Ultraviolet laser ablation of benzene monolayers.

Abstract

Etching by high-fluence excimer laser pulses has been studied by measuring laser-induced fluorescence (LIF) from atoms and diatomic molecules in the etch plume. The present work deals with the UV ablation and decomposition of benzene monolayers frozen onto sapphire surfaces. The energies involved are similar to those that result when benzene is dissociated as a low-density (approx. 1012 cm-3) vapor. Also, there are only minor changes whether one deals with C6H6 or C6D6. It is concluded that both surface monolayers and gas phase benzene molecules are sensitive to dissociation into C2 by 193-nm radiation. The dissociation proceeds by a 3hν process. The observation that the C2 energies are the same regardless of the starting physical state indicates that the last step of photodissociation occurs above the substrate when starting with a frozen monolayer.