Investigation of adsorption and absorption-induced stresses using microcantilever sensors

The interaction between a vapor and a thin film adsorbed on one side of a b imaterial microcantilever produces differential stress, resulting in readil y measurable curvatures of the cantilever structure. Depending upon the sys tem studied, there exist two types of gas-solid interaction: bulk-like abso rption and surface-like adsorption. The absorption of hydrogen into palladi um results in film expansion whose magnitude is governed by hydrogen partia l pressure. The bending of a bimaterial microcantilever (palladium/silicon) due to hydrogen absorption depends on the thickness of the palladium film and is reversible but rate limited by a surface barrier. In contrast, the s tress induced by adsorption of mercury onto a bimaterial (gold/silicon) can tilever is irreversible at room temperature, is rate limited by surface cov erage, and is independent of the gold-film thickness. (C) 2001 American Ins titute of Physics.