Hydrogen-assisted step-edge nucleation of MoSe₂ monolayers on sapphire substrates

Abstract

Controlled introduction of H2 during the CVD growth of MoSe2 plays a vital role in the step-edge aligned nucleation on a c-sapphire (0001) substrate.

Synthesis of Monolayer MoSe2 with Controlled Nucleation via Reverse-Flow Chemical Vapor Deposition

“…The nonlinear optical absorption of CVD-grown MoSe 2 and exfoliated samples is usually weakened by their random morphology, uncontrollable size and non-uniform thickness. Large-size monolayer MoSe 2 flakes ( Figure S4a) and uniform continuous film ( Figure S4b) can also be grown on the sapphire substrate with good light transmittance [10,22,23,32,33]. Open-aperture Z-scan measurements were performed using a homemade mode-locked Yb fiber laser operating at 1064 nm with a pulse width of 15 ps and a tunable repetition rate of 40 MHz [34].…”

Epitaxial Single‐Crystal Growth of Transition Metal Dichalcogenide Monolayers via the Atomic Sawtooth Au Surface

“…These results are in stark contrast with the appearance of triangular and inverted triangular TMdC grains on c ‐plane sapphire substrates reported by other studies. [ 24–26 ]…”

“…In addition, if the terrace facet is consistent over the entire region, the WS 2 grains are unidirectionally aligned, regardless of Miller indices. Coherent triangular WS 2 grains are consistently obtained, despite the possible generation of several other Miller indices in addition to the main (236) and (2,10,25) surfaces at fixed (111) and (100) terrace facets, respectively (Figure S13 and Table S2, Supporting Information). This is again attributed to the energetically favorable adsorption of W 3 S 6 clusters on a specific "B step edge" of an atomic sawtooth surface confirmed by DFT calculations.…”

“…These results are in stark contrast with the appearance of triangular and inverted triangular TMdC grains on c-plane sapphire substrates reported by other studies. [24][25][26] After a growth period of 20 min, a centimeter-scale SC WS 2 film is eventually obtained (Figure 1i). Low energy electron diffraction (LEED) pattern clearly indicates a supercell of WS 2 hexagonal lattice, Au (111) terrace facet, and atomic sawtooth Au (221) surface (Figure 1j and inset), congruent with the constructed LEED pattern (Figure S6, Supporting Information).…”

Selective saturation of step-edges as a tool to control the growth of molecular fibres

“…9 Moreover, they can act as active adsorption sites creating nucleation centres, which compete with the intrinsic epitaxial driven growth on the idealised, defect-free surface. Across different material classes, defects are sometimes also actively used to induce a specific growth behaviour, [10][11][12][13][14][15][16][17][18][19] while in general they cause a parasitic film growth, reducing long-range epitaxial ordering and yielding rather undefined interfaces. [20][21][22][23] However, even on idealised substrate surfaces, organic adlayers in particular exhibit pronounced dewetting, which leads to distinct island or fibre formation.…”