Comparison of microcantilever Hg sensing behavior with thermal higher order modes for as-deposited sputtered and thermally evaporated Au films

Abstract

As-deposited sputtered and thermally evaporated Au films are studied for Hg sensing with rectangular Si microcantilevers. Microcantilever deflection and frequency shifts in the first four thermally induced flexural modes are measured for each type of Au film as a function of Hg exposure. All thermally induced higher order modes show shifts in their frequencies for Hg exposures when the Au is sputter deposited whereas typically only the third and fourth order modes show frequency shifts when the Au is thermally evaporated. A technique is employed in order to vary Au coverage along a microcantilever surface. The shifts in the thermal microcantilever modes upon Hg exposure are thus studied as a function of fractional Au coverage along the microcantilever surface. Microcantilevers having various coverages of either sputtered or thermally evaporated Au films show a distinct response to Hg exposure. From both the deflection and spectral shifts it is observed that sputtered films give better response to Hg than thermally evaporated films when the Au is coated along the entire length of the microcantilever.