Mechanistic insight in the laser-pulse sputtering of polymers by combined photographiy and gas-dynamic analysis

Abstract

The gas-dynamic effects which are so prominent in laser-pulse sputtering have three limiting cases. The one limit could be described as an unsteady adiabatic expansion (UAE) due to gas which escapes from a finite reservoir (“outflow” model). The second limit is that the particles are released from target surface, form a Knudsen layer (KI,), and then enter a UAE (“KL-UAE” model). Closely related is the third limiting case, which allows for condensation at the surface (“condensation” model). Explicit photographs suggest that either the KI: UAE or the condensation model is relevant to laser-pulse sputtering of the polymer polymethylmcthacrylate (PMMA).