bluuebunny/crossref_metadata_2025 huggingface dataset:
Epitaxial Growth of Ge1-xSnx by Reduced Pressure CVD Using SnCl4 and Ge2H6
Authors: Wirths Stephan , Buca Dan , Tiedemann A.T. , Holländer Bernhard , Bernardy Patric , Stoica Toma , Grützmacher Detlev , Mantl Siegfried
Published: March 2013

The epitaxial growth of Ge and GeSn on Si(100) is studied in the low temperature regime by reduced pressure chemical vapor deposition using showerhead technology. Most emphasis is placed on the growth kinetics in the low temperature regime of 375oC to 500oC which is characterized by surface limited reactions. Using Ge2H6 precursor low activation energy of 0.7 eV was determined for H2 carrier gas which further decreases to 0.5 eV if N2 is used. GeSn layers with 10 and 6.5 at.% Sn are obtained at growth temperatures of 375oC and 400oC respectively, using Ge2H6 and SnCl4 as precursors. All Ge and GeSn layers are of high crystalline quality.
Growth of Ge1-xSnx Alloys Using Combined Sources of Solid Tin and Gaseous Germane
Authors: Su Shaojian , Cheng Buwen , Zhang Dongliang , Zhang Guangze , Xue Chunlai , Wang Qiming
Published: March 2013

In the paper, we report the growth of Ge1-xSnx alloy by using combined sources of solid Sn and gaseous GeH4. In order to prevent Sn surface segregation, Ge1-xSnx was grown at a very low temperature that the decomposition of GeH4 is extremely slow. The growth might be stopped at some stage. For further investigation, digermane and trigermane are suggested to replace germane for the synthesis of Ge1-xSnx alloys by using combined sources.
Growth and Characterization of Heteroepitaxial Layers of GeSiSn Ternary Alloy
Authors: Yamaha Takashi , Nakatsuka Osamu , Takeuchi Shotaro , Takeuchi Wakana , Taoka Noriyuki , Araki Koji , Izunome Koji , Zaima Shigeaki
Published: March 2013

We have examined the epitaxial growth of Ge1-x-ySixSny layers on Ge substrates with a Sn content of 3~15% with low temperature molecular beam epitaxy method. The Ge1-x-ySixSny layers are psuedomorphically grown on Ge substrates with high crystalline quality. The surface morphology of the Ge1-x-ySixSny layers with a Sn content below 7% shows very flat and uniform, although surface roughening occurs in the sample with a Sn content as high as 15% provably due to the Sn precipitation. We also roughly estimated the energy band structure with liner approximation calculation. The energy bandgap of Ge1-x-ySixSny alloy prepared in this study is expected to be 0.8~1.0 eV at the L or X point.
Single Crystalline GeSn on Silicon by Solid Phase Crystallization
Authors: Lieten Ruben R. , Decoster Stefan , Menghini Mariela , Seo Jin Won , Vantomme Andre , Locquet Jean-Pierre
Published: March 2013

We investigate the crystallization of amorphous GeSn layers on silicon substrates. Amorphous GeSn layers are deposited on silicon substrates kept at approximately room temperature by molecular beam epitaxy. Thermal annealing transforms these layers into single crystalline GeSn. Structural investigation shows excellent structural quality for layers with 4.5% Sn. Furthermore the surface and interface are smooth, especially when considering the relaxation of the layers. The surface root mean square roughness is smaller than 1 nm. Finally, we show an increased optical absorption for the GeSn layers with respect to Ge, which is promising for integration of optical devices on silicon substrates.
(Invited) Tin-Incorporated Source/Drain and Channel Materials for Field-Effect Transistors
Authors: Yeo Y. C. , Han Genquan , Gong Xiao , Wang Lanxiang , Wang Wei , Yang Yue , Guo Pengfei , Liu Bin , Su Shaojian , Zhang Guangze , Xue Chunlai , Cheng Buwen
Published: March 2013

We discuss technologies for the incorporation of substitutional Sn in the source/drain regions for strain engineering of SiGe and Ge channel MOSFETs. We also discuss recent work on the realization of GeSn channel p-MOSFETs and n-MOSFETs.
(Invited) GeSn Channel n and p MOSFETs
Authors: Gupta Suyog , Chen Robert , Vincent Benjamin , Lin Dennis , Magyari-Kope Blanka , Caymax Matty , Dekoster Johan , Harris James S , Nishi Yoshio , Saraswat Krishna C.
Published: March 2013

Semiconducting germanium tin (GeSn) alloy has recently emerged as a promising candidate material for optoelectronics and high performance CMOS devices because of its tunable direct bandgap and potential for high electron and hole mobilities. In this work, we perform detailed theoretical analysis to gauge the performance benefits of GeSn as a CMOS channel material. pMOSFETs fabricated on GeSn have been shown to outperform Ge. GeSn n-channel devices have been successfully fabricated and factors limiting its performance are investigated, potential solutions are presented.
High Hole Mobility in Strained Germanium-Tin (GeSn) Channel pMOSFET Fabricated on (111) Substrate
Authors: Han Genquan , Su Shaojian , Yang Yue , Guo Pengfei , Gong Xiao , Wang Lanxiang , Wang Wei , Guo Cheng , Zhang Guangze , Xue Chunlai , Cheng Buwen , Yeo Y. C.
Published: March 2013

We report the demonstration of strained GeSn channel pMOSFETs on (111)- and (100)-oriented Ge substrates. The Sn composition is 4.1%. The device interface is passivated using (NH4)2S solution. Compared to devices on Ge(100), GeSn pMOSFETs on Ge(111) demonstrate a 20% enhancement in effective hole mobility at an inversion charge density (Qinv) of 2 × 1013 cm-2.
Fabrication and Negative Bias Temperature Instability (NBTI) Study on Ge0.97Sn0.03 P-MOSFETs with Si2H6 Passivation and HfO2 High-k and TaN Metal Gate
Authors: Gong Xiao , Su Shaojian , Liu Bin , Wang Lanxiang , Wang Wei , Yang Yue , Cheng Ran , Kong Eugene , Cheng Buwen , Han Genquan , Yeo Yee-Chia
Published: March 2013

We report the demonstration of Ge0.97Sn0.03 P-MOSFETs, featuring low temperature Si2H6 passivation, HfO2 high-k dielectric and TaN metal gate. Ge0.97Sn0.03 P-MOSFET with high drive current and negligible hysteresis was realized. NBTI characterization was performed to investigate the off-leakage, suthreshold swing, peak transconductance degradation and threshold voltage shift under stress. Excellent device reliability characteristics were observed.
Si/SiGe Thermoelectric Generators
Authors: Paul Douglas J , Samarelli Antonio , Ferre Llin Lourdes , Zhang Yuan , Weaver John M.R. , Dobson Phil S. , Cecchi Stefano , Frigerio Jacopo , Isa Fabio , Chrastina Daniel , Isella Giovanni , Etzelstorfer Tanja , Stangl Julian , Müller Gubler Elisabeth
Published: March 2013

Thermoelectric materials have great potential for a range of energy harvesting applications. The thermoelectric performance of Ge/SiGe heterostructures is presented with the aim of developing materials to be used as power sources for autonomous sensing applications. Seebeck coefficients up to 279.5 {plus minus} 1.2 µV/K with electrical conductivities of 77,200 S/m are demonstrated at room temperature with power factors of 6.02 {plus minus} 0.05 mW m-1K-2.
Germanium Tin Tunneling Field Effect Transistor for Sub-0.4 V Operation
Authors: Yang Yue , Low Kain Lu , Guo Pengfei , Wang Wei , Han Genquan , Yeo Y. C.
Published: March 2013

Germanium Tin (Ge1-xSnx) as a group IV material has a direct and small band-gap for x > 0.11, which is attractive for the application in tunneling field-effect transistor (TFET). In this work, the design of Ge1-xSnx TFET operating at low supply voltages is investigated by simulation. Device simulation results show that Ge1-xSnx-based TFET can achieve high tunneling current and has potential for logic applications using sub-0.4 V supply voltage.
Ge Surface-Energy-Driven Secondary Grain Growth for Vertical Channel in 3D NAND Flash Memories
Authors: Lee Sangsoo , Son Yong-Hoon , Yoon Euijoon
Published: March 2013

The Ge surface-energy-driven secondary grain growth (SEDSGG) technique is demonstrated here for vertical channel in 3D NAND flash memories. The as-deposited polycrystalline Ge films via rapid thermal annealing show a dominant (111) texture, grain enlargement up to approximately 1 um, and a microstructure with a very low intra-grain defect density. With an increase in the annealing temperature and time, the distribution of the (111) nominal orientations also increases, thus accounting for the SEDSGG of the Ge films. These Ge SEDSGG films show relatively high carrier mobility (163 cm2/Vs) according to the Hall effect measurements.
(Invited) Microstructure Development in Epitaxially Grown In Situ Boron and Carbon Co-Doped Strained 60% Silicon-Germanium Layers
Authors: Reznicek Alexander , Adam Thomas N , Li Jinghong , Zhu Zhengmao , Murphy Richard , Bedell Stephen W. , Paruchuri Vamsi , Sadana Devendra K.
Published: March 2013

Future generations of silicon based integrated circuit technology require carrier concentrations in excess of the equilibrium dopant concentrations. In-situ doping during the epitaxial growth is an attractive alternative to place dopants where needed with tunable concentrations and hyper-abruptness. In this work we study the incorporation of boron or boron and carbon co-doping into fully strained high percentage (60%) Silicon-Germanium. We will discuss the epitaxial growth and dopant incorporation, and its effects on strain compensation due to the dopant atoms. The main focus will be on defect generation in highly strained doped SiGe layers.
In Situ Boron (B) Doped Germanium (Ge:B) Grown on (100), (110), and (111) Silicon: Crystal Orientation and B Incorporation Effects
Authors: Han Genquan , Zhou Qian , Guo Pengfei , Wang Wei , Yang Yue , Yeo Y. C.
Published: March 2013

We investigate the growth of in situ boron (B) doped Ge (denoted as Ge:B) on Si(100), (110) and (111) substrates at low temperature using an ultra-high vacuum chemical vapor deposition (UHVCVD) tool. The growth rate of Ge:B on Si(100) is higher than that on Si(110) at 320 ˚C. The growth of Ge:B on Si(111) achieves 3D quantum dots at 320 ˚C and continuous film at 300 ˚C. The growth rate of Ge:B on Si(111) at 300 ˚C is much lower than other two orientations at 320 ˚C. For all the orientations, Ge:B shows a higher growth rate than intrinsic Ge.
(Invited) Materials Integration for III-V/SiGe+CMOS Integrated Circuit Platforms
Authors: Fitzgerald Eugene A.
Published: March 2013

We review progress in III-V+Si CMOS integration.
(Invited) Heterogeneous Integration of III-V Devices and Si CMOS on a Silicon Substrate
Authors: Kazior Thomas E. , LaRoche J. , Hoke W.
Published: March 2013

Standard Si CMOS and SiGe BiCMOS enable unparalleled integration density, yield, and functionality on a single chip. In addition to realization of high performance mixed signal circuits, such as data converters, there have been many impressive demonstrations of highly integrated RF chips, including full multi-element phased arrays at mm-wave frequencies. However, the performance is not ideal because silicon cannot compete with III-V technologies in terms of power density, efficiency, noise figure, dynamic range or linearity, and speed. Heterogeneously integrating III-V devices with the CMOS gives the designers state of art III-V performance combined with the integration density and functionality of silicon. We present the status of the direct growth/fabrication of InP HBT and GaN HEMT materials/devices on a silicon substrate containing high density Si CMOS. The integration process is similar to the SiGe BiCMOS process and can be considered a III-V BiCMOS process.
(Invited) Hybrid Wafer bonding and Heterogeneous Integration of GaN HEMTs and Si (100) MOSFETs
Authors: Lee H.-S. , Li Z. , Sun M. , Ryu K. , Palacios Tomas
Published: March 2013

Nitride-based semiconductors have received considerable attention during the last decade due to their outstanding properties for optoelectronic, high frequency, and high power applications. The integration of GaN and Si (100) devices on the same chip would enable a vast array of new applications, from novel power distribution schemes in Si microsystems, to power digital-toanalog converters and new opportunities for optoelectronic devices integrated on a Si platform. This paper aims to summarize some of the recent results on the heterogeneous integration of GaN and Si (100) devices and circuits by using a hybrid 4" wafer bonding technology.
(Invited) Scalable GaN-on-Silicon Using Rare Earth Oxide Buffer Layers
Authors: Arkun F. Erdem , Lebby Michael , Dargis Rytis , Roucka Radek , Smith Robin S. , Clark Andrew
Published: March 2013

Growth of GaN epilayers on silicon (111) is achieved by using a rare earth oxide buffer layer technology. The use of the REO material system allows strain engineering of the silicon wafers prior to GaN growth in order to mitigate stresses formed during the growth and subsequent cooling process. Alloying of oxides with more than one rare earth element allows compositional and lattice parameter control of the REO material and thereby imparting different strains into the silicon wafer. The wafer bow of the REO/Si heterostructures is also a found to be dependent on the thickness of the oxide layers grown. Growth of GaN on REO/Si templates result in lower bow compared to growth on silicon wafers alone.
Formation and Characterization of Nickel Germanosilicide on Si1-xGex/Si/SiO2/Si
Authors: Yoo Woo Sik , Hasuike Noriyuki , Harima Hiroshi , Yoshimoto Masahiro
Published: March 2013

TiN capped Ni/Si1-xGex/Si/SiO2/Si wafers are prepared to investigate the formation of nickel germanosilicides in the temperature range of 235oC ~ 400oC in 1 atm N2. The annealing was done in a stacked hotplate system for 10 min (wafer residence time in the heater chamber). The Ge content of 80 nm-thick Si1-xGex layers was varied between 15 and 30 at%. Sheet resistance of thin film stacks were measured using a four point probe as a function of annealing temperature and Ge content. Multiwavelength micro-Raman measurements and X-ray diffraction measurements were performed to investigate crystallographic phases and reaction mechanisms of resulting nickel germanosilicides. Excitation wavelength dependence of Raman measurements was found and optimum excitation wavelength was experimentally determined. Clear correlation among sheet resistance, X-ray diffraction and Raman spectra was found as a function of annealing temperature and Ge content. A combination of X-ray diffraction and multiwavelingth micro-Raman spectroscopy was found to be very promising as in-line monitoring techniques.
(Invited) Thin Film Magnetic Heads - Early Inventions and Their Ongoing Impact on Magnetic Storage and on Electrochemistry
Authors: Romankiw Lubomyr T. , Krongelb Sol
Published: March 2013

Although many researchers in the 1960s hoped to use LSI techniques to batch fabricate magnetic read/write heads for data storage, building these devices entailed a much different set of requirements than LSI was addressing in circuit chip fabrication. Electroplating through a mask proved to be the way to pattern the magnetic elements and copper conductors of a thin film head, but this technology had to be integrated with a host of additional inventions to manufacture the device. This paper outlines the key inventions that had to be made as the head evolved from a laboratory demonstration to a manufactured product. The basic processes that were used to build the first thin film heads are still used to fabricate the heads in today's magnetic storage systems. The technology has also found its way into such diverse microelectronic applications as MEMS, NEMS, electronic packaging, semiconductor chip fabrication and, more recently, solar devices. The success of electroplating as one of the key processes in manufacturing the head has put a new focus on electrochemistry in both academia and industry.
(Invited) Reversible Change of Magnetism in FePt Films by Electrochemical Charging in a LiClO4 Based Electrolyte
Authors: Leistner Karin , Lange Norman , Oswald Steffen , Schultz Ludwig
Published: March 2013

Electric field induced changes of magnetic properties are of great interest to magnetic data storage and multifunctional micro- and nanoscaled devices. At the electrode/electrolyte interface various processes allow to change the magnetic properties at the electrode surface by an external voltage. The electrode processes at FePt thin films are investigated for different electrolytes. In LiPF6 based electrolytes, irreversible chemical reactions occur due to the presence of HF. When LiClO4 is used instead, the FePt/Fe-O film remains unchanged during immersion. During charging, as for LiPF6, the magnetization of FePt thin films can be changed by exploiting oxidation/reduction mechanisms in a naturally grown metal oxide layer.
Metastable L11 and B
h Ordered Phase Formation in CoPt Alloy Thin Films Epitaxially Grown on Metal Underlayers
Authors: Ohtake Mitsuru , Suzuki Daisuke , Kirino Fumiyoshi , Futamoto Masaaki
Published: March 2013

Co50Pt50 (at. %) alloy epitaxial thin films with the close-packed plane parallel to the substrate surface are prepared on fcc-Pt, fcc-Pd, fcc-Cu, bcc-Cr, hcp-Ti, and hcp-Ru underlayers hetero-epitaxially grown on MgO(111) single-crystal substrates at 300 {degree sign}C by using a radio-frequency magnetron sputtering system. Ordered phase formation is recognized for CoPt films grown on all the underlayers. The ordered phase is determined from a view-point of stacking sequence of close-packed plane. The CoPt films formed on fcc underlayers consist of L11 ordered phase, whereas those grown on bcc and hcp underlayers involve B
h ordered phase in addition to L11 ordered phase. These ordered films show strong perpendicular magnetic anisotropies reflecting the magnetocrystalline anisotropies of L11- and/or B
h-CoPt crystals.
(Invited) Developments in Integrated On-Chip Inductors with Magnetic Yokes
Authors: O'Sullivan Eugene J , Wang Naigang , Herget Philipp , Romankiw Lubomyr T. , Webb Bucknell C. , Fontana Robert E. , Sturcken Noah , Shepard Kenneth L. , Gallagher William J.
Published: March 2013

Thin-film ferromagnetic inductors show great potential as the energy storage element for integrated circuits containing on-chip power management. In order to achieve the high energy storage required for power management, on-chip inductors require relatively thick magnetic yoke materials ({greater than or equal to} a micron). The first part of this paper includes a review of on-chip inductors with magnetic materials from earlier studies. The second part describes the fabrication and characterization of a magnetic inductor on a silicon interposer at IBM. These inductors contained a variety of yoke geometries, included single-turn and multi-turn coils, and were fabricated on 200mm silicon wafers in a CMOS back-end-of-line (BEOL) facility. Each inductor consisted of electroplated copper coils enclosed by electroplated Ni45Fe55 yokes. Aspects of the fabrication of the inductors are described, along with the magnetic properties of the electroplated yoke material and inductor performance.
A Unique Magnetic Alloy for Integrated Power Systems on a Chip
Authors: Panda Amrit , Liakopoulos Trifon , Wilkowski Matthew , Lotfi Ashraf
Published: March 2013

A Fe-Co based amorphous magnetic alloy, called FCA is electroplated onto silicon substrates. The electrodeposition is carried out in customized electroplating equipment specifically developed for the FCA chemistry. A micro-inductor utilizing a magnetic core made of FCA is developed and integrated into a dc-dc converter. This work demonstrates the first commercially viable and available product utilizing electroplated magnetic materials on a wafer level in the power management industry.
Nanoporous Alumina Growth in a Magnetic Field
Authors: Ispas Adriana , Vrublevsky Igor , Schmidt Udo , Bund Andreas
Published: March 2013

One step anodization and re-anodization of aluminum in an external magnetic field was studied in different electrolytes. We could show that the intensity of the magnetic field affects both the properties of the alumina obtained and the anodization process itself. The most pronounced effect of a magnetic field was noticed in sulfuric acid solution, in the case of one step anodization. The samples that have been thermally treated after the first anodization step showed also a stronger effect in the presence of a magnetic field during the re-anodizing process than the samples that were not annealed.
Integration of Electroplated CoFe in Trench Type Flux Guides for Magnetic MEMS Applications
Authors: Chen Jue , Cvetković Srecko , Rissing Lutz
Published: March 2013

For a magnetic MEMS application, the integration of soft magnetic flux guides with high saturation flux density is often needed. A complex form including a trench in substrate was designed to achieve its flux guide function. Electroplating CoFe with followed Chemical-mechanical Polishing (CMP) process was chosen as fabrication technology. Pulse current was selected as power supply for electrodeposition process. Experimental results show, that fine tuned pulse current parameters are necessary for electroplating high magnetic performance, low residual stress CoFe films into a trench form without any formation of cracks and voids. For the further system integration a planarization step is required. Since the CoFe layers show a strong response to the chemical attack causing etching, the mere mechanical polishing process is adequate for the planarization of CoFe. Furthermore, the application of alumina abrasives shows very good results regarding surface quality.
Microfabrication of High-Performance Thick Co80Pt20 Permanent Magnets for Microsystems Applications
Authors: Oniku Ololade David , Arnold David P.
Published: March 2013

The fabrication, via aqueous electrodeposition, of 8 - 30 µm-thick photolithographically-patterned Co80Pt20 films for microsystems applications is reported in this paper. The dependence of their magnetic properties on film thickness has also been studied. Results show that a deposition rate of ~12 µm per hour is achievable via a bath pre-conditioning step without significantly sacrificing the magnetic properties of the film. Maximum out-of-plane intrinsic coercivity (Hci) of 330 kA/m and squareness (Mr/Ms) of 0.9 were obtained for films 15 - 18 µm thick, corresponding to an estimated energy density (BHmax) of 130 kJ/m3. A 23% decrease in coercivity is observed with increase in thickness to 30 µm.
Fabrication and Characterization of an Improved Micro Inductosyn
Authors: Miletić Dragan , Flügge Jens , Gatzen Hans H.
Published: March 2013

The standard linear Inductosyn® system consists of two measurement elements, a scale and a slider. The stationary scale contains a single meander winding, while the moving slider has two meander windings for sensing. Unlike the standard Inductosyn®, a second generation micro Inductosyn® system has four sensing windings, which enables to correct a wedge shaped air gap between scale and slide due to a misalignment occurring during the final assembly process. As its first generation micro Inductosyn® predecessor, it features magnetic flux guides not found in the standard Inductosyn® system to improve coupling. The micro displacement sensor was fabricated using Micro Electro-mechanical System (MEMS) technology. The sensor components, such as meander windings and flux guides, were fabricated by electrodeposition. Moreover, PECVD was used to create an insulating layer between these components. In order to evaluate the system, a mechanical test fixture and an electronic measurement system were created.
Embossing of Soft-Magnetic Structures and Influence on Magnetic Properties
Authors: Kaiser Matthias , Wurz Marc C. , Cvetković Srecko , Rissing Lutz
Published: March 2013

Magnetic flux guides are often a part of MEMS. These flux guides are usually made by electroplating of soft magnetic materials like NiFe. The geometry of the flux guides influences the magnetic anisotropy. A new method for the fabrication of the flux guides is the embossing of the surface to influence the magnetic anisotropy. For this purpose the Institute for micro production technology (IMPT) at the Leibniz Universitaet Hannover designed and fabricated two tools for a molding press. The embossing tool for a molding press (silicon carbide) and a bond tool are applied. This contribution describes the fabrication of the embossing tools for the molding press and the embossing process of NiFe45/55 surfaces applying the fabricated tools and the wire bond tool. The embossed surfaces are characterized via a Kerr microscope.
CPP-GMR of Co/Cu Multilayered Nanowires Electrodeposited into Anodized Aluminum Oxide Nanochannels with Large Aspect Ratio
Authors: Ohgai Takeshi , Goya Naoki , Zenimoto Yu , Takao Keizo , Nakai Masumi , Hasuo Shunji
Published: March 2013

Co/Cu multilayered nanowires with alternating Co and Cu layers of 10 nm in thickness were electrodeposited into extremely long nanochannels of anodized aluminium oxide thick films with 60 μm in thickness. Growth rate of Co/Co multilayered nanowires was around 30 nm/sec and the cylindrical shape was precisely transferred from the nanochannels to the nanowires and the aspect ratio reached up to ca. 1,000 to 1. Co/Cu multilayered nanowires with diameter 60 nm were easily magnetized to the long axis direction of nanowires due to the uni-axial shape anisotropy. 10.5 % of perpendicular giant magnetoresistance effect was observed in Co/Cu multilayered nanowires with 3,000 Co/Cu bilayers.
Anisotropic Magnetoresistance of Ni-Co-Fe Alloy Nanowires Electrodeposited into Anodized Aluminium Oxide Membrane Thin Films
Authors: Ohgai Takeshi , Ikeda Yuki , Egawa Takumi , Takao Keizo , Nakai Masumi , Hasuo Shunji
Published: March 2013

To synthesize a novel anisotropic magnetoresistance (AMR) sensor, Ni-Co, Ni-Fe, Co-Ni and Co-Fe alloy nanowires were electrodeposited into nano-channels of anodized aluminium oxide films with the thickness ranging from 20 μm to 200 μm. The growth rate of the nanowires was around 200 nm/sec at the cathode potential of -1.2 V vs. Ag/AgCl. The aspect ratio of the nanowires reached up to ca. 3,000 to 1 and the cylindrical shape was precisely transferred from the nano-channels to the nanowires. Magnetic hysteresis loops of Ni-Co, Ni-Fe, Co-Ni and Co-Fe alloy nanowires with the diameter of 60 nm showed typical perpendicular magnetization behaviour due to the uni-axial shape anisotropy and the coercive force reached up to 1 kOe. 3.2% of AMR was observed in Co-1.5%Ni alloy nanowires with the aspect ratio of 1,000.
Electrochemical Near-Net-Shape Production Via the FFC Cambridge Process --- Dedication to the Special Session for the 2012 Max Bredig Award
Authors: Hu Di , Chen George Zheng
Published: March 2013

The energy- and labour-intensive extraction processes, and the complex and expensive downstream processes for alloying and manufacturing are the main causes for the high cost of engineering components. These are particularly true for reactive metals based alloys, such as titanium alloys. This paper demonstrates the feasibility of using the FFC Cambridge Process for near-net-shape production of Ti-6Al-4V based engineering components in different shapes, including hollow sphere and miniature hollow golf driver head, from their corresponding metal oxide precursors. A series of investigations were carried out in order to attain a fundamental understanding of the relevant electrochemical reduction mechanism in molten CaCl2. Additive oxide was found to assist the electro-reduction of TiO2 by preventing in situ formation of perovskites during electrolysis in molten CaCl2.
Electrochemical Investigation of Quinone Complexation by Lewis Acids in a Chloroaluminate Ionic Liquid
Authors: Cheek Graham Terry
Published: March 2013

The electrochemical behavior of 9,10-anthraquinone (AQ) has been investigated in the initially neutral aluminum chloride : 1-ethyl-3-methylimidazolium chloride ionic liquid. It has been found that AQ is characterized by a single irreversible redox process in the neutral melt. Additions of AlCl3 cause a positive potential shift, first by the formation of two reversible redox processes corresponding to AlCl3 complexes of AQ under mildly acidic conditions, and then by the appearance of a shifted irreversible redox process in an acidic melt. HfCl4 additions cause similar behavior, except that the reversible systems persist at higher Lewis acid levels than for AlCl3. At the 11:1 Lewis acid: AQ point, AQ is still soluble as an orange solution for AlCl3 additions, but a yellow solid precipitates from a yellow (amber) solution for HfCl4 additions.
Effects of the Charge Density of the Anions of Ionic Liquids on the Electrode Kinetics of Ruthenium 2,2'-Bipyridine Complexes
Authors: Katayama Yasushi , Toshimitsu Yuichi , Miura Takashi
Published: March 2013

The electrode reaction of ruthenium 2,2'-bipyridine complexes has been investigated in 1-ethyl-3-methylimidazolium tetrafluoro-borate (EMIBF4) ionic liquid. The diffusion of the ruthenium complexes in EMIBF4 was slower than that in EMITFSA (TFSA- = bis(trifluoromethylsulfonyl)amide), of which the viscosity is close to that of EMIBF4. The rate constant of the ruthenium redox couple in EMIBF4 was also smaller than that in EMITFSA. It was suggested that the difference in these kinetic parameters in EMIBF4 and EMITFSA is ascribed to the coulombic interaction between the positively charged species and the anions of ionic liquids.
Voltammetric Studies of Proton Reduction in 1-Butyl-1-Methylpyrrolidinium Trifluoromethanesulfonate
Authors: Cheek Graham Terry , Roeper Donald F , O'Grady William E.
Published: March 2013

The reduction of trifluoromethanesulfonic acid (triflic acid) in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethane- sulfonate ( BMPY TfO ) has been investigated at platinum. In the concentration range 7 mM to 55 mM, triflic acid undergoes a broad reduction process at -0.25V vs Ag/AgCl at 100 mV/s, followed by a narrower oxidation process at +0.40V. Addition of water results in shifts of these potentials to more central values, with closer peak spacing ( 340 mV ) at the 4.00 : 1.00 mole ratio H2O : triflic acid point. These results suggest that the proton is associated via a three-center bond with two triflate anions in the BMPY TfO / triflic acid solution. Addition of water leads to complexation of the proton by water molecules, with a resulting potential shift for the redox processes.
Robust Microelectrodes In Molten Salt Analysis
Authors: Relf Andrew , Corrigan Damion , Brady Charlotte L , Terry Jonathan G , Walton Anthony J , Mount Andrew R
Published: March 2013

Molten salts have proven to be an ideal medium for the development of a number of electrochemical processes. However, there is a real need in such processes for techniques to be developed which are able to sense and analyse the properties of redox active species in the extreme conditions found in molten salts. This paper reports the work undertaken to develop a system for the characterisation of microelectrodes in molten LiCl-KCl eutectic and demonstrates for the first time using the Ag+/Ag plating/stripping system the production and characterisation of microelectrodes through photolithography which are able to measure redox characteristics with the expected enhanced characteristics compared to macroelectrode measurements.
PTFE Bound Activated Carbon - A Quasi Reference Electrode for Ionic Liquids and Its Application
Authors: Weingarth Daniel , Foelske-Schmitz Annette , Wokaun Alexander , Kötz Rüdiger
Published: March 2013

The search for widely applicable and stable reference electrodes in non-aqueous electrochemistry, especially in Ionic Liquids (IL), is one of the important topics in basic electrochemical research. PTFE bound activated carbon (AC) quasi-reference electrode for application with IL will be presented. The AC quasi-reference electrode shows long term stability in various IL and is unaffected by small impurities or charging currents. The quasi reference electrode (QRE) is used to study the anodic potential limits of three different Imidazolium based IL having cyano groups in the anion. The anodic electrochemical stability follows a clear trend in the order: [C(CN)3] < [N(CN)2] < [B(CN)4] which appears to be in agreement with valence band measurements performed using X-ray photoelectron spectroscopy.
Fundamental Study on Reduction Rate for Electrolytic Reduction of SiO2 Powder in Molten CaCl2
Authors: Toba Tetsuya , Yasuda Kouji , Nohira Toshiyuki , Hagiwara Rika , Ichitsubo Koki , Masuda Kenta , Homma Takayuki
Published: March 2013

Direct electrolytic reduction of powdery SiO2 has been investigated in molten CaCl2 at 1123 K aiming at a low cost and mass production of solar-grade Si. SiO2 powder was set on a Si plate which was installed at the bottom of the crucible and connected to a graphite rod used as a current lead. SiO2 powder was reduced to Si by cathodic polarization of the Si plate. The reduction rate was evaluated by the magnitude of the reduction current, in which three parameters were varied: electrode potential, SiO2 layer thickness, and SiO2 particle size. As a result, the rate-determining step of the reduction is suggested to be the diffusion of O2- ions inside the reduced porous Si particles filled with the electrolyte. During the reduction process, however, other factors such as contact resistance between Si particles and porosity of SiO2 particles possibly influence the reduction rate.
Anodic Reactions on Some Materials in LiCl-KCl Melt
Authors: Takenaka Toshihide , Umehara Masaki , Araki Daichi , Morishige Taiki
Published: March 2013

The anodic reactions on some materials in LiCl-KCl eutectic melt have been investigated. Palladium and Mo were dissolved seriously though Mo showed passivation behavior. In the melt including Li2O, O2 gas generation occurred at both metal anodes along with their anodic dissolution. At carbon anode, some anodic reactions besides the Cl2 gas generation reaction were observed in the melt with Li2O. The visual observation and the weight change of the anode indicated that the anodic reaction without gas generation and the electrode consumption preceded the CO2 gas generation. The potential of the CO2 gas generation reaction on carbon looked more positive than that of the O2 gas generation on Pd and Mo, which suggested the overpotential of the CO2 generation reaction on carbon was rather large in the melt.
Electrode Kinetics of Oxygen/Superoxide Ion Redox Couple in Some Amide-Type Ionic Liquids
Authors: Nakagawa Takashi , Katayama Yasushi , Miura Takashi
Published: March 2013

The electrode reaction of oxygen and superoxide ion couple was investigated in some amide-type ionic liquids. The solubility of oxygen in the ionic liquids were determined by chronoamperometric technique with both macro- and ultramicro-disk electrode. The temperature dependence on the solubility was small in these ionic liquids. The diffusion of oxygen was found to be independent of the viscosity of ionic liquids. The rate constant of oxygen / superoxide ion couple was also independent of the physical properties of ionic liquids probably because the electrode reaction of oxygen / superoxide ion couple involves adsorption and desorption on the electrode surface.
Reaction Entropies of Some Redox Couples in Ionic Liquids
Authors: Yamato Yoshinori , Katayama Yasushi , Miura Takashi
Published: March 2013

The temperature dependence of the potential, dE/dT, of some redox couples was investigated in different amide-type ionic liquids. The half-wave potentials of the redox couples were determined by DPV (differential pulse voltammetry). The half-wave potentials varied linearly with the temperature from 298 to 328 K in the ionic liquids. The reaction entropies (∆rcS) of the redox couples were calculated from the dE/dT values. ∆rcS of the redox couples with positive charges were affected mainly by the anions of ionic liquids. In contrast, ∆rcS of the redox couples with negative charges depended on the cations of ionic liquids. These results suggest the coulombic interaction between the redox couples and the ions with the opposite sign of charge to those of the redox couples is a dominant factor determining ∆rcS.
Electrochemical Behavior of Bis(trifluoromethylsulfonyl)imide-based ILs at Gold Single Crystal Electrodes
Authors: Ueda Hiroyuki , Nishiyama Katsuhiko , Yoshimoto Soichiro
Published: March 2013

Electrochemical behaviors of the bis(trifluoromethylsulfonyl)imide ([TFSI]−)-based ionic liquids consisting of 1-butyl-3-methylpyrrolidinium ([Py1,4]+), methyltributylammonium ([N1,4,4,4]+), and methyltrioctylammonium ([N1,8,8,8]+) cations were investigated by using low-index Au single crystal electrodes by cyclic voltammetry. The voltammetric feature was dependent on both the structure of the cation and the crystallographic orientation of Au. The electrochemical potential window of the [TFSI]−-based ILs was found to be only dependent upon the chemical structure of the cation. For each Au crystal plane, the electrochemical potential window of each IL was roughly estimated to be approximately 5.5 V, 5.6 V, and 5.8 V for [Py1,4][TFSI], [N1,4,4,4][TFSI] and [N1,8,8,8][TFSI], respectively.
Electrode Reactions of Platinum Bromide Complexes in an Amide-Type Ionic Liquid
Authors: Endo Tomoyuki , Katayama Yasushi , Miura Takashi
Published: March 2013

The electrode reactions of platinum bromide complexes were investigated in an amide-type room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA). Platinum halides were dissolved in BMPTFSA with addition of halide salts of BMP+. Ultraviolet and visible absorption spectra of electrolytes revealed that the coordination environment of Pt(II) and Pt(IV) were [PtBr4]2- and [PtBr6]2- , respectively. The cyclic voltammogram in BMPTFSA containing 10 mM [PtBr6]2- showed two reduction peaks at -1.2 V and -2.6 V. The diffusion coefficients of the [PtBr4]2- and [PtBr6]2- were calculated to be 1.5 × 10-7 and 0.49 × 10-7 cm2 s-1 in BMPTFSA, respectively, by chronoamperometry. Electrodeposition of Platinum in BMPTFSA containing 10 mM [PtBr4]2- was attempted by potentiostatic cathodic reduction at -2.6 V. Nano-particles (2-3 nm in diameter) in the electrolyte after potentiostatic cathodic reduction were observed by transmission electron microscopy. The nano-particles were found to be metallic Platinum by electron diffraction.
Recent Developments in Low-Temperature Electrolysis of Aluminum
Authors: Redkin Alexander , Apisarov Alexey , Dedyukhin Alexander , Kovrov Vadim , Zaikov Yurii , Tkacheva Olga , Hryn John
Published: March 2013

Recent developments in the field of low-temperature electrolytes and electrolysis are considered. Although the investigations have not found fundamental problems in low-temperature aluminum electrolysis development as an industrial process, challenges remain in cell design, construction, and operation of cells with these emerging technologies.
Electrodeposition of Lead from Chloride Melts
Authors: Haarberg Geir Martin , Owe Lars-Erik , Qin Bo , Wang Jingqing , Tunold Reidar
Published: March 2013

Pure lead can be produced by electrowinning or electrorefining in molten salts. Another potential application of lead deposition is related to the recycling of waste. Steady state cathodic current versus potential relations were found to be linear in pure molten lead chloride at 550 - 585 oC. On a tungsten microelectrode the linear behaviour was measured over a wide range; up to 700 A cm-2 and 3 V. The rate of the Pb deposition reaction is believed to be controlled by the transport of Pb containing species by migration in the electrolyte. In dilute solutions of lead chloride in molten KCl-LiCl at 400 oC, the cathodic deposition of lead was found to be diffusion controlled with the influence of nucleation on substrates of glassy carbon, tungsten and molybdenum.
Ta and Nb Electrodeposition from Ionic Liquids
Authors: Krischok Stefan , Ispas Adriana , Zühlsdorff Andre , Ulbrich Angela , Bund Andreas , Endres Frank
Published: March 2013

We have investigated the electrodeposition of tantalum and niobium from the two ionic liquids (ILs) 1 butyl 1 methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide and 1-methyl-3-propyl imidazolium bis(trifluoromethylsulfonyl) amide. The characterization of the deposited metal films is accompanied by an analysis of the chemical composition of the neat ILs as well as the ILs with dissolved TaF5 and NbF5 using X-ray photoelectron spectroscopy. Furthermore cyclic voltammograms provide further information on the reduction mechanism.
Al-W Alloy Deposition from Lewis Acidic Room-Temperature Chloroaluminate Ionic Liquid
Authors: Tsuda Tetsuya , Ikeda Yuichi , Arimura Takashi , Imanishi Akihito , Kuwabata Susumu , Hussey Charles L. , Stafford Gery
Published: March 2013

The electrochemistry of binuclear tungsten salt, K3[W2Cl9], was examined in the Lewis acidic 66.7-33.3 mole percent (m/o) aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-[EtMeIm]Cl) room-temperature ionic liquid as it pertains to the electrodeposition of the Al-W alloy. We revealed that Al-W alloy without chloride contamination can be electrodeposited from the 66.7 m/o AlCl3−[EtMeIm]Cl with the K3[W2Cl9]. Interestingly Al-W alloy having an amorphous phase as well as W-rich Al alloy over 96 atomic present (a/o) W were successfully produced. However the Al-W alloy became covered with powdery deposits with increasing the W content in the alloy. The resulting Al-W alloy showed a favorable chloride-induced pitting potential comparable to that produced by a usual sputtering method if the W content was less than ca. 3 a/o W.
Electrochemical Deposition of Cobalt onto the Surface of Copper Using a Choline Chloride-Based Ionic Liquid
Authors: Damiano Brad T. , Shenenberger Alex , Wixtrom Alex Ian , Abdel-Fattah Tarek M
Published: March 2013

This study involved the deposition of black cobalt onto the surface of a copper substrate using a choline chloride-based ionic liquid. The solution used for electro-deposition contained a 2:1 molar ratio of ethylene glycol and choline chloride, containing CoCl2. Depositions were performed for 30 minutes, with the solution kept at a constant temperature of 70⁰C. The black Co coating on the surface of the Cu substrate was confirmed using scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). This ionic liquid-based electrochemical deposition process could be used as an inexpensive method for solar power generation.
(Keynote) Protic Ionic Liquids Based on a Super-Strong Acid: Bulk and Electrochemical Properties
Authors: Miran Muhammed Shah , Yasuda Tomohiro , Susan Md. Abu Bin Hasan , Dokko Kaoru , Watanabe Masayoshi
Published: March 2013

Protic ionic liquids were synthesized by simple neutralization reactions of a super-strong acid, bis(trifluoromethanesulfonyl) amide acid (H[NTf2]), with a range of amines, resulting in a wide variation in the ΔpKa of the constituent acid and bases. Bulk physicochemical and electrochemical properties of the PILs were studied with an emphasis on thermal stability and temperature dependencies of density, viscosity and conductivity, and electrochemical activity. Thermogravimetric analysis revealed that thermal stability strongly depends on the ΔpKa of the constituent acid and the base. However, density, viscosity and conductivity at different temperatures by and large depend on the structure of amines rather than the ΔpKa. Walden plots indicate that all of these salts are good PILs. Cyclic voltammetry analyses inferred that the PIL with the highest ΔpKa value exhibited a very low electrochemical activity as apparent from the open circuit voltage of 0.60 V vs. RHE at 150 oC for oxygen reduction reaction.
(Keynote) Boronium Based Ionic Liquids: Salts of Boron Centered Cations as Promising Salts for Electrochemical Applications
Authors: Davis James H. , Ruether Thomas , Dorman Scott C.
Published: March 2013

Boronium ions are one of the most promising, yet most under-studied, types of cations of potential utility in ionic liquids and their electrochemical applications. While most mono-boron compounds are highly sensitive to air and water, boronium ions tend to be robust to both, as well as being comparable in thermal stability to more classical organic electrolyte ions such as quaternary ammoniums and imidazoliums. Using boronium ions, we have recently created new IL electrolytes that are competitive (in terms of the width of their electrochemical window) with widely-used ILs such as N,N-dialkylpyrrolidiniums; Further, high-level ab initio calculations have now shed light into the origin of their stability, and provide insights into how modifications to their basic structures could lead to ions with every better performance.
Physicochemical and Electrochemical Properties of Novel Ionic Liquids Containing Aprotic Heterocyclic Anions Doped with Lithium Salts
Authors: Shi Chaojun , Quiroz-Guzman Mauricio , DeSilva Aruni , Brennecke Joan F.
Published: March 2013

A series of novel ionic liquids (ILs) based on N, N'- dialkylimidazolium, tetra-alkylphosphonium and dialkylpyrrolidinium cations paired with two aprotic heterocyclic anions (AHAs) were synthesized in the present study. In addition, lithium salts of the corresponding anions were prepared. Physicochemical and electrochemical properties of the neat ILs and their mixtures with the lithium salts at various concentrations were systematically measured from 283.15K to 343.15K at atmospheric pressure, including density (ρ), viscosity (η) and electrical conductivity (σ). The empirical Vogel-Fulcher-Tammann (VFT) was used to analyze the experimental viscosities and electrochemical conductivities. Furthermore, the Walden plot behavior of the pure ILs and ILs doped with lithium salts were investigated. The results provide some insight into the strength of the association between Li+ and the different anions. Consequently, the ILs with low viscosity and good conductivities are promising electrolytes candidates to be used in electrochemical applications.
Electronic Absorption Spectra of Niobium Species in Halide Melts
Authors: Brevnova Natal'ya P. , Polovov Ilya B. , Chernyshov Mikhail V. , Volkovich Vladimir A. , Vasin Boris D. , Griffiths Trevor R.
Published: March 2013

The results of spectroscopic studies of Nb anodic dissolution, dissolution of NbCl5 and reaction of various niobium oxides with HCl in different chloride melts at 450-7500C are presented. Nb(III) species, NbCl63-, is the major product of niobium anodic dissolution at current densities up to 40 mA/cm2. Addition of NbCl5 to alkali chloride melts predominantly leads to the formation of Nb(V) species, NbCl6-. Upon increasing Nb(V) concentration NbCl6- tend to decompose to Nb(IV) and Cl2. Reaction of NbO and NbO2 with HCl proceeds via an intermediate oxygen-containing Nb(IV) complexes. Oxygen-free Nb(IV) ions, NbCl62-, were obtained by exchange reactions between metallic niobium and melts containing Bi(III), Ag(I) or Ni(II) chloro-ions. Electroreduction of Nb(III) on a tungsten working electrode below -1.45 V vs. Cl2/Cl- led to the formation of metallic niobium, no evidence of intermediate reduction products was obtained.
Hysteresis Effects in the In Situ SFG and Differential Capacitance Measurements on Metal Electrode/Ionic Liquids Interface
Authors: Zhou Wei , Xu Yuanrong , Ouchi Yukio
Published: March 2013

Potential dependent electric double layer (EDL) structure of ionic liquids on a polycrystalline Pt electrode has been studied by in-situ IR-visible sum frequency generation (SFG) spectroscopy and differential capacitance measurements. Within the electrochemical window (EW), potential dependent adsorption/desorption processes of the ions have been monitored. Both SFG and capacitance results indicate that significant hysteresis occurs during the adsorption/desorption processes on the Pt surface, while the EDL structure is highly reversible at the potential close to the limit of the EW. The unique hysteresis effect for ionic liquids on electrode surface should be seriously considered in electrochemical applications of ionic liquids.