# New Insights in the Ion Beam Sputtering Deposition of ZnO-Fluoropolymer Nanocomposites
## 3 Results and Discussion
### Treatments in Deposition Chamber to Reduce Fluorides Content  
The first part of this work, which deals with the spectroscopic and morphological characterization of composite materials without post-deposition treatments, must be considered as the main focus of this paper. Despite the presence of inorganic fluorides, these materials are very useful in many other applications, ranging from catalytic de-polymerization processes [51] to the modification of paddings and mattresses not in direct contact with human skin. The aim of this paragraph is just to add a useful piece of information for those readers interested in the textile manufacturing application of composite materials, thus providing complimentary information to what we reported in [45]. As shown, samples with higher loadings had a significant atomic percentage of inorganic fluoride that was about 26% of the total fluorine. This evidence posed a significant drawback to the possibility of using these nanomaterials as antimicrobial coatings of industrial products (textiles, leather, etc. ), since ZnF\({}_{2}\) is an irritant for human skin [52]. Therefore, in order to remove inorganic fluoride from the composite films, sample treatments were here developed and optimized, either in the deposition step, or at the end of it. The presence of a metal oxide as the sputtering target leads to the preferential deposition of the metal, which has a higher vapor pressure compared to oxygen and is not lost in the gaseous form during the deposition. The presence of non-coordinated metal in the fluoropolymer matrix was held to be responsible for the extraction of fluorine from it (refer to previous paragraphs) with consequent high CF\({}_{x}\) cross-linking. Hence, the deposition of a nanocomposite film at \(\phi=0.15\) was carried out at room temperature using a combined flow of Ar and O\({}_{2}\) (2 sccm Ar + 0.5 sccm O\({}_{2}\)), instead of pure Ar for ZnO sputtering, during the entire IBS process. A post-deposition thermal treatment was implemented, as an alternative method, on samples at \(\phi=0.15\). At the end of a standard deposition, we proceeded to flush 5 sccm of O\({}_{2}\) in the IBS chamber for 10 m. After that, in the presence of the same gas, the temperature of the substrate holder was raised prior to 50 \({}^{\circ}\)C and then, with a step of 10 \({}^{\circ}\)C up to 100 \({}^{\circ}\)C, for 1 h. We choose not to exceed 100 \({}^{\circ}\)C because Teflon\({}^{\oplus}\)'s glass-transition temperature is 120 \({}^{\circ}\)C [53]. To test \begin{table}
\begin{tabular}{c c c} \hline \hline \(\phi\) & \(\theta\)**Advancing/Degree** & \(\theta\)**Receding/Degree** \\ \hline
0.05 & \(112\pm 1\) & \(73\pm 1\) \\
0.10 & \(108\pm 1\) & \(28\pm 2\) \\
0.15 & \(111\pm 1\) & \(28\pm 1\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Dynamic water contact angles as a function of \(\phi\). the efficacy of these two new protocols, samples were immediately subjected to a surface chemical composition analysis by parallel angle-resolved XPS (PAR-XPS). For the experiments here discussed, spectra were collected at four detection angles, ranging between 30.5\({}^{\circ}\) (most bulk-sensitive angle) and 75.5\({}^{\circ}\) (most surface-sensitive angle), through constant steps of 15\({}^{\circ}\). Surface chemical composition was determined for each value of \(\theta\), with particular attention to the F\({}^{-}\) component (684.8 \(\pm\) 0.2 eV) in the F1s spectra's high resolution regions. In Figure 5, we report the trend of the signal as a function of \(\theta\) for each treatment. In the sample that underwent thermal treatments (Figure 5a), the abundance of inorganic fluoride (684.8 \(\pm\) 0.2 eV) decreased with the sampling depth, and the second component (688.8 \(\pm\) 0.2 eV), related to organic fluoride, grew with \(\phi\).