Fig. 1: GIXRD characterization of PtSe₂2 grown by selenization of Pt(111).

a A 80° sector map of the reciprocal space parallel to the surface at l = 0, as acquired after the selenization; (h, k, l) are surface reciprocal lattice units expressed in terms of the coincidence supercell; the orange hexagonal frames delimit Pt(111) Brillouin zones; orange and blue circles highlight two in-plane peaks belonging, respectively, to PtSe₂ and the Pt substrate lattices. The rings of scattered intensity centered around the origin can be indexed as polycrystalline grains Pt reflections, very likely originated from damaged areas of the single crystal surface. The inset on the right shows a highly resolved diffraction pattern corresponding to the black-dashed-line-delimited sector in the extended map; the image has been acquired from a different sample without Pt polycrystalline grains. b Highly resolved in-plane radial scans measured along the high symmetry direction h (highlighted in red in a) of the Pt(111) substrate before (blue) and after (orange) the selenization; the h axis is indexed using supercell reciprocal lattice units (s.r.l.u.); blue and orange filled circles indicates Pt(111) and PtSe₂ reflections, whereas the remaining peaks are associated to superstructure peaks by orange diamonds. c Plot and linear fit of the squared transversal width of the in-plane peaks measured by rocking scans as a function of the inverse squared modulus of the transfer vector q. The intercept of the fit with the vertical axis provides an estimation of the (negligible) overlayer mosaic spread. The slope of the linear fit allows deducing the average PtSe₂ ___domain size. d Scans along the out-of-plane direction l perpendicular to the sample surface at the positions (33l), (50l), and (70l), relative to a PtSe₂ Bragg peak and two superstructure peaks. The logarithm of the intensity is plotted.