Phase-Controllable Chemical Vapor Deposition Synthesis of Atomically Thin MoTe2

Abstract

Two-dimensional (2D) molybdenum telluride (MoTe2) is attracting increasing attention for its potential applications in electronic, optoelectronic, photonic and catalytic fields, owing to the unique band structures of both stable 2H phase and 1T′ phase. However, the direct growth of high-quality atomically thin MoTe2 with the controllable proportion of 2H and 1T′ phase seems hard due to easy phase transformation since the potential barrier between the two phases is extremely small. Herein, we report a strategy of the phase-controllable chemical vapor deposition (CVD) synthesis for few-layer (<3 layer) MoTe2. Besides, a new understanding of the phase-controllable growth mechanism is presented based on a combination of experimental results and DFT calculations. The lattice distortion caused by Te vacancies or structural strain might make 1T′-MoTe2 more stable. The conditions for 2H to 1T′ phase conversion are determined to be the following: Te monovacancies exceeding 4% or Te divacancies exceeding 8%, or lattice strain beyond 6%. In contrast, sufficient Te supply and appropriate tellurization velocity are essential to obtaining the prevailing 2H-MoTe2. Our work provides a novel perspective on the preparation of 2D transition metal chalcogenides (TMDs) with the controllable proportion of 2H and 1T′ phase and paves the way to their subsequent potential application of these hybrid phases.

Recent Strategies for the Synthesis of Phase-Pure Ultrathin 1T/1T′ Transition Metal Dichalcogenide Nanosheets

“…Because of the low energy barrier between 1T′ and 1H, MoTe 2 and WTe 2 could be easily grown using CVD by controlling the tellurization velocity, ,, as shown in Figure (a) . During rapid tellurization, the built-in strain or Te-rich vacancies in the deposited film stabilize 1T′ phase tellurides . Additionally, precursors influence TMD polytypes.…”

“…The energy of the intermediate species decreases with increasing the NaCl content in the precursor, which facilitates growth of MoS 2 nanosheets. (a) reproduced with permission from ref . Copyright 2022 MDPI.…”

“…253 During rapid tellurization, the built-in strain or Te-rich vacancies in the deposited film stabilize 1T′ phase tellurides. 253 Additionally, precursors influence TMD polytypes. Using spin-coating, liquid precursor droplets containing sodium molybdate and sodium hydroxide were spread on sapphire substrates and functioned as nucleation sites during CVD heating.…”