Surface structuring of titanium under pulsed Nd:YAG laser irradiation

Multi-pulse Nd:YAG (lambda=1.064 mum, tausimilar to100-300 ns, v=1-30 kHz) laser irradiation of titanium at low intensities, below or in some cases just above the single-pulse melting threshold of titanium led to the development of a large variety of surface structures. The morphology evolution was strongly influenced by the number of the subsequent laser pulses as well as the ambient gas. In air the formation of crown-, or dome-shaped micro-structures was evidenced. In vacuum the micro-relief is characterised by smooth polyhedral structures developing in the surface plane. In nitrogen the cumulative laser irradiation induced the growth of uniformly distributed micro-column arrays with a high aspect ratio, protruding above the non-irradiated target surface. Morphological, structural and chemical characterisations of the laser treated surface areas were performed by scanning electron microscopy, X-ray diffractometry, Raman spectroscopy, and wavelength dispersive X-ray spectroscopy. The growth mechanisms which lead to the formation of the specific structures are investigated. Moreover, the potential applications of the laser processed surfaces are discussed.