Synthesis And Raman Characteristic Of Two Dimensional Material Molybdenum Disulfide And Iron Phosphorus Sulfur(Selenium)

Since the single-layer graphene was successfully prepared in 2004,two-dimensional graphene has large potential in the field of optoelectronics due to its high electron mobility and high thermal conductivity.As a two-dimensional material,graphene has good electrical properties,but its zero band gap limit its application in the field of optoelectronics devices.When researchers were looking for similar two-dimensional materials,they found that molybdenum disulfide,which has a layered two-dimensional structure similar to graphene,also has excellent electron mobility and band structure.And the single-layer molybdenum disulfide is a semiconductor with direct band gap of about 1.9e V.This property makes molybdenum disulfide have new application ideas in addition to its wide application in the fields of lubrication and catalysis.However,prepare of high-performance thin-layer molybdenum disulfide is a very critical issue.Another two-dimensional material iron phosphorus sulfur(selenium)with a layered two-dimensional structure is a typical compound of transition metal thiophosphite,and it exhibits special magnetic anisotropy.In particular iron phosphorous sulfur(selenium)can be observed its structural phase transition and magnetic order reversal when applying high-pressure on it.The research on these two types of structure phase transition has deepen people's understanding of their physical properties.The main research content of this essay is divided into two parts: the preparation of thin-layer molybdenum disulfide and the high-pressure experiment of iron,phosphorus and sulfur(selenium).The main experimental method is Raman spectroscopy.The first part of this essay describes the layered molybdenum disulfide prepared by chemical vapor deposition(CVD)with molybdenum oxide and sulfur vapor raw materials and the layered molybdenum disulfide prepared by metal organic chemical vapor deposition(MOCVD)and the basic physical properties characterization.Then explore how the MOCVD method uses molybdenum hexacarbonyl and ethyl sulfide/hydrogen sulfide as raw materials to prepare layered molybdenum disulfide to make its properties closer to a single layer and uniformity on a larger scale.The main research method is to influence the final preparation result by adjusting the growth parameters used in the crystal growth process,so as to further understand the mechanism of thin-layer crystal growth.The preparation results are given by common optical characterizations such as Raman spectroscopy.The second part of this topic is to study the phase transition of iron phosphorus sulfur(selenium)single crystal under high pressure.First,the single crystal was prepared by chemical vapor transport(CVT),and the iron phosphorus sulfur(selenium)sample was prepared by the micromechanical force peeling method and transferred to the high-pressure experimental device diamond anvil.Then,high-pressure Raman spectroscopy was applied to characterize the iron-phosphorus-sulfur(selenium)single crystal under high pressure.Since it was found in the investigation that the structural phase transition of iron phosphorus sulfur(selenium)exhibits the transformation of the lattice structure from the mott insulating state to the metallic state,and this phase transition has been confirmed by the results of X-ray diffraction,in this study,from the perspective of high-pressure Raman technology,we discuss the structural phase transition behavior under high-pressure.Finally,the magnetic sequence flipping phenomenon caused by the structural phase transition can also be obtained from the analysis of high-pressure Raman spectroscopy.