Ar ion laser-assisted chemical etching of molybdenum foils in air

Abstract

Ar ion laser-assisted chemical etching of Mo foils in air is reported. Etching occurred due to local heating by the focused laser beam which induced the Mo oxidation to form the volatile MoO3 at the elevated sample temperature. Holes and slots with slightly tapered walls and a minimum hole diameter of less than 10 μm could be etched in 25-, 50-, and 150-μm-thick foils. The hole diameters increased with increasing laser power and at any given laser power they decreased with increasing sample thickness. Etch-rate measurements as a function of the laser power were performed with static and scanned samples. Threshold powers for etching through the Mo foils were found. They increased with increasing sample thickness. Above these thresholds the etch rates increased rapidly with increasing laser power and rates as high as dz/dt=50 μm/s in the static mode and dV/dt=20×50×300 μm3/s in the scanning mode were obtained in a 50-μm-thick Mo foil under 10-W laser irradiation. Average sample temperatures as functions of the laser power in the scanning mode of operation where thermal equilibrium exists were measured by the use of optical pyrometry. A model which relates the laser power to the etch rate and temperature of the sample is presented and tested for agreement with the experimental results.