Controllable growth of large-area 1T′, 2H ultrathin MoTe2 films, and 1T′–2H in-plane homojunction

Abstract

Atomically thin molybdenum ditelluride (MoTe2) has been intensively studied as an emerging material for electronics and optoelectronics due to its unique properties. While the small free energy difference between the 2H and 1T′ phases of MoTe2 always results in mixed-phase growth, precisely controlled phase transition of MoTe2 nanostructures is still a considerable challenge. Here, the centimeter-scale 1T′, 2H ultrathin MoTe2 films, and in-plane 1T′–2H homojunction have been synthesized by ambient pressure chemical vapor deposition based on the precursor design and space-confined strategies. The controllable growth of pure 1T′, 2H MoTe2, and 1T′–2H mixed-phase MoTe2 with phase separation and homogeneous mixture, respectively, has been achieved by adjusting growth temperature and growth time. The thickness of synthesized 1T′ and 2H ultrathin MoTe2 films can be effectively controlled by tuning the space-confined height. The corresponding growth mechanism was further illuminated based on systematically experimental characterizations and computational fluid dynamics simulations. The electrical transport properties of 1T′ and 2H MoTe2 films were investigated by conductive atomic force microscope and MoTe2-based thin-film field-effect transistors. Our experimental results provide a new route to realize the phase transition of two-dimensional materials, which makes these materials easily accessible as functional building blocks for next-generation electronic and optoelectronic devices.