C. Li, C. Phillips
Bruker Nano Surfaces and Metrology,
Keywords: AFM-IR, correlative property
Summary:Chemical identification on the nanoscale is a long sought after capability from the inception of AFM. AFM-IR has proven to be uniquely successful in achieving this among all other attempts. It uses a mid-IR laser shining at the AFM tip to obtain IR spectra correlated with conventional FTIR spectroscopy. However, a single data set rarely tells the full story and multiplexed analysis is essential to fully understand a material. Using a Dimension IconIR system with MIROView (microscope image registration and overlay) it is possible to return to the exact same position on a sample when changing probes, enabling extensive multimodal analysis. Data on a two-component polymer sample PS-LDPE comprising polystyrene and polyethylene reveals nanoIR spectra that correlate well with FTIR, while nanoIR maps at different IR wavenumbers provide the distribution of each component. Further, they are directly correlated at the nanometer level through PeakForce QNM elastic modulus and adhesion maps, as well as work function (surface potential) and dielectric maps with FM-KPFM (frequency-modulated Kelvin probe force microscopy). Many of the properties can be conveniently obtained simultaneously, while others are preferably obtained in a colocalized manner with the optimal probe choice and parameter settings for each. Data on real-world industrial samples including SBR (styrene-butadiene rubber) with carbon-black additives for car tires, and lithium ion battery electrodes exemplify how ratio-map and multimodal property mapping unravel information not seen through one technique alone.