Fig. 3: Characterization of defects and defect-bound excitons in WSe2.
From: Intrinsic donor-bound excitons in ultraclean monolayer semiconductors
a–c Scanning Tunneling Microscopy (STM) topographic images of 50 x 50 nm2 area of WSe2 with different growth parameters (F1, F2, and F3). Scale bar is 10nm. Imaging conditions for the STM topographic images were a tunneling bias of 1.4 V and current of 400 pA for F1 and a tunneling bias of 1.4 V and current of 150 pA for F2 and F3. The WSe2 crystals were cleaved in ultra-high vacuum STM chamber (base pressure <2.0 × 10−10 torr) to obtain a clean surface before imaging. White and black dashed circles highlight the donor and acceptor defects, respectively. See Supplementary Fig. 6 details. d–f Photoluminescence (PL) color maps as a function of the back-gate bias for d, F1, e, F2, and f, F3. The white dashed boxes in the PL color maps indicate the energy and the back-gate bias ranges for defect-bound excitons. For the PL color map, the samples were excited using a continuous-wave (CW) laser with an excitation wavelength of 532 nm with a fluence of 650 W/cm2 (10 μW) at 4 K.
