Sensitive determination of the Young's modulus of thin films by polymeric microcantilevers

Paolo Colombi, Paolo Bergese, Elza Bontempi, Laura Borgese, Stefania Federici, Stephan Sylvest Keller, Anja Boisen, Laura Eleonora Depero

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    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.

    Original languageEnglish
    JournalMeasurement Science and Technology
    Issue number12
    Pages (from-to)125603
    Publication statusPublished - 2013

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