Laser ablation of graphite at 355 nm: cluster formation and plume propagation

Abstract

Ablation dynamics of C n + ions ejected from a 355-nm laser ablation of graphite target in vacuum has been investigated by time-of-flight (TOF) mass spectrometry. At 0.5 J/cm 2 laser fluence, the larger cluster ions are predominantly produced. With increasing laser fluence, however, the maximum size distribution moves toward small cluster ions. A strong nonlinear dependence of the amount of desorbed C n + cluster ions on laser fluence is observed under moderate laser fluence conditions (≤1 J/cm 2). This is interpreted by the mechanism that C n + ions are produced directly from the graphite via conversion of the multiphoton energy into thermal energy. The time resolved analysis of the ablated C + ions shows the two drift velocities with the fast and slow components. The result indicates that the ejecta emitted above the target surface separates into two components during plume propagation.