Imaging ultrafast dynamics on the nanoscale with THz-STM

The ability to directly image ultrafast phenomena with nanometer spatial resolution is essential to our understanding of local excitation dynamics in nanomaterials and devices. We have developed a new approach to ultrafast scanning tunneling microscopy (STM) that couples terahertz (THz) pulses to the scanning tip of a STM. We have used THz-STM under ambient lab conditions to image ultrafast charging dynamics of a single InAs nanodot on GaAs with 0.5 ps time resolution and 2 nm spatial resolution. We are currently developing THz-STM for operation in ultrahigh vacuum with the goal of imaging ultrafast dynamics on surfaces with atomic resolution.