Role of surface morphology on desorption kinetics of water molecules from uncoated silicon microcantilever

Desorption kinetics of water molecules from uncoated silicon microcantilevers (MC) is studied, by measuring resonance frequency, with Relative Humidity (RH) varying in the range of 50-15%. Shift in resonance frequency of MC was used to estimate the desorbed mass, which over-estimated the number of monolayers desorbed between the RH values of interest and followed a single exponential decay model. Moreover, desorption rate is found to be higher for RH > 25% compared to RH < 25%. However, the Q factor describing the sensitivity of the MC and computed from the resonance spectrum is found to decrease by ∼3%. These results are explained on the basis of complex surface coverage during desorption of water molecules and is supported by topographical image of MC surface clearly showing quasi 3D nanofeatures. The bending of uncoated MC during desorption, due to the generation of differential surface stress, further confirms the presence of these surface features.