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Metal matrix composites have a diverse range of applications. We have probed local structural modifications taking fullerene C70 as a model matrix material. In this study, thin films of fullerene C70 were grown on polished silicon and quartz substrates by resistive heating of fullerene C70. In order to understand local structural changes, these semi-crystalline films were irradiated with 120 keV N+ ions at different fluences ranging from 1 × 1013 to 3 × 1016 ions.cm−2. Microscopic analysis shows an increase in topological roughness up to a fluence of 1 × 1015 ions.cm−2 and then a decrease. The size of the particles decreases with increase in the fluence. Various spectroscopic analyses conducted on differently irradiated fullerene C70 films show that the bandgap decreases with the increase in the fluence which will increase the conductivity of the irradiated thin films. These results are proved by I-V measurements showing the decrease in the resistivity at higher fluences. Therefore, this characteristic trait makes fullerene C70 to be used as a prominent matrix component in the composites. Raman spectroscopic investigations reveal that C70 is completely transformed into amorphous carbon at a fluence of 3 × 1016 ions.cm−2. Different vibrational modes in FT-IR are also reported in the present work.

A bi-functional nanocomposite thin film containing Ag nanoparticles embedded in fullerene C 70 is synthesized by thermal co-evaporation technique. Tuning of plasmonic resonance of Ag-C 70 nanocomposite is obtained by annealing the nanocomposite thin film at different temperatures from 80 to 300 °C for 30 min. The optical and structural properties of nanocomposite thin film with respect to high temperature are studied by UV–visible absorption spectroscopy and X-ray diffraction. Transmission electron microscopy is performed to investigate the temperature dependent size evolution of Ag nanoparticles in fullerene C 70 matrix. Growth of Ag nanoparticles is observed with increasing temperature above 200 °C due to enhanced diffusion of Ag in fullerene C 70 and Ostwald ripening. The optical and structural properties of metal-fullerene nanocomposite is not significantly affected upto a temperature of 150 °C, after that a progressive blue shift of ~ 27 nm in SPR wavelength is observed with increasing temperature. The tuning of SPR is ascribed to the thermal induced structural transformation of fullerene C 70 matrix into amorphous carbon and also to mutual polarization of the particles.

Au-C70 nanocomposite thin films are deposited using thermal co-evaporation technique. Low atomic concentration of Au (∼3%) are used to avoid any deterioration of the properties of fullerene C70 when used with Au. These thin films are annealed in inert atmosphere at different temperatures for 30 min in order to promote the formation of nanocomposite material. Both the Au nanoparticles and fullerene C70 matrix are evolved by thermal treatment. Spherical shaped Au nanoparticles with a diameter of 3.8 ± 0.1 nm are clearly observed in the TEM images at 350 °C. The characteristic D and G bands of amorphous carbon are evidenced by Raman scattering spectroscopy in the film annealed at 350 °C. The surface plasmon resonance (SPR) absorption band of Au nanoparticles in carbon is obtained at 565 nm after treatment at 300 °C and it is blue shifted to 549 nm for the sample annealed at 350 °C.

International audience; Microstructural and surface morphological studies of Co (2.5%) doped ZnS thin films deposited at different substrate temperatures (TS) of 200, 400 and 600 °C by means of pulsed laser deposition are presented. The deposited films are in wurtzite-hexagonal crystal structure as confirmed by X-ray diffraction and Raman spectroscopy techniques. The films deposited at higher TS show columnar morphology, as evidence by transmission electron microscopy measurements. Images of the surface topography have been taken by atomic force microscopy (AFM) for the film deposited at different TS. The film deposited at TS of 200 °C shows cone-like structures while deposited at TS of 400 and 600 °C show columnar structures. A fractal analysis has been performed on AFM images to understand the microstructure and surface morphology of thin film at different TS. Fractal analysis also reveals the morphological changes in the film with increasing TS. The observed ferromagnetism is correlated with columnar growth of the film which can be used as diluted magnetic semiconductor for spintronic applications.

We study the optical and microstructural properties of silver/amorphous carbon (Ag/a-C) nanocomposite thin film and its modification induced by swift heavy ion irradiation. Ag nanoparticles (NPs) embedded in a-C matrix were synthesized by co-sputtering of Ag and graphite by 1.5 keV neutral Ar atom beam. These Ag NPs were irradiated by 120 MeV Ag ions at different fluences ranging from 1 × 10 12 to 3 × 10 13 ions/cm 2 . Optical absorption studies revealed that surface plasmon resonance of Ag NPs in pristine film occurs at a wavelength of ~ 430 nm and it shows a blue shift (~ 26 nm) with increasing ion fluence up to 3 × 10 13 ions/cm 2 . Transmission electron microscopy and Rutherford backscattering spectroscopy were used to quantify particle size and metal atomic fraction, respectively, in the nanocomposite films. The growth of Ag NPs with bi-model distribution at a fluence of 3 × 10 13 ions/cm 2 was observed with ion irradiation. Raman spectroscopy was used to investigate the effect of heavy ion irradiation on carbon matrix. The blue shift in plasmonic wavelength is explained in terms of increase in sp 2 content in carbon matrix by heavy ion irradiation due to thermal energy deposition which leads to a decrease in dielectric properties of the matrix.

International audience; Fabrications of ZnS nanocrystalline thin films at different substrate temperatures (T-S) of 200, 300 and 400 degrees C by means of pulsed laser deposition are presented. Thin film deposited at TS of 200 degrees C is in cubic zinc-blende (ZB) structure while those deposited at TS of 300 and 400 degrees C are in hexagonal wurtzite (W) phase. The grain size, surface roughness and bandgap of the films increases with increasing TS. The zinc vacancies and interstitials in the films increases while sulfur vacancies decreases with increasing TS. The variation of zinc and sulfur vacancies in ZnS films with TS is responsible for structural phase transition from ZB to W which causes the change in energy bandgap.

Nanocomposite thin films of Au–alumina with varying Au contents were synthesized by atom beam co-sputtering. The Au content and the thickness of nanocomposite films were determined by Rutherford backscattering spectrometry. Transmission electron microscopy studies reveal the presence of Au nanoparticles with bimodal size distribution in nanocomposites for lower Au content. Overlapping Au nanoparticles were observed for higher Au content. The increase in size of Au nanocrystals is observed with increase in Au concentration as also evident by glancing angle X-ray diffraction studies. Ultraviolet (UV)-visible absorption studies revealed surface plasmon resonance (SPR) peak which showed a red shift from 519 to 602 nm with increasing Au content of the nanocomposites. Preliminary study exploring the interaction between Au nanoparticles in the nanocomposites and bovine serum albumin (BSA) showed the Au nanoparticles to be BSA sensitive, indicating their possible applications in biosensors.

The present work reports the formation of Ni nanoparticles inside the SiO2 matrix and deals with the influence of Ni concentration on structural and magnetic properties of Ni–SiO2 nanocomposite thin films. The films with varying Ni concentration (20–55 at% measured by Rutherford back scattering spectroscopy) were deposited using DC/RF magnetron co-sputtering. TEM and XRD analysis reveal the formation of FCC Ni nanoparticles in all the samples. The particle size varies from 3 to 10 nm as a function of Ni concentration. The surface roughness of the films is also found to increase with increase in nickel concentration. Magnetic measurements show that the Ni nanoparticles behave as superparamagnets when their size is ≤6 nm, in spite of their large volume fractions. The results show that the magnetic properties of the nanoparticles can be controlled by their size and Ni concentration in the samples.

The present work envisages synthesis of magnetic nanocomposites by ion beam mixing technique using swift heavy ion irradiation of Ni-Teflon bilayer system and its magnetic characterizations. The nanocomposite is characterized by Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM), scanning probe microscopy (SPM) and superconducting quantum interference device (SQUID) magnetometer. Cross-sectional TEM and magnetic force microscopy (MFM) results confirm the formation of nanocomposite. Magnetic characterizations reveal that nanocomposite exhibits ferromagnetic behavior with an increase in the coercivity, which is attributed to the formation of Ni nanoparticles. The coercivity of the nanocomposite is found to be 112 Oe at room temperature which is two orders of magnitude larger than that of the bulk Ni (0.87 Oe). Copyright © 2011 VBRI press.

The magnetic properties of Zn 1− x Co x S ( x =0.025 and 0.05) thin films grown on α-quartz substrates at different temperatures ( T S ) of 200, 400 and 600 °C by means of pulsed laser deposition are presented. The films are crystallized with wurtzite structure. Optical absorption and transmission electron microscopy measurements indicate that Co ions are substituted to Zn on tetrahedral sites. Their magnetic response is composed of ferromagnetic and paramagnetic components of which respective strengths depend on T S and Co concentration. This behavior is interpreted as due to fluctuations in the magnetic ordering, depending on grain size and site location in grain boundaries or in crystal cores.

Structural and spectroscopic modifications of nanocrystalline (nc) ZnO films induced by Swift heavy ion (SHI) irradiation is reported. Films were irradiated at incremented ion fluences. Structural study reveals that the nanocrystals become more oriented at low fluences, while a release of strain and decrease in grain size is observed at high fluence. The surface morphology study also shows a decrease in crystallite size and agglomeration of grains at high fluence. On the other hand micro-Raman and Fourier transform infrared (FTIR) results show that the longitudinal optical (LO) mode is strengthened and red shifted, while the transverse optical (TO) mode get dampened at high fluence. But the amorphization of crystallites was not observed under the used irradiation conditions. The observed structural and spectroscopic modifications are explained in terms of high density of lattice defects and disorder created by dense electronic excitations induced by SHI irradiation. (C) 2011 Elsevier Ltd. All rights reserved.

Swift heavy ion induced stress in a pulsed laser deposited textured ZnO thin film is reported. In situ X-ray diffraction (XRD) measurements are carried out during ion irradiation at incremented fluences under 120 MeV Ag(+9) ions. The average grain size, lattice constant 'c', and stress in the film are calculated from the diffraction pattern. The nature of the stress is intrinsic and the origin can be attributed to the strong density of defects like dislocations at the grain boundaries as evidenced by micro-Raman, Fourier transform infrared (FTIR) spectroscopy and Atomic Force microscopic (AFM) studies. (C) 2010 Elsevier Ltd. All rights reserved.

We have investigated interfacial chemistry in a 100 nm Ni on PTFE (polytetrafluoroethylene) bilayer system induced by 120 MeV Au ions with fluences varying from 1 x 10(12) to 5 x 10(13) ions/cm(2). In-situ quadrupole mass analysis (QMA) shows emission of Fluorine (F) and different fluorocarbons (C(x)F(y)) such as CF, CF(3), C(2)F(3) etc. during irradiation. Electron spectroscopy for chemical analysis (ESCA) studies show that Ni reacts with chemically reactive species such as F(-)/F(center dot). and C(x)F(y) ions or radicals emitted during irradiation forming NiF(2) and metal-polymer complexes (-CFNi-). Rutherford backscattering spectrometry (RBS) was used to analyze the atomic transport at the interface and strong interface mixing is observed at the ion fluence 5 x 10(13) ions/cm(2). Atomic force microscopy (AFM) studies before and after irradiation show that surface roughness is increased from 6.9 to 12.4 nm with increasing fluence. Observed results have been explained on the basis of the chemical reactions taking place within molten ion tracks in the polymer and hot zones around the ion paths created in the Ni film. The studies show that swift heavy ion irradiation introduces strong chemical alteration in the system and induces chemical reactions within the ion track, which enhance ion beam mixing in Ni-PTFE bilayer systems. (C) 2010 Elsevier Ltd. All rights reserved.

International audience; We have prepared germanium nanoparticles embedded in SiO2 matrix by atom beam co-sputtering (ABS) of Ge+SiO2 on Si substrate. The as-deposited films were annealed at various temperatures in Ar+H2 atmosphere and irradiated with various energies with fixed fluence. The pristine and irradiated samples were characterized by Raman, X-ray diffraction and atomic force microscopy (AFM). Rutherford back scattering (RBS) was used to quantify the concentration of Ge in the SiO2 matrix and the film thickness. Raman studies of the films indicate the formation of Ge crystallites as a result of swift heavy ion (SHI) irradiation. Moreover, the crystalline nature of Ge improves with an increase in energy. Glancing angle X-ray diffraction and Raman results also confirm the presence of Ge crystallites in the irradiated samples. Similarly, 400keV Ge+ ions implanted into silicon substrate at higher fluence at 573K have been irradiated with 100MeV Au8+ions at RT. These irradiated implanted samples were subsequently characterized by XRD and Raman to understand the crystallization behavior. We also studied the surface morphology of a high-energy irradiated sample by AFM. The irradiation results were compared with those obtained by thermal annealing in ABS. The basic mechanism for crystallization induced by SHI in these films has been investigated.

The effects of ion irradiation on electrical and magnetic properties of C60 films are investigated and correlated to changes of structure. Conducting nanowires are formed along the linear path of swift heavy ions. Their continuity and radial dimension are correlated with the energy density deposited by such ions in electronic excitations. Whatever the slowing down process of ions, irradiation at high ion fluences induces the formation of an amorphous C phase exhibiting a ferromagnetic response up to room temperature. An additional paramagnetic signal is recorded from films irradiated with swift ions, which is ascribed to the formation of oriented defects decorated with oxygen.

International audience; In the present study, we have investigated the swift heavy ion induced structural modification of ZnO thin film deposited by atom beam sputtering. The films were irradiated by 100 MeV Ag ions at different fluences from 5 x 10(10) ions/cm(2) to 3 x 10(13) ions/cm(2). The influence of the irradiation fluence on structural and optical properties of these thin films was investigated. The structural properties have been studied using X-ray diffraction. The Zn-O bonding was confirmed by Fourier transform infrared spectroscopy and surface morphology was investigated by atomic force microscopy. XRD confirmed that the grain size and texture of the ZnO thin film are increased after the irradiation. The absorption peak intensity corresponding to Zn-O bonding is also increased as a result of energy deposition by swift heavy ion as revealed by FTIR. The AFM study of the films implied that roughness remains almost constant. Power spectral density was also estimated from the AFM micrograph to extract the value of roughness exponent. (C) 2009 Elsevier B.V. All rights reserved.

We report synthesis of a transparent magnetic semiconductor by incorporating Ni in zinc oxide (ZnO) matrix. ZnO and nickel-doped zinc oxide (ZnO: Ni) thin films (similar to 60 nm) are prepared by fast atom beam (FAB) sputtering. Both undoped and doped films show the presence of ZnO phase only. The Ni concentration ( in at%) as determined by energy dispersive X-ray (EDX) technique is similar to 12 +/- 2%. Magnetisation measurement using a SQUID magnetometer shows that the Ni-doped films are ferromagnetic, having coercivity (H(c)) values 192, 310 and 100 Oe and saturation magnetization (M(s)) values of 6.22, 5.32 and 4.73 emu/g at 5, 15 and 300 K, respectively. The Ni-doped film is transparent (> 80%) across visible wavelength range. Resistivity of the ZnO: Ni film is similar to 2.5 x 10(-3) Omega cm, which is almost two orders of magnitude lower than the resistivity (similar to 4.5 x 10(-1) Omega cm) of its undoped counterpart. Impurity d-band splitting is considered to be the cause of increase in conductivity. Interaction between free charges generated by doping and localized d spins of Ni is discussed as the reason for ferromagnetism in the ZnO: Ni film. (C) 2008 Elsevier B.V. All rights reserved.

Zn(1-x)M(x)O (M=Co, Ni, Mn) films with different concentrations of transition metal (10-30%)were synthesized by pulsed laser deposition. The substrates were heated at 400 degrees C and the depositions were performed either under secondary vacuum or under an oxygen pressure of 30 Pa. The occurrence of ion channeling in the films during Rutherford Backscattering Analysis, together with X-ray diffraction, optical absorption and transmission electron microscopy, clearly show that the M atoms are in solid solution on Zn sites. Magnetic properties were investigated by means of magnetometry at 5 and 300 K and Electron Spin Resonance. The Zn(1-x)Co(x)O and Zn(1-x)Ni(x)O films deposited under low 02 pressure exhibit both a ferromagnetic and a paramagnetic response up to 300 K, while films deposited under high 02 pressure and Zn(1-x)Mn(x)O films are paramagnetic. Broad spin resonance peaks are recorded at room temperature, from ferromagnetic films only. The nearly isotropic magnetic response of these films, which is observed in ESR when varying the field orientation with respect to the surface, seems to indicate that the crystalline anisotropy oppose the shape anisotropy, because of the strong [001] texture of the films. (C) 2008 Elsevier B.V. All rights reserved.

Damage caused by swift heavy ions with three different electronic stopping powers (120 MeV Au9+ (22 keV/nm), 90 MeV I7+ (17 keV/nm) and 70 MeV Ni5+ (11 keV/nm)) in three pyrochlores (Gd2Zr2O7, Nd2Zr2O7 and Gd2Ti2O7) with progressively increasing radius ratios (r(A)/r(B) of A(2)B(2)O(7)) of cations is reported. Since I+7 is one of the ions used, these measurements also simulate fission fragment damage in pyrochlores and identify a potential host lattice for inert matrix fuel. X-ray diffraction on the irradiated materials indicate amorphization in Gd2Ti2O7 at the lowest S-e used, and a transition to anion-deficient fluorite (Fm (3) over barm) structure with about 1% decrease in volume in Nd2Zr2O7 and Gd2Zr2O7 at higher S-e. In Nd2Zr2O7 this is followed by amorphization and Gd2Zr2O7 does not amorphize even at the highest S-e employed. Raman analysis of Gd2Zr2O7 and Nd2Zr2O7, indicate an increase of Zr coordination number after irradiation and the bands become broader due to disordering. Analysis of the results shows that the radiation susceptibility of these pyrochlores in the electronic stopping regime strongly depends on the radius ratio of A to B cations and hence on the energy required for formation of cation antisites and anion Frenkel pairs, similar to their susceptibility in the nuclear stopping regime. Published by Elsevier B.V.

International audience; The sensitivity of ZnO films, undoped and doped with Er, Ta and Co, to exposure to NH3 has been studied. The films were deposited by magnetron co-sputtering of a sintered ZnO target with chips of the different doping elements on its surface. The sensitivities of the ZnO films to exposure to NH3 were measured by the quartz crystal microbalance method using the resonance frequency shift. The adsorption process was investigated over an aqueous solution of ammonia with 100 ppm concentration. The speed and the mass of sorption were calculated on the basis of the time-frequency characteristic. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

This paper reports the synthesis of Au nanoparticles (NPs) of different sizes on fused quartz substrates by e-beam evaporation followed by thermal annealing. UV–visible absorption measurements and atomic force microscopy (AFM) studies have been carried out on the as-deposited and the annealed samples. While as-deposited samples show no signature of NP formation, the annealed samples show a signature of surface plasmon resonant (SPR) absorption at ~520 nm, which clearly indicates the presence of Au NPs. AFM images show the formation of Au NPs in the case of annealed samples. The red and blue shifts in the SPR peak position in the absorption spectra with increased annealing temperatures are due to the growth and the dissolution of Au NPs, respectively. The average size (diameter) of the Au NPs, estimated from the AFM data is in good agreement with the absorption results. We have observed growth in the size of the Au NPs up to a certain annealing temperature beyond which dissolution of the Au NPs starts. The formation of gold nanorings has also been observed under appropriate annealing conditions.

Silver nanoparticles (Ag NPs) embedded in silica were prepared by a novel process of atom beam sputtering (ABS). Optical and structural properties of Ag NPs were studied by using ultraviolet–visible absorption, transmission electron microscopy and X-ray diffraction. The processes involving nucleation and growth of Ag NPs are discussed. The superiority of the ABS over ion implantation and ion beam mixing is discussed. These Ag NPs are found to be glucose sensitive, indicating their possible application in medical diagnostics.

Gold nanoparticles embedded in silica matrix were prepared by co-evaporation. After deposition, the samples were annealed at different temperatures in inert environment for 30 min. No signature of nanoparticle formation was found in case of as-deposited samples, while the annealed samples showed a clear signature of a surface plasmon resonance absorption peak around 520 nm, which indicated the formation of Au nanoparticles. The samples annealed at 900 °C were irradiated with 100 MeV Ag ions at fluences 2.5×1012 and 1×1013 ions/cm2. UV-visible absorption measurements of pristine and irradiated films showed a clear signature of dissolution of Au nanoparticles with ion beam fluence. X-ray diffraction studies of pristine and irradiated samples also supported the dissolution of Au nanoparticles with ion beam fluence. Rutherford backscattering spectrometry was used for quantification of gold.

International audience; This review covers some key concepts related to embedding of the noble metal nanoparticles in polymer surfaces. The metal nanoparticles embedded into the polymer matrix can provide high-performance novel materials that find applications in modern nanotechnology. In particular, the origin of various processes that drive the embedding phenomenon, growth of the nanostructure at the surface,factors affecting the embedding including role of surface, interface energies and thermodynamic driving forces with emphasis on the fundamental and technological applications,under different conditions (annealing and ion beams) have been discussed. In addition to the conventional thermal process for embedding which includes the measure of fundamental polymer surface properties with relevant probing techniques,this review discusses the recent advances carried out in the understanding of embedding phenomenon starting from thin metal films to growth of the nanoparticles and embedded nanostructures using novel ion beam techniques.

Thin films of silica containing 0.15 at.% Eu and 3.5 to 7 at.% Na were prepared by sol–gel chemistry and annealed at 600 ° C in air, then submitted to ion–exchange treatments in NaNO3 : AgNO3 for studying the effect of the plasmon resonance of Ag nanoparticles on the excitation of Eu3+ ions. When excited at other wavelengths in the UV other than that corresponding to the 7F0–5L6 transitions of the Eu3+ ions, the yield of the 5D0–7F2 emission is increased by a factor of the order of 10 in films containing Ag particles with respect to that in non-exchanged films.

Three phase transitions (face centered to simple cubic, surface rearrangement from (2×2) to (1×1) and glass transition) in fullerene thin films and the effect of 150 MeV Ti ion irradiation on these transitions have been studied, using temperature dependence of electrical resistivity measurements. The structural properties of the C60 thin films are studied by X-ray diffraction, atomic force microscopy and UV–vis spectroscopy. It is observed that defect creation by ion irradiation in the films lead to quenching and broadening of structural phase transitions but the transition temperatures did not show significant shifting under ion irradiation.

Effects of swift heavy ions irradiation on silica films containing Fe under the form of solute ions or metal particles have been investigated, using electron spin resonance and magnetometry. The results indicate that electronic excitations induce the reduction of solute ions and the precipitation of metal particles when the Fe concentration is not too low. The hammering effect of ions on the silica matrix causes a tilt of easy magnetization axis when the volume fraction of particles is of a few percents, but this axis remains in the film plane for fraction over 10%.

The modification of fullerenes vibrational properties by energetic ion irradiation is investigated, using Fourier transform infrared (FTIR) spectroscopy . The C60 thin films have been irradiated with 200 MeV Au ions at fluence from 1 × 1012 to 1 × 1013 ions/cm2. It is observed that 577 cm−1 mode is the most sensitive but 527 cm−1 IR active mode is more resistive for swift heavy ion irradiation. To understand change in the molecular structure of fullerene molecule under swift heavy ion (SHI) irradiation, we determined damage cross-section for all four T1u (527, 577, 1183, 1428 cm−1) IR active modes. It is observed that damage cross-section (σ) is different for different vibrational modes. The effective radii (r) of the damage cylindrical zone are also evaluated.

Sol–gel materials are converted into glassy ceramics when subjected to ion irradiation or heat treatments. In addition, a demixing occurs in the obtained glasses when their structure is metastable. In the present work, we have irradiated silicon-based gels with 120 MeV and 2 GeV Au ions at different fluences from 8 × 109 to 2 × 1013 ions/cm2. Ion irradiation leads to formation of carbon nanoclusters, which have semiconducting properties. Photoluminescence and optical absorption spectroscopies are used to identify the semiconducting properties of carbon clusters. High resolution transmission electron microscopy (HRTEM) and energy filtered imaging of C atoms show that C particles with a size of not, vert, similar4 nm are produced and they are aligned along ion tracks. Elastic recoil detection analysis has been performed to determine the kinetics of the H evolution and to evaluate the track radius, which matches with the radius obtained from HRTEM. The obtained aligned carbon clusters (wires) would find useful applications as field emitters or nanocontacts.

Thin films of high-quality polycrystalline silicon (poly Si) on different substrates are of interest for manufacturing thin film transistors, solar cells, and image sensors. In this study, we present the results of an investigation of poly Si films on glass, formed by nickel-induced crystallization. The process is based on isothermal annealing in air at 550 and 560 °C of co-sputtered Ni+Si films deposited on glass at different substrate temperatures, with and without the application of an electric field to the films. The poly Si films were investigated by Raman spectroscopy and Rutherford back-scattering. It was established that the substrate temperature and the Ni-concentration in the precursor amorphous Si+Ni films are important parameters for nickel-induced crystallization.

The formation of high-quality polycrystalline silicon (poly-Si) on low cost substrates has important applications in the development of thin film solar cells, transistors, image sensors, etc. In this study, we present the results of an investigation of poly-Si and poly-SiGe films on glass, formed by aluminum induced crystallization (AIC). The process is based on the isothermal annealing at temperatures between 500 and 540 °C of co-sputtered Si+Al, Si+Ge or sputtered a-Si films on glass, with and without thermally evaporated or sputtered Al film. The crystallized films were investigated by Raman spectroscopy, optical microscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Raman spectra demonstrate the crystalline structure of the poly-Si and poly-SiGe films prepared by AIC. The grain sizes of the poly-Si films estimated from the SEM and optical microscopy images are up to 25 μm for the different annealing conditions.

The processes of nucleation and growth of silver clusters under ion irradiation are investigated respectively in ion-exchanged glasses containing no clusters and in sputtered films, in which all the metal is precipitated before the irradiation. The studied samples were irradiated with He or Au ions of energy in the range of 1–100 MeV and the yields of precipitation or growth were assessed by combining measurements of luminescence and of optical absorption. The two processes result from electronic excitations and the nuclear collisions have insignificant effect. The nucleation rate is proportional to the product of the reduction cross section of Ag + ions by the ion fluence and the process involves the transient formation of Ag 3 2+ ions. Ag atoms must be released from clusters in order to permit the growth of some others in a matrix free of solute atoms (sputtered films) and this desorption is the stage limiting the growth rate. The desorbed atoms remain in solid solution when the density of electronic excitations exceeds a threshold value.

Ion irradiation of silicon-based gels with the stoichiometry SiO1.5H1, prepared from triethoxysilane, and containing Fe3+, Ni2+ or Cu2+ ions in solid solution permits to obtain the precipitation of metallic nanoparticles. Comparison of the particles volume fractions in films irradiated with 1.5 MeV He or 3 MeV Au ions on basis of their optical absorption or magnetic resonance indicates that electronic excitations are responsible for the reduction and precipitation processes, while atomic displacements induce a partial redissolution by mixing. Moreover, the precipitation yield increases almost in proportion to the ion fluence. Measurements of magnetization as a function of the temperature show that the Fe and Ni particles in irradiated films are superparamagnetic and their range of sizes is narrower than in films heat treated in vacuum at 600–1000 °C.

Recently nanocomposites with sensoring function are becoming a new area of interest in the field of optical gas sensor. In fact, the optical transmittance of nano-particles or thin films has been reported to be changed by atmosphere gases. In particular it was found that NiO, Co 3 O 4 and Mn 3 O 4 thin films showed reversible decrease in the Vis-NIR absorption due to CO. Aim of this work is the synthesis and the characterization of SiO 2 sol-gel glass films doped with NiO nanocrystals. Films of composition (100-X)SiO 2 -XNiO with X = 10, 20, 40, were obtained by mixing a matrix solution of Si(OC 2 H 5 ) 4 (TEOS) and CH 3 Si(OC 2 H 5 ) 3 (MTES) as SiO 2 precursors, with a doping solution containing NiCl 2 as precursor for NiO particles. 3-Aminopropyltriethoxysilane (3-APTES), bearing either an ammine group capable of coordinating the Ni ions and hydrolysable siloxane groups for anchoring the metal complex moiety to the silicate matrix, was used as bifunctional ligand. Transmission electron microscopy micrographs showed a uniform distribution of round shaped nanoparticles in film heated at 500°C with a mean diameter of 2.5 nm. The film composition evaluated from Rutherford backscattering spectrometry.was in good agreement with the nominal one. As expected the density of the films heated at 1000°C is much higher than the density of the film heated at 500°C due to a residual porosity. Fourier transform infrared spectra also confirmed the presence of residual porosity in the films heated at 500°C.

The sensitization of the infrared luminescence of Er ions by Si clusters is studied in oxide films derived from tetraethoxysilane and triethoxysilane gels, doped chemically or by ion implantation with Er and/or Si. No quenching of the luminescence by impurities and structural defects is observed with respect to ion-implanted silica, and a maximum enhancement is observed in the SiO1.5 suboxide formed from triethoxysilane. The segregation of erbium silicide or oxide, depending on the synthesis procedure, deactivates the Er ions when their concentration exceeds 1 at % or the temperature of annealing is above 1050 °C.

Irradiation-assisted processing, i.e. ion, electron and laser irradiation, have been applied to fabricate metal/glass nanocomposites. The particle configurations are studied by transmission electron microscopy to get some insight into the rather complex formation mechanisms. Special attention is given to spheroidally shaped particles surrounded by smaller secondary particles observed upon ion beam mixing of silica/silver/silica layer compounds as well as irradiating femtosecond laser pulses on sodium silicate glass containing spherical silver particles. Another unique type of structure are cavities observed in silver particles formed by high fluence ion implantation into silica as well as upon laser pulse irradiation of silver particles in glass. The experimental findings are discussed in terms of irradiation-induced defect formation and radiation-enhanced diffusion.

The transformations induced by ion irradiation in films of polycarbosilane and gels derived from tetraethoxysilane, methyltriethoxysilane and triethoxysilane have been studied. Hydrogen is released selectively under the effect of electronic excitations at a rate depending on the probability of H radicals to combine for forming molecules inside the film. The radiolysis efficiency of C—H bonds is the lowest and that of Si—H bonds the highest. Beside the conversion of the polymeric structure into an amorphous ceramic, ion irradiation induces the precipitation of C or Si clusters, according to the precursor, leading to a noticeable luminescence in the visible. This precipitation has been put into evidence for the first time by energy filtered electron microscopy.

Silicon nanoclusters formed in triethoxysilane during annealing at temperatures above 900°C are used for increasing the excitation cross section of Er atoms. A stronger sensitization of the Er luminescence is observed, for a given Er concentration, when the Er3+ ions are introduced in the matrix by ion implantation than when adding a salt to the precursor solution, because of a better dispersion of the implanted atoms. The logarithmic increase of the emission yield with the Er concentration up to 1 at% which is found in the case of implanted samples is ascribed to the quenching processes by interaction between neighbour Er3+ ions.

International audience; The magnetic properties of Ni doped ZnS thin films fabricated at substrate temperature of 400 degrees C by means of pulsed laser deposition are presented. The films show crystalline wurtzite structure. Optical absorption and transmission electron microscopic studies indicate that Ni has been appropriately substituted on Zn tetrahedral site. The films show ferromagnetism up to room temperature. The magnetization in the films decreases with increase of Ni concentration. Swift heavy ion (SHI) irradiations have been carried out using 120 MeV Ag ions for the modification of structural and magnetic properties of the films. SHI irradiation suggests the formation columnar ion track inside the films causing decrease in magnetization. (C) 2014 Elsevier Ltd. All rights reserved.

a-Si 1− x C x :H thin films doped with different concentrations of Tb have been deposited by magnetron co-sputtering. The carbon content in the films is varied in order to change the optical gap. RBS analysis shows that Tb is homogeneously distributed in the bulk. Optical absorption spectra in the visible are studied and changes in the optical gap and the defect absorption with increasing Tb concentration are observed. The laser excited photoluminescence (PL) of the films is studied after annealing at 300°C in Ar atmosphere. It consists of a broad band covering the whole visible spectrum. The position of the PL band does not change when the carbon content in the films is increased from 10 to 25 at%. It is tentatively assigned to the Tb 3+ impurity.

Ag nanoclusters in a SiO2 matrix prepared by RF magnetron co-sputtering and subsequent irradiation with heavy 4.5 MeV Au+ ions were formed. The refractive index and optical absorption spectra of the films were studied. The method of the disappearing diffraction pattern was used for the refractive index determination. The refractive index enhances with increasing Ag concentration, as expected from the light scattering theory. SiO2:Ag thin films exhibit a plasmon resonance in the visible region. In the as-deposited films the Ag nanoclusters are less than 1 nm and are formed during the deposition. The intensity of the plasmon peak is low. After irradiation with 4.5 MeV Au+ ions the intensity of the peak increases and the peak becomes narrower. The TEM study shows that this is related to the change in the size of the Ag nanoclusters.

SiOx thin films with various oxygen contents (1.1⩽x⩽1.7) have been prepared by thermal evaporation of silicon monoxide in vacuum. The film composition is controlled by changing both deposition rate (between 0.2 and 6 nm/s) and depositing the films at two different residual pressures, (2×10−4 or 1×10−3 Pa). Long-term stability of all films is ensured by a post-deposition anneal at 520 K for 30 min and this is explained with reference to the annealing-induced decrease of the volume fraction occupied by pores in the film. The oxygen content, x, of each film is determined using both infrared absorption and Rutherford backscattering measurements and the x-values obtained in each case are quite different. The observed difference is related to the low density of the films, particularly those deposited at high residual pressure and high deposition rates, which, in addition to the oxygen deficiency, decreases the frequency of the TO stretching mode. An increase of the oxygen content of the films is observed upon annealing at 970 K accompanied by formation of amorphous silicon particles. Phase separation is completed after annealing at 1300 K and Si nanocrystals embedded in SiO2 matrix are produced, but the infrared absorption results show that the level of chemical disorder in the matrix is appreciably higher than that in ‘pure’ SiO2 thin films.

Precipitation of silver clusters in silica is achieved by different methods: ion implantation, ion beam mixing of superimposed layers and ion irradiation of films deposited by means of co-sputtering or sol-gel technique. Main features of the nanoparticles depending on the preparation method are investigated by TEM. The optical extinction resonance of these clusters is analysed in terms of sizes and interaction between the clusters on the basis of calculations. We found that resonances in sputtered and gel films with low metal concentrations are well described by plasmon polaritons in isolated clusters and calculations based on Mie theory allow the study of their growth under irradiation. This theory is not appropriate to describe the optical response of silver clusters in silica implanted with Ag concentrations higher than 5 at.% or in ion beam mixed films, because of the interaction between clusters. Using an effective medium model, it is demonstrated that the random dispersion of clusters in implantation films causes fluctuations and, on average, an increase of the clusters polarization. On the contrary, the particular arrangement of the clusters with a bimodal size distribution in ion beam mixed films induces a screening effect between the clusters of largest size.

The release of H from Si-based polymers under irradiation by He, C, Si, Cu, Ag and Au ions of different energies has been studied. The ions and energies have been chosen in such a way that they cover a wide range of electronic and nuclear energy loss values. Results are analysed in the frame of three different models. A model of track percolation leading to an exponential decay of the H concentration as a function of ion fluence fits the kinetics of H evolution only on a limited range of fluence. An explanation is proposed in the second model, assuming that the radiolytic efficiency in the core of tracks changes when the tracks overlap. A better agreement is found however with a model implying the diffusion of molecular hydrogen in the material after combination of two radicals formed within a critical recombination volume.

Spectra of optical extinction in the visible range for SiO 2 :Ag colloid films prepared by ion implantation and ion beam mixing are compared to calculations for isolated clusters and for interacting clusters in an effective medium. Whereas for low metal concentrations the shape of the spectra is determined by the cluster size, at higher concentrations it largely depends on their mutual interaction. This interaction induces a broadening of the resonance in implantated films and on the contrary a narrowing in ion beam mixed films. The difference is ascribed to a particular arrangement of the clusters, with a bimodal size distribution, in the latter films.

We present results of X-ray fluorescence measurements (carbon Kα and Si L2,3) of methylhydroxylsiloxane and phenylmethylhydroxylsiloxane films. The films are converted into amorphous ceramics by irradiation with 500 keV C and 3 MeV Au ions. Changes in the composition (O/Si ratio) of some polysiloxane films are found when treated with ion irradiation. It is shown that ion irradiation induces a segregation of carbon atoms from methyl groups into diamond-like clusters whereas carbon atoms from phenyl groups maintain their sp2 configuration.

The mixing of noble metals (M) with various oxides under 4.5 MeV ion irradiation and the concurrent process of metal segregation were studied by means of Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). Simulations of the widening of RBS M peaks due to the spheroidization of the M layer, using particles sizes measured in TEM, indicate that the effect is noticeable but does not determine the mean square spread of the M depth distribution. RBS analyses show that recoil implantation is the predominant mechanism of injection of M atoms into the oxide matrix. The spreading is controlled either by the recoil implantation or the radiation-enhanced diffusion of M atoms according to their mobility. In particular this mobility depends on the M mass and on the oxide ionicity.

Layers of noble metals M embedded in various oxide matrices (SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , and also Si for a purpose of comparison) were irradiated with incremented fluences of MeV heavy ions. A major contribution of recoil implantation to displacements accounts for the linear rates of atoms relocation as a function of the ion fluence, measured by means of RBS. According to the temperature and to the initial thickness of the M layer, the in depth-straggling of M atoms varies in proportion to the ion fluence or to its square. This change of straggling rate is explained by its control either by the radiation-enhanced diffusion or by the recoil implantation process, when the solution of diffusion equations relative to an infinitely thin source cannot be applied. The mobility of M atoms in the oxide depends on the latter ionicity and on the M mass.

Thin layers of noble metals (M=Cu, Ag, Pd, Pt, Au) embedded in silica were submitted to irradiation with increasing fluences Φ of 4.5 MeV Au ions. Concurrently to the mixing of metal and silica atoms, the irradiation promotes the clustering of the metallic phase. Metallic particles were observed in transmission electron microscopy in order to determine if their size contributes for a large part to the spreading of the M distribution measured by Rutherford Backscattering Spectrometry (RBS). The part of this spreading due to the recoil implantation of M atoms into the silica matrix and to their radiation-enhanced diffusion is yet larger. The variance of the distribution increases in proportion to Φ or to its square, depending on whether it is controlled by the diffusion (thin films) or the recoil implantation process (thicker films).

The electronic structure and chemical bonding of unirradiated and irradiated Poly-1,4-phenylene-ether-sulphone (PES) films have been studied with fluorescent X-ray emission spectroscopy. PES films have been irradiated with 150 keV Ar + ions at concentrations of 5 × 10 13 , 1 × 10 14 , 1 × 10 15 and 7.5 × 10 15 cm −2 . The electronic structure of PES has also been calculated with MO LCAO calculations using a deMon density functional theory (DFT) program and shows good agreement with the experimentally obtained X-ray fluorescence spectra (S L 2,3 , C Kα and O Kα). It is found that the C Kα X-ray emission spectra (XES) of irradiated PES films display marked changes at very high concentrations (1 × 10 15 − 7.5 × 10 15 cm −2 ), similar to the spectroscopic characteristics of amorphous carbon. According to our measurements, the low-energy shift of the S Kα 1,2 XES is observed for concentrations greater than 5 × 10 13 cm −2 which is related to the reduction of –SO 2 – to –S– following the transfer of an oxygen atom from the –SO 2 – functional group to the radical site.