A super high aspect ratio atomic force microscopy probe for accurate topography and surface tension measurement

This work presents a methodology for fabricating high aspect ratio atomic force microscopy (HAR-AFM) probes and its applications in high aspect ratio nanostructure topography and liquid surface tension measurement. The focus ion beam (FIB) precisely positions and grows HAR tips of controlled diameter, height, and tilting angle, which can fabricate robust, repeatable, and multi-angled HAR tips. Through ion beam etching, the probe tip was further sharpened, which helped to achieve a high resolution of topography scanning. We achieved HAR probes fabrication with an aspect ratio of 5–40, a maximum height of 20 µm, a minimum diameter of less than 100 nm, and a tilting angle range of 0–15°. The actual superior performance of FIB-fabricated probes is demonstrated by observing the topography of nano-trenches by HAR AFM probes and compared with commercial pyramid-shaped AFM probes. An additional application is demonstrated that surface tension of micron/nanodroplets could be measured accurately by HAR AFM probes.