MEASUREMENT OF YOUNG'S MODULUS AND POISSON'S RATIO OF THIN FILMS BY SYNCHROTRON X-RAY DIFFRACTION

A new experimental method for determining elastic constants of thin films is proposed. The curvatures of the single crystal substrates before and after depositing thin film are first measured using high-resolution X-ray rocking curve technique with high quality monochromatic and high intensity synchrotron radiation. The residual stress in the film is then calculated from the change in substrate curvature based on the well-known modified Stoney's equation. The formulae for calculating thin film's Young's modulus and Poisson's ratio are deduced based on measured residual stress and the lattice spacing dψ versus sin2ψ curves of the film before and after an unknown mechanical loading. LaNiO3 film grown on single crystal silicon substrate using pulsed laser deposition is employed to demonstrate the measurement method.