Preparation And Optical Properties Of Two-dimensional SnSe₂/SnS_2-xSe_x Nanomaterials

Since the discovery of graphene in 2004,The research of two-dimensional materials has become a hot topic.Among them,tin selenide(SnSe2)has attracted many scientists’ interest for its unique properties,and has been widely discussed and studied.However,there are few reports about its doping product SnS2-xSex.This is because there are great challenges in the preparation of high-quality and ultra-thin SnS2-xSex films.Meanwhile,there are few reports on the XRD and Raman spectra of SnS2-xSex materials with different doping levels.In order to solve these problems,SnSe2 was prepared by chemical vapor deposition(CVD)on SiO2/Si substrates,SnS2-xSex was prepared on mica substrate,and its appearance and structure were characterized by OM and XRD.At the same time,their optical properties of SnSe2 with different thickness were studied by Raman spectra,we found that the certain relationship between the thickness and the shift of Raman peak.We also analyzed doping concentration of SnS2-xSex materials by XRD and Raman spectra.Then we calculated the band gap width of SnS2-xSex materials by UV-Vis absorption spectrum and photoluminescence spectrum,which indicated that doping of S can change the optical band gap of SnS2-xSex.The main conclusion is as follows:(1)A large area of SnSe2 was prepared by the CVD.The appearance,structure and crystal quality of the products were characterized.The XRD shows that the products are high quality single crystal.The Raman spectra shows that the SnSe2 is 1T phase crystal.We also found the thickness of the SnSe2 is related with the position and intensity of the Raman peak.(2)A large area of SnS2-xSex material was prepared by the improved CVD method,and its appearance and structure were characterized.By analyzing the XRD and Raman spectra of SnS2-xSex,we can roughly guess the doping concentration of the products.By the UV-Vis absorption spectrum and photoluminescence spectrum of SnS2-xSex material,we found that doping can change the band gap of the products,which provide a way for the fabrications of optical devices with different optical band gap.We used CVD method to prepare SnSe2 and SnS2-xSex,which were characterized by its Raman spectrum and XRD spectrum.We fabricated SnS2-xSex material by changed the S:Se ratio of the precursor,and the band gap of the products could be adjusted.We provided a way for the preparation of two-dimensional materials with different band gap.