6-MHz 2-N/m piezoresistive atomic-force-microscope cantilevers with INCISIVE tips

Abstract

Piezoresistive atomic-force-microscope (AFM) cantilevers with lengths of 10 μm, displacement sensitivities of (ΔR/R)/Å = 1.1 × 10 -5, displacement resolutions of 2 × 10 -3 Å/√Hz, mechanical response times of less than 90 ns, and stiffnesses of 2 N/m have been fabricated from a silicon-on-insulator (SOI) wafer using a novel frontside-only release process. To reduce mass, the cantilevers utilize novel inplane crystallographically defined silicon variable aspect-ratio (INCISIVE) tips with radius of curvature of 40 Å. The cantilevers have been used in an experimental AFM data-storage system to read back data with an areal density of 10 Gb/cm 2. Four-legged cantilevers with both imaging and thermomechanical surface modification capabilities have been used to write 2-Gb/cm 2 data at 50 kb/s on a spinning polycarbonate sample and to subsequently read the data. AFM imaging has been successfully demonstrated with the cantilevers. Some cantilever designs have sufficient displacement resolution to detect their own mechanical-thermal noise in air. The INCISIVE tips also have applications to other types of sensors. [271].