| The two-dimensional MoS2 has excellent optical and electrical properties and has become a hotspot in recent years.The preparation of high quality,large size monolayer Mo S2 is still a challenging subject,at the same time,there is no clear understanding of the shape evolution mechanism and surface defect distribution of Mo S2.In this paper,two-dimensional MoS2 was prepared by CVD?chemical vapor deposition?,and we explored the growth process and shape evolution mechanism of monolayer Mo S2,the distribution of Mo S2 surface defects was studied by fluorescence and Raman spectroscopy,at the same time,the effects of BPO on the optical properties of monolayer Mo S2 were investigated by investigating the changes of fluorescence and Raman spectra of MoS2 samples treated with BPO?benzoyl peroxide?.High quality,large size MoS2 samples were successfully prepared in aerobic systems,and characterized by scanning electron microscopy?SEM?,atomic force microscopy?AFM?,Raman spectroscopy?Raman?,fluorescence spectroscopy?PL?.The introduction of oxygen in the CVD system regulates the ratio of S: Mo in the preparation experiment,while reducing the nucleation sites in the reaction.The Raman spectrum of Mo S2 was collected and it was found that the E2 g peak gradually shifted red and the A1 g peak gradually shifted blue as the number of Mo S2 layers increased,the monolayer Mo S2 had strong fluorescence,with the increase of the number of Mo S2 layers,the intensity of A exciton was gradually weakened.Based on the S: Mo ratio,we established the MoS2 shape evolution model,and explained the evolution of Mo S2 with different morphologies.Compared with the triangular,quadrangular and pentagonal Mo S2 fluorescence spectra,we found that the fluorescence intensity of hexagonal MoS2 increased sharply,while the fluorescence characteristic peak was blue shift.The fluorescence spectra of MoS2 surface were collected and found that the defects of hexagonal MoS2 were concentrated in the central region,while the triangular Mo S 2 defects were concentrated in the vertex and boundary.The fluorescence and Raman spectra of Mo S2 samples were observed before and after treatment with BPO.It was found that the fluorescence intensity of the edge region of the Mo S2 was increased after the Mo S2 sample was treated by BPO,also the blue-shifted of the Raman peak A1 g was observed.With the increase of the laser power,the intensity of B exciton peak and the A exciton peak increased gradually,and the magnitude of the increase of the A exciton peak intensity was larger than that of the B exciton peak.We believe that the cause of fluorescence enhancement,Raman peak A1 g peak blue shift may be due to BPO successful chemical modification of Mo S2,or a chemical adsorption mechanism. |
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