Investigations of holes machined by laser beam on Al and Cr thin films

Transmission and scanning electron microscopy studies of holes created by laser irradiation on Al and Cr films were carried out. The results showed that both films have the well-shaped round holes and that the peripheral regions form gentle swells for Al films and steep swells for Cr films. From the measurement of surface shape across the groove made by a laser beam the height of swells was nearly the same as the film thickness. It was also found that the swells are composed of large recrystallized grains, and that the effect of the existence of large grains on the recording characteristics is not so evident. The numerical analysis of temperature rise of the metal films was made using the finite difference method considering the phase transition of the film materials. Comparison of the temperature distributions with the experimental results revealed that the hole initiated by vaporization at the center of the melt expands outwards by the surface tension.