Sputtering and amorphization of crystalline semiconductors by Nanodroplet Bombardment

In this review we expose how Nanodroplet Bombardment of surfaces by charged particles produced through electrospray atomization offers unparalleled opportunities for surface engineering of chemically inert crystalline materials. The sputtering yields and rates are comparable or higher than reactive etching techniques and significantly higher than other physical sputtering systems. Moreover, bombardment can amorphatize a thin layer of the target. The imposed physical characteristics of the electrospray, droplet diameter, molecular mass of the spray, and kinetic energy will determine the sputtering and amorphization efficiency, and the topography of the processed target. Molecular dynamics studies have clarified the mechanisms of both processes; amorphous layers appear due to ultra-fast quenching of melted target pools around the impact area while sputtering is driven by a combination of collision cascades, thermal evaporation, and, for large and fast projectiles, of hydrodynamic forces.