Tuning the Electronic and Magnetic Properties of In-Planar Graphene

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Tuning the Electronic and Magnetic Properties of In-Planar Graphene/ boron Nitride Heterostructure by Doping 3d Transition-metal Atom Xiangyue Liu, Hong Zhang, and Xin-Lu Cheng J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b06537 • Publication Date (Web): 15 Aug 2019 Downloaded from pubs.acs.org on August 28, 2019

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The Journal of Physical Chemistry

Tuning the electronic and magnetic properties of in-planar graphene/boron nitride heterostructure by doping 3d transition-metal atom Xiang-Yue Liu1,3, Hong Zhang1,2*, Xin-Lu Cheng2,3 1

2 Key

College of Physics, Sichuan University, Chengdu 610065

Laboratory of High Energy Density Physics and Technology (Ministry of Education), Sichuan University, Chengdu 610065

3

Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065

ABSTRACT The grain boundary (GB) composed of topological defects is prone to form where a merge occurred between two separate grains during the chemical vapor deposition fabrication process of in-planar 2D heterostructural nanomaterials. Here, a systematic investigation regarding the geometrical stability, electronic and magnetic properties of 3d transition metal (TM) decorated in-planar graphene/h-BN (GBN) bicrystalline heterostructure was performed. The GGA+U approach is employed as the computation method. We selected a periodical grain boundary consisted of pentagon-heptagon or pentagon-octagon topological defects as the hybrid interface between graphene and h-BN domains, and we considered Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, 9 atoms for the TM addition. GB was found to be the trapped region for all TM impurities during adsorption process. The binding strength and charge transfer of adsorbed atoms were remarkably enhanced by GB local topological defects. All 9 TM atoms adsorption introduce a transformation from non-magnetic states of pristine GBN to varying magnetization of TMGBN. Spin-splitting band structures are found in all TM adsorption systems. Multiple electronic states can be achieved, including spin-polarized half-metallic states, halfsemiconductor states, and metallic states. Both the charge injection from TM to GBN substrate and electron rearrangement between s, p, d orbitals of impurity can work on the

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rich electronic and magnetic properties. Our findings indicate that it is feasible to obtain peculiar electronic and magnetic properties by surface TM addition, which can widen the utilization of in-planar graphene/h-BN heterostructure in spin-electronic materials and nanomagnets area.

1.INTRODUCTION Two dimensional (2D) materials have received extensive research attentions on account of their potential applications, the tunable electronic, magnetic, optical, and mechanical properties, etc.1-3 Theoretical design and experimental fabrication of the heterostructures including vertical stacking and in-planar integration are able to combine the unique performances of 2D materials for desirable properties, which extend the applications of 2D materials in electron spintronics, integrated circuits, field effect tubes areas.4-8 In particular, the hybrid approaches of graphene/hexagonal boron nitride(h-BN) heterostructure are interlayer coupling and intralayer coupling. The interlayer mode can only open a relatively small energy gap, while the intralayer coupling can considerably adjust the electronic properties without destroying the monoatomic layer thickness of material.

9-11

Experimentally, it is achievable to merge graphene and h-BN into a single atomic layer to form the in-planar heterosturcture, owing to their similar atomic arrangement and least lattice constant mismatch.12-13 Ci and coworkers have realized the synthesis of in-planar graphene/h-BN heterostructure films with a wide range of compositions by means of a thermal catalytic chemical vapor deposition (CVD) method on a large area, demonstrating a variety of electronic property features as composition varies.14 Theoretical investigation of graphene/h-BN coplanar heterostructure reported by Eduardo et al. provides an accurate relevance between the electronic, thermal transport characterization and the ratio of graphene or h-BN grains concentration.15 Recently, Zhang et al. overcame the difficulty of directly growth of graphene/h-BN coplanar heterostructure by CVD method in designed way, demonstrating a new processing approach with controllable pattern.16 It is generally recognized that the formation of grain boundary (GB) is inevitable during grain adhesion of the CVD-grown 2D materials, due to the separate grain nucleation on the growth substrate.17 Furthermore, the formation of topological defects has been commonly observed


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in CVD fabrication process.18 For instance, grain boundaries consisted of five/seven-fold topological defects were formed in the process of h-BN nanosheet deposition.19 Besides, one-dimensional defect composed of pentagon-octagon rings in graphene sheet has been realized experimentally, grain boundary consisted of pentagon-octagon topological defects can lead to a local density of states distribution at Fermi level, and that the grain boundary defect act as a metallic wire.20 The topological defects in single layer graphene membrane also were found by using transmission electron microscopy investigation.21 First-principle calculations found that defects are easy to from at the interface between graphene and hBN domains rather than in the interior of grains. 22 Li et al. revealed that the presence of grain boundary composed of topological defects may has a great influence on the mechanical and thermal properties of in-planar graphene/h-BN heterostructure.23 GB functionalization is of great importance for mediating various properties of materials. 24-25 Transition-metal (TM) atoms adsorption is an effective way to modulate the magnetic and electronic properties of 2D materials.26-31 For example, Sevincli et al. comprehensively investigated the 3d TM regulated effect on the electronic and magnetic properties of graphene and graphene nanoribbons by applying density functional theory.32 The electronic and magnetic properties of single 3d TM doped graphediyne and graphyne nanosheet have been researched by He et al., adopting GGA+U method. A certain kind of TM doping 2D materials can be used as the potential electrical spintronics devices.33 In this perspective, the research of TM tuning effect on the electronic property of in-planar heterostructure is still ongoing. In this paper, our aim is to conduct a systematical investigation on the optimized configuration, electronic and magnetic properties of 3d TM adsorbed in-planar graphene/h-BN heterostructure by theoretical calculations, considering Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu impurities doping. It should be noted that the hybrid interface between graphene and h-BN is a symmetrical grain boundary containing different types of topological defects.

2. METHODS



We employed spin-polarized density functional theory (DFT) within generalized gradient approximation (GGA) for our all first principle calculations, as implemented in Vienna ab initio simulation package (VASP) code.34-35 The projector augmented-wave (PAW) pseudopotentials have been utilized to account the effect of core electrons and ions for configuration optimization and energy calculation.36 The Van der Waals PerdewBurke-Ernzerh (PBE)-D2 functional corrections was adopt to achieve accurate description of long-range interaction.37 All computed results were obtained with a plane-wave cutoff energy 450eV. The global convergence criteria for energy and interatomic force were set as 10-4eV and 0.01eV/Å respectively. The Brillouin-Zone integration was sampled by using 3×3×1 Monkhorst-Pack K-mesh during geometrical relaxation and static calculations, a denser K-mesh of 5×21×1 was set for electronic properties calculations. The supercells of GBN heterostructure were constructed by jointing separated graphene and h-BN grains with the determined orientation, graphene and h-BN grains were connected by a grain boundary composed of pentagon-heptagon defects (GBN57) or pentagon-octagon defects (GBN58) arranged in a periodical way, as displayed in Figure 1. And that GBN57 and GBN58 correspond to the armchair (AC) and zigzag (ZZ) shape hybrid interfaces respectively. Two-dimensional periodic boundary conditions were imposed and it is necessary to enlarge the grain to eliminate the interactions between GBs. A vacuum layer of 30Å was used. It is imperative to consider the electron correlation effect for the magnetic property of 3d TM elements on account of TM localized d orbital. Therefore, the onsite coulomb interaction DFT+U method was employed to conduct the calculation of adsorption geometry, electronic and magnetic properties of TM-GBN heterostructure systems.38 Here we consider a reasonable moderate value of U=2.5eV, and the exchange parameter J was set to zero as default.39 To evaluate the stability of adorption geometry, we defined the adsorption energy Ead for TM adatoms adsorbed on GBN sheet: Ead= ETM-GBN-ETM- EGBN-sheet Where ETM-GBN is the total spin-polarized energy of TM adsorbed heterostructure systems, ETM is the energy of a free TM atom, and EGBN-sheet is the energy of heterostructure sheet. To have a better understanding of the charge redistribution in TM-GBN systems, the charge density difference ∆ρ is calculated by:


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∆ρ= ρ(TM-GBN)-ρ(TM)- ρ(GBN-sheet) Where ρ(TM-GBN), ρ(TM), ρ(GBN-sheet) are the total charge density of TM adsorbed heterostructure systems, a free TM atom and the heterostructure sheet correspondingly. The total electron transfer between TM atom and GBN sheet is calculated by Bader charge analysis method.40 Since the valence electrons of adsorbed TM atom are distributed in 4s, 3d, 4p orbitals, we obtained the electron distribution of 4s, 3d, 4p states of TM atom by partial density of states (PDOS) to determine the interobital electron transfer. In addition, we took into account the ferromagnetic (FM) and the antiferromagnetic (AFM) spin configuration to attain magnetic behavior ground state by adsorbed two same TM atoms on GBN57/GBN58 sheet.

3. RESULTS AND DISCUSSION 3.1. Pristine graphene/h-BN in-planar heterostructural bicrystal Before adsorbed TM atoms on heterostructure sheet, the selected pristine coplanar GBN bicrystalline heterostructures have been optimized, as presented in Figure 1(a) and (b). Figure 1(c) and (d) present the least stable supercells in our calculation, in which GBN57 supercell contains 36C, 18B, 18N while the GBN58 contains 36C, 16B, 16N. The lattice constants of GBN57 are a=29.45Å, b=6.60Å, and GBN58 are a=28.41Å, b=4.96Å respectively. What’s more, we have calculated the band structure and the total density of states of pristine GBN57 and GBN58, Figure 2 indicate that nonmagnetic semiconductor state with a direct band gap of 0.23eV realized for GBN57 and the GBN58 exhibits metallic state. The electronic property of GBN heterostructure varies with the topological defect composition of hybrid grain boundary between graphene and h-BN domains.

3.2. TM adsorbed GBN configurations and energy calculation In present study, nine 3d TM adatoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) were considered to adsorb on the selected in-planar GBN heterostructures. The single TM atom



introduction to the given GBN57 and GBN58 supercells is equivalent to a 1.39% and 1.47% doping concentration. According to the symmetry of GBN57/GBN58 heterostructure, several different initial adsorption sites are chosen as shown in Figure 1(c) and (d) including hollow sites (H), top sites (T), and bridge sites (B). The optimized configurations of TM-GBN systems are displayed in Figure 3 and Figure 4, indicating that all TM atoms prefer to absorb on the top of hybrid grain boundary containing topological defects instead of graphene or h-BN grains. In addition, all of the TM atoms tend to absorb on the hollow sites of heptagon hybrid ring for GBN57 heterostructure except for Cu-GBN57 case, while all of the TM atoms have an inclination to absorb on the top of pentagon hybrid ring for GBN58 heterostructure except for Cr, Ni, Cu-GBN58 cases. Specifically, for TM-GBN57, the hollow site off the middle of heptagon ring are preferred by TM (Sc-Ni) atoms energetically while Cu atom tends to locate at bridge site deviated from B2 site. For TMGBN58, the H2 site in the central of pentagon carbon ring is the optimized adsorption sites for Sc, V, Mn, Fe, Co adatoms while Ti is off the H1 site in the middle of hybrid pentagon ring. Cr, Ni, Cu are apt to adsorb at the bridge sites jointed two pentagon rings. The introduction of all TM adatoms to GBN sheet makes an obviously distortion in the inplanar configuration to some extent from the top and side views, the substrate atoms below TM are displaced from their initial positions. Table 1 offers the calculated energy and structural parameters of adsorption geometry in detail, containing the adsorption energy, bond length between TM atoms and the nearest C atoms of GBN and the vertical distance between adatom and nanosheet. All the negative values of adsorption energy indicate the chemisorption characteristic for TM-GBN adsorption. It can be seen that Ni-GBN57 and Ni-GBN58 cases shows lowest binding energies, in which they are supposed to be the most stable structures among other TM-GBN systems. Cr-GBN57 and Ti-GBN58 have the weakest binding interaction. For GBN57, the bond lengths between Fe, Ni, Cu, and the nearest carbon atom are close to the standard bond length (1.95Å), which is in agreement with their larger adsorption energy. While for GBN58, the near-expected bond lengths of Fe-C, Co-C, Ni-C correspond to the strong interaction between TM adatom and GBN substrate. We also calculated the ratio of adsorption energy and experimental cohesive energy of bulk TM to determine the growth mode of TM on GBN substrate, as summarized in Table 1.41 By definition, the larger Ead/Ec value, the 2D layer growth mode of metal is favorable. On the contrary, metal is more likely to appear 3D cluster growth morphology under a small Ead/Ec value. Sc, Fe, Ni, Cu prefer a 2D layer growth mode while Ti, V, Cr, Mn, Co are prone to 3D island growth mode on GBN57 substrate. TM adatoms may display the 2D layer formation pattern on GBN58 substrate except for Ti, V cases.


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3.3. Electronic and magnetic properties of TM-GBN heterostructure In this section we systematically investigate the electronic and magnetic properties of all the TM-GBN systems on basis of the optimized structures. Table 2 summarized the calculation parameters, including magnetic moment, the electron transfer between orbitals, charge transfer, and the magnetic energy difference. We can clearly see that all the 3d TM (Sc-Cu) doping magnetize the heterostructure substrate, in which a minor fractional total magnetic moment -0.002μB and the TM basin magnetic moment -0.001μB are found in NiGBN57 case especially. Chemisorption of Ti, Cr, Mn atoms in GBN57 and Cr, Mn in GBN58 induce a larger magnetic moment. To elucidate the stability of the spin-polarization state of TM adsorbed systems, we also calculated the increase in energy from spin-polarization which defined as the energy difference between magnetic and nonmagnetic states, the results are consistent with the total magnetic moment of TM decorated heterostructure. For instance, the 5.45μB and the 5.67μB magnetic moments are attained in Mn-GBN57 and MnGBN58 that match their strong spin polarization with the largest ∆EM respectively. In order to gain a better understanding of magnetism, we checked the magnetic behavior of ground state of TM-GBN systems and calculated the energy difference between the ferromagnetic and antiferromagnetic states by doping two same TM atoms to the calculated supercell shown in Figure.1(c) and (d), as summarized in Table 3. It can be found that for GBN57, Sc, V, Fe, Cu adsorbed systems display FM states whereas the doping of Ti, Cr, Mn, Co, Ni makes GBN57 appear AFM states; for GBN58, Sc, Fe, Co, Cu doping systems exhibit FM behaviors and the others display AFM behaviors. The measurement of magnetic ground state is closely correlated with the spintronic application of GBN, however, no available experimental data has been reported by now. Concerning the coupling between TM and GBN substrate, we also calculated the charge transfer between dopants and GBN by means of Bader charge analysis, as displayed in

Table

2.

The

sequence

of

charge

transfer

of

TM-GBN57

is

Sc>Ti>V>Fe>Cr>Mn>Co>Ni>Cu, while Sc>V>Ti>Cr>Mn>Fe>Co>Ni>Co for TMGBN58. The bonding situation is analyzed by the spin-polarized charge density differences, presented by Figure.5 and Figure. 6, the yellow and blue regions represent the gain and



depletion of electrons. It is apparent that electron accumulated around TM and nearest atoms of GBN, and there is a redistribution of electron density around the adsorption zone. The considerable electron transfer from TM to GBN manifests the formation of a covalent bonding. The spin-polarized band structures of TM-GBN57 and TM-GBN58 are presented in Figure.7. and Figure. 8. The adsorption of Sc-Cu impurities on GBN57/GBN58 results in spin splitting of band structure in various degree, the multiple electronic properties are obtained in doping systems. We summarized the electronic characteristics of TM-GBN57 and TM-GBN58 from band structures as followed: (i) V-GBN57, Cu-GBN57, Ni-GBN57 behave as spin-polarized half-semiconductor. The spin polarization of Cu-GBN57 are 100% at HOMO level and LUMO level, where the VBM and CBM belong to different spin channels. Ni doping induces minor spin polarization in GBN57 on account of its small fraction magnetic moment, comparing with pristine GBN57, the band gap of Ni doping system is narrowed down. For the V, Ni decorating GBN57 , the band structures are semiconducting with direct band gaps of 0.27, 0.16eV for majority spin channels and indirect band gaps of 0.32, 0.13eV for minority spin channels respectively. Cu-GBN57 has an indirect band gap of 0.58eV for spin-up state and an indirect band gap of 0.51eV for spin-down state. (ii) When GBN57 adsorbed Sc, Ti, Cr, Mn, the heterostructure systems realized semiconductor-metal transition. Those adsorbed systems are spin-polarized metals. What’s more, V, Cr, Mn, Fe, Co, Ni, Cu adsorbed GBN58 heterostructure systems maintain their metallic state. (iii) Fe-GBN57, Co-GBN57, Sc-GBN58, Ti-GBN58 exhibit half-metallic states. For Fe-GBN57, its band structure is semiconducting with an indirect band gap of 0.29eV for spin-up states whereas it is metallic for spin-down states; For Co-GBN57, its band structure is metallic for spin-up states whereas it is semiconducting for spin-down states with an indirect band gap of 0.54eV. The spin polarization of half-metallic heterostructures are up to 100% at Fermi level. Moreover, Sc-GBN58, Ti-GBN58 also exhibit half-metallic states. For both Sc-GBN58 and Ti-GBN58 cases, their band structures are metallic for spin-up states whereas there are semiconducting characters for spin-down states with indirect band gap of 0.22, 0.36eV. Fe-GBN57, Co-GBN57, Sc-GBN58, Ti-GBN58 adsorption systems are potential candidates for spintronic device because they exhibit metallic behaviors in one spin channel but semiconductor in another channel. On the whole,


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more abundant electronic properties can be realized in GBN57 substrate by TM regulation, compared with TM-GBN58 systems. The density of states including TDOS and PDOS are consistent with the band structures, displayed in Figure.9 and Figure. 10. PDOS illuminate the coupling between TM atoms and GBN57 sheet, in which the 3d orbital of TM are segmented into E1(dxz, dyz), E2(dxy, dx2-y2) and A1(dz2). The proportions of 4s and 3d states are calculated by PDOS. TM orbitals have the coupling effect with nearest neighbor states around the Fermi level in all adsorbed systems. On account of electrons redistribution, the density of states in different spin channels undergo spin-splitting near Fermi level. The coupling electronic properties and magnetic characteristic of TM-GBN have been discussed below. (A) TM-GBN57 systems: The magnetic moment of TM impurity for all Sc-Cu doped GBN57 cases are all decreased by 0.04, 0.14, 3.48, 3.19, 0.50, 3.50, 2.79, 1.999, 0.58μB compared with those of their free-standing state. As displayed in TDOS and PDOS, for Sc, Ti-GBN57 cases, E1 state of TM locates around the Fermi level in majority spin channel, and p state of the nearest carbon atom locates around the Fermi level in both majority and minority spin states. The electron occupation of 3d orbital of Sc shows a small increment so that the magnetic moment of Sc adsorbed on GBN57 is very close to that of its freestanding state. Both the 4s and 3d orbitals of Ti lose electrons, and empty 4p orbital shows 0.18e occupation. The deduction of magnetic moment is mainly resulted from the decrease of Ti 3d orbital unpaired electrons. The spin-up and spin-down VBMs are mainly located by V 3d orbital (E1, E2) and C p states; V s state and C s state correspondingly. Whereas E2 state of V dominates the spin-up CBM and V s, C p states locate in the spin-up CBM. For Cr-GBN57, A1 state of Cr locates around Fermi level in both majority and minority channels. Occupation of Cr A1, E2 states and the p state of nearest Carbon makes a contribution to both the spin-up and spin-down states around Fermi level. The 4s orbital and 3d orbital of Cr lose electrons that resulting in the less-half filled d shell and the decrease of the unpaired electrons in 3d orbital, so that there is a considerable decrease of magnetic momentum. The occupation of Mn s orbital and C p orbital contributes to the spin-up state around Fermi level while Mn E2, A1 states occupy the spin-down Fermi level region. The VBM and CBM in both spin-up and spin-down channels of Fe-GBN57 are



attributed to the occupation of Fe E1 state coupling to C p state; Fe s state coupling to C p state respectively. For Co-GBN57, the coupling in the energy range of -2.25 to -1.5eV is derived from between the p state of carbon atom and E1, E2, A1 states in both majority and minority spin channel. For Ni-GBN57, there is a weak spin- polarization with ∆ EM=10meV, showing a small degree of spin splitting. The 3d orbital of the free-standing Ni atom has 8 intrinsic electrons, Bader analysis shows that 1.75 electrons transfer from its 4s orbital to 3d orbital due to the coupling between Ni atom and heterostructure sheet. The near-zero magnetic moment of Ni-GBN57 is on account of the near full-filled shell of 3d orbital of Ni. For Cu-GBN57, the VBM in minority spin states is derived from s state of Cu and p state of nearest C, CBM is mainly derived from s state of Cu. Here, the Fe-GBN57 case is taken to illuminate the correlation of charge transfer and the magnetic properties in detail. For spin-up state, the Fermi level passes through the conduction band because of the electron transfer from 3d TM to GBN sheet. The Fe d orbital with s, E1, E2 states couples to p orbital of nearest carbon atom in the energy range of 0.2-0.35eV; Fe d orbital with E1, E2 couples to carbon p in -2.35 to -2.15eV energy range. For spin-down state, there are considerable overlaps for Fe E1, E2, A1 and C p in 1.8 to -1.36eV, 1.6 to 2.39eV energy regions. Fe atom transfers 0.61eV to GBN57 while total electron of Fe 3d shell is increased by 0.52e and the Fe 4p shows 0.24e electron occupation, which is stemmed from electron injection from Fe 4s to Fe 3d and 4p orbitals. The coupling between Fe and GBN57 sheet shows that charge interchange from GBN57 to Fe atom, and the electron redistribution between orbitals. There are 6 intrinsic electrons in 3d orbital of the Fe atom that has larger half-filled d shell, most of electron of 4s orbital move to the 3d and 4p orbitals based on Bader analysis. The magnetic momentum of Fe atom is less than it of its freestanding state on account of the depletion of 3d orbital unpaired electrons. (B) TM-GBN58 systems: The magnetic moment for Sc-Cu cases are reduced by 0.29, 1.75, 3.96, 1.60, 0.28, 2.90, 1.07, 1.99, 0.91μB related to those of their free atom states. We take the similar approach discussed above to analyze the relationship between TMGBN interaction, TM-substrate electron exchange, electron redistribution between orbitals and magnetic characteristic in TM- GBN58. The 4s orbital of TM for all the adsorbed


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systems always draw electrons out and empty 4p orbital always get electrons. The PDOS shows that for Ti-GBN58, E2 state of Ti dominates the majority spin states around Fermi Level, while s state of Sc dominate the majority spin state around Fermi level. Both the 3d orbitals of Sc and Ti lose electrons, which leading to the minor reduction in unpaired electrons, showing the decrease of magnetic moment. The coupling between A1 state of V and p state of nearest carbon is achieved in the ranges of -1.75 to -1.6eV and -1.33 to 0.95eV. For Cr adatom, the spin-up states are mainly contributed by the occupation of the Cr E1, E2, A1 states, while the p state of carbon and the s, d (E1, E2, A1) orbitals of Cr make a contribution to spin-down states. Analogous to Cr-GBN57 case, the magnetism reduction of Cr-GBN58 compared to its free-standing state is ascribed to the decrease of unpaired electrons in d orbital. In Mn doping, the states above Fermi level are mainly occupied by Mn E2 state in majority states and there is a certain coupling between Mn E1, E2 states and carbon p state in the spin-up region of -0.5 to -0.37eV. E2, A1 states of Fe and p state of carbon locate around the Fermi level in spin-up channel. Fe E1, E2 states couple with C p state in -0.72 to -0.60eV energy window. In both spin-down channels, the Co E1, E2 and A1 states strongly couple with p state of carbon in the range of -0.81 to 0.52eV; E2, A1couple with s of carbon around -1.45 to -1.3eV. For Ni-GBN58, the states around Fermi level are contributed by the occupation of spin-up E1, E2 orbitals of Ni. The s, p orbitals of Cu and p orbital of carbon dominate the spin-down region around Fermi level states. To study the effect of GB topological defect ring on in-planar h-BN with TM doping, we calculated the TM adsorbed pure armchair interface graphene/h-BN (GBNAC) and zigzag interface graphene/h-BN (GBNZZ) cases as comparison, the calculated parameters are displayed in Table 4. Here we compared GBNAC to GBN57; and GBNZZ compares with GBN58. From the comparison, it has been found that the binding strength of most TMGBNAC and TM-GBNZZ cases are very small. Specifically, small negative values of Ead for Ti-GBNAC and Sc-GBNZZ (about -0.24eV and -0.22eV) demonstrates that the adsorption processes are exothermic and TM are physical bonded with substrate. Remarkably, the GB topological defects are conducive to the combination of TM and heterostructure. What’s more, the charge transfer between GBNAC and Fe is only 0.25e, while, 0.61e was



transferred to GBN57 sheet for Fe adsorption. There is 0.53e charge transfer when Mn binding with GBN58 substrate, but only 0.07e be transferred to GBNZZ substrate for Mn adsorption. The other adsorption cases of GBNAC and GBNZZ are also undergoing a distinct decrease of charge transfer, relative to GB containing topological defects. Thereby, local defective states have a significant effect to promote the interaction between TM and GBN substrate.

4. CONCLUSION In summary, the first principle calculation has been carried out to investigate the optimized configurations, electronic and magnetic properties of in-planar graphene/h-BN bi-crystal heterostructure functionalized by 3d transition metal atom. We both calculated the adsorption situation that the interface between graphene and h-BN domains is matched by pentagon-heptagon or pentagon-octagon topological defects. Conclusions include the following: (1) The most favorable adsorption configurations are that TM atoms are prefer to occupy the hollow sites of the hybrid grain boundary except for Cu-GBN57 and Cr, Ni, CuGBN58 cases, and the TM atoms are chemically bonded with the heterostructure sheet. (2) Hybrid GB containing topological defects has a significant effect to facilitate binding strength and charge transfer of TM impurity atoms. (3) The adsorption of TM can effectively tune the magnetic properties of heterostructure. TM (Sc-Cu) adatoms induce spin-polarization and magnetism to some extent for both pentagon-heptagon heterostructure (GBN57) and pentagon-octagon heterostructure (GBN58). Especially both Mn adsorbed GBN57 and GBN58 have the largest magnetic momentum of 5.45μB, 5.67μB with antiferromagnetic spin alignment. Of all TM adatoms considered, the magnetic behaviors of ground states of TM-GBN57 systems are identical to that of TM-GBN58 systems, but V, Co adsorption can make GBN57 and GBN58 substrates present the opposite magnetic ground states.


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(4) Electronic properties of GBN can be obviously modified by 3d TM doping. For GBN57: Fe, Co adsorption systems exhibit half-metallic states; the spin-selected halfsemiconductor states are achieved in the V, Cu, Ni adsorption systems; the other cases realized the semiconductor-metal transition. For GBN58: Sc, Ti adsorption systems exhibit half-metallic states; V-Cu adsorption systems maintain their metallic states with spinsplitting. Analysis of magnetic moment, density of state and charge distribution for each adsorption systems provides evidence that the electron redistribution within TM orbitals and charge transfer between impurity and substrate can modulate the magnetic and electronic properties. The above results indicate that the transition metal atom adsorbed in-planar graphene/hBN bicrystalline heterostructure can be applied in the field of nano-electronics and spintronic device.

AUTHOR INFORMATION Corresponding Author 

E-mail: [email protected].

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT H.Z. acknowledges ﬁnancial support from the National Key R&D Program of China (Grant 2017YFA0303600), X.C. acknowledges ﬁnancial support from the National Natural Science Foundation of China (Grant No. 11774248).



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Figure 1 Optimized configurations of GBN57 (a) and GBN58 (b) heterostructures, the orange dash lines indicates the least supercells, (c), (d)supercells used in our calculations, the red dots represent the possible initial adsorption sites before optimization.



Figure 2 (a) The band structure and (b) TDOS of GBN57,(c) the band structure and (d) TDOS of GBN58, Fermi level is set to zero.


Page 18 of 41

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Figure 3 Diagrams of the configuration of TM-GBN57 systems after optimization from top and side view (a)-(f). (a)-(e) TM (Sc-Ni) atoms are apt to stay at the top of hybrid heptagon ring and tend to stray away from the central point of heptagon defects. (f) Cu prefer to locate near B2 site.

Figure 4 Diagrams of the configuration of TM-GBN58 systems after optimization from top and side view (a)-(d). (a) Sc, V, Mn, Fe, Co tend to absorb at the H2 sites of GBN58 sheet.



(b) Ti tends to locate near H1 site. (c) Cr, Ni deviate from the B1 site to different degrees. (d) B1 site is favored by Cu dopant.

Figure 5 Spin-polarized charge density differences for TM-GBN57. The yellow and blue regions donate the gain and loss of electron respectively.

Figure 6 Spin-polarized charge density differences for TM-GBN58. The yellow and blue regions donate the gain and loss of electron.


Page 20 of 41

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Figure 7 Calculated electronic band structures of TM-GBN57, Fermi level is set to zero. The spin-up and spin-down states are represented by blue and red solid lines respectively.



Figure 8 Calculated electronic band structures of TM-GBN58, Fermi level is set to zero. The spin-up and spin-down states are represented by blue and red solid lines respectively


Page 22 of 41

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Figure 9 Electronic density of states for TM-GBN57, Fermi level is set to zero. The upper, middle and lower channels represent the TDOS, the PDOS of TM and the PDOS of nearest carbon atoms of GBN sheet respectively.



Figure 10 Electronic density of states for TM-GBN58, Fermi level is set to zero. The upper, middle and lower channel represent the TDOS, the PDOS of TM and the PDOS of nearest carbon atoms of GBN sheet respectively.


Page 24 of 41

Page 25 of 41 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1 The adsorption energy (Ead) for the TM adsorbed on GBN57 and GBN58 systems at the most stable adsorption sites, the bond length between TM atom and the nearest C atom (DTM-C), the vertical distance of adatom to upper nearest C atom. The ratio (Ead/Ec) of adsorption energy and cohesive energies per atom of bulk TM. Ead/eV

DTM-C/Å

HTM-C/Å

Ead/Ec

TM-GBN57

TM-GBN58

TM-GBN57

TM-GBN58

TM-GBN57

TM-GBN58

TM-GBN57

TM-GBN58

Sc

-2.02

-2.18

1.98

2.16

2.47

2.51

0.52

0.56

Ti

-1.62

-1.17

1.87

2.17

2.37

2.38

0.33

0.24

V

-2.05

-2.09

1.77

1.88

2.26

2.22

0.39

0.39

Cr

-1.21

-2.03

1.92

2.09

2.28

2.25

0.30

0.50

Mn

-1.25

-2.24

2.01

2.07

2.34

2.33

0.43

0.77

Fe

-2.49

-2.89

1.49

1.86

1.99

2.09

0.58

0.68

Co

-1.84

-3.02

1.69

1.70

2.26

1.99

0.42

0.69

Ni

-2.52

-3.05

1.83

1.76

2.03

1.94

0.57

0.69

Cu

-2.44

-2.31

1.94

1.98

2.01

2.12

0.70

0.66



Page 26 of 41

Table 2 Total magnetic moment Mtot(μB) of the TM-GBN systems, the magnetic moment MTM(μB) of TM dopants in the optimized configuration, the magnetic moment MTMfreestanding(μ0) of TM atoms in free-standing state, the valence electronic configurations for a free-standing TM atom (TM-freestanding 4s/3d), the valence electronic configurations for the TM atoms absorbed on graphene/ hexagonal boron nitride inplanar heterostructure systems (TM-freestanding 4s/3d/4p), charge transfer from TM adatom to GBN sheet. Energy difference  EM (meV) between nonmagnetic state and magnetic state in the same supercell. TM-freestanding


TM-heterostructure

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Mtot(μB)

MTM(μB)

MTM-freestanding(μ0)

4s/3d

4s/3d/4p

Te

∆EM

Sc-GBN57

2.26

0.96

1

2/1

1.22/1.02/0.09

0.83

463

Ti-GBN57

3.13

1.86

2

2/2

0.17/1.95/0.18

0.78

1291

V-GBN57

-2.12

-1.52

5

2/3

0.15/3.03/0.10

0.76

874

Cr-GBN57

-3.08

-2.81

6

1/5

0.17/4.66/0.09

0.57

1716

Mn-GBN57

5.45

4.50

5

2/5

0.22/5.23/0.12

0.42

3514

Fe-GBN57

0.94

0.50

4

2/6

0.26/6.52/0.24

0.61

738

Co-GBN57

-0.89

-0.21

3

2/7

0.32/7.46/0.13

0.36

260

Ni-GBN57

-0.00

-0.00

2

2/8

0.25/8.81/0.11

0.24

10

Cu-GBN57

-1.04

-0.44

1

1/10

0.43/9.48/0.12

0.18

369

Sc-GBN58

1.64

0.71

1

2/1

1.26/0.92/0.09

0.77

225

Ti-GBN58

1.31

0.25

2

2/2

1.16/1.84/0.06

0.65

535

V-GBN58

-1.66

-1.06

5

2/3

0.19/3.21/0.14

0.72

1520

Cr-GBN58

-5.32

-4.40

6

1/5

0.20/4.14/0.08

0.55

3166

Mn-GBN57

5.67

4.72

5

2/5

0.21/5.12/0.12

0.53

3348

Fe-GBN58

1.33

1.10

4

2/6

0.23/6.49/0.25

0.49

544

Co-GBN58

2.33

1.93

3

2/7

0.33/7.56/0.34

0.47

828

Ni-GBN58

0.12

0.01

2

2/8

0.38/8.76/0.19

0.27

11

Cu-GBN58

-0.33

-0.09

1

1/10

0.34/9..41/0.11

0.18

28



Page 28 of 41

Table 3 Energy difference in ferromagnetic(FM) state and antiferromagnetic (AFM) state (meV) when adsorbed two same TM adatoms on heterostruture sheet, and the magnetic ground state (MS). MS

∆EFM-AFM/meV Two TM adatoms adsorption

TM-GBN57

TM-GBN58

TM-GBN57

TM-GBN58

Sc

-76

-144

FM

FM

Ti

9

902

AFM

AFM

V

-1003

1385

FM

AFM

Cr

2418

1856

AFM

AFM

Mn

2316

236

AFM

AFM

Fe

-278

-62

FM

FM

Co

28

-38

AFM

FM

Ni

2

39

AFM

AFM

Cu

73

48

FM

FM

Table 4 The adsorption energy (Ead) for the TM adsorbed on GBNAC and GBNZZ at the most stable adsorption sites, and the charge transfer from TM adatom to GBNAC and GBNZZ substrate. Ead/eV

Te


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TM-GBNAC

TM-GBNZZ

TM- GBNAC

TM- GBNZZ

Sc

0.19

-0.22

0.75

0.74

Ti

-0.24

0.54

0.71

0.72

V

0.53

0.29

0.53

0.52

Cr

0.89

3.34

0.32

0.45

Mn

3.29

0.67

0.50

0.07

Fe

0.42

0.34

0.25

0.33

Co

0.61

0.68

0.30

0.13

Ni

0.07

-0.04

0.23

0.27

Cu

0.55

0.69

0.11

-0.02

Abstract Graphic




Page 30 of 41

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Abstract graphic 186x202mm (300 x 300 DPI)



Figure 1 Optimized configurations of GBN57 (a) and GBN58 (b) heterostructures, the orange dash lines indicates the least supercells, (c), (d)supercells used in our calculations, the red dots represent the possible initial adsorption sites before optimization. 720x215mm (300 x 300 DPI)


Page 32 of 41

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Figure 2 (a) The band structure and (b) TDOS of GBN57,(c) the band structure and (d) TDOS of GBN58, Fermi level is set to zero. 518x397mm (300 x 300 DPI)



Figure 3 Diagrams of the configuration of TM-GBN57 systems after optimization from top and side view (a)(f). (a)-(e) TM (Sc-Ni) atoms are apt to stay at the top of hybrid heptagon ring and tend to stray away from the central point of heptagon defects. (f) Cu prefer to locate near B2 site. 253x181mm (300 x 300 DPI)


Page 34 of 41

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Figure 4 Diagrams of the configuration of TM-GBN58 systems after optimization from top and side view (a)(d). (a) Sc, V, Mn, Fe, Co tend to absorb at the H2 sites of GBN58 sheet. (b) Ti tends to locate near H1 site. (c) Cr, Ni deviate from the B1 site to different degrees. (d) B1 site is favored by Cu dopant. 245x100mm (300 x 300 DPI)



Figure 5 Spin-polarized charge density differences for TM-GBN57. The yellow and blue regions donate the gain and loss of electron respectively. 1006x323mm (150 x 150 DPI)


Page 36 of 41

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Figure 6 Spin-polarized charge density differences for TM-GBN58. The yellow and blue regions donate the gain and loss of electron. 1007x242mm (300 x 300 DPI)



Figure 7 Calculated electronic band structures of TM-GBN57, Fermi level is set to zero. The spin-up and spindown states are represented by blue and red solid lines respectively. 785x630mm (150 x 150 DPI)


Page 38 of 41

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Figure 8 Electronic density of states for TM-GBN57, Fermi level is set to zero. The upper, middle and lower channels represent the TDOS, the PDOS of TM and the PDOS of nearest carbon atoms of GBN sheet respectively. 799x628mm (150 x 150 DPI)



Figure 9 Calculated electronic band structures of TM-GBN58, Fermi level is set to zero. The spin-up and spindown states are represented by blue and red solid lines respectively 711x611mm (150 x 150 DPI)


Page 40 of 41

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Figure 10 Electronic density of states for TM-GBN58, Fermi level is set to zero. The upper, middle and lower channel represent the TDOS, the PDOS of TM and the PDOS of nearest carbon atoms of GBN sheet respectively. 794x616mm (150 x 150 DPI)


Tuning the Electronic and Magnetic Properties of In-Planar Graphene

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