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- Bretscher, Hope, et al.
(författare)
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Rational Passivation of Sulfur Vacancy Defects in Two-Dimensional Transition Metal Dichalcogenides
- 2021
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:5, s. 8780-8789
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Tidskriftsartikel (refereegranskat)abstract
- Structural defects vary the optoelectronic properties of monolayer transition metal dichalcogenides, leading to concerted efforts to control defect type and density via materials growth or postgrowth passivation. Here, we explore a simple chemical treatment that allows on-off switching of low-lying, defect-localized exciton states, leading to tunable emission properties. Using steady-state and ultrafast optical spectroscopy, supported by ab initio calculations, we show that passivation of sulfur vacancy defects, which act as exciton traps in monolayer MoS2 and WS2, allows for controllable and improved mobilities and an increase in photoluminescence up to 275-fold, more than twice the value achieved by other chemical treatments. Our findings suggest a route for simple and rational defect engineering strategies for tunable and switchable electronic and excitonic properties through passivation.
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| 2. |
- Shukla, Vivekanand, 1988, et al.
(författare)
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Accurate Nonempirical Range-Separated Hybrid van der Waals Density Functional for Complex Molecular Problems, Solids, and Surfaces
- 2022
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Ingår i: Physical Review X. - 2160-3308. ; 12:4
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a new, general-purpose, range-separated hybrid van der Waals density functional termed vdW-DF2-ahbr within the nonempirical vdW-DF method [Hyldgaard, et al. J. Phys. Condens. Matter 32, 393001 (2020)]. It combines a correlation from vdW-DF2 with a screened Fock exchange that is fixed by a new model of exchange effects in the density-explicit vdW-DF-b86r or rev-vdW-DF2 functional [Hamada, Phys. Rev. B 89, 121103(R) (2014)]. The new vdW-DF2-ahbr prevents spurious exchange binding and has a small-density-gradient form set from many-body perturbation analysis. It is accurate for bulk as well as layered materials, and it systematically and significantly improves the performance of the present vdW-DFs for molecular problems. Importantly, vdW-DF2-ahbr also outperforms present-standard (dispersion-corrected) range-separated hybrids on a broad collection of noncovalent-interaction benchmark sets, while at the same time successfully mitigating the density-driven errors that often affect the description of molecular transition states and isomerization calculations. vdW-DF2-ahbr furthermore improves on state-of-the-art density-functional-theory approaches by succeeding at challenging problems. For example, it (1) correctly predicts both the substrate structure and the site preference for CO adsorption on Pt(111), (2) it outperforms existing nonempirical vdW-DFs for the description of CO2 adsorption in both a functionalized and in a simple metal-organic framework, and (3) it is highly accurate for the set of base-pair interactions in a model of DNA assembly.
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