Fig. 5: Determination of chloroform location in a WSe2/oxide stack.
From: Low resistance p-type contacts to monolayer WSe2 through chlorinated solvent doping
a Atomic-force microscopy (AFM) of an exfoliated WSe2 flake with various layer thicknesses. L denotes the number of WSe2 layers. b Height distribution of the exfoliated flake before (gray) and after (green) doping, in the 2–4L region (as marked in panel (a). The peaks mark the height of the SiO2, 2L, 3L, and 4L WSe2 regions. There is no noticeable change in spacing between WSe2 layers, but the difference between SiO2 and 2L WSe2 increases. Inset: schematic of chloroform inserting at the SiO2/WSe2 interface, causing an increase in height of the WSe2 layer relative to SiO2. Triangles denote the height of the 2L, 3L, and 4L WSe2 regions, matching the peaks in the height distribution. c Scanning electron microscope (SEM) image of the exfoliated WSe2 flake as seen in panel (a). d–f Elemental mapping by Auger electron spectroscopy (AES) of a doped WSe2 flake of Se, Si, and Cl, respectively. The brighter pixels correspond to regions with higher elemental content. g Line scan of elemental Se, Si, and Cl content extracted from panel (d), showing an increase in Cl signal in the 2L WSe2 region.
