro-photoluminescence (μ-PL) from the embedded InGaN/GaN multiple quantum wells shows a blue shift of 68 meV in energy with a broadened full-width at half maximum, ~200meV. Moreover, the power-dependent μ-PL measurement confirms that the strain-relaxed emission region of the nanopillar exhibits a higher radiative recombination rate than that of the as-grown structure, indicating great potential for realizing high-efficiency nano devices in the UV/blue wavelength range.
Strain Relaxed GaN/InGaN Nanorod Light Emitting Arrays
Authors: Chen Liang-Yi , Wang Cheng-Yin , Chen Cheng-Pin , Cheng Yun-Wei , Ke Min-Yung , Huang JianJang
Published: October 2008

We present a practical top-down etch process to fabricate InGaN/GaN multiple quantum well nanorod structure. By using nature lithography to define nanostructure, and a space layer to prevent p-type contact from connecting n-type GaN, the nanorod light emitting diode array is realized. The quantum confine stark effect is suppressed in nanorod LEDs which is indicated by their nearly constant electroluminescence peak wavelength at the injection current range between 25mA and 100mA. Furthermore, Raman measurement confirms strain relaxation between lattice mismatch layers of such a nanostructure.
GaN MOSFETs with Large Current and Normally-off Operation
Authors: Niiyama Yuki , Kambayashi Hiroshi , Ootomo Shinya , Ikeda Nariaki , Nomura Takehiko , Kato Sadahiro
Published: October 2008

GaN is promising for high-power, high-temperature devices due to its large bandgap, high critical electric field, and high saturation velocity compared with Si and SiC. The MOSFET structure can be operated at a positive threshold voltage, namely the normally-off mode, which is preferable for power transistors in terms of fail-safe operation. In order to realize MOSFET operation, good interface quality at SiO2/GaN and low resistance in the n+-contact layer is strongly required. We have overcome these requirements by precise thermal control. Finally, we have fabricated GaN MOSFETs and have achieved more than 1 A operation in the normally-off mode at more than 250oC. The breakdown voltage was more than 1500 V.
Influence of the Structural and Compositional Properties of PECVD Silicon Nitride as a Passivation Layer for AlGaN HEMTs
Authors: Karouta Fouad , Krämer Mark , Kwaspen J J. , Grzegorczyk Andrzej , Hageman Paul , Hoex Bram , Kessels W. M. , Klootwijk Johan , Timmering Eugène , Smit Meint
Published: October 2008

We have investigated the influence of the structural and compositional properties of silicon nitride layers on the passivation of AlGaN/GaN HEMTs grown on sapphire substrates by assessing their continuous wave (CW) and pulsed current-voltage (I-V) characteristics. We have looked at the effect of various PECVD parameters like gas composition (SiH4/NH3 ratio and ammonia-free SiNx), process pressure, plasma power and deposition temperature. The best SiNx layer is Si-rich and has a refractive index of 2.01, an extinction coefficient of 0.03 at 3.44 eV and an optical band gap of 2.87eV. The best device performance was only achieved when the optimized SiNx layer was used in conjunction with a low-power Ar-plasma after the metallization of the ohmic contacts and cleaning using an ammonia dip just before the Schottky gate metallization. The latter treatment accounted for a substantial reduction of the gate and drain leakage currents densities from 6.7 mA/mm to 400 μA/mm.
AlGaN/GaN Transistors and Circuits
Authors: Bardwell Jennifer , Lester Tim , Tang Haipeng , Surridge Bob , Harrison Alan , Lau Andy
Published: October 2008

AlGaN/GaN transistors and circuits have been fabricated on semi-insulating SiC substrates. The process has been expanded to provide all the required elements of a full MMIC fabrication, including thin film resistors, MIM capacitors, and two levels of gold interconnect including air-bridge. Spiral inductors have been included in some designs. Large signal models of devices with various gate widths have been obtained, and a several experimental circuits with both microwave and digital functions, have been designed and measured.
High Performance GaN-based Light-emitting Diodes with Geometric GaN Shaping Structure
Authors: Liao Cheng , Wu YewChung Sermon
Published: October 2008

InGaN-GaN light emitting diodes (LEDs) with p-roughened surface and n-bowl structure were fabricated by low temperature growing, ICP etching, wafer-bonding, and laser lift-off technologies. Ni/Ag/Ni mirror was introduced on the n-bowl surface. It was found the light intensity of PRUB-LEDs with different bowl size are all higher than PR-LED. The intensity of PRUB-LED with 3 μm bowls was 2.33 times higher than that of the PR-LED.
Electrochemical Capacitor Performance in Energy Harvesting Applications
Authors: Miller John R. , Butler Sue
Published: October 2008

Many energy harvesting applications are now emerging to reduce fuel consumption and address long-term environmental concerns. Electrochemical capacitors have several important performance features that make them very attractive as the energy storage component in these applications. Capacitor features are identified and quantified.
Evaluation of DC Internal Resistance and Estimation of Power Characteristics of EDLC using the "Current-Rest-Method"
Authors: Yata Shizukuni , Mori Shiro , Satake Hisashi
Published: October 2008

Backed by attention to the power characteristics of energy storage devices in recent years, the DC internal resistance by "the Current-Rest-Method" (the C.R.M. resistance) has been proposed by Dr. S. Yata (1). In this paper, we focus the time-dependent C.R.M. resistance (Rt) at the first current-rest point in the discharge process (Point B), and we discovered that the discharging curve at various currents can be estimated using Rt, which corresponds well with the actual discharging curve.
Hybridation of Lead-Acid Batteries and Supercaps: A Mean to Gain in Electrical Performances and in Life Time
Authors: Mattera Florence , Colin Hervé , Lemaire-Potteau Elisabeth , Delaille Arnaud , Genies Sylvie , Merten Jens
Published: October 2008

The present study, conducted in the frame of the project SoS-PVi (Security of Supply PhotoVoltaic Inverter), results in the development of a multi-functional grid-connected PV inverter including as storage function a lead-acid + supercapacitor system. Two modes of operation are aimed: the supply of the energy during the short and long duration network faults and the reduction of the impact of the PV production on the network by storing in the batteries a part of the energy produced to move in the day the injection on the network and level the production. This paper presents the tests performed with the lead-acid + supercapacitor system in accordance with realistic use profiles.
Activated Carbon in Double Layer Capacitors
Authors: Kirk Donald W. , Jia Charles
Published: October 2008

Double layer capacitors, supercapacitors or ultracapacitors are of particular interest in the sustainable energy field because of the optimization role that they can play in providing a buffer between power and energy supply and demand. The cost per energy stored and the charge - discharge performance still require improvement for large scale implementation of the technology. In this work, the capacitance performance of an activated carbon from an inexpensive fluid coke source is reported. Two aspects were studied. The activated carbon capacitance was compared with and without sulfur impregnation. The effect of sulfur either increased the capacitance or did not contribute to capacitance depending on carbon preparation conditions. High temperature treatment of the sulfur impregnated carbons reduced capacitance
Combining Nanostructured Carbon Electrodes and Ionic Liquid Electrolytes to Develop New Electrochemical Capacitors
Authors: Lu Wen , Hartman Rachel , Qu Liangti , Dai Liming , Kulkarni Kapil , Carnahan David
Published: October 2008

Performance of electrochemical capacitors is largely determined by the properties of the electrodes and the electrolytes employed. In this work, we utilized carbon nanotubes to develop a range of nanostructured carbon electrodes and combined them with ionic liquid electrolytes to fabricate new electrochemical capacitors. Difference in the cost, preparation, and performance of these electrode materials allows us to achieve the optimal performance / cost value for the capacitors and to select a specific type of nanoelectrodes to fabricate capacitors for a particular application. Combing the highly conductive and electrolyte-accessible structures of these nanoelectrodes with the large electrochemical window of the ionic liquid electrolytes, the resultant capacitors have achieved superior performances over the current state-of-the-art electrochemical capacitor technology. Excellent safety-related properties of the ionic liquid electrolytes ensure superior safety and lifetimes for these new capacitors.
Evaluation of Composite Electronic Materials Based upon Single-Wall Carbon Nanotubes and Highly Charged Poly(aryleneethynylene)s for Supercapacitor Applications
Authors: Rosario-Canales Mariem R. , Deria Pravas , Kang Youn , Therien Michael , Santiago-Aviles Jorge
Published: October 2008

Although substantial improvement in capacitance, energy densities, and discharge times has been achieved for redox supercapacitors over the last several years, important challenges remain. These include high series resistance which limits the ability to quickly discharge these devices, excessive heat generation, and the coupled thermoelastic strain field which tends to deform the device materials. High stability composites based upon conjugated polymers that wrap single-wall carbon nanotubes (SWNTs) provide a platform to develop materials that can broadly impact these issues. This work compares the performance of a new class of hybrid materials, polymer-wrapped SWNTs to established electroactive polymer-based anode and cathode material benchmarks of poly(3,4-propylenedioxythiophene) for the construction of supercapacitors. These polymer-wrapped SWNT composites exploit rigid, polyanionic poly(aryleneethynylene)s which provide unusual solubility and dispersion characteristics for carbon nanotubes in several solvents.
Electrochemical Performance of Iridium Oxide Thin Film for Supercapacitor Prepared by Radio Frequency Magnetron Sputtering Method
Authors: Liu Dong-Qiang , Yu Sung-Hun , Son Se-Wan , Joo Seung-Ki
Published: October 2008

IrO2 thin films were prepared by radio frequency (rf) sputteringtechnique, and the supercapacitive properties of the films werestudied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1 M LiNO3 electrolyte for the first time. The specific capacitance of the single IrO2 film electrode was calculated to be 293 F·g-1 at a scan rate of 5 mV·s-1for the sample prepared at room temperature.
Effects of Li Ion on Electric Double Layer Involving Ionic Liquid Electrolyte
Authors: Yamagata Masaki , Fukuda Yasutake , Tanaka Rie , Ishikawa Masashi
Published: October 2008

Origins of cathodic stability of an ionic liquid electrolyte, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) containing lithium tetrafluoroborate (LiBF4), are investigated mainly by applying electrochemical impedance spectroscopy for a glassy-carbon electrode interface. Its Helmholtz layer capacitance in the EMIBF4 electrolyte containing Li+ becomes much higher than that in neat EMIBF4 with increasing cathodic polarization. On the basis of such analyses as well as our hypotheses, a reasonable mechanism for the stabilizing effect induced by the Li salt addition is discussed.
Functional Electrolytes for Use in Non-aqueous EDLCs
Authors: Jackson Nicole M. , Payne Martin
Published: October 2008

In this work, we have examined the physical and electrochemical properties of electrolytes for non-aqueous electrochemical double layer capacitors (EDLCs) that are designed to fulfill select functional needs, namely in the areas of alternative salts and water scavenging additives. The results demonstrate that select alternative salts do show promise to increase conductivity in test capacitors while continuing to maintain other key critical performance goals. Preliminary results also have identified several select water scavenging additives that have been shown to preserve crucial performance characteristics in our test cells.
Electrocatalytic Deposition of Nanostructured Vanadium Oxide for Pseudocapacitors
Authors: Hu Chi-Chang , Huang Chao-Ming , Chang Kuo-Hsin
Published: October 2008

This work describes that vanadium oxide can be anodically deposited at potentials much more negative to oxygen evolution from aqueous VOSO4 solutions by adding H2O2. Vanadium oxide deposit with a 3D nanonetwork architecture has been successfully deposited from VOSO4 with the addition of H2O2. The X-ray photoelectron spectroscopic analyses reveal that this oxide deposit, mainly consisting of V(V) with minor amount V(IV), shows a hydrous nature (denoted as VOx.wH2O). The VOx.wH2O deposit exhibits ideal pseudocapacitive performances in 3 M KCl.
Novel Energy Storage System using Grapahite Cathode and Nb2O5 Anode
Authors: Park Gumjae , Nakamura Hiroyoshi , Lee Yun-Sung , Yoshio Masaki , Takano Koji
Published: October 2008

A novel energy storage system was developed using graphite and Nb2O5 for cathode and anode materials, respectively. This system exhibited a sloping voltage profile from 2.7 to 3.5 V during charging and presented a high operating voltage plateau between 1.5 and 3.5 V during discharging process. The adsorption of anions to the edge plane regions in graphite happened in the voltage region between 0.0 and 2.7 V, but anion intercalation into graphite occurred between 2.9 and 3.5 V.
Manganese Oxide Supercapacitor with Aqueous Hydrogel Electrolyte
Authors: Lee Kuang-Tsin , Wu Nick Nae-Lih
Published: October 2008

Two poly(acrylic acid)-based gel electrolytes have been characterized for their application to MnO2•nH2O supercapacitors. The gel polymer electrolytes (GPEs) consist of either poly(acrylic acid) or poly (acrylic acid)-co-poly(acrylamide) with 1 M KCl aqueous solution (weight composition, polymer : KCl : H2O = 9%: 6.7%: 84.3%). The GPEs show no fluidity, while possessing ionic conductivities in the order of 10-1S cm-1. The electrochemical performance of MnO2-GPE supercapacitors have been investigated, and compared with liquid electrolyte counterpart. While both GPEs can give high initial capacitance, the copolymer one gives remarkably enhanced cycled stability.
Enhancement of Pseudo-capacitive Behaviors of Birnessite Type Manganese Dioxide by Electrolyte Additive
Authors: Komaba Shinichi , Tsuchikawa Tomoya , Ogata Atsushi
Published: October 2008

The birnessite type manganese dioxide electrode was prepared by the electrochemical stimulation as we recently described. It showed 190 F g-1 in a Na2SO4 aqueous solution between -0.1 and 0.9 V vs. Ag/AgCl at 1 A g-1. The specific capacitance of birnessite was decreased by the manganese dissolution when the reduction and oxidation were repeated. By adding small amounts of Na2HPO4 or NaHCO3 into the electrolyte, the capacitance increased to 200 - 230 F g-1 and the manganese dissolution was successfully suppressed. Thanks to the additives, the birnessite demonstrated the much improved cycleability over > 1800 cycles.
Characterization of a New Type of Asymmetric Supercapacitors: LiMn2O4/MnFe2O4
Authors: Wu Nick Nae-Lih , Chen Yu-Hung
Published: October 2008

Nanocrystalline MnFe2O4 having a spinel structure with Mn and Fe ions randomly distributed over the tetrahedral and octahedral sites have been found to exhibit capacitive characteristics in organic electrolyte containing 1M LiPF6 in the mixture of ethyl carbonate + ethylene methyl carbonate. As characterized by cyclic voltammetry and in-situ synchrotron X-ray absorption spectroscopy, the material show reversible pseudocapacitance behavior over a potential window from 1.75V to 4.5 V versus Li/Li+ with a specific capacitance of ~125 F/g. Asymmetric supercapacitors consisting of LiMn2O4 cathode and MnFe2O4 anode and Li organic electrolyte has thus been developed and characterized for their electrochemical performance in a three- electrode configuration in order to independently reveal the behaviors of the battery cathode and pseudocapacitive anode.
Textural and Capacitive Characteristics of Pulse-Deposited Manganese Oxide Nanowires
Authors: Chang Kuo-Hsin , Hu Chi-Chang , Wu Yung-Tai
Published: October 2008

In this work, we report manganese oxide nanowires has been successfully prepared on graphite substrates in a pulse-rest deposition mode. In addition, the textural and capacitive properties of pulse-deposited manganese oxide nanowires will be systemically studied by XRD, SEM and CV analyses.
Microstructural effects on Charge Storage Properties in MnO2 based Electrochemical Supercapacitors
Authors: Ghodbane Ouassim , Pascal Jean-Louis , Favier Frédéric
Published: October 2008

The present work provides a detailed study on the charge storage properties in MnO2 based electrochemical capacitors. Various crystallographic forms of MnO2 were investigated including pyrolusite, ramsdellite, cryptomelane, todorokite, birnessite, buserite and spinel. Prepared products have been characterized by XRD, SEM and BET. SEM photomicrographs revealed different surface morphologies depending on the prepared MnO2 form. According to BET measurements, surface areas vary from 29 m2/g for the cryptomelane to 156 m2/g for the spinel form. Electrochemical performances have been evaluated and commented regarding microstructural arrangements: 1D tunnels, 2D layers or 3D interconnected channels. Specific capacitances were found to decrease in the following order: spinel > birnessite > buserite > cryptomelane > ramsdellite > Ni-todorokite > pyrolusite or regarding microstructures with 3D > 2D > 1D.
Controlled Structure of Zinc Oxide by Means of Side Flow Type MOCVD
Authors: Yoshii Naoki , Nakamura Atsushi , Hosaka Shigetoshi , Temmyo Jiro
Published: October 2008

We have demonstrated that the ZnO deposited on sapphire (11-20) substrate is controlled to various structures by side flow type MOCVD at high temperature (above 973 K). We found that the crystal quality of ZnO having film structure is better than that of ZnO nanorod although they are fabricated under the same temperature condition. Also, in the case of ZnO nanorod, it is found that its crystal quality improves dramatically at higher temperature (1073 K).
Review of Characterization of ZnO by Spectroscopic Ellipsometry
Authors: Bondaz Alexis , Kitzinger Laurent , Defranoux Christophe
Published: October 2008

Spectroscopic Ellipsometric (SE) is a non contact, non destructive optical characterization technique which allows the precise determination of the refractive indices and thicknesses of thin films. Very sensitive to any optical contrast, S.E. is now also being applied to the characterization of organic materials such OLED or for a range of Solar Cells that require thin films; all parameters (complex refractive index and thickness) of each layer can be obtained from one single measurement. In this paper we will focus on the determination of the thickness and refractive index of ZnO. We will also demonstrate how a SE measurement in different spectral range can give access to different properties of the ZnO & TCO's layers such as electrical properties (resistivity, resistance) or doping differentiation. We will introduce the SE measurement of encapsulated sample through the back side of the substrate and the extration film's resistivity.
ZnO Nanostructures: From a Single Nanowire to Solar Cells
Authors: Chen Chun-Wei , Chen Kuei-Hsien , Wu Jih-Jen , Pong Way-Faung , Su Wei-Fang , Chen L-C.
Published: October 2008

In this article, surface and interface properties of 1-D ZnO nanostrutcures from the fundamental optical properties of a single ZnO nanorod to the application in photovoltaics will be presented. In the first part, optical and vibrational properties of a single ZnO nanorod will be investigated by cathodoluminescence (CL) and photoluminescence (PL) spectroscopy and confocal Raman spectroscopy. The anomalous energy shift in the emission spectra of individual nanorods with sizes beyond the quantum confinement regime was observed, which is mainly due to the enhanced surface effect in nanostructures (1). In addition, the interplay between the local phonon behavior and geometric anisotropy was revealed by Raman mapping images of an individual nanorod (2). In the second part, the optoelectronic properties at the interfaces between ZnO nanorods and conjugated polymer will be addressed, which represents the potential application in photovoltaics and photodetectors. Through interfacial nanostructuring, the photovoltaic performance can be largely improved due to the enhanced efficiency in charge separation and transport (3,4) at interfaces.
Pulsed Laser Deposited ZnO for Thin Film Transistor Applications
Authors: Bayraktaroglu Burhan , Leedy Kevin
Published: October 2008

The film growth conditions were optimized for pulsed laser deposited ZnO thin films for high performance field effect transistor applications. Transistors fabricated on Si and GaAs substrates with various gate lengths and gate widths and demonstrated current on/off ratios better than 1012, current density of >700mA/mm, sub-threshold gate voltage slope of 109mV/decade, current gain cutoff frequency of 500MHz, and power gain cutoff frequency of 400MHz (2um gate device).
Plasma-Enhanced Chemical Vapor Deposited SiNx and SiO2 Passivation Effects on ZnO Heterojunction Light Emitting Diodes
Authors: Wang Yu-lin , Kim H. S. , Norton David P. , Pearton Stephen J. , Ren F.
Published: October 2008

ZnO heterojunction light emitting diodes (LEDs) were passivated by plasma-enhanced chemical vapor-deposited SiO2 and SiNx. Post-dielectric deposition annealing was critical in obtaining good LED electrical and optical characteristics. No diode characteristics or light emission were observed unless the structures were annealed at 350 {degree sign}C after fabrication. Annealed diodes showed band-edge electroluminescence (385 nm) and a broad defect band with a peak at 930 nm at room temperature. The SiO2 and SiNx had very different passivation effects in terms of the electrical and electro-luminescence characteristics of the LEDs. After annealing, the SiO2 passivated ZnO LEDs showed diode IV characteristics and emitted light. However, the annealed SiNx-passivated ZnO LEDs showed leaky diode characteristics and no light emission. We attribute these differences to the role of hydrogen on the LEDs.
Fabrication and Characterization of Semiconducting ZnO nanofiber for Advanced Environmental Sensing
Authors: Zyung Taehyoung , Lee Su-Jae , Park Jin-Ah , Moon Jaehyun
Published: October 2008

Nanostructured semiconducting metal oxides offer an extremely high surface/volume ratio which have detecting sensitivity of part per million and even below, dynamic range and decrease the response time by more than 10-fold in comparison with thin film materials. Motivated by the recent development in fabricating and synthesizing nano-sized metal oxides, we have used an electrospinning method to produce semiconducting ZnO nanofibers for advanced environmental sensing. ZnO/PVP composite fiber mats were directly electrospun onto a SiO2/Si at 120oC, then calcined at 600oC. Polycrystalline wurtzite ZnO nanofibers of diameter in 35~70 nm were obtained. The CO gas sensing performances have been evaluated in a CO concentration range of 10~25 ppm. The resistances of ZnO nanofibers were observed to decrease upon exposure to CO. This is attributed to the reducing nature of CO, which reacts with O- to release an extra electron
ZnO Nanostructures and Thin Layers for Device Applications
Authors: Bakin A. , Wagner Alexander , Schlenker Eva , Postels Bianca , Al-Suleiman Mohamed , Behrends Arne , Elshaer Abdel-Hamid , Petukhov Vladimir , Waag A.
Published: October 2008

An overview of our nanostructures and thin layers fabrication technologies including MOCVD, vapour phase transport, MBE, chemical growth, electrodeposition is presented. The developed technologies provide control on the nanopillar characteristics, and still leaving the self-organisation mechanism untouched. Also fabrication of complicated heterostructures like quantum wells both as epitaxial layers or embedded into nanopillars was demonstrated. First results of the device applications of ZnO nanostructures as well as implementation of alternative ZnO nanostructures like nanopowders are discussed.
Germanium for High Performance MOSFETs and Optical Interconnects
Authors: Saraswat Krishna , Kim Donghyun , Krishnamohan Tejas , Kuzum Duygu , Okyay Ali K. , Pethe Abhijit , Yu Hyun-Yong
Published: October 2008

It is believed that to continue the scaling of silicon CMOS innovative device structures and new materials have to be created in order to continue the historic progress in information processing and transmission. Recently germanium has emerged as a viable candidate to augment Si for CMOS and optoelectronic applications. In this work we will first review recent results on growth of thin and thick films of Ge on Si, technology for appropriate cleaning of Ge, surface passivation using high-κ dielectrics, and metal induced crystallization of amorphous Ge and dopant activation. Next we will review application of Ge for high performance MOSFETs. Innovative Si/Ge MOS heterostructures will be described with high on current and low off currents. Finally we will describe optical detectors and modulators for on-chip and off-chip interconnect. Successful integration of Ge on Si should allow continued scaling of silicon CMOS to below 22 nm node.
Si and SiGe Epitaxy in Perspective
Authors: De Boer Wiebe B.
Published: October 2008

Fifty years of Si and SiGe epitaxy in the semiconductor industry and twenty-five since the conception of the present generation of industrial epi reactors suffice to justify a review of the evolution and the status of the technology. Although there has been very little change in the reactor design, the epi process progressed significantly. The strengths and weaknesses of the current technology are discussed with an emphasis on possible improvements.
Stress Manipulation with Strained-Silicon Directly (SSOI) on Insulator
Authors: Thean Aaron
Published: October 2008

The stress sensitivity of SSOI substrate offers a unique material platform for strain manipulation. Base on patterning and device processing, new opportunities to engineer the metastable stress for planar and other novel device structures are possible. In this presentation, the strain stability of SSOI devices are discussed and how mixing of uniaxial and biaxial strain can be achieved to improve devices for CMOS operation.
High Hole Mobility SGOI Substrates Obtained by the Germanium Condensation Technique
Authors: Souriau Laurent , Nguyen Tuan , Augendre E. , Loo Roger , Terzieva Valentina , Caymax Matty , Cristoloveanu Sorin , Meuris Marc , Vandervorst Wilfried
Published: October 2008

Thin SGOI substrates with Ge content from 42 to 93% have been produced by the Ge condensation technique and full structural characterization has been carried out. In a second step, the electrical properties of these substrates have been analyzed by the pseudo-MOSFETs technique which allowed the determination of the carrier low field mobilities as well as the density of fixed charges in the buried oxide (BOX) and the density of interface traps at the BOX-SiGe film interface. Optimization of intermediate anneals in argon during the condensation process has made the production of high crystalline quality and high mobility substrates possible (up to 400 cm2/Vs for a 93% SGOI). Opposite trends were observed for holes and electrons: while the hole mobility is increasing with increasing Ge content, the electron mobility decreases. Moreover, the density of interface traps and the density of oxide charges were found to increase with increasing Ge content.
Simulation of <110> nMOSFETs with a Tensile Strained Cap Layer
Authors: Bufler Fabian , Heinz Frederik O. , Tsibizov Alexander , Oulmane Mohamed
Published: October 2008

The on-current (Idsat) enhancement in process-simulated <110> nMOSFETs by a tensile strained cap layer is investigated by mechanical stress and Monte Carlo (MC) device simulation. Our MC model is based on an improved semi-empirical analytical two-band model for electrons. This model is found to compare favorably to pseudopotential MC results with some underestimation of the on-current improvement. The MC simulations yield Idsat gains of around 20 % and 10 % for a 60 nm thick cap layer with 2 GPa and 1 GPa intrinsic stress, respectively, with decreasing tendency upon scaling. These current gains are significantly higher than the gains predicted by drift-diffusion simulation with the linear piezoresistance model.
Strain Technology under Metal/High-k Damascene-Gate Stacks
Authors: Wakabayashi Hitoshi
Published: October 2008

Strain technology under metal/high-k damascene-gate stacks is discussed. It is estimated from stress simulation that compressive stresses for pMOSFETs with compressive stress-liners of SiN film and eSiGe are enhanced by damascene-gate process. Moreover, it is confirmed by UV-Raman spectroscopy in plane view that the compressive stress is considerably enhanced just after dummy-gate removal step, especially for smaller gate length. On the other hand for nMOSFETs, tensile stresses even by top-cut tensile stress-liners of SiN film are slightly enhanced by damascene-gate process. Therefore, high drivability of high-performance CMOS devices with gate length of 40 nm are achieved by not only thinner Tinv of 1.4 nm but also higher transconductance.
Reactive Ion Etch of Si3N4 Spacers High Selective to Germanium
Authors: Altamirano Efrain , Kunnen Eddy , De Jaeger Brice , Boullart Werner
Published: October 2008

The plasma etching of Si3N4 spacers selective to germanium with less than one nanometer recess in a CH3F/CF4/O2 mixture has been studied. The X-Ray Photoelectron Spectroscopy, Angle Resolved X-ray Photoelectron Spectroscopy, Transmission Electron Microscopy, Ellipsometry and Mass Metrology analyses suggest that the oxidation of the germanium top layers is the key parameter to achieve a high selectivity during the Si3N4 spacer patterning.