Fig. 2: Polytype isolation forms 2D CDW layers.
From: Two-dimensional charge order stabilized in clean polytype heterostructures
a Pristine 1T-TaS2 at room temperature hosts NC-CDW (left). Upon heating the NC phase gives way to IC-CDW (right) at ~350 K; the transition is normally reversible. Remarkably, heating above ~620 K then cooling stabilizes tC-CDW (bottom). SAED patterns were formed from a 500 nm aperture b–e In-situ TEM reveals layer-by-layer octahedral to prismatic polytypic transformations during heat treatment. Multiple polytypic domains (denoted green, purple, and yellow) nucleate and grow simultaneously without interaction (See Supplementary Movie 1). Scale bar is 350 nm. f Schematic cross-section of TaS2 during layer-by-layer polytypic transition. g Fast and slow transitions occur along \(\langle 10\overline{1}0\rangle\) and \(\langle 11\overline{2}0\rangle\) directions respectively. h, i Atomic resolution cross-sectional HAADF-STEM of h pristine and i heat-treated TaSxSe2−x confirms polytypic transformation. After treatment, prismatic (Pr) layers encapsulate monolayers of octahedral (Oc) layers. Scale bar is 2 nm. A selenium doped sample was imaged to enhance chalcogen visibility.
