Research On Preparation And Properties Of Molybdenum DiSelenide Thin Films

The layer by layer structure transition metal dichalcogenide-molybdenum diselenide?MoSe₂?has gradually become a hot topic in the field of materials science.With the tunable bandgap of 2H phase and metallic 1T phase,the MoSe₂ thin film exhibits excellent performance on semiconductor electronic devices,optoelectronic conversion devices,catalysis,energy storage and other applications.However,how to prepare large-area and high quality MoSe₂ thin film still remains a big challenge,which inevitably limits the industrial application of MoSe₂.On the other hand,MoSe₂ has three different crystal structures.How to obtain the single phase structure and excellent semiconductor properties is a high priority of current research.Therefore,a straightforward and efficient preparation method will promote the extensive applications of MoSe₂ film.In this article,in order to solve these problems,two direct selenization methods for preparing MoSe₂ films have been demonstrated.MoSe₂ Thin Films Prepared by Selenium Molybdenum Thin Film Technology:In the experiment,molybdenum thin film was prepared by electron beam evaporation.After that,the pre-deposited molybdenum film was subjected to a selenization reaction by thermal evaporation Se powder to obtain a MoSe₂ film.The influences of selenium evaporation source temperature,substrate growth temperature and growth time parameters on the phase structure and stoichiometry of the molybdenum diselenide thin film were investigated.These parameters for the preparation of pure2H phase MoSe₂ were optimized deliberately.In order to further verify the semiconductor properties of our 2H-phase MoSe₂ thin film,the MoSe₂ thin film was used as the channel layer of the thin film transistor.The 100 nm-thick Ti was deposited by the magnetron sputtering as electrodes.Finally,the thin film transistor with bottom gate and top contact structure was fabricated on thermally oxidize SiO₂substrate.The output and transfer curve test results show that the channel layer conductance and gate voltage of MoSe₂ have the strong correlation controllability,confirming that the 2H phase MoSe₂ thin film prepared by the method of molybdenum selenide metal film with excellent semiconductor properties.Preparation of MoSe₂ Thin Film by Selenium Molybdenum Oxide Thin Film Technology:molybdenum thin films used as precursors for the preparation of MoSe₂requires a high growth temperature.In comparison,a method for preparing molybdenum diselenide thin films at a low temperature was demonstrated.Selenization reaction of MoO₃ and Se can produce high-purity MoSe₂ at a suitable temperature.SeO₂,a side reaction product,is a volatile gas discharged with the system exhaust.In this section,a layered?-MoO₃ thin film was prepared by Mo metal thin film annealing and oxidation technique.After the selenization of?-MoO₃thin film,a high-quality MoSe₂ thin film was prepared at a low temperature of 500?.The comprehensive analysis results of Raman spectroscopy,X-ray photoelectron spectroscopy and Transmission Electron Microscopy confirmed that the MoSe₂ thin film material prepared by the selenization MoO₃ film method has a high purity of 2H phase.