Functionalization of two-dimensional tungsten diselenide and MXene for tunable optical property
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Since the discover of graphene in 2004, two-dimensional (2D) materials have gained tremendous attention because of their distinctive properties relative to their bulk form. Particularly, transition metal dichalcogenides (TMDs) and 2D transition metal carbides and nitrides (MXenes) have shown promising applications in flexible electrical and optoelectronic devices. Due to the atomically thin nature, the electronic band structures of these materials are very sensitive to the small changes in the lattice and the surface functionalization, offering a dimension to tune the properties of the materials. In this thesis, approaches to functionalize monolayer WSe2 and MXene were explored. The as-grown chemical vapor deposition (CVD) monolayer WSe2 flakes were treated by plasma assisted doping method. Specifically, Methane plasma was used as carbon dopant source to introduce p-type lattice doping into monolayer WSe2. In addition, chemical reactions between perfluorophenylazides (PFPA) organic molecules and WSe2 flakes were conducted where the PFPA molecules may covalently bonded to the WSe2 surface. Similarly, the PFPA functionalization was applied to MXene, an emerging 2D material with high conductivity. Shifts and intensity change were observed in Raman spectra after the functionalization, indicating structural and electric structure changes might be introduced. Further characterizations of the structures and electric properties will be taken in the near future.