Fabrication of a quartz tuning-fork probe with a sharp tip for AFM systems

A quartz tuning-fork probe can oscillate and can be used to detect an atomic force between the tip and the sample surface due to the piezoelectric property of quartz. We have designed a tuning-fork structure with a large spring constant of 50 N/m to prevent probe adsorption to the sample surface. We developed a fabrication process to integrate the tuning-fork probe with the tip structure by applying two different processes: anisotropic wet etching and a focused ion beam (FIB) system. The length, thickness, and width of a beam of the fabricated tuning-fork were 1500 μm, 100 μm, and 100 μm, respectively. The height of the tip formed at the end of one beam was less than 6 μm. We also evaluated the self-oscillation properties of the fabricated quartz tuning-fork in two vibration modes – in-phase and anti-phase – and experimentally obtained a significantly improved quality (Q) factor of 5247 in the anti-phase mode. The fabricated tuning-fork was able to detect a 100-nm-high step by using the self-oscillation property in tapping-mode atomic force microscopy (AFM).