Enhancing Stability and Photoluminescence of Monolayer MoS2 by Encapsulation with Pulsed Laser Deposited Amorphous Boron Nitride

Abstract

Monolayer two-dimensional (2D) materials offer exciting opportunities for next-generation microelectronics and optoelectronics, however, their sensitivity to environmental exposure and energetic plasma species requires the development of precise and damage-minimized methods for their device integration and protective encapsulation. Here, we demonstrate a pulsed laser deposition (PLD) approach for encapsulating monolayer MoS2 on SiO2/Si with amorphous boron nitride, resulting in improved photoluminescence and enhanced environmental and thermal stability. By tuning background gas collisions and using in situ plasma diagnostics, the kinetic energy of BN plasma species is reduced from highly damaging values of ∼100 eV/B atom to sub-eV “soft landing” conditions. This kinetic-energy-controlled process preserves the structural integrity of monolayer MoS2 during encapsulation and minimizes defect formation and strain, as confirmed by in situ Raman spectroscopy and ex situ electron microscopy. Photoluminescence and ultrafast pump-probe spectroscopy further reveal enhanced free exciton emission intensity and lifetime after air annealing, which are attributed to oxygen passivation of sulfur vacancies and suppression of nonradiative recombination pathways. Our work establishes kinetic-energy-controlled PLD as a robust method for damage-minimized direct encapsulation of monolayer 2D materials, enabling stable and high-performance devices.