Multiple nanoscale parallel grooves formed on Si3N4/TiC ceramic by femtosecond pulsed laser

Abstract

Multiple nanoscale parallel grooves were induced on Si3N4/TiC ceramic by a femtosecond pulsed laser with a pulse width of 120fs, wavelength of 800nm and repetition rate of 1000Hz. Pulse energy, scanning speed and the number of overscans were studied for the formation of regular parallel grooves. The evolution of surface morphology, ablation dimension and surface roughness with different processing parameters was measured by scanning electron microscope (SEM), atomic force microscope (AFM) and white light interferometer. The results show that the uniform multiple nanoscale parallel grooves are obtained by optimizing the pulse energy, scanning speed and number of overscans. The optimum parameters are 2.5μJ pulse energy and 130μm/s scanning speed with 1 overscan. At a constant scanning speed of 130μm/s, the period of the parallel grooves stays relatively constant with increasing pulse energy, fluctuating around 600nm, which is smaller than the laser wavelength. Additionally, the period was found to increase in a roughly linear fashion with increasing scanning speed. The depth of grooves increases with the increasing pulse energy and decreasing scanning speed; the surface roughness increases with the increasing pulse energy, decreasing scanning speed and increasing number of overscans. Meanwhile, the formation mechanism of laser-induced multiple nanoscale parallel grooves on the Si3N4/TiC ceramic surface was discussed.