Colombi, Paolo3; Bergese, Paolo4; Bontempi, Elza4; Borgese, Laura4; Federici, Stefania4; Keller, Stephan Sylvest5; Boisen, Anja5; Depero, Laura Eleonora4
1 Department of Micro- and Nanotechnology, Technical University of Denmark2 Nanoprobes, Department of Micro- and Nanotechnology, Technical University of Denmark3 CSMT Gestione S.c.a.r.l.4 Università di Brescia5 Center for Intelligent Drug Delivery and Sensing Using Microcontainers and Nanomechanics, Center, Technical University of Denmark
A method for the highly sensitive determination of the Young's modulus of TiO2 thin films exploiting the resonant frequency shift of a SU-8 polymer microcantilever (MC) is presented. Amorphous TiO2 films with different thickness ranging from 10 to 125 nm were grown at low temperature (90 °C) with subnanometer thickness resolution on SU-8 MC arrays by means of atomic layer deposition. The resonant frequencies of the MCs were measured before and after coating and the elastic moduli of the films were determined by a theoretical model developed for this purpose. The Young's modulus of thicker TiO2 films (>75 nm) was estimated to be about 110 GPa, this value being consistent with the value of amorphous TiO2. On the other hand we observed a marked decrease of the Young's modulus for TiO2 films with a thickness below 50 nm. This behavior was found not to be related to a decrease of the film mass density, but to surface effects according to theoretical predictions on size-dependent mechanical properties of nano- and microstructures.
Measurement Science and Technology, 2013, Vol 24, Issue 12