The Study Of Surface Property Modification And Enhanced Raman Scattering Based On Two-dimensional MoTe₂

Molybdenum distelluride（MoTe₂）surface enhanced Raman scattering（SERS）substrates have drawn intense attention due to their excellent spectral reproducibility,high uniformity and perfect antiinterference ability.However,the Raman enhancement based on two-dimensional（2D）MoTe₂/SERS substrate is derived from the charge transfer between MoTe₂ and probe molecules,the inferior detection sensitivity and low enhancement have seriously limited its practical application.Therefore,improving the SERS performance of 2D material has become a widely studied problem.At present,the commonly SERS performance regulation methods include regulating the materials growth process,electron beam irradiation and laser burning.These methods enhance the SERS effect by modifying the band gap,stoichiometry and crystal structure of 2D materials or introducing defects.However,these methods have some inevitable shortcomings.For instance,laser burning is limited by the low processing area and nonuniform surface after treatment.Electron beam irradiation could effectively create defects in a large area,however,it is difficult to control the doping degree precisely.Plasma and Ultraviolet（UV）-Ozone surface modification technology has gradually attracted people’s attention due to its flexible,mild,controllable characteristics and large-area processing.In this thesis,plasma and UV-Ozone surface modification technology are used to treat 2D MoTe₂ surface to achieve precise regulation and enhancement of SERS performance.The main research contents are summarized as follows:1、Hydrogen plasma is used to modify the MoTe₂ substrate to achieve the SERS improvement.The result show that none damage was observed on sample surface after hydrogen plasma treatment.Moreover,the P-type doping and lattice distortion are introduced into MoTe₂ substrate.P doping makes the Fermi level of MoTe₂ move down,and the lattice distortion weaken the binding ability of the surface to electrons.These two factors jointly promote the charge transfer between Rhodamine6G（R6G）molecule and MoTe₂ substrate,and finally improve the SERS effect.After hydrogen plasma treatment,the limit of detection of R6G even reaches 10^-13M and the corresponding enhancement factor is as high as 1.83×10⁶,far more than the other 2D materials and nonmetal oxide substrates.In the experiment,the Rhodamine B（Rh B）molecules is used to verify the universality of plasma treated samples.The research results show that the limit of detection on the hydrogen plasma treated substrates could reach 10^-11M.Thus,it is concluded that plasma treatment is an effective means to modulate SERS performance.2、UV ozone is used to modify the thickness of MoTe₂ substrates to realize the accurately regulation and the enhancement of SERS performance.It is found that the thickness of MoTe₂decreases layer by layer with the increase of processing time.Raman signal of R6G molecules on MoTe₂ substrates gradually increases as the thickness decreases,and the SERS enhanced effect of monolayer samples is the optimized.This can be attributed to the transition from the direct band gap to indirect band gap when the multi-layer sample is thinned to be monolayer,which is beneficial to the charge transfer between MoTe₂ substrate and R6G molecule.In the process of ozone treatment,P doping is induced into MoTe₂ film,which improves the charge transfer between R6G molecule and MoTe₂ substrate.With the increase of treatment time,the P doping degree gradually intensifies,resulting in the gradual enhanced the Raman signal,so as to realize the precise regulation and control of SERS performance.Finally,the detection limits of ozone-treated MoTe₂ substrates is investigated,and the results show that the limit of detection of the sample reaches 10^-11M and the corresponding enhancement factor is 4.65×10⁵,far better than other 2D materials and non-metal oxide substrates.