Papers

ICMCTF2008 Session F1-1: Advances in Characterization of Coatings and Thin Films

Monday, April 28, 2008 10:00 AM in Room Royal Palm 4-6

Monday Morning

Start	Invited?	Item
10:00 AM		F1-1-1 Advanced Analysis Methods for Advanced Coatings: The Use of Ions, Photons and Electrons P. Schaaf (University of Göttingen, Germany) Advanced Coatings are making more and more use of nanostructured and smart materials with superior properties leading also to more and more complicated processing for obtaining them. Therefore, sophisticated and well suited analytical tools are necessary to prove the quality and also for optimizing the processing. The complexity of such materials processing and analysis makes it inevitable to rely on a combination of complementary analysis methods in order to achieve a complete ‘picture’ of the metallurgical processes within and the properties of the coatings. It will be demonstrated how ions, photons and electrons can be used for the advanced analysis of advanced coatings, surfaces and thin films. The use of ion-beam analysis (Rutherford Backscattering Spectrometry, Nuclear Reaction Analysis, Channelling, SIMS), Mössbauer Spectroscopy, Magneto-optical Kerr Effect, photoelectron spectroscopy, Raman spectroscopy, SEM/TEM with EDX and SAD, Squid, AFM/MFM, XRD, X-ray absorption spectroscopy, and some others will be illustrated. Besides the well-known ‘conventional’ use of these methods, it will be presented how an intelligent design of an experiment can yield superior details and conclusions. The benefits from a clever combination of the right analysis methods will be exemplified by metallurgical coatings and films for industrial applications: high temperature coatings with sharkskin and lotus effect, hard coatings for wear applications, coatings for corrosion resistance, magnetic films for storage or sensor applications, and photovoltaic materials.
10:40 AM		F1-1-3 Microstructural and Compositional Studies of TiAlSiN Nanostructured Coatings V. Godinho, T.C. Rojas (Instituto de Ciencia de Materiales de Sevilla CSIC-US, Spain); F.J. Ferrer, J. Garcia-Lopéz (Centro Nacional de Aceleradores CSIC-US, Spain); A. Justo (Instituto de Ciencia de Materiales de Sevilla CSIC-US, Spain); M.P. Delplancke-Ogletree (Université Libre de Bruxelles, Belgium); A. Fernández-Camacho (Instituto de Ciencia de Materiales de Sevilla CSIC-US, Spain) In the last decade the industry demands for hard coatings with enhanced thermodynamic stability has increased the interest in the study of superhard TiAlSiN nanocomposite coatings. A full characterisation of nanostructured TiAlSiN coatings at the microstructural and compositional level is needed to understand the good mechanical properties of these coatings. In this work, the influence of experimental parameters such as power of the sputtering source and appliance of a bias voltage during deposition has been correlated with the structure and composition of the coatings. The studied coatings have been deposited onto different substrates by using reactive magnetron sputtering. The synthesis process has been carried out with two commercial TiAl (75/25 at. %) and Si (99.999 at. %) targets. The combination of different characterization techniques such as grazing incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM) associated to electron diffraction (ED) and electron energy loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) will be presented as a suitable methodology to characterize nanostructured coatings in general and the TiAlSiN coatings in particular.
11:00 AM		F1-1-4 Characterisation of Silica Films Deposited on Titanium Substrates: Analysis of Surface Chemistry, Morphology and Functional Hydroxyl Groups E.J. Szili (Flinders University / University of South Australia); S. Kumar, R.St.C. Smart (University of South Australia); N.H. Voelcker (Flinders University, Australia) Previously, we have developed and characterised a procedure for the deposition of silica thin films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. The coatings have been shown to improve the corrosion resistance of nickel and induce bioactivity on the titanium (Ti) surface ^[1-3]. The process involves a 3-step reaction: air plasma etching for surface cleaning and oxidation; air/TEOS for silica deposition and air/H₂O₂ for surface hydroxylation. Silica coatings deposited using our PECVD method (PECVD-Si) feature a graded metal/oxide/silicate/silica surface layer that strongly adheres to the material substrate. Since its development, we have been fine-tuning the PECVD method for producing high quality and reproducible PECVD-Si coatings on metals, primarily aimed at surface immobilisation of biomolecules. This requires a complete investigation of the surface, chemical and morphological properties of the films deposited using the optimised parameters. Therefore, this current investigation was carried out to analyse the characteristic features of PECVD-Si deposited on Ti substrates. The surfaces were characterised by atomic force microscopy (AFM), scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and contact angle (CA). Ti surfaces cleaned by air plasma exhibited slightly reduced surface roughness, lower hydrocarbons and a thicker surface oxide layer as compared to the untreated Ti surfaces. Silica was deposited at a higher rate in air carrier gas compared to oxygen. Small globular structures (possibly from gas phase nucleation of TEOS species) were evident on PECVD-Si and the coatings were conformal to the substrate surface. The PECVD-Si surface was composed of stoichiometric SiO₂ and showed a low carbon content (below 10 at.%). PECVD-Si strongly adhered to Ti and was resistant to delamination. Finally, the silica coatings were very hydrophilic (CA <10º). [1] Arora, P.S., Smart, R.St.C., Surface and interface analysis, 24 (1996) 539. [2] Stevenson, M., Arora, P.S., Smart, R.St.C., Surface and interface analysis, 26 (1998) 1027. [3] Zhang, H., Simpson, D., Kumar, S., Smart, R.St.C., Colloids and surfaces A: Physiochemical and Engineering Aspects, 291 (2006)128.
11:20 AM		F1-1-5 PVD-Grown Photocatalytic TiO₂ Thin Films on Polymer Substrates for Sensors and Actuators Applications C.J. Tavares, S.M. Marques, S. Lanceros-Mendez, V. Sencadas, C.M. Costa (University of Minho, Portugal); E. Alves, N. Franco, N.P. Barradas (Instituto Tecnológico Nuclear, Portugal); A.J. Fernandes (University of Aveiro, Portugal) Titanium dioxide’s self-cleaning effect has been broadly used in textiles, paints, windows, residual water treatment, amongst various other photocatalytic applications. Polymer substrates have found their way in the semiconductor industry as a base layer for flexible electronics, as well as in sensor and actuator applications. The optimum performance of these systems may be affected by dirt adsorbed on its surface, which can also originate mechanisms for the degradation of the polymer. The authors have endured an extensive research in order to enhance the photocatalytic efficiency and the mechanical properties of titanium dioxide thin films on glass and polymer substrates. These thin films have been deposited by unbalanced reactive magnetron sputtering on different polymers. Rutherford Backscattering experiments evidenced that these coatings have a TiO₂ stoichiometry, which remains stable after thermal annealing in vacuum at 500 °C. X-ray diffraction revealed that the as-deposited coatings are mostly amorphous, however some evidence of anatase crystalline phases are apparent from Raman spectroscopy experiments. The photocatalytic behaviour of the titanium dioxide coatings was determined by combined ultra-violet/visible irradiation and absorption measurements. In order to assess the mechanical behaviour of the as-sputtered films, the film/substrate composite system was loaded unidirectionally using a tensile testing machine. The stress-strain curves were analysed and correlated with photocatalytic efficiency and structural data.
11:40 AM		F1-1-6 SEM and Raman Study of Anatase Nano-Structures V. Vishnyakov, N. Mahdjoub, N. Allen, P. Kelly (Manchester Metropolitan University, United Kingdom); C. Bygott, J. Stratton (Millennium Chemicals, United Kingdom) Titania nano-structures used in the present study have been created by Ion Sputtering, Magnetron deposition and synthesised by the sulphate process. Thin films and powders have been annealed in air at temperatures up to 1022 K for 30 min. The materials have been characterised by X-Ray Diffraction (XRD), Low Energy Scanning Electron Microscopy (SEM) and micro-Raman. Nano-crystallite sizes were derived from XRD by use of the Scherrer equation. Physical Vapor Deposition processes only created Anatase phase at substrate temperatures above 600 K. Additional annealing at 1022 K results in average crystal coarsening from 13 to 72 nm. Raman spectra of crystalline films show peaks which are characteristic of anatase phase. The peak positions and Full-Width-at-Half-Maximum (FWHM) change considerably during annealing. There is similarity in peak behavior between thin films and nano-powders. For instance, the low energy E_g peak shifts from 146 to 154 cm-1 after temperature treatment at 1022 K and the peak FWHM changes from 29 to 11 cm^-1. High energy peaks show compression stress in deposited films. This stress is not presented in nano-powders. The analysis indicates that peak behavior is closely correlated to the first order phonon confinement phenomena and might be related to Oxygen vacancy annealing at high temperatures.