Electrons on the surface of 2D materials: from layered electrides to 2D electrenes

Druffel, Daniel L.; Woomer, Adam H.; Kuntz, Kaci L.; Pawlik, Jacob T.; Warren, Scott C.

doi:10.1039/c7tc02488f

Cited by 60 publications

(59 citation statements)

References 107 publications

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“…Usually, researchers arbitrarily alter the elemental combinations of typical electrides but retain their crystal symmetry to extend for the new electrides, e.g., ABtype, A 2 B-type, and A 3 B-type (A = alkaline or rare earth elements, B = IV, V, VI, and VII elements) electrides. [24][25][26][27] Besides, many electrides (e.g., Li, 28 Na, 29 Mg, 30 C 31 , Na 2 He, 32 and Sr 5 P 3 33 ) have been found to reveal a generalized structure under pressure. 34 Depending on the dimensionality of the anionic electrons localizations, electrides can be classified into 0D, 1D, and 2D systems, 13,20,35,36 where the anionic electrons are either isolated or bonded with each other in the cage-like, channel-like, or layer-like voids.…”

Section: Introductionmentioning

confidence: 99%

Identifying quasi-2D and 1D electrides in yttrium and scandium chlorides via geometrical identification

Wan

Xiao

et al. 2018

npj Comput Mater

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Developing and understanding electron-rich electrides offers a promising opportunity for a variety of electronic and catalytic applications. Using a geometrical identification strategy, here we identify a new class of electride material, yttrium/scandium chlorides Y(Sc) x Cl y (y:x < 2). Anionic electrons are found in the metal octahedral framework topology. The diverse electronic dimensionality of these electrides is quantified explicitly by quasi-two-dimensional (2D) electrides for [YCl] + •e − and [ScCl] + •e − and one-dimensional (1D) electrides for [Y 2 Cl 3 ] + •e − , [Sc 7 Cl 10 ] + •e − , and [Sc 5 Cl 8 ] 2+ •2e − with divalent metal elements (Sc 2+ : 3d 1 and Y 2+ : 4d 1 ). The localized anionic electrons were confined within the inner-layer spaces, rather than inter-layer spaces that are observed in A 2 B-type 2D electrides, e.g. Ca 2 N. Moreover, when hydrogen atoms are introduced into the host structures to form YClH and Y 2 Cl 3 H, the generated phases transform to conventional ionic compounds but exhibited a surprising reduction of work function, arising from the increased Fermi level energy, contrary to the conventional electrides reported so far. Y 2 Cl 3 was experimentally confirmed to be a semiconductor with a band gap of 1.14 eV. These results may help to promote the rational design and discovery of new electride materials for further technological applications.npj Computational Materials (2018) 4:77 ; https://doi.

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Section: Introductionmentioning

confidence: 99%

Identifying quasi-2D and 1D electrides in yttrium and scandium chlorides via geometrical identification

Wan

Xiao

et al. 2018

npj Comput Mater

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“…Finally, it was shown that Ca 2 N can be exfoliated into two-dimensional (2D) nanosheets by liquid exfoliation, while preserving anionic electrons on its surface [16,17]. Nowadays, 2D electrides, or electrenes, is a special topic of research fusing the concepts of electride chemistry and 2D materials [18].In this regards, 2D materials are of extreme interest featuring various exceptional properties and applications [19,20]. Of particular importance is intrinsic magnetism in atomically thin systems, where over the years various prototype examples have been reported to exhibit magnetic properties [21][22][23][24][25].…”

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confidence: 99%

Localised magnetism in 2D electrides

Badrtdinov

Nikolaev

2020

J. Mater. Chem. C

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In this work, we investigate intrinsic magnetic properties of monolayer electrides LaBr2 and La2Br5, where excess electrons do not reside at any atomic orbital and act as anions located at interstitial regions. Having demonstrated that conventional first-principles approaches are incapable of treating such non-atomic magnetic orbitals largely underestimating insulating band gaps, we construct effective electronic models in the basis of Wannier functions associated with the anionic states to unveil the microscopic mechanism underlying magnetism in these systems. Being confined at zero-dimensional cavities in the crystal structure, the anionic electrons will be shown to reveal an exotic duality of strong localisation like in d-and f -electron systems and large spatial extension inherent to delocalised atomic orbitals. While the former tends to stabilise a Mott-insulating state with localised magnetic moments, the latter results in direct exchange between neighbouring anionic electrons that dominates over antiferromagnetic superexchange interactions. On the basis of the derived spin models, we argue that any long-range magnetic order is prohibited in LaBr2 by Mermin-Wagner theorem, while intersite anisotropy in La2Br5 stabilises weakly coupled ferromagnetic chains along the monoclinic b axis. Our study shows that electride materials combining peculiar features of both localised and delocalised atomic states constitute a unique class of strongly correlated materials.Introduction. Electrides are a unique class of ionic materials, where the electron density is neither localised at any atomic orbital, nor fully delocalised like in metals. Instead, their electrons occupy interstitial regions formed by cavities in the crystal structure, where they act as anions [1, 2]. Materials with anionic electrons offer versatile functionalities, such as high electrical conductivity [3], ultra-low work functions [4], and non-linear optical responses [5], ranging their applications as electron emitters [6], battery anodes [7], and agent catalysts [8].Their physical properties are in large part determined by topology of the voids confining anionic electrons. In 2003, Matsuishi et al [9] demonstrated the first inorganic material [Ca 24 Al 28 O 64 ] +4 ·4e − stable at room temperature, which shows the high density of anionic electrons trapped in the crystallographic cages, forming a quasizero-dimensional electride with high electronic conductivity due to tunnelling through the cages [10, 11]. Recently, a novel layered electride [Ca 2 N] + ·e − has been reported, where owing to a highly delocalised nature the quasi-two-dimensional anionic electrons confined in the interlayer regions display an extreme electron mobility and long mean scattering time [12, 13]. Later on, strong localisation of anionic electrons has been observed in a layered transition-metal hypocarbide [Y 2 C] 2+ ·2e − with the quasi-two-dimensional anionic electrons in the interlayer spaces [14, 15]. Finally, it was shown that Ca 2 N can be exfoliated into two-dimensional...

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“…Two-dimensional (2D) layered materials have displayed a new stage ever since graphene was successfully fabricated in 2004 [ 1 ]. Recently, more and more 2D materials have been synthesized and investigated [ 2 ]. These include layered transition metal dichalcogenides (TMDs)

(A = Mo, W, and Re and B = S and Se) and layered group III-VI semiconductors such as GaS and GaSe.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Sensitivity of CO on Two-Dimensional, Strained, and Defective GaSe

2021

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The toxic gas carbon monoxide (CO) is fatal to human beings and it is hard to detect because of its colorless and odorless properties. Fortunately, the high surface-to-volume ratio of the gas makes two-dimensional (2D) materials good candidates for gas sensing. This article investigates CO sensing efficiency with a two-dimensional monolayer of gallium selenide (GaSe) via the vacancy defect and strain effect. According to the computational results, defective GaSe structures with a Se vacancy have a better performance in CO sensing than pristine ones. Moreover, the adsorption energy gradually increases with the scale of tensile strain in defective structures. The largest adsorption energy reached −1.5 eV and the largest charger transfer was about −0.77 e. Additionally, the CO gas molecule was deeply dragged into the GaSe surface. We conclude that the vacancy defect and strain effect transfer GaSe to a relatively unstable state and, therefore, enhance CO sensitivity. The adsorption rate can be controlled by adjusting the strain scale. This significant discovery makes the monolayer form of GaSe a promising candidate in CO sensing. Furthermore, it reveals the possibility of the application of CO adsorption, transportation, and releasement.

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Electrons on the surface of 2D materials: from layered electrides to 2D electrenes

Abstract: We review layered and ultrathin electrides with exciting properties like high electrical mobility, high carrier concentrations, and low work functions.

Cited by 60 publications

References 107 publications

Identifying quasi-2D and 1D electrides in yttrium and scandium chlorides via geometrical identification

Identifying quasi-2D and 1D electrides in yttrium and scandium chlorides via geometrical identification

Localised magnetism in 2D electrides

Enhanced Sensitivity of CO on Two-Dimensional, Strained, and Defective GaSe

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