Research On The Preparation And Optical Properties Of Quasi One-dimensional Layered Material KP₁₅

Due to the high exposure of surface atoms,atomic thickness,strongin-plane covalent bond,and large lateral size,2D materials have been applied in electronic/optoelectronic devices,supercapacitors,Li-ion batteries and flexible devices.Reducing the symmetry of the 2D lattice system could lead to high structural anisotropy and further cause a strong anisotropy of their electronic structures and optical properties.Such anisotropic 2D materials are promising for fabricating high performance electronic and optical devices,and researching many-bodyinteractions.Thus,2D materials with high anisotropy can effectively increase the number of possible applications,but the development of 2D high in-plane anisotropic materials faces a challenge.Specifically,light-induced oxidation of black phosphorus causes it to degrade when exposed to the atmosphere.The carrier mobilities of ReS₂ is low,and As,the basic component element of GeAs/As_1-xP_x is toxic.Here in this study,a new kind of anisotropic layered materials:KP₁₅ has been systematically studied.Concrete results are as follow:?1?The KP₁₅ single crystals were prepared by gas phase transfer method.It's detailed crystal structure of KP₁₅ first was confirmed by single-crystal XRD measurement.The anisotropic electron-density distribution of KP₁₅ was calculated by the maximum entropy method and first-principles calculations.The interaction between adjacent layers,adjacent P atoms along the P tubes,K atoms with P atoms,was confirmed.?2?Few layers KP₁₅ were exfoliated by mechanical and liquid exfoliation and Hansen paramaters of KP₁₅ have been confirmed.The concentration of KP₁₅suspension exfoliated by liquid exfoliation was up to 0.0477 mg/mL.The thicknesses of 63.1%of KP₁₅ nanowires exfoliated by liquid exfoliation were within 0²5 nm;the widths of 78%of those KP₁₅ nanowires were less than 120 nm.The theoretical calculation results,sections,and the orientation of KP₁₅ nanowires imply that the P tubes in one layer can be separated.Thus,with further effort to optimise the process parameters,KP₁₅ nanowires consisting of only a few P tubes may be achieved.?3?The effect of vacancies on K?P13?P14?P15 have been studied by first-principles calculations,PL,and UV absorption spectrometry.?4?The F-P effect has been found in KP₁₅ bulks and the refractive index of KP₁₅have been confirmed by ellipsometer.?5?The stability of KP₁₅ in atmosphere has been tested by Raman and theoretical calculation.?6?Thickness,temperature,and polarization direction of excitation laser dependent Raman and PL of KP₁₅ nanowires were studied.The polarized spectrum results reveal the intrinsic anisotropy of lattice structure of KP₁₅.Therefore,it is expected that polarized measurements is effective for quickly determining the orientation of KP₁₅.Meanwhile,we found two neutral exciton emissions from KP₁₅nanowires.The high energy emission?1.83 eV?seems to have been produced by the surface state,and the lower one?1.67 eV?may have been produced by the original crystal structure of KP₁₅.The KP₁₅ nanowires also exhibited a large exciton binding energy?98 meV?,which is one order of magnitude greater than those of common semiconductors.The above work establish a foundation for the application of KP₁₅ in semiconductor field and provide ideas for the development of new low-dimensional high anisotropy materials.Meanwhile,our group cooperated with Professor Pingxue Li and successfully use KP₁₅ to produce mode-locked laser.It provides a new idea for the device development for KP₁₅.