Frequency-based detection of chemical expansion dynamics in thin films

Abstract

Current techniques for measuring chemical expansion in thin film structures are too slow, too imprecise, or require synchrotrons. In contrast, nanoscale electrochemomechanical spectroscopy (NECS) can be used to make nanoscale measurements at time scales of seconds with simple contact or non-contact sensors. In a NECS measurement, a sample, such as thin-film oxide structure, is subjected to a temporally modulated stimulus, such as a sinusoidally alternating voltage. The stimulus causes the sample to expand, contract, deflect, or otherwise deform. A sensor, such as a contact probe or optical sensor, produces an electrical signal in response to this deformation that is correlated with the temporal modulation of the stimulus. Because the stimulus and deformation are correlated, the temporal modulation of the stimulus can be used to filter the deformation signal produced by the sensor, producing a precise, sensitive measurement of the deformation.