Simultaneous photoluminescence enhancement in CVD grown single layer MoS2 and TiO2 NRs in the MoS2@TiO2 heterojunction

Abstract

Photoluminescence (PL) enhancement in MoS2 by suppressing the trions and in TiO2 nanostructure by tuning the defect concentration is important for various optoelectronic applications. Hydrothermally grown vertically aligned rutile TiO2 NRs array on FTO coated glass substrate was used as the substrate/template for the chemical vapour deposition (CVD) growth of uniform monolayer MoS2 (1L-MoS2) thin film over TiO2 NRs. Here, we demonstrate the simultaneous PL enhancement of 1L-MoS2 and TiO2 NRs in the HS, as compared to their pristine counterparts. Raman studies confirm the large area monolayer growth of MoS2 over TiO2 NRs. Uniform decoration with 1L-MoS2 was confirmed by HRTEM. The intensity of characteristic PL emission for 1L-MoS2 (∼662 nm) and rutile TiO2 NRs (∼810 nm) are observed to be enhanced by ∼80 and ∼5 times, respectively after the formation of heterojunction. The enhancement of the PL in the HS is attributed to charge transfer from MoS2 to TiO2 resulting to the conversion of trion to neutral exciton for the MoS2. In the course of CVD growth of MoS2, the Ti interstitial and oxygen vacancy defects in the rutile TiO2 increased substantially, resulting to the enhancement in PL emission.