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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.

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.

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.

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.

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.