Growth and Simultaneous Valleys Manipulation of Two-Dimensional MoSe₂-WSe₂ Lateral Heterostructure

Abstract

The covalently bonded in-plane heterostructure (HS) of monolayer transition-metal dichalcogenides (TMDCs) possesses huge potential for high-speed electronic devices in terms of valleytronics. In this study, high-quality monolayer MoSe-WSe lateral HSs are grown by pulsed-laser-deposition-assisted selenization method. The sharp interface of the lateral HS is verified by morphological and optical characterizations. Intriguingly, photoluminescence spectra acquired from the interface show rather clear signatures of pristine MoSe and WSe with no intermediate energy peak related to intralayer excitonic matter or formation of MoWSe alloys, thereby confirming the sharp interface. Furthermore, the discrete nature of laterally attached TMDC monolayers, each with doubly degenerated but nonequivalent energy valleys marked by (K, K') for MoSe and (K, K') for WSe in k space, allows simultaneous control of the four valleys within the excitation area without any crosstalk effect over the interface. As an example, K and K valleys or K' and K' valleys are simultaneously polarized by controlling the helicity of circularly polarized optical pumping, where the maximum degree of polarization is achieved at their respective band edges. The current work provides the growth mechanism of laterally sharp HSs and highlights their potential use in valleytronics.

Characterization of atomic defects on the photoluminescence in two‐dimensional materials using transmission electron microscope

“…The lateral heterostructure is another kind of defects in 2D crystal materials, it plays a crucial role in high‐speed electronic devices such as high‐mobility field‐effect transistors . Here Ullah et al research the PL properties of lateral heterojunction constituted by WSe 2 and MoSe 2 . To observe the interface properties on a truly atomic scale, Figure A shows a clear image of the lateral heterojunction between WSe 2 and MoSe 2 filmed by high‐angle annular darkfield (HAADF)‐STEM.…”

“…95 Here Ullah et al research the PL properties of lateral heterojunction constituted by WSe 2 and MoSe 2 . 96 To observe the interface properties on a truly atomic scale, Figure 5A shows The atomic number of W is larger than Mo, thus W atoms is brighter than Mo in Z-contrast image. Distribution condition of different atoms at the interface between the two compounds can be vividly seen.…”

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

“…[13,[76][77][78][79][80] While two-dimensional materialsbased vertical heterostructures are fabricated through transfer process generally. However, transfer methods are very complicated for multi-layer structure which lowers success rate.…”

“…Kim et al used physical layer deposition (PLD) method to electively deposit MoO3 and WO3 in different region to form MoSe2-WSe2 heterojunction with sharp interfaces. [76] Such in-plane heterojunctions preserve four Dirac valleys for future valleytronics. [76] However, uniformly deposition of precursors is acquired.…”

“…[76] Such in-plane heterojunctions preserve four Dirac valleys for future valleytronics. [76] However, uniformly deposition of precursors is acquired. Such deposition method is hard to achieve monolayer growth, which hinders its application in some conditions.…”