Thermal and ambient-induced deflections of scanning force microscope cantilevers

TLDR

Scanning force microscope cantilevers with metal coating exhibit deflection that is strongly affected by thermal heating, relative humidity, and vapor adsorption, with laser‑induced drift and a linear humidity dependence when thermally stabilized. The study proposes using the cantilever’s deflection and resonance‑frequency shifts caused by vapor adsorption as the basis for new chemical sensors. Adsorbate mass can be quantified with picogram resolution by measuring shifts in the cantilever’s resonance frequency.

Abstract

The deflection of scanning force microscope cantilevers, metal coated on one side, is significantly influenced by both thermal heating and variations in relative humidity. For constant relative humidity, the deflection of the cantilever drifts due to laser heating and eventually reaches a steady-state value. For a thermally stabilized cantilever, the deflection varies linearly with relative humidity. Exposure to other vapors, such as mercury, changes the inherent deflection of the cantilever. Relative amounts of adsorbates on the cantilever can be estimated from shifts in the cantilever resonance frequency with picogram mass resolution. The cantilever deflection as well as changes in resonance frequency due to vapor adsorption can be used as basis for novel chemical sensors.