Investigation of AFM tip-assisted milling of ferroelectric thin films

Tip-assisted milling via atomic force microscopy (AFM) has been successfully utilised for nanomechanical machining of various materials including polymers, metals, silicon wafers, oxides, etc. due to advantages relating to the low cost, high accuracy, and ease of customised control. Ferroelectric materials, which represent candidate materials for a wide range of applications, have rarely been studied via this technique. AFM-based milling can be levereged to achieve high-resolution 3D tomography investigations of ferroelectric thin films by gradually removing thin (<1 nm) layers of the film. In addition, tip-assisted fabrication of ferroelectric nanostructures may offer advantages compared to established techniques such as focussed ion beam and bottom-up approaches in select cases where low damage and low cost modification of already-fabricated thin films is required, without the need for focussed ion beam facilities. Through a systematic investigation of a broad range of AFM parameters, we demonstrate that tip-milling provides a low-cost option to rapidly thin local regions of the film, as well as fabricate a range of different nanostructures, with aspect ratios limited by the tip profile and stiffness.