Fabrication of tuning-fork based AFM and STM tungsten probe

We compare the sharpness of tungsten probe tips produced by the single-step and two-step dynamic electrochemical etching processes. A small radius of curvature (RoC) of 25 nm or less was routinely obtained when the two-step electrochemical etching (TEE) process was adopted, while the smallest achievable RoC was ~10 nm, rendering it suitable for atomic force microscopy (AFM) or scanning tunneling microscopy (STM) applications.