Bandgap energy and dielectric function of GaOBr monolayer using density functional theory and beyond

doi:10.1016/j.ssc.2021.114261

Solid State Communications

Volume 329, April 2021, 114261

https://doi.org/10.1016/j.ssc.2021.114261 Get rights and content

Highlights

•
We study the electronic and optical properties of GaOBr monolayer.
•
The GaOBr monolayer is dynamically stable, which determined by their phonon dispersion.
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Our GW results show that the bandgap energy of GaOBr is significantly larger than the bandgaps of REOBr.
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The BSE approach is the best technique to represent the dielectric function of GaOBr.

Abstract

In the last years, 2D materials beyond graphene have a great interest in the field of nanoelectronics and nano-optics applications. Based on the density theory and beyond (i.e., GW, RPA, and BSE), we study the vibrational, electronic, and optical properties of a new 2D GaOBr monolayer. In this framework, we have found that this 2D sheet is dynamically stable, which determined by their phonon dispersion. Our GW results show that the bandgap energy value of this sheet is ~ 5.20 eV, which is larger than the bandgaps of the REOBr monolayers (RE = Tb, Dy, Ho, Er, and Tm). Surprisingly, for the valence band, we have obtained two maxima, one is located at Γ point and the other appears at the X-point. The influence of an electric field on the electronic band structures of the GaOBr monolayer is also studied. In this framework, we obtained the application of the electric field significant changes in the position of VBM and CBM. Furthermore, we found that the BSE approach is the best technique to represent the dielectric function of GaOBr.

Graphical abstract

Introduction

The discovery of graphene [1] has revolutionized the world of modern technology due to its distinctive properties [[2], [3], [4], [5]]. This discovery paved the way for the identification of two-dimensional materials (2D) by mechanical exfoliation [6] or physical vapor deposition [7]. Among these 2D materials, we quote silicene [8], transition metal dichalcogenides (TMDs) [9], phosphorene [10,11], Janus transition metal dichalcogenides (JTMDs) [12], transition-metal compounds (TMC) [13,14], and others [[15], [16], [17], [18]]. Morosely, the TMD bandgap energy (E_g) value does not surpass 3.0 eV and also graphene (or stanene and others) has a zero bandgap energy, therefore they are not proper for optoelectronic applications, e.g., in photocatalytic water splitting [19,20]. Therefore, the search for new 2D materials with a wide band-gaps and stable dynamically became necessary to evade this lack. Notice that the area of research on two-dimensional materials is very active to access new compounds [21,22] that have distinct characteristics compared to other materials, and so can be used in the creation of new electronic devices. In this direction, we obtained in recent decades, a new type of layers systems has taken attention, which is 2D oxybromides [22,23]. The oxybromides layers have great characteristics in optical and luminescent properties [24,25]. These oxybromides films have used in several electronic and optoelectronic fields such as: conductive gas sensors [26], the thermal barrier [27], the optical windows in solar cells [28]. Furthermore, 2D oxybromides have aroused great interest such as the GaOBr monolayer. The crystal system of the GaOBr monolayer is tetragonal (matlockite PbFCl-structure) and its elementary mesh contains two molecules. Theoretically, Guo et al. [29] have computed the electronic properties of the CrSBr and CrOBr monolayers. Recently, Kai Xu et al. [30] have studied the electronic structure and magnetic anisotropy of single-layer rare-earth oxybromide REOBr (RE = Tb, Dy, Ho, Er, and Tm). Also, Zhang et al. [31] have investigated the electronic band structures of the BiOBr bulk. Experimentally, Yan and co-workers [32] we have successfully prepared a series of monodisperse and well-shaped nanocrystals of lanthanide oxybromides (LnOBr) bulks. Hai Guo [33] has prepared the LaOBr (0.1%) powders by solid-state reaction. H $\ddot{a}$ ls $\ddot{a}$ et al. [34,35] have studied the effective magnetic moment of the SmOX (X = F, Cl, and Br) rare earth oxybromides. Moreover, Song et al. [36] have successfully examined the visible light-activated Zn-doped BiOBr hierarchical nanostructures. Zhou et al. [37] have shown that the large indirect bandgap (2.8 eV) of BiOBr hinders its practical applications under visible light. Despite all these studies, but it does not meet all aspirations. Thus, we urgently need to find new material with distinct properties. In the present work, we investigate the structural, vibrational, electronic, and optical properties of 2D GaOBr monolayer, employing density functional theory (DFT) [38] and beyond [39]. A noticeable point is that as of now, there is no theoretical or experimental work on the GaOBr single layer. The present paper is divided as follows: in Sec. 2 we describe our computational details. We present our results in Sec. 3, and we conclude in Sec. 4.

Section snippets

Computational details

Our ab-initio total-energy and force calculations are based on the density functional theory as achieved in the Vienna ab-initio simulation package (VASP) [40] code. Electron-ion interactions are treated within the projector-augmented wave (PAW) [41]. Exchange and correlation was approximated using either the local density approximation (LDA) adapted by Ceperly and Alder (CA) [42], or the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) [43] with a plane wave cutoff of

Results and discussion

In Fig. 1, we present the geometric structure of the GaOBr monolayer. The thickness of this sheet is ~ 6.10 Å with the HSE functional and its crystal system is tetragonal, which contains two molecules/unit cell. Upon relaxation by HSE functional, we found that the Ga–Ga, Ga–O, and Ga–Br bond lengths are 3.12, 2.10, and 2.52 Å, respectively. Besides, the O-Ga-O and O-Ga-Br bond angles are 38.60 and 83.60°. The lattice constant of GaOBr is 3.69 Å with LDA and 3.73 Å with GGA, while is around

Conclusion

In this article, we have systemically investigated the vibration, electronic, and optical properties of GaOBr monolayer, using density functional theory and beyond. We obtained this monolayer is dynamically stable since there are not the imaginary modes in their phonon dispersion, confirming the stability of 2D form of this compound. We found that the GW calculations show that the bandgap energy value of this sheet is ~ 5.20 eV, which is larger than the bandgaps of the REOBr monolayers.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

Thank all researchers from the University of Monastir for their help in analyzing these results. Also, the authors are grateful to King Khalid University for their continuous support during the conduction of this work.

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Bandgap energy and dielectric function of GaOBr monolayer using density functional theory and beyond

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Computational details

Results and discussion

Conclusion

Declaration of competing interest

Acknowledgments

J. Mol. Graph. Model.

Mater. Chem. Phys.

Appl. Mater. Today

Opt. Mater.

J. Mol. Catal. Chem.

Phys. Scripta

Science

Science

Nature

Science

Phys. Rev. Lett.

ACS Nano

ACS Nano

Chem. Soc. Rev.

Science

Nat. Commun.

Appl. Phys. Lett.

J. Appl. Phys.

Nature

Nat. Nanotechnol.

J. Phys. Condens. Matter

Phys. Chem. Chem. Phys.

Chem. Chem. Phys.

J. Appl. Phys.

Nano Res

Phys. Rev. B

Beilstein J. Nanotechnol.

J. Mater. Sci.