Fabrication And Luminescence Of Lanthanide-doped Two-dimensional Transition Metal Chalcogenides

Two-dimensional transition metal chalcogenides(2D-TMDs),possessing atomic thickness and adjustable bandgap,are a class of excellent luminescent materials,glittering for the construction of optoelectronic devices due to their unique physical properties.Doping can effectively regulate the physicochemical properties of 2D-TMDs,which is momentous for their application.Lanthanide-doping can reform the band of TMDs to endow new photoelectric nature.So far,a handful of lanthanides have been doped into 2D-TMDs via dry-method synthesis.The implementation of doping and co-doping of lanthanides to monolayer TMDs materials aided with molecular uniformly liquid precursors and dopants,as well as the study of their luminescent properties,are of pith and moment for the development of 2D luminescent materials.A series of trivalent lanthanide(Ln³⁺)doped monolayer MoS₂was fabricated by two-step thermal annealing of a new liquid precursor Na₂MoS₄ and trivalent lanthanide chloride as dopants.The photoluminescence spectra of doped MoS₂ at 300K and 77K suggests the doping of Ln³⁺leading to blue-shifting and higher intensity of A exciton,whose variations show a tetrad effect with the atomic number climbing.It suggests the f-d orbital interactions in Ln³⁺-doped MoS₂are bound up with the f orbital configuration.A liquid precursor-assisted CVD method was also proposed,in which ammonium heptamolybdate emulsion acted as the precursor and the mix of lanthanide chlorides and ammonium tetramolybdate as dopants to achieve different proportions of Er/Yb and Er/Ho co-doping in monolayer MoS₂.The implantation of Ln³⁺into the lattice was determined by various characterizations.Interestingly,the doping of Er/Yb and Er/Ho made the Raman and PL peak of MoS₂ swing with the wave of the ratio of Ln³⁺,and the possible reasons were discussed.The multi-band up-conversion emitting of co-doped MoS₂ was detected,and the corresponding mechanisms were explained.The luminescence of monolayer MoS₂was effectively tuned by co-doping of Ln³⁺.In this thesis,the doping of trivalent lanthanide ions in 2D-MoS₂was fabricated by diverse raw material systems,and their luminescence behaviors were studied,which renders a laboratory basis for the application of lanthanides in optical semiconductors.