Epitaxial Atomic Substitution for MoS₂–MoN Heterostructure Synthesis

Abstract

Integrating different two-dimensional (2D) crystals is highly demanded for advancing their application in nextgeneration electronics. 2D transition metal carbides, nitrides, and carbonitrides (MXenes), as new members in the 2D family, are promising candidates for 2D electrodes because of their high conductivity and stability. However, integrating MXenes with other 2D semiconductors has been underdeveloped due to the limitation of top-down etching synthesis of MXenes. Our recent development of atomic substitution synthesis achieved ultrathin non-van der Waals (non-vdW) transition metal nitrides (TMNs) through the conversion of vdW transition metal dichalcogenides (TMDs), opening opportunities of combining TMDs with TMNs via controllable partial conversion. Here, we perform an in-depth study of the atomic substitution process from semiconducting MoS 2 to metallic MoN and realize both lateral and vertical MoN− MoS 2 heterostructures via edge and surface epitaxial conversion, respectively. The structural evolution investigation from MoS 2 to MoN using high-resolution transmission electron microscopy suggests atomically bonded interface for lateral heterostructures and moirépattern in vertical heterostructures. Moreover, mask-assisted atomic substitution is applied to create patterned MoN−MoS 2 − MoN lateral heterostructures. Electrical measurements reveal a Schottky barrier height of meV for a three-layer MoS 2 −MoN interface, showcasing the potential of atomically bonded lateral heterostructures for MoS 2 electronics with MoN as contact electrodes.

Heteroepitaxy of 2D CuCr2Te4 with Robust Room‐temperature Ferromagnetism

“…The thickness of bottom Cr 2 Te 3 layer and top CuCr 2 Te 4 layer is ≈17.8 and 5.6 nm, respectively (Figure 1f). Besides, some CuCr 2 Te 4 /Cr 2 Te 3 heterostructures that basically show no difference in height between Cr 2 Te 3 and the heterostructure region were also observed, which may be attributed to the existence of epitaxial atomic substitution during the growth process [ 22 ] (Figure S3, Supporting Information).…”

Advancing Nanoelectronics Applications: Progress in Non-van der Waals 2D Materials

“…62,63,91 Li et al further showed that the conversion initiates from both the edge and the defect sites on the surface of a precursor flake, followed by an epitaxial conversion process. 136,137 The converted nitride crystals are observed to share the same crystal orientation as the MoS 2 precursor flakes.…”

“…(a, b) Schematic illustration of fabrication process for lateral (a) and vertical (b) heterostructures. (c–f) High resolution planar TEM image (c) and fast Fourier transformation (FFT) patterns (d–f) of each section in the MoS 2 –MoN lateral heterostructure: (d) MoN, (e) interface, (f) MoS 2 . Images were reproduced with permission from ref .…”

“…(c–f) High resolution planar TEM image (c) and fast Fourier transformation (FFT) patterns (d–f) of each section in the MoS 2 –MoN lateral heterostructure: (d) MoN, (e) interface, (f) MoS 2 . Images were reproduced with permission from ref . Copyright 2022 American Chemical Society.…”

“…The process involves patterning the flakes with polymers followed by plasma etching and metal deposition, where polymer residues, overetching, and edge exposure inevitably degrades the connection between 2D flakes and metal electrodes . Li et al demonstrated an alternative approach to fabricate the edge contact by converting the two ends of a MoS 2 flake into MoN with NH 3 , while the middle is passivated by an Al 2 O 3 mask (Figure a) . The obtained MoN-MoS 2 –MoN structure is a metal–semiconductor-metal heterojunction with atomically bonded seamless one-dimensional (1D) interfaces.…”