In-situ scanning tunneling microscopy of ultrafast laser damage on Si (100) surface in ultra-high vacuum

A novel instrumentation design and operation to study ultrafast laser damage with atomic scale characterization by scanning tunneling microscopy is described here. The STM system operates in an ultrahigh vacuum chamber, fitted with an in situ objective allowing for tight focusing of laser excitation onto the sample. A combination of in situ and ex situ laser machining is used to define fiducial registry markers that help identify the overlap region for the optical excitation and STM scanning, aided by simultaneous confocal imaging and far-field cameras. We report initial measurements of laser damage on silicon in UHV with 10 pulses (77 fs compressed width, 0.67J/cm2 peak fluence) from a 1030nm Yb:KGW laser. STM imaging of damage sites show several characteristic regions with sharply defined boundaries determined by underlying damage thresholds, including an ablation crater and the beginnings of periodic surface structures.