MELTING AND SURFACE DEFORMATION IN PULSED LASER SURFACE MICRO-MODIFICATION OF NIP DISKS

摘要

The nanosecond pulsed laser-induced transient melting and miniature surface deformation of Ni-P hard disk substrates has been investigated experimentally. A photothermal displacement method has been developed to detect the transient melting and surface deformation process with nanosecond time resolution. The deflection signals show the variation of the feature shape in response to different pulse energies of the near-IR pulsed nanosecond heating laser beam. A laser flash photography system is also developed to visualize the growth dynamics of the entire feature with nanosecond time resolution and sub-micron spatial resolution. The feature formation is mainly driven by surface tension, which depends not only on the surface temperature, but also on the surfactant concentration. Competition between the thermocapillarity and a surfactant concentration effect is revealed in the course of the bump formation process. Smaller features with diameters of 5 pm are obtained by using visible pulsed laser radiation. On-line monitoring of the transient growth process of such small features is achieved by a new laser flash deflection microscope.