Molybdenum Disulfide Nanoribbons with Enhanced Edge Nonlinear Response and Photoresponsivity

MoS₂ nanoribbons have attracted increased interest due to their properties, which can be tailored by tuning their dimensions. Herein, the growth of MoS₂ nanoribbons and triangular crystals formed by the reaction between films of MoOx (2<x<3) grown by pulsed laser deposition and NaF in a sulfur-rich environment is demonstrated. The nanoribbons can reach up to 10 µm in length, and feature single-layer edges, forming a monolayer–multilayer junction enabled by the lateral modulation in thickness. The single-layer edges show a pronounced second harmonic generation due to the symmetry breaking, in contrast to the centrosymmetric multilayer structure, which is unsusceptible to the second-order nonlinear process. A splitting of the Raman spectra is observed in MoS₂ nanoribbons arising from distinct contributions from the single–layer edges and multilayer core. Nanoscale imaging reveals a blue-shifted exciton emission of the monolayer edge compared to the isolated MoS₂ monolayers due to built-in local strain and disorder. We further report on an ultrasensitive photodetector made of a single MoS₂ nanoribbon with a responsivity of 8.72 × 10² A W⁻¹ at 532 nm, among the highest reported up-to-date for single-nanoribbon photodetectors. These findings can inspire the design of MoS₂ semiconductors with tunable geometries for efficient optoelectronic devices.