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Electronic structure and magnetic properties of 3d transition-metal atom adsorbed SnO monolayers
Applied Surface Science 493 (2019) 404–410
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Electronic structure and magnetic properties of 3d transition-metal atom adsorbed SnO monolayers
T
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K. Niea, X.C. Wanga, , W.B. Mib a Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Electrical and Electronic Engineering, Tianjin University of Technology, Tianjin 300384, China b Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology, School of Science, Tianjin University, Tianjin 300354, China
A R T I C LE I N FO
A B S T R A C T
Keywords: SnO monolayer Transition metal atoms Adsorption Spin polarization Magnetic anisotropy
Monolayer SnO has attracted extensive attention due to the unique electronic properties, which have potential applications in nanoelectronic and optoelectronic devices. Transition metal (TM) atoms are often used to modulate electronic structures and magnetic properties of two dimensional (2D) materials, which can facilitate the application of these materials in spintronic devices. The electronic structure and magnetic characteristics of 3d TM (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) adsorbed SnO monolayer are predicted by first-principle calculations. The n-type doping in the SnO monolayer appears when Sc, Ti, V, Cr, Mn, Fe and Zn atoms are adsorbed. Co, Ni and Cu adsorptions induce the p-type doping in the SnO monolayer. In addition, the magnetic moments of SnO in the adsorption systems are in the range from −0.038 to 0.414 μB, and that reach the maximum at the case of Ni-absorbed. It is also found that Fe, Co and Ni adsorbed SnO monolayers have a perpendicular magnetic anisotropy (PMA), while Ti, V, Cr and Mn adsorbed SnO monolayers have an in-plane magnetic anisotropy (IMA). Our results indicate that TM adsorbed SnO monolayers have the potential applications in spintronic devices.
1. Introduction The discovery of graphene has intrigued strong interest in two-dimensional (2D) materials, including phosphorene [1], transition metal dichalcogenides (TMDCs) [2], MoS2 [3], stanene [4], and silicone [5]. Meanwhile, magnetic 2D materials have been paid much attention due to their possible applications in novel spintronic devices. However, some intrinsic deficiencies limit their practical applications, where the zero band gap nature of graphene limits its applications in digital electronic devices [6], and a transition from 1T to 2H phase of MoS2 limits the operating temperature of the devices [7]. Therefore, there is an urgent need to discover or design novel 2D materials with desire properties. Recently, tin monoxide (SnO), with thickness of a few atomic layers, has been experimentally synthesized [8]. The monolayer SnO has been paid intensive attention due to its unique semiconducting characteristics and bipolar conductivity [9]. In particular, previous results show that SnO have a large optical band gap, excellent transparency and resistance to oxidation [10–14]. Monolayer SnO can be applied to flexible electronic and optoelectronic devices. However, it is necessary to induce the magnetism in monolayer SnO for its applications in spintronic devices. Tao et al. illustrated that B-, C-, N-, O- and F-
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adsorption can tailor the band structure and magnetic properties of monolayer SnO [15]. Houssa et al. theoretically predicted that the hole doping can induce the ferromagnetic order in monolayer SnO [16]. Wang et al. found that 3d transition metal atom doping can induce the magnetism in monolayer SnO [17]. Transition metal (TM) atoms are often used to modulate magnetic and electronic properties of 2D materials, which can facilitate the application of these materials in spintronic devices [18–20]. He et al. studied the magnetic and electronic properties of 3d TM absorbed graphene, which can facilitate the application of graphene in spintronic devices [18]. Wang et al. illustrated that the 3d TM adsorption on MoS2 monolayer can make it magnetization [21]. Ju et al. theoretically predicted that TM atoms (Sc, Ti, V, Cr, Mn, Fe and Co) can induce the spin polarization in monolayer InSe [22]. Until now, no experimental or theoretical results on adsorption of 3d TM atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) adsorbed SnO monolayers are reported. Consequently, it is significant that study the effects of TM absorption on the 2D SnO. In this work, the electronic structure and magnetic characteristics of 3d TM (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) adsorbed SnO monolayer are calculated by first-principles calculations. The n-type
Corresponding author. E-mail address: [email protected] (X.C. Wang).
https://doi.org/10.1016/j.apsusc.2019.07.054 Received 12 April 2019; Received in revised form 12 June 2019; Accepted 7 July 2019 Available online 09 July 2019 0169-4332/ © 2019 Elsevier B.V. All rights reserved.
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K. Nie, et al.
For TM atom, there are four possible initial adsorption sites based on the symmetry of SnO monolayer, which marked in Fig. 1(a). The possible initial adsorption sites are denoted as T1, T2, B and H, which mean the TM atoms occupy the sites above the Sn atom, O atom, between SneO bond and the hollow site of the quadrangle ring, respectively. Fig. 1(b) shows the band structure of SnO (3 × 3) monolayer. Obviously, the monolayer SnO is a semiconductor with an indirect band gap of 3.281 eV. The valence band maximum (VBM) of SnO locates at M point, and the conduction band minimum (CBM) locates at Γ point. In order to investigate the effects of 3d TM adsorption on SnO monolayer, we calculate the Ead of all situations. Fig. 2 shows the relaxed structures for the most stable TM adsorbed SnO systems. It is found that the TM atoms (Sc, Ti, V, Cr, Mn, Fe, Cu, Zn) prefer to relax at T1 site on SnO monolayer. The Co and Ni atoms prefer to adsorb at the T2 and B sites. All the TM atoms do not favor the H site. The values of Ead can be used to judge the binding strength between the TM atoms and SnO monolayer. The adsorption energies of all the stable TM adsorbed SnO systems are listed in Table 1. The binding energies are in the range from −0.567 to −4.17 eV, so the order of adsorption strength is Co > Ti > Ni > V > Sc > Cu > Fe > Cr > Mn > Zn. The Co and Ti adsorbed SnO monolayers have a larger binding energy than others. Zn atom has the weakest binding with SnO monolayer. Moreover, other structural parameters of TM adsorbed SnO monolayers are also listed in Table 1, such as the TM adatom height over SnO surface (h), the distance between the TM adatom and the nearest Sn (O) under the most stable configurations (dTM-Sn/O). The height between adatom and SnO surface ranges from 1.338 Å to 2.342 Å. The largest adatom height (h) is 2.342 Å, where Sc locates at the T1 site. The bond length between TM adatom and the nearest Sn (O) is in the range from 2.771 to 3.559 Å. The bond length of TM atoms (Sc, Ti, V, Cr, Mn, Fe, Cu, Zn) at T1 site is larger than that at other sites. The magnetic moments of 3d TM adsorbed SnO monolayer are investigated. The magnetic moments of TM atoms (μTM) and SnO layer (μSnO) are listed in Table 1. The ground state of pure SnO monolayer is nonmagnetic, so the magnetism of the TM adsorbed SnO monolayer comes from the TM atoms. The magnetic moments of Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu are 0.839, 2.696, 3.753, 4.777, 4.738, 3.500, 2.209, 1.086 and 0.176 μB, respectively. The magnetic moments of SnO layer in the adsorbed systems are in the range from −0.038 to 0.414 μB, which reaches the maximum at the Ni-absorbed case. However, neither isolated Zn atom nor its adsorption system has magnetic moment. Therefore, we mostly focus on Ti, V, Cr, Mn, Fe, Co, Ni, and Cu adsorbed cases, which have larger magnetic moments. The SnO monolayer is induced with magnetism by absorbing TM atoms, which has the potential applications in 2D SnO-based spintronic devices. In order to explore the magnetic ground state of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu adsorption, the magnetic coupling (EAFM-FM) is investigated by calculating energy difference between antiferromagnetic (AFM) and ferromagnetic (FM) states [36]. The EAFM-FM between 3d transition metal adsorbed SnO monolayer are listed in Table 1. For Ti, V, Mn, Fe, and Cu adsorbed cases, the FM state is found to be more energetically stable and the values of EAFM-FM are 0.602, 3.886, 0.197, 0.666, and 0.001 eV, respectively. While for Sc, Cr, Co and Ni adsorption, the AFM configuration is the magnetic ground state with the lower energy, where the value ranges from −0.461 to −0.018 eV. In order to understand the electronic properties of TM adsorbed SnO monolayer, we study the band structures of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn adsorbed SnO monolayers. Fig. 3 shows the band structure of the most stable cases, where the red and blue solid lines represent the bands of TM-adsorbed SnO monolayers in the spin-up and spin-down channels, respectively. Meanwhile, the spin-up and spin-down states of the Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu adsorbed SnO monolayers do not overlap, which are different from the isolated SnO monolayer, suggesting that the spin polarization is induced in these systems. The band gaps of adsorbed SnO are in the range of 0.283–1.432 eV, which shows a half-semiconducting property. The Zn-adsorbed SnO preserve the
doping in SnO monolayers appears when Sc, Ti, V, Cr, Mn, Fe and Zn atoms are adsorbed. Co, Ni and Cu adsorptions induce the p-type doping in SnO monolayers. In addition, the magnetic moments of 3d TM adsorbed structures from Sc to Cu are in the range from 0.032 to 0.259 μB, while no magnetic moments appears in Zn adsorbed case. The adsorption of TM atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu) can make the SnO monolayer turn into half-semiconducting characteristics. Furthermore, Fe, Co and Ni adsorbed SnO monolayers have a perpendicular magnetic anisotropy (PMA), while Ti, V, Cr and Mn adsorbed SnO monolayers have an in-plane magnetic anisotropy (IMA). Co adsorbed SnO have the largest PMA of −0.103 mJ/m2. The results reveal that the 3d TM adsorbed SnO monolayer can be used as spintronic devices. 2. Calculation details The density functional theory (DFT) is employed to all the calculations by the Vienna ab initio Simulation Package [23]. The projectoraugmented wave (PAW) method is used to describe the interaction between electrons and ions [24]. The Perdew-Burke-Ernzerh of (PBE) form of generalized gradient approximation (GGA) is adopted to deal with the electronic exchange-correlation interaction [25–27]. The DFT + D2 method of Grimme is added to take into account the van der Waals interaction [28]. At different cutoff energy, the magnetic anisotropy energy of Co atom gradually decreases and then it reaches steady state at 450 eV. So, the cutoff energy of 500 eV can reproduce the magnetic anisotropy energy for 3d TM adsorbed monolayer SnO systems. At different k-point mesh, the magnetic anisotropy energy of Co atom appears fluctuated until it reaches stability in 6 × 6 × 1 k-point mesh. Therefore, the 7 × 7 × 1 k-point mesh is adopted throughout the calculations for the 3d TM adsorbed monolayer SnO systems [29,30]. A 18-Å thick vacuum layer is added to prevent the coupling between adjacent periodic images. The energy and force convergence criteria are 10−5 eV and 0.01 eV/Å, respectively. The Coulomb interaction (GGA + U) is introduced to describe the d electrons of TM atom [31]. U = 4.5 eV and J = 0 eV are set for the TM d orbital, where the value of Ueff = U-J is effective in the calculations. The stability and feasibility of the different adsorption configurations are evaluated by using the adsorption energy Ead = Etotal-ESnO-ETM, where Etotal represents the total energy of SnO monolayer with the adsorbed TM atoms, ESnO is the total energy of the 3 × 3 supercell for SnO monolayer, and ETM is the total energy of the isolated TM atom in its ground state. Based on the secondorder perturbation theory [32–35], the MAE is expressed as | ψ | L̂ | ψ
|2 − | ψ | L ̂ | ψ
|2
MAE ∝ ξ 2 ∑o,u o z u E − E o x u , where ψo and ψu indicate the u o occupied and unoccupied states, respectively. Eo and Eu are the eigen energies of the occupied and unoccupied states, respectively. ξ is the SOC constant. The MAE depends on the couplings between the occupied and unoccupied states through the orbital angular momentum operators L x̂ and L ẑ . The small energy separation (Eu, Eo) between the occupied and unoccupied states is responsible for the variation of MAE. In addition, MAE is obtained by MAE = E[001]-E[100], where E[001] and E[100] are the energies with the magnetization in the out-of-plane and in-plane directions, respectively [33]. The positive and negative values of MAE represent the in-plane magnetic anisotropy (IMA) and perpendicular magnetic anisotropy (PMA), respectively [34]. 3. Results and discussion The optimized atomic structure of SnO monolayer is shown in Fig. 1(a). The stable phase of SnO monolayer has a tetragonal litharge structure, where two O atoms and two Sn atoms form a pyramid structure. The lattice constant and the bond length of SneO are 3.83 and 1.805 Å, which well agree with the experimental values [10]. In the models, a single TM atom is adsorbed on a 3 × 3 × 1 SnO monolayer, where the system contains 18 Sn atoms, 18 O atoms and one TM atom. 405
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Fig. 1. (a) Top and side views for (3 × 3) supercell of SnO monolayer. Four adsorption sites, hollow (H), top (T1 and T2), and bridge (B), are marked on the SnO lattice in the 3 × 3 supercell. (b) The band structure of the pure monolayer SnO.
Fig. 2. Top and side view of the most stable structures of TM adsorbed SnO monolayer. Table 1 The adsorption energy (Ead), the bond length between TM atom and the nearest Sn(O) atom (dTM-Sn/O), the vertical height over the nearest Sn(O) atom of the top surface plane (h), charge transfer from TM atom to SnO (Δq), magnetic moment of TM adatom (μTM) and SnO layer (μSnO), the band gap (Eg) at the most stable state for all the TM atom adsorption systems and magnetic coupling (EAFM-FM) between 3d transition metal adsorbed atoms.
Sc Ti V Cr Mn Fe Co Ni Cu Zn
Ead (eV)
dTM-Sn/O (Å)
h (Å)
μTM (μB)
μSnO (μB)
Eg (eV)
−1.450 −3.194 −2.340 −0.880 −0.651 −0.982 −4.170 −2.730 −1.342 −0.567
3.559 3.298 3.297 3.359 3.477 3.200 2.781 2.771 2.934 3.457
2.342 1.919 1.921 1.951 2.201 1.775 1.928 1.544 1.338 2.163
0.839 2.696 3.753 4.777 4.738 3.500 2.209 1.086 0.176 0
−0.038 0.401 0.346 0.310 −0.043 0.155 0.300 0.414 0.410 0
0.475 0.911 0.999 1.160 1.432 0.475 0.645 0.443 0.283 2.641
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Δq (e) 0.357 0.380 0.260 0.178 0.171 0.100 −0.012 −0.156 −0.086 0.022
EAFM-FM (eV) −0.355 0.602 3.886 −0.081 0.197 0.666 −0.461 −0.018 0.001 0
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Fig. 3. Band structure of single TM adsorbed SnO monolayer. Fermi level is set to zero. The solid red and blue lines represent the spin-up and spin-down channels, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 4. Top and side views of the charge density differences in TM adsorbed SnO monolayers. Yellow and blue regions represent the charge gain and loss, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 5. Density of states of single TM adsorbed SnO monolayers.
In order to analyze the orbital hybridization of the TM adsorbed SnO, the total density of states (TDOS) and partial density of states (PDOS) of the TM, Sn and O atoms are shown in Fig. 5. Obviously, the TM atoms induce the asymmetric distribution between the spin-up and spin-down states. The TDOS demonstrate the semiconducting characteristics of TM adsorbed SnO monolayer. The adsorption of TM atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu) can induce the magnetic moments in SnO monolayer. Therefore, the SnO monolayers in the adsorbed systems turn into magnetic semiconductor. The spin polarization appears in the Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu adsorbed systems. For Sc-adsorbed case, the Sc px orbit strongly couple with O pz orbit at the valence band maximum. For Ti-adsorption case, Ti s orbit couples with pz orbit of O and Sn in the range from −0.7 to −0.3 eV in the spin-up state. In the spin-up channel, V d orbit of couples with O py, pz orbits and Sn s, pz orbits in the range from −1.8 to −1.6 eV. The Cr s orbit couples with pz orbit of O and Sn in the range from −0.7 to −0.4 eV. In the spin-down channel, the couple between pz orbit of O and s orbit of Sn and Cr is mainly in the energy range from 0.5 to 0.8 eV. For Mn adsored case, in the spin-up channel, Mn s orbit have strong couple with pz orbit of O and s, pz and dz2 orbits of Sn in the range from −0.8 to −1.2 eV. In the spin-down state, the couple between s orbit of Mn and
band structure of pure SnO monolayer, where the band gap is 2.641 eV. The charge transfer between the TM atoms and SnO monolayers is calculated by using Bader charge analysis, as shown in Table 1. The values of Δq are 0.357e, 0.380e, 0.260e, 0.178e, 0.171e, 0.010e, −0.012e, −0.156e, −0.086e and 0.022e for Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn adsorbed SnO monolayers, where the positive values indicate the electrons transfer from TM atom to SnO monolayer. Therefore, the n-type doping in SnO monolayers appears when Sc, Ti, V, Cr, Mn, Fe and Zn atoms are adsorbed, while Co, Ni and Cu adsorptions induce the p-type doping in SnO monolayers. In order to further investigate the bonding mechanism, the charge density differences of the adsorbed systems are shown in Fig. 4. The yellow and blue regions represent the gain and loss electrons, respectively. The charge transfer mainly occurs between TM atoms and neighboring Sn (O) atoms. Moreover, Sn and TM atoms lose electrons while O atoms gain electrons in the interface. The large charge transfer has great influence on the electronic structure of SnO monolayer. Particularly, in Fig. 4, the yellow areas between Ti atom and monolayer SnO are the most obvious by comparing with other systems, indicating that the Ti adsorbed SnO generates the largest charge transfer and the orbital hybridization is the strongest. 408
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Fig. 6. The 3d orbital resolved MAE of TM atom in TM adsorbed SnO monolayers, (a) Ti, (b) V, (c) Cr, (d) Mn, (e) Fe, (f) Co and (g) Ni. (h) The layer resolved MAE of TM adsorbed SnO monolayers.
pz orbit of O and Sn is mainly in the energy ranges from −0.4 to −0.7 eV. For Fe-adsorbed SnO monolayer, in the spin-up channel, Fe s orbit couples to pz orbit of O and Sn in the range from −0.4 to −0.7 eV, while in the spin-down channel the Fe s and dz2 orbits couple to py and pz orbits of O and pz orbit of Sn in the energy ranges from −0.3 to 0.3 eV. Co, Ni and Cu adsorbed cases are similar, where TM s orbit couples with p orbits of O and Sn in the energy ranges from −0.3 to −0.3 eV. For nonmagnetic Zn adsorption, no spin polarization appears so the spin up and spin down states are perfectly symmetrical. The magnetic anisotropy of Sc, Cu and Zn atoms is not obvious, so we will focus on other atoms. Fig. 6 shows the d-orbital resolved MAE of Ti, V, Cr, Mn, Fe, Co and Ni atoms in adsorbed systems. The main contributions from Ti and Fe atoms come from the matrix element differences between dyz and dx2−y2 orbitals, which are positive. For V atom, a large positive contribution comes from the matrix element differences between dyz and dz2 orbitals. For Cr atom, the positive contribution comes from the matrix element differences between dyz and dz2 orbitals, but the matrix element differences between dxy and dx22 y orbitals give the negative contribution. By comparing with Cr atom, for Mn-adsorbed case, the matrix element differences between dyz and dz2 as well as dxy and dx2-y2 orbitals offer the opposite contribution. However, the contribution from Mn atom is larger than Cr atom. The main contributions of Co atom can be ascribed to the matrix element differences between dyz and dz2 orbitals as well as dyz and dx2-y2, which are negative. For Ni atom, the large positive contribution comes from the matrix element differences between dxy and dx2-y2 orbitals. Fig. 6(h) shows the layer-resolved MAE of SnO monolayers adsorbed by different atoms. The Fe, Co and Ni adsorbed SnO monolayers show perpendicular MAE, which are −0.0196, −0.103 and −0.0038 mJ/m2, respectively. The Ti, V, Cr and Mn adsorbed SnO monolayers have an in-plane MAE, which are in the range from 0.003 to 0.010 mJ/m2.
is nonmagnetic. The magnetic moment of SnO monolayer in the adsorbed systems changes from −0.038 to 0.414 μB, which reaches the maximum in Ni-absorbed case. The Fe, Co and Ni adsorbed SnO monolayers have the perpendicular magnetic anisotropy, while the Ti, V, Cr and Mn adsorbed SnO monolayers induce the in-plane magnetic anisotropy. The Co adsorbed SnO monolayer has the largest PMA of −0.103 mJ/m2. Our results reveal that 3d absorbed SnO monolayers have potential applications in spintronic devices. Acknowledgements This work is supported by the Key Project of the Natural Science Foundation of Tianjin City (18JCZDJC99400). References [1] H. Liu, A.T. Neal, Z. Zhu, Z. Luo, X. Xu, D. Tománek, P.D. Ye, ACS Nano 8 (2014) 4033. [2] Q.H. Wang, K. Kalantar-Zadeh, A. Kis, J.N. Coleman, M.S. Strano, Nat. Nanotechnol. 7 (2012) 699. [3] K.F. Mak, K. He, J. Shan, T.F. Heinz, Nat. Nanotechnol. 7 (2012) 494. [4] M. Modarresi, A. Kakoee, Y. Mogulkoc, M.R. Roknabadi, Comput. Mater. Sci. 101 (2015) 164. [5] N.D. Drummond, V. Zolyomi, V.I. Fal’Ko, Phys. Rev. B 85 (2012) 075423. [6] K.S. Novoselov, S.V. Morozov, T.M.G. Mohinddin, L.A. Ponomarenko, D.C. Elias, R. Yang, I.I. Barbolina, P. Blake, T.J. Booth, D. Jiang, J. Giesbers, E.W. Hill, A.K. Geim, Phys. Status Solidi 244 (2007) 4106. [7] H.F. Bai, L.C. Xu, M.Y. Di, L.Y. Hao, Z. Yang, R.P. Liu, X.Y. Li, J. Appl. Phys. 123 (2018) 95301. [8] K.J. Saji, K. Tian, M. Snure, A. Tiwari, Adv. Electron. Mater. 2 (2016) 1500453. [9] W. Zhou, N. Umezawa, Phys. Chem. Chem. Phys. 17 (2015) 17816. [10] J. Du, C. Xia, Y. Liu, X. Li, Y. Peng, S. Wei, Appl. Surf. Sci. 401 (2017) 114. [11] J.A. Caraveo-Frescas, H.N. Alshareef, Appl. Phys. Lett. 103 (2013) 222103. [12] T. Yang, J. Zhao, X. Li, X. Gao, C. Xue, Y. Wu, R. Tai, Mater. Lett. 139 (2015) 39. [13] H. Hayashi, S. Katayama, R. Huang, K. Kurushima, I. Tanaka, Phys. Status Solidi (RRL) 9 (2015) 192. [14] Y. Ogo, H. Hiramatsu, K. Nomura, H. Yanagi, T. Kamiya, M. Hirano, H. Hosono, Appl. Phys. Lett. 93 (2008) 032113. [15] J. Tao, L. Guan, Sci. Rep. 7 (2017) 44568. [16] M. Houssa, K. Iordanidou, G. Pourtois, V.V. Afanas’ ev, A. Stesmans, ECS Trans. 80 (2017) 339. [17] Y.R. Wang, S. Li, J.B. Yi, J. Phys. Chem. C 122 (2018) 4651. [18] G. Yu, M. Zhu, Y. Zheng, J. Mater. Chem. C 2 (2014) 9767. [19] Q. Pang, L. Li, C. Zhang, X.M. Wei, Y.L. Song, Mater. Chem. Phys. 160 (2015) 96. [20] J.M. Zhang, S.F. Wang, L.Y. Chen, K.W. Xu, V. Ji, Eur. Phys. J. B 76 (2010) 289. [21] Y. Wang, B. Wang, R. Huang, B. Gao, F. Kong, Q. Zhang, Phys. E Amsterdam, Neth. 63 (2014) 276. [22] W. Ju, T. Li, Q. Zhou, H. Li, X. Li, D. Ma, Comput. Mater. Sci. 150 (2018) 33. [23] G. Kresse, J. Furthmüller, Phys. Rev. B 54 (1996) 11169. [24] G. Kresse, D. Joubert, Phys. Rev. B 59 (1999) 1758. [25] J.P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 77 (1996) 3865. [26] J.J. Mortensen, Phys. Rev. B: Condens. Matter Mater. Phys. 71 (2005) 391. [27] S. Grimme, J. Comput. Chem. 27 (2006) 1787.
4. Conclusion The electronic structure and magnetic characteristics of 3d TM adsorbed SnO monolayers are investigated by first-principles calculations. After the structure optimization, the TM atoms (Sc, Ti, V, Cr, Mn, Fe, Cu and Zn) prefer to locate at T2 site on SnO monolayer. However, the Co and Ni atoms prefer to locate at T1 and B sites. The adsorption energies are in the range from −0.567 to −4.17 eV. The n-type doping in SnO monolayer appears when Sc, Ti, V, Cr, Mn, Fe and Zn atoms are adsorbed. The Co, Ni and Cu adsorptions induce the p-type doping in SnO monolayer. The Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu adsorbed SnO monolayers show the magnetism, but the Zn adsorbed SnO monolayer 409
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[33] D.S. Wang, R. Wu, A.J. Freeman, Phys. Rev. B 47 (1993) 14932. [34] P.V. Ong, N. Kioussis, P.K. Amiri, J.G. Alzate, K.L. Wang, G.P. Carman, J. Hu, R. Wu, Phys. Rev. B 89 (2014) 991. [35] P. Gambardella, S. Rusponi, M. Veronese, S.S. Dhesi, C. Grazioli, A. Dallmeyer, I. Cabria, R. Zeller, P.H. Dederichs, K. Kern, Science 300 (2003) 1130. [36] X. Cai, C. Niu, J. Wang, W. Yu, X.Y. Ren, Z. Zhu, Phys. Lett. A 381 (2017) 1236.
[28] [29] [30] [31]
T. Bucko, J. Hafner, S. Lebegue, J.G. Angyán, J. Phys. Chem. A 114 (2010) 11814. L.L. Li, H. Zhang, X.L. Cheng, Y. Miyamoto, Appl. Surf. Sci. 441 (2018) 647. H.J. Monkhorst, J.D. Pack, Phys. Rev. B 13 (1976) 5188. S.L. Dudarev, G.A. Botton, S.Y. Savrasov, C.J. Humphreys, A.P. Sutton, Phys. Rev. B 57 (1998) 1505. [32] D. Li, C. Barreteau, M.R. Castell, F. Silly, A. Smogunov, Phys. Rev. B 90 (2014) 205409.
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Electronic structure and magnetic properties of 3d transition-metal atom adsorbed SnO monolayers
T
⁎
K. Niea, X.C. Wanga, , W.B. Mib a Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Electrical and Electronic Engineering, Tianjin University of Technology, Tianjin 300384, China b Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology, School of Science, Tianjin University, Tianjin 300354, China
A R T I C LE I N FO
A B S T R A C T
Keywords: SnO monolayer Transition metal atoms Adsorption Spin polarization Magnetic anisotropy
Monolayer SnO has attracted extensive attention due to the unique electronic properties, which have potential applications in nanoelectronic and optoelectronic devices. Transition metal (TM) atoms are often used to modulate electronic structures and magnetic properties of two dimensional (2D) materials, which can facilitate the application of these materials in spintronic devices. The electronic structure and magnetic characteristics of 3d TM (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) adsorbed SnO monolayer are predicted by first-principle calculations. The n-type doping in the SnO monolayer appears when Sc, Ti, V, Cr, Mn, Fe and Zn atoms are adsorbed. Co, Ni and Cu adsorptions induce the p-type doping in the SnO monolayer. In addition, the magnetic moments of SnO in the adsorption systems are in the range from −0.038 to 0.414 μB, and that reach the maximum at the case of Ni-absorbed. It is also found that Fe, Co and Ni adsorbed SnO monolayers have a perpendicular magnetic anisotropy (PMA), while Ti, V, Cr and Mn adsorbed SnO monolayers have an in-plane magnetic anisotropy (IMA). Our results indicate that TM adsorbed SnO monolayers have the potential applications in spintronic devices.
1. Introduction The discovery of graphene has intrigued strong interest in two-dimensional (2D) materials, including phosphorene [1], transition metal dichalcogenides (TMDCs) [2], MoS2 [3], stanene [4], and silicone [5]. Meanwhile, magnetic 2D materials have been paid much attention due to their possible applications in novel spintronic devices. However, some intrinsic deficiencies limit their practical applications, where the zero band gap nature of graphene limits its applications in digital electronic devices [6], and a transition from 1T to 2H phase of MoS2 limits the operating temperature of the devices [7]. Therefore, there is an urgent need to discover or design novel 2D materials with desire properties. Recently, tin monoxide (SnO), with thickness of a few atomic layers, has been experimentally synthesized [8]. The monolayer SnO has been paid intensive attention due to its unique semiconducting characteristics and bipolar conductivity [9]. In particular, previous results show that SnO have a large optical band gap, excellent transparency and resistance to oxidation [10–14]. Monolayer SnO can be applied to flexible electronic and optoelectronic devices. However, it is necessary to induce the magnetism in monolayer SnO for its applications in spintronic devices. Tao et al. illustrated that B-, C-, N-, O- and F-
⁎
adsorption can tailor the band structure and magnetic properties of monolayer SnO [15]. Houssa et al. theoretically predicted that the hole doping can induce the ferromagnetic order in monolayer SnO [16]. Wang et al. found that 3d transition metal atom doping can induce the magnetism in monolayer SnO [17]. Transition metal (TM) atoms are often used to modulate magnetic and electronic properties of 2D materials, which can facilitate the application of these materials in spintronic devices [18–20]. He et al. studied the magnetic and electronic properties of 3d TM absorbed graphene, which can facilitate the application of graphene in spintronic devices [18]. Wang et al. illustrated that the 3d TM adsorption on MoS2 monolayer can make it magnetization [21]. Ju et al. theoretically predicted that TM atoms (Sc, Ti, V, Cr, Mn, Fe and Co) can induce the spin polarization in monolayer InSe [22]. Until now, no experimental or theoretical results on adsorption of 3d TM atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) adsorbed SnO monolayers are reported. Consequently, it is significant that study the effects of TM absorption on the 2D SnO. In this work, the electronic structure and magnetic characteristics of 3d TM (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) adsorbed SnO monolayer are calculated by first-principles calculations. The n-type
Corresponding author. E-mail address: [email protected] (X.C. Wang).
https://doi.org/10.1016/j.apsusc.2019.07.054 Received 12 April 2019; Received in revised form 12 June 2019; Accepted 7 July 2019 Available online 09 July 2019 0169-4332/ © 2019 Elsevier B.V. All rights reserved.
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For TM atom, there are four possible initial adsorption sites based on the symmetry of SnO monolayer, which marked in Fig. 1(a). The possible initial adsorption sites are denoted as T1, T2, B and H, which mean the TM atoms occupy the sites above the Sn atom, O atom, between SneO bond and the hollow site of the quadrangle ring, respectively. Fig. 1(b) shows the band structure of SnO (3 × 3) monolayer. Obviously, the monolayer SnO is a semiconductor with an indirect band gap of 3.281 eV. The valence band maximum (VBM) of SnO locates at M point, and the conduction band minimum (CBM) locates at Γ point. In order to investigate the effects of 3d TM adsorption on SnO monolayer, we calculate the Ead of all situations. Fig. 2 shows the relaxed structures for the most stable TM adsorbed SnO systems. It is found that the TM atoms (Sc, Ti, V, Cr, Mn, Fe, Cu, Zn) prefer to relax at T1 site on SnO monolayer. The Co and Ni atoms prefer to adsorb at the T2 and B sites. All the TM atoms do not favor the H site. The values of Ead can be used to judge the binding strength between the TM atoms and SnO monolayer. The adsorption energies of all the stable TM adsorbed SnO systems are listed in Table 1. The binding energies are in the range from −0.567 to −4.17 eV, so the order of adsorption strength is Co > Ti > Ni > V > Sc > Cu > Fe > Cr > Mn > Zn. The Co and Ti adsorbed SnO monolayers have a larger binding energy than others. Zn atom has the weakest binding with SnO monolayer. Moreover, other structural parameters of TM adsorbed SnO monolayers are also listed in Table 1, such as the TM adatom height over SnO surface (h), the distance between the TM adatom and the nearest Sn (O) under the most stable configurations (dTM-Sn/O). The height between adatom and SnO surface ranges from 1.338 Å to 2.342 Å. The largest adatom height (h) is 2.342 Å, where Sc locates at the T1 site. The bond length between TM adatom and the nearest Sn (O) is in the range from 2.771 to 3.559 Å. The bond length of TM atoms (Sc, Ti, V, Cr, Mn, Fe, Cu, Zn) at T1 site is larger than that at other sites. The magnetic moments of 3d TM adsorbed SnO monolayer are investigated. The magnetic moments of TM atoms (μTM) and SnO layer (μSnO) are listed in Table 1. The ground state of pure SnO monolayer is nonmagnetic, so the magnetism of the TM adsorbed SnO monolayer comes from the TM atoms. The magnetic moments of Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu are 0.839, 2.696, 3.753, 4.777, 4.738, 3.500, 2.209, 1.086 and 0.176 μB, respectively. The magnetic moments of SnO layer in the adsorbed systems are in the range from −0.038 to 0.414 μB, which reaches the maximum at the Ni-absorbed case. However, neither isolated Zn atom nor its adsorption system has magnetic moment. Therefore, we mostly focus on Ti, V, Cr, Mn, Fe, Co, Ni, and Cu adsorbed cases, which have larger magnetic moments. The SnO monolayer is induced with magnetism by absorbing TM atoms, which has the potential applications in 2D SnO-based spintronic devices. In order to explore the magnetic ground state of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu adsorption, the magnetic coupling (EAFM-FM) is investigated by calculating energy difference between antiferromagnetic (AFM) and ferromagnetic (FM) states [36]. The EAFM-FM between 3d transition metal adsorbed SnO monolayer are listed in Table 1. For Ti, V, Mn, Fe, and Cu adsorbed cases, the FM state is found to be more energetically stable and the values of EAFM-FM are 0.602, 3.886, 0.197, 0.666, and 0.001 eV, respectively. While for Sc, Cr, Co and Ni adsorption, the AFM configuration is the magnetic ground state with the lower energy, where the value ranges from −0.461 to −0.018 eV. In order to understand the electronic properties of TM adsorbed SnO monolayer, we study the band structures of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn adsorbed SnO monolayers. Fig. 3 shows the band structure of the most stable cases, where the red and blue solid lines represent the bands of TM-adsorbed SnO monolayers in the spin-up and spin-down channels, respectively. Meanwhile, the spin-up and spin-down states of the Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu adsorbed SnO monolayers do not overlap, which are different from the isolated SnO monolayer, suggesting that the spin polarization is induced in these systems. The band gaps of adsorbed SnO are in the range of 0.283–1.432 eV, which shows a half-semiconducting property. The Zn-adsorbed SnO preserve the
doping in SnO monolayers appears when Sc, Ti, V, Cr, Mn, Fe and Zn atoms are adsorbed. Co, Ni and Cu adsorptions induce the p-type doping in SnO monolayers. In addition, the magnetic moments of 3d TM adsorbed structures from Sc to Cu are in the range from 0.032 to 0.259 μB, while no magnetic moments appears in Zn adsorbed case. The adsorption of TM atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu) can make the SnO monolayer turn into half-semiconducting characteristics. Furthermore, Fe, Co and Ni adsorbed SnO monolayers have a perpendicular magnetic anisotropy (PMA), while Ti, V, Cr and Mn adsorbed SnO monolayers have an in-plane magnetic anisotropy (IMA). Co adsorbed SnO have the largest PMA of −0.103 mJ/m2. The results reveal that the 3d TM adsorbed SnO monolayer can be used as spintronic devices. 2. Calculation details The density functional theory (DFT) is employed to all the calculations by the Vienna ab initio Simulation Package [23]. The projectoraugmented wave (PAW) method is used to describe the interaction between electrons and ions [24]. The Perdew-Burke-Ernzerh of (PBE) form of generalized gradient approximation (GGA) is adopted to deal with the electronic exchange-correlation interaction [25–27]. The DFT + D2 method of Grimme is added to take into account the van der Waals interaction [28]. At different cutoff energy, the magnetic anisotropy energy of Co atom gradually decreases and then it reaches steady state at 450 eV. So, the cutoff energy of 500 eV can reproduce the magnetic anisotropy energy for 3d TM adsorbed monolayer SnO systems. At different k-point mesh, the magnetic anisotropy energy of Co atom appears fluctuated until it reaches stability in 6 × 6 × 1 k-point mesh. Therefore, the 7 × 7 × 1 k-point mesh is adopted throughout the calculations for the 3d TM adsorbed monolayer SnO systems [29,30]. A 18-Å thick vacuum layer is added to prevent the coupling between adjacent periodic images. The energy and force convergence criteria are 10−5 eV and 0.01 eV/Å, respectively. The Coulomb interaction (GGA + U) is introduced to describe the d electrons of TM atom [31]. U = 4.5 eV and J = 0 eV are set for the TM d orbital, where the value of Ueff = U-J is effective in the calculations. The stability and feasibility of the different adsorption configurations are evaluated by using the adsorption energy Ead = Etotal-ESnO-ETM, where Etotal represents the total energy of SnO monolayer with the adsorbed TM atoms, ESnO is the total energy of the 3 × 3 supercell for SnO monolayer, and ETM is the total energy of the isolated TM atom in its ground state. Based on the secondorder perturbation theory [32–35], the MAE is expressed as | ψ | L̂ | ψ
|2 − | ψ | L ̂ | ψ
|2
MAE ∝ ξ 2 ∑o,u o z u E − E o x u , where ψo and ψu indicate the u o occupied and unoccupied states, respectively. Eo and Eu are the eigen energies of the occupied and unoccupied states, respectively. ξ is the SOC constant. The MAE depends on the couplings between the occupied and unoccupied states through the orbital angular momentum operators L x̂ and L ẑ . The small energy separation (Eu, Eo) between the occupied and unoccupied states is responsible for the variation of MAE. In addition, MAE is obtained by MAE = E[001]-E[100], where E[001] and E[100] are the energies with the magnetization in the out-of-plane and in-plane directions, respectively [33]. The positive and negative values of MAE represent the in-plane magnetic anisotropy (IMA) and perpendicular magnetic anisotropy (PMA), respectively [34]. 3. Results and discussion The optimized atomic structure of SnO monolayer is shown in Fig. 1(a). The stable phase of SnO monolayer has a tetragonal litharge structure, where two O atoms and two Sn atoms form a pyramid structure. The lattice constant and the bond length of SneO are 3.83 and 1.805 Å, which well agree with the experimental values [10]. In the models, a single TM atom is adsorbed on a 3 × 3 × 1 SnO monolayer, where the system contains 18 Sn atoms, 18 O atoms and one TM atom. 405
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Fig. 1. (a) Top and side views for (3 × 3) supercell of SnO monolayer. Four adsorption sites, hollow (H), top (T1 and T2), and bridge (B), are marked on the SnO lattice in the 3 × 3 supercell. (b) The band structure of the pure monolayer SnO.
Fig. 2. Top and side view of the most stable structures of TM adsorbed SnO monolayer. Table 1 The adsorption energy (Ead), the bond length between TM atom and the nearest Sn(O) atom (dTM-Sn/O), the vertical height over the nearest Sn(O) atom of the top surface plane (h), charge transfer from TM atom to SnO (Δq), magnetic moment of TM adatom (μTM) and SnO layer (μSnO), the band gap (Eg) at the most stable state for all the TM atom adsorption systems and magnetic coupling (EAFM-FM) between 3d transition metal adsorbed atoms.
Sc Ti V Cr Mn Fe Co Ni Cu Zn
Ead (eV)
dTM-Sn/O (Å)
h (Å)
μTM (μB)
μSnO (μB)
Eg (eV)
−1.450 −3.194 −2.340 −0.880 −0.651 −0.982 −4.170 −2.730 −1.342 −0.567
3.559 3.298 3.297 3.359 3.477 3.200 2.781 2.771 2.934 3.457
2.342 1.919 1.921 1.951 2.201 1.775 1.928 1.544 1.338 2.163
0.839 2.696 3.753 4.777 4.738 3.500 2.209 1.086 0.176 0
−0.038 0.401 0.346 0.310 −0.043 0.155 0.300 0.414 0.410 0
0.475 0.911 0.999 1.160 1.432 0.475 0.645 0.443 0.283 2.641
406
Δq (e) 0.357 0.380 0.260 0.178 0.171 0.100 −0.012 −0.156 −0.086 0.022
EAFM-FM (eV) −0.355 0.602 3.886 −0.081 0.197 0.666 −0.461 −0.018 0.001 0
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Fig. 3. Band structure of single TM adsorbed SnO monolayer. Fermi level is set to zero. The solid red and blue lines represent the spin-up and spin-down channels, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 4. Top and side views of the charge density differences in TM adsorbed SnO monolayers. Yellow and blue regions represent the charge gain and loss, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 5. Density of states of single TM adsorbed SnO monolayers.
In order to analyze the orbital hybridization of the TM adsorbed SnO, the total density of states (TDOS) and partial density of states (PDOS) of the TM, Sn and O atoms are shown in Fig. 5. Obviously, the TM atoms induce the asymmetric distribution between the spin-up and spin-down states. The TDOS demonstrate the semiconducting characteristics of TM adsorbed SnO monolayer. The adsorption of TM atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu) can induce the magnetic moments in SnO monolayer. Therefore, the SnO monolayers in the adsorbed systems turn into magnetic semiconductor. The spin polarization appears in the Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu adsorbed systems. For Sc-adsorbed case, the Sc px orbit strongly couple with O pz orbit at the valence band maximum. For Ti-adsorption case, Ti s orbit couples with pz orbit of O and Sn in the range from −0.7 to −0.3 eV in the spin-up state. In the spin-up channel, V d orbit of couples with O py, pz orbits and Sn s, pz orbits in the range from −1.8 to −1.6 eV. The Cr s orbit couples with pz orbit of O and Sn in the range from −0.7 to −0.4 eV. In the spin-down channel, the couple between pz orbit of O and s orbit of Sn and Cr is mainly in the energy range from 0.5 to 0.8 eV. For Mn adsored case, in the spin-up channel, Mn s orbit have strong couple with pz orbit of O and s, pz and dz2 orbits of Sn in the range from −0.8 to −1.2 eV. In the spin-down state, the couple between s orbit of Mn and
band structure of pure SnO monolayer, where the band gap is 2.641 eV. The charge transfer between the TM atoms and SnO monolayers is calculated by using Bader charge analysis, as shown in Table 1. The values of Δq are 0.357e, 0.380e, 0.260e, 0.178e, 0.171e, 0.010e, −0.012e, −0.156e, −0.086e and 0.022e for Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn adsorbed SnO monolayers, where the positive values indicate the electrons transfer from TM atom to SnO monolayer. Therefore, the n-type doping in SnO monolayers appears when Sc, Ti, V, Cr, Mn, Fe and Zn atoms are adsorbed, while Co, Ni and Cu adsorptions induce the p-type doping in SnO monolayers. In order to further investigate the bonding mechanism, the charge density differences of the adsorbed systems are shown in Fig. 4. The yellow and blue regions represent the gain and loss electrons, respectively. The charge transfer mainly occurs between TM atoms and neighboring Sn (O) atoms. Moreover, Sn and TM atoms lose electrons while O atoms gain electrons in the interface. The large charge transfer has great influence on the electronic structure of SnO monolayer. Particularly, in Fig. 4, the yellow areas between Ti atom and monolayer SnO are the most obvious by comparing with other systems, indicating that the Ti adsorbed SnO generates the largest charge transfer and the orbital hybridization is the strongest. 408
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Fig. 6. The 3d orbital resolved MAE of TM atom in TM adsorbed SnO monolayers, (a) Ti, (b) V, (c) Cr, (d) Mn, (e) Fe, (f) Co and (g) Ni. (h) The layer resolved MAE of TM adsorbed SnO monolayers.
pz orbit of O and Sn is mainly in the energy ranges from −0.4 to −0.7 eV. For Fe-adsorbed SnO monolayer, in the spin-up channel, Fe s orbit couples to pz orbit of O and Sn in the range from −0.4 to −0.7 eV, while in the spin-down channel the Fe s and dz2 orbits couple to py and pz orbits of O and pz orbit of Sn in the energy ranges from −0.3 to 0.3 eV. Co, Ni and Cu adsorbed cases are similar, where TM s orbit couples with p orbits of O and Sn in the energy ranges from −0.3 to −0.3 eV. For nonmagnetic Zn adsorption, no spin polarization appears so the spin up and spin down states are perfectly symmetrical. The magnetic anisotropy of Sc, Cu and Zn atoms is not obvious, so we will focus on other atoms. Fig. 6 shows the d-orbital resolved MAE of Ti, V, Cr, Mn, Fe, Co and Ni atoms in adsorbed systems. The main contributions from Ti and Fe atoms come from the matrix element differences between dyz and dx2−y2 orbitals, which are positive. For V atom, a large positive contribution comes from the matrix element differences between dyz and dz2 orbitals. For Cr atom, the positive contribution comes from the matrix element differences between dyz and dz2 orbitals, but the matrix element differences between dxy and dx22 y orbitals give the negative contribution. By comparing with Cr atom, for Mn-adsorbed case, the matrix element differences between dyz and dz2 as well as dxy and dx2-y2 orbitals offer the opposite contribution. However, the contribution from Mn atom is larger than Cr atom. The main contributions of Co atom can be ascribed to the matrix element differences between dyz and dz2 orbitals as well as dyz and dx2-y2, which are negative. For Ni atom, the large positive contribution comes from the matrix element differences between dxy and dx2-y2 orbitals. Fig. 6(h) shows the layer-resolved MAE of SnO monolayers adsorbed by different atoms. The Fe, Co and Ni adsorbed SnO monolayers show perpendicular MAE, which are −0.0196, −0.103 and −0.0038 mJ/m2, respectively. The Ti, V, Cr and Mn adsorbed SnO monolayers have an in-plane MAE, which are in the range from 0.003 to 0.010 mJ/m2.
is nonmagnetic. The magnetic moment of SnO monolayer in the adsorbed systems changes from −0.038 to 0.414 μB, which reaches the maximum in Ni-absorbed case. The Fe, Co and Ni adsorbed SnO monolayers have the perpendicular magnetic anisotropy, while the Ti, V, Cr and Mn adsorbed SnO monolayers induce the in-plane magnetic anisotropy. The Co adsorbed SnO monolayer has the largest PMA of −0.103 mJ/m2. Our results reveal that 3d absorbed SnO monolayers have potential applications in spintronic devices. Acknowledgements This work is supported by the Key Project of the Natural Science Foundation of Tianjin City (18JCZDJC99400). References [1] H. Liu, A.T. Neal, Z. Zhu, Z. Luo, X. Xu, D. Tománek, P.D. Ye, ACS Nano 8 (2014) 4033. [2] Q.H. Wang, K. Kalantar-Zadeh, A. Kis, J.N. Coleman, M.S. Strano, Nat. Nanotechnol. 7 (2012) 699. [3] K.F. Mak, K. He, J. Shan, T.F. Heinz, Nat. Nanotechnol. 7 (2012) 494. [4] M. Modarresi, A. Kakoee, Y. Mogulkoc, M.R. Roknabadi, Comput. Mater. Sci. 101 (2015) 164. [5] N.D. Drummond, V. Zolyomi, V.I. Fal’Ko, Phys. Rev. B 85 (2012) 075423. [6] K.S. Novoselov, S.V. Morozov, T.M.G. Mohinddin, L.A. Ponomarenko, D.C. Elias, R. Yang, I.I. Barbolina, P. Blake, T.J. Booth, D. Jiang, J. Giesbers, E.W. Hill, A.K. Geim, Phys. Status Solidi 244 (2007) 4106. [7] H.F. Bai, L.C. Xu, M.Y. Di, L.Y. Hao, Z. Yang, R.P. Liu, X.Y. Li, J. Appl. Phys. 123 (2018) 95301. [8] K.J. Saji, K. Tian, M. Snure, A. Tiwari, Adv. Electron. Mater. 2 (2016) 1500453. [9] W. Zhou, N. Umezawa, Phys. Chem. Chem. Phys. 17 (2015) 17816. [10] J. Du, C. Xia, Y. Liu, X. Li, Y. Peng, S. Wei, Appl. Surf. Sci. 401 (2017) 114. [11] J.A. Caraveo-Frescas, H.N. Alshareef, Appl. Phys. Lett. 103 (2013) 222103. [12] T. Yang, J. Zhao, X. Li, X. Gao, C. Xue, Y. Wu, R. Tai, Mater. Lett. 139 (2015) 39. [13] H. Hayashi, S. Katayama, R. Huang, K. Kurushima, I. Tanaka, Phys. Status Solidi (RRL) 9 (2015) 192. [14] Y. Ogo, H. Hiramatsu, K. Nomura, H. Yanagi, T. Kamiya, M. Hirano, H. Hosono, Appl. Phys. Lett. 93 (2008) 032113. [15] J. Tao, L. Guan, Sci. Rep. 7 (2017) 44568. [16] M. Houssa, K. Iordanidou, G. Pourtois, V.V. Afanas’ ev, A. Stesmans, ECS Trans. 80 (2017) 339. [17] Y.R. Wang, S. Li, J.B. Yi, J. Phys. Chem. C 122 (2018) 4651. [18] G. Yu, M. Zhu, Y. Zheng, J. Mater. Chem. C 2 (2014) 9767. [19] Q. Pang, L. Li, C. Zhang, X.M. Wei, Y.L. Song, Mater. Chem. Phys. 160 (2015) 96. [20] J.M. Zhang, S.F. Wang, L.Y. Chen, K.W. Xu, V. Ji, Eur. Phys. J. B 76 (2010) 289. [21] Y. Wang, B. Wang, R. Huang, B. Gao, F. Kong, Q. Zhang, Phys. E Amsterdam, Neth. 63 (2014) 276. [22] W. Ju, T. Li, Q. Zhou, H. Li, X. Li, D. Ma, Comput. Mater. Sci. 150 (2018) 33. [23] G. Kresse, J. Furthmüller, Phys. Rev. B 54 (1996) 11169. [24] G. Kresse, D. Joubert, Phys. Rev. B 59 (1999) 1758. [25] J.P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 77 (1996) 3865. [26] J.J. Mortensen, Phys. Rev. B: Condens. Matter Mater. Phys. 71 (2005) 391. [27] S. Grimme, J. Comput. Chem. 27 (2006) 1787.
4. Conclusion The electronic structure and magnetic characteristics of 3d TM adsorbed SnO monolayers are investigated by first-principles calculations. After the structure optimization, the TM atoms (Sc, Ti, V, Cr, Mn, Fe, Cu and Zn) prefer to locate at T2 site on SnO monolayer. However, the Co and Ni atoms prefer to locate at T1 and B sites. The adsorption energies are in the range from −0.567 to −4.17 eV. The n-type doping in SnO monolayer appears when Sc, Ti, V, Cr, Mn, Fe and Zn atoms are adsorbed. The Co, Ni and Cu adsorptions induce the p-type doping in SnO monolayer. The Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu adsorbed SnO monolayers show the magnetism, but the Zn adsorbed SnO monolayer 409
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[33] D.S. Wang, R. Wu, A.J. Freeman, Phys. Rev. B 47 (1993) 14932. [34] P.V. Ong, N. Kioussis, P.K. Amiri, J.G. Alzate, K.L. Wang, G.P. Carman, J. Hu, R. Wu, Phys. Rev. B 89 (2014) 991. [35] P. Gambardella, S. Rusponi, M. Veronese, S.S. Dhesi, C. Grazioli, A. Dallmeyer, I. Cabria, R. Zeller, P.H. Dederichs, K. Kern, Science 300 (2003) 1130. [36] X. Cai, C. Niu, J. Wang, W. Yu, X.Y. Ren, Z. Zhu, Phys. Lett. A 381 (2017) 1236.
[28] [29] [30] [31]
T. Bucko, J. Hafner, S. Lebegue, J.G. Angyán, J. Phys. Chem. A 114 (2010) 11814. L.L. Li, H. Zhang, X.L. Cheng, Y. Miyamoto, Appl. Surf. Sci. 441 (2018) 647. H.J. Monkhorst, J.D. Pack, Phys. Rev. B 13 (1976) 5188. S.L. Dudarev, G.A. Botton, S.Y. Savrasov, C.J. Humphreys, A.P. Sutton, Phys. Rev. B 57 (1998) 1505. [32] D. Li, C. Barreteau, M.R. Castell, F. Silly, A. Smogunov, Phys. Rev. B 90 (2014) 205409.
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