Depth-resolved analysis of multilayered samples by laser-induced breakdown spectrometry

The capability of laser-induced breakdown spectrometry (LIES) to resolve complex depth profiles is demonstrated. Electrolytically deposited brass samples were analyzed by monitoring the emission corresponding to Cr (357.8 nm), Ni (341.4 nm), Cu (327.4 nm) and Zn (334.5 nm). The nominal thickness of the layers was known, which permitted an estimate of the ablated mass in the range between 150 and 500 nm per pulse depending on the matrix and laser irradiance. Laser irradiance was varied by defocusing, and its effect on the depth-resolution of LIES was tested For comparison purposes, a commercial zinc-coated steel was also studied by following the Zn and Fe emission intensity depth profiles with a commercial glow-discharge optical emission spectrometry system to obtain information on the exact location of the Zn-Fe interface (12 mu m). The ablation rate in terms of ablated mass per pulse was found to be at the ng per pulse level and depended on the laser pulse irradiance.