Picosecond pulse laser ablation of yttria-stabilized zirconia from kilohertz to megahertz repetition rates

Abstract

Thin films of yttria stabilized zirconia were deposited onto silicon substrates using high repetition rate picosecond pulse lasers. The applied lasers covered the repetition rate range from 10 kHz to 4 MHz. We found that the laser pulse overlapping which results from increased repetition rates led to considerable changes in the ablation process. Defect formation and local heating lead to lower ablation thresholds and, with sufficiently high repetition rates, to melting of the target and even to thermal evaporation. We found that yttria-stabilized zirconia (YSZ) films deposited with picosecond pulses at 1064 nm wavelength below repetition rates of 2 MHz have rough, nanostructured morphology and the same atomic ratio of yttrium and zirconium as the target. Films deposited with 2 MHz and higher repetition rates with high number of overlapping pulses are very smooth, but are yttrium deficient, providing evidence of the importance of the thermal processes.