Growth And Characterization Of The Rare Earth Element Doped MoS₂ Thin Films

Due to its unique atomic structure,valley-selective excitation and excellent optical and electronic properties,monolayer MoS₂ can be used to fabricate microelectronic devices with high on/off ratio and optical and electronic devices in visible range.However,the low absorption coefficient and defects of the monolayer affect its photoluminescence efficiency and optoelectronic properties.It is well known that the rare earth elements have abundant electron band structures.If the rare earth(RE)element are doped into monolayer MoS₂,it is possible to improve its absorption efficiency and photoluminescence,leading to its potential application as excellent optoelectronic devices.In this work,monolayer MoS₂ was grown by chemical vapor deposition.MoO₃and S powders were used as precursors,and argon was used as carrier gas.Monolayer MoS₂ was grown on a SiO₂/Si substrate after optimizing the growth parameters.Then,LuCl₃(or ErCl₃)was mixed into the previous precursors to grow RE-doped monolayer MoS₂.RE-doped monolayer MoS₂with large size of 80-100?m was obtained at 720?on the SiO₂/Si substrate assisted by Na Cl molten salt.The surface morphology and thickness of the sample were analyzed by optical microscope,scanning electron microscope,Raman spectroscopy and atomic force microscope,which shows that the grown thin film is the monolayer MoS₂.The energy dispersive X-ray spectrum analysis shows that the obtained films contain the doping rare earth element.The lattice constant measured by high-resolution transmission electron microscopy has a little shrinkage after doping.The X-ray photoelectron spectroscopy analysis shows a 1.3 e V chemical shift change.Compared with pristine MoS₂films,the Raman spectra of RE doped MoS₂ films has a 1 cm^-1 Raman shift changes,and their photoluminescence intensity has significant increase,reaching a maximum of 10 times.In conclusion,the rare earth atoms have been successfully entered into the monolayer MoS₂.In addition,it is found that the intensity of the transient absorption spectrum was slightly increased,the lifetime was significantly changed.It may be concluded that the lattice shrinkage caused by doping rare earth enhanced the crystal quality of MoS₂film,thus improving its luminous efficiency.This work greatly improves the photoluminescence performance of MoS₂ film by rare earth doping,which is of great significance to the further study of optical and electronic devices of MoS₂ film.