## 3 Results and Discussion
### Electrical Properties
[50] who showed that the sheet resistance and resistivity of amorphous V\({}_{2}\)O\({}_{5}\) increase with the increases in the amount of oxygen in the sputtering gas ratio. Researchers showed that proper control of the oxygen flow rate enables adjustments to some properties of vanadium pentoxide, e.g., electrical properties or stoichiometry [50]. Figure 8: Resistivity as a function of 1000/T of vanadium oxide thin films deposited with various Ar:O\({}_{2}\) gas ratios during sputtering process. In addition, to compare the optical and electrical properties of analysed vanadium oxide thin films deposited with different Ar:O\({}_{2}\) ratios during sputtering, the merit figure (Q) was calculated based on the average transmission in the visible wavelength range and resistivity values (Equation (1)), for each sample. The calculated values of the merit figure are in the range from 2.64\(\cdot\)10\({}^{-8}\) to 3.31\(\cdot\)10\({}^{-6}\) and the dependence of Q on the Ar:O\({}_{2}\) gas ratios during sputtering is shown in Figure 10. The thin films deposited with Ar:O\({}_{2}\) gas ratios of 3:1 and 4:1 were found to have the highest Q values. This was related to the high average transmission, which was very similar to the V\({}_{\mathrm{x}}\)O\({}_{\mathrm{y}}\) deposited with Ar:O\({}_{2}\) gas ratio 2:1, and at the same time resulted in a one-order lower value of resistivity compared to the mentioned sample. Thin films deposited with a gas ratio greater than 4:1 had significantly lower average transmission, which led to a decrease in the Q factor. The Seebeck coefficient (S\({}_{\mathrm{c}}\)) of the prepared thin films was determined on the basis of thermoelectric measurements (Figure 11). The characteristics of the thermoelectric voltage as a function of the temperature difference between electrical contacts for all the deposited vanadium oxide thin films are presented in Figure 9. The positive sign of the Seebeck coefficient indicates the hole type of electrical conduction, while the negative sign indicates the electron type [51]. Samples prepared with the lowest oxygen content in Ar:O\({}_{2}\) gas ratios, i.e., 8:1, 7:1 and 6:1, were p-type semiconductors, whereas those prepared with ratios below 6:1 were n-type semiconductors. Therefore, a lower O\({}_{2}\) content in the Ar:O\({}_{2}\) gas mixture resulted in a p-type of electrical conduction that could be an effect of the oxygen vacancies present in the microstructure of the film. The oxygen vacancies were also responsible for the deterioration of the average transmission in the visible-wavelength range of deposited thin films and an increase in their conductivity. Similar behaviour of optical and electrical properties has been already reported for non-stoichiometric WO\({}_{\mathrm{x}}\) thin films prepared by magnetron sputtering [30]. As the sputtering atmosphere became more oxygen rich, the conduction switched to the electron type, which was related to a lower number or even an absence of oxygen vacancies. The thermoelectric characteristics with calculated S\({}_{\mathrm{c}}\) are presented in Figure 8.0  
Figure 8.1 Dependence of sheet resistance and resistivity of vanadium oxide thin films on the Ar:O\({}_{2}\) gas ratio during the preparation process. The summary of optical and electrical properties of as-deposited vanadium oxide thin films is shown in Figure 8.2  
Figure 8.3 Thermoelectric characteristics of vanadium oxides thin films deposited with various ArO\({}_{2}\) gas ratios. Figure 8.4 Dependence of the figure of merit of vanadium oxide thin films on the Ar:O\({}_{2}\) gas ratio during the magnetron sputtering process.