Defect Activated Photoluminescence in WSe₂ Monolayer

Abstract

Defects in transition metal dichalcogenides (TMDs) play an important role in tailoring electrical and optical properties.Here we employ Ar + plasma to controllably generate active defects in WSe 2 monolayers to tune their optical properties. Two defect-activated PL emission peaks are emerging in the low temperature PL spectra of WSe 2 monolayer treated with Ar + plasma. These emissions are attributed to the recombination of excitons bound to different types of structural defects. The shallow level emission originates from the recombination of excitons at chalcogen vacancies, while the deep level emission might arise from other types of defects, such as transition metal vacancies, cluster of vacancies, rotational defects, or antisite defects. Our results demonstrate that Ar + plasma treatment is an effective approach to induce desirable defects in TMDs monolayers and PL spectroscopy is an efficient method to investigate these defects.

Emerging photoluminescence from defective vanadium diselenide nanosheets

“…Keeping the sub-band-gap energy of light emission, it can be hypothesized that the band-to-band transition is mediated with some localized energy states inside the material band gap. These states are mainly raised from surface and bulk defect states and imperfections such as grain boundaries [23,25,[41][42][43][44][45][46]. To evaluate the stability of the emission under continuous light irradiation, the dispersed solution of VSe 2 NSs has been placed inside a quartz cuvette and exposed to UV irradiation (8 W, UVLMS-38 EL, 302 nm) from a distance of c.a ∼1 cm for about 4 h. As it can be clearly seen from Fig.…”

“…The conversion from an indirect to a direct band-gap semiconductor is one of these prominent differences between the bulk and monolayer TMDs. This phenomenon is due to quantum confinement effects and has been found in different types of TMDs such as MoS 2 [21,22], WS 2 [23], WSe 2 [24,25], and MoTe 2 [26][27][28]. This conversion makes 2D TMDs an excellent choice for LED applications in the visible (Vis) and near infrared (NIR) spectral regimes.…”

“…Chemical treatments [29][30][31], alloying [32][33][34][35], coupling with surface plasmon polaritons [36,37], integration with photonic crystal cavities [38,39], and strain engineering [40] are some of these proposed methodologies to improve the band-to-band PL characteristics of 2D TMDs. Moreover, it is found that a strong sub-band-gap PL can be originated from defect-mediated transitions [23,25,[41][42][43][44][45][46] that are of great interest in the design of NIR LEDs.…”

Modelling the UV spectrum of SDSS-III/BOSS galaxies: hints towards the detection of the UV upturn at high-z

“…The M09 empirically-based models use the index description as a function of stellar parameters as measured on the real IUE stellar spectra collected by F92. The data consists of low-resolution (6Å) observations of 218 stars in the solar neighbourhood, covering 1150 -3200Å and are compiled in the "IUE Ultraviolet spectral atlas" (Wu et al (1983(Wu et al ( , 1991). The library consists of 56 stellar groups, classified by spectral type and luminosity class.…”

Microsecond Valley Lifetime of Defect-Bound Excitons in Monolayer WSe2

“…1(c), suggests that this emission arises from defect-bound excitons localized near the selenium vacancy sites [31,32]. Similar changes to the optical response occur after electronbeam lithography, alpha-particle irradiation, and argon plasma treatment of TMDs [33][34][35][36]; however, the recombination dynamics and spin-valley coupling of engineered defects in TMDs have not been investigated, which is the focus of this Letter.…”