Structural Evolution of Atomically Thin 1T’‐MoTe₂ Alloyed in Chalcogen Atmosphere

Abstract

Alloying is widely applied to tailor properties of 2D materials. Herein, a space‐confined chemical vapor deposition (CVD) strategy to homogeneously grow 100 μm‐sized monolayer 1T’‐MoTe2 in batches is developed. Aberration‐corrected annular dark‐field scanning transmission electron microscopy combined with density functional theory calculations is applied to investigate the atomic structural alteration of 1T’‐MoTe2 alloyed with sulfur. 1T’‐to‐2H phase transition is observed, triggered by both thermodynamic (stability improvement) and kinetic (phase transition barrier reduction) reasons. The alloying degrees of MoS2xTe2(1−x) grown at different temperatures display homophilic and random configurations, respectively, providing a feasible approach to tailor the atomic mixture of the alloying elements. The intralayer reconstruction and the interlayer displacement take place as defect concentration increases at elevated alloying temperatures. In contrast, 1T’‐MoTe2 displays high susceptibility in the presence of oxygen. An encapsulation method is developed using CVD‐grown monolayer MoS2, extending the lifetime of monolayer tellurides from several minutes to at least 24 h. These results gain fundamental insights into the structural change in both the beneficial (sulfurization) and detrimental (oxidation) alloying processes of atomically thin 1T’‐MoTe2 and provide a new degree of freedom for the controllable growth of 2D alloys (i.e., tailoring the alloying degree).

Phase-Controllable Chemical Vapor Deposition Synthesis of Atomically Thin MoTe2

“…For the 1T′-MoTe 2 grains, Figure 2 a shows the Raman-active modes of A g (86 cm −1 , 112 cm −1 , 127 cm −1 , 252 cm −1 , 269 cm −1 ) and B g (102 cm −1 , 162 cm −1 , 185 cm −1 ), which is consistent with previous reports on 1T′-MoTe 2 [ 45 ]. The Raman mapping of the most prominent B g (162 cm −1 ) peak of 1T′-MoTe 2 presents a uniform intensity distribution within the leaf-like shape (the inset of Figure 2 a), which displays a highly homogenous 1T′-MoTe 2 grain [ 47 , 51 , 52 , 53 , 54 ].…”

“…To make few-layer MoTe 2 domains more homogenous, a space-confined CVD system was applied as reported in our previous work [ 45 ], in which fluid dynamics are equivalent to the low-pressure CVD (LPCVD). Figure 1 a shows the schematic illustration of this space-confined CVD system possessing a narrow gap of 24 μm.…”

Two-dimensional materials: synthesis and applications in the electro-reduction of carbon dioxide

“…Moreover, Here, carbon atoms are represented by blue spheres, boron is shown in yellow, and nitrogen is in purple [71] . (E-G) Synthesis of 2D Fe single-crystal nanoflakes by space-confined CVD [77] . 2D: 2-dimensional; CVD: chemical vapor deposition; TEM: transmission electron microscopy.…”

“…Space-confined CVD can be used to achieve the growth of high-quality 2D materials. Recently, Li et al used Te-assisted CVD to precisely synthesize 2D Fe single-crystal nanoflakes with different thicknesses [77] [Figure 3E-G]. Xu et al used space-confined CVD to grow homogeneous 1T'-MoTe 2 monolayers with a lateral size of 100 μm in batches, demonstrating that the confined space can increase the vapor pressure of sulfur to extend the lifetime of monolayer tellurides from several minutes to at least 24 h [78] .…”

Ambipolar‐To‐Unipolar Conversion in Ultrathin 2D Semiconductors

“…[42] Another doping process can be generated using defect engineering by creating single anion or cation vacancies: anion vacancies operate as donor sites, whilst cation vacancies act as acceptor sites, resulting in n-doping and p-doping, respectively. [45] As an example, Li Gao et al presented a strategy for precise vacancy control using chemical treatment. Some S-vacancies are created in MoS 2 by breaking S-Mo bonds by the introduction of electrons by HO 2 -from the H 2 O 2 solution (Figure 5f ).…”