bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photodefinable Metal Oxide Dielectrics II: Direct Fabrication of Patterned High-k Dielectrics for Low Cost RF Capacitive MEMS Switches
Authors: Romeo Michael , Finger Isaac , Jeyakumar Augustin , Wang Guoan , Papapolymerou John , Henderson Clifford L. 
Published: April 2011

ABSTRACTIn this paper, recent advancements related to a novel approach for fabricating low cost capacitive radio frequency microelectromechanical (RF MEMS) switches using directly photodefinable high dielectric constant metal oxides are discussed. In this approach, a radiation sensitive metal-organic precursor is deposited via spin coating and converted patternwise to a metal oxide using exposure to ultraviolet light. The feasibility of this approach has previously been demonstrated by fabricating bridge-type and cantilever-type RF MEMS switches. These early experiments showed that the photopatterned oxides displayed dielectric breakdown strengths that were insufficient for reliable operation of MEMS switches which required actuation voltages on the order of 20 V to 30 V. Recent work has focused on developing advanced processes based on the photodefinable metal-organic approach that can produce oxides with higher dielectric breakdown strengths and higher dielectric constants. A variety of post-patterning processes, including thermal baking and oxygen plasma annealing, were investigated and the impact of such processing on the resulting dielectric properties are discussed in this paper. It is shown that a combination of thermal annealing and oxygen plasma treatment can substantially improve the dielectric breakdown strength of the metal oxides produced using the photosensitive metal-organic process.
Novel High-Q Suspended Inductors on Alumina Ceramic Substrates
Authors: Woodward Lisa , Woo Paul , Capanu Mircea , Koutsaroff Ivo , Selvakumar C. R. , Cervin-Lawry Andrew 
Published: April 2011

ABSTRACTThe growth of the wireless industry over the past ten years has created a need for good quality passive components, and in particular high Q factor inductors. There has been a large amount of work aimed at improving the quality factors of inductors on both silicon and ceramic/insulating substrates. KAIST and other research groups have explored a MEMS technique, releasing the inductor coil to create an air gap between the coil and underpass, on silicon [1]. Typically the inductor coil has been separated by a 50 to 100μm air gap and has required special processing such as a dual exposure photoresist mold [1]. In the present work, suspended inductor coils have been fabricated and characterized on an alumina ceramic substrate [2]. The gap used was only 1μm and this was enough to increase the self-resonance frequency by up to 4GHz after release. The inductor coils were created in 6–10μm thick electroplated gold and the underpass in an aluminum layer. A sacrificial LPCVD oxide layer was used as the released dielectric. In the present study a range of inductance from 1 to 30nH was explored before and after release. The Q factors achieved in this work range from 40 to 70 in the 2 to 10 GHz range, which are some of the best Q factors reported for planar inductors (see Table I). In addition, since the architecture allowed the use of three metal layers, released transformers were also fabricated. They showed promising high frequency performance, which also will be presented. Minimum insertion loss better then –2dB was achieved between 10–12 GHz. The above described process is simple, precise, and manufacturable with the ability to extend the useful range of inductors to higher frequencies (1–10 GHz).
A Silicon Nitride Based Shallow Trench Isolation with Side-Gate for CMOS Integration with MEMS Components for System-On-Chip Applications
Authors: Gokirmak Ali , Tiwari Sandip 
Published: April 2011

ABSTRACTWe have developed a hydrofluoric acid (HF) resistant, composite shallow trench isolation (STI) process for MOSFETs utilizing silicon nitride as isolation material for on-chip integration of micro-electro-mechanical (MEMS) resonators and CMOS devices. Peripheral leakage currents in silicon nitride isolated MOSFETs are suppressed by employing an independently controlled polysilicon side-gate, surrounding the active area of the devices. Electrostatic control of the threshold voltage at the device periphery alleviates the need for edge implants, resulting in increased thermal budget. Compatibility with HF release processes and high temperature anneal cycles allows integration of MEMS components in close proximity to CMOS devices for system-on-chip applications. nMOSFET devices fabricated using this composite STI process show excellent device characteristics.
Three-dimensional magnetophotonic crystals based on artificial opals: fabrication and properties
Authors: Baryshev A. V. , Kodama T. , Nishimura K. , Uchida H. , Inoue M. 
Published: April 2011

ABSTRACTWe have fabricated three-dimensional magnetophotonic (3D MPCs) crystals based on artificial opals. Structural and magnetic properties of 3D MPCs were studied by field emission scanning electron microscopy, x-ray diffraction analysis, and vibrating sample magnetometer. It was shown that increase of volume fraction of magnetite in the opal lattice leads to a dramatic decrease of transmitted light intensity in the visible region. We also found considerable changes in the Faraday rotation inside the (111) photonic bandgap of an opal—magnetite magnetophotonic crystal.
Fabrication of Integrated Magneto-Optic Isolator
Authors: Sung Sang-Yeob , Qi Xiaoyuan , Reinke John , Mondal Samir K. , Lee Sun Sook , Stadler Bethanie J. H 
Published: April 2011

ABSTRACTIn optical applications, especially in optical communications, protecting light sources from harmful reflected energy is very important. With magneto-optic isolators, these light sources can be protected to extend their lifetimes and performance by blocking back-reflected light. The active element in these optical isolators is a magneto-optical garnet. However, garnet is difficult to integrate with semiconductors due to the high thermal budget usually required to obtain the garnet crystal structure. For example, current isolator garnets cannot be integrated monolithically into a photonic integrated circuit due to the growth process, liquid phase epitaxy, which requires growth temperatures of >900 °C and also garnet substrates. In this work, magneto-optical garnets were grown monolithically by low-temperature reactive RF sputtering, followed by an ultra-short (<15 sec) anneal. The refractive indices of the resulting garnets were measured using Fourier transform infrared (FTIR) spectroscopy. Various rib waveguides were fabricated by both wet etching and reactive ion etching (RIE). The width of the waveguides varied from 2 to 12 μm and the heights were varied from 0.5 to 1.0 μm. Sm-Co thin films were used for integrated biasing magnets. They were deposited on top of claddings of both magnesium oxide and yttrium oxide, all using the same sputtering system that was used to deposit the garnet films. These magnetic films had high enough remanent fields to saturate the garnet waveguides, and they had coercivities of 700 Oe. The Faraday rotations and waveguide losses of the subsequent isolators were measured to be 10 degrees and 0.1 dB/μm at 632 nm, respectively. Although this prototype is promising, optimization of the device designs is ongoing. In summary, this work succeeded in providing the first comprehensive report on etching YIG by RIE, in developing all of the steps required for integrating isolators on non-garnet substrates, and in proving the feasibility of these isolators.
Waveguide Optical Isolators Fabricated by Wafer Bonding
Authors: Mizumoto Tetsuya , Yokoi Hideki 
Published: April 2011

ABSTRACTWafer bonding of a magnetooptic garnet crystal to III-V compound semiconductor and LiNbO3 is discussed for the application to waveguide optical isolators. Two types of waveguide isolators, an interferometric isolator and a semileaky isolator, are discussed. The interferometric isolator uses nonreciprocal phase shift and is composed of the GaInAsP guiding layer. The isolator has the advantage of integratability with optical active devices. The semileaky isolator composed of a magnetooptic garnet guiding and LiNbO3 upper cladding layer has the advantages of large fabrication tolerance and wide operating wavelength range. The performance of isolators is also demonstrated.
Magneto-Optical Properties of Multilayered FePt for High Density Recording
Authors: Ryu Hojun , Suh Dongwoo , Park Yongwoo , Kim Eunkyung , Yoo Yonggoo , Jung Woosug , Paek Mun Cheol 
Published: April 2011

ABSTRACTThe Si3N4/FePt/Si3N4/Al/Si structures have been fabricated. 57 nm silicon nitride films have been used as dielectric layer for heat dissipation and 500 nm Al film used for reflection layer. The Kerr rotation angle was changed with the FePt layer thickness. At the 65 % Pt composition in 10 nm FePt layer, the maximum Kerr rotation angle was 0.82°. As increase with FePt thickness the Kerr angle is slightly decreased. The change of Kerr rotation angle and the thermal behavior of multilayered structure according to FePt thickness variation were also calculated by computer simulation.
Magnetorefractive effect in magnetophotonic crystals
Authors: Erokhin Sergey G. , Boriskina Yulia V. , Granovsky Alexander B. , Vinogradov Alexey P. , Zhao X.S. , Inoue Mitsuteru 
Published: April 2011

ABSTRACTThe magnetorefractive effect in one-dimensional magnetophotonic crystals was investigated at a wavelength of about 3 μm. It is shown that the magnitude of magnetorefractive effect can be increased to 10–15 times in comparison with one magnetic layer of the same thickness positioned on a metallic mirror.
The Effect of Mn Concentration on Curie Temperature and Magnetic Behavior of MOCVD Grown GaMnN Films
Authors: Berkman Erkan Acar , Reed Mason J. , Erdem Arkun F. , El-Masry Nadia A. , Zavada John M. , Oliver Luen M. , Reed Meredith L. , Bedair Salah M. 
Published: April 2011

ABSTRACTWe report on the growth and characterization of dilute magnetic semiconductor GaMnN showing ferromagnetism behavior above room temperature. GaMnN films were grown by MOCVD using (EtCp2)Mn as the precursor for in-situ Mn doping. Structural characterization of the GaMnN films was achieved by XRD, SIMS and TEM measurements. XRD and TEM confirmed that the films were single crystal solid solutions without the presence of secondary phases. SIMS analysis verified that Mn was incorporated homogeneously throughout the GaMnN layer which was ∼0.7μm thick. Ferromagnetic behavior for these films was observed along the c-direction (out of plane orientation) in a Mn concentration range of 0.025–2%. The saturation magnetization ranged from 0.18–1.05 emu/cc for different growth conditions. Curie temperatures of the GaMnN films were determined to be from 270 to above 400K depending on the Mn concentration. This dependence of Curie temperature on concentration of Mn in GaMnN indicates that the grown films are random solid solutions. SQUID measurements ruled out the possibility of spin-glass and superparamagnetism in these MOCVD grown GaMnN films. The grown films were electrically semi-insulating; however PL measurements showed that the films were still optically active after Mn doping. This study showed that the growth of III-Nitride films doped with Mn requires a small window of growth conditions that depend on growth temperature and (EtCp)2Mn flux to achieve ferromagnetism above room temperature, and the magnetic response of the film depends on the Fermi level position. We suggest that ferromagnetism occurs when the Fermi level lies within the Mn energy level which is 1.4 eV above the GaN valence band.
Recent Advances in Three Dimensional Thin Film Microbatteries
Authors: Nathan M. , Golodnitsky D. , Yufit V. , Strauss E. , Ripenbein T. , Shechtman I. , Menkin S. , Peled E. 
Published: April 2011

ABSTRACTAutonomous MEMS require similarly miniaturized power sources. We present the first three-dimensional (3D) working thin-film microbattery (MB) technology that is compatible with MEMS requirements. Our 3D MBs are formed in perforated substrates (silicon chip or glass microchannel plate), in which a sandwich-like thin-film battery structure is deposited conformally and sequentially on all available surfaces, using wet chemistry. The area of high aspect ratio holes in the substrate enhances the capacity and energy density per given substrate footprint by more than an order of magnitude. Full 3D cells were manufactured on both glass and silicon substrates. A 3D cell on a micro-channel plate substrate exhibited a capacity of ca. 2mAh/cm2, in good agreement with the ca. 23 times area gain provided vs an identical footprint 2D cell.
Structural and Electrochemical Properties of LiMn0.4Ni0.4Co0.2O2
Authors: Ma Miaomiao , Chernova Natasha A. , Zavalij Peter Y. , Stanley Whittingham M. 
Published: April 2011

ABSTRACTThe layered oxide LiMn0.4Ni0.4Co0.2O2 was synthesized by heating the mixed hydroxide precursor. This 442 composition was found to show high capacity. It has the optimum cobalt concentration to both substantially order the lattice, yet leave enough nickel on the lithium sites to minimize conversion to the 1T structure of CoO2 on deep charging. A combined x-ray and neutron diffraction study showed conclusively that only nickel, not manganese or cobalt is found on the lithium sites at room temperature. Magnetic measurements also confirmed the presence of nickel on the lithium sites, and showed the effectiveness of cobalt at minimizing nickel disorder. Heating above 800°C always leads to nickel disorder. The structural and thermal stability of reduced lithium content materials was studied; the structure remains rhombohedral except for x≤0.05, and cobalt substitution improves the thermal stability of the layered compound, but not the chemical stability.
Intermediate Temperature Electrochemical Ceramic Oxygen Generators
Authors: Sin Agusti , Aricò Antonino S. , Gullo Laura , Rosa Daniela La , Kopnin Evgeny , Dubitsky Yuri , Zaopo Antonio , Antonucci Vincenzo 
Published: April 2011

ABSTRACTIn the present work, an electrochemically driven ceramic oxygen generator (ECOG) device is investigated. The present device is based on an electrode supported architecture. Structural and electrochemical characterizations of the electrochemical cell have been carried out. The O2 production rate has been measured showing a performance four times higher than the generally accepted targets for practical applications. The high performance obtained with this device, indicates that there are good perspectives to decrease the O2 production costs significantly decreased as well as small and light weight devices for portable uses are envisaged.
Electrochemical behaviour of Co-doped LSGM perovskites prepared by sol-gel synthesis
Authors: Polini Riccardo , Falsetti Alessia , Traversa Enrico , Schäf Oliver , Knauth Philippe 
Published: April 2011

ABSTRACTLa0.8Sr0.2Ga0.8Mg0.2-xCoxO3-δ (LSGMC) powders containing different amounts of Co (x = 0.05 and 0.085) were prepared by a citrate sol-gel method. Crystalline powders were obtained by firing at 1000°C (10 h) and dense high-purity pellets were prepared by pressing (300 MPa) and sintering in air at 1475°C (5, 10 and 20 h). The sintered pellets of LSGMC were characterized by X-Ray Diffraction (XRD) Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The conductivity of sintered LSGMC pellets containing different amounts of Co ions in the B sites of the perovskite lattice was assessed by electrochemical impedance spectroscopy (EIS) in the 250–750 °C temperature range. Conductivity values and apparent activation energies were in good agreement with previously published data referring to materials with same composition, but prepared by solid-state reaction.
NMR and impedance study of H+-ion irradiated TlH2PO4
Authors: Kim Se Hun , Lee Kyu Won , Jang Jae Won , Lee Cheol Eui , Noh S. J. 
Published: April 2011

ABSTRACTThe H+-ion treatment effect on TlH2PO4, a KH2PO4 (KDP)-type ferroelectrics, was studied by nuclear magnetic resonance (NMR) and AC dielectric measurements. A sample of TlH2PO4 was irradiated by 1-MeV H+ ion beams to a dose of 1015 ions/cm2. The irradiation changed the hydrogen-bond geometry, presumably affecting the order-disorder proton dynamics. The deformation of the PO4 tetrahedra was identified by the isotropic chemical shift and the full width at half maximum (FWHM) of the high-resolution 31P NMR spectra. A prominent decrease in the dielectric constant was also observed after the irradiation. The macroscopic and microscopic changes due to the irradiation are discussed in the light of the proton dynamics.
Synthesis, Characterization and Thermal Stability of Highly Crystallized Titania Nanotubes
Authors: Poudel B. , Wang W. Z. , Dames C. , Huang J. Y. , Kunwar S. , Wang D. Z. , Banerjee D. , Chen G. , Ren Z. F. 
Published: April 2011

ABSTRACTGram quantities of titania (TiO2) nanotubes, with typical outside diameter about 9 nm, wall thickness about 2.5 nm, and length about 600 nm, were synthesized from anatase nano- and micro-powder using the hydrothermal method. The crystallization, structure, and phase stability of the nanotubes at high temperatures were systematically studied. A morphology change from nanotube to nanowire was observed at 650°C. The as-prepared nanotubes were usually contaminated with sodium impurities, other TiO2-derived phases and were poorly crystallized, but under optimized synthesis conditions the impurity phases was completely removed, resulting in highly crystallized pure nanotubes. The volume filling fraction of the autoclave as well as the concentration of the acid treatment were found to be particularly important for controlling the purity and crystallinity of the resulting nanotubes.
Dye Sensitized Solar Cells Using Nanostructured Thin Films of Titanium Dioxide
Authors: Gish Douglas A. , Kiema Gregory K. , Jensen Martin O. , Brett Michael J. 
Published: April 2011

ABSTRACTDye sensitized solar cells (DSSCs) were fabricated using porous thin films of TiO2. These films were deposited by electron beam evaporation and an advanced substrate motion technique called PhiSweep. PhiSweep, an extension of glancing angle deposition (GLAD), allows for greater control over the surface area of nanostructured thin films than is possible with traditional GLAD. The as-deposited films were amorphous, so the films were annealed to improve their crystal structure. The films were sensitized with a photoactive dye and implemented into a DSSC configuration as the electron collecting electrode. It was expected that the higher surface area of the films produced using the PhiSweep method would improve the cell performance compared with cells made using traditional GLAD films of TiO2. However, the performance of the cells prepared using PhiSweep films was likely hindered by higher internal resistance of the films compared to the films prepared by traditional GLAD. The highest photoelectric conversion efficiency of the dye sensitized solar cells produced using the PhiSweep method was 1.5%.
Bulk Heterojunction Photovoltaic Cells from Polymer Mixtures with Soluble Oxadiazole and Quinoline Polymers as Electron Acceptors
Authors: Economopoulos Solon , Chochos Christos L. , Govaris Giannis K. , Yiannoulis Panagiotis , Kallitsis Joannis K. , Gregoriou Vasilis G. 
Published: April 2011

ABSTRACTThe interplay between phase separation in polymer blends consisting of the electron donating poly(3-hexylthiophene-2, 5-diyl) (P3HT) or poly[2-methoxy-5-(2'-ethylhexyloxy)-, 4-phenylenevinylene] (MEH-PPV), with either polyquinoline or a fluorene-oxadiazole copolymer as the electron accepting polymers is presented herein. The bulk heterojunction photovoltaic performance has been examined for these blends along with a new copoly(aryl ether) containing substituted anthracene and fluorene segments coupled with aromatic 1, 3, 4-oxadiazole moieties. Photoluminescence quenching in the MEH-PPV blends as well as a 100-fold photocurrent enhancement of the bulk heterojunction device P3HT/SDPQ photovoltaic device were observed compared to the single layer P3HT device. Finally, the structure and morphology of these films was investigated using atomic force microscopy and scanning electron microscopy in an attempt to correlate the role of morphology to photovoltaic performance.
III-V Multi-Junction Materials and Solar Cells on Engineered SiGe/Si Substrates
Authors: Ringel Steven A. , Andre Carrie L. , Lueck Matthew , Isaacson David , Pitera Arthur J. , Fitzgerald Eugene A. , Wilt David M. 
Published: April 2011

ABSTRACTThe monolithic integration of high efficiency III-V compound solar cell materials and devices with lower-cost, robust and scaleable Si substrates has been a driving force in photovoltaics (PV) basic research for decades. Recent advances in controlling mismatch-induced defects that result from structural and chemical differences between III-V solar cell materials and Si using a combination of SiGe interlayers and monolayer-scale control of III-V/IV interfaces, have led to a series of fundamental advances at the material and device levels, which establish that the great potential of III-V/Si PV is within reach. These include demonstrations of GaAs epitaxial layers on Si that are anti-phase domain-free with verified dislocation densities at or below 1×106 cm−2 and negligible interface diffusion, minority carrier lifetimes for GaAs on Si in excess of 10 ns, single junction GaAs-based solar cells on Si with open circuit voltages (Voc) in excess of 980 mV, efficiencies beyond 18%, and area-independent PV characteristics up to at least 4 cm2. These advances are attributed in large part to the use of a novel “engineered Si substrate” based on compositionally-graded SiGe buffers such that a high-quality, low defect density, relaxed, “virtual” Ge substrate could be developed that can support lattice-matched III-V epitaxy and thus merge III-V technology based on the GaAs (or Ge) lattice constant with Si wafers. This paper focuses on recent results that extend this work to the first demonstration of high performance III-V dual junction solar cells on SiGe/Si. Open circuit voltages in excess of 2 V at one-sun have been obtained for the conventionally “lattice-matched” In0.49Ga0.51P/GaAs dual junction cells on inactive, engineered SiGe/Si; to our knowledge is the first demonstration of > 2V solar power generation on a Si wafer. Comparisons with identical cells on GaAs substrates reveal that the Voc on engineered Si retains more than 94% of its homoepitaxial value, and that at present both DJ/GaAs and DJ/SiGe/Si cells are similarly limited by current mismatch in these early cells, and not fundamental defect factors associated with the engineered Si substrates.
Preparation and characterization of monolithic HgCdTe/CdTe tandem cells
Authors: Wang S. L. , Drayton J. , Parikh V. , Vasko A. , Gupta A. , Compaan A. D. 
Published: April 2011

ABSTRACTA prototype monolithic HgCdTe/CdTe superstrate tandem cell has been fabricated by RF sputtering, comprising a CdTe/CdS top cell, a ZnTe:N/ZnO:Al interconnect junction and a HgCdTe/CdS bottom cell. The Hg1−xCdxTe film as the bottom absorption layer was deposited by RF sputtering with 70% or 85% Cd content in the Hg1−xCdxTe magnetron target. Hg1−xCdxTe films with band gap from 0.98 eV to 1.45 eV were obtained by controlling the deposition temperature. CdCl2 thermal treatments were used to improve the Hg1−xCdxTe film electrical properties. A nitrogen-doped ZnTe film combined with an aluminium (Al) doped ZnO film formed a good interconnect junction. Results of Voc = 0.99 V and Jsc = 2.1 mA/cm2 were obtained in the best such tandem cell at one sun (AM1.5).