Determination of the polymeric thin film thickness by energy dispersive X-ray fluorescence and multivariate analysis

The objective of this work was to investigate the potential of energy dispersive X-ray fluorescence spectrometry for polymeric thin film thickness measurements using univariate and multivariate statistical tools. To this end, nine polymeric films 1.5 to 7.6 μm thick with different composition were used for calibration and validation purposes. The univariate approach was not suitable as thickness measurement strategy, because the coefficient of determination (R²) between the Rh-Kα Compton (18.54-19.83 keV) counting rate and the thin film thickness was estimated as 0.873 (n = 9). Even lower R² values were estimated for other X-ray spectral regions. On the other hand, the multivariate approach proved to be appropriated for the polymeric thin film thickness measurement, presenting satisfactory R² values (0.993-0.998; n = 8), precision (4%) and recovery (97%). The scanning electron microscopy was employed for validation of the proposed multivariate strategy. One can concluded that we show that the energy dispersive X-ray fluorescence using multivariate approach is a powerful non-destructive tool to measure the polymeric thin film thickness.