Fig. 1: Selective epitaxial growth of Cr_xTe_y.

a Side view of the crystal structure of ML-CrTe₂ and ML-Cr₂Te₃ on an HOPG substrate. b Schematic of the formation of the Cr_1+δTe₂ phases with Cr atoms self-intercalating within the van der Waals gap of CrTe₂. c, d RHEED patterns of samples grown at a substrate temperature of (c) T_s = 400 °C and (d) T_s = 700 °C [Cr cell temperature: 1025 °C], and (e) corresponding intensity profiles extracted from the shaded regions in (c, d). The extracted in-plane lattice constants (stars in (i)) are consistent with CrTe₂ and [Cr₂Te₃, Cr₃Te₄], respectively. f, g AFM images for the samples shown in (c, d). h AFM line profiles corresponding to the lines shown in (f, g), revealing the different thickness of the monolayer islands, again consistent with CrTe₂ and [Cr₂Te₃, Cr₃Te₄], respectively. i Obtained growth phase diagram of Cr_xTe_y as a function of substrate and Cr effusion cell temperature, as determined from lattice constant measurements from RHEED. Stars indicate the in-plane lattice constants as measured from samples for which the corresponding RHEED and AFM images are shown in (c, d, f, g).