The automation of robust interatomic-force measurements

Interatomic-force measurements are regularly performed using frequency-modulation atomic force microscopy. This requires conversion of the observed shift in the resonant frequency of a force-sensing cantilever to the actual force experienced by its tip. Recently, Sader et al. [Nat. Nanotechnol. 13, 1088 (2018)] showed that this force conversion can be unreliable and proposed the inflection point test to identify valid and robust force data. Efficient and user-friendly algorithms are required for its routine practical implementation, which currently do not exist. Here, we (1) advance the theoretical framework of the inflection point test, (2) develop the required efficient algorithms for its complete automation, and (3) demonstrate the utility of this automation by studying two experimental datasets, in ultrahigh vacuum and liquid. The principal outcome of this report is the development of user-friendly software that integrates this automation with a standard force conversion methodology. This software provides the enabling technology for practitioners to now seamlessly perform robust nanoscale and interatomic-force measurements.