bluuebunny/crossref_metadata_2025 huggingface dataset:
Charge Trapping in HfYOx Gate Dielectrics on Strained-Si
Authors: Majhi Bibhas , Mahata Chandreswar , Maiti C.K.
Published: September 2009

HfYOx gate dielectric has been deposited on strained-Si/Si0.8Ge0.2 by RF co-sputtering of HfO2 and Y2O3 targets. Chemical and electrical properties have been demonstrated by x-ray photo electron spectroscopy (XPS), capacitance-voltage (C-V) and leakage current (I-V) characteristics. The reliability characteristics of HfYOx gate dielectric stacks on strained-Si/Si0.8Ge0.2 have been investigated under different field (2.3-6MV/cm) and constant current stress (10-25mA/cm2) of different amplitude and fluence in order to analyze the degradation of oxide as a function of stress parameters. Oxide trap charge and trap centroid location have been analyzed after constant current stressing.
Surface Generation-Recombination Processes of Gate and STI Oxide Interfaces Responsible For Junction Leakage on SOI
Authors: Liu Yong , Koldyaev Victor
Published: September 2009

Carrier generation-recombination at the top, corner and trench surfaces of silicon-on-insulator (SOI) diode bodies have been studied using the standard gated-diode methodology and new test structures with independent trench-side gates. The influences of top or trench gate voltage, temperature and junction bias have been elucidated. Four distinct diode current peaks are observed during top-gate voltage sweeps. Qualitative analysis has assigned these peaks to surface recombination at the different surface areas of SOI bodies. The coexistence of multiple recombination current peaks might be related to silicon faceting at top trench corners. During top-gate voltage sweeps, STI-gate voltage causes a larger recombination current peak shift for interface traps at the SOI trench corners and walls than those at top SOI interface. A new model involving an oxide trap within the STI oxide has been proposed to interpret the random telegraphic signal (RTS) noise of a gated-diode at high carrier injection and temperature.
Quantitative Estimation of Strained Si/SiGe Hetero Structure Using C-V Characteristics of Strained Si MOS Capacitors
Authors: Inagaki Mitsuhoro , Matsumoto Satoru
Published: September 2009

A plateau observed in the quasi-static C-V (QSCV) curve of MOS capacitors on the strained Si/relaxed SiGe epitaxial wafers was used as a quantitative estimation of the strain. There is a linear relationship between the strength of plateau and the Raman shift of Si-Si 520.0 cm-1. It suggests that plateau in C-V curve can be used as a quantitative index of the strained Si/SiGe heterostructures.
Probing the Strain States in Nanopatterned Strained SOI
Authors: Moutanabbir Oussama , Reiche M , Hähnel A , Erfurth W , Naumann F , Petzold M , Goesele U
Published: September 2009

Using strained SOI as a strategy to enhance the performance of Si-based electronic devices raises fundamental questions about the stability of the strain during different processing steps. In this work, we elucidate the influence of nanoscale pattering, a crucial step in device fabrication, on the strain states. UV micro-Raman and high resolution transmission electron microscopy were employed to quantify the strain in the strained layers. Post-patterning strain in different nanostructures was evaluated by UV micro-Raman. Our data demonstrate that the formation of free surfaces upon pattering leads to a partial relaxation of the strain. The extent of the relaxation was found to depend on the lateral dimension and the geometry. A detailed mechanistic picture is presented based on 3D finite element simulations
Controlling Copper ECD Processes by Early Fault Detection and Diagnosis Using In-situ Electrochemical Sensor Coupled with Pattern Recognition Chemometrics
Authors: Jaworski Aleksander , Wikiel Hanna , Wikiel Kazimierz
Published: September 2009

A system for plating bath process control was developed utilizing a novel approach that combines advanced electroanalytical methods with various statistical data analysis techniques based on chemometric factor analysis. The electroanalytical techniques employed, including DC- and AC-voltammetry, were designed to provide a response strongly affected by the presence of specific contaminants while being practically insensitive to the varying concentrations of deliberately added bath constituents. The shape differences between deformed and training set voltammograms were quantified using various outlier-detection chemometric techniques. The specificity of the response to the presence of a likely contaminant combined with multi-parameter quantification of its presence enabled not only early-fault detection but also its diagnosis, therefore automating the troubleshooting process.
Studies on Galvanic Corrosion on Floating and Grounded Bondpads in Wafer Fabrication
Authors: Hua Younan , Ping Lee Yuan , Rao Nistala R. , Qinghua Tian
Published: September 2009

Galvanic corrosion is well known to impact the quality of microchip Al bondpads. In this paper, we will further study the characteristics of galvanic corrosion and understand why galvanic corrosion is more serious on the floating or non-grounded bondpads as compared to the grounded Al bondpads. A phenomenological model of the Al pad corrosion, based on the oxidation-reduction reactions, will be invoked so as to explain why the floating pads with thinner Al oxide are more likely to suffer galvanic corrosion. Experimental data from cross-sectional TEM investigations provide the evidence of Al oxide thinning in the floating pads as compared to the non-floating or grounded Al bondpads. We recommend that during the initial process or recipe optimization DOE(s) (design of experiments) in the far-backend of line (FBEOL) one may use short-loop wafers with floating pads as they represent the 'worst-case-scenario', insofar as galvanic corrosion is concerned.
Investigation on Particle Generation Mechanism during Dichlorosilane-Based WSi Deposition Process
Authors: Oh Myeonghun , Kim Jaungjoo , Kim Jinsung , Yang Jichul , Lee Soocheol , Kim Taesung
Published: September 2009

Semiconductor industry faces a continuous challenge to increase the production yield by eliminating defect sources. In this paper, generation of typical defect during dichlorosilane-based WSi2 deposition process is systematically evaluated. The root cause analysis using tape sampling test and parts analysis revealed that the source of silicon particles during the particle generation is due to Vapor-Liquid-Solid(VLS) mechanism. The particle generation according to gas flow rate, susceptor material, susceptor structure were studied systematically. As a result, we found that silicon component particle generation could be suppressed by AlN Coating susceptor with revised structure.
Poly Si TFT on Microsheet
Authors: Won Sunghwan
Published: September 2009

In this study, we used thin flexible glass of 75 um in average thickness as a substrate to fabricate poly-Si TFT's. Glass substrates are so thin that they can be bent to radius of curvature as small as 3 inch. Glass substrate, we used, is borosilicate glass, thus barrier layers, SiNx fooled by a SiO2 layer, were deposited on both sides of glass substrate to suppress the out-migration of unwanted glass constituents from the glass into the semiconductor during processing. We fabricated Poly Si TFT on this substrate and investigated characteristics of the TFT.
Characterization of SiGe/Si Quantum Dot Grown by using APRPCVD
Authors: Kim Taek Sung , Jeong Mi Ra , Mun Nan Ju , Kil Yeon-Ho , Kim Jan-Di , Jeong Tae Soo , Kang Sukil , Kim Sang Hoon , Choi Chel-Jong , Shim Kyu-Hwan
Published: September 2009

We have investigated the characterization of SiGe/Si quantum dot (QD) structures grown directly onto Si (001) substrates using atmospheric pressure reduced pressure chemical vapor deposition (APRPCVD) system in an ASM Epsilon One. The structural properties of the SiGe/Si QD were investigated using X-ray diffraction (XRD), SEM and TEM. The optical properties of the SiGe/Si QD were investigated using Raman spectroscopy and photocurrent (PC) measurement. The transition peaks related to the QD region observed in the PC spectrum were preliminarily assigned to electron-heavy hole (e-hh) and electron-light hole (e-lh) transitions.
Confinement Effect on CdTe
Authors: Frausto Reyes Claudio , Molina-Contreras J. R. , Pérez Ladrón de Guevara Héctor , Medel Ruiz Carlos Israel , López Álvarez Yadira Fabiola
Published: September 2009

Quantum confinement effects on the first LO phonon mode in CdTe due to the roughness surface are studied using Raman spectroscopy. Our findings suggest that the sharper experimental Raman pick obtained with an excitation wavelength near the E0 transition of CdTe due the roughness surface can be explained by a confinement effect and that the right line wing of the experimental line shape for a smooth zone cannot be ascribed to the first LO and TO phonon CdTe
High Depth Resolution Depth Profile Analysis of Ultra Thin High-κ Hf Based Films using MEIS Compared with XTEM, XRF, SE and XPS
Authors: Van den Berg Jaap , Reading Michael A. , Parisini Andrea , Kolbe Michael , Beckhoff Burkhard , Ladas Spyros , Fried Miklos , Petrik Peter , Bailey Paul , Noakes Tim , Conard Thierry , De Gendt Stefan
Published: September 2009

Nanometre thin high-k hafnium oxide (HfO2) layers combined with a sub-nm SiO2 layers or Hf silicate have become Si compatible gate dielectrics. Medium energy ion scattering (MEIS) analysis has been applied to a range of such MOCVD grown HfO2/SiO2 and HfSiOx(60%Hf)/SiO2 gate oxide films of thickness between 1 and 2 nm on top of Si(100), before and after decoupled plasma nitridation (DPN). MEIS in combination with energy spectrum simulation provides quantitative layer information with sub-nm resolution on these layer structures and their atomic composition that is in excellent agreement with a) the as grown layer parameters and b) results obtained from techniques, such as SE, XPS, XRF and XTEM. MEIS analysis of a metal gate, high-k TiN/Al2O3/HfO2/SiO2/Si stack shows the interdiffusion, after thermal treatment, of Hf and Al from the caplayer, which was inserted to modify the metal gate work function.
Effect of High-temperature Annealing on Evaporated Silicon Oxide Films: A Spectroscopic Ellipsometry Study
Authors: Szekeres Anna , Vlaikova Emilia , Lohner Tivadar , Petrik Peter , Cziraki Agnes , Zlobin S. , Shepeliavyi P.
Published: September 2009

Silicon oxide films, vacuum evaporated and annealed in Ar atmosphere at a temperature of 1000 and 1100ºC have been studied by multiple-angle spectroscopic ellipsometry (SE) in the spectral range of 280-820 nm. The thickness, complex refractive index and composition of the films have been determined from the SE data analysis, performed with multiple-layer optical models and applying the Bruggeman effective medium approximation theory. The SE results have revealed that during annealing at 1000oC the Si clusters with volume fraction of ~ 14 % crystallize in the substoichiometric SiO1.61 matrix, while annealing at 1100oC transforms the oxide structure to a fully stoichiometric SiO2 with embedded nc-Si clusters with enhanced volume fraction of 22%. The TEM micrographs visualized the Si crystallites, which have random distribution in the amorphous oxide matrix and an average size of 3 nm.
Improved TEM Sample Preparation by Low Energy FIB for Strain Analysis by Convergent Beam Electron Diffraction
Authors: Balboni Roberto , Borionetti Gabriella , Moiraghi Luigi , Vaccari Giuseppe , Polignano Maria Luisa , Carnevale Gian Pietro , Cazzaniga Francesco , Mica Isabella , Sammiceli Francesca
Published: September 2009

The application of the focused ion beam (FIB) to the preparation of thin lamellae of Si-based samples for strain analysis by means of convergent beam electron diffraction (CBED) was investigated. The crystal damage induced by the ion beam at the sample surface is expected to influence the pattern quality strain analysis too. Repeatable results in the strain measurements were obtained only if a low energy (5 KeV) finishing step was used in the sample preparation. The strain measurement results obtained in patterned structures with different strain amount were also compared with the ones calculated using a commercial process simulator and with electrical measurements performed on the final devices.
Remote Plasma Atomic Layer Deposition of Co3O4 Thin Films
Authors: Donders Merijn E. , Knoops Harm , Van de Sanden M. C. , Kessels W. M. , Notten Peter
Published: September 2009

Cobalt oxide has been deposited with remote plasma ALD over a wide temperature window (100 - 400 {degree sign}C), using CoCp2 as cobalt precursor and with a remote O2 plasma as oxidant source. This novel combination resulted in the deposition of high density (6.2 g/cm3), stoichiometric Co3O4 with an electrical resistivity between 0.5 and 5.3 Ohm cm. Several merits have been identified for this process. Compared to the literature, the temperature window was widened to 100 - 400 {degree sign}C and the growth per cycle was higher at 0.05 nm/cycle, almost independent of the substrate temperature. Investigation of the material properties revealed cubic Co3O4 films with a preferential (111) direction for all temperatures with an increasing crystallinity with temperature. Furthermore, the plasma assisted process resulted in smooth Co3O4 films with a roughness of {less than or equal to} 1 nm for all substrate temperatures and film thicknesses (5 - 65 nm) investigated.
Structures, Properties and Applications of Functional Thin Films by ALD
Authors: Choy Kwang-Leong
Published: September 2009

This paper gives an overview of the use of Atomic Layer deposition (ALD) technique for the emerging and non mainstream ALD applications. These include a special focus on ALD fabrication of multifunctional protective oxide thin films, and textured thin films for electrical, optoelectronic devices, as well textured templates for the cost-effective growth of highly oriented nanowires for light emitting diodes (LED), field-effect transistor (FET) and catalysts with high activity and electivity.
Modeling and Characterization of ALD Grown ZnO Nanotubes and their Application to Sub-Micron Devices
Authors: Abdel-Fattah Tarek M. , Gu Diefeng , Baumgart Helmut , Bajpai Ritu , Zaghloul Mona
Published: September 2009

Characteristic properties and dimensions of ZnO nanowires grown by ALD and template technology have been used to model a nanowire into a fixed-fixed beam structure using conventional microelectromechanical systems (MEMS) design techniques. The frequency response of the structure as a result of piezoelectric actuation has been studied. Percentage error between the simulation and theoretical model has been found to be 0.97%.
The Benefits of Atomic Layer Deposition in Non-semiconductor Applications; Producing Metallic Nanomaterials and Fabrication of Flexible Display
Authors: Kim Hyungjun , Kim Woo-Hee , Lee Han-Bo-Ram , Lim S.J.
Published: September 2009

Atomic layer deposition (ALD) is a promising deposition technique for nanoscale device fabrication due to its great benefits including excellent conformality, atomic scale thickness control, high quality deposition at low growth temperature, and large area uniformity. In this presentation, we will present a couple of examples for novel applications of ALD; metallic nanomaterial fabrications combined by nanotemplate utilizing the excellent conformality of ALD and fabrication of driving devices for transparent flexible displays utilizing the ability of ALD to produce high quality materials at low growth temperature. These examples manifest the benefits of ALD in the near future industry.
Formation of Silicide Nanowires by Annealing of Atomic Layer Deposition Cobalt/Silicon Core-Shell Nanowires
Authors: Lee Han-Bo-Ram , Heo Kwang , Hong Seunghun , Kim Hyungjun
Published: September 2009

Co/Si core-shell nanowires (NWs) were fabricated by using highly conformal thermal atomic layer deposition (TH-ALD) of Co and the formation of Co silicide NWs by annealing was investigated. When Co/Si core-shell NWs were annealed without capping layer, no Co silicide was observed due to oxygen contamination. To prevent oxygen contamination, in situ TH-ALD Ru was used for capping layer utilizing its excellent conformality suitable for 3-D nanostructures as well as thermal stability. The scanning transmission electron spectroscopy analysis showed Si NWs are perfectly wrapped by TH-ALD Ru/Co films, resulting in the formation of Ru/Co/Si core-shell NWs. By annealing Ru/Co/Si core-shell NWs, CoSi2 was formed above Ta = 800 {degree sign}C. This silicidation by using TH-ALD Co and Ru can be effectively used for the fabrication of future nanoscale devices.
Advanced Precursor Development for Sr and Ti Based Oxide Thin Film Applications
Authors: Katamreddy Rajesh , Wang Ziyun , Omarjee Vincent , Rao Pallem V. , Dussarrat Christian , Blasco Nicolas
Published: September 2009

In this work, we evaluated novel Sr and Ti precursors for atomic layer deposition application. Traditional Sr precursor Sr(thd)2 is a solid with very low vapor pressure, high melting point, and requires high temperature oxidation for efficient carbon removal.. In comparison, bulky cyclopentadienyl based Sr compounds display high vapor pressures, low melting points, reactivity with water and high ALD growth rates. We also evaluated the effect of various stabilizing adducts on the properties of Sr cyclopentadienyl precursors and on the SrO ALD process. Sr precursors studied include AbsoluteSr Sr(iPr3Cp)2, HyperSr.THF Sr(iPr3Cp)2.2THF, HyperSr.DME Sr(iPr3Cp)2.DME, StarSr.THF Sr(Me5Cp)2.THF and StarSr.DME Sr(iPr3Cp)2.DME. Novel Ti precursors like PrimeTi (Ti(MeCp)(OMe)3), StarTi (Ti(Me5Cp)(OMe)3), TyALD (TiCp(NMe2)3) and StarTyALD (TiMe5Cp(NMe2)3) developed using heteroleptic chemistry are evaluated for TiO2 ALD. Finally, compatibility of the novel HyperSr.THF along with Ti precursors such as PrimeTi and StarTi in terms of composition tunability and material properties for STO ALD are studied.
Low Temperature Plasma-Enhanced Atomic Layer Deposition of Metal Oxide Thin Films
Authors: Potts Stephen E. , Van den Elzen Luc R. , Dingemans Gijs , Langereis Erik , Keuning Wytze , Van de Sanden M. C. , Kessels W. M.
Published: September 2009

Many reported ALD processes are carried out at elevated temperatures (> 100 ºC), which is problematic for temperature-sensitive substrates. Plasma-enhanced ALD routes may provide a solution, as the ALD temperature window can be extended to lower deposition temperatures. As such, the plasma-enhanced ALD of aluminium oxide, titanium dioxide and tantalum oxide has been investigated at 25-150 ºC using trimethylaluminium, titanium isopropoxide, methylcyclopentadienyltris(isopropoxy)titanium and pentakis(dimethylamido)tantalum respectively as precursors. An oxygen plasma was employed as the oxygen source. We have demonstrated metal oxide thin film deposition at temperatures as low as room temperature and compared the results with corresponding thermal ALD routes to the same materials.
Atomic Layer Deposition of GdHfOx Thin Films
Authors: Adelmann Christoph , Pierreux Dieter , Swerts Johan , Rosseel Erik , Shi Xiaoping , Tielens Hilde , Kesters Jurgen , Van Elshocht S. , Kittl Jorge
Published: September 2009

GdHfOx thin films were deposited by atomic-layer deposition (ALD) using Tris(isopropyl-cyclopentadienyl)Gadolinium [Gd(i-PrCp)3] and HfCl4 in combination with H2O as oxidizer. Growth curves show nearly ideal ALD behavior. The growth per cycle is found to be 0.55 Aå, independent of Gd/(Gd+Hf) composition in the studied range. This indicates that the amount of HfO2 deposited during an HfCl4/H2O cycle is identical to the amount of Gd2O3 deposited during a Gd(i-PrCp)3/H2O cycle. The film composition can therefore be deduced from the HfCl4/Gd(i-PrCp)3 cycle ratio. The crystallization of GdHfOx with Gd/(Gd+Hf) contents between 9% and 30% was studied. All films crystallize into a cubic/tetragonal HfO2-like phase during spike annealing at 1050{degree sign}C. Cu-bic/tetragonal phases are also observed after laser annealing for 1.5 ms up to 1300{degree sign}C, demonstrating that the cubic/tetragonal phase is thermally stable in this temperature range.
Extreme Scaled Gate Dielectrics By Using ALD HfO2/SrTiO3 Composite Structures
Authors: Pierreux Dieter , Machkaoutsan Vladimir , Tois Eva , Swerts Johan , Schram Tom , Adelmann Christoph , Van Elshocht S. , Popovici Mihaela I. , Conard Thierry , Tseng Joshua , Ragnarsson Lars-Aåke , Maes Jan W.
Published: September 2009

A sub 1-nm equivalent oxide thickness (EOT) gate stack with conduction band edge effective work function is demonstrated with an ALD deposited HfO2/SrTiO3 based composite material. An EOT reduction of 0.2 nm as compared to the HfO2 reference is obtained after applying a high thermal budget in a gate first transistor flow. A comparison with ALD HfO2/La2O3 and HfO2/MgO composite stacks is made. Results suggest that the EOT reduction and threshold voltage shift (Vt) are determined by the Sr, La or Mg diffusion inside the dielectric stack and into the interface oxide after a thermal treatment. The onset of this diffusion is temperature dependent and differs from stack to stack.
Copper Oxide ALD from a Cu(I) -Diketonate: Detailed Growth Studies on SiO2 and TaN
Authors: Waechtler Thomas , Roth Nina , Mothes Robert , Schulze Steffen , Schulz Stefan E. , Gessner Thomas , Lang Heinrich , Hietschold Michael
Published: September 2009

The atomic layer deposition (ALD) of copper oxide films from [(nBu3P)2Cu(acac)] and wet oxygen on SiO2 and TaN has been studied in detail by spectroscopic ellipsometry and atomic force microscopy. The results suggest island growth on SiO2, along with a strong variation of the optical properties of the films in the early stages of the growth and signs of quantum confinement, typical for nanocrystals. In addition, differences both in growth behavior and film properties appear on dry and wet thermal SiO2. Electron diffraction together with transmission electron microscopy shows that nanocrystalline Cu2O with crystallites < 5 nm is formed, while upon prolonged electron irradiation the films decompose and metallic copper crystallites of ~ 10 nm precipitate. On TaN, the films grow in a linear, layer-by-layer manner, reproducing the initial substrate roughness. Saturated growth obtained at 120{degree sign}C on TaN as well as dry and wet SiO2 indicates well-established ALD growth regimes.
Liquid Injection Atomic Layer Deposition of Metallic Ru Thin Films from Ru(tmhd)3 and of High-k TiO2 Thin Films from Ti(O-i-Pr)2(tmhd)2
Authors: Kim Seong Keun , Hoffmann-Eifert Susanne , Waser Rainer
Published: September 2009

Unique features of liquid delivery atomic layer deposition (LIALD) are considered in this paper in comparison to standard bubbler-type thermal ALD processes. The first part deals with the LIALD growth of metallic Ru thin films using tris(2,2,6,6-tetra-methyl-3,heptanedionato)ruthenium(III) dissolved in ethylcyclo hexane (ECH) and oxygen as metal and oxidation sources. We will show that LIALD is effective in reducing the contents of the corresponding oxides in the noble metal films. The second case deals with LIALD of TiO2 thin films with a smooth morphology from Ti(O-i-Pr)2(thd)2 dissolved in ECH as a Ti source and H2O as an oxidant. The self-saturation growth behavior of the TiO2 films was confirmed up to 390 oC. The differences in the surface roughness of the nanocrystalline LIALD TiO2 thin films obtained from Ti(O-i-Pr)2(thd)2 compared to nanocrystalline ALD TiO2 thin films from Ti(O-i-Pr)4 are discussed with respect to the differences in the nucleation behavior.
Plasma-Enhanced Atomic Layer Deposition of Ta(C)N Thin Films for Copper Diffusion Barrier
Authors: Kim Kwang-Ho , Jeong Seong-Jun , Yoon Jaesik , Kim Young-Moon , Kwon Se-hun
Published: September 2009

Ta(C)N thin films were deposited by plama-enhanced atomic layer deposition using an alternate supply of tertiary amyl imido-tris(dimethylamido) tantalum [TAIMATA] and hydrogen plasma at 230°. Hydrogen plasma acted as an effective reducing agent for TAIMATA. The film thickness/cycle was saturated at 0.132nm/cycle, when the source pulse time exceeds 5 sec. The resistivity of Ta(C)N films was 1000 μΩ-cm, which is higher value as the application of Cu diffusion barrier material. However, the resistivity of TaN films improved with the increase of hydrogen plasma time because of the decrease of Ta3N5 (>106 μΩ-cm) phase formed by insufficient active hydrogen radical to reduce alkyl groups in TAIMATA, the formation of Ta-C (30 μΩ-cm) phase, and the increase of crystallinity of cubic-TaN. By applying higher plasma power, the lattice mismatch between Ta(C)N and CVD-Cu can be minimized. As a result, Ta(C)N films showed an improved adhesion to CVD-Cu.
Metal Alloy Catalysts with Pt Surface Coating by Atomic Layer Deposition for Intermediate Temperature Ceramic Fuel Cells
Authors: Shim Joon Hyung , Jiang Xirong , Bent Stacey F. , Prinz Fritz B.
Published: September 2009

We have tested atomic layer deposition (ALD) of platinum layers onto various sputtered porous metals including silver, palladium, ruthenium and gold as catalysts of ceramic fuel cells expecting good surface alloying. We investigated thermal and chemical stability against oxidation using x-ray photoelectron spectroscopy (XPS). Fuel cell tests were conducted using the metal-ALD Pt cathodes with 200μm-thick 8% yttria stabilized zirconia electrolytes and sputtered platinum anodes. Performance of the fuel cells was measured by comparing the current-voltage curves and maximum power densities with varying temperature.
Interface Analysis of Transparent Analog Capacitor Using ITO Electrodes and ALD High-k Dielectrics
Authors: Won Seok-Jun , Huh Myung Soo , Park Sanghyun , Suh Sung-In , Choi Yu-Jin , Heo Jaeyeong , Hwang Cheol Seong , Kim Hyeong Joon
Published: September 2009

For the first time, we report transparent analog capacitors using ITO electrodes and HfO2 (and/or Al2O3) high-k dielectrics. The use of ITO bottom and top electrodes did not cause the electrical degradation to the capacitor compared to TiN and Pt electrodes. In the viewpoint of analog capacitors, capacitors using ITO electrodes show a few different characteristics. The right-side inclination of a C-V curve in ITO electrodes suggests that there is a thicker depletion layer at the top interface. This is probably due to the high resistivity of the Sn-rich top ITO initial layer on the dielectric film. Before and after subsequent thermal annealing, while the C-V curve of ITO/Al2O3/ITO is hardly changed, that of ITO/HfO2(or HAH)/ITO is greatly changed. Our results demonstrate that this comes not from the crystallinity change of ITO and/or HfO2 but from the composition change (ex. Hf diffusion and oxygen deficiency) at the interface.
Atomic Layer Deposition of Materials for Phase-Change Memories
Authors: Leskelä Markku , Pore Viljami , Hatanpää Timo , Heikkilä Mikko , Ritala Mikko , Schrott Alejandro , Raoux Simone , Rossnagel Stephen
Published: September 2009

Germanium antimony telluride (GST) materials and precursors for gas-phase thin film deposition are briefly reviewed. In the experimental part we show that alkylsilyls of tellurium can be used as tellurium precursors in plasma-free atomic layer deposition (ALD). Compounds with a general formula (R3Si)2Te react with various metal halides producing metal telluride thin films. Sb2Te3, GeTe and GST films can be deposited by ALD at temperatures below 100 {degree sign}C using (Et3Si)2Te, SbCl3 and GeCl2•C4H8O2 as precursors. All three precursors exhibit a typical saturative ALD growth behaviour in binary telluride processes. When processing ternary materials some non-ideal behaviour exist but by adjusting the exposure times and ratio of the binary cycles Ge-Te and Sb-Te, the GST composition could be controlled. The ternary films are amorphous as-deposited and crystallize at 130 {degree sign}C in the cubic structure, and at around 250-300 {degree sign}C the stable hexagonal phase is formed. Phase change behavior of the ALD GST films was studied using a static laser tester and found to be similar to sputter deposited films.
Status of National Project for SOFC Development in Japan
Authors: Hosoi Kei , Nakabaru Mitsugu
Published: September 2009

The basic research and development for SOFC technology began in 1989, and included two phases prior to 2001. In Phase 3, from 2001 to 2004, we carried out the development of thermal self-supporting modules, which resulted in high performance, cost effective and reliable modules. To prepare for the demonstration for introduction, NEDO carried out system technology development for 10kW to 200kW classes of SOFCs from 2004 to 2007. Furthermore, elemental technology development for future generation SOFCs was done from 2005 to 2007. In 2007 NEDO started demonstrative research on SOFC, to identify issues for future technological development. Our novel project from 2008 to 2012 has just been commenced for the improvement of durability and the advancement of practical applications. This paper summarizes status of national project for SOFC Development in Japan.
Development of kW Class SOFC Stack and System for Solid Oxide Fuel Cell Operating at Intermediate Temperature
Authors: Yoo Young-Sung , Lee Taehee , Choi Jin Hyeok
Published: September 2009

A 1 kW-class SOFC stack using metallic interconnects such as ferritic stainless steel and anode-supported single cells of 10 x 10cm 2 with thin electrolyte layer(<25μ) of YSZ was fabricated for application to Residential Power Generation(RPG). I-V and AC impedance characteristics of single cells were evaluated at intermediate temperature(650~750°). Maximum power density of the 10x10cm2 cells was about 0.32 W/2 at 750° and 0.2 W/2 at 650°. A 1kW-class SOFC stack composed of 48 cells (10x102) was successfully manufactured and a SOFC system with BOPs for combined heat and power was integrated to operate and evaluated for long-term. The system designed for RPG using natural gas as fuel can concurrently produce electricity and hot water from recuperating the stack exhaust heat. The system showed maximum DC output of 1.6kWe at 720°. Detailed status and experimental results of the 1kW-class SOFC system are discussed in this paper.
200 W Module Design using Micro Tubular SOFCs
Authors: Funahashi Yoshihiro , Suzuki Toshio , Fujishiro Yoshinobu , Shimamori Toru , Awano Masanobu
Published: September 2009

Solid oxide fuel cells (SOFCs) have several problems regarding to rapid heat cycle. In order to solve these problems, we utilized micro tubular SOFCs and developed a micro tubular SOFC bundle with the performance over 3 Wcm-3. In this study, we focused on the establishment of fabrication technique of 15 cm3 stack-bundle and assembling technique of a few-hundred-W class module. The micro tubular cells in the stack-bundle were connected by using a conducting paste in series and parallel. The stack-bundle has current terminals on the top and bottom of the stack-bundle, which allows easy assembling of a module (consisting of eight stack-modules, a pair of current collectors and a pair of fuel manifolds) only by fastening several bolts. The power of this module was designed to generate 200 W from the output power of single micro tubular SOFCs.
Development of the Gas Channel Integrated SOFC Cell and Stack at NGK Insulators, Ltd.
Authors: Ryu Takashi , Takase Naoya , Matsuda Kazuyuki , Kuno Toshiaki , Ichigi Takenori
Published: September 2009

The design of the gas channel integrated cell was reconsidered to reduce the cell thickness without increasing the cell resistance. The cell resistance was decreased by the reduction of the current collection distance. Furthermore, the changing of the current collection window position also decreased the cell resistance. The new design cell showed the same power density as the former design cell, indicating that the thickness of the cell was successfully reduced without any decrease of the cell power output. The power output of the new design cell was 1.6 times larger than that of the planar cell with the same cell size. The large power output per cell was a great advantage of the GCI cell.
Generating Electricity at 60% Electrical Efficiency from 1 - 2 kWe SOFC Products
Authors: Payne Richard , Love Jonathan , Kah Michael
Published: September 2009

Ceramic Fuel Cells Limited (CFCL) has developed Gennex and BlueGen products that are highly efficient SOFC products for the micro-CHP and electrical generator markets operating on natural gas and producing electricity to the grid at 1 - 2 kWe. An electrical efficiency (LHV) of 60% is being achieved by the system for net AC electricity exported to the grid. An additional 25% of power is available as heat. This paper describes how this electrical efficiency is achieved in CFCL's product.
Field Testing of SOFC at CMR Prototech
Authors: Warnhus Ivar , Vik Arild
Published: September 2009

Prototech AS has recently performed field tested of a 3 kW SOFC system. BKK-pilot is a 3 kW CHP system operating on natural gas. To this day, it has been operated for approximately 1800 hours. The test show steady and degradation free operations, where all changes in the performance could be explained by variation in temperature or in variations in the fuel quality.
A Combined System of an SOFC and PEFCs
Authors: Yakabe Hisataka , Yoshida Hideki , Amaha Shinji
Published: September 2009

An idea for a combined system of an SOFC and PEFCs is proposed. Large scale SOFCs are thermally self-sustainable and excess heat is available for the other use. The excess heat is used for a production of hydrogen. Several variations of the hydrogen production systems are proposed. The combination of the SOFC system with recycling the off-fuel and the hydrogen production system by purifying the off-fuel use effectively the excess heat and can produce much hydrogen. The generated hydrogen can be used as a fuel for PEFCs. PEFCs can be operated directly with the produced hydrogen and the present combined system improves the overall electrical conversion efficiency compared with the standalone PEFC or SOFC systems. For the SOFC and PEFCs combined system, the overall conversion efficiency is higher by around 10% than that of the standalone SOFC system.
In-Situ Investigation of SOFC Patterned Electrodes using Ambient-Pressure X-ray Photoelectron Spectroscopy
Authors: McDaniel Anthony , El Gabaly Farid , Akhadov E. , Farrow Roger L. , McCarty Kevin F. , Linne Mark A. , Decaluwe Steven C. , Zhang Chunjuan , Eichhorn B. , Jackson Gregory S. , Liu Zhi , Grass Michael , Hussain Zahid , Bluhm Hendrik
Published: September 2009

Single chamber electrochemical cells were fabricated by patterning working and counter electrodes of Ni and Pt on single-crystal Y2O3-stabilized ZrO2. Cells were characterized in mixed atmospheres of H2 and H2O at ratios of 1:1 and 1:20 at nominally 923 K and 67 Pa total pressure. Potential sweep and impedance measurements were conducted simultaneously with ambient-pressure x-ray photoelectron spectroscopy (APXPS), which is a unique synchrotron-based probe designed for in-situ chemical characterization of surfaces using photoemission at gas pressures large enough to achieve realistic densities of faradic current. Electrochemically induced oxidation of Ni was observed under anodic polarization and could be reversed by applying a cathodic bias. The thin-film microstructure could also be manipulated electrochemically in that pores exposing underlying electrolyte would open through the Ni film after polarization. Application of APXPS to resolve fundamental details of high-temperature electrochemical process in-situ is discussed.
Investigation on Oxygen Potential Distribution in a ZrO2-Based Solid Electrolyte by Using In-Situ Micro XAS Technique
Authors: Amezawa Koji , Ina Toshiaki , Orikasa Yuki , Unemoto Atsushi , Watanabe Hidetaka , Iguchi Fumitada , Terada Yasuko , Fukutsuka Tomokazu , Kawada Tatsuya , Yugami Hiroo , Uchimoto Yoshiharu
Published: September 2009

Oxygen potential distribution in a ZrO2-based solid electrolyte in the vicinity of a dense film platinum electrode under a current flow was investigated by using in-situ micro x-ray absorption spectroscopy. The oxide ion conductor (Y2O3)0.08(ZrO2)0.92 doped with 2.5 mol% of Mn2O3, in which the valence state of manganese ions could be used as an indicator for evaluating the oxygen potential, was chosen as a model electrolyte. As results, a drastic drop of oxygen potential was apparently observed near the triple phase boundary. The proposed method was found to be principally applicable for the direct observation of the oxygen potential distribution in an oxide ion conductor under a current flow.
Performance Analysis of Single Step Co-fired Solid Oxide Fuel Cells (SOFCs)
Authors: Yoon Kyung Joong , Gopalan Srikanth , Pal Uday B.
Published: September 2009

Anode-supported planar solid oxide fuel cell (SOFC) was fabricated by a single step co-firing process, and tested between 700~800oC with humidified hydrogen (97% H2+3% H2O) as fuel and air as oxidant. The measured maximum power densities were 1.42W/cm2 at 800oC, 1.20W/cm2 at 750oC, and 0.87W/cm2 at 700oC. The cell was also tested at 800oC with various compositions of oxidant, and the cell parameters, which included the area specific ohmic resistance, exchange current densities, and anodic and cathodic limiting current densities, were obtained through polarization modeling. The polarization resistances of the cell were calculated using the cell parameters obtained from modeling, and compared with the corresponding values measured using impedance spectroscopy. The effect of cell operating conditions on various polarization losses and performance was analyzed in detail using the polarization modeling results.
Effect of Pre-sintering Treatment of Anode Substrate on the Densification and Flatness of YSZ Electrolyte by Suspension Spray
Authors: Zhang Lei , Zhang Shangquan , Bi Lei , Xie Bin , Liu Wei , Wang Haiqian
Published: September 2009

A suspension spray technique was developed to fabricate dense YSZ electrolyte films on pre-sintered NiO/YSZ anode substrates. The substrates were prepared by tape casting and then pre-sintered at different temperatures. The results indicate that the shrinkage of anode substrates during the pre-sintering treatment and the co-sintering process plays a very important role in electrolyte densification and cell distortion. Flat and camber-free YSZ-NiO/YSZ bi-layers were obtained when the pre-sintering temperature was higher than 1200{degree sign}C; while the electrolyte films were dense when the pre-sintering temperature was lower than 1225{degree sign}C. The single cell based on the anode pre-sintered at 1200{degree sign}C outputted a maximum power density of 0.747 W/cm-2 and OCV of 1.00V at 800{degree sign}C with humidified hydrogen as fuel and ambient air as oxidant.
Suspension Plasma Spraying to Manufacture Electrodes for Solid Oxide Fuel Cell (SOFC) and Solid Oxide Electrolysis Cell (SOEC)
Authors: Marchand Olivier , Saoutieff Elise , Bertrand Pierre , Planche Marie-Pierre , Tingaud Olivier , Bertrand Ghislaine
Published: September 2009

SOFC technology is assumed to have significant potential in energy conversion although many obstacles still prevent its widespread use. Among these, the cost of scaling up existing manufacturing processes for mass production is of major concern. With thermal spray technology, SOFCs can be produced without implementing time consuming sintering steps required in wet ceramic processing. Suspensions Plasma Spraying is one of the promising solutions because it produces thin layer with finer and more adapted microstructures. In the present work, water or alcoholic suspensions of sub-micronic, YSZ/NiO for hydrogen electrode and La2NiO4 for oxygen electrode have been studied to achieve a good dispersion and stability. These optimised suspensions have been injected into the plasma spray system to produce porous coatings of 40 µm thick onto ferritic porous substrates. The evolution of the morphology and crystalline structure of the electrodes have been investigated by SEM/EDS and XRD with the operating parameters.
Manufacturing Ceramic Tapes and Thick Film Pastes for SOFCs in an ISO 9001 Environment
Authors: Feingold Alvin , Topka Zack , Twiname Eric , Palanisamy P. , Webb Richard
Published: September 2009

Cell and stack developers need to obtain volume quantities of materials consistently and economically. Two viable technologies are cast ceramic tapes and thick-film pastes. Engineering, scale-up, and manufacture provide unique challenges. Materials engineered for manufacturability require control from raw material identification to finished product including source qualification, specification development, paste and tape formulation, in-process control, and documentation. Tapes are manufactured in laboratory and prototype volumes. Thin electrolyte tapes present a manufacturing challenge. Data on tapes that fire to full density at thicknesses <12.5µm are shown. Pastes are used for electrolytes, cathodes, anodes, current collectors, and interconnects. Electrolytes must be gas tight. Vehicles required to disperse high surface area powders must burn out to leave dense, uniform films. Cathode and anode pastes require vehicles designed for large area prints. Reproducing pastes despite powder variation is another challenge. Paste properties for multiple manufacturing lots are presented.
Metal-Supported SOFC Development at JPOWER
Authors: Sakuno Shinichi , Takahashi Shuuichi , Sasatsu Hiroshi
Published: September 2009

JPOWER has been developing the low-cost and high-reliability tubular type metal-supported SOFC in collaboration with LBNL (Lawrence Berkeley National Laboratory, USA). In our collaboration, JPOWER is mainly focusing on stacking the metal-supported thin-film YSZ SOFC cells developed by LBNL, while LBNL is focusing on developing the cells. The cells are composed of 5-layer in which the cell elements (Anode/Electrolyte/Cathode) are sandwiched between porous stainless steel current collectors, so it is easy to stack and/or bundle the cells by the existing technology of metal joining. JPOWER designed the segment-in-series type simplified cell stacking structure and verified the proof-of-concept by testing a single cell and 2-cells stacking structure. In this paper, JPOWER's activities for metal-supported SOFC development are discussed.
IDEAL-Cell, Innovative Dual mEmbrAne fueL-Cell: Fabrication and Electrochemical Testing of First Prototypes
Authors: Presto Sabrina , Barbucci Antonio , Viviani Massimo , Ilhan Zeynep , Ansar Asif , Soysal Dennis , Thorel Alain S. , Abreu Joao , Chesnaud Anthony , Politova Tatiana , Przybylski Kazimierz , Prazuch Janusz , Brylewski Tomasz , Zhao Zhe , Vladikova Daria E. , Stoynov Zdravko
Published: September 2009

The IDEAL-Cell concept is based on the junction between a PCFC anode/electrolyte section and a SOFC cathode/electrolyte section, through a mixed proton and oxide ion conducting porous ceramic membrane, operating in the temperature range 600-700{degree sign}C. Recombination of ions takes place within the junction, or central membrane (CM), and water vapor is evacuated through open porosity. The first results on the fabrication of multilayered samples reproducing the IDEAL-Cell structure are reported here, together with electrochemical tests carried out on selected samples in order to evaluate the performances of the chosen materials and to demonstrate the feasibility of this innovative concept of fuel cell. Stable OCV and power generation were obtained in the multilayered structures. Anomalies on the I/V curves and impedance measurements under large perturbation could be considered as proofs of water formation inside the central membrane.
Semi-Empirical Equations to Estimate SOFC Lifetime
Authors: DiGiuseppe Gianfranco , Sun Li
Published: September 2009

This paper explores the possibility to estimate the SOFC lifetime using different semi-empirical equations. Several possibilities are discussed, including the advantages and disadvantages of each approach. Empirical equations are equations that fit the observed data and are not necessarily derived from first principles. Empirical equations are best suited if the SOFC has only one degradation mechanism. For instance, if the voltage-time data exhibits multiple slopes and the voltage degrades at different rates, it is very likely that multiples modes of degradation are present.
Impact of Flowfield Design on Solid Oxide Fuel Cell Performance
Authors: Kornely Michael , Leonide André , Weber André , Ivers-Tiffée Ellen
Published: September 2009

In the present work a finite element method (FEM) model was developed to investigate the impact of the flowfield design on the performance of a planar SOFC repeat unit. The 2-D FEM model, which considers the performance data of an ideal contacted cell, the electrical conductivities of the electrode materials and the contact resistance between the electrodes and the metallic interconnectors, provides the electrical potential and current density distribution in the repeat unit. Simulations and experimental studies for different flowfield geometries were performed to evaluate the cell performance decrease due to the in plane ohmic losses in the electrode and the contact resistance. Experimental and modeling data are in good agreement. With respect to anode supported cells, the flowfield design on the cathode side has a significant impact (~ 48 % power loss) on the cell performance, whereas the flowfield design in the anode is of minor importance (< 1% power loss).
Cycling Studies of Microtubular SOFCs
Authors: Kendall Kevin , Dikwal Chinnan
Published: September 2009

A major problem of solid oxide fuel cells (SOFCs) is their long term durability under cyclic operation, for example during start-up and shutdown, where cracking can occur. The objective of this project was to understand these mechanisms of cyclic degradation for microtubular SOFCs, then to set up experiments to measure the degradation in terms of the drop in electrochemical performance, subsequently confirming the theories by dilatometry and scanning electron microscopy (SEM). First, a theory of degradation based on micro-crack propagation due to expansion/contraction of the Ni cermet anode was propounded. Several experiments were then designed to illustrate the degradation phenomena including temperature and redox cycling.
Comparison of Mechanical Testing Methods for Micro-tubular Solid Oxide Fuel Cells
Authors: Roy Brycen R. , Sammes Nigel M.
Published: September 2009

A fundamental issue with micro-tubular solid oxide fuel cells (SOFCs) is improvement in the mechanical strength of the cell. Fabricated using extrusion techniques, the approximately 1.7 mm diameter anode support-tubes tested in this study are composed of a 50:50 NiO and Gd2O3-doped ceria cermet. The mechanical properties of the tubes are analyzed through internal burst testing and monotonic compressive loading on a c-ring test specimen. The burst test is an important parameter because of improved power efficiency at increased fuel pressures, and c-ring testing is critical to determine ultimate strengths because of external stresses incurred in a fuel cell stack. In order to develop a trend for the mechanical behavior of micro-tubes in relation to variations in fabrication techniques, several parameters are varied. The two testing techniques are compared and related, and maximum hoop stress values are reported for each of the fabrication parameters.
YSZ Free-standing Membranes for Silicon-based Micro SOFCs
Authors: Tarancon Albert , Garbayo Iñigo , Santiso Jose , Cavallaro Andrea , Roqueta J. , Garcia Gemma , Gràcia Isabel , Cané Carles , Sabaté Neus
Published: September 2009

The present study is devoted to analyze the compatibility of yttria-stabilized zirconia thin films prepared by pulsed laser deposition technique for developing new silicon-based micro devices for micro solid oxide fuel cells applications. Yttria-stabilized zirconia free-standing membranes with thicknesses from 60 to 240 nm and surface areas between 50x50 µm2 and 820x820 µm2 were fabricated on micromachined Si/SiO2/Si3N4 substrates. Deposition process was optimized for deposition temperatures from 200ºC to 800ºC. A mechanical study comprising thermomechanical stability, residual stress of the membranes and annealing treatment as well as a preliminary electrical characterization of ionic conductivity was performed in order to evaluate the best processing parameters for the yttria-stabilized zirconia membranes.