Lateral and depth profiles of nitrogen in laser-nitrided iron

The effect of nitrogen take-up upon irradiation of iron or steel with excimer laser pulses in air or nitrogen atmosphere is well established. However, the influence of the laser parameters (energy density, time structure, wavelength, number of pulses) on the nitrogen profile is not yet understood. We used Resonant Nuclear Reaction Analysis to investigate the evolution of nitrogen profiles with the number of pulses, To improve the accuracy of the nitrogen profiling, the laser irradiation was carried out in a N-15(2) enriched atmosphere. This allowed to detect also very low nitrogen concentrations that made it possible to follow the development of the nitrogen depth profiles from 1 to 64 pulses and to resolve the lateral nitrogen profiles across the laser spot. The laser induced surface morphology was observed with optical microscopy and a surface profilometer.