Time-resolved scanning tunneling microscope light emission spectroscopy of Sb2Te3

We have successfully added ps temporal resolution to scanning tunneling microscope (STM) light emission spectroscopy. STM light emission spectra of Sb2Te3 were measured in the configuration that the tip sample gap of the STM is irradiated by a pair of pump and probe laser pulses with a duration less than 2 ps each, and were analyzed as a function of optical delay time between the pump and probe pulses. We found that the peak energy of the STM light emission, which is excited via electronic transitions of Sb2Te3 (Y. Uehara et al., , Solid State Commun., 149, 1902 (2009)), is shifted toward the higher energy side when the optical delay time is in the range between around 2 ps to 13 ps. This result demonstrates that the proposed method has temporal resolution of ps.