Non-thermal effects in laser assisted oxidation of thin metal films

We study the oxidation in air of thin films exposed to laser radiation. Films 2000 A thick of Cd and Cu deposited on glass are irradiated with an Ar+ laser at beam powers in the 2-5W range. The kinetics of oxidation are monitored by R and T measurements using a HeNe probe, where the reflected beam displays minima due to destructive interference in the oxide layer. We show that complete oxidation occurs in seconds at temperature around 300-4000C and, by beam chopping experiments, demonstrate that the high oxidation rate cannot be explained by the heating effect of the laser beam alone. Other possible mechanisms are discussed