# New Insights in the Ion Beam Sputtering Deposition of ZnO-Fluoropolymer Nanocomposites
## 3 Results and Discussion
### Surface Analytical Characterization  
X-Ray Photoelectron Spectroscopy (XPS) was systematically employed to characterize the surface chemical composition of the nanomaterials. Elemental quantification is summarized in Table 2 as a function of \(\phi\). On the one hand, the zinc and oxygen percentages increased with \(\phi\) and remained almost constant for \(\phi\geq 0.10\). A certain divergence with the results obtained for analogous Pd-CF\({}_{x}\) and Cu-CF\({}_{x}\) materials was noticed; in these previous studies, the surface atomic percentages of inorganic components increased systematically as a function of the metal loading [46; 14]. On the other hand, the fluorine percentage followed an opposite trend, decreasing noticeably at higher inorganic loadings [13; 14; 45; 46]. Polymer reticulation and defluorination were considered responsible for this experimental evidence. A detailed curve-fit procedure was applied to all high resolution regions for each value of \(\phi\). In the C1s region (Figure S2), six or seven photoelectron components were used to process the signal, whose position and relative abundances are listed in Table S1 and described in the corresponding text. A general inspection of the C1s spectra (Figure S2) indicated that the fluoropolymer matrix structure changed profoundly with \(\phi\). At \(\phi\) = 0.10 (Figure S2b) and \(\phi\) = 0.15 (Figure S2c), a shift towards lower BE values was found in the C1s spectra, probably due to a massive polymer defluorination and reticulation. Otherwise, ZnO-CF\({}_{x}\) materials with a low zinc oxide content (i.e., \(\phi\) = 0.05, Figure S2a) gave the typical C1s spectrum of a fluoropolymer [14] with a low branching degree. The F1s high \begin{table}
\begin{tabular}{c c c c c} \hline \(\phi\) & **Sample Region** & **\% F** & **\% Zn** & **F/Zn** \\ \hline \multirow{3}{*}{0.05} & Cluster & n.d. & n.d. & - \\ \cline{2-5}  & Background & n.d. & n.d. & - \\ \cline{2-5}  & Total & 7.2 & 0.2 & 36.0 \\ \hline \multirow{3}{*}{0.10} & Cluster & 2.0 & 0.6 & 3.3 \\ \cline{2-5}  & Background & 3.3 & 0.8 & 4.1 \\ \cline{2-5}  & Total & 3.4 & 0.8 & 4.2 \\ \hline \multirow{3}{*}{0.15} & Cluster & 2.4 & 1.7 & 1.4 \\ \cline{2-5}  & Background & 5.6 & 1.5 & 3.7 \\ \cline{2-5}  & Total & 5.3 & 1.5 & 3.5 \\ \hline \end{tabular}
\end{table} 
Table 1: energy dispersive X-ray (EDX) elemental analysis, as a function of the metal oxide volume fraction \(\phi\). Error is 0.4% in all cases. n.d. = not detectable. \begin{table}
\begin{tabular}{c c c c c} \hline \(\phi\) & **\% C** & **\% F** & **\% O** & **\% Zn** \\ \hline
0.05 & 46.3 \(\pm\) 0.3 & 3.4 \(\pm\) 0.2 & 51.6 \(\pm\) 0.4 & 1.4 \(\pm\) 0.2 \\
0.10 & 33.5 \(\pm\) 1.4 & 8.8 \(\pm\)0.2 & 43.6 \(\pm\) 0.8 & 14.2 \(\pm\) 0.4 \\
0.15 & 35.6 \(\pm\) 0.4 & 8.9 \(\pm\)0.2 & 40.9 \(\pm\) 0.2 & 14.1 \(\pm\) 0.5 \\ \hline \end{tabular}
\end{table} 
Table 2: ZnO-CF\({}_{x}\) surface elemental composition as a function of the metal oxide volume fraction \(\phi\). Errors are calculated as standard deviation on three replicates. resolution region (Figure 3) was curve-fitted, in all cases, with two components. The one on the right, centered at 684.8 \(\pm\) 0.2 eV, was attributed to inorganic fluoride (F\({}^{-}\)); this signal component grew with \(\phi\). The other one, at 688.8 \(\pm\) 0.2 eV, was attributed to organic fluorine (C-F), and its relative abundance decreased with increasing inorganic loading. Therefore, it could be inferred that the formation of inorganic fluoride was somehow related to the amount of inorganic phase in the composite thin film. Important information about zinc chemical speciation was obtained by the analysis of the Auger ZnL\({}_{3}\)M\({}_{45}\)M\({}_{45}\) region (Figure 4). The region was curve-fitted using two signal components, with a large FWHM (full width at half maximum) of 3.5 \(\pm\) 0.2 eV, and a Gaussian-Lorentzian ratio of 30.0 \(\pm\) 0.5.