Gold-vapor-assisted chemical vapor deposition of aligned monolayer WSe2 with large domain size and fast growth rate

Abstract

Orientation-controlled growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs) may enable many new electronic and optical applications. However, previous studies reporting aligned growth of WSe 2 usually yielded very small domain sizes. Herein, we introduced gold vapor into the chemical vapor deposition (CVD) process as a catalyst to assist the growth of WSe 2 and successfully achieved highly aligned monolayer WSe 2 triangular flakes grown on c-plane sapphire with large domain sizes (130 μm) and fast growth rate (4.3 μm•s −1 ). When the aligned WSe 2 domains merged together, a continuous monolayer WSe 2 was formed with good uniformity. After transferring to Si/SiO 2 substrates, field effect transistors were fabricated on the continuous monolayer WSe 2 , and an average mobility of 12 cm 2 •V −1 •s −1 was achieved, demonstrating the good quality of the material. This report paves the way to study the effect of catalytic metal vapor in the CVD process of TMDCs and contributes a novel approach to realize the growth of aligned TMDC flakes.

Large‐Size Ultrathin α‐Ga2S3 Nanosheets toward High‐Performance Photodetection

“…Chemical vapor deposition (CVD) method is an alternative way to grow continuous 2D layered semiconductors on large scales. [ 33–35 ] For obtaining ultrathin nanosheet, metal and metal oxide precursors are common in conventional CVD method. However, these regular precursors (Ga, Ga 2 O 3 ) are unsuitable for synthesis of specific 2D materials with large size, due to high melting points and low vapor pressures of precursors are unstable growth conditions in the reaction.…”

Epitaxy of 2D Materials toward Single Crystals

“…Besides, high chalcogen evaporation temperatures and early feeding of chalcogen vapors are also conducive to achieve the alignment of TMDC domains. [ 116 , 117 ] It also should be noted that considering the smaller nucleus has lower barrier to rotate, the growth rate of nucleus should be as slow as possible that it has enough time to rotate to the preferred orientation. [ 116 , 117 ] To sum up, from the perspective of precursor reaction, sufficient reduction of metal precursors and appropriate reaction rate are favorable for vdW epitaxy.…”

“…[ 116 , 117 ] It also should be noted that considering the smaller nucleus has lower barrier to rotate, the growth rate of nucleus should be as slow as possible that it has enough time to rotate to the preferred orientation. [ 116 , 117 ] To sum up, from the perspective of precursor reaction, sufficient reduction of metal precursors and appropriate reaction rate are favorable for vdW epitaxy. Meantime theoretical calculation results revealed that TMDC domain alignment on sapphire with Al‐terminated surface is more feasible due to higher absorption energy.…”

“…[ 116 ] Similarly, high Se/W ratio contributed to the alignment growth of WSe 2 on c ‐plane sapphire. [ 117 ] In the CVD growth of TMDC, metal precursors are always in the solid state. If the metal‐containing particles are not fully reduced during the growth, they would serve as the nucleation sites and the nuclei lose their rotational freedom, resulting in failure of vdW epitaxy.…”

Ternary hybrid CuO-PMA-Ag sub-1 nm nanosheet heterostructures

“…1 The wet-chemical methods usually include heat-up or hot-injection in three-neck flasks [12][13][14] and hydrothermal (solvothermal) methods, 15,16 most of which need to conduct complex two-step growths and it is difficult to control the shape and size of products. Although the gaseous strategies (physical / chemical vapor deposition) [17][18][19][20][21] can realize the powerful control on the shape, size and composition of nanoheterostructures through the related parameters regulation, it is quite difficult to control the size of nanoheterostructures in sub-1 nm scale. Atomic layer deposition (ALD) as an advanced atom-level vapor-phase deposition technique can create atomic-level epitaxial growth, but it is usually faced with expensive apparatus and time-consuming operations.…”