Synthesis of Atomically Thin 1T-TaSe₂ with a Strongly Enhanced Charge-Density-Wave Order

Bulk 1T-TaSe₂ as a charge-density-wave (CDW) conductor is of special interest for CDW-based nanodevice applications because of its high CDW transition temperature. Reduced dimensionality of the strongly correlated material is expected to result in significantly different collective properties. However, the growth of atomically thin 1T-TaSe₂ crystals remains elusive, thus hampering studies of dimensionality effects on the CDW of the material. Herein, chemical vapor deposition (CVD) of atomically thin TaSe₂ crystals is reported with controlled 1T phase. Scanning transmission electron microscopy suggests the high crystallinity and the formation of CDW superlattice in the ultrathin 1T-TaSe₂ crystals. The commensurate–incommensurate CDW transition temperature of the grown 1T-TaSe₂ increases with decreasing film thickness and reaches a value of 570 K in a 3 nm thick layer, which is 97 K higher than that of previously reported bulk 1T-TaSe₂. This work enables the exploration of collective phenomena of 1T-TaSe₂ in the 2D limit, as well as offers the possibility of utilizing the high-temperature CDW films in ultrathin phase-change devices.