bluuebunny/crossref_metadata_2025_split huggingface dataset:
Redox reactions on modified bilayer lipid membranes for biosensing device
Authors: Krysiński Pawel 
Published: May 2005

AbstractSuitably modified bilayer lipid membranes (BLMs) offer exceptionally good opportunities for probing the electric field effects on charge transfer and redox reactions in biosensor and molecular electronics research and development. This work presents an attempt to form an ultrathin electron‐conducting matrix for a biosensing redox device on the basis of a BLM modified with tetracyano‐p‐quinodimethane (TCNQ), a well‐known compound forming charge transfer complexes of ‘organic metal’ behavior. The rationale behind the choice of membrane modifier was the reports of its unusual rectifying current–voltage characteristics when incorporated into BLMs alone or as part of an σ‐bridged donor–acceptor molecule of C16H33–Q3CNQ (Z‐β‐(1‐hexadecyl‐4‐quinolinium)‐α‐cyano‐4‐styryldicyano methanide) deposited in the form of a Langmuir–Blodgett film.
The photovoltage signals of bacteriorhodopsin in Langmuir–Blodgett films with different molecular orientations
Authors: Ikonen Marjo , Sharonov Alexey , Tkachenko Nikolai , Lemmetyinen Helge 
Published: May 2005

AbstractThe photoresponse of bacteriorhodopsin (bR) has been studied in Langmuir–Blodgett (LB) films bR was deposited by vertical dipping as x‐ or z‐type monolayers and as z‐type multi layers between stearic acid LB films. The electrodes used were a transparent vacuum‐deposited ITO on a quartz substrate and an InGa metal alloy. The signals were observed from samples containing a single bR layer or five bR layers both at room humidity and in water‐saturated conditions. The photoelectric signals of x‐ and z‐type monolayers had opposite polarities and both had two exponential kinetics on a microsecond time scale with time constants of about 10 and 70 μs. The amplitude of the fast negative component of the signal of a bR monolayer was 0.4 mV, in the opposite direction to that in which protons were pumped. The amplitude due to five layers was five times as high as that due to a monolayer. The ratio between the amplitudes of the fast negative component and the slow positive part of the signal, in the proton‐pumping direction, was 1:3. The photoresponse signal saturated with a light intensity of about 1.7 mJ cm−2, which is equivalent to a photon density of 0.5 Å−2. The activation energy of the bR photovoltage was 75 ± 5 kJ mol−1 in the temperature range between 17 and 35°C.
A study of the effect of in situ doping on the crystallinity of LPCVD polysilicon
Authors: Hitchman Michael L. , Jones Cameron W. , Zhao Junfu , Shamlian Sarkis 
Published: May 2005

AbstractResults are presented for the degree of crystallinity, determined by Raman spectroscopy, of in situ B‐doped LPCVD polysilicon as a function of deposition temperature. The results are compared with those reported in the literature for P‐doped polysilicon and it is found that for B doping full crystallinity of the layer is achieved at a significantly lower deposition temperature than is required for P doping. An attempt to understand this effect is made in terms of a quantitative model which allows an estimation of values for silicon self‐diffusivity and which is in accord with the experimental observations.
Modification of the dark and photoconductivity and the optical transmittance of solution‐grown CdS thin films
Authors: Sebastian P. J. , Sanchez A. , Nair P. K. 
Published: May 2005

AbstractVery interesting behaviour is shown by chemically deposited CdS thin films for optoelectronic applications after air and vacuum (10−5 Torr) annealing. Vacuum annealing of samples at about 100°C caused the dark conductivity to improve by five orders of magnitude. The dark and photoconductivity of air‐annealed (at around 200°C) samples increased by seven and two orders of magnitude respectively. Air‐annealed (at 350°C for about 2 min) samples exhibited a very quick photoresponse (<2 s for two decades of photocurrent decay) with σp/σd ≈ 105 for a bias of 10 V, which may be exploited for photodetector applications. Air or vacuum annealing of samples for a minimum of 10–15 min caused the optical transmittance above the band edge to increase by 10%–15% and annealing the sample at 200°C caused the absorption edge to shift towards the longer‐wavelength region compared with the as‐prepared and 100 and 350°C annealed films.
Evidence for solid state electronic conductivity in mixtures of a porphyrin and its two‐electron oxidation product
Authors: Milgrom Lionel R. , Hill Jonathan P. , Bone Stephen 
Published: May 2005

AbstractConductivity measurements demonstrate that in the presence of toluenesulphonic acid, 1:1 mixtures of mesotetrakis(3,5‐di‐t‐butyl‐4‐hydroxyphenyl)porphyrin and its two‐electron oxidation product give materials whose degree of semiconductivity is dependent on the toluenesulphonic acid concentration in the solid.
On the electro‐optic properties of single crystals of sodium, potassium and rubidium acid phthalates
Authors: Miniewicz Andrzej , Bartkiewicz Stanislaw 
Published: May 2005

AbstractThe linear electro‐optic (Pockels) effect in a series of alkali metal acid phthalate crystals has been studied. Single electro‐optic coefficients r and r for sodium (NaAP), potassium (KAP) and rubidium (RbAP) acid phthalates have been measured by employing the modified Mach–Zehnder interferometric technique. The best electro‐optic crystal in this series is RbAP with r = 9.10 × 10−12 m V−1, r = 3.05 × 10−12 m V−1 and a sizable figure of merit for electro‐optic phase retardation, comparable with that of KDP. The dispersion properties of the electro‐optic coefficients for KAP are discussed in detail.
A comparative investigation of the oxidation of silicon using H2/O2, TCA/O2 and HCl/O2 mixtures
Authors: Ahmed W. , Ahmed E. , Armour D. G. 
Published: May 2005

AbstractThe oxidation of single‐crystal silicon wafers has been investigated using an industrial thermal oxidation system. The growth characteristics and electrical properties of the oxides resulting from pure hydrogen/oxygen (H2/O2), trichloroethane/oxygen (TCA/O2) and hydrogen chlorid/oxygen (HCl/O2) mixtures have been investigated and compared. The addition of both HCl and TCA to oxygen produces higher growth rates and improved electrical characteristics. It is shown that the oxidation rate for TCA/O2 is approximately 30%–40% higher than for HCl/O2 and that comparable electrical properties can be readily obtained. A TCA/O2 ratio of 1 mol% gives the optimum process for VLSI applications, though 3 mol% HCl/O2 gives comparable results. It is suggested that the overall mechanisms governing the processes are similar. However, the TCA process is a safer and cleaner alternative because it generates HCl in situ in the oxidation chamber.
Neural network fitting and prediction of polarisability tensors for aromatic hydrocarbons
Authors: Munn R. W. , Munn N. S. 
Published: May 2005

AbstractA standard back‐propagation neural network is used to correct input semi‐empirical molecular orbital calculations of polarisability tensors to fit experimental data for aromatic hydrocarbons. The method readily yields the correct component normal to the molecular plane but is restricted by a small training set. The network is also used to predict polarisability components for structures input as the pattern of rings fused to a central benzene ring. Semi‐quantitative predictions are obtained depending on the size and method of presentation of the training set.
Laser activation and metallisation of oxide ceramics
Authors: Shafeev G. A. 
Published: May 2005

AbstractUV excimer laser irradiation of oxides such as SrTiO3, PbTi1 − xZrxO3 (PZT) and Al2O3 results in the formation of colour centres. These colour centres mediate catalytic activity for electroless plating from Cu and Ni solutions. The adherence of the metal deposits to the as‐sintered ceramic surfaces is excellent.
Structure of 2‐(iminocoumar‐3‐yl)‐4‐(coumar‐3‐yl)‐thiazole, C2lHl4N2O3S
Authors: Baumer V. N. , Ponomaryov O. A. , Novikov A. I. , Lakin E. E. , Kuznetsov V. P. 
Published: May 2005

AbstractWe have determined the structure of 2‐(iminocouma‐3‐yl)‐4‐(coumar‐3‐yl)‐thiazole, C21H14N2O3S, Mr=372.4, λ = 0.71073 Å, monoclinic, space group P21/n, a = 9.472(2) Å, b = 11.284(2) Å, c = 15.821(3) Å, β = 86.50(2)°, V = 1687.9(6) Å3, Z = 4, Dx = 1.465 Mg m−3, μ(Mo Kα) = 0.207 mm−1, F(000) = 768, S = 1.91, R = 3.82%, wR = 3.26% for 1251 observed reflections (F > 6σF). In the observed conformation of the molecule the imino group forms an intramolecular H…S bond of length 2.26 Å and the carbonyl oxygen makes a short contact with the hydrogen atom of the thiazolyl cycle. The molecule is planar. In the crystal structure a particular disorder of about 20% of molecules is observed with respect to the pseudo‐mirror plane which is perpendicular to the molecular plane and passes through the thiazolyl N atom and the middle of the SCH bond. The disagreement found between the observed conformation and that predicted by molecular mechanics calculations is explained by the tendency of the molecule to have the lowest value of dipole moment due to minimisation of the electrostatic contribution to the energy.
Electroluminescence from phenylenevinylene‐based polymer blends
Authors: Vestweber H. , Oberski J. , Greiner A. , Heitz W. , Mahrt R. F. , Bässler H. 
Published: May 2005

AbstractThe electroluminescent behaviour of films of poly(phenylphenylenevinylene) (PPPV), of PPPV blended with polystyrene (PS) and of PS doped with oligo(phenylenevinylene) sandwiched between indium–tin oxide (ITO) and Al contacts has been investigated. Polymer blending increases the relative quantum efficiency by up to two orders of magnitude. Studying the cell performance under application of rectangular voltage pulses as a function of temperature indicates that (i) hole injection at the ITO contact occurs by tunnelling, (ii) tunnel injection of electrons at the cathode is promoted by a space charge field across an interfacial Al2O3 layers and (iii) leakage of holes through the cathodic barrier is the main loss mechanism for holes.
The kinetics of charges in dry bacteriorhodopsin Langmuir–Blodgett films—an analysis and comparison of electrical and optical signals
Authors: Ikonen Marjo , Sharonov Alexey Yu. , Tkachenko Nikolai V. , Lemmetyinen Helge 
Published: May 2005

AbstractThe decay of the M intermediate and the recovery kinetics of bacteriorhodopsin (bR) were detected optically in dry and wet bR Langmuir–Blodgett (LB) films and electrically in dry films. From the electrical signals the kinetics of the proton motion was distinguished from the cell function and it was found to be equal to that determined optically for the M intermediate decay. The rate‐determining step for the recovery rate of bR was found to be the M state.
Visible fluorescence on IR excitation of polar dimethylaminobenzylidene 1,3‐indandione crystals
Authors: Valkunas L. , Juodzbalis D. , Urbas A. , Gruodis A. , Durandin A. D. , Silinsh E. A. , Klimkans A. , Larsson S. 
Published: May 2005

AbstractA novel non‐linear fluorescence (NLF) effect in polar dimethylaminobenzylidene 1,3‐indandione (DMABI) crystals is presented and discussed. A single crystal or vacuum‐evaporated layer of DMABI excited in the IR region at 1064 nm (by a Q‐switched YAG laser) emits red light in the visible region of the spectrum at 600–740 nm depending on the DMABI crystalline modification. This anti‐Stokes luminescence shows a quadratic dependence on the exciting light intensity which transforms to a linear dependence at very high excitation intensities. The observed NLF effect under IR excitation is determined by optical transitions into intermolecular charge transfer (CT) states. It has been suggested that the photoexcited singlet 1CT excitations may either interact in a quadratic singlet–singlet (1CT + 1CT) annihilation reaction or, more probably, form long‐lived triplet 3CT excitons via a hyperfine interaction effect which may subsequently annihilate in a similar bimolecular fusion reaction (3CT + 3CT). In both cases the excited molecular singlet state S1 is formed and thus the NLF effect is due to singlet–singlet or triplet–triplet fusion of CT excitons. A detailed energy diagram and kinetic description of the model are presented. Quantum chemical calculations of the electronic structure of the DMABI molecule illustrate the dipolar nature of its ground and excited states.
A photolithographic technique for patterning spin‐coated polyaniline films
Authors: Di Bartolomeo C. , Barker P. , Petty M. C. , Adams P. , Monkman A. P. 
Published: May 2005

AbstractSolvent‐cast polyaniline films have been deposited by spin coating and photolithographic techniques used to pattern the films to a resolution of 15–20 μm. This approach is then used successfully to deposit the polymer on the gate areas of an array of silicon field effect transistors.
Polyalkylthiophene thin films and their characterisation with transmission spectroscopy
Authors: Heinämäki A. 
Published: May 2005

AbstractPolyalkylthiophene thin films have been prepared to enable the characterisation of the films with transmission spectroscopy and profilometry for the first time. The optical properties of the films as a function of annealing temperature are discussed. The changes in absorption with time are related to thermochromism.
Relationship between microscopic and macroscopic structures of organic thin films for SHG
Authors: Voigt‐Martin I. G. , Zhou E. , Simon P. , Garbella R. W. , Yan D. , Paulus W. , Ringsdorf H. 
Published: May 2005

AbstractThe experiments described in this paper were undertaken in order to obtain information about the relationship between the structure and non‐linear optical properties (second‐harmonic generation) of organic thin films. For this purpose, two closely related dyes, diones and tetrones, were compared, both of which are shown to have large hyperpolarisabilities. Their microscopic properties are investigated by conformational analysis and electron diffraction. It could be shown that detailed knowledge about the structure and the adjacent neighbour packing can be obtained from conformational analysis and electron diffraction in order to understand the non‐linear optical properties of the two dyes.
Group 2 element and related compounds as chemical vapour deposition precursors for high‐temperature superconducting metal oxides
Authors: Barron Andrew R. , Rees William S. 
Published: May 2005

AbstractThe advent of high‐temperature superconducting metal oxides (SMOs) has prompted an increasing number of studies aimed at the development of new routes to their syntheses, in particular in the form of thin films. The preferred method in this regard has been that of chemical vapour deposition (CVD); however, significant difficulties have been associated with the efficacy of commercial precursors for the group 2 metals, in particular those of the bis(β‐diketonates) of barium, whose co‐ordinative unsaturation leads to cluster formation. The development of alternative β‐diketonate precursor systems has focused upon the synthesis of stable Lewis acid‐base complexes by either inter‐ or intramolecular stabilisation. The results of these studies are described herein, along with a review of the research to date on non‐β‐diketonate derivatives of the group 2 metals, including organometallic, halide, amide, carboxylate and alkoxide compounds. On the basis of the results to date, a series of goals for the synthesis of the ideal precursor are discussed.
The influence of chlorine on the optical properties of monoclinic lead phthalocyanine thin films
Authors: Krier A. , Abass A. K. , Collins R. A. 
Published: May 2005

AbstractThe optical transmittance and absorption of thin films of monoclinic lead phthalocyanine have been studied as a function of exposure to chlorine and air. The effect of chlorine on the refractive index and dielectric constant of freshly prepared films was estimated from reflectivity data in the photon energy range 2.1–2.6 eV. Responsivity and recovery from gaseous exposure were studied with regard to the applicability of lead phthalocyanine to the fabrication of an optical chlorine sensor.
Formation of silicon nitride films by remote plasma‐enhanced chemical vapour deposition
Authors: Alexandrov Sergei E. , Hitchman Michael L. , Shamlian Sarkis 
Published: May 2005

AbstractIn this paper we describe the growth of silicon nitride from nitrogen and silane for the first time by capacitively coupled remote PECVD. We report on the effect of process parameters on the composition and properties of the deposited films and we show that by adjustment of these parameters it is possible to produce high‐quality material which could be of interest for electronic applications. Of particular note is that the growth rate is about one order of magnitude higher than any previously reported for nitride growth with remote PECVD using molecular nitrogen as the nitrogen source. We also discuss the mechanism of growth and propose that electron excitation of nitrogen and silane occurs in the gas phase, producing SiHx species which are adsorbed on the growing surface. The nitrogen is then incorporated into the layer by heterogeneous reaction.
In‐Situ mechanistic studies of the reaction of trimethylgallium and phosphine in zeolite H‐Y
Authors: Anderson M. W. , Logothetis G. K. , Pemble M. E. , Taylor A. G. , Wallace N. C. , Yates H. M. 
Published: May 2005

AbstractCoherent anti‐Stokes Raman scattering (CARS) has been utilised to monitor the decomposition of trimethylgallium (TMGa) on the reactive internal surface of the protonated form of zeolite Y under metal organic chemical vapour deposition (MOCVD) conditions designed to produce GaP deposits that exhibit quantum‐size effects. The CARS data clearly reveal the facile room temperature decomposition of TMGa in the zeolite, as evidenced by the detection of increasing levels of methane with increasing reaction time. In addition, the zeolite samples were analysed by solid state nuclear magnetic resonance with magic angle spinning (MAS NMR) before reaction, after reaction of TMGa and after subsequent reaction with phosphine at 300°C. These data reveal that TMGa reacts with acid sites in the zeolite 12‐rings, resulting in species containing methyl groups. Subsequent exposure to phosphine removes these methyl group protons, leaving various, as yet not fully characterised, phosphorus species. Exposure to phosphine does not appear to regenerate the acid sites on the zeolite.
Controlling the interface between II–VI and III–V semiconductors
Authors: Zahn Dietrich R. T. 
Published: May 2005

AbstractThis paper describes ways in which the interface between II–VI and III–V semiconductors can be controlled so as to suppress or alter commonly observed interfacial reactions. This will be done using CdTe/InSb and CdS/InP heterostructures as examples. In the case of CdTe/InSb a modification of the interfacial properties is achieved by a variation in the II/VI ratio offered to the surface during growth, while the influence of Sb interlayers is studied for CdS on InP. Information on the interface properties is obtained from Raman spectroscopy. While structural and electronic properties of the II–VI layer can be deduced from the scattering intensities of its characteristic vibrational modes, the formation of interfacial compounds is observed by the appearance of scattering intensity in a different spectral range, which is consistent with the formation of III2VI3 compounds. The potential of Raman spectroscopy for on‐line in situ monitoring of growth processes will be displayed.
Phase transition from the cubic to the hexagonal modification in thin CdS films on InP(110)
Authors: Zahn D. R. T. , Kudlek G. , Rossow U. , Hoffmann A. , Broser I. , Richter W. 
Published: May 2005

AbstractCdS films were prepared by molecular beam epitaxial growth on clean cleaved InP(110) substrates. Films with thicknesses in the 200 nm range were studied by optical techniques: spectroscopic ellipsometry, reflection and photoluminescence. The film thickness and the dielectric function of the films are evaluated from the ellipsometry data. The feature in the imaginary part of the film dielectric function which is induced by the E1 interband transition in CdS is found to be extremely sensitive to the crystal modification. A splitting of this feature occurring at approximately 200 nm indicates a phase transition in the thin films from the cubic to the hexagonal modification. This is confirmed by reflection measurements which show two series of reflection loops for both modifications for film thickness exceeding 200 nm. The energy positions of the free excitons of the hexagonal and cubic modifications are derived. In addition, the band gap for the cubic modification is determined for the first time. The photoluminescence spectra also reveal cubic and hexagonal contribution of donor–acceptor pair recombinations. From the excitonic transitions attempts are made to identify the main impurities in the layers.
High‐density and optical non‐linearity effects in epitaxially grown ZnTe layers
Authors: Wagner H. P. , Festner S. , Stanzl H. , Kudlek G. , Presser N. 
Published: May 2005

AbstractWe investigated the high‐density luminescence and non‐linear transmission of ZnTe layers grown by metal‐organic vapour phase epitaxy (MOVPE). For the high‐density luminescence we compared ZnTe layers on (001) GaAs substrate with free‐standing ZnTe layers of equal thickness. At high excitation intensities a strong luminescence P band appears a few meV below the free exciton energy which is assigned to resonant exciton‐scattering processes. A second strong luminescence N band occurs only in free‐standing layers. It shows a remarkable red shift with increasing intensity and becomes the dominant emission for an excitation intensity Iexc > 1.5 MW cm−2. This lower‐energy band was interpreted as electron–hole plasma recombination.The optical non‐linearity of thin ZnTe layers in the excitonic region was investigated by pump‐and‐probe experiments at 2 K and room temperature (RT). For these experiments we used two different pump energies, one above (at 2 K and RT) and one below (at 2 K) the band gap energy. In all cases a red shift and a large non‐linear decrease in the excitonic absorption with increasing pump intensity was observed. The experimental results can be explained by many‐body effects of exciton screening.
Dynamics of impurity‐related optical switching in CdS near the band edge
Authors: Schmolke R. , Schöll E. , Nägele M. , Gutowski J. 
Published: May 2005

AbstractWe present a dynamic theory related to experiments on the induced transmission of doped CdS crystals under pulsed laser excitation at 2 K at frequencies just below the band gap. Numerical simulations of the optical switching front which describes the non‐linear spatio‐temporal dynamics of the switching process from low to high transmittivity and back are performed for two different two‐level models. These are associated with two different bleaching mechanisms of the acceptor–conduction band transition.
Gain and dynamics of excitons in MOVPE‐grown ZnSe/ZnSxSe1 − x heterostructures
Authors: Umlauff M. , Kalt H. , Langbein W. , Wind O. , Geyzers K. P. , Heuken M. 
Published: May 2005

AbstractOptically pumped stimulated emission in ZnSe/ZnSxSe1 − x heterostructures grown by MOVPE has been observed up to 170 K. Gain measurements have been performed using the variable stripe length method. The underlying gain mechanism at 25 K is atributed to an excitonexciton scattering process. Photoluminescence excitation spectra and the temporal evolution of the luminescence indicate a transfer process from the ZnSxSe1 − x barrier into the ZnSe active layer.