Mit Hilfe radiokristallographischer und thermograviometrischer Analyse sowie IR‐ Absorptionsrness... more Mit Hilfe radiokristallographischer und thermograviometrischer Analyse sowie IR‐ Absorptionsrnessungen werden die beiden Clatlirate und jede Phase der Abbauetappen untersucht.
Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1984
Infrared and Raman spectra (1800–200 cm–1) of methyl viologen (1,1′-dimethyl-4,4′-bipyridyl dicat... more Infrared and Raman spectra (1800–200 cm–1) of methyl viologen (1,1′-dimethyl-4,4′-bipyridyl dication or MV2+)([1H8] and [2H8] derivatives) have been recorded for the chloride, iodide and palladate salts and for the intercalated compounds of formula M0.84 PS3–(MV)0.16(with M = Mn and Cd), FePS3–(MV)0.15 and Zn0.71 PS3–(MV)0.29. Complete assignments have been proposed for all these species. The methyl viologen appears to be intercalated in its dicationic form and is weakly interacting with the host lattice. In the ZnPS3 system the MV2+ pyridyl rings are twisted while in MnPS3, CdPS3, and FePS3 the cation rings are coplanar and parallel to the sulphur layers. From these results, a model of packing of MV2+ in the MPS3 host lattices has been established which accounts for the different intercalation rates. Finally, the reduced product, MV˙+, has been studied in both the chloride salt and the CdPS3 intercalation compound; in the latter case the radical cation behaves as though diluted and trapped inside an inert matrix, demonstrating unexpected stability.
Pulsed laser ablation has attracted great attention over the past few years as promising techniqu... more Pulsed laser ablation has attracted great attention over the past few years as promising technique for depositing thin films. A large variety of successful experimental results were obtained in this field, including the growth of high- temperature superconducting films, ferroelectric films, oxides, semiconductors, diamonds, etc. One of the main advantages of this technology is the simplicity of the experimental set-up. In a common configuration, the laser- generated flux of particles is collected on a planar substrate positioned parallel to the irradiated surface. Several modifications, like simultaneous generation of two plumes from different targets (double ablation), were proposed. Different lasers (e.g. KrF with (lambda) equals 248 nm, Nd-YAG with (lambda) equals 532 nm, etc.) with energy density 2 - 10 J/cm2 were used in the ablation experiments both in vacuum and into diluted ambient gas (pressure up to 750 mTorr). Monte Carlo simulation was found to be a successful technique for theoretical investigations of the laser ablation processes. This method has allowed us to investigate the influence of elastic collisions and chemical reactions in the laser ablated plume on the angular characteristics of the flow. The results of the simulation show that elastic collisions give rise to focusing of particles towards the surface normal and to the redirection of the velocities of the more energetic particles in the direction close to the surface normal. The chemical reactions are found to influence the angular distributions in the way opposite to the one of elastic collisions. The reaction heat contributes to the energy of particles and the velocity distributions are affected by reactions. As result of these processes, the angular distributions are broadened from the surface normal. Additional collisions with the particles of the ambient gas were shown to influence the composition and uniformity of thin films. The study of these processes is of a particular interest for the developing of pulsed laser deposition (PLD) technique.
A large field of applications as microelectronics, micromechanics and optics needs to overcome th... more A large field of applications as microelectronics, micromechanics and optics needs to overcome the deposition of various materials showing dielectric, superconducting, piezoelecinc properties under thin film form. Numerous methods were developed as Chemical Vapour Deposition, Sputtering, Thermal Evaporation. Since the early 1980's, a new process based on laser ablation is developed.1 The Pulsed Laser Deposition (P.L.D) method is based on the laser evaporation of a target and the subsequent deposition of the ablation plume on a substrate (see fig. 1). A wide variety of materials was successfully deposited in thin film form by this method. Recently, Nb5Te4 thin films were realized for the first time by using P.L.D process.3 The Nb5Te4 compound presents strong anisotropic properties and finds applications in microelectronics (1D conductors) and micromechanics (solid lubricant). These first results3 shown the key roles played by the laser fluence and the substrate temperature on the film composition and crystallisation. For example, increasing the laser fluence decreases the interreticular distance observed by X-ray diffraction and increases the Te/Nb ratio. This shows the importance of kinetic parameters of the laser-induced plume on the crystallisation process. In order to understand the influence of the laser parameters on the film formation, it is necessary to study the ablation process and the expansion of the ablation cloud.
Physical Concepts of Materials for Novel Optoelectronic Device Applications I: Materials Growth and Characterization, 1991
ABSTRACT Highly anisotropic polytellurides MTe with M Zr and x 1. 5 to 5 have been synthetized un... more ABSTRACT Highly anisotropic polytellurides MTe with M Zr and x 1. 5 to 5 have been synthetized under thin film form for the first time. Preferential orientations of these films with respect to the substrate surface are evidenced and tentatively correlated to the anisotropy of the optical or conduction properties.
Abstract The layered MPS 3 (M= Mn, Fe, Ni, Zn, Cd) react with a number of organometallic sandwich... more Abstract The layered MPS 3 (M= Mn, Fe, Ni, Zn, Cd) react with a number of organometallic sandwich compounds, forming the related intercalation compounds. The case of CdPS 3 is studied in detail; intercalation may be obtained using either neutral or cationic ...
Laser Processing: Surface Treatment and Film Deposition, 1996
Niobium telluride thin films were produced by excimer laser vaporisation of NbTe2 bulk targets an... more Niobium telluride thin films were produced by excimer laser vaporisation of NbTe2 bulk targets and deposition of the ablation plume on heated silicon substrates. Precise control of the laser energy density and of the substrate temperature leads to good quality, well-crystallized thin films. For a specific couple of fluence and temperature, films were crystallized in the Nb5Te4 phase. In order to characterize the influence of laser parameters, analyse of the ablation plume by optical spectroscopy was performed using an Optical Multichanel Analyzer.
ABSTRACTPulsed laser deposition (PLD ) is known for its capacity to reproduce a target compositio... more ABSTRACTPulsed laser deposition (PLD ) is known for its capacity to reproduce a target composition on a substrate. We have used this deposition technique to produce thin films of transition metal chalcogenides. However, the deposits were always deficient in Te relative to the starting material ( composed by a refractory metal ( niobium ) and a chalcogene ( tellurium ) ). Variations of the interreticular distances have been observed with respect to fluence and substrate temperature. We show that spatial composition of the films is determined by a degree of crystallinity of deposit and by the reaction of formation of Te2 molecule within laser induced plume Two kinds of deposits have been obtained : Nb5Te4-type thin films which have a one-dimensional structure and NbTe2-type thin films which have a two-dimensional structure. While NbTe2 films have been realized by sputtering, it is the first time that Nb5Te4 films have been deposited.
We may not be able to make you love reading, but synchrotron radiation in chemistry and biology i... more We may not be able to make you love reading, but synchrotron radiation in chemistry and biology iii will lead you to love reading starting from now. Book is the window to open the new world. The world that you want is in the better stage and level. World will always guide you to even the prestige stage of the life. You know, this is some of how reading will give you the kindness. In this case, more books you read more knowledge you know, but it can mean also the bore is full.
The infrared, polarized Raman, and inelastic neutron scattering spectra (650-10 cm-') of M&&&PS, ... more The infrared, polarized Raman, and inelastic neutron scattering spectra (650-10 cm-') of M&&&PS, and M~rsAg:.,& compounds, where M " = Mn Cd, have been recorded and compared , with those of the related M"P& derivatives. It is shown that all these new metal-substituted systems maintain a bidimensional structure (CdC& type) consisting of P& entities, monometallic M"S6, and bimetallic (M')& octahedra. The copper derivatives are disordered because of a random distribution of Cu& entities; meanwhile, the silver-containing lattices seem ordered. The vibrational modes assigned to translational motions of Cur and Ag' cations have been clearly identified in the low-frequency region (Y < 75 cm-'). Finally, the magnetic and vibrational properties of the M~,,&I~.~~PS~ host lattice intercalated with Co(C,H& have been investigated; this definitely confirms the layered character of this new family of compounds. Q 1988 Academic Press, Inc.
Infrared transmission spectra (600–50 cm−1) and Raman spectra (800–10 cm−1) of the layered semico... more Infrared transmission spectra (600–50 cm−1) and Raman spectra (800–10 cm−1) of the layered semiconducting transition metal sulphides HfS3 and NiPS3 and of their intercalates LixHfS3, NaxHfS3 (0<x&45ROM9;3) and LixNiPS3 (0<x&45ROM9;1.5) are compared. In agreement with previous studies, it is concluded that alkali metal ions are accom-modated in both tetrahedral and octahedral sulphur environments in the former case and only in octahedral surroundings in the latter. The wavenumbers of the characteristic intercalation modes are discussed and compared with literature data; simple local symmetry arguments can then explain the very weak Raman intensity of the modes in LixNiPS3 compounds.
Abstract Infrared and Raman spectra (10–3100 cm −1 ) of the layered ZnPSs compound and of interca... more Abstract Infrared and Raman spectra (10–3100 cm −1 ) of the layered ZnPSs compound and of intercalates with [ Co ( η 5 − C 5 H 5 ) 2 + ] and [ Cr ( η 6 − C 6 H 6 ) 2 + ] cations in the polycrystalline state have been recorded 300–10 K temperature range. A complete assignment of the spectra is proposed in terms of PSs group motions, Zn 2+ ion translations and [ Co ( η 5 − C 5 H 5 ) 2 + ] or [ Cr ( η 6 − C 6 H 6 ) 2 + ] internal vibrations. New low frequency for the [Co(η 5 -C 5 H 5 ) 2 + ] intercalate at low temperature are assigned to librational and torsional modes of C 5 H 5 rings. Moreover, the preresonance Raman spectra of this intercalate show a selective enhancement for the metal-ligand vibrations when the charge transfer band of the cobalticenium is approached. One concludes that guest molecules are intercalated under their cationic form, are weakly interacting with the host lattice and seem to be dynamically disordered at room temperature.
The first results obtained with the prototype system at the synchrotron beamline ID03 at ESRF are... more The first results obtained with the prototype system at the synchrotron beamline ID03 at ESRF are presented and illustrate the possibility to detect an element-specific contrast and to perform nanoscale x-ray absorption spectroscopy experiments at the Zn K and W L 3 absorption edges in mixed zinc oxide-zinc tungstate thin films.
A versatile procedure of sputter deposition, well-adapted for getting a large range of Te/M ratio... more A versatile procedure of sputter deposition, well-adapted for getting a large range of Te/M ratios (with M = Zr or Nb), has led to the synthesis of several highly anisotropic zirconium and niobium polytellurides in thin film form. Upon tuning the two key parameters of the process, i.e., the Te percentage in the target and the substrate temperature during the deposition, preparation of systems ranging from ZrTe0.72 to ZrTe6.7, on the one hand, and from NbTe1.28 to NbTe7.84, on the other, has been achieved. Besides their amorphous or crystalline (with or without preferential orientations) behavior and their relationship to known structural types, the most striking feature of these films is their large departure from the stoichiometry of the bulk MTex reference compounds. This peculiarity, together with the possible changes of composition under annealing, are described and interpreted in terms of variable amounts of Te and M atoms trapped or intercalated within the parent structures.
We present XAFS (K-edge) studies of the local atomic structure around the Nb and Te ions in niobi... more We present XAFS (K-edge) studies of the local atomic structure around the Nb and Te ions in niobium tellurides (NbTe.,,, Nb3Te 4 and NbTe4) in comparison with ZrTe 2. Using a multi-shell best-fit analysis procedure, we have reconstructed local environments of the Nb and Te ions and compared them with the existing structural models. We found that at the Nb K-edge the XAFS data of NbTe4 are extremely sensitive to metal clustering and to the subsequent departure from the average crystallographic positions. Moreover~,at Te K-edge the XAFS data allowed us to distinguish the different type of Te-Te bonds, for instance: the dimer (Tc-Te: ..) A) and the squares (Te-Te: 3.3 ,a,) in NbTe4, the interlayer and intralayer (Te~Te: 2.9=4.0 ,A) in NbTe:, through their Debye-Waller characteristics, in addition, a comparative analysis of Debye-Waller factors obtained in the different coordination shells (Te-Te, Te-Nb, Nb-Te and Nb-Nb) shows an evidence of correlation in the vibrational motion.
Mit Hilfe radiokristallographischer und thermograviometrischer Analyse sowie IR‐ Absorptionsrness... more Mit Hilfe radiokristallographischer und thermograviometrischer Analyse sowie IR‐ Absorptionsrnessungen werden die beiden Clatlirate und jede Phase der Abbauetappen untersucht.
Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1984
Infrared and Raman spectra (1800–200 cm–1) of methyl viologen (1,1′-dimethyl-4,4′-bipyridyl dicat... more Infrared and Raman spectra (1800–200 cm–1) of methyl viologen (1,1′-dimethyl-4,4′-bipyridyl dication or MV2+)([1H8] and [2H8] derivatives) have been recorded for the chloride, iodide and palladate salts and for the intercalated compounds of formula M0.84 PS3–(MV)0.16(with M = Mn and Cd), FePS3–(MV)0.15 and Zn0.71 PS3–(MV)0.29. Complete assignments have been proposed for all these species. The methyl viologen appears to be intercalated in its dicationic form and is weakly interacting with the host lattice. In the ZnPS3 system the MV2+ pyridyl rings are twisted while in MnPS3, CdPS3, and FePS3 the cation rings are coplanar and parallel to the sulphur layers. From these results, a model of packing of MV2+ in the MPS3 host lattices has been established which accounts for the different intercalation rates. Finally, the reduced product, MV˙+, has been studied in both the chloride salt and the CdPS3 intercalation compound; in the latter case the radical cation behaves as though diluted and trapped inside an inert matrix, demonstrating unexpected stability.
Pulsed laser ablation has attracted great attention over the past few years as promising techniqu... more Pulsed laser ablation has attracted great attention over the past few years as promising technique for depositing thin films. A large variety of successful experimental results were obtained in this field, including the growth of high- temperature superconducting films, ferroelectric films, oxides, semiconductors, diamonds, etc. One of the main advantages of this technology is the simplicity of the experimental set-up. In a common configuration, the laser- generated flux of particles is collected on a planar substrate positioned parallel to the irradiated surface. Several modifications, like simultaneous generation of two plumes from different targets (double ablation), were proposed. Different lasers (e.g. KrF with (lambda) equals 248 nm, Nd-YAG with (lambda) equals 532 nm, etc.) with energy density 2 - 10 J/cm2 were used in the ablation experiments both in vacuum and into diluted ambient gas (pressure up to 750 mTorr). Monte Carlo simulation was found to be a successful technique for theoretical investigations of the laser ablation processes. This method has allowed us to investigate the influence of elastic collisions and chemical reactions in the laser ablated plume on the angular characteristics of the flow. The results of the simulation show that elastic collisions give rise to focusing of particles towards the surface normal and to the redirection of the velocities of the more energetic particles in the direction close to the surface normal. The chemical reactions are found to influence the angular distributions in the way opposite to the one of elastic collisions. The reaction heat contributes to the energy of particles and the velocity distributions are affected by reactions. As result of these processes, the angular distributions are broadened from the surface normal. Additional collisions with the particles of the ambient gas were shown to influence the composition and uniformity of thin films. The study of these processes is of a particular interest for the developing of pulsed laser deposition (PLD) technique.
A large field of applications as microelectronics, micromechanics and optics needs to overcome th... more A large field of applications as microelectronics, micromechanics and optics needs to overcome the deposition of various materials showing dielectric, superconducting, piezoelecinc properties under thin film form. Numerous methods were developed as Chemical Vapour Deposition, Sputtering, Thermal Evaporation. Since the early 1980's, a new process based on laser ablation is developed.1 The Pulsed Laser Deposition (P.L.D) method is based on the laser evaporation of a target and the subsequent deposition of the ablation plume on a substrate (see fig. 1). A wide variety of materials was successfully deposited in thin film form by this method. Recently, Nb5Te4 thin films were realized for the first time by using P.L.D process.3 The Nb5Te4 compound presents strong anisotropic properties and finds applications in microelectronics (1D conductors) and micromechanics (solid lubricant). These first results3 shown the key roles played by the laser fluence and the substrate temperature on the film composition and crystallisation. For example, increasing the laser fluence decreases the interreticular distance observed by X-ray diffraction and increases the Te/Nb ratio. This shows the importance of kinetic parameters of the laser-induced plume on the crystallisation process. In order to understand the influence of the laser parameters on the film formation, it is necessary to study the ablation process and the expansion of the ablation cloud.
Physical Concepts of Materials for Novel Optoelectronic Device Applications I: Materials Growth and Characterization, 1991
ABSTRACT Highly anisotropic polytellurides MTe with M Zr and x 1. 5 to 5 have been synthetized un... more ABSTRACT Highly anisotropic polytellurides MTe with M Zr and x 1. 5 to 5 have been synthetized under thin film form for the first time. Preferential orientations of these films with respect to the substrate surface are evidenced and tentatively correlated to the anisotropy of the optical or conduction properties.
Abstract The layered MPS 3 (M= Mn, Fe, Ni, Zn, Cd) react with a number of organometallic sandwich... more Abstract The layered MPS 3 (M= Mn, Fe, Ni, Zn, Cd) react with a number of organometallic sandwich compounds, forming the related intercalation compounds. The case of CdPS 3 is studied in detail; intercalation may be obtained using either neutral or cationic ...
Laser Processing: Surface Treatment and Film Deposition, 1996
Niobium telluride thin films were produced by excimer laser vaporisation of NbTe2 bulk targets an... more Niobium telluride thin films were produced by excimer laser vaporisation of NbTe2 bulk targets and deposition of the ablation plume on heated silicon substrates. Precise control of the laser energy density and of the substrate temperature leads to good quality, well-crystallized thin films. For a specific couple of fluence and temperature, films were crystallized in the Nb5Te4 phase. In order to characterize the influence of laser parameters, analyse of the ablation plume by optical spectroscopy was performed using an Optical Multichanel Analyzer.
ABSTRACTPulsed laser deposition (PLD ) is known for its capacity to reproduce a target compositio... more ABSTRACTPulsed laser deposition (PLD ) is known for its capacity to reproduce a target composition on a substrate. We have used this deposition technique to produce thin films of transition metal chalcogenides. However, the deposits were always deficient in Te relative to the starting material ( composed by a refractory metal ( niobium ) and a chalcogene ( tellurium ) ). Variations of the interreticular distances have been observed with respect to fluence and substrate temperature. We show that spatial composition of the films is determined by a degree of crystallinity of deposit and by the reaction of formation of Te2 molecule within laser induced plume Two kinds of deposits have been obtained : Nb5Te4-type thin films which have a one-dimensional structure and NbTe2-type thin films which have a two-dimensional structure. While NbTe2 films have been realized by sputtering, it is the first time that Nb5Te4 films have been deposited.
We may not be able to make you love reading, but synchrotron radiation in chemistry and biology i... more We may not be able to make you love reading, but synchrotron radiation in chemistry and biology iii will lead you to love reading starting from now. Book is the window to open the new world. The world that you want is in the better stage and level. World will always guide you to even the prestige stage of the life. You know, this is some of how reading will give you the kindness. In this case, more books you read more knowledge you know, but it can mean also the bore is full.
The infrared, polarized Raman, and inelastic neutron scattering spectra (650-10 cm-') of M&&&PS, ... more The infrared, polarized Raman, and inelastic neutron scattering spectra (650-10 cm-') of M&&&PS, and M~rsAg:.,& compounds, where M " = Mn Cd, have been recorded and compared , with those of the related M"P& derivatives. It is shown that all these new metal-substituted systems maintain a bidimensional structure (CdC& type) consisting of P& entities, monometallic M"S6, and bimetallic (M')& octahedra. The copper derivatives are disordered because of a random distribution of Cu& entities; meanwhile, the silver-containing lattices seem ordered. The vibrational modes assigned to translational motions of Cur and Ag' cations have been clearly identified in the low-frequency region (Y < 75 cm-'). Finally, the magnetic and vibrational properties of the M~,,&I~.~~PS~ host lattice intercalated with Co(C,H& have been investigated; this definitely confirms the layered character of this new family of compounds. Q 1988 Academic Press, Inc.
Infrared transmission spectra (600–50 cm−1) and Raman spectra (800–10 cm−1) of the layered semico... more Infrared transmission spectra (600–50 cm−1) and Raman spectra (800–10 cm−1) of the layered semiconducting transition metal sulphides HfS3 and NiPS3 and of their intercalates LixHfS3, NaxHfS3 (0<x&45ROM9;3) and LixNiPS3 (0<x&45ROM9;1.5) are compared. In agreement with previous studies, it is concluded that alkali metal ions are accom-modated in both tetrahedral and octahedral sulphur environments in the former case and only in octahedral surroundings in the latter. The wavenumbers of the characteristic intercalation modes are discussed and compared with literature data; simple local symmetry arguments can then explain the very weak Raman intensity of the modes in LixNiPS3 compounds.
Abstract Infrared and Raman spectra (10–3100 cm −1 ) of the layered ZnPSs compound and of interca... more Abstract Infrared and Raman spectra (10–3100 cm −1 ) of the layered ZnPSs compound and of intercalates with [ Co ( η 5 − C 5 H 5 ) 2 + ] and [ Cr ( η 6 − C 6 H 6 ) 2 + ] cations in the polycrystalline state have been recorded 300–10 K temperature range. A complete assignment of the spectra is proposed in terms of PSs group motions, Zn 2+ ion translations and [ Co ( η 5 − C 5 H 5 ) 2 + ] or [ Cr ( η 6 − C 6 H 6 ) 2 + ] internal vibrations. New low frequency for the [Co(η 5 -C 5 H 5 ) 2 + ] intercalate at low temperature are assigned to librational and torsional modes of C 5 H 5 rings. Moreover, the preresonance Raman spectra of this intercalate show a selective enhancement for the metal-ligand vibrations when the charge transfer band of the cobalticenium is approached. One concludes that guest molecules are intercalated under their cationic form, are weakly interacting with the host lattice and seem to be dynamically disordered at room temperature.
The first results obtained with the prototype system at the synchrotron beamline ID03 at ESRF are... more The first results obtained with the prototype system at the synchrotron beamline ID03 at ESRF are presented and illustrate the possibility to detect an element-specific contrast and to perform nanoscale x-ray absorption spectroscopy experiments at the Zn K and W L 3 absorption edges in mixed zinc oxide-zinc tungstate thin films.
A versatile procedure of sputter deposition, well-adapted for getting a large range of Te/M ratio... more A versatile procedure of sputter deposition, well-adapted for getting a large range of Te/M ratios (with M = Zr or Nb), has led to the synthesis of several highly anisotropic zirconium and niobium polytellurides in thin film form. Upon tuning the two key parameters of the process, i.e., the Te percentage in the target and the substrate temperature during the deposition, preparation of systems ranging from ZrTe0.72 to ZrTe6.7, on the one hand, and from NbTe1.28 to NbTe7.84, on the other, has been achieved. Besides their amorphous or crystalline (with or without preferential orientations) behavior and their relationship to known structural types, the most striking feature of these films is their large departure from the stoichiometry of the bulk MTex reference compounds. This peculiarity, together with the possible changes of composition under annealing, are described and interpreted in terms of variable amounts of Te and M atoms trapped or intercalated within the parent structures.
We present XAFS (K-edge) studies of the local atomic structure around the Nb and Te ions in niobi... more We present XAFS (K-edge) studies of the local atomic structure around the Nb and Te ions in niobium tellurides (NbTe.,,, Nb3Te 4 and NbTe4) in comparison with ZrTe 2. Using a multi-shell best-fit analysis procedure, we have reconstructed local environments of the Nb and Te ions and compared them with the existing structural models. We found that at the Nb K-edge the XAFS data of NbTe4 are extremely sensitive to metal clustering and to the subsequent departure from the average crystallographic positions. Moreover~,at Te K-edge the XAFS data allowed us to distinguish the different type of Te-Te bonds, for instance: the dimer (Tc-Te: ..) A) and the squares (Te-Te: 3.3 ,a,) in NbTe4, the interlayer and intralayer (Te~Te: 2.9=4.0 ,A) in NbTe:, through their Debye-Waller characteristics, in addition, a comparative analysis of Debye-Waller factors obtained in the different coordination shells (Te-Te, Te-Nb, Nb-Te and Nb-Nb) shows an evidence of correlation in the vibrational motion.
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