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The (Na1-xKx)0.5Bi0.5TiO3 perovskite solid solution is investigated using x-ray diffraction (XRD) and Raman spectroscopy in order to follow the structural evolution between the end members Na0.5Bi0.5TiO3 (rhombohedral at 300 K) and K0.5Bi0.5TiO3 (tetragonal at 300 K). The Raman spectra are analysed with special regard to the hard modes and suggest the existence of nano-sized Bi3+TiO3 and (Na1-2xK2x)+TiO3 clusters. The complementary use of XRD and Raman spectroscopy suggests, in contrast to previous reported results, that the rhombohedral ↔ tetragonal phase transition goes through an intermediate phase, located at 0.5 ≤ x ≤ 0.80. The structural character of the intermediate phase is discussed in the light of sub- and super-group relations. © 2000 IOP Publishing Ltd.

Raman imaging has been used to investigate the microstructure of some (100)-textured diamond films. Results have shown that different crystals within a film can give rise to different Raman line positions, intensities and line widths, with the result that the overall diamond line is the sum of all the individual contributions from all the different crystals. The images presented herein first show considerable variation in the distribution of amorphous carbon and defects producing the luminescence background. These defects were mostly detected within the grain boundaries, confirming most of the previous studies. These examples also emphasize the amount of variability that may be detected in the line shape of the Raman diamond line. In particular, line splitting was observed for all the samples examined, and in some particular cases was the most dominant feature that was observed. Such a line splitting has to be related to strain fields that exist within the crystals. However, it was impossible to correlate line shift or line splitting to the presence of defects such as amorphous carbon or point defects giving rise to the luminescence background.

Tin dioxide nanocrystalline powders were prepared by precipitation ofα-stannic acid followed by various thermal and chemical treatments. An original preparation via a colloidal solution step led to particles having a particular two-dimensional microstructure. The size of the crystallites was found to increase from 2 nm for as-prepared samples to 30 nm for samples annealed for 3.5 hr at 920°C. The compounds were characterized by X-ray diffraction, scanning electron microscopy (SEM), and infrared and micro-Raman spectroscopy. As reported in the literature, the Raman spectral signature was found to change drastically with the size of the particles. A new spectral feature centered at about 500 cm−1was found for compounds prepared via the colloidal step and having typical sizes smaller than 4.5 nm. The powder Raman spectra are interpreted in terms of volume modes and surface modes. Their frequency evolution with crystallite size is discussed in terms of tensile surface stresses.

A sequential analysis of the growth of diamond films on silicon substrates in a microwave plasma assisted chemical vapor deposition (CVD) reactor has been performed by Raman spectroscopy. The plasma was switched off during measurements, but the substrate heating was maintained to minimize thermoelastic stresses. The detectivity of the present experimental setup has been estimated to be about a few tens of μmg/cm2. From such a technique, one expects to analyze different aspects of diamond growth on a non-diamond substrate. The evolution of the signals arising from the substrate shows that the scratching treatment used to increase the nucleation density induces an amorphization of the silicon surface. This surface is annealed during the first step of deposition. The evolution of the line shape of the spectra indicates that the non-diamond phases are mainly located in the grain boundaries. The variation of the integrated intensity of the Raman signals has been interpreted using a simple absorption model. A special emphasis was given to the evolution of internal stresses during deposition. It was verified that compressive stresses were generated when coalescence of crystals took place.

Vickers microindentations obtained with loads between 0.05 N and 2 N were performed on crystalline (100) silicon. The residual stress field and the different structural states induced by loading were studied by mapping the indented zones by their micro-Raman response. A Raman signature of amorphous silicon is found in the center of the impression. The energy of the Γ25 zone center phonon is found to vary from 522 cm−1 when probing the silicon at a distance of 80 μm from the center of the indentation up to 527 cm−1 when probing the pileup region of the impression. When probing cracked zones in the vicinity of the pileup region, wave numbers as high as 536 cm−1 are measured. The stress components induced by a point indentation (1 N) have been calculated from analytical expressions given in the literature. For an average conversion factor of 3.2 cm−1/GPa, the residual local stresses after unloading are found of the same order of magnitude or even larger than the calculated stresses that are generated during loading. A tentative explanation is proposed. Finally a systematic laser-induced thermal treatment of the central area and of the pileup region of indentations was performed. It is shown that the amorphous silicon in the center can partly recrystallize but that the residual stress state in the pileup region cannot be completely relaxed by local laser heating.

A polarized Raman study of tetragonal monocrystalline WSi 2 is reported. The two Raman lines of WSi 2 have been assigned in terms of symmetry. Using a linear chain model, force constants of 6.64 and 3.16 N/cm for compressive Si-Si and Si-W motions along the c axis of the unit cell have been derived. The values of 3.30 and 2.30 N/cm for the shear motions perpendicular to the c axis have been obtained. Polarized Raman spectra of a thermally annealed WSi 2 film reveal a preferred orientation of the layer; this effect is confirmed by X-ray diffraction. The thermal behavior of the WSi 2 Raman lines has been analysed both for single crystal and thin firm over a wide temperature range (79–853 K). The wavenumbers, half-widths and intensities are strongly temperature dependent. The frequency shift has been related to the thermal expansion of the crystal, using the Gruneisen theory. The important broadening of the A 1g mode with temperature is explained in terms of anharmonicity and the loss of intensity of the two lines is discussed.

Raman spectroscopy is the most frequently used tool to characterize diamond films prepared by various deposition methods. Hence, in situ Raman monitoring of the growth of plasma CVD diamond films may contribute to the understanding and the control of the growth process. As an attempt to improve our previous in situ Raman measurements, a new spectrometer is used, specifically designed for this application and optimized for analysis in the UV spectral range. In this paper the first results of this in situ analysis are presented and compared to those obtained with a more usual excitation in the visible spectral range. Careful temperature measurements during diamond deposition are made both using the temperature induced shift of the lines arising from the substrate and from the Stokes to anti-Stokes intensity ratio. Then, the frequency of the diamond line is related to stress incorporation within the films. It is shown that there is a large stress gradient within the film thickness.

Heavily B‐doped polycrystalline diamond films ([B]≳1019 cm−3) are studied by Raman spectroscopy and electron spin resonance. The formation of an impurity band is accompanied by a Fano‐type interference for the one‐phonon scattering. Bands at 1200 and 500 cm−1 are observed in Raman spectroscopy for concentrations above 1020 cm−3. They are related to maxima in the phonon density of states, and are ascribed to disordered regions or crystalline regions of very small size. The concentration of defects associated with the paramagnetic signal observed around g=2.0030 increases drastically above 1021 B cm−3. The Mott insulator‐metal transition is accompanied by the presence of a new paramagnetic signal (g=2.0007 for 2×1020 B cm−3, g=1.9990 for 1021 B cm−3) ascribed to free holes in the impurity band.

Textured diamond films prepared by CVD were studied by X-ray measurements and Raman spectroscopy in the high dispersive mode in order to get structural information. A 〈100〉 fibre texture is observed for the films prepared with a 2% methane concentration and a low substrate temperature. For all the 2% CH4 samples the diffraction spectra reveal an important broadening of the 111 reflection and two additional bands at about 0.207 and 0.217 nm attributed to stacking faults along the 〈111〉 direction. Domains of hexagonal symmetry can then locally be formed with the defect ordering. The recording of a 1322 cm−1 Raman line generally attributed to the lonsdaleite or hexagonal diamond polytypes supports this assumption. This 〈100〉 fibre texture is recorded for samples obtained with a high methane concentration (2%) related to a fast growth rate, which may explain these stacking faults along the 〈111〉 direction.

A setup designed for characterization of a diamond film during its growth in a dc plasma jet chemical vapor deposition reactor is described. It is composed of a pulsed laser and the detector is gated in order to synchronize the Raman detection with the laser pulses. The optical components are designed for working in the visible and near UV. The installation is specially designed for remote detection and can be used in industrial reactors as well as in laboratory experiments. The detectivity of the setup is analyzed through some typical diamond spectra and it is shown that it is of the same order as that of a micro‐Raman multichannel spectrometer. Some results are reported on how the temperature and the quality of the film can be controlled during the deposition process or during its etching by H2 reactive plasma. These results are discussed and confirmed by ex situ measurements including Raman, infrared, and scanning electron micrographs obtained on the same samples or in the same conditions as for in situ experiments. The secondary nucleation is responsible for the loss of Raman intensity and it could have some cyclic character.

Coupled impedance and Raman measurements were achieved on a ceramic of undoped BaCeO 3 in the 25–600 °C temperature range under air, argon, nitrogen and carbon dioxide. The sample was studied both in micro and normal Raman spectroscopy. At 600 °C, in air, the conductivity of the compound decreases from 3 × 10 −7 to 1.5 × 10 −7 S · cm −1 after a thermal cycle. The nature of the charge carriers is only briefly discussed. The simultaneous measurement of the Raman spectra and of the impedance diagrams has allowed to show that a large part of the variations of the conductivity is due to the structural changes induced by the temperature variation. Reciprocally, this coupled study contributes to the understanding of the phase transition mechanism. The resistance of the compound and the intensity of the 133-110 cm −1 Raman band vary in the same way when the temperature is raised or lowered between 400 and 600 °C. These observations could be related to the growth of the domains of the tetragonal phase. Their kinetics of growth is favored at 600 °C but their thermodynamic stability should be maximum at about 450 °C: actually, as it can be deduced from the reduction of the fullwidth of the Raman bands and from their intensity, the long range ordering takes place at about 450 °C, while the nucleation process would start at a lower temperature. This process should start between 180 and 350 °C and is characterized by the variation of the frequencies of the modes at low energy. Thus, the increase of the resistance when the sample is maintained at 600 °C should be related to the ordering of the tetragonal phase and the large fluctuations in the electric signal which are observed between 200 and 450 °C could be related to the fluctuation of the sizes of domains. Finally, some preliminary results related to the influence of water and of carbon dioxide are mentioned.

A set-up designed for the Raman characterization of a diamond film during its growth in different plasma CVD reactors is described. It is composed of a pulsed laser and a gateable detector in order to synchronize the Raman detection with the pulses of the laser. The optical components are designed for working in the visible and near UV. The installation is specially designed for a remote detection and can be used in industrial reactors as well as in laboratory experiments. The detectivity of the set-up is analysed through some typical diamond spectra and it is shown that it is of the same order of what is obtained with a micro-Raman multichannel spectrometer equipped with a continuous laser. Some results are reported; it is shown how this set-up may be used to control in real time the deposition process.

Diamond is deposited from 100 sccm H 2 /0.5 sccm CH 4 or 100 sccm H 2 /4 sccm CH 4 /2 sccm O 2 by microwave plasma assisted chemical vapour deposition, either in the middle of the plasma ball or in a remote position at the level of the bottom wall of the wave guide. When H 2 /CH 4 mixtures are used, from Raman spectroscopy the parasitic phases concentration and the full width at half maximum (FWHM) of the diamond line are seen to decrease from the middle to the bottom position. In the bottom position, the diamond crystallite characteristics are further improved by using the mixture containing oxygen: no parasitic phases can be detected, and the FWHM remains between 3 and 4 cm −1 between 680 °C and 880 °C. The concentration of luminescent centers (from the Raman backgrounds) also decreases for a lower deposition temperature, O 2 in the gas, and a remote substrate position, but has a minor effect on the FWHM. These centers are ascribed to defects in the bulk of the crystallites while the FWHM and non-diamond Raman signal are both ascribed to parasitic phases on the crystallite surfaces. Coherent phenomenological models are proposed for the origins of the decrease of the FWHM and of the concentration of the luminescent centers with the previous deposition conditions.

Mineral compounds Li1 + xAlxTi2 − x(PO4)3 (x = 0 and x = 0.3) have been made by cogrinding and soil-gel processes. Structural characterizations by X-ray diffraction and Raman spectroscopy indicate that alumina substitution (x = 0.3) does not modify the crystallographic structure, whatever the synthesis process: compounds crystallize in the rhombohedral system with an R-3C space group. The use of the sol-gel route makes low-temperature sintering (950 °C) easier and, moreover, leads to ceramics with a high water stability. Li1.3Al0.3Ti1.7(PO4)3 compounds are fast ionic conductors: σ25 °C varies from 15−5 to 10−4 S cm−1, depending on the synthesis process. They have been used as ionic membranes for lithium-selective electrodes. Sensors prepared with sol-gel membranes have the best performance: the detection limit is 1.4 × 10−4 mol dm−3. The potassium and the protonic selectivity properties are attractive for such electrodes. For sodium, they need to be improved for biomedical applications.

Diamond and carbonaceous films grown in a microwave assisted plasma reactor have been characterized by x‐ray diffraction, scanning electron microscopy, and Raman spectroscopy. This study is mainly focused on the identification of the different carbonaceous compounds which can coexist with the diamond depending on the synthesis parameters. Selective etching reactions and the excitation wavelength dependence of Raman cross sections of the different carbon species reveal that the broad and poorly structured Raman spectra in the 1100–1700 cm−1 region contain six components that arise from three different carbonaceous species: (i) one species is graphitic and is identified from the components at about 1350 and 1590 cm−1 which are resonantly enhanced as compared to the other components when the excitation energy is lowered from 3 to 2 eV. (ii) The second species is associated with the two broad bands at 1350 and 1550 cm−1 and is attributed to amorphous diamond‐like carbon (a‐C:H); both bands are resonantly enha...

An experimental set‐up designed for in situ Raman analysis during the growth of diamond films in a microwave plasma reactor is described. A gated multichannel detection synchronized with a pulsed YAG laser is used to discriminate the Raman signals from the plasma emission. The in situ detection of a diamond film during its growth on a single crystal of alumina substrate is presented. The detectivity of the method has been estimated to be about a few tens of μg/cm2 for an acquisition time of 800 s. Peak shifts are interpreted in terms of temperature and stress dependences. It is shown that the diamond in the first stages of deposition is free of stress, then when grains come into contact compressive stresses are observed, when the film thickness reaches about 1 μm stresses are relaxed.

Diamond films were prepared in a microwave plasma-assisted chemical vapour deposition (CVD) reactor. The deposition parameters were deliberately optimized to obtain mixtures of diamond and different carbonaceous compounds. We present the results of an in-situ Raman study of the growth of such films and of their etching under different atmospheres. At least six Raman bands in the range 1100–1600 cm−1 were observed; their relative intensity variation with the elaboration parameters, with the excitation wavelength and with the etching conditions led to the conclusion that at least three different carbonaceous forms are present in CVD diamond films. During the growth process, one first obtains the diamond phase along with a diamond-like compound; the disordered graphitic form appears only in a second stage.

The effectiveness of doping in polycrystalline CVD diamond by 10 13 –10 16 cm −2 boron implantation at 77 K followed by annealing at 800 °C has been studied by Raman scattering and I(V, T) measurements. The amorphization threshold is found to be located around a boron doping of 3 × 10 15 cm −2 . Subsequent annealing of samples implanted with boron doses below and above this threshold results respectively in doped semiconducting diamond and graphite. In the high temperature range, the activation energies (between 0.61 and 0.15 eV) are discussed assuming a highly compensated semiconductor behaviour. In part of the low temperature range, hopping conduction occurs. The compensating centres are suggested to originate from native as well as implantation-induced defects.

Nonhydrogenated diamondlike carbon films have been prepared by dual ion beam sputtering and ion‐beam‐assisted magnetron. The assistance parameters—ion energy, ion mass, ion flux/atom flux—have been systematically varied, and the films have been characterized by Rutherford backscattering spectroscopy, high‐resolution transmission electron microscopy, electron energy loss spectroscopy, positron annihilation spectroscopy, Raman spectroscopy, and nanoindentation. It was found that the density and the degree of disorder of the films go through a maximum with ion energy, and the void concentration goes through a minimum. Microstructure analysis shows that the films are mostly sp2 bonded, with a maximum of about 16% concentration of sp3 bonding from the largest values of density. The evolution of density with ion flux and energy is consistent with a combined effect of atomic displacements in the film leading to densification, and damage buildup leading to progressive graphitization as the energy is increased. Th...

Polycrystalline samples of perovskite-structured BaCeO3 and SrCeO3 were studied by Raman scattering spectroscopy in the temperature range 77–983 K. Changes in the spectra of BaCeO3 with temperature are explained in terms of a second-order phase transition (D2h D4h) at T0 = 427 K. Analysis of the temperature dependence of soft modes suggests a partial displacive character. A dramatic decrease in band intensity above 1000 K indicates a transition to the cubic (Oh) structure, for which no Raman bands are expected. The Raman spectra of SrCeO3 indicate that no phase transitions occur in the temperature range 77–983 K. Room temperature spectra of BaCeO3 doped with various rare earth ions (Nd3+, Gd3+, Yb3+) are compared. Doping with 5 and 10 mol.% Nd stabilizes the high-temperature tetragonal and cubic phases, respectively. The crystal structure is a sensitive function of Nd dopant concentration.

The Raman spectra of powdered sulfamide and deuterosulfamide have been recorded at 300 and 77K in the 4000-50 cm −1 range. Polarized Raman spectra of oriented microcrystals and oriented films have also been obtained. New bands are evidenced and some framework modes have been reassigned. Special attention has been given to the low-frequency region as no data exists in the literature. The analysis of the NH stretching bands indicates the existence of non-equivalent protons within the same amine group fo the sulfamide molecule: a practically free proton H f and a proton H b involved in a moderately strong hydrogen bond. The different intra- and intermolecular couplings have been derived for the NH vibrators. A phase transition preceding melting seems probable. The melting transition has also been studied.

We present the measured dependence of the Raman intensity on the thickness of the metal film in a Kretschmann geometry when surface plasmons are excited. To perform our work, we deposited a Ag film of varying thickness onto a prism, and then we coated it with a thin layer of copper phthalocyanine. We show that the maximum of the Raman signal is achieved for an overall optimization of the coupling at both pump and Stokes frequencies, demonstrating the simultaneous excitation of surface plasmons at these two frequencies.

Raman scattering studies of perovskite-structured BaCeO 3 acceptor-doped with the rare earth ions Yb 3+ , Gd 3+ and Nd 3+ are presented. Room temperature spectra of BaCeO 3 doped with 5% Yb 3+ and 5% Gd 3+ are similar to that observed for undoped BaCeO 3 , having an orthorhombic perovskite structure. However, 5% doping with Nd 3+ results in a strikingly different Raman spectrum with fewer bands, indicating a tetragonal structure. Moreover, the distortion of the structure towards the higher symmetry phase is an increasing function of Nd dopant concentration, 10% doping giving a nearly cubic structure. A broad band appearing at 624 cm -1 which increases in intensity with increasing Nd dopant concentration probably arises from dopant-oxygen ion vibrational modes. The Raman scattering results are interpreted in terms of the ionic radii of the dopants and, further, are compared to existing conductivity results.

Recently, a new method using carbon implantation at 300 K in bulk copper followed by excimer laser annealing has been proposed to synthesize diamond, with contradictory results. We use this technique on copper thin films with carbon implantation at 77 and 300 K. From Rutherford backscattering spectrometry, the C, Cu and Si profiles have been deduced. They suggest solid state diffusion during annealing. The carbon depth profiles are found to be mainly dependent on the implantation temperature. The Raman spectra are well fitted by the same three and sometimes four gaussian components. The fourth component centred between 1305 and 1340 cm−1 is tentatively assigned to diamond.

Room temperature Raman scattering spectra of the perovskitestructered cerates BaCeO3 and SrCeO3 are compared and analyzed, based on factor group analysis of the space group D2h16. High temperature spectra of BaCeO3, collected in the temperature range 25–800°C, indicate that the material undergoes an orthormbic to tetragonal (D2h → D4h) phase transition in this range. A tetragonal to cubic (D4h → Oh) phase transition is expected at temperatures slightly above 800°C.

Raman spectroscopy has been used to characterize carbon films grown on silicon by the pulsed laser evaporation of graphite targets. Spectra from films of thickness ranging from 1 nm to a few micrometers have been analysed. The influence of the deposition geometry has been investigated by varying the angle between the target-substrate direction and the normal to the target surface. At increasing substrate temperatures, the spectra evolve from diamond-like to glassy carbon and to carbide. For 1 nm films, a relatively uncommon has been observed line at 1470 cm−1.

Diamond films were deposited on silicon substrates at 750 °C, by the hot-filament technique, from a reactive CH 4 (0.1–2%) H 2 mixtures. Two wide Gaussian lines around 1330 and 1500 cm−1 with coupled variations in the whole preparation range appeared in the global Raman spectra. They were attributed to intermediate carbon defects in the diamond crystallites, which might control the confinement length of diamond phonons. Their contributions to the diamond line shift and width for all the samples is calculated and compared with the experimental results. The remaining shift is attributed to the stress (up to 1.2 GPa), while the origin of the remaining widening (large distribution of stress or Raman inactive additional defects) is discussed.

We present the Raman characterization of carbon films prepared on (100) silicon substrates by remote microwave plasma enhanced CVD in a gaseous mixture of CH 4 in H 2 . The set of samples was obtained by varying the methane concentration from 0.5 to 5.0% for different substrate temperatures ranging from 600 °C to 1000 °C. The following conclusions were obtained: 1. (i) For a given methane concentration, the substrate temperature range leading to diamond formation is very narrow. 2. (ii) The average temperature of diamond formation decreases when the methane concentration increases.

The Raman characterisation of crystalline diamond films prepared by the plasma torch system and diamond-like carbon (DLC) deposited using the ion-beam-assisted DC magnetron technique is presented. The spectra are first discussed in terms of quality of diamond samples and are used to define the best set of synthesis parameters. The broadening of diamond line is discussed in terms of a distribution of stresses and of crystallite size effect. The DLC spectra are discussed as a function of the H content and of the density of the films, their second-order spectra have been investigated. Because of the resonant nature of the 1570 cm −1 component and the strong second-order band at about 3150 cm −1 , the presence of graphite-like entities is discussed.

A noble basic proton conducting polymer (so-called proton-vacancy conducting polymer) based on a solvating polymer (PEO), a sulfamide-type salt and a doping agent (guanidine, proton-vacancy inducer) is presented. Three eutectics and three intermediate crystalline compounds are found in the phase diagram established for the P(EO) n NH 2 SO 2 NH 2 system (where n = O/S stands as the ratio of monomer units per sulfamide molecule). Experimental data obtained for two different doping levels (represented as the ratio N/H of guanidine molecules added per proton extracted) indicate that conductivity is raised as more protons are extracted from sulfamide. At room temperature one of the doped samples exhibits 10 −5 Ω −1 cm −1 . A conduction mechanism is proposed. A new vibrational band, ir inactive and probably due to complexation effects, is seen at about 896 cm −1 in the Raman spectra of some of the complexes studied in the absence of base. The NH 2 stretching Raman bands characteristic of the analysed complexes are evidenced.

Micro-Raman spectra of thin films of various carbonaceous compounds are presented. The relative Raman scattering cross sections of films of graphite and diamond are revised (a factor of two is found instead of 50 as in literature). Second order and third order Raman spectra of graphite and diamond like films are presented and discussed in terms of resonance Raman effect. Study of carbonaceous thin films under electric field is in progress.

The commensurate-incommensurate transition of PbO, lead monoxide, was confirmed by small anomalies observed below 200 K on both heat capacity curves and Raman spectra. For Pb 0.94 Ti 0.06 O 1.06 , no transition has been detected using neutron diffraction, heat capacity measurements and Raman spectroscopy. Structural refinements show new interlayer Pb-O and Ti-O bonds. Extra oxygen atoms are located in the interlayers of the host lattice of the PbO structure; they break the interactions between the electronic lone pairs of the Pb 2+ ions and the transition no longer occurs.

Raman spectra for 4-methoxybenzylidene-4′-butylaniline (MBBA) in its nematic liquid crystal phase and in all its solid phases were measured in the frequency range 5–1700 cm−1. Clear modifications have been observed at the phase transitions, not only in the low frequency range, but also in the internal vibrational modes. Different stages of the structural order in the successive polymorphic modifications are evidenced. In addition, the changes which occur in the intramolecular part of the spectra reveal that phase transitions directly affect the butyl tail while others are related to conformational modifications of the core of the molecule.

The IR and Raman spectra at 20°C of PbMg 1 3 Nb 2 3 O 3 are reported and an assignment of the observed frequencies taking into account the different types of chemical bonds is proposed. The evolution of the spectra with temperature is analyzed. The Raman spectra are sensitive to a small modification of the short-range order i n the B site of the perovskite obtained by substitution of NbV by WVI or PbII by LaIII.

This paper proposes a novel HW/SW co-simulation approach that minimizes the impact on software designers. We propose a SystemC-based system that enables the software team to test their software with their own tools and environment using an accurate simulated ASIC (Application Specific Integrated Circuit) model. The solution presented here enables a smooth and early ASIC and SW integration, which reduces the project development time and improves the ASIC design quality (i. e., SW engineers can help in the ASIC verification and ASIC engineers can help in the SW development). In this solution, the real and full software (i. e., multi-threaded application) runs in its native environment with minimal changes and interfaces with a simulated ASIC model using sockets. We have tested this approach on a pilot-project, which has demonstrated the feasibility of this co-development methodology.

Raman spectroscopy was applied to monitor the growth of diamond in different plasma-assisted chemical vapour deposition reactors. A gated, multichannel detection system was used to discriminate against the high level of background radiation produced by the plasma and the hot substrate. As a result, Raman spectra could be taken during diamond growth without interruption of the process. The ability to detect and distinguish between diamond and non-diamond phases during film growth is demonstrated. A sufficient signal-to-noise ratio in the spectra was achieved for stress formation to be observed. Copyright © 2003 John Wiley & Sons, Ltd.

The study of the behaviour of fullerenes under pressure has shown that under strong non-hydrostatic compressions they reproducibly transform above 15–20 GPa from a black soot to transparent hard pellets. X-ray analysis shows the existence of polycrystalline diamond of grain size smaller than 1000 A. Further transmission electron microscopy characterization shows that these small cubic diamond crystals are embedded in an amorphous matrix whose diffraction patterns suggest a disordered tetrahedral coordination for the carbon atoms. Finally Raman microspectroscopy studies indeed show the existence of the characteristic 1330 cm−1 cubic diamond peak in all our samples, together with a broad band at 1450 cm−1, which we tentatively attribute to the amorphous phase.

We present the Raman characterization of transformed fullerene samples obtained by applying high (∼20 GPa) nonhydrostatic pressures on C 60 or C 60 -C 70 powders. Only two clear features are observed. The first is a peak at 1330 cm -1 , signature of the existence of cubic diamond. The second is a broadband of unknown origin centered at approximately 1450 cm -1 . These results confirm previous crystallographic analysis that showed that our samples consist of polycrystalline diamond embedded in an amorphous matrix

Non-hydrogenated diamond-like carbon films have been prepared by Dual Ion Beam Sputtering and Ion Beam Assisted Magnetron. The assistance parameters -ion energy, ion mass, ion flux/atom flux-have been systematically varied and their effect on the microsaucture of the films studied. The films have been characterised by Rutherford Backscattering Spectroscopy (RBS), High Resolution Transmission Electron Microscopy (HRTEM), Electron Energy Loss Spectroscopy (EELS), Positron Annihilation Spectroscopy (PAS), and Raman Spectroscopy (RS). RBS and PAS results showed that the density and the degree of disorder of the films go through a maximum with ion energy, and that the void concentration goes through a minimum. EELS and RS show that the films are mostly sp 2 bonded, with a maximum concentration of sp 3 bonding of about 16% for the largest values of density. The evolution of density with ion flux and energy is consistent with a combined effect of atomic displacements in the film leading to densification, and with damage buildup leading to progressive graphitisation as the energy is increased

Several experimental and theoretical studies [1,2,3] of Surface Plasmons Enhanced Raman Scattering (SPERS) in Kretschmann geometry (prism-metal-dielectric stacks) have demonstrated that it is possible to use surface plasmons (SP) to enhance Raman scattering from molecules adsorbed on a metal film. The enhancement process originates from two contributions: First, excitation of SP at pump frequency (ωi) and second, excitation of SP at Stokes frequency (ωs). To get the strongest Raman signal, scattered light must be detected on the prism side [3]. Indeed, the collected light comes from the outcoupling of SP at the Stokes frequency. In an experiment of SPERS, the Raman intensity depends on the distance of the active molecules to the metal surface [2]. Moreover, it has been suggested [3] that the thickness of the metal film deposited onto the prism should also be taken into account if one wants to improve the limit of detection.

A complete vibrational study of crystalline V2O5 was performed. Polarized Raman spectra at 300 and 100 K on a single crystal and i.r. absorption spectra on powder samples have been recorded. An assignment in terms of factor group symmetry species is given. A normal coordinate analysis using a complete force field has been performed. All the normal modes of vibration have been described in terms of potential energy distribution and in terms of cartesian displacements. Some modes characteristic of specific bonds have been discussed. Finally some low frequency modes have been found to derive, at a first approximation, from acoustic modes and some dispersion curves are derived from the simple model of the linear chain.

The thermal behaviours of LiRbSO4 and LiCsSO4 have been investigated in the temperature range 10 to 300 K. Besides the previously reported phase transition at 201 K in LiCsSO4, new anomalies were observed on both compounds from d.s.c. studies and heat-capacity measurements. They occur around 260 K and are very dependent on the crystal size and the thermal history of the studied sample. Such behaviour is compared with that previously observed on LiKSO4.

The purpose of this work was to ascertain the validity of the conclusions drawn from i.r. and Raman studies relative to the structure of the V 2 O 5 frameworkin V 2 O 5 · n H 2 O xerogels with n = 0.3, 0.6, 1.4. Three structural models have been considered: (i) one 2D independent V 2 O 5 layer identical to those of crystalline V 2 O 5 (infinite in two dimensions), (ii) the same 2D layer as (i) in which all the vanadium atoms are coordinated by water molecules, (iii) one 2D fibril (infinite in one dimension and made of five V 2 O 5 units in the other). The force fields used in those models were based on that of crystalline V 2 O 5 . The agreement between calculated and observed frequencies confirms that the model of an independent 2D layer cannot be representative of the n = 0.3 compound, and that interlayer forces exist as in the crystal, while model (ii) of the hydrated layer is valid for the n ⩾ 0.6 composition. The Cartesian displacements for the different normal modes calculated in the three models have been obtained and some of these which are closely related to the structural modifications are represented.

Raman spectra of single crystals of NH3SO3 were recorded for the B1g and B3g polarization in the range 10–500 cm−1 for the temperature range 10–360 K and for zz, zy and zχ polarizations in the range 2500–3300 cm−1 at 77 and 300 K. Neutron diffraction data on the polycrystalline sample at 4 and 77 K were obtained in order to study the structural variation with temperature. Potential energy calculations made using atom-atom potentials show that torsional mode broadening is not caused by hot-band transitions. The ful width at half maximum intensity of the torsional mode was accounted for in terms of the reorientational motion of the NH3 rotor and the pure vibrational dephasing (PVD). At 300 K the reorientational motion contributes about 2 cm−1. The PVD broadening was calculated on the basis of cubic coupling between the torsional and hydrogen bond stretching modes following a semi-classical model. Its contribution at 300 K was estimated to be 25 cm−1.

A complete vibrational study of xerogels of vanadium oxide corresponding to the formula V/sub 2/O/sub 5/ x nH/sub 2/O with n = 1.6, 1.2, 0.6, 0.4, and 0.3, was performed. Raman and infrared spectra of powder and oriented films of the samples have been recorded at 100 and 300 K. It has been possible to verify the existence of two different structures. For n = 0.3, V/sub 2/O/sub 5/ layers are connected as in the crystal through V=O-V bonds, each water molecule trapped into cavities being linked by its two hydrogen atoms to the oxygen lattice, the interlayer distance (b parameter) should be close to that of the crystal. For n = 0.6, the V/sub 2/O/sub 5/ layers are not connected as in the crystal through the long V-O bonds, but the vanadium atoms are coordinated to H/sub 2/O molecule by V-OH/sub 2/ bonds. For 0.6 < n < 1.4 three kinds of water molecules are likely present. Finally, it is shown that the conclusions are consistent with the literature structural models proposed from diffraction methods. 18 references, 9 figures, 2 tables.

Three phase transitions were found in LiNH 4 SO 4 crystals by heat capacity measurements between 10 and 310 K. One is first order at T tr = 288.7 K and the two others are of high order over a large temperature range with maximum C p,m anomalies around 248 and 37 K respectively. Raman spectroscopic studies down to 10 K show that both NH + 4 rotations and Li + translations are involved in the phase transition around 248 K. The mechanism of the transition at 37 K is essentially governed by reorientational motions of the ammonium group. All these results are discussed in the light of numerous studies previously reported on the behaviour of LiNH 4 SO 4 crystals.