The electronic structure, magnetic and optical properties of B-doped CeO2 (111) surface by first-principles

doi:10.1016/j.physleta.2020.126526

Physics Letters A

Volume 384, Issue 22, 6 August 2020, 126526

https://doi.org/10.1016/j.physleta.2020.126526 Get rights and content

Highlights

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Structural, magnetic and optical properties of B-doped CeO₂ (111) surface were investigated by the first-principles method.
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The B dopants prefer to occupy the O sites under Ce-rich conditions. While the B@Ce cases are more stable under O-rich.
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When B is at the O or Ce site, the B-doped systems produce the magnetic moment of approximately 3 and 1 $μ_{B}$ , respectively.
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The doping of B atoms can effectively improve the absorption efficiency of visible light and lower energy regions.

Abstract

The effects of B-doped CeO₂ surface on electronic, magnetic and optical properties are explored by the first-principles. The replacement of Ce or O sites with B atom in doped CeO₂ depends on the growth environment. For the cases of substitutional B at O site, the covalent bond property of Ce-B bond under the doping systems is more obvious than that of Ce-O bond under the undoped systems. When B is at the Ce site, the B-O bond manifests more stronger ionic property than the Ce-O. When B is at the O or Ce site, the B-doped systems produce the magnetic moment of approximately 3 and 1 $μ_{B}$ , respectively. The calculated optical properties indicate that significant enhancement of the absorption peaks in the near-infrared regions for all doping cases.

Introduction

On account of the excellent characteristics and applications in the field of magnetic and magnetoelectric, the diluted magnetic semiconductors (DMS) have attracted considerable attention in both experimental and theoretical studies. A large number of researches focus on the semiconductors doped with transition metals (TM). For example, TM doped single layer MoS₂, ZnSe, and GaN are studied widely [1], [2], [3]. T. Dietl et al. [4] theoretically predicted that the doping TM in oxide semiconductor material can obtain ferromagnetism. For example, TM-oxide diluted magnetic semiconductors materials (ODMS) [5], [6], [7], [8], [9], [10], [11], [12], [13] can exhibit half metallic properties and quietly high Tc value. ODMS is outstanding magnetic materials in the field of spintronics devices. It is worth noticing that TM clusters may appear in TM-doped ODMS. But nonmetal sp elements doped ODMS can overcome this shortcoming. Many studies reveal that the doping structures can also exhibit better FM state and significantly higher Tc compared with room temperature [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24]. So ODMS doped with sp elements become the burning spot in spintronics.

CeO₂ has a wide band gap and its dielectric constant is higher than other oxides. CeO₂ is not only an indispensable material for catalytic and optical coatings, but also an excellent host material in ODMS. The TM and nonmetal atoms doped CeO₂ improve the various properties of CeO₂ [25], [26], [27], [28], [29], [30], [31]. Li et al. [27] reported that the Cu-doped CeO₂ system can produce the magnetic moment. Jia et al. [32] concluded the conversion of Ce ions from +4 valence to +3 valence for Si-doped CeO₂. However, the studies of the B-doped CeO₂ system were limited to the study of mechanical properties, and there were few studies on magnetic and magnetic coupling mechanisms. Jia et al. [33] theoretically deduced that Si- and B-doped CeO₂ resulted in band gap disappearance and metallic characteristics. Some theoretical and experimental researches prove that the CeO₂ (111) surface is the most stable [34], [35]. The (111) surface was modeled by using the slab geometry comprising 9 and 12 atomic layers [36], [37], [38], [39], respectively. The different structures may lead to the different properties. To demonstrate the effect of the number of atomic layers on the magnetic and optical properties, the 9 and 12 atomic layers CeO₂ (111) surface are studied. The incorporation of B into CeO₂ may replace Ce or O. So the Ce or O atoms in the CeO₂ (111) surface and subsurface are replaced by B atom in this work. The B@O_sur, B@O_sub, B@Ce_sur and B@Ce_sub are represented different doping configurations. The properties of the B-doped CeO₂ surface systems are studied by the first-principles method. The B-doped CeO₂ as a host material may have a huge impact in the field of spintronics and photocatalysis.

Section snippets

Computational methods

The first-principles are used to study the various properties of the doping systems systematically. The calculation is based on spin polarization density functional theory (DFT). Moreover, the projector augmented wave (PAW) pseudopotentials [17] is chosen. The Vienna Ab Initio Simulation Package (VASP) code is used in this study [40]. The GGA+U method can correct the high localization of electrons of Ce 4f states. To determine the suitable U-value, we calculated the band gap of CeO₂ by the

The stability of doping systems

The pure CeO₂ (111) surface with 9 and 12 atomic layers and the different doping positions are shown in Fig. 1. The optimized lattice constant of pure CeO₂ is $a = 5.45$ Å, and the bond length of O-Ce is 2.35 Å. It can be certificated that the parameters adopted are justifiable according to previous studies [46]. The density of states (DOS) of the pure phase is also displayed in Fig. 1. The valence band (VB) and conduction band (CB) are composed of O 2p states and Ce 4f states respectively. To

Conclusions

The influences of B-doped CeO₂ (111) are studied by first-principles calculation. The B dopants prefer to occupy the O sites under Ce-rich conditions. While the B@Ce cases are more stable under O-rich. For substitutional B at O site, the results show that the length of the Ce-B bond in B@O_sur is longer than that of the Ce-O bond in the pure phase. The charge transfer of the Ce atom in doping cases is much smaller than the Ce atom in the undoped systems, which means the Ce-B bond displays

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.

Acknowledgements

This work has been supported by the National Natural Science Foundation of China (51572190).

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The electronic structure, magnetic and optical properties of B-doped CeO2 (111) surface by first-principles

Highlights

Abstract

Introduction

Section snippets

Computational methods

The stability of doping systems

Conclusions

Declaration of Competing Interest

Acknowledgements

Comput. Mater. Sci.

J. Phys. Chem. Solids

Phys. Lett. A

Comput. Mater. Sci.

J. Phys. Chem. Solids

J. Catal.

Comput. Mater. Sci.

Solid State Commun.

J. Alloys Compd.

Catal Commun.

Surf. Sci.

J. Alloys Compd.

Physica B

J. Phys. Condens. Matter

Semicond. Sci. Technol.

Appl. Phys. Lett.

Phys. Rev. B

Mater. Today Commun.

J. Korean Phys. Soc.

Phys. Rev. Lett.

J. Phys. Condens. Matter

J. Appl. Phys.

J. Appl. Phys.

Phys. Status Solidi B

The electronic structure, magnetic and optical properties of B-doped CeO₂ (111) surface by first-principles