Stable single-layers of calcium halides (CaX<sub>2</sub>, X = F, Cl, Br, I)

Başkurt, Mehmet; Yagmurcukardes, M.; Peeters, F. M.; Şahin, Hasan

doi:10.1063/5.0006011

Cited by 15 publications

(6 citation statements)

References 71 publications

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“…For CaX 2 :Tm (X = Cl, Br, I) no direct values for the phonon energies ω max coupling to Tm 2+ are reported in literature. We have therefore decided to estimate these values based on known studies that involve such hosts, see table 1 [9][10][11]. The values are close to those reported for LaY 3 (Y = Cl, Br) [24].…”

Section: Model Settingsupporting

confidence: 53%

Experimental and numerical analysis of Tm²⁺ excited-states dynamics and luminescence in CaX ₂ (X = Cl, Br, I)

Plokker

Knijff

Wit

et al. 2021

J. Phys.: Condens. Matter

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The prospect of using Tm 2+ -doped halides for luminescence solar concentrators (LSCs) requires a thorough understanding of the temperature dependent Tm 2+ excited states dynamics that determines the internal quantum efficiency (QE) and thereby the efficiency of the LSC. In this study we investigated the dynamics in CaX 2 :Tm 2+ (X = Cl, Br, I) by temperature-and time-resolved measurements. At 20 K up to four distinct Tm 2+ emissions can be observed. Most of these emissions undergo quenching via multi-phonon relaxation below 100 K. At higher temperatures, only the lowest energy 5d-4f emission and the 4f-4f emission remain. Fitting a numerical rate equation model to the data shows that the subsequent quenching of the 5d-4f emission is likely to occur initially via multi-phonon relaxation, whereas at higher temperatures additional quenching via interband crossing becomes thermally activated. At room temperature only the 4f-4f emission remains and the related QE becomes close to 30%. Possible reasons for the quantum efficiency not reaching 100% are provided.

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Section: Model Settingsupporting

confidence: 53%

Experimental and numerical analysis of Tm²⁺ excited-states dynamics and luminescence in CaX ₂ (X = Cl, Br, I)

Plokker

Knijff

Wit

et al. 2021

J. Phys.: Condens. Matter

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“…Our results show that the 1T phase is energetically more favorable compared to the 1H phase of Janus CaFBr monolayer, which is in agreement with the previous calculations for 1T and 1H phases of CaF 2 and CaBr 2 monolayers. [ 52 ] . Figure 2 a,b presents the calculated band structure phonons spectra along the high symmetric k‐points in the Brillouin zone and corresponding phonon density of states for the 1T and 2H phases of CaFBr, respectively.…”

Section: Resultsmentioning

confidence: 99%

Strain Engineering of the Electronic and Optical Properties of Predicted Janus CaFBr Monolayer for Potential Use in Optoelectronic Devices: A Density Functional Theory Study

Marjaoui

Tamerd

Abdellaoui³

et al. 2023

Physica Status Solidi (b)

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Herein, the biaxial strain effect is investigated on the structural, electronic, and optical properties of 1T and 1H phases of Janus CaFBr monolayer in the framework of density functional theory. It is found that both phases of the Janus CaFBr monolayer are direct semiconductors at equilibrium, with bandgaps of 3.90 and 3.55 eV for 1T and 1H phases, respectively. The thermodynamic stability is examined via cohesive energy and phonon dispersion. The bandgap decreases linearly and is nearly parabolic for 1T and 1H phases, respectively, when switching from the tensile to compressive strain with a drastic shift from direct to indirect bandgap at −10% of compressive strains. The calculated dielectric function and optical properties such as reflectivity, refractive index, extinction, and absorption coefficients enhance under biaxial with an improvement of the absorption coefficient especially in the visible and ultraviolet (UV) regions for 1H and 1T phases, respectively, which is in line with the dielectric constant. The results suggest that the Janus CaFBr monolayer might be a potential candidate for optoelectronic applications in visible/UV detection and absorption.

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“…Following the discovery of graphene and other 2D materials, several groups have investigated the monolayer counterpart of some alkaline earth halides. For instance, stable single-layer of calcium halides have been predicted by Baskurt et al [31]. All the monolayers are dynamically stable, exhibiting insulator nature with band gap ranging from 4.38 to 9.49eV.…”

Section: Introductionmentioning

confidence: 95%

Inducing d ⁰ magnetism in new SrCl₂ monolayer towards spintronic applications

On,

Ponce-Pérez,

et al. 2024

Phys. Scr.

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Magnetism engineering in two-dimensional (2D) materials has been widely explored to make new spintronic materials. In this work, the doping (with alkali metals at Sr sublattice and with chalcogen atoms at Cl sublattice) method are proposed to induce signiﬁcant d0 magnetism in the non-magnetic SrCl2 monolayer. This 2D material is an indirect gap insulator with large band gap of 4.97(6.25) eV as obtained by PBE(HSE06) functional, exhibiting ionic character that is generated by the charge transfer from Sr atom to Cl atoms. The monolayer is signiﬁcantly magnetized by doping with alkali metals, where a total magnetic moments between 0.90 and 1.00 µB are obtained. Herein, Cl atoms closest to the doping site make main contribution to the system magnetism. Interestingly, the doped systems exhibit half-metallic behavior that is generated by semiconductor spin-up state and metallic spin-down state. On the other hand, the diluted magnetic semiconductor nature emerges in SrCl2 monolayer as a result of doping with chalcogen atoms. In these cases, total magnetic moment of 1.00 µBis obtained, where magnetic properties are produced mainly by chalcogen impurities and Cl atoms below them. The electronic and magnetic properties of the doped systems are regulated mainly by the outermost p orbital of Cl and chalcogen atoms, and Sr-4d orbital that form mainly the conduction band. Upon further increasing the doping level of K and O atoms, the half-metallic or magnetic semiconductor natures are preserved. Results presented in this work may introduce new prospective 2D spintronic candidates for spintronic applications, which are derived from a non-magnetic SrCl2 monolayer via doping with d0 atoms.

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Stable single-layers of calcium halides (CaX₂, X = F, Cl, Br, I)

Abstract: Paper published as part of the special topic on 2D Materials ARTICLES YOU MAY BE INTERESTED INQuantum properties and applications of 2D Janus crystals and their superlattices Applied Physics Reviews 7, 011311 (2020);

Cited by 15 publications

References 71 publications

Experimental and numerical analysis of Tm²⁺ excited-states dynamics and luminescence in CaX ₂ (X = Cl, Br, I)

Experimental and numerical analysis of Tm²⁺ excited-states dynamics and luminescence in CaX ₂ (X = Cl, Br, I)

Strain Engineering of the Electronic and Optical Properties of Predicted Janus CaFBr Monolayer for Potential Use in Optoelectronic Devices: A Density Functional Theory Study

Inducing d ⁰ magnetism in new SrCl₂ monolayer towards spintronic applications

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Stable single-layers of calcium halides (CaX2, X = F, Cl, Br, I)

Abstract: Paper published as part of the special topic on 2D Materials ARTICLES YOU MAY BE INTERESTED INQuantum properties and applications of 2D Janus crystals and their superlattices Applied Physics Reviews 7, 011311 (2020);

Cited by 15 publications

References 71 publications

Experimental and numerical analysis of Tm2+ excited-states dynamics and luminescence in CaX 2 (X = Cl, Br, I)

Experimental and numerical analysis of Tm2+ excited-states dynamics and luminescence in CaX 2 (X = Cl, Br, I)

Strain Engineering of the Electronic and Optical Properties of Predicted Janus CaFBr Monolayer for Potential Use in Optoelectronic Devices: A Density Functional Theory Study

Inducing d 0 magnetism in new SrCl2 monolayer towards spintronic applications

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Product

Resources

About

Stable single-layers of calcium halides (CaX₂, X = F, Cl, Br, I)

Experimental and numerical analysis of Tm²⁺ excited-states dynamics and luminescence in CaX ₂ (X = Cl, Br, I)

Experimental and numerical analysis of Tm²⁺ excited-states dynamics and luminescence in CaX ₂ (X = Cl, Br, I)

Inducing d ⁰ magnetism in new SrCl₂ monolayer towards spintronic applications