NANOMETRIC RANGE DEPTH-RESOLVED ANALYSIS OF COATED-STEELS USING LASER-INDUCED BREAKDOWN SPECTROMETRY WITH A 308 NM COLLIMATED BEAM

The spatial profile from an XeCl excimer laser was modified using a si mple two-lenses telescope to generate a flat energy-profile beam that impinged a layered sample (a Zn-coated steel) without beam conditionin g. The irradiance obtained (about 10(7) W cm(-2)) was high enough to v aporize the target, to cause plasma formation and to allow atomic emis sion spectrometry with acceptable signal-to-noise ratio. Modification in beam energy distribution resulted in flat ablated profiles and impr oved depth-resolution up to the few nm pulse(-1) range was attained. T he net intensity areas were transformed into normalized values leading to plots in excellent agreement with those provided by commercial dep th-resolved analysis instruments.