Vertically Stacked MoSe₂/MoO₂Nanolayered Photodetectors with Tunable Photoresponses

A variety of two-dimensional (2D) nanodevices with diverse optoelectronic properties have been successfully fabricated. A strategy for engineering 2D heterostructures high-performance devices rich in functions and adaptable for specific applications must be developed. Herein, two types of photodetectors fabricated through van der Waals interactions from vertically stacked MoSe2/MoO2 heterostructures with the thickness of MoO2 flakes at 25 and 105 nm, respectively, which exhibits metallic and semiconductor characteristics on elevation at thickness from 25 to 105 nm. A higher photoresponse can be obtained from the thin MoO2 flake vertically stacked MoSe2/MoO2 heterostructure with the merits of a photoresponsivity of 100.86 mA·W-1 and a detectivity of 23.4 × 109 Jones. The external quantum efficiency reaches 23.5% at bias of 3 V under the illumination of a monochromatic light at 532 nm, which is better than thick MoO2 flake heterostructure (thickness ∼105 nm). The enhanced mechanism originates from high absorption efficiency, high carrier conductivity, and better contact of thin metallic MoO2 flakes compared to the thick MoO2 flakes heterostructure, which relates to various Fermi energy levels of the two different MoO2 flakes photodetector. This work can provide an interesting route for engineering optoelectronic high-performance devices and developing a diverse photodetector on the basis of transition metal dichalcogenides (TMDs)/transition metal oxides (TMOs) heterojunction.