“…Based on classical semiconductor theory, Mott-Schottky Eq. ( 15) can be used to describe the linear relationship between 1/C 2 and electrode potential [39,40]. Figure 7a shows the Mott-Schottky curves of the three L-PBF NiTi immersed in artificial saliva for 168 h. When the electrode potential is higher than the flat band potential, the curves are all positive, indicating that the passive films of the L-PBF NiTi formed in artificial saliva at OCP are n-type semiconductor, which again confirms that the passive film on the NiTi-SMA surface is mainly composed of TiO 2 [29].…”