Dynamic and Static Manifestation of Molecular Absorption in Thin Films Probed by a Microcantilever

Mechanical resonators shaped like microcantilevers have been demonstrated as a platform for very sensitive detection of chemical and biological analytes. However, their use as an analytical tool requires fundamental understanding of the molecular absorption-induced effects in the static and dynamic sensor response. The effect of absorption-induced surface stress on the microcantilever response is here investigated using palladium hydride formation. It is shown that the dynamic and static responses of the cantilever monitored simultaneously exhibit excellent correlation with the crystalline phases of hydride formation. However, the resonance frequency shifts and quasistatic bending are observed to be independent during the solid solution phase. Importantly, absorption-induced changes in the elastic parameters of the palladium film are found to play a dominant role in the static and dynamic response. The presented results help in discerning between changes in swelling and elastic modulus that control the cantilever response as well as the relationships between these parameters.