Figure 8 The decomposed O 1s XPS lines of the IHfO:H thin films without annealing (a) and annealed at (b) 150 °C, (c) 200 °C, and (d) 250 °C.
The decomposed O 1s XPS lines of the IHfO:H films annealed at different temperatures are shown in Figure 8. The relative intensities of the three XPS peaks of OA, OB, and OC are listed in Table 2. It can be seen that as the annealing temperature increases to 250 °C, the relative integral area of the OB peak, representing the oxygen vacancies, gradually decreases from the as-deposited of 13.34 % to 9.74 % due to the filling of the oxygen vacancies by oxygen in the air during the annealing process, as studied by Meng et al.24 With the same initial Hf and hydrogen doping concentrations, the decrease of the oxygen vacancies is one of the reasons for the decrease of the carrier concentration of the IHfO:H films. In addition, hydrogen might escape during the annealing process as mentioned above, which is another possible reason for the carrier concentration reducing at high annealing temperature. Thereby, the excessively rapid decrease in carrier concentration leads to an increase in the sheet resistance of the IHfO:H films.