Angle-resolved laser-induced breakdown spectrometry for depth profiling ofcoated materials

The combination of angle-resolved laser ablation with the use of a collimat ed beam is presented as a new approach to increase the depth-resolved capab ilities of laser-induced breakdown spectrometry (LIBS). The effect of beam conditioning and the reduction of the effective sampling depth due to the a ngular dependence of laser ablation allow ablation rates lower than 2 nm/pu lse for coated materials (Sn-coated steels and Cr-coated samples). Spectral information is obtained on a single-laser-shot basis. The effect of incide nce angle has been examined from differentiated emission profiles, demonstr ating the beneficial effect of working at incidence different from normal. A compromise between depth resolution and emission signal must be found at large angles due to the lower irradiance resulting from the increase in bea m size at the interface for large angles of incidence. A comparison of the proposed approach with the analysis provided by a commercial glow-discharge device [glow discharge optical emission spectroscopy (GD-OES)] demonstrate d quite satisfactory results.