  The new generation of strained silicon nitride resonators harbors great
promise for scanning force microscopy, especially when combined with the
extensive toolbox of cavity optomechanics. However, accessing a mechanical
resonator inside an optical cavity with a scanning tip is challenging. Here, we
experimentally demonstrate a cavity-based scanning force microscope based on a
silicon nitride membrane sensor. We overcome geometric constraints by making
use of the extended nature of the mechanical resonator normal modes, which
allows us to spatially separate the scanning and readout sites of the membrane.
Our microscope is geared towards low-temperature applications in the
zeptonewton regime, such as nanoscale nuclear spin detection and imaging.
