Chemical composition of dome-shaped structures grown on titanium by multi-pulse Nd:YAG laser irradiation

The specific dome-shaped structures were grown by multi-pulse Nd:YAG (l ¼ 1:064 mm, t ¼ 300 ns, and n ¼ 30 kHz) laser irradiation of titanium targets in air at atmospheric pressure. The laser intensity values were chosen below the single-laser-pulse melting threshold of titanium. The chemical composition of the structures was studied as a function of laser pulse number as well as laser intensity, both at the outer surface layer and in depth. Micro-Raman spectroscopy, Auger electron spectroscopy (AES), and wavelength dispersive X-ray spectroscopy (WDX) were used as diagnostic techniques. Morphological investigations were performed by scanning electron microscopy. The obtained results revealed a lower oxygen concentration in the centre of the structures as compared to the borders and a lower concentration on the surface than in the depth. Moreover, it was found that the stoichiometry of the formed TiO2 x oxides increases from the structures centre towards the border and from the surface towards the depth. # 2003 Elsevier B.V. All rights reserved.