Preparation And Photoelectric Detection Performance Of Two-dimensional Metal (Mn,In) Phosphorous Chalcogenides

Two-dimensional(2D)layered metal phosphorus trichalcogenides(MPTs)have gained widespread interest and shown versatile applications in electronics,optoelectronics,energy devices and spintronics due to their layered characteristics,rich varieties of band structure and intrinsic magnetism.However,the research about optical and optoelectronic properties of 2D MPTs is still in the initial stage.Mn PSe₃ and In_2/3PSe₃,as scarce direct-bandgap materials of MPTs,have higher ability in light absorption efficiency than indirect-bandgap MPTs as well as smaller bandgap and better conductivity which are expected to realize the high-performance photoelectric detection devices.However,there is no research reported on the optoelectronic property of Mn PSe₃ and In_2/3PSe₃.Therefore,we prepare high-quality 2D Mn PSe₃ and In_2/3PSe₃ nanosheets and characterize their structure,optical properties and photoelectric detection performance.The main research contents are as follows:(1)High-quality Mn PSe₃ single crystals are synthesized by chemical vapor transport method,and 2D Mn PSe₃ nanosheets with thickness of 1.5 nm are prepared via mechanical exfoliation method.Systematical Raman investigations are performed for Mn PSe₃nanosheets to assign Raman modes and the variation of peak positions with thickness and temperature are studied.Low-temperature electrical transport indicates a semiconductor nature of 2D Mn PSe₃.The photodetector based on Mn PSe₃ nanosheet displays best performance in the ultraviolet range among MPTs with high responsivity of 22.7 A/W and detectivity of 3.1×10¹² Jones,which originate from the photogating effect.(2)High-quality 2D In_2/3PSe₃ crystals are isolated via mechanical exfoliation method from the bulk crystals synthesized by chemical vapor transport method,the thickness of the thinnest nanosheet is 3.7 nm.Second harmonic generation spectroscopy is adopted to verify the broken-symmetry structure of In_2/3PSe₃.Transition mechanism and separation characteristics of photogenerated carriers are revealed by photoluminescence(PL)and time-resolved PL spectra.What's more,the photodetector based on In_2/3PSe₃ nanosheets exhibits an ultra-low dark current(25 f A),excellent detectivity(6.28×10¹¹ Jones),high on/off ratio(4×10⁴),and ultra-fast response rate(14?s/24?s).The ultra-fast response owns to the rapid separation and recombination of photogenerated electrons and holes induced by photoconductive effect.