Alkali-assisted synthesis of multilayer crystalline MoS2 nanoribbons with 2D edges, and Schottky barrier observation on MoS2 nanoribbon-Au/Cr junction

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Chemical vapor deposition (CVD) is an extensively studied process for 2D transitional metal dichalcogenides (TMDs) synthesis, which has demonstrated significant potential. Considerable efforts have been focused on the studies of growth parameters such as operating pressure, temperature, and concentrations of chemical precursors to achieve desired film quality and number of layers. CVD of 2D TMDs has faced multiple variations including the use of growth seed promoters and alkali metal halide salts. Their role of liquefying or stabilizing transition metal oxides can be employed to reduce transition metal oxides melting point (by forming molten salt precursors such as Na2Mo2O7, Na2MoO4 and Na2WO4), and facilitate vapour–liquid–solid (VLS) phase reaction[1]. This can be an attractive approach to induce directional or lateral growth of MoS2 crystals, achieving direct bottom-up synthesis.

In this study, we demonstrate an alkali-assisted synthesis of aligned multilayer MoS2 nanoribbons. The MoS2 nanoribbons are formed by VLS reaction between MoOx ultra-thin films grown using pulsed laser deposition, followed by NaF layer deposition and annealing in sulfur-rich environment at 800oC[2]. The growth process evolves via emergence of Na–Mo–O liquid phase, which mediates the formation of MoS2 multilayer nanoribbons in a sulfur-rich environment. Moreover, the as-grown MoS2 nanoribbons are surrounded by mono- and multilayer triangles of MoS2, and exhibit a preferential alignment defined by both MoS2 crystal symmetry and sapphire substrate. The presence of monolayer-to-multilayer junction forms a heterojunction due to a significant bandgap difference between multilayer MoS2 and 2D MoS2 layer. In order to study MoS2 optoelectrical properties, we have fabricated an electrical device structure (Fig.1a) with Au/Cr electrodes placed along and perpendicular the nanoribbon’s growth axis. We found that MoS2 nanoribbon based electrical device exhibit high photoresponsivity at 532 nm, and by performing photocurrent mapping (Fig.1b) we observe photocurrent amplification at the interface between MoS2-Au/Cr contacts, induced by built-in electric field due to Schottky barrier formed.
Period20 May 202423 May 2024
Event title2D Transition Metal Dichalcogenides 2024
Event typeConference
LocationHong Kong, Hong KongShow on map
Degree of RecognitionInternational


  • 2D materials
  • TMD
  • 2D growth
  • Monolayer
  • Chalcogenides
  • Synthesis
  • Oxides
  • Nanomaterials
  • Semiconductor