Fig. 3: Protonation of SFCO films.
a X-ray 2θ/θ diffraction patterns for as-grown (blue lines) and protonated SFCO films (orange lines). The films were protonated by applying a gate voltage VGS of 3.5 V for 30 min in transistor structures. The reflections indicated with the arrows originate from the protonated phase of SFCO films. b–d Co-substitution-changes in (b) the intensity of the (0 0 3/2)pc superlattice peaks for as-grown SFCO films, (c) the out-of-plane and in-plane lattice constants for as-grown SFCO films, and (d) hydrogen concentration for protonated SFCO films. The in-plane lattice constants were determined from the (114)pc reflection positions in reciprocal space mapping measurements (Supplementary Fig. S4). The lattice constants are plotted on the basis of the pseudo-cubic perovskite notation. The hydrogen concentrations of the SFCO films used for the XRD (Fig. 3a) and XAS characterizations (Fig. 4) were obtained from ERDA measurements and plotted with the blue and red symbols, respectively. Error bars in Fig. 3d correspond to the uncertainty in the hydrogen concentration calculated by fitting ERDA spectra. The gray lines in (b, d) are guides for the eye.
