Heteroatomic stitching of broken WS2 monolayer with enhanced surface potential

Abstract

Sub-nanometre thick two-dimensional (2D) materials suffer from severe cracking during the high temperature chemical vapour deposition growth process. The cracking can be utilised to generate more active edges. These active edges can be stitched with a homo- or hetero-material. While the direct growth of 2D-heterostructures is mostly limited to a small fraction of outer edges of monolayer flakes, the cracked monolayers can be utilised to produce a large fraction of heterostructures. Heterostructures are important for developing multifunctional components for nanoscale electronics and optoelectronics. In this work, we demonstrate the formation of WS₂–MoS₂ heterostructures in large fractions by atomic stitching of cracked WS₂ monolayers with the sequential growth of MoS₂. Aberration-corrected scanning transmission electron microscopy and Raman spectroscopy have been utillised to probe fine details on the stitched interface between WS₂ and MoS₂. Growth of MoS₂ domains were observed to take place at the terminating edge of cracked WS₂, which then merged to form MoS₂ multilayers at the cracked site. Growth of MoS₂ at the opposite edges of WS₂ eventually results in a MoS₂–MoS₂ junction with a Σ = 7 tilt boundary. Kelvin probe force microscope (KPFM) measurement from the stitched region revealed that the work function of WS₂ is ∼32.46 meV higher than that of MoS₂, which also closely matches with the Fermi energy difference between these two materials. With the aid of an atomic force microscope and KPFM, the surface potential width at the stitched region was found to be ∼5 times higher than the actual width of the interface, confirming the modulation of properties near the interface.