Fig. 1: Fe:talc structural analysis.

a Optical micrograph of several Fe:talc flakes on SiO₂/Si substrate (300 nm SiO₂ layer) also indicates the estimated number of layers for the thicker flakes. Inset of (a) presents AFM topography image of a monolayer Fe:talc (5 × 5 µm², z = 6 nm) indicated in a by the dotted black square. b Height cross section (blue line) along the dashed white line in the inset of a and the fitted height profile (red line), also showing a side view of the Fe:talc structure. c Crystal structure of a monolayer of Fe:talc (top view) obtained from ab initio calculations. d Raman spectrum of the characteristic Mg-OH and Fe-OH vibrations (black line) for Fe:talc, in comparison to minnesotaite (red line; reprinted from Wang et al.⁴⁰). Inset of d presents an optical micrograph of the Fe:talc flake from which the spectrum is reported. e WDS spectrum of the Fe Kα line, compared to a reference spectrum of an iron-poor talc flake with similar thickness. Inset of e presents a WDS map (scale bar 5 µm) of the Fe Kα line. f SAED pattern of a ~20 layer suspended flake (200 kV, ~250 nm beam diameter). The diffraction pattern was recorded after the suspended flake was stored for more than 24 months under ambient conditions. Labeled diffraction peaks were identified by modeling of the SAED pattern of talc. The inset of f shows a 10 × 10 nm² atomic-resolution TEM image of the same sample.