The evolution of nano-precursors at film-substrate interface under nanosecond laser irradiation

Abstract

Functionally graded layers (FGLs) with quasi-continuous interfaces are deposited by ion-beam sputtering (IBS). The laser-induced damage threshold (LIDT) of FGLs is more than twice that of film-substrate interface. Basic time-resolved microscope system is designed to capture the ultrafast dynamics process of nanosecond laser-induced damage in FGLs and film-substrate interface, respectively. Materials ejections and damages craters at the film-substrate interface are observed by focused ion beam (FIB) microscope. The primary sources leading to low LIDTs are the nano-precursors distributed among the subsurface. The nano-precursors formed by the metastable chemical structures (FeOx and CeSixOy) are agglomeratedand grown during migration process because of sputtered atomic collision motion. High normalized electric field intensity enhancement in the subsurface region (about 275 nm) is considered to be an important factor that promotes absorption of the nano-precursors. The experiment first provides a sufficient experimental observation of the laser-induced damage process inside films which deepens people’s understanding of nano-precusors and lays a solid basis for solving the damage of film-substrate interface.