Abstract
The experimental study of damage to tungsten (W), molybdenum (Mo), and silicon carbide (SiC) surfaces induced by focused extreme ultraviolet laser radiation (lambda similar to 47 nm/similar to 1.5 ns/21-40 mu J) is presented. It was found that W and Mo behaved similarly: during the first shot, the damaged area is covered by melted and re-solidified material, in which circular holes appear residua of just opened pores/bubbles, from which pressurized gas/vapors escaped.
Next cracks and ruptures appear and the W has a tendency to delaminate its surface layer. Contrary, single-crystalline SiC has negligible porosity and sublimates; therefore, no escape of "pressurized" gas and no accompanying effects take place.
Moreover, SiC at sublimating temperature decomposes to elements; therefore, the smooth crater morphology can be related to local laser energy density above ablation threshold. When more shots are accumulated, in all three investigated materials, the crater depth increases non-linearly with number of these shots.
The surface morphology was investigated by an atomic force microscope, the surface structure was imaged by a scanning electron microscope (SEM), and the structure below the surface was visualized by SEM directed into a trench that is milled by focused ion beam. Additionally, structural changes in SiC were revealed by Raman spectroscopy.