Figure 3: XPS characterization of franckeite surface.
From: Exfoliation of natural van der Waals heterostructures to a single unit cell thickness
(a) Average XPS spectrum of franckeite obtained from multiple individual measurements, referenced to the adventitious carbon C 1s peak at 284.7 eV (ref. 46). The peaks labelled in red were used for the quantification shown in Table 2. Other significant peaks, which were not used in quantification, are labelled in black. (b–e) High-resolution spectra of Pb 4f, Sn 3d, Sb 3d (+ O 1s), and S 2p binding energy regions. The intensities are normalized to the most intense peak within the respective spectral region.
