Fig. 5

Narrow bandgap bilayer PtSe₂ via defect engineering. a Comparison of photodetectors operated at different wavelengths, based on two-dimensional materials, such as graphene^{35,36,39,40,41,42,43}, MoS₂^24,26,27, black phosphorene^{28,29,30,31,32}, WS₂^44,45, WSe₂⁴⁶, MoSe₂⁴⁷, SnSe₂⁴⁸, SnS₂⁴⁹, InSe^20,21, In₂Se₃^22,23, TiS₃²⁵, CuIn₇Se₁₁⁵⁰, and black AsP^38,51. The mid-infrared range is rarely explored besides graphene. b Photoresponse spectrum of the photodetector based on the Ar plasma treatment bilayer PtSe₂ FET (20 s), measured by FTIR internal source. c, d X-ray photoelectron spectroscopy (XPS) spectrum of Pt 4f (c) and Se 3d (d) core level peaks of PtSe₂ with Se vacancies. e, f Density of states (DOS) of bilayer PtSe₂ with 3% (e) and 6.8% (f) Se vacancy concentrations by first-principles calculations. g The experimental (blue) and theoretical (red) bandgap evolution of bilayer PtSe₂ with different Se vacancy concentrations