Improving luminescence properties of WSe2 monolayers via vanadium incorporation during CVD growth

Monolayer Tungsten diselenide (WSe2) is a direct band gap semiconductor that has good luminescence properties which are of great interest for optoelectronics applications, especially in optical communications due to its bandgap falling within the fiber optic transmission windows (similar to 1.6 eV). In this study, we investigated the effect of vanadium (V) incorporation in WSe2 monolayers grown by chemical vapor deposition (CVD). Our results show that lightly V-doped WSe2 exhibits increased photoluminescence (PL) intensity as compared to pristine WSe2 and strongly quenched PL signal for highly doped samples. Resonance Raman spectroscopy measurements were performed to study the disorder effects due to the presence of V in the vibrational spectra. It was possible to observe the activation of the defect-related LA(M) mode and the evolution of the 2LA(M) and A(M) modes as a function of V concentration. X-ray photoelectron spectroscopy (XPS) and high-resolution scanning transmission electron microscopy (STEM) measurements were performed to investigate de presence of V in the samples.