Efficient MoWO₃/VO₂/MoS₂/Si UV Schottky photodetectors; MoS₂ optimization and monoclinic VO₂ surface modifications

Abstract

The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS₂) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO₂. MoWO₃/VO₂/MoS₂ photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO₃/VO₂/MoS₂/Si with MoS₂ deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO₂ layer on MoS₂/Si causes a redshift and intensive MoS₂ Raman peaks. Interestingly, the incorporation of VO₂ dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO₂/(30 s)MoS₂/Si from < 1 to > 1. By increasing the deposition time of MoS₂ from 60 to 180 s, the relative intensity of the B-exciton/A-exciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO₂/(60 s)MoS₂/Si structure. Both the VO₂/(60 s)MoS₂/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS₂/Si structure. The MoWO₃/VO₂/(60 s)MoS₂/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 × 10⁸ Jones detectivity, and ~ 1.0 × 10¹⁰ quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at ~ 40 °C.