Analysis of Multi-elemental Thin Films via Calibration-Free Laser-Induced Breakdown Spectroscopy

Elemental analyses of thin films with complex composition are challenging as the standard analytical techniques based on measurement calibration are difficult to apply. We show that calibration-free laser-induced breakdown spectroscopy (LIBS) presents a powerful solution, enabling quantitative analyses of multielemental thin films with analytical performances better than those obtained with other techniques. The demonstration is given for a nickel-chromium-molybdenum alloy film of 150 nm thickness that was produced by pulsed laser deposition. The LIBS spectra were recorded under experimental conditions that enable simple and accurate modeling of plasma emission. Thus, a calibration-free approach based on the calculation of the spectral radiance of a uniform plasma in local thermodynamic equilibrium was applied to deduce the elemental composition. Supported by analyses via Rutherford backscattering spectrometry and energy-dispersive X-ray spectroscopy, the LIBS measurements evidence nonstoichiometric mass transfer of the alloy during the thin-film deposition process. This technique could be used even for thinner films, provided that the film-composing elements are not present in the substrate.