Preparation Of Standing WS₂ And ZnO&WS₂ Micro-nano Film Materials And Study Of Nonlinear Optical Properties

With the rapid development of science and technology,modern optics promotes the integration and progress of multiple disciplines.Nonlinear optics is an important branch of optics and a frontier subject of modern optics.It has important scientific value and significance in laser technology,information image processing and storage.In the field of nonlinear optics,researchers promote its development by exploring new materials,discovering new phenomena and revealing new problems.At present,many research groups at home and abroad have carried out extensive research on the advantages of many optoelectronic properties of bandgap semiconductor materials.Transitional metal dichalcogenides are a kind of material that can change the optical band gap by adjusting the number of layers.WS₂,as one of them,will also have great development in the field of nonlinear optics.Meanwhile,ZnO material has excellent nonlinear optical properties.By combining the two materials,the nonlinear optical properties of composite materials can be studied effectively.In this thesis,WS₂films and ZnO&WS₂(ZnO@WS₂,WS₂@ZnO)heterojunction composite films were prepared on quartz substrate by radio frequency magnetron sputtering.The effects of sputtering parameters on the surface morphology,optical absorption,crystal structure,composition ratio and chemical valence of the sample were studied.The nonlinear absorption characteristics of WS₂films and ZnO@WS₂heterojunction composite films were studied by using open-aperture femtosecond Z-scan technique to reveal the physical mechanism of nonlinear absorption.And the following aspects are discussed:(1)WS₂films with different experimental parameters were obtained by controlling the substrate temperature and sputtering time.Morphology analysis shows that the standing growth structure and sickle-like texture of WS₂film can be obtained with the increase of substrate temperature or the increase of sputtering time.The crystallinity of WS₂films increases with the increase of substrate temperature or the prolonging of sputtering time,and the linear optical absorption in the visible region is enhanced.The growth mechanism of standing WS₂films were analyzed by the morphology change and cross-section of WS₂..(2)A series of ZnO&WS₂heterojunction composite films were obtained by changing the sputtering time of WS₂,the substrate temperature of ZnO and the sputtering order.The morphology analysis shows that the morphology analysis shows that using WS₂film can promote the growth of ZnO flake structure.When the ZnO-100?film is used as the substrate,WS₂participates in the recrystallization process of ZnO,and the surface of the composite film appears granular.The elemental ratios and valence states of heterojunction composite films show the different ratios of Zn²⁺,O^2-,S^2-and W⁴⁺.The position and shape of the diffraction characteristic peaks in the composite films are similar to those of ZnO(002)and WS₂(002)/(101).The linear optical absorption shows that the heterojunction structure of the composite film is type II(Ride type).The growth mechanism of the composite film was analyzed.(3)Z-scan technology was used to test WS₂films and ZnO@WS₂heterojunction composite films respectively,and the"W"and"M"type data graphs of the Z-scan curve of the opening were analyzed.The obtained Z-scan images are classified and discussed.The results show that the WS₂film has two-photon absorption process and transitions from saturation absorption to saturation absorption.ZnO@WS₂heterojunction composite films show ground state or excited state saturation absorption or reverse reverse saturation absorption induced by multi-photon absorption.The nonlinear absorption values of WS₂film and ZnO@WS₂heterojunction composite film were calculated.Therefore,WS₂thin film and ZnO&WS₂heterojunction composite film will be promising candidate materials in nonlinear optical materials.