Epitaxial Growth of Rectangle Shape MoS₂ with Highly Aligned Orientation on Twofold Symmetry a‐Plane Sapphire

Abstract

2D transition-metal dichalcogenides (TMDs) are an emerging class of materials with superior properties that make them highly attractive for fundamental studies of novel physics and for applications ranging from nanoelectronics and nanophotonics to sensing and catalysis. [1][2][3][4][5] As the most extensively Research on transition metal dichalcogenides (TMDs) has been accelerated by the development of large-scale synthesis based on chemical vapor deposition (CVD) growth. However, in most cases, CVD-grown TMDs are composed of randomly oriented grains, and thus contain many distorted grain boundaries (GBs), which seriously degrade their electrical and photoelectrical properties. Here, the epitaxial growth of highly aligned MoS 2 grains is reported on a twofold symmetry a-plane sapphire substrate. The obtained MoS 2 grains have an unusual rectangle shape with perfect orientation alignment along the [1-100] crystallographic direction of a-plane sapphire. It is found that the growth temperature plays a key role in its orientation alignment and morphology evolution, and high temperature is beneficial to the initial MoS 2 seeds rotate to the favorable orientation configurations. In addition, the photoluminescence quenching of the well-aligned MoS 2 grains indicates a strong MoS 2 −substrate interaction which induces the anisotropic growth of MoS 2 , and thus brings the formation of rectangle shape grains. Moreover, the well-aligned MoS 2 grains splice together without GB formation, and thus that has negligible effect on its electrical transport properties. The progress achieved in this work could promote the controlled synthesis of large-area TMDs single crystal film and the scalable fabrication of high-performance electronic devices.

Superconducting 2D NbS2 Grown Epitaxially by Chemical Vapor Deposition

“… 30 At the early stage of growth, nucleation takes place on the surface of sapphire with an initial random orientation of the crystallites. 31 For relatively low growth temperatures (e.g., 750 °C), the small crystallites do not have enough thermal energy to explore the energy landscape by rotation before they grow to big crystals. As a result, NbS 2 crystals with a small domain size and a random orientation are observed in Supplementary Figure S1a .…”

Mechanisms beyond energetics revealed by multiscale kinetic modeling of 2D‐material growth and nanocatalysis

“…73,74 Understanding key factors for anisotropic growth then facilitates its controllable synthesis. 75,76 As shown in Figure 3(a), anisotropic WS 2 nanoribbons were successfully fabricated by a space-confined and substrate-directed strategies combined with the chemical vapor deposition method. 77 In experiments, one piece of SiO 2 / Si substrate was placed at the center of furnace with tungsten trioxide powder randomly scattered on the substrate surface, and another piece of SiO2/Si substrate was put facedown above the bottom substrate forming a confined space.…”

“…However, some typical 2D materials such as transition‐metal dichalcogenides (TMDCs) tend to form isotropic nanoplates rather than anisotropic nanoribbons 73,74 . Understanding key factors for anisotropic growth then facilitates its controllable synthesis 75,76 …”

Epitaxy of 2D Materials toward Single Crystals

“…Up to now, different 2D materials have been epitaxially grown on various single‐crystal substrates, including graphene and hexagonal boron nitride (h‐BN) on copper (Cu), [ 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ] germanium (Ge), [ 53 , 54 , 55 ] other transitional metals [ 56 , 57 , 58 , 59 , 60 , 61 ] and metal alloys, [ 62 , 63 , 64 , 65 ] and transition metal dichalcogenides (TMDCs) on sapphire, [ 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 ] mica, [ 75 , 76 ] and gold (Au). [ 77 , 78 , 79 , 80 , 81 ] The heart issue in the epitaxy is to regulate the orientations of the 2D domains which is closely related the interplay between 2D domains and the single‐crystal substrates.…”