Physisorption on Nanomechanical Resonators: The Overlooked Influence of Trace Moisture

Short gas pulses introduced in a vacuum chamber have long been utilized to showcase the ultra-low mass resolutions achievable with nanomechanical resonators. The resonance frequency shifts are used as evidence of gas adsorption. However, there is very little clarity as to what exactly is adsorbing on to the resonators. We demonstrate that the physisorption of gases on cantilevers is predominantly the effect of moisture content that is present even in ultra-high purity gases. The experimental work is performed at low temperatures and in a high vacuum and is supported by theoretical calculations and simulation.