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 mu m 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 (R-2) between the Rh-Ka Compton (18.54-19.83 keV) counting rate and the thin film thickness was estimated as 0.873 (n = 9). Even lower R-2 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 R-2 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.