Large Spin-Orbit Splitting of Deep In-Gap Defect States of Engineered Sulfur Vacancies in Monolayer WS2

Abstract

Structural defects in 2D materials offer an effective way to engineer new material functionalities beyond conventional doping. Here, we report the direct experimental correlation of the atomic and electronic structure of a sulfur vacancy in monolayer WS 2 by a combination of CO-tip noncontact atomic force microscopy and scanning tunneling microscopy. Sulfur vacancies, which are absent in as-grown samples, were deliberately created by annealing in vacuum. Two energetically narrow unoccupied defect states followed by vibronic sidebands provide a unique fingerprint of this defect.Direct imaging of the defect orbitals reveals that the large splitting of 252 ± 4 meV between these defect states is induced by spin-orbit coupling.

Exciton diffusion in monolayer semiconductors with suppressed disorder

“…As a limiting case, we can assume that the non-radiative recombination is provided by a finite trap density that is of the same order of magnitude in asexfoliated and encapsulated samples. This proposition could be reasonable considering that many of the trap states are likely to already reside within the material itself , 66 at least in the studied WS 2 samples, and are not necessarily associated with the choice of the substrate. Only moderate increase of the exciton lifetime from about 0.5...0.7 ns in SiO 2 -supported samples to 0.8...1 ns in freestanding flakes 21 are consistent with this assumption.…”

Electron and hole transport in disordered monolayer MoS2 : Atomic vacancy induced short-range and Coulomb disorder scattering

“…In experimental STM studies on monolayer TMDs, atomic monovacancies have been found to be among the dominating sources of intrinsic lattice disorder [43][44][45][46][47][48]. Their stability and electronic structure have been studied in great detail theoretically [49][50][51][52][53][54][55][56][57], demonstrating that they often introduce in-gap states, as illustrated in Fig.…”

Electrically driven photon emission from individual atomic defects in monolayer WS 2

“…The as-grown sample contains several substitutional atomic defects, such as chromium (Cr W ) and molybdenum (Mo W ) replacing tungsten, as well as oxygen substituting sulfur (O S ) ( 19 , 35 ). Then, we selectively generate Vac S in both the top and bottom sulfur layers by high-temperature annealing in vacuum ( 36 ). Both Cr W and Vac S defects exhibit unoccupied electronic states placed a few hundred millielectronvolts below the WS 2 conduction band edge ( Fig.…”