Towards Scanning Tunneling Microscopy studies of ultrafast laser damage*

 Nowadays, femtosecond lasers are widely used, because of their short pulse duration which can be used to study reactions at the atomic level. Based on former thermal ablation research using femtosecond lasers, we start to explore surface morphology caused by femtosecond laser damage at the atomic scale using Scanning Tunneling Microscopy (STM). We perform atomic-resolution STM in Ultrahigh vacuum (UHV) which means there is a protective environment for the surface, especially for semiconductor surfaces which are more easily contaminated by air. 

 Challenges for combining a femtosecond laser with STM are the timescale resolution for material dynamics and locating the laser damage spot due to the STM’s sample rate and limited scan area. 

  In our recent work, we designed a custom UHV chamber, which can realize sputtering and annealing with our self-built electron-beam-heater (eheater) at one spot. Additionally, we designed a mount for an in-situ objective lens to tightly focus light onto the sample. To test the STM capability for locating laser damage areas, we have performed initial studies on Si(100) substrates, cleaned by immersion in HF. STM images of the control Si(100) sample show an atomically flat surface with a low coverage of surface contamination. These data will be compared with STM images of a laser-irradiated sample to identify laser damage areas.