  We developed a time-resolved force microscopy technique by integrating atomic
force microscopy using a tuning-fork-type cantilever with the delay time
modulation method for optical pump-probe light. We successfully measured the
dynamics of surface recombination and diffusion of photoexcited carriers in
bulk WSe2, which is challenging owing to the effect of tunneling current in
time-resolved scanning tunneling microscopy. The obtained results were
comprehensively explained with the model based on the dipole-dipole interaction
induced by photo illumination.
