Photoluminescence quenching in monolayer transition metal dichalcogenides by Al2O3 encapsulation

We report the photoluminescence quenching in monolayer MoS2, MoSe2, WS2, and WSe2 by atomic layer deposited Al2O3 encapsulation. The negative shift and broadening of photoluminescence emission suggested electron doping after encapsulation. The further reduction, softening, and broadening of the A(1g) mode in Raman spectra also suggested electron doping after Al2O3 encapsulation. To investigate the origin of photoluminescence quenching, we fabricated bottom-gate MoS2 transistors on SiO2/Si substrates. Under a 405-nm-laser, Al2O3-encapsulated MoS2 transistors exhibited enhanced electron photocurrent, suggesting that photoluminescence quenching was dominated by hole transfer to encapsulation-induced trap states. These results demonstrated the importance of defect control for the dielectric deposition in achieving high-performance optoelectronic devices based on monolayer transition metal dichalcogenides. Published by AIP Publishing.