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Advanced resonant ultrasound spectroscopy for measuring anisotropic elastic constants of thin films
Author(s) -
OGI H.,
NAKAMURA N.,
HIRAO M.
Publication year - 2005
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.2005.00885.x
Subject(s) - resonant ultrasound spectroscopy , thin film , materials science , anisotropy , tripod (photography) , resonance (particle physics) , substrate (aquarium) , spectroscopy , crystallite , piezoelectricity , optics , composite material , elastic modulus , physics , nanotechnology , atomic physics , metallurgy , oceanography , quantum mechanics , geology
This paper presents an advanced resonant ultrasound spectroscopy (RUS) method to determine the elastic constants C ij of thin films. Polycrystalline thin films often exhibit elastic anisotropy between the film growth direction and the in‐plane direction, and they macroscopically show five independent elastic constants. Because all of the C ij of a deposited thin film affect the mechanical resonance frequencies of the film/substrate layer specimen, measuring resonance frequencies enables one to determine the C ij of the film with known density, dimensions and the C ij of the substrate. Resonance frequencies have to be measured accurately because of low sensitivity of the C ij of films to them. We achieved this by a piezoelectric tripod. Mode identification has to be made unambiguously. We made this measuring displacement–amplitude distributions on the resonated specimen surface by laser Doppler interferometry. We applied our technique to copper thin film and diamond thin film. They show elastic anisotropy and the C ij smaller than bulk values of C ij . Micromechanics calculations indicate the presence of incohesive bonded regions.