Measurements of photoconductive switches with an ultrafast scanning tunneling microscope

We present experimental results of time-resolved signals of photoconductive (PC) switches with an ultrafast scanning tunneling microscope, which combines ultrashort laser techniques with scanning tunneling microscope (STM) to obtain simultaneous high temporal and spatial resolution. The picosecond electrical transients were generated by optically exciting the photoconductive switch between a high-speed coplanar strip transmission lines. The measured PC switch demonstrated a linear relation between the amplitudes of the time-resolved pulse signals and the photoconductive currents as well as a linear relation between the amplitudes of the signals and the bias voltage applied to the PC switch. The resolved transient signal in contact mode showed a FWHM of 3.2 ps, and the transient signals in non-contact mode were from the capacitive coupling between the tip and the coplanar transmission line.