WEB Extending the study of mechanical size effects by the means of Reflectance Anisotropy Spectroscopy.Wednesday (01.01.2020) 05:30 - 05:45 Part of:
Materials exhibit different mechanical behavior if they are down-sized to the micro- or nanometer scale. These mechanical size effects, with the most common one phrased as “smaller is stronger”, have been studied extensively during the last two decades. Amongst others, by the means of Nano-indentation, Synchrotron XRD, Wafer-curvature, micropillar-compression, bulge-testing, cantilever-bending, nanowire-tensile experiments, and lately also by Reflectance Anisotropy Spectroscopy (RAS).
When it comes to polycrystalline thin films however, all the above mentioned techniques (except RAS) are getting less reliable when it comes to ultra-thin films, with thicknesses below 50 nm. Nevertheless, these ultra-thin films are already widely used in industry, e.g. as reflection- or diffusion-barriers. The importance of insights into their mechanical properties, to avoid failure, will only increase with the coming up-rise of flexible electronics.
As the RAS is probing the dielectric function in two orthogonal directions, it is highly sensitive to anisotropic changes in lattice spacing, as it is the case e.g. under uniaxial loading. We are here demonstrating how RAS offers the ability to qualitatively and reliably in-situ test ultra-thin films on flexible substrates with film-thicknesses significantly below 50 nm, by presenting a new size effect study on Gold down to 20 nm thin polycrystalline films. The method is not limited to any material or materials class, as long as the films are continuous and the material has an electronic transition in our detection range (1.5 - 5.5 eV).