Fig. 3: Charge transfer mechanism of monolayer WSe2 doped with chloroform.
From: Low resistance p-type contacts to monolayer WSe2 through chlorinated solvent doping
a Photoluminescence (PL) spectra of an undoped monolayer WSe2 sample at different temperatures (6.7 to 296 K). b PL spectra of chloroform-doped monolayer WSe2 sample from 6.7 to 296 K. Representative Gaussian-Lorentzian blend curve fits are shown for the 6.7 K spectra in panels (a, b), corresponding to the neutral exciton (X), trion (T), and L1-L3 peaks (described further in the text). c Density functional theory (DFT) simulated isosurfaces of monolayer WSe2 with adsorbed chloroform in Cl-facing (top) and H-facing (bottom) configurations, as well as the calculated adsorption energies (Eads). The value of the Bader charge transfer efficiency is shown for each chloroform orientation, corresponding to the charge transfer of one chloroform molecule. d Potential energy vs. distance for an adsorbed chloroform to monolayer WSe2 in Cl-facing and H-facing orientations. The adsorption energy ranges from 300–500 meV and the equilibrium distance from 2–4 Å, consistent with strong physisorption. Inset: zoomed-out view of the potential energy vs. distance. e Projected density of states (pDOS) contributions from monolayer WSe2 and chloroform to the overall DOS in the Cl-facing orientation. The valence band maximum EV and conduction band minimum EC are marked with dashed pink lines. Noticeably, no chloroform states are formed in the WSe2 band gap. The inset shows a zoomed-in view of the PDOS contributions around the WSe2 band gap.
