Effect of Carrier Gas Flow Field on Chemical Vapor Deposition of 2D MoS2 Crystal

Abstract

The carrier gas flow field plays a vital role in the chemical vapor deposition (CVD) process of two dimensional (2D) MoS2 crystal, which was studied by simulations and experiments. Different carrier gas flow fields were studied by utilizing three types of precursor carrier which affected the local gas flow field significantly. The experiment results showed that the appropriate precursor vapor concentration could be achieved by local carrier gas flow field conditioning, resulting in single 2D MoS2 crystals of a large size and a high coating rate of 2D MoS2 crystal on the target substrate surface. The carrier gas flow also contributed to the growth of the 2D MoS2 crystal when it flew towards the target surface. The size of deposited single 2D MoS2 crystal reached tens of micrometers and a few layers of 2D MoS2 crystal were characterized and confirmed.

Role of gas flow direction on monolayer MoS2 growth on patterned surfaces via CVD

“…Various intrinsic lattice defects including vacancies, substitutional impurities, adatoms, antisite defects, and grain boundaries are frequently observed in TMDs, mostly resulted from a variety of non-optimized growth conditions. Laminarity of the precursor vapor flow is of vital importance for the growth of high-quality 2D crystals as it is controlling the crystallinity by directly affecting the structural defect density [22,29,37]. We did not observe any variation in the Raman spectra considering the change in flow direction.…”

“…Bai et al investigated how MoS 2 grain size is affected by the gas flow concentration around the substrate surface using differently shaped quartz crucibles. They showed that reduced velocity or pressure led to an increased MoS 2 grain size, which could result from longer residence times on the surface [29]. The flow perpendicular to the microchannels may give rise to the augmentation of the number of vortices enhancing the intensity of the turbulence around the channels resulting in non-uniform dispersion [21].…”

Molten glass-mediated conditional CVD growth of MoS2 monolayers and effect of surface treatment on their optical properties

“…Previous studies have shown that sodium ions enhance the growth rate by reducing the energy barrier for MoS 2 growth and promote film formation by forming an intermediate product with a lower melting point than MoO 3 [34][35][36]. The CVD process can be outlined in five key steps: (a) sublimation of precursors and transport by a carrier gas; (b) diffusion towards the substrate; (c) surface adsorption; (d) spreading of adatoms across the surface; and (e) the occurrence of the reaction to form flakes/film [37]. The efficiency of precursor transport is directly dependent on the carrier gas.…”

Low-cost Millimeter Scale Single-Layer MoS2 Synthesis via Chemical Vapor Deposition

“…Therefore, a large number of MoS 2 molecules accumulate on the substrate to deposit a continuous MoS 2 monolayer structure. In other words, higher concentrations of molybdenum and sulfur vapor allow for larger-sized MoS 2 crystal fragments or more of the target area to be covered with MoS 2 [43]. For open-ended quartz boat, the different distributions of MoS 2 structures on SiO 2 /Si substrate are also investigated (see Fig.…”