Fig. 3: Optical characteristics of the Nb-induced single photon emitters.
From: Nb impurity-bound excitons as quantum emitters in monolayer WS2
a Time evolution of PL spectra highlighting the region of \({{\rm{NbX}}}_{{\rm{L}}}\) as well as free trions and neutral exciton peaks over 60 s. b Power dependence of the integrated PL signal. Error bars represent standard deviation of the fitted curves. \({P}_{{\rm{sat}}}\) denotes the saturating laser power of \({{\rm{NbX}}}_{{\rm{L}}}\). c Time-resolved PL data fitted to a triexponential function, revealing three distinct lifetime components: \({\tau }_{1}\), \({\tau }_{2}\), and \({\tau }_{3}\).The long component (light grey curve) corresponds to the broad background (BG) feature in the bottom panel of 2b (i.e., the grey area underneath the sharp Nb peak). The sharp Nb peak represents the single photon emitter (SPE). The instrumental response function (IRF) of ~0.2 ns is also shown. The time difference \(\,{\tau }_{0}\) between the rise time of the IRF and the emitter is indicated. d Second-order photon correlation of the two faster-decaying components marked with light and dark orange lines in (c). Intensity correlation shows antibunching with 0.27 ± 0.22 at zero delay. Uncertainty is obtained from the standard deviation of 390 peaks for t ≠ 0. A 532 nm CW laser is used in (a, b), whilst a pulsed laser tuned to the A-exciton resonance is used in (c, d). All measurements were conducted at 4 K.
