Growth of surface structures on titanium through pulsed Nd:YAG laser irradiation in vacuum

Abstract

The formation of specific surface structures as a result of multi-pulse, high repetition rate Nd:YAG ( λ=1.064 μm, τ∼300 ns, ν=30 kHz) laser irradiation of Ti targets in vacuum is reported. The experiments are performed at laser intensity levels below the melting threshold of Ti for single laser pulse irradiation. An analysis of the early stage of surface transformation as well as of the further structure development by cumulative laser irradiation is done. A number of consecutive laser pulses are necessary to initiate the formation of the surface micro-structures. The process continues with the next laser pulses and the surface roughness increases. However, a change to a smooth, dendritic surface morphology takes place after a certain number of pulses. The irradiated areas are analysed by profilometry and scanning electron microscopy (SEM). The main physical phenomena implied in the laser induced surface microrelief development are discussed.