Gas cluster etching for the universal preparation of polymer composites for nano chemical and mechanical analysis with AFM

Atomic force microscopy (AFM) based techniques that probe nanomechanical and nanochemical features are valuable tools for studying composite surfaces at high-resolution. However, the application of AFM, particularly at resolutions less than 50 nm per pixel, is limited to sample surfaces that are smooth relative to the tip dimensions and damage-free. As a result, high-resolution AFM is limited in technologically relevant polymer composite systems where current sample preparation techniques can fail to produce the necessary pristine surfaces. Here, we apply gas cluster ion beam (GCIB) etching to prepare composite materials for nanomechanical and nanochemical analysis. We demonstrate that the GCIB can effectively remove material and produce damage free surfaces for composites comprised of PMMA or PS confined in the 7 nm diameter pores of an organosilicate matrix. AFM-IR measurements on the etched region indicate a high degree of hydrogen bonding between the carbonyl groups of the confined PMMA and the hydroxyl groups on the pore walls, while maps of loss tangent can identify the 7 nm polymer domains within the organosilicate matrix. This work demonstrates that GCIB is an effective tool for nanocomposite surface preparation and could enable a new range of materials to be studied with AFM at high resolution.