## 3 Results and Discussion
The surface adsorbates are bound by AlO\({}_{\mathrm{x}}\), and since the surface sensitivity of Al is much lower than that of Zn (Al 2p signal comes from the topmost \(\sim\)7.5 nm, while the Zn 2p signal comes from the topmost \(\sim\)3 nm), one can assume that the surface is dominated by AlO\({}_{\mathrm{x}}\). A second argument for this assumption is that the AlO\({}_{\mathrm{x}}\) lattice signal increases after irradiation, as well as the Al-O component in the O 1s spectrum, while the Zn contribution associated with the lattice component decreases. Figure 3:4 Refractive index and extinction coefficient of the thickest layer in model of **(a)** AZO samples and **(b)** ITO samples. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Relative Contribution** & **Zn [\%]** & **Al [\%]** & **O [\%]** \\ \hline \multirow{4}{*}{AZO: H+} & Lattice & 76.4 & 50.3 &
\begin{tabular}{c} 41.3 Zn-O \\ 23.7 Al-O \\ \end{tabular} \\  & Surface & 21.3 & 30.4 & \\  & Defects & 2.3 & 19.2 & 26.8 \\  & Adsorbates & & & 8.3 \\ \hline \multirow{4}{*}{AZO: H+} & Lattice & 64.8 & 56.5 & 27.2 Zn-O \\  & Surface & & & 39.0 Al-O \\  & Defects & & 27.8 & 20.2 \\  & Adsorbates & 1.7 & & 13.7 \\ \hline \multirow{4}{*}{ITO} & & In [\%] & Sn [\%] & O [\%] \\  & Lattice & 64.1 & 67.2 & 45.1 \\ \cline{1-1}  & Surface & 30.0 & 32.8 & 25.9 \\ \cline{1-1}  & Defects & & & 29.0 \\ \cline{1-1}  & Adsorbates & 5.9 & & \\ \hline \multirow{4}{*}{ITO: H+} & Lattice & 64.4 & 68.1 & 41.7 \\ \cline{1-1}  & Surface & 29.6 & 31.9 & 27.0 \\ \cline{1-1}  & Defects & & & 31.3 \\ \cline{1-1}  & Adsorbates & 6.1 & & \\ \hline \end{tabular}
\end{table} 
Table 1: Relative contribution of components in the XPS analysis of AZO and ITO before and after proton irradiation. Figure 7: XPS results for AZO and AZO:H+ samples (**a**) of Zn 2p, (**b**) Al 2p, and (**c**) of O 1s; for ITO and ITO:H+ of (**d**) In 3d, (**e**) Sn 3d 5/2, and (**f**) O 1s. The black line represents the fit line, empty blue circles are data of non-irradiated samples, and red circles are data of irradiated samples. The shift of the signal to higher binding energies is related to the decrease in the conductivity of the surface, as then more energy is needed to extract a core-level electron. The main component of Al 2p shifted from 73.6 eV BE to 73.8 eV after irradiation. The main component of Zn 2p shifted from 1021.3 eV BE to 1021.5 eV. In the case of O 1s, the Zn-O component shifted from 529.8 to 530 eV and the Al-O from 531.8 to 532 eV. All the secondary components of Al 2p, Zn 2p, and O 1s also shifted to higher energies. This indicates that the resistance of AZO should increase after proton irradiation. This behaviour is also consistent with the surface dominated by AlO\({}_{\rm x}\), which is a high band gap insulator [27]. In the case of ITO, the irradiation does not change the surface, as there is no notable shift in the BE of the core levels and also no change in the composition of the surface. Only the intensity component of O 1s that comes from the I\({}_{2}\)O\({}_{3}\) lattice is slightly decreased (Figure 7f). In the case of ITO, information about relative concentrations of Sn and In can be extracted from XPS because the kinetic energies of the species of interest are comparable, and thus the surface sensitivities are comparable. Both samples show an In:Sn ratio of 10:1. The sheet resistance of the films changed only slightly for ITO film (increase of about 1.8%). AZO before irradiation had a resistance of 302.485 \(\pm\) 3.413 \(\Omega/\square\), which, after the experiment, decreased to 202.347 \(\pm\) 0.265 \(\Omega/\square\) (33% decrease). The results of the four-point probe measurements are summarized in Table 2. The decrease in resistance of AZO after irradiation is in contrast to the XPS results, which indicate increased electrical resistance. As AZO is an oxide semiconductor, its conductivity is influenced by the presence of oxygen vacancies and metallic interstitial defects.