Fabrication and evaluation of single-crystal silicon cantilevers with ultra-low spring constants

Abstract

We successfully fabricated single-crystal silicon cantilevers with spring constants as low as 10−5 N m−1 for use in magnetic resonance force microscopy applications. The fabricated ultra-thin silicon cantilevers had thicknesses ranging from 200 to 400 nm, lengths ranging from 340 to 450 µm and a width of 5 µm. We characterized their force sensitivity in the vacuum range from ambient pressure to 10−3 Pa and the temperature range from 15 to 300 K. A minimum value is observed for the internal friction, Q−1, at 160 K, which corresponds to an activation peak due to phonon scattering by atomic-scale defects. The best force sensitivity was achieved at 20 K, where it was increased by a factor of 10 as compared to that observed at room temperature.