Fig. 4: Angle-resolved XPS core-level spectra of Janus SPtSe.
a Sketch illustrating the AR-XPS technique and the relationship between the probing depth d and the take-off angle θ (d = λ sin(θ), where λ is the attenuation length taking into account elastic scattering29). The probing depths are 11.5, 28.2, and 47.15 Å for 10°, 25°, and 45° take-off angles, respectively. b–d X-ray photoelectron spectra of Se 3p and S 2p core levels, taken at 45°, 25°, and 10° take-off angle θ on the sulfurized sample. The red line above the spectra corresponds to the fitting residual. The spectra have been normalized to the intensity at the S 2p core level. e S/Se concentration ratio as a function of the take-off angle θ.
