Study On High Pressure Modulation Of Excitons And Lattice Vibrational Behavior In Gase And Mose₂-mos₂ Heterostucture

Two-dimensional?2D?materials are special materials with a great variety of unique properties that make them highly attractive for fundamental studies of novel physical phenomena and for applications in field of electronics,transistors,light-emitting diodes and photodetectors.They also have attracted widespread concern of the academic community due to the effect of the interlayer coupling,when thinning down bulks to monolayers,the energy band structure of TMDs transform would make a huge difference.Moreover,the evolvements in the peeling of 2D materials by mechanical exfoliation method have opened new doors to different electronic gadgets.Since the weak van der Waals interlayer coupling is used,the lattice-matching requirement is relaxed.Thus,a huge number of combinations can be designed and explored.The interface can be atomically sharp and the junction region can be as thin as two atomic layers,which holds potential for P-N junction,photodetector,photovoltaic cell,transistor device applications.This dissertation takes GaSe,MoS₂ and MoSe₂ as examples to explore the behavior with the help of in-situ Raman spectroscopy under pressure and PL spectroscopy.Finding the pressure of metallization phase transition and the products after GaSe oxidation,studying the lattice vibration behavior of GaSe and MoS₂-MoSe2heterojunction?HS?crystal under high pressure.Main results are as followed.Firstly,Layered Gallium selenide?GaSe?was obtained by using mechanical exfoliation method.The photoluminescence?PL?and Raman spectra were used to measure the properties of the GaSe.And the high-pressure Raman spectra of bulk materials and thin-layer GaSe were obtained within pressure range of 0-30 GPa via a Diamond Anvil Cell?DAC?with inert argon used as pressure transmission medium?PTM?.The results show that bulk and thin-layered GaSe processed a phase transition around 28 GPa.As for oxidized few layered GaSe,a vibration mode at a position of250 cm^-11 was found by Raman spectra,which was confirmed as the Raman vibration mode of a-Se.The high-pressure Raman spectra of the oxidized thin layers GaSe were also investigated in this work.Secondly,A high-quality monolayer MoSe₂ and MoS₂ sample based on a diamond substrate was prepared,and A monolayer MoSe₂-MoS₂ HS was prepared.The renormalization of excitonic and vibrational systems was found for the first time,and modulation transformation of the excitonic and vibrational system dimension was achieved.A 3D interlayer exciton appeared in MoSe₂-MoS₂.In aspect of lattice vibration,the 3D B¹_2g?H?modes of MoSe₂-MoS₂ HS exhibits a blue-shift with the increasing pressure.The result of the renormalization of the exciton and vibration can provide basis and guidance for the application of flexible excitonic devices and the quantitative measurement of interlayer coupling strength.