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.