Fluence-independent range of surface roughening within the Gaussian-shaped prole of a low-intensity ultrashort laser

Abstract

In the pursuit to master the manipulation of matter at the nanoscale, we investigate the local eects of irradiating a Cu(511) surface with a Gaussian-shaped laser spot lasting 50 fs at a power well beneath the ablation threshold. Irradiation results in the formation of adatom and vacancy clusters. Such changes exhibit signicant variation based on their position within the laser spot because of a strong dependence on the locally absorbed uence, limiting the precision of nanoscale modications induced by laser irradiation. We delve into these critical nanoscale transformations across the microscale using the nanoscale resolution of low-temperature scanning tunneling microscopy. We identify a broad uence range, where the number of defects stays approximately constant. Our results open a route to create dened nanostructures across a larger spatial range despite the inevitable uence variations across a Gaussian-shaped laser spot.