UV Nd:YAG laser ablation of copper: chemical states in both crater and halo studied by XPS

Laser ablation of pure copper was performed using a pulsed Nd:YAG laser operating at 355 nm in air. Oxide nanoparticles redeposited near the edge of the crater results in the formation of the halo. Chemical states in both crater and halo were measured by X-ray photoelectron spectroscopy (XPS). After UV laser ablation, there are an obvious shoulder around 934.4 eV and a shake up satellite around 942.5 eV for the Cu 2p3/2 spectra in both crater and halo. Deconvoluting the Cu 2p3/2 spectra, a component was detected at 933.7 eV corresponding to CuO in both crater and halo as expected. Also, another component at 935.1 eV can be assigned to Cu(OH)2. The formation of CuO and Cu(OH)2 is probably due to the reactions of copper with O2 and water vapor in air. This suggest that the ablation atmosphere plays an important role for the formation of chemical species in both crater and halo. Moreover, an enhanced oxidation in the halo was found at higher fluence: the FWHM of the Cu 2p3/2 spectra and the peak areas of CuO and Cu(OH)2 were significantly higher than those in the crater. This is probably due to the formation of the laser-induced plasma. In addition, peak areas of CuO and Cu(OH)2 in the halo markedly increase with increasing the laser fluence.