Determination of Formation and Ionization Energies of Charged Defects in Two-Dimensional Materials

Wang, Dan; Han, Dong; Li, Xianbin; Xie, Songhai; Chen, Nian‐Ke; Wang, Tian; West, Damien; Zhang, S. B.

doi:10.1103/physrevlett.114.196801

Cited by 103 publications

(86 citation statements)

References 43 publications

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“…5. In agreement with recent DFT studies 8, 11, 12, 16 , these results demonstrate that the task of calculating the formation energy of a charged defect in a low-dimensional material cannot be accomplished by using only DFT. A numerical scheme needs to be used to estimate Δ E L = E ∞ − E L , which in the case of a singly negatively charged S vacancy in monolayer MoS 2 amounts to about 10% of the energy value obtained by DFT (Table 2).…”

Section: Resultssupporting

confidence: 90%

“…In Eq. (1), Δ E L is equal to E ∞ − E L 1, 3, 6, 8, 9 , that is the difference in electrostatic energy between the isolated defect in the infinite material system, E ∞ , and the periodic array of defected supercells of linear dimension L compensated by a uniform charge background, E L . Here, we present a new and original method to calculate Δ E L = E ∞ − E L .…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, various corrective schemes have been put forward to go beyond the Makov and Payne scheme and calculate Δ E L in a general situation 7, 8, 10–12 , such as for a charged defect of finite size 3 in an anisotropic 9 , inhomogeneous 6 , or aperiodic system 6 . All these previous corrective schemes rely on continuum electrostatics, structureless jellium-like models for a defected dielectric system, and either analytical 3 or numerical 6 solutions of the Poisson equation.…”

Section: Introductionmentioning

confidence: 99%

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Atomistic Corrective Scheme for Supercell Density Functional Theory Calculations of Charged Defects

Cao

Bongiorno

2017

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A new method to correct formation energies of charged defects obtained by supercell density-functional calculations is presented and applied to bulk, surface, and low-dimensional systems. The method relies on atomistic models and a polarizable force field to describe a material system and its dielectric properties. The polarizable force field is based on a minimal set of fitting parameters, it accounts for the dielectric screening arising from ions and electrons separately, and it can be easily implemented in any software for atomistic molecular dynamics simulations. This work illustrates both technical aspects and applications of the new corrective scheme. The method is tested on systems in vacuo to validate the energy scheme. It is applied to charged defects in the bulk and at the surface of realistic materials to achieve comparison with published results obtained by using available corrective schemes based on continuum electrostatics treatments. Moreover, to demonstrate its generality, the method is used to correct the formation energy obtained by DFT of a singly negatively charged S vacancy in monolayer, bilayer, trilayer and bulk MoS2.

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Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Atomistic Corrective Scheme for Supercell Density Functional Theory Calculations of Charged Defects

Cao

Bongiorno

2017

Sci Rep

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“…The exchange correlation energy was described by the generalized gradient approximation, in the scheme proposed by Perdew, Burke and Ernzerhof (PBE) (refs 52, 53). A unit cell with vacuum region of 16 Å was used for the calculation, and a 9 × 9 × 1 Monkhorst-Pack mesh grid was used to sample the Brillouin zone.…”

Section: Methodsmentioning

confidence: 99%

Slow cooling and efficient extraction of C-exciton hot carriers in MoS2 monolayer

et al. 2017

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In emerging optoelectronic applications, such as water photolysis, exciton fission and novel photovoltaics involving low-dimensional nanomaterials, hot-carrier relaxation and extraction mechanisms play an indispensable and intriguing role in their photo-electron conversion processes. Two-dimensional transition metal dichalcogenides have attracted much attention in above fields recently; however, insight into the relaxation mechanism of hot electron-hole pairs in the band nesting region denoted as C-excitons, remains elusive. Using MoS2 monolayers as a model two-dimensional transition metal dichalcogenide system, here we report a slower hot-carrier cooling for C-excitons, in comparison with band-edge excitons. We deduce that this effect arises from the favourable band alignment and transient excited-state Coulomb environment, rather than solely on quantum confinement in two-dimension systems. We identify the screening-sensitive bandgap renormalization for MoS2 monolayer/graphene heterostructures, and confirm the initial hot-carrier extraction for the C-exciton state with an unprecedented efficiency of 80%, accompanied by a twofold reduction in the exciton binding energy.

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“…Specifically, when the jellium model is used, a virtual charge is uniformly filled in the whole supercell, including the vacuum region. This leads to a divergent Coulomb interaction between the jellium charge and the charge left on the 2D slab 17 . In this case, the jellium model also becomes unphysical because the jellium is very different from the real charge distribution when electrons are excited to the band edge states with their charge distribution confined within or near the 2D slab ( Fig.1c).…”

Section: Introductionmentioning

confidence: 99%

Realistic dimension-independent approach for charged-defect calculations in semiconductors

et al. 2020

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First-principles calculations of charged defects have become a cornerstone of research in semiconductors and insulators by providing insights into their fundamental physical properties.But current standard approach using the so-called "jellium model" has encountered both conceptual ambiguity and computational difficulty, especially for low-dimensional semiconducting materials. In this Communication, we propose a physical, straightforward, and dimension-independent universal model to calculate the formation energies of charged defects in both three-dimensional (3D) bulk and low-dimensional semiconductors. Within this model, the ionized electrons or holes are placed on the realistic host band-edge states instead of the virtual jellium state, therefore, rendering it not only naturally keeps the supercell charge neutral, but also has clear physical meaning. This realistic model reproduces the same accuracy as the traditional jellium model for most of the 3D semiconducting materials, and 2 remarkably, for the low-dimensional structures, it is able to cure the divergence caused by the artificial long-range electrostatic energy introduced in the jellium model, and hence gives meaningful formation energies of defects in charged state and transition energy levels of the corresponding defects. Our realistic method, therefore, will have significant impact for the study of defect physics in all low-dimensional systems including quantum dots, nanowires, surfaces, interfaces, and 2D materials.

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Determination of Formation and Ionization Energies of Charged Defects in Two-Dimensional Materials

Cited by 103 publications

References 43 publications

Atomistic Corrective Scheme for Supercell Density Functional Theory Calculations of Charged Defects

Atomistic Corrective Scheme for Supercell Density Functional Theory Calculations of Charged Defects

Slow cooling and efficient extraction of C-exciton hot carriers in MoS2 monolayer

Realistic dimension-independent approach for charged-defect calculations in semiconductors

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