Fig. 4: SEM morphology and elemental distribution of FEVE and F-T/S films.

a SEM image (2000 ×) of the FEVE film, (b–f) distribution of C, O and F elements, and XRF analysis diagram; (g) SEM image (2000 ×), of the F-T/S-1 film; (h–o) distribution of C, O, F, Si, and Ti elements, and XRF analysis diagram, elements are uniformly distributed on the surface of the F-T/S films.