Indirect Bandgap Puddles in Monolayer MoS2 by Substrate-Induced Local Strain

An unusually large bandgap modulation of 1.23-2.65 eV in monolayer MoS2 on a SiO2/Si substrate is found due to the inherent local bending strain induced by the surface roughness of the substrate, reaching the direct-to-indirect bandgap transition. Approximately 80% of the surface area reveals an indirect bandgap, which is confi rmed further by the degraded photoluminescence compared to that from suspended MoS2.