Multifrequency imaging in the intermittent contact mode of atomic force microscopy: Beyond phase imaging

The cantilever dynamics in single-frequency scanning probe microscopy (SPM) are undefined due to having only two output variables, which leads to poorly understood image contrast. To address this shortcoming, generalized phase imaging scanning probe microscopy (GP-SPM), based on broad band detection and multi-eigenmode operation, is developed and demonstrated on diamond nanoparticles with different functionalization layers. It is shown that rich information on tip-surface interactions can be acquired by separating the response amplitude, instant resonance frequency, and quality factor. The obtained data allow high-resolution imaging even in the ambient environment. By tuning the strength of tip-surface interaction, different surface functionalizations can be discerned. Resonance frequency mapping of nanodiamond particles functionalized with octadecylamine on a mica substrate is carried out by generalized phase scanning probe microscopy (GP-SPM). The method is based on broad band detection and multi-eigenmode operation. Information on tip-surface interactions can be acquired by separating the response amplitude, instant resonance frequency, and quality factor.