Papers

ICMCTF2007 Session C2/E5: Mechanical Characteristics of Optical Films

Monday, April 23, 2007 10:00 AM in Room California

Monday Morning

Start	Invited?	Item
10:00 AM		C2/E5-1 Loading Rate Effects on the Fracture Behaviour of Solar Control Coatings During Nanoindentation J. Chen, S.J. Bull (Newcastle University, United Kingdom) Contact damage of coating materials is life-limiting in many applications. For brittle coatings the fracture response is key to performance. In this study we have investigated the effect of the loading rate on the nanoindentation fracture response of the most important layers in solar control coatings deposited on glass. It was found that the higher the loading rate the bigger fracture threshold within the loading range for all the oxide coatings (<400nm in thickness). SnO₂ and ITO coatings show quite different behaviour compared to the other materials tested (such as TiO_xN_y, ZnO etc) in this study and many other ceramics coatings reported in literature; at a given depth (ie. 400nm peak displacement by a cube corner tip in which case evidence of fracture was observed for all the coatings discussed in this study) the maximum load was found to increase dramatically when the displacement rate increases from 20nm/s to 40nm/s, which was neither observed for the other coatings investigated in this work nor in test conditions where fracture was absent. The possible mechanisms to account for such abnormal behaviour for these two coatings will be discussed.
10:40 AM		C2/E5-3 Multiscale Modelling of the Mechanical Properties of Thin Films R. Smith, E. McGee, S.D. Kenny (Loughborough University, United Kingdom); A. Richter (University of Applied Science, Wildau, Germany) Nanoindentation and nanoscratching are modern tools for investigating the mechanical properties of many different materials including optical thin films. This paper describes a new multiscale technique that can be used to determine the mechanical properties of optical materials by modelling the nanoindentation and nanoscratching processes. In this model the plastic deformation region of the material is considered atomitically and this is linked to a region in which elastic deformation takes place which is analysed using finite elements. The two regions are linked in a smooth way which conserves energy which is the key to the success of the technique. Examples are given which show good agreement with experiment both in terms of the hardness and elastic modulus of hard materials and also in the prediction of the pile-up mechanisms and patterns during indentation and stick-slip and friction during scratching.
11:20 AM		C2/E5-5 Near-Interfacial Delamination Failures Observed in Ion Beam Sputtered Ta₂O₅/SiO₂ Multilayer Stacks M. Grigonis, W. Hebenstreit, M.K. Tilsch (JDSU) Ion beam sputtered Ta₂O₅/SiO₂ multilayer stacks have been mechanically stressed to failure. The delamination failures do not occur precisely at the layer interfaces. XPS and AFM analyses indicate that the failures occur near the interfaces where SiO₂ was deposited on Ta₂O₅. Delamination is not observed near the interfaces where Ta₂O₅ was deposited on SiO₂. The failure location is 2-3 nm into Ta₂O₅ layers and can occur randomly near multiple interfaces within a test. The delamination failures were induced by performing tape pull tests over lines scribed into the multilayer coatings.
11:40 AM		C2/E5-6 Optical and Mechanical Properties of Transparent Conducting and Semiconducting Al_xCoCrCuFeNi Oxide Films T.K. Chen, M.S. Wong (National Dong Hwa University, Taiwan) Multicomponent Al_xCoCrCuFeNi (x = 0.5, 1 and 2) oxide thin films were prepared by means of reactive sputtering using multi-principal-element alloy targets. They showed unexpected simple structure of a cubic-spinel-type AB₂O₄ lattice and a wide range of resistivity variation from conducting to semiconducting depending on compositions. Optical properties of the oxide films were analyzed according to their UV-visible spectra, Fourier transform infrared spectra, and Raman spectra. These oxide thin films exhibited both visible and infrared transparency, and the percent absorption and absorption edges varied with compositions. The oxide thin films also showed superior mechanical properties measured by nanoindentation technique.