bluuebunny/crossref_metadata_2025 huggingface dataset:
Tailoring Microdomain Orientation in Block Copolymer Thin Films for Lithographic Application
Authors: Yoshida Hiroshi , Kitano Hirofumi , Akasaka Satoshi , Inoue Tomohiro , Taknaka Mikihito , Hasegawa Hirokazu , Nagano Hideki
Published: April 2011

Block copolymer lithography is a promising method for fabricating periodical nano patterns less than 20nm by self-assembly and can be applicable for fabricating patterned magnetic media with recording density over 1Tbit/inch2. We found a simple technique to control the orientation of cylindrical microdomains in thin films. Only by mixing polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymers with the constituent homopolymer (PS or PMMA), we could align the cylindrical microdomains perpendicular to the film surface. The added homopolymer induces conformational entropic relaxation of the block chains in microdomain space and stabilizes perpendicular orientation of hexagonally packed cylindrical microdomains. Thus formed perpendicular cylinders can be readily aligned in a regular array with a grating substrate.
Measurement of Arrays of Dots Produced by Electron-beam Lithography
Authors: Hoyle Philip C. , Laidler Ian
Published: April 2011

Electron-beam mastering of templates for patterned media presents a challenge to the toolmaker to simultaneously meet throughput, resolution and placement requirements. Fundamental to tool development is the ability to measure the placement to true grid of shapes as small as 7 nm over the whole substrate. In this article we describe a technique, consisting of acquiring and analyzing scanning electron (SE) micrographs, for measuring the placement errors in lithography similar to that required for patterned media, albeit over a few square microns and without scale and orthogonality components. The method enabled the measurement of placement errors of dots in an array with accuracy down to about 2 nm. The technique was used to benchmark current X-Y tool performance and the smallest 3× standard deviation of placement error was found to be around 4.5 nm. A clearer understanding of the necessary tool improvements was obtained. The use of the technique as basis for measuring errors to true grid over the entire substrate is discussed.
Development of a Novel Metal Epitaxy Method towards Ni Based Electro-magnetic Hybrid Systems
Authors: Matsuda Akifumi , Kasahara Masayasu , Watanabe Takahiro , Hara Wakana , Otaka Sei , Koyama Kouji , Yoshimoto Mamoru
Published: April 2011

The epitaxial Ni (111) thin film on the oxide substrate could be obtained by a novel epitaxy method, employing pulsed laser deposition (PLD) of NiO (111) epitaxial film on the sapphire (α-Al2O3single crystal) substrate and successive hydrogen reduction of NiO. The NiO (111) epitaxial film was deposited on the sapphire (0001) substrate at room-temperature by PLD, and then reduced into the Ni epitaxial film by annealing (300 °C to 500 °C) in the hydrogen-atmosphere. On the other hand, the polycrystalline Ni metal thin film was obtained by reduction of the polycrystalline NiO film, indicating necessity of epitaxial growth for the precursor oxide thin film in the metal epitaxy. The present epitaxy method suggests the possible formation of [Ni/α-Al2O3] epitaxial multilayer via selective reduction of oxide multilayer.
Hydrothermal Synthesis of Zinc-Doped Magnetite Nanoparticles
Authors: Sorescu Monica , Diamandescu Lucian , Tarabasanu-Mihaila Doina , Teodorescu Valentin
Published: April 2011

Hydrothermal techniques have been used to synthesize samples of ZnxFe3−xO4 (x=0.0-1.0) starting with ZnSO4.7H2O/FeSO4.7H2O aqueous solution. The sequence of phases, structural and magnetic properties were followed by X-ray diffraction (XRD), Mössbauer spectroscopy and transmission electron microscopy (TEM). Refinement of the XRD spectra yielded the dependence of the lattice parameters of zinc–doped magnetite and zinc ferrite phase as function of the Zn molar concentration x. As well, the particle diameter was derived as a function of Zn content x. As a function of Zn concentration, the phase content of hydrothermally synthesized samples was found to consist of zinc-doped magnetite, goethite and zinc ferrite. Consistent with the XRD results, Mössbauer spectroscopy data indicate the presence of magnetite and goethite at x≤0.2, magnetite and zinc ferrite at x≤0.9 and pure zinc ferrite only at high zinc concentrations. The presence of different magnetite phases was confirmed by TEM and particles with a size of 50 nm were identified. Our results show that zinc ferrite is formed at high zinc concentration by the hydrothermal method and an acicular component of goethite-magnetite is obtained at low zinc content.
Synthesis of a Magnetic-Dielectric YIG@BaTiO3 Composite via Hydrothermal Processing
Authors: Lin Shin-Wei , Ko Wen-Song , Tung Mean-Jue
Published: April 2011

YIG@BaTiO3 composite was synthesized by a sequential process involving the formation of TiO2 by sol-gel reaction and a subsequent hydrothermal transformation from TiO2 to BaTiO3. TiO2 layer was coated on YIG particle via sol-gel reaction which comprised hydrolysis and condensation reaction of titanium n-butoxide. The pH value of the solution was precisely controlled to ensure that YIG particles could be well dispersed in the solution and the concentrations of TBOT and H2O were adjusted to obtain variant thickness of TiO2 layer. Nano-sized BaTiO3 coating on YIG was achieved by a hydrothermal conversion of the TiO2 shell layer. BaTiO3 shell layer was synthesized in an autoclave at 240°C for 12 hours and the concentration ratio of [Ba]/[Ti] was 1.6. Phases and morphology of the composite are identified by X-ray diffraction and SEM, respectively. Magnetic properties of YIG@BaTiO3 composite were investigated by vibrating sample magnetometer. Coercivity of YIG@BaTiO3 composites with different composition were not affected but the saturated magnetization dropped down with increasing of the volume ratio of BaTiO3. Permittivity of YIG was raised by coating of BaTiO3 layer and was varied from 6 to 60 and 75 by tuning up the volume ratio of BaTiO3 in the composite. The mechanism of the formation of YIG@BaTiO3 composite was also discussed in the article.
Synthesis of Silicon Based Opal by Chemical Reduction of Silica Opal
Authors: Aliev Ali E. , Royer M. A. O. , Zakhidov A. A. , Baughman R. H.
Published: April 2011

By reduction of SiO2 opal in atmosphere of nitrogen (80%)-helium (15%)-hydrogen (5%) gas mixture at various temperatures we tuned the dielectric contrast ratio and band gap of photonic crystal (PC) up to 10 %. The SEM images dose not show any detectible change in lattice parameters, whereas the elemental analysis shows remarkable decrease of oxygen content. The shift of reflectance spectra toward the long wavelength and increase of transmission in infrared region confirm the redaction of silica and partial transformation to the silicon.
Functional Metamaterials Based on Mesoscale Gold Sponges, Particulate Aggregates, and Their Composites with Dielectric Materials
Authors: Cortie Michael , Maaroof Abbas , Smith Geoff B
Published: April 2011

The optical properties of some nanoscale composites may deviate from that expected from a simple law of mixture of their individual components. In these cases the resulting structure can be considered to be a type of “metamaterial”. Here we explore some of the possibilities for nanoscale composite structures comprised of gold and VO2 – the latter being a functional material that undergoes a reversible insulator to metallic phase transition at 68°C. Two microstructures are examined: aggregates of gold nanoparticles surrounded by VO2 as the continuous phase, and its geometric inverse, mesoporous gold sponge with discontinuous VO2 inclusions. A composite, right-angled parallelepiped measuring 40×100×100 nm is taken as representative of the mixture, and calculations of the optical properties performed using the discrete dipole approximation code of Draine and Flatau. The VO2 matrix strongly attenuates the dipole-dipole plasmon resonance of the gold structure, and thermochromic switching of the remaining plasmon resonance occurs
Ferroelectricity from Electron Ordering
Authors: Ikeda Naoahi , Mori Shigeo , Yoshii Kenji , Matsuo Yoji
Published: April 2011

We report ferroelectricity in triangular mixed valence material RFe2O4 (R=Y, Dy, Ho, Er, Tm, Yb, Lu). This ferroelectricity originates from the polar ordering of Fe3+ and Fe2+ or the polar ordering of electrons on Fe3+.
Capacitance Tunability of Magneto-electric Material:Cr2O3 using Ferromagnetic (La,Sr)MnO3 Electrode
Authors: Yokota Takeshi , Kuribayashi Takaaki , Shundo Takeshi , Hattori Keita , Sakakibara Yasutoshi , Gomi Manabu
Published: April 2011

We have investigated the dielectric properties of the Cr2O3 films using ferromagnetic electrode; (La0.66, Sr0.33)MnO3. The relationships between those properties and their crystallinity also have been investigated. The well crystallized sample was exhibited low leakage current density. Although all samples show capacitance decreasing by applying voltages, the decreasing ratio was the largest on the sample with lowest leakage current density. Since the Cr2O3 film with same leakage current density as that sample using non-magnetic electrode didn't show any capacitance changes by applying voltages, it is suggested that the dielectric properties of Cr2O3 film might be affected by the ferromagnetic film.
Doping Effect on the Charge Ordering in LuFe2O4
Authors: Matsuo Yoji , Shinohara Satoshi , Mori Shigeo , Horibe Yoichi , Yoshii Kenji , Ikeda Naoshi
Published: April 2011

Change of the charge ordered (CO) structure by substituting Cu2+ for Fe2+ in LuFe2O4 was investigated by means of the transmission electron microscopy. The CO structure in LuFe2O4 is characterized by the modulated structure with the wave vector of q=1/3[1-13/2] and the average size of the CO domains can be estimated to be about 10-20nm. On the contrary, the Cu2+ substitution in LuFe2O4 destroyed the CO structure drastically and induced characteristic local lattice distortion, which gives rise to characteristic diffuse scattering in the reciprocal space. High-resolution lattice images revealed that there exist nano-scale clusters, which are characterized as the short-range ordering of the Fe3+ and Cu2+ ions on the triangular lattice. In addition, the magnetic measurement revealed that LuFeCuO4 exhibits an antiferromagnetic transition around 50K, which is lower than the Neel temperature of 250K in LuFe2O4.
Piezoresponse in Ferroelectric PZT Thin Films
Authors: Kiselev Dmitry , Bdikin Igor , Movchikova Alena , Kholkin Andrei , Suchaneck Gunnar , Gerlach Gerald
Published: April 2011

Poled ferroelectric lead zirconate titanate (PZT) films comprising a (111) texture on (100)Si/SiO2/(111)Pt substrates were investigated by piezoresponse force microscopy (PFM). Depending on the film thickness, the crystallite orientation varies from purely (111) (related to the Pt bottom electrode orientation) to a more random texture. By PFM, 90° domains with a width of 50 nm were obtained in an individual grain Pb(Pb0.10Zr0.21Ti0.69)O3 − PPZT (10/21/69). It was shown that the virgin (unpoled) films possess large piezoelectric activity comparable to that after local poling (self-polarization effect). This corresponds to a clear predominance of the domains with a polarization oriented from the bottom electrode to the free surface of the film.
Investigation of Epitaxially Grown PbO, TiO2 and ZrO2 as Bridge Layers for Integration of PZT on GaN by MBE
Authors: Gu Xing , Izyumskaya Natalia , Avrutin Vataliy , Morkoç Hadis
Published: April 2011

Epitaxial growth of PbO, TiO2 and ZrO2 has been achieved on MOCVD grown GaN template using oxides MBE with a reactive H2O2 oxygen source. In situ RHEED was used to monitor the growth in-situ. AFM was used to characterize the surface morphology of the thin PbO and ZrO2, which show streaky, 2-D RHEED patterns. XRD pattern indicates that the growth orientation of these oxides are PbO [111]//GaN [0002], ZrO2[100]//GaN [0002] and TiO2[200]//GaN[0002].
Characterization of Ferroelectric Properties of Bi4-xPrxTi3O12 Polycrystals
Authors: Munro Abril , Mata Jorge , Martínez Eduardo , Siqueiros Jesus
Published: April 2011

Effects of Praseodymium doping on the ferroelectric properties of Bi4Ti3O12 were investigated using dense ceramics from room temperature to 730 °C. DRX and XPS studies shows that the structure can accept only 10% of praseodymium without the precipitation of second phases. Thermoelectric analysis and ferroelectric hysteresis measurements were performed and show that the incorporation of praseodymium modified the transition temperature Tc and slightly the polarization values. The incorporation of praseodymium resulted in a variation in the permittivity and in the remanent polarization (2Pr). The polarization characteristics in the samples doping were different to Bi4Ti3O12.
Effect of CuO on Microstructure and Microwave Dielectric Properties of CaTiO3-Ca(Zn1/3Nb2/3)O3 Ceramics System
Authors: Yu Hongtao , Hao Hua , Liu Hanxing , Tian Zhongqing
Published: April 2011

The effect of CuO on the microstructure and microwave dielectric properties of the CaTiO3-Ca(Zn1/3Nb2/3)O3 ceramics prepared by the conventional solid-method has been investigated. Doped with the 0.5∼1.25wt% CuO powder, the system of which the sintering temperatures were lowered exhibited the orthorhombic perovskite. It can effectively promote the microwave dielectric properties of the 0.3CaTiO3-0.7Ca(Zn1/3Nb2/3)O3 system at lower sintering temperature at the level of 1.0wt% CuO additive. The quality factor increases from 10860 to 13900GHz and not any significant change was observed in the TCF value with fixed CuO additive at different sintering temperature.
Dielectric Permittivity Mapping up to 9GHz Region with Non-contact Microwave Probe for Ferroelectric Device
Authors: Kakemoto Hirofumi , Li Jianyong , Harigai Takakiyo , Nam Song-Min , Wada Satoshi , Tsurumi Takaaki
Published: April 2011

Direct observations for high frequency microscopic dielectric distributions in cross sections of a multi-layer ceramic capacitor were carried out using non-contact type microwave probe. The measured data were imaged from the raw data and rounding data process. Using microwave reflection intensity mappings from cross sections of multi-layer ceramic capacitor, the dielectric permittivity distribution in micro-region of a multi-layer ceramic capacitor was measured at room temperature. The spatial resolution was experimentally estimated to be about 10 μm from mappings of the dielectric and inner electrode layers in a multi-layer ceramic capacitor.
Dielectric Tunability Properties and Thermal Stability of (Ba,Sr,Ca)TiO3 Thin Films Prepared by the Sol-Gel Method
Authors: Qin Wei , Chen Wanhai , Wu Wenbiao , Cheng Jinrong , Meng Zhongyan
Published: April 2011

A new family of (Ba1-x-ySrxCay)TiO3 (BSCT) thin films was prepared on Pt(111)/TiO2/SiO2/Si substrates by using sol-gel techniques. BSCT thin films with Ba/Sr/Ca ratio of 15/55/30, 20/45/35 and 25/35/40 were investigated, which were selected at the cubic region in the vicinity of the cubic-tetragonal phase boundary according to the ternary phase diagram of BaTiO3-SrTiO3-CaTiO3. X-ray diffraction analysis indicates that BSCT thin films are of the cubic perovskite structure. No hysteresis window can be observed from the capacitance-voltage curves, reflecting that BSCT thin films are in the paraelectric phase. The dielectric constant and tunability of BSCT thin films were investigated in the temperature range of 200–370 K. The Curie temperature Tc increases with increasing Ba concentration.
Electrical Study of Device Arrays on Thin Film Vanadium Dioxide
Authors: Mani Ramesh G. , Ramanathan S. , Narayanamurti V.
Published: April 2011

The VO2 phase of vanadium oxide is known to exhibit large changes in the electrical and optical properties in the vicinity of the structural phase transition at 68C. Here, we report on the fabrication and study of thin film vanadium oxide (VO2) devices deposited on R-plane sapphire. Thin films prepared by electron beam evaporation have been processed by photolithography into two-terminal strips for electrical measurements. Measurements on such specimens exhibit reproducibility across a chip, in addition to hysteretic transport, and a one-to-two orders of magnitude change in the resistance in the vicinity of the structural transition. In sum, these experiments show that e-beam evaporation of VO2 constitutes a simple and useful approach to realizing devices from this technologically important material.
Reactive Multilayer Foils for Silicon Wafer Bonding
Authors: Qiu Xiaotun , Wang Jiaping
Published: April 2011

In this study silicon wafers were bonded using Al/Ni reactive multilayer foils as local heat sources for melting solder layers. Exothermic reactions in Al/Ni reactive multilayer foils were investigated by XRD and DSC. XRD measurements showed that dominant product after exothermic reaction was ordered B2 AlNi compound. The heat of reaction was calculated to be -57.9 KJ/mol by DSC. With Al/Ni reactive multilayer foil, localized heating can be achieved during bonding process. Both experimental measurements and numerical simulation showed that the heat exposure to the wafers was highly limited and localized. Moreover, leakage test showed that this bonding approach possessed a good hermeticity.
Compression Creep Behavior of the 95.5Sn-(4.3, 3.9, 3.8)Ag-(0.2, 0.6, 0.7)Cu Solders
Authors: Vianco Paul , Rejent Jerome , Kilgo Alice , Martin Joseph
Published: April 2011

The compression creep properties were evaluated for the Pb-free solders 95.5Sn-4.3Ag-0.2Cu (wt.%), 95.5Sn-3.9Ag-0.6Cu, and 95.5Sn-3.8Ag-0.7Cu to determine the effects of small composition differences on time-dependent deformation. The test temperatures were -25°C, 25°C, 75°C, 125°C, and 160°C. The nominal applied stresses were in the range of 2 – 45 MPa. Samples were tested in the as-fabricated condition as well as post-aged at 125°C for 24 hours. Negative creep was recorded for all three alloy compositions. However, the extent of this phenomenon was sensitive to alloy composition and the aging treatment. Creep deformation resulted in the formation of coarsened-particle boundaries within the eutectic regions of the microstructure. The boundaries were comprised of Cu6Sn5and, to a lesser extent, Ag3Sn particles. The minimum creep rate kinetics were evaluated for these solders. The sinh term exponent, n, was 4 – 6 for the Sn-Ag-0.2Cu and Sn-Ag-0.6Cu solders and 1 – 2 for the Sn-Ag-0.7Cu alloy. The apparent activation energy (ΔH) values were in the range of 30 – 70 kJ/mol for all alloys, indicating that a short-circuit or fast-diffusion mechanism controlled creep deformation. The aging treatment did not consistently alter the rate kinetics parameters amongst the alloys. Separating the minimum creep rate data into the low and high temperature regimes, [-25°C, 75°C] and [75°C, 160°C], respectively, showed that bulk diffusion contributed to creep in the higher temperature regime. The ΔH values for the low temperature regime, which indicated that creep was dominated by a fast-diffusion mechanism, were sensitive to solder composition.
Electric Current Induced Brittle Failure of Eutectic Lead and Lead-free Solder Joints with Electroless Ni-P Metallization
Authors: Kumar Aditya , Chen Zhong , Wong C. C. , Mhaisalkar S. G. , Kripesh Vaidhyanathan
Published: April 2011

The mechanical properties of thermally-aged and electric current-stressed eutectic lead (Sn-37Pb) and lead-free (Sn-3.5Ag) solder joints with electroless Ni-P metallization were investigated using tensile testing. Multi-layered test samples, electroless Ni-P/solder/electroless Ni-P, having two electroless Ni-P/solder interfaces were prepared. Tensile testing results showed that for both types of solder, high density electric current causes the brittle failure of solder joint. The eutectic lead solder joint was found to be more prone to current induced brittle failure compared to the lead-free solder joint. In the eutectic lead solder joint, brittle failure always occurred at the cathode side electroless Ni-P/Sn-37Pb interface (where electrons flowed from Ni-P to solder), whereas no such polarity effect was observed in the case of lead-free solder joint.
Parylene-PDMS Bilayer Coatings for Microelectronic and MEMS Packaging
Authors: Lee Hyungsuk , Cho Junghyun
Published: April 2011

Current microelectronic devices and microelectromechanical systems (MEMS) require that packaging costs be reduced with more enhanced device performance. In addition, the packaging materials are often exposed to harsh environments, for which their performance is drastically degraded. Importantly, such devices become lighter and smaller, precluding the use of conventional packaging materials and schemes. Given that, surface coatings can provide an alternative solution for some of the aforementioned issues. Polydimethylsiloxane (PDMS) is a good candidate material in many encapsulating applications but its surface must be effectively protected due to its poor surface properties. In this study, the PDMS surface is coated with the parylene C film through a vapor-phase deposition. Proper surface modification of PDMS is then essential to generate desirable interfacial adhesion and performance between the parylene C and the PDMS. Effects of plasma treatment were examined in this study to evaluate their effectiveness on the surface modification of the PDMS. In order to explore mechanical performances of the bilayer coatings, dynamic nanoindentation and feedback-control nanoindentation testings were employed. In addition, extensive surface characterizations are performed with atomic force microscope (AFM) and optical microscope (OM).
Through Wafer Interconnects - A Technology not only for Medical Applications
Authors: Vogtmeier Gereon , Drabe Christian , Dorscheid Ralf , Steadman Roger , Wolter Dr. Alexander
Published: April 2011

The foremost driver for the development of fully CMOS compatible Through Wafer Interconnects (TWIs) is the need of very large photodiode arrays for detectors, e.g. in computed tomography applications. The front to back-side contact allows the four-side buttable chip placement of the already large chips (20mm × 22mm2). The TWI technology allows an interconnection for chips up to 280μm thickness. This technique does not require any via opening at the font side, thus enabling a metal signal routing on the active side, on top of the interconnection. The application specific optical sensitive front-side of the chip is fully accessible. The production process is separated into three main steps. The first step is the implementation of the special TWI geometry into the CMOS substrate. Depending on the electrical and geometrical requirements of the circuit, different TWI structures are built with deep trenches (up to 280μm), which are passivated and filled with doped poly-silicon. The technologies used in this process, such as DRIE-etching, oxidation and low pressure CVD, are standard CMOS compatible processes. The use of poly-silicon prevents from achieving very low resistivity interconnections but allows the use of all CMOS process steps for an imager production (no temperature limitation – compared to other TWI process flows). The second step is the standard CMOS processing on the substrate already including the TWIs. The third step is a low temperature back-side process starting with wafer thinning down to 280μm or less to open the implemented TWI structure from the back-side. The thickness may be selected depending on the target application. A modified under ball metallization (UBM) process, which could include also re-routing of signals on the back-side, concludes the process flow until the solder ball placement, or similar bond connections.

The special process flow opens a variety of applications which benefit from the full CMOS compatible processing and the accessible front-side.
γ-Irradiation Stimulated Change of Recycled Polypropylene Composites Dielectric Permittivity
Authors: Gafurov Ulmas , Fazilova Z.
Published: April 2011

The γ-irradiation influence on dielectric permittivity (ε′) of recycled polypropylenes (PPR) and of thermoplastic composites γV TDV on its bases has been investigated. It was investigated follows thermoplastic composites: PPR+EPDM, PPR+EPDM+GTR, PPR+EPDM+GTR/plast; EPDM -ethylene-propylene diamine. The permittivity increasing up to dose ∼ 100 kGy one can explained of radiation stimulated peroxide radicals formation, processes of cross-linking and increase of ordering, crystallinity degree. It is supported the measurements of the IR spectra of irradiated samples and by the data of X-ray diffraction measurements.

The dielectric permittivity for the PPR+EPDM and PPR+EPDM+GTR/plast composites have little change up to the dose of γ-irradiated 1500 kGy and the composites have stable dielectric properties. The stable properties is defined the radiation stable of polymer (PPR) matrix. The dose raise more lead to the permittivity decreasing for the plasticized composite PPR+EPDM+GTR/plast. It is result of crystallinity degree reduction and by plasticization of destruction products.
Fabrication of SiN-assisted 0.12um AlGaAs/InGaAs PHEMT and 60GHz-band MMICs for 60GHz WPAN system
Authors: Ahn Hokyun , Lim Jong-Won , Ji Hong-Gu , Chang Woo-Jin , Mun Jae-Kyoung , Kim Haecheon
Published: April 2011

In this paper, the fabrication technology of SiN-assisted 0.12um double deck T-gate AlGaAs/InGaAs p-HEMT and 60GHz-bands MMICs for the high rate personal area network (WPAN) system was described. The effect of the gate shape such as the 1st-deck and the 2nd-deck gate head size on the DC and RF characteristics of the p-HEMT device and the device performance at the optimum gate head size were also presented. At 0.22um of the optimum 1st-deck gate head size and 1um of the 2nd-deck head size, the p-HEMT device with two finger gates of 0.12um length × 50um width shows an extrinsic transconductance of 529mS/mm and a threshold voltage of -1.19V. The cut-off frequency and the maximum frequency of oscillation were 94.7GHz and 189.1GHz, respectively. The gate shape of the p-HEMT device such as a gate head size is correlated to parasitic capacitances including Cgs which have effects on RF performances including a cut-off frequency (fT) and a maximum frequency of oscillation (fmax).
3-D Integration Latest Developments at LETI
Authors: Charlet Barbara
Published: April 2011

We review the latest 3-D integration developments performed in LETI, giving some devices integration examples and discussing the achieved performances. Direct bonding and layer transfer (smart cut™) is now largely used to process innovative substrates like: SOI, SSOI, GeOI, … and others. This type of new substrate can play a crucial role in 3D structure integration and can answer the requirements for new challenging performances.

3-D integration approach has been used and will be presented in the following topics: advanced packaging by neo-wafers, chip to wafers integration, hetero-structures integration and wafer to wafer concept (front and back-end application). The examples of neo-wafer rebuilding for advanced packaging, the hetero- structure achieved by chip-to-wafer or wafer-to-wafer bonding and front-end and back-end architecture are discussed regarding the 3-D integration challenging requirements. The challenging cases of wafer-level integrated demonstrators for high density 3D inter-chips connections and wireless interconnections are presented. For some examples we give also the first electrical performances achieved with representative demonstrators.
Fabrication and Evaluation of 3D Packages with Through Hole Via
Authors: Jang Dong Min , Lee Kwang Yong , Ryu Chung Hyun , Cho Byeong Hoon , Oh Tae Sung , Kim Joung Ho , Lee Won Jong , Yu Jin
Published: April 2011

System in package (SiP) is a superb candidate to enhance the area efficiency and performance of electronic packaging. Here, recent work on stacked chip type 3D SiP with vertically interconnected through hole vias are reported. The process includes; formation of 50um-diameter via holes, conformal deposition of SiO2 dielectric layer, deposition of Ta and Cu barrier layers, via filling by Cu electroplating, Cu/Sn bump formation for multi-chip stacking, and finally chip-to-PCB bonding using Sn-3.0Ag-0.5Cu solder and ENIG pad. A prototype 3D SiP stacked up to 10 layers was successfully fabricated.

A high frequency electrical model of the through hole via was proposed and the model parameters were extracted from measured S-parameters. The proposed model was verified by TDR/TDT (time domain reflectometry/time domain transmission) and eye-diagram measurement. Contact resistances of Cu via and bump joint were presented.
Hydrogen Desorption from MgH2 Based Nano-Micro Composites
Authors: Bonetti Ennio , Fiorini Anna Lisa , Pasquini Luca , Abazovic Nadica , Montone Amelia , Vittori Antisari Marco
Published: April 2011

The microstructure and hydrogen sorption behaviour of MgH2 based nano-hydrides with different additives prepared by ball milling and inert gas condensation has been investigated by XRD, Differential Scanning Calorimetry and Mechanical Spectroscopy. Preliminary results on materials with similar composition and different nanostructures show that suitable mechanical processing and additive additions induce in the nanostructured composites tailored channels for improved ab/de-sorption kinetics at reduced temperatures.
Supported High Temperature Protonic Films Produced by Solid State Reaction
Authors: Meulenberg Wilhelm A , Serra José M.
Published: April 2011

This work presents the last progresses in the development of thin oxidic proton conducting electrolytes supported on mixed conducting cermets making use of a solid state reaction. The procedure includes preparation routes applying solid state transformation of an already-gastight oxide layer (typically doped zirconia and ceria) by reacting with an alkali-earths layer (stoichiometric amount) deposited by screen printing on top of that. This kind of supported films can find application as IT-SOFC, H2-membranes and advanced catalytic converters. Thin-film (∼5μm) proton conducting membranes with the nominal composition as for instance BaZr0.85Y0.15O3-δ and BaCe0.8Gd0.2O3-δ were prepared over porous Ni-8YSZ or Ni-CGO substrates by solid state reaction. The produced films are gastight with a homogeneous composition, and showed a highly crystalline cubic perovskite structure. The solid state reaction promoted the formation of (i) a different grain size distribution from 0.1 μm for barium zirconate to 2-3μm for barium cerate, and (b) the formation of a porous fibrous top-layer (for barium zirconate) or a just flat surface (for strontium zirconate), depending on the exact composition of the reacting oxides.
Ionic Conduction in Nanoscale Films of Yttrium-Doped Barium Zirconate
Authors: Shim Joon Hyung , Gur Turgut M , Prinz Fritz B
Published: April 2011

Proton conductivity of yttrium-doped barium zirconate grown on MgO(100) using pulsed laser deposition (PLD) has been explored as a function of film thickness (60∼670nm) related to crystal and grain structure in the nano scale. Highly textured thin film (60nm) without significant grain separation showed high ionic conductivity close to the bulk BYZ value while thick polycrystalline samples showed lower values with clear grain and grain boundary formation.
Refractory Cathode Investigation for Single-Step Co-Fired Solid Oxide Fuel Cells (SOFCs)
Authors: Zink Peter A. , Yoon Kyung Joong , Huang Wenhua , Gopalan Srikanth , Pal Uday B. , Seccombe Donald A.
Published: April 2011

A single step co-firing process for fabricating solid oxide fuel cells (SOFCs) requires refractory electrodes to prevent excessive sintering of the electrode while facilitating full-density sintering of the electrolyte. Single cell current-potential curves and impedance measurements indicate that the majority of the performance losses occur in the cathode and are due to activation polarization. A-site deficient calcium and cerium doped lanthanum ferrite cathode powders were synthesized and investigated as possible refractory cathode materials with low activation polarization losses. Four-probe conductivity measurements indicated that all compositions were suitable as cathodes. However, reactivity with YSZ reduced the conductivity by as much as two orders of magnitude, too low for use as a cathode. These refractory cathode compositions could be effective if a suitable barrier layer is applied to prevent reaction with YSZ. Experiments will investigate the applicability of a doped-ceria barrier layer to prevent reaction between the lanthanum ferrite cathode layer and the YSZ electrolyte layer.
LixCn as Anode Material for Lithium Ion Batteries
Authors: Xie Haiming , Yu Haiying , F. Jalbout Abraham , Yang Guiling , Pan Xiumei , Wang Rong-Shun
Published: April 2011

We design a way that the anode hosts provide lithium ion in lithium ion battery operation. If the limiting factors of the cathode materials are less, there will be more alternatives for it. It was proven to be successful by two kinds of test cells based on LixCn as anode material, and β-FeOOH or Cr8O21 as cathode materials. Their theoretical capacities are much higher than those present electrode materials. Unlike the lithium secondary batteries with lithium metal foil or lithium alloy as anode, this type of lithium ion batteries with LixCn as anode prohibit dendrite formation during charging-discharge process. The idea of lithium ion sources coming from the anode can come true successfully as a result that steady protecting solution be sought for LixCn.
Effect of ZnO Coating on the Electrochemical Performance of LiMn1.5Ni0.5O4 Cathode Material
Authors: Singhal Rahul , Tomar Maharaj S , Burgos Juan G , Kumar Arun , Katiyar Ram S
Published: April 2011

LiMn1.5Ni0.5O4 cathode material was prepared by sol-gel method and annealed at 850°C for 15 hrs. The prepared powder was coated with ZnO by dissolving zinc acetate in methanol and LiMn1.5Ni0.5O4 powder was mixed in this solution followed by the continuous stirring for 4 hr. The LiMn1.5Ni0.5O4 and ZnO coated LiMn1.5Ni0.5O4 powder was characterized using X-ray diffraction, TEM and Raman spectroscopy. The coin cell was fabricated using LiMn1.5Ni0.5O4 and ZnO coated LiMn1.5Ni0.5O4 as cathode materials, LiPF6, dissolved in EC/DMC (1:1 wt ratio) as electrolyte, and Li foil as anode. The cyclic voltammetric and charge-discharge characteristics were carried out for the coin cell using LiMn1.5Ni0.5O4 and ZnO coated LiMn1.5Ni0.5O4 cathode materials. It was found that the ZnO coated LiMn1.5Ni0.5O4 cathode materials showed improved discharge capacity (∼146mAh/g) as compared to the pure LiMn1.5Ni0.5O4 (∼140mAh/g). The discharge capacity retention after 50 cycles was found to be about 94% and 97% for LiMn1.5Ni0.5O4 and ZnO coated LiMn1.5Ni0.5O4 cathode materials, respectively.
Influence of Lithium Content on Performance of Layered Li1+z[Ni0.45Mn0.45Co0.1]1-zO2 in Lithium Ion Batteries
Authors: Xiao Jie , Chernova Natasha A. , Whittingham M. Stanley
Published: April 2011

Li1+z[Ni0.45Mn0.45Co0.1]1-zO2(0.8≤1+z≤1.2) has been synthesized by the co-precipitation method. It was found that 5% excess lithium must be added to obtain the desired composition. XRD results show that an apparent single-phase structure appears except for the lowest lithium content. The layered character of the structure increases with increasing lithium content and Rietveld refinement reveals that cation disorder decreases rapidly as more lithium is added. This conclusion is further confirmed by magnetic studies in which only Li0.8[Ni0.45Mn0.45Co0.1]1.2O2 and Li0.9(Ni0.45Mn0.45Co0.1)1.1O2 show magnetization hysteresis loops. The electrochemical behavior of this series of samples is compared to figure out the best lithium to transition metal ratio.
Electrochromic Nickel Hydroxide Thin Films Chemically Deposited
Authors: Araceli Monica , Vidales-Hurtado  , Mendoza Arturo
Published: April 2011

Nickel hydroxide thin films were deposited on ITO-coated glass substrates by the chemical bath deposition method. Two formulations using nickel nitrate were employed to obtain the films. The first one is through coordination compounds by using an ammonia complex producing the well crystallized phase β(II)-Ni(OH)2. The second formulation is based on the decomposition of urea at temperatures above of 90 °C, which promotes the deposition of the turbostratic phase α(II)- Ni(OH)2. After thermal annealing in air at temperatures of 250-300 °C, the β(II) films retain their polycrystalline structure, while the α(II) films are partially transformed to NiO. The electrochromic behavior of the films was tested by cyclic voltammetry in a three electrodes configuration cell. Also, chronoamperometry and in-situ single wavelength transmittance measurements were carried out to evaluate the switching time response. From Raman spectroscopy the structural transformations between colored and blanched states were studied. In the colored state most of the films show a mixture of β(III) and γ(III) phases of NiOOH, and in one case the Ni2O3 phase was found. It is shown that the films can exhibit high optical contrast depending on the processing conditions and electrical potential applied.
Effect of Water on the IR Properties of Mg2+ Intercalated Electrochromic Nb2O5 Thin Films
Authors: Agarwal Gargi , Reddy G B
Published: April 2011

Sol-gel derived Nb2O5 thin films were intercalated with Mg2+,using the non-aqueous solution of Mg(ClO4)2 in propylene carbonate (pc) as the electrolyte. 2% and 4% ( volume %) water was added to the electrolyte to study the effect of water on the electrochromic properties of Nb2O5. This paper presents the changes in optical and structural properties of the intercalated films with and without water in the electrolyte. The ratio (x) of the Mg2+ and Nb atoms has been controlled by optimizing the intercalation duration under a constant current density. The fall in transmittance on intercalation (for x= 0.8) increased by 15% with 4% water in the electrolyte, compared to the film intercalated without water. FTIR studies show that water is incorporated in the films on intercalation and small quantities of Mg(OH)2 and Nb-OH are formed along with Mg-O-Nb bonds. The presence of water in electrolyte decreases water content in the films and enhances the formation of Mg(OH)2, Mg-O-Nb and Nb-OH bonds. The recovery of Mg2+ on deintercalation is slightly reduced in presence of water in the electrolyte. The cyclic stability of the films intercalated without water is more than that of the films intercalated in presence of water.
High Performance Single Step Co-Fired Solid Oxide Fuel Cells
Authors: Yoon Kyung Joong , Gopalan Srikanth , Pal Uday B.
Published: April 2011

Anode-supported planar solid oxide fuel cell (SOFC) was successfully fabricated by a single step co-firing process. The cell comprised of a Ni + yittria-stabilized zirconia (YSZ) anode, a YSZ electrolyte, a Ca-doped LaMnO3 (LCM) + YSZ cathode active layer, and an LCM cathode current collector layer. The fabrication process involved tape casting of the anode, screen printing of the electrolyte and the cathode, and single step co-firing of the green-state cells at 1300°C for 2 hours. The maximum power densities were 1.50W/cm2 at 800°C, and 0.87W/cm2 at 700°C with humidified hydrogen (97% H2-3% H2O) as fuel and air as oxidant. The experimentally measured I-V curves were fitted into a polarization model to obtain cell parameters including the area specific ohmic resistance, exchange current density, effective binary diffusivity of hydrogen and water vapor in the anode, and that of oxygen and nitrogen in the cathode. The cell was also tested at 800°C with various compositions of humidified hydrogen to evaluate the cell performance at high fuel utilization, and the maximum power densities were 1.30W/cm2 with 75.7% H2-24.3% H2O, 0.94W/cm2 with 49.4% H2-50.6% H2O, and 0.49W/cm2 with 27.3% H2-70.7% H2O.
Scandia – Stabilized Zirconia: Effect of Dopants on Surface/Grain Boundary Segregation and Transport Properties
Authors: Smirnova A. , Sadykov V. , Muzykantov V. , Mezentseva N. , Ivanov V. , Zaikovskii V. , Ishchenko A. , Sammes N. , Vasylyev O. , Kilner J. , Irvine J. , Vereschak V. , Kosacki I. , Uvarov N. , Zyryanov V.
Published: April 2011

The nanocrystalline samples of 10wt.%Scandia stabilized Zirconia (10ScSZ) and 1wt.%Ceria doped ScSZ (1Ce10ScSZ) prepared via co-precipitation route were characterized and compared to commercially available samples regarding their transport properties and electrical conductivity. The results of oxygen isotope experiments show that for Zirconia-based electrolytes, the rate of heteroexchange is lower than that for Samaria-doped Ceria. The results of Secondary Ions Mass Spectrometry (SIMS) indicate that all admixed components are present both in the surface layer and the bulk of the studied samples with pronounced segregation on the grain boundary. The highest total conductivity is observed for DKKK sample. In the range of 600-400°C the highest conductivity observed for synthesized nanocrystalline 1Ce10ScSZ sample is explained by the effect of segregated Scandia doped Ceria surface layers.
Safety Characteristics of the Li4Ti5O12/LiMn2O4 Li-Ion Battery
Authors: Belharouak Ilias , Lu Wenquan , Amine Khalil
Published: April 2011

Li4+xTi4O12 and Li1-yMn2O4 materials have been respectively prepared by a chemical lithiation of Li4Ti4O12 in the presence of an excess of butylithium (LiC4H9) in hexane solution and chemical delithiation of LiMn2O4 spinel using NO2BF4 oxidizer in an acetonitrile medium. The thermal gravimetric results show that Li1-yMn2O4 releases oxygen starting from 200°C with an overall oxygen loss of 6 wt% at 500 °C, whereas Li4+xTi4O12 gains oxygen starting from 200 °C with an overall oxygen gain of 4 wt % at 500 °C. The reactivity of the Li4+xTi4O12 and Li1-yMn2O4 powders in the presence of electrolytes was investigated by a differential scanning calorimetry (DSC) between room temperature and 375°C, and compared to a lithiated graphite in the case of the Li4+xTi4O12 negative electrode material.
Influences of Microstructures of the Cathode/Electrolyte Interface on the Electrochemical Properties of All Solid-State Li-ion Batteries
Authors: Kishida Kyosuke , Wada Naoyuki , Yamaguchi Yuji , Tanaka Katsushi , Iriyama Yasutoshi , Ogumi Zempachi , Inui Haruyuki
Published: April 2011

Two types of samples containing different La2/3-xLi3xTiO3 (LLT) solid electrolyte /LiCoO2 cathode interfaces were prepared by depositing LiCoO2 on polycrystalline LLT with two different surface finishes: cleaved and polished surfaces. Electrochemical properties of the samples were analyzed by cyclic voltammetry (CV). Microstructures of the LLT/LiCoO2 interfaces were investigated by scanning electron microscopy and transmission electron microscopy. Cyclic voltammograms of the cleaved sample show that the anodic and cathodic peaks respectively shift to higher and lower potential with the number of cycles, while those for the polished samples do not change much during cycles of potential sweeps, indicating the higher stability for the polished samples upon insertion and extraction of lithium ion. The LiCoO2 thin-film cathode is epitaxially deposited with the orientation relationships: {110}LLT//{1120}LiCoO2 and <001>LLT//<4401>LiCoO2 for both samples with different geometric configurations of the interfaces to the Li layers in the LiCoO2. Amorphous regions are observed to exist in places at the interface only in the polished samples. The geometric configuration of the interface and the existence of the amorphous regions are considered to have great influences on the stability of the LLT/LiCoO2 interfaces upon charge / discharge operations.
Microfabricated Solid State Thin Film Lithium Batteries
Authors: Salot Raphael , Salot Raphael , Pereira-Ramos Jean-Pierre
Published: April 2011

This work presents recent advances in the development and the integration of a solid state thin film battery, to work as a high voltage energy source for RF-MEMS powering. Micro-electro-mechanical systems require similarly miniaturized power sources. Up to day, microbatteries are realized with mechanical masks, this method doesn't allow dimensions below several decades of mm2 of active area, and besides the whole process flow is done under controlled atmosphere so as to ensure materials chemical stability (mainly lithiated materials). Within this context, Microelectronics micro-fabrication procedures (photolithography, Reactive Ion Etching…) are used to reach both miniaturisation (100×100 μm2 targeted unit cell active area) and microelectronic IC technological compatibility. The whole process is realized in clean room environment. The thin film battery is composed of three active layers. First the positive electrode layer of crystalline vanadium pentoxide c-V2O5, the next level presents then the solid state electrolyte, a glassy ionic conducting material commonly known as “LiPON”. Finally, a negative electrode top level is realized by the evaporation of metallic lithium. The total stack thickness is of about 10 μm. A final wafer level packaging step is then realized to avoid reactivity with air and moisture. Specific attention will be put on the microfabrication processes developed for the positive electrode and the electrolyte (etching chemistry, resist stripping…). Several electrochemical characterizations (spectroscopic electrochemical impedance, charge-discharge cycling) were performed before and after micro-fabrication process steps so as to evaluate any possible effect on the electrochemical behaviour of the different studied layers.
Temperature Dependence Study of Gas Permeability in Metal Doped Composite Polymeric Membranes
Authors: Vijay Yogesh Kumar , Jain Anil Kumar , Acharya Naveen Kumar , Awasthi Kamlendra , Kulshrestha Vaibhav
Published: April 2011

Polycarbonate (PC) membrane and PC based hydrogen active intermetallic compound Fe0.5Ti0.5 particles doped composite membrane have been prepared by solution cast method. The membranes have been characterized by H2 and CO2 permeability and selectivity measurements with increasing temperature. Higher gas permeation has been observed with increasing temperature. In case of doped composite membrane H2/CO2 gas pair selectivity first increases then decreases with temperature whereas in case of pure PC it decreases with temperature. The effect of doping increases the activation energies for permeation of H2 and CO2 in the doped membrane in comparison to pure PC. Doping was found to suppress plasticization effect in polycarbonate. The doped membrane was analyzed by optical micrograph and XRF study.
Mechanical-to-Electrical Energy Conversion of Thin-Film Piezoelectric Diaphragms
Authors: Morris Dylan J , Robinson Michelle C , Weiss Leland W , Richards Cecilia D , Richards Robert F , Bahr David F
Published: April 2011

A micro (∼1 cm3) dynamic heat engine, capable of producing electrical power from lowgrade heat sources, utilizes a micro-machined diaphragm with a piezoelectric element as a The electromechanical coupling of a piezoelectric diaphragm under large initial stresses and/or large deflections – in the membrane limit – is described here. A simple model is derived for electromechanical transduction of a pressurized piezoelectric membrane and an experiment is described to measure it. Electromechanical coupling initially increases as the square of the center-point deflection as the residual stress is overcome. In the limit of large pressures, the electromechanical coupling approaches a limit that is predicted by the model.