bluuebunny/crossref_metadata_2025_split huggingface dataset:
Delayed luminescence in a molecularly doped polymer (TAPC in polycarbonate)
Authors: Hensel K. , Bässler H. 
Published: May 2005

AbstractDecay of the delayed luminescence of 1,1‐bis(di‐4‐tolylaminophenyl)cyclohexane, both doped into a polycarbonate binder and matrix‐isolated in an MTHF glass, has been studied upon excitation with the 308 nm line of an excimer laser. Time‐resolved emission spectra have also been recorded. In the early time regime, 30 ns < t < 10 μs, the decay of the emission, identified as delayed fluorescence rather than phosphorescence, follows a power‐law characteristic of geminate pair recombination in a disordered medium. Singlet–singlet excitation fusion is considered to be the main pathway for geminate pair formation. Fusion of triplet excitations becomes important for e–h pair formation at long times only (10 μs < t < 10 ms). The rate of triplet–triplet encounters carries a time dependence characteristic of the random walk of excitations in a disordered solid.
The characterisation of GaAs on silicon using polarised laser light
Authors: Morris I. L. , Jenkins T. E. , Goodes S. R. 
Published: May 2005

AbstractMBE‐grown gallium arsenide epitaxial layers on silicon, with thicknesses between 0.1 and 8.1 μm, have been studied using a simple rotating polariser multiple‐angle‐of‐incidence ellipsometer. From these data, information on the roughness of the surfaces of the layers and the anisotropy of the refractive index of the layers has been obtained. The results are compared with data obtained on the same samples using scanning electron microscopy and conventional spectroscopic ellipsometry.
Development of lithographic techniques for metallisation of organic substrates
Authors: Gilmour Sandra , Kershaw Stephen V. , Pethrick Richard A. , Pantelis Philip , Cassidy Steven , Sherwood John N. 
Published: May 2005

AbstractA wide range of applications which involve organic crystalline materials require the metallisation of low‐molecular‐weight compounds. Conventional lithographic techniques used in silicon fabrication technology use high‐temperature processing methods which are unsuitable for organic materials. Gold/titanium bilayer and shadow‐masking techniques were found to provide suitable solutions to the problem of metallisation of these materials and allowed fabrication of a surface acoustic wave (SAW) device with (–)‐2‐α‐methylbenzylamino‐5‐nitropyridine (MBANP) as substrate.
Peculiarities of silicon carbide crystal growth under the diffusion mechanism of vapour transfer
Authors: Lilov S. K. , Yanchev I. Y. 
Published: May 2005

AbstractIn the present work the gas dynamics in the growth zone of SiC crystals is investigated. It is shown that the propagation of SiC vapour from the growth cavity walls towards the lids is effected by diffusion. On this basis the calculation of the concentration distribution of SiC vapour (n), the equilibrium vapour concentration (ns) and the supersaturation (α = [(n – ns)/ns] × 100%) in the crystal growth zone at different radial and axial gradients is carried out by solving the Laplace equation in cylindrical co‐ordinates for a stationary case corresponding to the conditions of crystal growth. The results obtained are compared with the available experimental data, which gives the possibility of explaining some of the observed peculiarities during SiC crystal growth from the vapour phase by the sublimation method.
The influence of bath composition on the photocurrent response and morphology of chemically deposited CdS thin films
Authors: Sebastian P. J. , Nair P. K. 
Published: May 2005

AbstractThe influence of the chemical bath composition on the photocurrent response, film morphology and optical transmittance of chemically deposited CdS thin films is reported. The bath parameters such as concentrations of triethanolamine, thiourea, ammonia and cadmium acetate and the bath temperature controlled the photosensitivity, photocurrent decay, morphology and optical transmittance of the films. The optimum concentration of the bath for getting good‐quality photosensitive films with good optical transmittance was identified in this investigation.
A theoretical study of the hyperpolarisabilities of nickel dithiolene molecules
Authors: Craig B. I. , Williams G. R. J. 
Published: May 2005

AbstractThe hyperpolarisabilities γ of nickel dithiolene complexes have been calculated by the finite field method in combination with the CNDO/S molecular orbital method. This computational technique, which has been developed for calculating the polarisation of large organic molecules by a perturbing electric field, is discussed. The changes in γ that occur as a result of different selections of substituent groups in the dithiolene ligand are described. The results are compared with recent experiments investigating these types of molecules. Large values for γ are found to arise from the interaction of the nickel 3d electrons with the conjugated π‐electrons of the metal–ligand complex.
Metal–Organic chemical vapour deposition of polycrystalline tetragonal indium sulphide (InS) thin films
Authors: Maclnnes Andrew N. , Cleaver William M. , Barron Andrew R. , Power Michael B. , Hepp Aloysius F. 
Published: May 2005

AbstractThe dimeric indium thiolate [(tBu)2In(μ‐StBu)]2 has been used as a single‐source precursor for the metal–organic chemical vapour deposition (MOCVD) of InS thin films. The dimeric In2S2 core is proposed to account for the formation of the non‐equilibrium high‐pressure tetragonal phase in the deposited films. Analysis of the deposited films has been obtained by transmission electron microscopy (TEM), with associated energy‐dispersive X‐ray analysis (EDX) and X‐ray photoelectron spectroscopy (XPS).
Second‐Order optical non‐linearities of {4‐(dimethylamino) stilben z & e 4'‐yl} dimesityl borane
Authors: Lequan Minh , Lequan Rose Marie , Chane‐ching Kathleen , Callier Anne‐claude , Barzoukas Marguerite , Fort Alain 
Published: May 2005

AbstractSamples of {4‐(dimethylamino) stilben Z & E 4'‐yl} dimesityl borane (BNS) were synthesised and investigated for their non‐linear optical properties. The results show that the quadratic hyperpolarisability of the Z‐isomer is smaller than that of the E‐isomer, the beta value found for the latter being as high as 60 × 10−30 esu.
An investigation of LPCVD and PECVD of in situ doped polycrystalline silicon for VLSI
Authors: Ahmed Waqar , Ahmed Ejaz 
Published: May 2005

AbstractIn general, high‐temperature processes cause thermal stresses and diffusion of dopants, resulting in reduced device yields. It is thus desirable to reduce the number of high‐temperature steps and the use of an in situ doping technique eliminates one such step. In this investigation, low‐pressure chemical vapour deposition (LPCVD) and plasma‐enhanced chemical vapour deposition (PECVD) have been utilised to deposit in situ doped polycrystalline silicon films. The process characteristics and properties such as spreading resistance, grain structure, etch rate using a plasma and dopant concentrations of these films have been investigated and explained using a simple model for dopant activation and grain growth. It is shown that good‐quality films suitable for VLSI can be produced.
Electrochemical synthesis of electroactive polyaniline in organic solutions
Authors: Pasquali M. , Pistoia G. , Rosati R. 
Published: May 2005

AbstractPolyaniline films have been grown in solutions based on acetonitrile or acetonitrile/nitromethane mixtures by galvanostatic, potentiostatic and cyclic voltammetry techniques. LiClO4 or anilinium tetrafluoborate was used as a salt. With the latter, aniline was absent in some tests, since anilinium could act simultaneously as a charge carrier and a polymerising species. The film characteristics have been evaluated by cyclic voltammetry, impedance spectroscopy and SEM experiments. It has been found that the protons released by aniline (following oxidation) or anilinium can be made available to the g| wing chains if the protophilic character of the solvent is sufficiently low. In a 1/1 acetonitrile/nitromethane mixture the galvanostatic and potentiostatic techniques produce electroactive films of reduced resistance, especially if anilinium tetrafluoborate is present. These seem to be the best conditions for the synthesis.
Stability of electrochemically prepared polyaniline films in aqueous and organic solutions
Authors: Pasquali M. , Pistoia G. , Fiordiponti P. 
Published: May 2005

AbstractElectroactive polyaniline films have been grown by galvanostatic, potentiostatic and cyclic voltammetry techniques in organic solutions based on LiClO4 or anilinium tetrafluoborate as salts and acetonitrile or acetonitrile/nitromethane mixtures as solvents. After storage of these films in a 1 M H2SO4, Na2SO4 aqueous solution, their stability was tested by cyclic voltammetry and impedance spectroscopy in this solution. Different levels of retention of the anodic charge have been found depending on the electrochemical technique and preparation solution. The impedance tests have revealed limited changes in the charge transfer resistance upon storage. This has been interpreted on the basis of a limited deactivation of the films, which in some cases would instead experience physical changes. Confirmation of this assumption was obtained via an SEM experiment.Films prepared by cyclic voltammetry in the above acidic solution and stored in acetonitrile‐or propylene‐carbonate‐based electrolytes show major degradation processes, as evidenced by the appearance of quinone‐like compounds and the marked increase in the charge transfer resistance.Finally, films prepared by different electrochemical techniques in acetonitrile‐based solutions and stored in LiClO4‐acetonitrile reveal moderate degradation phenomena.
Chemical sensing by an electrical oscillator: Detection and quantification of cationic surfactants
Authors: Nakata Satoshi , Yoshikawa Kenichi , Shima Osamu , Terada Hiroshi 
Published: May 2005

AbstractA new chemical sensing system using an electrical oscillator has been developed. This sensing system measures the electrical ‘non‐linearity’ at the surface of an electrode immersed in a test solution: a sinusoidal voltage is applied to the electrode and the higher harmonics of the output current are obtained by Fourier transformation. This sensing system has been used to detect and quantify surfactant molecules in solutions. The relative intensity P2/P1 of the peaks of the second (P2) and first (P1) harmonics in the output current was found to be linearly correlated with the logarithms of the concentrations of cationic surfactants such as cetylpyridium bromide (CPB) and cetyl‐N,N,N‐trimethylammonium bromide (CTAB), but not with those of the anionic surfactant sodium dodecyl sulfate (SDS) or the neutral surfactant Triton X‐100. The reproducibility of this sensing system was shown to be excellent.
Mass spectrometric study of laser‐induced pyrolytic decomposition of TMA
Authors: Ivanov B. , Popov C. , Shanov V. 
Published: May 2005

AbstractThe composition of the gaseous phase during pyrolytic laser‐induced chemical vapour deposition (LCVD) of aluminium from trimethylaluminium (TMA) was determined. The analysis was carried out in situ by means of a quadrupole mass spectrometer (QMS) in a closed reaction cell. The decomposition of the aluminium alkyl was induced by a copper bromide vapour laser on the surface of (111) silicon monocrystalline wafer at 0.22 GW m−2 average power density, 120 μm s−1 scanning speed and 100 Pa (1 mbar) partial pressure of TMA. The detected gaseous products of the pyrolysis of TMA were ethane, ethylene, methane and hydrogen. The presence of ethane and ethylene was probably due to the unconventional way of decomposition caused by pulsed laser irradiation. The mass peak dynamics of the created pyrolytic products at m/e = 28, 16 and 2 indicated significant production of ethane + ethylene, methane and hydrogen in the ratio 1:5:1.75.
Liquid crystalline siloxanes containing spiropyran chromophores as reversible optical data storage materials
Authors: Natarajan L. V. , Tondiglia V. , Bunning T. J. , Crane R. L. , Adams W. W. 
Published: May 2005

AbstractThe application of liquid crystalline siloxanes consisting of pentamethylhydrocyclosiloxane cores with attached cholesteryl‐, biphenyl‐ and photochromic spiropyran‐based mesogens as reversible optical data storage materials is demonstrated by grating formation with an argon ion laser beam operating in the UV and visible regions. Erasure of the gratings with heat or visible radiation was possible.
Low‐Pressure chemical vapour deposition of tantalum pentoxide films for ulsi devices using tantalum pentaethoxide as precursor
Authors: Treichel H. , Mitwalsky A. , Sandler N. P. , Tribula D. , Kern W. , Lane A. P. 
Published: May 2005

AbstractA laminar flow low‐pressure chemical vapour deposition (LPCVD) system (LAM IntegrityTM) has been used to deposit tantalum pentoxide (Ta2O5) from Ta(OEt)5 films in the presence of oxygen (O2) at 470 °C at a typical deposition rate of 4 nm min−1. Uniformities of <1.5% (SD 1σ) over a 150 mm silicon substrate were obtained. The layers were annealed under different conditions. It was discovered that the films did not change their stoichiometry as determined by Rutherford backscattering (RBS). The as‐deposited films were amorphous but became crystalline (β‐Ta2O5) at temperatures > 700 °C. The transmission electron microscopy (TEM) results on crystallisation behaviour were supported by X‐ray diffraction data. The electrical properties of the Ta2O5 films have been characterised using MIS (metal/insulator/silicon) capacitor structures. Leakage values of <10−6 A cm−2 at 6 MV cm−1 equivalent applied electric field and breakdown strengths of >7 MV cm−1 at 1.6 μA were obtained for annealed layers. Compound dielectric constants (native silicon oxide thickness of about 2.5 nm plus Ta2O5 of various thicknesses) between 14 and >30 have been measured. The electrical properties reveal the potential use of Ta2O5 as a storage capacitor dielectric in 64 and 256 Mbit DRAM (dynamic random access memory) devices.
The pyrolytic LCVD of high‐purity gold tracks from alkyl (trialkylphosphine) gold(I) complexes
Authors: Davidson J. L. , John P. , Milne D. K. , Roberts P. G. , Jubber M. G. , Wilson J. I. B. 
Published: May 2005

AbstractThe pyrolytic LCVD of high‐purity gold tracks from the organogold(I) complex MeAuPMe3 is reported. The tracks were deposited onto (100) n‐type single‐crystal silicon with a thermally grown oxide layer (3000 Å), single‐crystal GaAs with an intact native oxide layer and polycrystalline diamond films upon (100) silicon using the output from an argon ion laser (Coherent Innova 100‐10) at 514.5 nm. Deposits were grown at a range of scan speeds from 0 to 200 μm s−1 and characterised by SEM, SIMS, LIMA and scanning profilometry. Electrical resistivities as low as 7.04 μΩ cm, within a factor of three of that of bulk gold, were achieved at scan speeds below 156.3 μm s−1. These are consistent with deposit purities of better than 99% (LIMA) without the need for a post‐deposition annealing step.The relationship between power density, beam residence time and deposition rate was measured. The morphology of the deposit from the onset of detectable nucleation through to the formation of continuous tracks was analysed by SEM micrographs of deposits grown at successively increasing power densities. The nucleation process was found to be substrate‐dependent. Changes in deposit morphology with power density and scan speed were observed. These include periodicity in track width and at high power densities the development of ‘volcano’‐shaped profiles.The formation of a phosphorus‐based interfacial layer, exclusive to laser deposition upon GaAs, is evidence for a reaction between the PMe3 and GaAs.
A modified plasma source for controlled layer thickness synthesis in laser pulse vapour deposition (LPVD)
Authors: Dietsch R. , Mai H. , Pompe W. , Völlmar S. 
Published: May 2005

AbstractThe conventional thin film deposition equipment of LPVD has been modified for the preparation of nanometre‐layer stacks of uniform thickness at reduced target/substrate separation. Therefore the planar target was replaced by a cylindrical one and the target motion regime has been modified.During thin film deposition a substrate translation is preferred instead of the usual rotation technique. With this arrangement the emission characteristic of the plasma source can be computer controlled and tailored via a stepper‐motor‐driven manipulator for the desired layer thickness profile across an extended substrate. Thus, for example, a homogeneous film thickness is obtained even for lower target/substrate distances, and an appropriate deposition rate can be maintained.First applications of the equipment are explained and compared with typical results of the conventional technique.
Low‐temperature plasma‐assisted processes for fabrication of SiO2/Si heterostructures
Authors: Lucovsky Gerald 
Published: May 2005

AbstractIn the conventional high‐temperature thermal oxidation and rapid thermal oxidation processes used to fabricate commercial SiO2/Si structures at ∼850–1050°C, the SiO2/Si interface and the bulk oxide are formed at the same time. We have developed a low‐temperature process for the formation of SiO2/Si structures at 200–300°C that separately controls and optimizes the properties of the SiO2/Si interface and the bulk SiO2. This has been accomplished by separating interface formation by plasma‐associated oxidation from bulk oxide plasma‐assisted deposition. The oxidation step (i) removes residual C contamination from the Si surface, (ii) prevents N incorporation at the interface from the O atom source gas N2O and (iii) forms an oxide layer ∼0.6 nm thick and an SiO2/Si interface with a trap density, Dit ≈(1–4) × 1010 cm−2 eV−1. This type of process has also been extended to the deposition of multilayer oxide–nitride–oxide dielectrics.
Laser‐induced deposition of aluminium on gallium arsenide from trimethylamine alane
Authors: Bourée J. E. , Tonneau D. , Sayah A. , Frugier T. , Boulahia A. , Mencaraglia D. , Siffre J. M. 
Published: May 2005

AbstractAluminium microstructures (dots or strips) have been photodeposited on GaAs substrates via the decomposition of a solid precursor, the 2:1 hydride adduct of Al, called trimethylamine alane (TMAA).The dissociation of TMAA, the vapour pressure of which can be varied between 0.4 and 1 mbar by dilution in hydrogen carrier gas, has been achieved via a pyrolytic process using a CW Ar+ laser operating in the visible range (488–514 nm). This decomposition reaction occurs at laser powers higher than 0.3 W, i.e. at laser‐induced temperatures higher than 130°C, and leads to the formation of high‐purity aluminium strips as observed from Auger electron spectroscopy (AES) and energy‐dispersive X‐ray analysis (EDX) data. The deposition rates are in the range 50–1400 Å s−1. The minimum of line resistivity measured versus scanning speed and laser power is 6.5 μΩ cm.The photolytic decomposition of TMAA has been performed at room temperature within the laser spot area using a CW UV laser (intracavity frequency doubler emitting at 257 nm). The formation of aluminium clusters has been observed at very low deposition rates (20 Å s−1). However, these tiny clusters react quickly with oxygen and are transformed into alumina clusters.All these results have been tentatively explained on the basis of the surface reactivity of H2 and TMAA regarding GaAs or Al, as obtained by other workers through surface science techniques and mass spectrometry.
Laser cleaning: Laser‐induced removal of particles from surfaces
Authors: Zapka W. , Ziemlich W. , Leung W. P. , Tam A. C. 
Published: May 2005

AbstractPulsed‐laser‐induced removal of particles from surfaces is a new cleaning technique. This laser cleaning can be performed on dry surfaces as well as on wet surfaces with a micron‐thick liquid film during pulsed laser irradiation to provide enhanced removal efficiency. Using the latter technique, to be called ‘steam laser cleaning’ here, we are able to remove epoxy, alumina, silicon or gold particles with diameters in the range 0.1–10 μm from silicon and other surfaces.
Damage of STM tips during nanofabrication
Authors: Yokoi N. , Namba S. , Takai M. 
Published: May 2005

AbstractThe STM tip shape was found to change when nanofabrication using a scanning tunnelling microscope (STM) was attempted by applying voltage pulses between the tip and the sample. This change, which is considered to be caused by the voltage pulses, was studied systematically to investigate the thermal contribution to nanofabrication using STM tips. The tips become easily damaged as the pulse amplitude and pulse width increase or the tunnelling gap decreases. Thermal reaction, including thermochemical reaction, is considered to play an important role in such nanofabrication.
Pulsed laser deposition of some II–VI compounds and alloys
Authors: Aydinli Atilla , Compaan Alvin D. 
Published: May 2005

AbstractPulsed laser deposition (PLD) of materials is a growing field with applications to many systems. With many materials, however, a major problem is particulate formation due to splashing of molten droplets or ablation of solid clusters from the target. For the case of II–VI semiconductors we have found that careful selection of the laser power density and appropriate mastering of the beam could reduce particulate formation to a negligible level even with the use of pressed targets. In this work we have deposited a number of II–VI semiconductors and their alloys, using XeCl and Nd:YAG lasers, from pressed and bulk targets onto various substrates in high vacuum. The ternaries of ZnTe and ZnSe as well as of ZnTe and CdTe were studied in detail. We determined the optimum growth temperatures and deposition rates for the growth of optical quality films. X‐ray diffraction, optical absorption, energy‐dispersive X‐ray analysis and Raman scattering were used to characterise these films or grain size and orientation, optical band gap and alloy effects on photon bands.
Excimer laser micromachining
Authors: Ihlemann J. , Schmidt H. , Wolff‐Rottke B. 
Published: May 2005

AbstractThe machining of several materials such as polymers, metals and ceramics using excimer lasers (193, 248 and 308 nm) was investigated. By photoablation, micrometer resolution can be achieved for polymers if the wavelength and fluence are chosen properly. High‐definition processing of metals is complicated by the occurrence of surface melting. An interaction between the ablation plume and the walls of the laser‐drilled holes leads to hole widening in the case of polymers at high fluences. For small structures (<100 μm) all materials investigated show a size‐dependent ablation rate. This effect has to be taken into account if a precise ablation depth is required for a pattern with structures of different sizes.
Ceramic thin films deposited on Si(100) by laser ablation: Application as buffer layers for YBa2Cu3O7 films
Authors: Sánchez F. , Varela M. , Queralt X. , Carcía‐Cuenca M. V. , Palau J. , Aguiar R. , Morenza J. L. 
Published: May 2005

AbstractCeramic thin films of yttria‐stabilised zirconia (YSZ), SrTiO3(STO) and CeO2 have been deposited on Si(100) substrates by laser ablation. The films have been characterized by X‐ray diffractometry, field emission scanning electron microscopy and secondary ion mass spectrometry (SIMS). The effects of the oxygen partial pressure during deposition and the substrate temperature were studied. All the films have preferential orientation: (h00) and (hh0) for STO and (hhh) for CeO2 and YSZ. The films show a low density of particulates and a very smooth surface. SIMS profiles indicate a low interdiffusion between film and silicon. One of the applications of these materials is their use as a buffer layer for the growth of YBCO on silicon. Because both materials are highly reactive, it is necessary to put a barrier between YBCO and silicon. For this purpose we used the ceramic films previously deposited in order to obtain superconducting YBCO films. The deposited YBCO films present good superconducting properties with zero resistance at temperatures between 80 and 85 K.