## 3 Results and Discussion
This may be an indication of the combined effect of the surface roughness of the films and the nature of chemical bonds due to the greater difference in the electronegativity between _In_ (1.78) and _Mg_ (1.31). Therefore, the highest hydrophobicity among all investigated materials was observed in In\({}_{0.4}\)Mg\({}_{0.8}\)O\({}_{1.4}\) films. The electronegativity of atoms determines the polarity of a bond, since the electronegativity is a measure of the tendency of an atom to attract electrons (or electron density) towards itself, and it determines how the shared electrons are distributed between the two atoms in a bond. The difference in electronegativity between two atoms determines how polar a bond will be. Therefore, the chemical nature of a surface determines its polarity. On the other hand, the water is classified as a polar molecule because of its polar covalent bonds and its bent shape. As a result of water's polarity, it attracts, or is attracted to, other polar molecules and ions. This interaction determines the hydrophilicity or hydrophobicity of a surface. For instance, an atomistic computer simulation was used to explore the relationship between the mesoscopic (liquid drop contact angle) and microscopic (surface atomic polarity) characteristic of water in contact with a model solid surface, such as a structure of silica [69]. It was found that the hydrophobicity varies substantially when the topography and polarity of the surface act in concert with the asymmetric charge distribution of water. It was also shown that, in order to prepare the materials with a larger contact angle, one should combine the effect of the surface roughness and chemical composition, since both of them determine the wettability of the surface [70; 71; 72]. Concerning the specific behavior of ITO films compared to other material systems, one can suppose that it could be related to the presence of \(Sn\) in their composition, which is absent in other investigated materials. Note that the electronegativity of \(Sn\) (1.96) is the largest among the metals used in this paper. As a result, the increase in the \(Ga\) content in ITO films leads to the increase in their surface roughness, while the concomitant decrease in the Sn content leads to the decrease in their hydrophobicity, i.e., they become more hydrophilic. These assumptions are corroborated by the analysis of the behavior of Ga\({}_{2}\)O\({}_{3}\) films incorporated by \(Al\) or \(St\). As one can see from Figure 5, the incorporation of \(Al\) in undoped Ga\({}_{2}\)O\({}_{3}\) films forming a Ga\({}_{1.75}\)Al\({}_{0.25}\)O\({}_{3}\) composite leads to an increase in the surface roughness by a factor of 2 and an increase in the contact angle from 117.8\({}^{\circ}\) to 122.3\({}^{\circ}\). This behavior is similar to that of (In\({}_{1-x}\)Ga\({}_{x}\))\({}_{2}\)O\({}_{3}\) films, i.e., an increase in surface roughness leads to an increase in the hydrophobicity of films in both cases. On the other hand, the incorporation of \(Sn\) in undoped Ga\({}_{2}\)O\({}_{3}\) forming a (Ga\({}_{2}\)O\({}_{3}\))\({}_{0.75}\)(SnO\({}_{2}\))\({}_{0.25}\) composite film with lower surface roughness also leads to an increase in the hydrophobicity, this behavior being similar to that of ITO films. Apart from the investigation of the morphology and wettability properties of the prepared films, their optical properties have been investigated with the purpose of their bandgap assessment. The optical absorption spectra of some of the prepared films are shown in the Figure 6 plot in the Tauc coordinates, i.e., the dependence of the absorption coefficient (\(\alpha\)hv)\({}^{2}\) vs the hv photon energy. The thickness of the produced films, measured from cross-sectional SEM images, as well as from interference fringes in the optical reflection spectra, was found to be several hundred of nanometers. The exponent of the power function in the Tauc formula should be 2 for direct transitions and \(\%\) for indirect transitions.