bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self‐organized microstructure growth
Authors: Nötzel Richard , Fukui Takashi , Hasegawa Hideki , Temmyo Jiro , Kozen Atsuo , Tamamura Toshiaki 
Published: May 2005

AbstractWe present evidence of the new phenomenon of the direct growth of microstructures by metal‐organic vapor‐phase epitaxy (MOVPE) on high‐index GaAs substrates. One‐ and zero‐dimensional self‐faceting by step bunching on GaAs (n11)A substrates produces quantum‐wire‐ and dot‐like arrays on GaAs(311)A and GaAs (211)A substrates. The lateral periodicity of self‐faceting is controlled by the layer thickness and growth temperature and is directly correlated with the red shift of the luminescence of GaAs/AlGaAs heterostructures. On GaAs (n11)B substrates, well‐ordered quantum‐dot arrays are formed in a new self‐organizing growth mode found in the MOVPE of a sequence of AlGaAs and strained InGaAs films. The InGaAs film spontaneously interacts with AlGaAs buffer layers to form ordered arrays of disk‐shaped InGaAs quantum dots buried within AlGaAs microcrystals due to lateral mass transport. The size and distance of the disks can be controlled independently by the In composition and the InGaAs layer thickness. Similar structures are also formed on InP (311)B substrates in the GaInAs/AlInAs and GaInAs/InP material systems. Lateral confinement of carriers in the disks is confirmed by the photoluminescence linewidth which, at room temperature, is as narrow as 13 meV due to reduced thermal broadening.
New forms of luminescent silicon: Silicon–silica composite mesostructures
Authors: Chomski Emmanuel , Dag Ömer , Kuperman Alex , Coombs Neil , Ozin Geoffrey A. 
Published: May 2005

Can mesoscopic luminescent silicon clusters be synthesized?The study reported here answers this question in the affirmative. The CVD of Si2H6 in a 35 Å channel structure MCM‐41 silica host is described, with the growth of the clusters in the host channels receiving particular attention (see figure). Spectroscopic results and a model for the luminescence are presented.magnified image
Considerations of the production of C60 thin films by PECVD, combustion, or pyrolysis
Authors: Rocabois Phillippe , Hitchman Michael L. , Shamlian Sarkis H. 
Published: May 2005

AbstractA short review of C60 production methods is first presented with an emphasis on thin films for electronic applications. These films are currently made by first producing the fullerene, purifying it and then depositing by different evaporation techniques. Results of an unsuccessful attempt to produce these films by PECVD from organic precursors (cyclopentadiene and naphthalene) are reported. An assessment of the available thermodynamic data of gaseous and solid C60 is then presented. Gibbs free energy minimization for the gaseous system C‐H‐O‐Ar + He including large polyaromatic hydrocarbons and C60 helps to determine under which conditions C60 molecules are stable. Finally, in the light of these calculations, the possibility of the direct production of C60 films by a continuous process such as combustion or pyrolysis is discussed.
Chemical Vapor Deposition Topotaxy in Porous Hosts
Authors: Bowes Carol L. , Malek Andrzej , Ozin Geoffrey A. 
Published: May 2005

AbstractThe application of chemical vapor deposition techniques to the “internal surface” of porous hosts, termed “CVD topotaxy”, is reviewed. Various organometallic species are found to anchor on the internal surfaces of zeolites; species such as methyltrioxorhenium, displaying remarkable optical effects as the result of polymerization processes, and tungsten and molybdenum carbonyls forming redox‐tunable tungsten and molybdenum oxides. Topotaxy has contributed to the quest for spatial confinement of semiconductors through the MOCVD of cadmium, zinc, and tin sulfides in the 13 Å cavities of zeolite Y. This has also been applied to Si and Ge semiconductors, with special applications to the field of luminescent silicon. Finally, Si encapsulation in mesoporous hosts is discussed.
In situ halide chemical vapor deposition of Bi2Sr2CaCu2O8 + x on silver substrates
Authors: Hårsta Anders , Lundquist Stefan 
Published: May 2005

AbstractThe superconducting Bi2Sr2CaCu2O8 + x phase is deposited on polycrystalline silver substrates by halide CVD in the temperature interval 760–820° C. Metal iodides and oxygen are used as precursor materials. The films grow with a pronounced [001] orientation, and a superconducting critical temperature of about 80 K was observed without any post‐annealing. As far as the authors know, this is the first report of in situ CVD of the Bi‐2212 phase on silver substrates. Some of the films were postannealed in a two‐step process. The [001] orientation was now considerably improved, but the superconducting critical temperature was reduced to about 75 K.
Epitaxial growth of Bi2O2.33 by halide Cvd
Authors: Schuisky Mikael , Hårsta Anders 
Published: May 2005

Bismuth oxide is an interesting dielectric material with potential applications for optical coatings. MIS capacitors, and microwave integrated circuits. CVD growth has a number of advantages over other deposition techniques, e.g., precise control of oxygen activity, microstructure, and texture. The study presented here shows how this can be achieved for epitaxial Bi2O2.33 films grown on SrTiO3 and MgO (see Figure) using halide CVD with Bil3 as the bismuth source.magnified image
Atomic Layer Epitaxy of Copper on Tantalum
Authors: Mårtensson Per , Carlsson Jan‐Otto 
Published: May 2005

AbstractThe decreasing size and increasing complexity of the components in future microelectronics devices present a great challenge in the development of new deposition techniques. One method for the deposition of semiconductor materials which has generated considerable interest is atomic layer epitaxy (ALE). This method has been shown to yield films with excellent step coverage and high conformity, even on very complex shaped substrates. In this paper we report, for the first time, the deposition of copper using the ALE technique. The films were deposited on tantalum substrates using copper(I) chloride as the precursor and hydrogen as the reducing agent. The films were found to be polycrystalline and practically free from texture. They were also very low in chlorine contamination and possessed a rather rough surface morphology. An initial fast substrate reduction, yielding a film thickness of approximately 300 À, was observed, the rate determining step being the reaction of hydrogen with the adsorbed copper chloride. The activation energy for this step was estimated to be 80 kJ mol−1.
Silica Overlayers Prepared Using Organic Template Molecules on Tin Oxide and Its Molecular Sieving Property
Authors: Kodakari Nobuaki , Katada Naonobu , Niwa Miki 
Published: May 2005

AbstractIn order to create a molecular recognition property on an oxide surface, a silica overlayer was prepared on tin oxide by the chemical vapor deposition (CVD) of silicon alkoxide using pre‐adsorbed benzoate anions as template molecules, which were then removed. Silica overlayers on tin oxide prepared in this way showed the adsorption property to discriminate between molecules based on their molecular size, i.e., to possess a molecular sieving property. The size of the vacancies in the silica overlayers was controlled by the template molecule.
MOCVD Route to Chromium Carbonitride Thin Films Using Cr(NEt2)4 as Single‐Source Precursor: Growth and Mechanism
Authors: Ossola Franco , Maury Francis 
Published: May 2005

AbstractChromium carbonitride coatings with a low nitrogen content were deposited by low pressure MOCVD in the temperature range 573–793 K using Cr(NEt2)4 as single‐source precursor. As‐deposited films are amorphous and crystallize upon annealing at 873 K to form an orthorhombic ternary phase. They exhibit a high hardness and their resistivity decreases by increasing the growth temperature. This dependence has been correlated to their microstructure. Quantitative 1H NMR analysis of the by‐products of the MOCVD reaction has been performed. The quasi‐equimolecular ratio of the by‐products EtN=CHMe and HNEt2 suggests that most of the NEt2 ligands are removed by a stepwise mechanism, which is discussed.
Volatile Metal β‐Diketonates: ALE and CVD precursors for electroluminescent device thin films
Authors: Tiitta Marja , Niinistou Lauri 
Published: May 2005

AbstractThe use of volatile β‐diketonate chelates as precursors for the deposition of thin films for electroluminescent devices is reviewed. Alternating current thin film electroluminescent (ACTFEL) devices consist of an emitting layer sandwiched between two dielectric layers, together with conducting and buffer layers. Besides various physical deposition techniques, the commonly applied methods for preparing thin films are chemical vapor deposition (CVD) and its particular variant atomic layer epitaxy (ALE). Alkaline earth β‐diketonates are used as precursors for deposition of the semiconducting alkaline earth sulfide and thiogallate films that provide the matrix in emissive layers, while β‐diketonates of lanthanides and a few other metals (Mn, Na, K) are precursors for dopants and codopants producing colors. β‐Diketonate precursors can also be used for the preparation of dielectric alkaline earth titanate and oxide layers. Current research on thin film electroluminescent materials is focused on improving the blue color produced by cerium doping of alkaline earth sulfide and thiogallate matrices. The synthesis and properties of β‐diketonate chelates and the growth and characterization of the thin films obtained with them are presented and discussed. This review of precursors for TFEL materials is also relevant for other materials, including oxide superconductors.
Epitaxial BaTiO3 films grown by aerosol MOCVD
Authors: Gorbenko Oleg Y. U. , Kaul Andrey R. , Wahl Georg 
Published: May 2005

BaTiO3 tin films are promising for electronic and optoelectronic devices. Current growth techniques give rather low deposition rates for practical applications. Here epitaxial growth rates over 100 times higher have been achieved using aerosol CVD with surface diffusion enhancement in the presence of Bio‐containing vapor. The AFM image shows a typical layer with an rms roughness of 12 nm.magnified image
Photochemical Vapor Deposition of Wide Bandgap III‐V Materials: Influence of Photochemically Generated Radicals on the Growth of Aluminum Nitride and Gallium Nitride Films
Authors: Alwan James J. , Eden J. Gary 
Published: May 2005

AbstractAluminum nitride and gallium nitride films have been grown on the 1120, 0001, 1010, and 1102 (A, C, M, and R, respectively) planes of sapphire by laser photochemical vapor deposition and MOCVD at temperatures ranging from 600 to 950°C and a total reactor pressure of 1–5 Torr. For the molecular precursors triethylgallium (TEGa) and ammonia. GaN film growth directly onto sapphire or on AIN buffer layers ranging from ∼50 to 500 Å in thickness has been investigated under conventional MOCVD growth conditions and compared to the growth rates and structure for films produced when 193 and 248 nm (ArF, hω = 6.4eV, and KrF, hω = 5.0eV, respectively) photons are introduced into the reactor. Kinetic modeling of the growth rate dependence on laser pulse energy suggests that the dominant photolytically produced species is the amidogen radical, NH2. The presence of 193 nm photons also promotes the growth of (1120)‐oriented GaN films, which provides an example of the ability of photochemistry in the gas phase to drive surface kinetics.
Plasma‐assisted CVD of cubic boron nitride
Authors: Konyashin Igor , Bill Joachim , Aldinger Fritz 
Published: May 2005

AbstractSingle‐phase cubic boron nitride films of high quality might be of great importance as superhard wear‐resistant coatings and semiconductive materials. This paper reviews deposition techniques, precursors, deposition parameters and substrates employed in plasma‐assisted CHEMICAL VAPOR DEPOSITION (PACVD) of cubic boron nitride (c‐BN) as well as procedures applied for the characterization of c‐BN‐containing films. Mechanisms of the formation of sp3‐hybridized boron nitride during PACVD by use of either high‐energy nitrogen and argon ions or hydrogen plasmas are discussed. All experimental results on PACVD of c‐BN are thought to fit either “physical” or “chemical” routes for c‐BN low‐pressure synthesis, which are based on principles of c‐BN physical vapor deposition or diamond CVD.
Palladium thin films grown by CVD from (1,1,1,5,5,5‐hexafluoro‐2,4‐pentanedionato) palladium(II)
Authors: Bhaskaran Vijay , Hampden‐Smith Mark J. , Kodas Toivo T. 
Published: May 2005

AbstractThe precursor (1,1,1,5,5,5‐hexafluoro‐2,4‐pentanedionato) palladium(II) [Pd(hfac)2] was used to deposit high‐purity, polycrystalline palladium films under low‐pressure CVD conditions at high growth rates (1000–4000 Å/min) over a substrate temperature range of 80–200°C in the presence of H2. Mixing of the precursor and H2 streams near the substrate was required to avoid reactions of the precursor with H2 at locations other than the substrate surface. Auger electron spectroscopy (AES) showed that the films were impurity free when sufficient H2 was used. Resistivity values of 20 μΩ were obtained at the higher deposition temperatures (∼200 °C) while high values of 50 μω were observed at the lower deposition temperatures (∼90 °C). The deposition rate was feed‐rate limited even at the lowest deposition temperatures and highest precursor delivery rates, suggesting that even higher deposition rates could be obtained with higher feed rates. A high precursor conversion of 50–60 % was observed. The high surface reaction probability of Pd(hfac)2 in the presence of H2 was reflected qualitatively by trench fill studies which showed a greater film thickness on the top of sub‐micrometer trenches than in the bottom.
Silica gel modified carbon composite electrodes
Authors: Kopanica Miloslav , Stará Vĕra 
Published: May 2005

AbstractCarbon composite electrodes modified with silica gel exhibit properties analogous to those of an ultramicroelectrode array in voltammetric measurements. The limiting current in linear scan voltammetry is independent of the potential scan rate in certain scan rate regions. The possibility of using high potential scan rates is advantageous analytically, both in direct voltammetric determinations and in analyses involving accumulation of the analyte on the surface of the working electrode.
A thin‐layer electrode cell for fluorescence. Measurements on electrogenerated intermediates
Authors: Compton Richard G. , Fisher Adrian C. , Wellington R. Geoffrey 
Published: May 2005

AbstractA new methodology for the study of luminescence from photoexcited electrogenerated species is presented. A suitable optically transparent thin‐layer electrode compatible with fluorescence spectrometer was developed, and this was used to study luminescence from the radical cation of tris(4‐methylphenyl)amine and the radical anion of 9,10‐anthracenedione electrogenerated in situ.
Comparison of the adsorptive voltammetric behavior of avidin and streptavidin
Authors: Buckley Eileen , Alvarez Jose M. Fernández , Smyth Malcolm R. , O'Kennedy Richard 
Published: May 2005

AbstractThe adsorptive voltammetric behavior of the binding proteins avidin and streptavidin was investigated at a stationary mercury drop electrode. It is demonstrated that, although streptavidin contains no disulfide linkages or sulfur‐containing amino acids, it gives rise to voltammetric behavior similar to avidin, which is a glycoprotein containing two cysteine residues per subunit and one interchain disulfide linkage. The adsorptive accumulation of both proteins was investigated both at open circuit and under electrolytic conditions. It is shown that avidin shows preferential adsorption characteristics under open circuit conditions, and under electrolytic conditions when the potential of the electrode was held at positive potentials. Streptavidin, on the other hand, shows preferential adsorption characteristics when accumulation is carried out at open circuit. This behavior is explained by considering the charged nature of the proteins under the experimental conditions used in this study. It would appear, therefore, that the voltammetric peaks obtained for globular and other proteins not containing prosthetic groups are due in part to processes other than the simple reduction of the disulfide linkage.
Disposable amperometric CO2 sensor employing bacteria and a miniature oxygen electrode
Authors: Suzuki Hiroaki , Tamiya Eiichi , Karube Isao 
Published: May 2005

AbstractWe have developed a disposable bacterial CO2 sensor employing a miniature Clark‐type oxygen electrode and autotrophic bacteria. To make the sensitive area less vulnerable to stress, to facilitate CO2 diffusion through the sensitive area, and to make the application to biosensors easier, the sensor structure was simplified by immobilizing the bacteria in an oxygen electrode cell along with a 0.1 M KCl electrolyte solution. We developed a novel process that allows immobilization of bacteria in a small sensitive area, thereby improving the response time. The response time of this CO2 sensor ranged from 1 to 3 minutes. A linear relationship was obtained for NaHCO3 concentrations between 0.5 and 3.5 mM (at 32°C and pH 5.5). The CO2 sensor can be used up to 10 times before disposal.
Catalytic adsorptive stripping voltammetric determination of cobalt as an α‐benzil dioxime complex in the presence of an extremely large excess of zinc
Authors: Bobrowski Andrzej , Bond Alan M. 
Published: May 2005

AbstractThere is considerable interest in determining trace amounts of cobalt in highly concentrated zinc solutions. Existing commonly used voltammetric methods such as those based on formation of dimethlyglyoxime complexes and adsorptive stripping voltammetry, while very sensitive for the determination of cobalt, do not always provide the necessary discrimination against the zinc (and nickel) processes. In the present work a recently described method, based on the formation and adsorption of a cobalt–α‐benzil dioxime complex and catalyzed by nitrite, has been optimized so at a 106 to 107 M concentration excess of zinc can be tolerated. Since the method is also relatively insensitive to nickel, it can be applied to highly purified zinc electrolytes.
Electrocatalytic oxidation of ascorbic acid at chemically modified electrodes
Authors: Kulys Juozas , Drungiliene Alms 
Published: May 2005

AbstractElectrocatalytic oxidation of ascorbic acid (AA) in aqueous buffer solution at the p‐tetracyanoquinodimethane (TCNQ)‐, ferrocene (Fc)‐, 1,1′‐dimethylferrocene (DMFc)‐, and tetrathiafulvalene (TTF)‐modified graphite electrodes is carried out at each modifier's redox potentials. Over the linear range of current dependence on AA concentration, the sensitivity of the electrocatalytic systems corresponds to up to 0.1 A/M. At pH 6.5–8.0 a change in the electrocatalytic process rate is less evident (for TCNQ, TTF) or is increased by a factor of 4.9 (DMFc). The electrocatalytic current is only slightly dependent on electrode rotation speed. The electrodes retain about 80% of their initial response over a 2‐month period of operation.
Flow injection determination of methionine with amperometric detection at a stable modified electrode
Authors: Cox James A. , Dabek‐Zlotorzynska Ewa 
Published: May 2005

AbstractA glassy carbon electrode that is modified by electrodeposition of a film comprising mixed valence ruthenium oxide stabilized by cyano crosslinlks catalyzes the oxidation of methionine at 0.92 V vs. Ag/AgCl. A linear calibration curve is obtained for flow injection amperometry over the range 0.6–180 μM with a 0.2 M K2SO4 carrier at pH 2, a 7.5 μL sample volume, and a 1.0 mL/min flow rate. The sensitivity is 20 ± 0.3 nA/μM at a 0.07 cm2 electrode. With a single surface preparation, the sensitivity of the method remains constant over more than 3 weeks with daily use. The method also was used with carriers of the composition of common liquid chromatographic eluents such as various citrate–phosphate mixtures and a 0.1 M chloroacetic acid solution at pH 3.0 in 1% acetonitrile.
Polarographic identification and determination of synthetic coloring matter in corks
Authors: Barros Aquiles Araújo , Rodrigues José António M. 
Published: May 2005

AbstractIn the final treatment of corks a certain amount of coloring matter must be added to restore the natural color that is lost during manufacturing. The coloring matter most widely used is Sunset Yellow FCF. Another food coloring matter, Orange II, which is not permitted for use, is often incorporated. Unfortunately both dyes exhibit similar polarographic behavior, making it almost impossible to differentiate between them. This work describes a polarographic procedure that allows one to distinguish between the two coloring materials. An application of the method to the analysis of corks is described, including the quantitation of the coloring matter identified. Detection limits less than 100 ppb. were obtained, corresponding to an amount of coloring matter of about 2 μg per cork.
Modified electrodes for electrochemical sensors
Authors: Wang Joseph 
Published: May 2005

AbstractChemically modified electrodes exhibit unique behavior that can greatly benefit electrochemical sensing. In this article we review the development and applications of modified electrodes for chemical sensing. After a general introduction, different strategies for surface modification, as employed in chemical sensing, are discussed in detail. Special attention is given to permselective coatings, which offer controlled access at the sensor surface or the surface immobilization of biological entities that specifically recognize the analyte. Better, understanding of these modified electrodes is achieved by using high resolution surface characterization techniques. Future prospects are evaluated.
Signal shapes and single‐boundary measurements in flow injection analysis with amperometric detection
Authors: Fogg Arnold G. , Zhao Rui 
Published: May 2005

AbstractThe shapes of normal and reverse flow injection (nFI and rFI) signals have been studied using single‐channel manifolds, amperometric and visible spectrophotometric detection, and small and large (> 1.5 mL) injection volumes. The shapes of nFI and rFI signals are fundamentally different because in rFI the sample, being the carrier stream, is present in essentially infinite volume. For this reason, rFI signals are broader and are prone to double‐peak formation at lower injection volumes than are nFI signals. Contributions to the final signal from dispersion at the front and rear boundaries of the injected bolus frequently are, or appear to be, unequal. With loop injection, the rear boundary travels further than the front boundary and is dispersed more: injection by stream switching removes this factor. With spectrophotometric detection, correction for large and opposite refractive index effects at the two boundaries may be required. In amperometric detection, differences in acidity of carrier stream and injectate can cause significant changes in background current on switching and can distort the signal at low concentrations of monitorand. When these factors are eliminated, however, other factors causing peak height and peak shape differences remain: differences in dispersion rates of reactants, and of reaction rates, appear to be the major factors.