# New Insights in the Ion Beam Sputtering Deposition of ZnO-Fluoropolymer Nanocomposites
## 3 Results and Discussion  
### Thin Film Deposition and Morphological Characterization  
Optimized IBS deposition parameters for composite ZnO-CF\({}_{x}\) thin films, at different inorganic volume fractions, have already been reported elsewhere [45]. We previously demonstrated that, with this technique, an organic-inorganic thin film with an easily tunable thickness and \(\phi\) could be prepared. In this study, ZnO-CF\({}_{x}\) composites were characterized by a good morphological in-plane homogeneity, as shown in the TEM micrographs reported in Figure 1.  
For the lowest inorganic volume fraction, i.e., \(\phi\) = 0.05, ZnO clusters with an average cluster size of 5-8 nm were appreciable (Figure 1a). Anyhow, the ZnONP morphology showed dependence upon \(\phi\). In fact, both the cluster size and its surface density increased with the ZnO loading. In particular, for \(\phi\) = 0.10 (Figure 1b) and \(\phi\) = 0.15 (Figure 1c), cluster coalescence occurred with evident percolation pathways. The TEM pictures of the ZnO-CF\({}_{x}\) ultrathin films should be only considered as elucidative images, being most of the study focused on much thicker coatings, which are more representative of the material when it is used in real-life applications.  
When depositing thicker films (150 nm), the ZnO-CF\({}_{x}\) composites showed the presence of large spheroidal islands/clusters (with diameters higher than 100 nm and height of tens of nm) laying down on a low-roughness background. The surface roughness (RMS) ranged from 1.31 \(\pm\) 0.05 nm (for \(\phi\) = 0.05) to 2.03 \(\pm\) 0.09 nm (for \(\phi\) = 0.15) as outlined in Figure 2.  
Figure 1: Transmission electron microscopy (TEM) micrographs of ZnO-CF\({}_{x}\) nanocomposites having an inorganic phase volume fraction of \(\phi\) = 0.05 (**a**); \(\phi\) = 0.10 (**b**); and \(\phi\) = 0.15 (**c**).  
Cluster abundance was a function of \(\phi\), while their average in-plane size appeared to be not affected by the ZnO loading. These large spheroidal features were not visible in thinner films subjected to TEM characterization. Hence, their presence could be attributed to the deposition of a thicker layer. In order to understand their physicochemical nature, the same samples underwent scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy (for experimental details please refer to the electronic Supplementary Material). The surface morphology observed by SEM was analogous to the one revealed by AFM. For explicative purposes, SEM micrographs of ZnO-CF\({}_{x}\) thin films were also observed in the TEM characterization.  
Figure 2: Atomic force microscopy (AFM) micrographs of ZnO-CF\({}_{x}\) nanocomposites having an inorganic phase volume fraction of \(\phi\) = 0.05 (**a**–**a**), \(\phi\) = 0.10 (**b**–**b**), and \(\phi\) = 0.15 (**c**–**c**).  
films are reported in Figure S1. An elemental analysis was performed both on clusters and substrate, and the results obtained are reported in Table 1 as a function of \(\phi\).  
The F/Zn ratio diminishes with \(\phi\), as expected. Anyhow, it is worth noting that this ratio is lower in the case of clusters with respect to the amorphous polymeric background on which the sub-micron structures lay. This was considered indicative of the chemical nature of the spheroidal features, which were mostly composed by inorganic material and covered by a polymer layer.