Improved luminescence properties of MoS₂ monolayers grown via MOCVD: role of pre-treatment and growth parameters

Abstract

Fabrication of transition metal dichalcogenides (TMDCs) via metalorganic chemical vapor deposition (MOCVD) represents one of the most attractive routes to large-scale 2D material layers. Although good homogeneity and electrical conductance have been reported recently, the relation between growth parameters and photoluminescence (PL) intensity-one of the most important parameters for optoelectronic applications-has not yet been discussed for MOCVD TMDCs. In this work, MoS is grown via MOCVD on sapphire (0001) substrates using molybdenum hexacarbonyl (Mo(CO), MCO) and di-tert-butyl sulphide as precursor materials. A prebake step under H atmosphere combined with a reduced MCO precursor flow increases the crystal grain size by one order of magnitude and strongly enhances PL intensity with a clear correlation to the grain size. A decrease of the linewidth of both Raman resonances and PL spectra down to full width at half maxima of 3.2 cm for the E Raman mode and 60 meV for the overall PL spectrum indicate a reduced defect density at optimized growth conditions.

Tailoring Domain Morphology in Monolayer NbSe2 and WxNb1–xSe2 Heterostructure

“…High-quality TMDs and their lateral heterostructures including metallic NbS 2 /semiconducting WS 2 have been successfully synthesized on a large scale by chemical vapor deposition (CVD). − There are three CVD approaches for growing TMDs, namely, (i) solid-metal-precursor, , (ii) vapor-metal-precursor, − and (iii) liquid-metal-precursor approaches. ,, Solid-metal-precursor CVD provides high-quality TMDs with crystal domains of a few tens of μm in size; however, sample uniformity is often limited by the growth conditions. − The vapor-metal-precursor approach, with metal–organic CVD as an example, provides a uniformly distributed sample on a 4 in. wafer, but the grown TMD suffers from low crystallinity (a few hundred nm domain) and low accessibility due to its toxicity .…”

Gaussian synapses for probabilistic neural networks

“…Therefore, hardware implementation of PNNs using Gaussian synapses will necessitate large-area growth of MoS 2 and BP. Fortunately, recent years have seen tremendous progress in wafer-scale growth of high quality MoS 2 and BP using chemical vapor deposition (CVD) and metal organic chemical vapor deposition (MOCVD) techniques 37–41 . Furthermore, while we have used two different 2D materials, MoS 2 and BP, for our demonstration of Gaussian synapses owing to their superior performance as n-type and p-type FETs, respectively, there are 2D materials, such as, WSe 2 , which offer ambipolar transport, i.e., the presence of both electron and hole conduction 42 and can be grown over large area using CVD techniques 43 .…”

2D MoS2 Heterostructures on Epitaxial and Self‐Standing Graphene for Energy Storage: From Growth Mechanism to Application

“…[ 1–3 ] Some 2D materials show also exceptional topological features, allowing pairs of electrons to travel without resistance along specific paths. [ 4,5 ] These characteristics can be exploited not only in nanoelectronics, but also in a large number of other applications, like sensing, [ 6–8 ] optoelectronics [ 6,9,10 ] and energy storage. [ 11–16 ]…”

“…[27] CVD starting from MoO 3 and S precursors can be used to grow high-quality MoS 2 heterostructures on several substrates in a scalable way. [9,[28][29][30][31][32][33] Controlling the size, shape, and number of layers of MoS 2 is possible by changing the growth parameters of the CVD reactor; [34] however, the growth depends critically on the interaction with the substrate and a full understanding of this process is still lacking.…”

“…[1][2][3] Some 2D materials show also exceptional topological features, allowing pairs of electrons to travel without resistance along specific paths. [4,5] These characteristics can be exploited not only in nanoelectronics, but also in a large number of other applications, like sensing, [6][7][8] optoelectronics [6,9,10] and energy storage. [11][12][13][14][15][16] One way of combining the favorable characteristics of semiconducting 2D materials with the exceptional conductivity of graphene, is by stacking them to create van der Waals heterostructures.…”