Vertically Stacked MoSe₂/MoO₂ Nanolayered 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 MoSe 2 /MoO 2 heterostructures with the thickness of MoO 2 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 MoO 2 flake vertically stacked MoSe 2 /MoO 2 heterostructure with the merits of a photoresponsivity of 100.86 mA·W –1 and a detectivity of 23.4 × 10 9 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 MoO 2 flake heterostructure (thickness ∼ 105 nm). The enhanced mechanism originates from high absorption efficiency, high carrier conductivity, and better contact of thin metallic MoO 2 flakes compared to the thick MoO 2 flakes heterostructure, which relates to various Fermi energy levels of the two different MoO 2 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.