Tuning photoluminescence behaviors in strained monolayer belt-like MoS2 crystals confined on TiO2(001) surface

Abstract

We report on a monolayer (ML) MoS2 belt-like single crystal directly fabricated on the Rutile-TiO2(001) surface via chemical vapor deposition (CVD). We find that the photoluminescence (PL) behaviors in the ML MoS2 single crystal strongly depend on their shapes and the interface of MoS2/TiO2. Compared with the as-grown triangular ML MoS2, the PL peak position is in a blue shift and the PL intensity is increased for the as-grown ML MoS2 belt. Moreover, the PL peak position is in the blue shift by about 38 meV and the intensity is enhanced by nearly 15 times for the as-grown ML MoS2 belt crystal on TiO2 than those samples transferred onto SiO2/Si substrate. This special PL behavior can be attributed to the in-plane compressive strain that is introduced during the CVD growth of ML MoS2 belts confined by the substrate. The energy band of the strained ML MoS2 belt is changed with an up-shift in the conduction band minimum (VBM) and a down-shift in the valence band maximum (CBM), and the band gap is thus enlarged. This results in the energy band structural realignment in the interface of MoS2/TiO2, thereby weakening the charge transferring from the TiO2 substrate to MoS2 and suppressing the concentration of charged excitons to finally enhance the PL intensity of the ML MoS2 belt. The substrate-confined ML MoS2 belts provide a new route for tailoring light-matter interactions to upgrade their weak quantum yields and low light absorption, which can be utilized in optoelectronic and nanophotonic devices.