Electronic structure, carrier mobility and device properties for mixed-edge phagraphene nanoribbon by hetero-atom doping

doi:10.1016/j.orgel.2017.09.025

Organic Electronics

Volume 51, December 2017, Pages 277-286

https://doi.org/10.1016/j.orgel.2017.09.025 Get rights and content

Highlights

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Electronic and transport properties of a doped phagraphene nanoribbon are studied.
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Such a ribbon hold rich and fully tunable electronic structures.
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Doping can regulate carrier mobility and device properties significantly.

Abstract

Phagraphene, a new carbon allotrope, was proposed recently. We here select a mixed-edge phagraphene ribbon to study B-, N-, and BN-doping effects respectively on the geometric stability, electronic structure, carrier mobility, and device property. Calculations show that the energetic and thermal stability for these ribbons are very high. With different doping types and doping sites, the bandgap size of a ribbon may be nearly unchanged, increased, or decreased as compared with the intrinsic ribbon, and even become a metal, thus presenting fully tunable electronic structures. For this, the charge transfer shifting edge bands and the new formed hybridized bands due to doping play a crucial role. More interestingly, doping at different positions can regulate the carrier mobility of ribbon, and the difference of two orders of magnitude for hole mobility can be generated by BN-doping. In addition, the study on device property shows that there is a prominent negative differential resistance characteristics occurring in a BN-doped ribbon device. These findings are meaningful for understanding the doping effects on electronic properties of phagraphene nanoribbons.

Graphical abstract

Introduction

Graphene, one of the most extensively studied two-dimensional (2D) materials in recent years, consists of carbon atoms by hexagonal symmetric lattice, resulting in its band structure like Dirac cones with linear dispersion near the Fermi level [1]. And graphene presents many novel properties, such as quantum Hall effect [2], [3], ultrahigh thermal conductivity and super-flexibility [4]. In particular, its carrier mobility can reach 10⁵ cm² V⁻¹ s⁻¹ orders of magnitude at room temperature [5]. This make it possible becoming a promising alternative for developing the next-generation high-performance functional devices. Meanwhile, the successful fabrication of graphene also encourage researchers to explore other 2D materials. So far, beyond graphene, numerous other 2D materials have also been proposed or fabricated, such as silicene [6], h-BN [7], [8], [9] and borophene [10], MoS2 [11], and phosphorene [12]. Especially for carbon-based 2D atomic crystals, such as graphane [13], graphdiyne [14], [15], and penta-graphene [16], [17], all of which demonstrate novel and exceptional electronic features.

Recently, a new carbon allotrope with a planer structure composed of 5-6-7 carbon rings, phagraphene, was predicted to be stable [18]. This 2D material made out of sp²-hybrid carbon atoms possesses a high atomic packing density, allowing that its physical properties could be comparable with graphene and its geometrical structure is energetically more favorable than other carbon allotropes proposed previously [18], [19]. Intrinsic phagraphene is a semimetal with the band structure like distorted Dirac cones near the Fermi level [19]. By using a molecular dynamics simulations, Pereira et al. [20]reported that the thermal conductivity of phagraphene is anisotropic, and the predicted electronic properties suggest that phagraphene could be a better candidate than graphene in future carbon-based thermoelectric devices. Unfortunately, the lack of band gap in phagraphene will be an obstacle for realistic applications in future electronic devices. Similar to graphene, the very simple and feasible strategy to solve this issue is cutting phagraphene sheet into quasi-one dimensional narrowed nanoribbons, phagraphene nanoribbons (PHAGNRs). The electronic properties of PHAGNRs would be ruled by atomic geometries along edges. For example, Liu et al. [21]reported that hydrogen-terminated PHAGNRs with mixture of armchair and zigzag shaped edges are semiconducting, and hydrogen-terminated pure zigzag PHAGNRs behave as a metal.

In previous works, in order to tune functional properties of graphene or derived graphene nanoribbons adequately for realizing applications in more fields, one of the usually used routines is doping them with foreign atoms [22], [23], [24], [25], [26], [27], [28], [29], [30] or to constitute the hetero-structure [31], [32], [33], [34]. Among these doping schemes, B or/and N atom doping is more preferred. This is because the chemical properties of N and B atoms are similar to C atoms, and thus forming a quite strong covalent B (N)-C bond, similar to the C single bond C bond. The geometric deformation for graphene induced by the N or/and B doping is also very small. They modulate electronic properties of graphene only by introducing extra carries and changing energy band structures, therefore, the N or B atom or BN molecule doping has become typical substitutional doping in graphene. So far, B- or/and N-doped graphene have been synthesized in many experiments [28], [29], [30], [35], [36], including a large area h-BNC film being fabricated, which presents different physical properties from h-BN film and graphene sheet [36]. Particularly, with the continuous enhancement of the experimental technology, for example, single carbon atom can be knocked off by focused electron beam of 1 Å diameter [37], and an atomic force microscope (AFM)has been applied to achieve various single-atom manipulations [38], the atom-doping trends to be more ordered, and even to be feasible to realize site-selective substitutional doping with atomic precision [39]. However, there are no reports about doping for phagraphene to modulate electronic properties until now, including B or/and N doping.

In this present work, based on the first-principles method, we study the geometrical stability, electronic structure, carrier mobility, and device property for a mixed-edge phagraphene ribbon with B-, N-, and BN- doping, respectively. Calculations show that the energetic and thermal stability for these ribbons is very high, and they hold diverse electronic structures upon the dopant types and doping sites. For this, the charge transfer moving edge bands and new formed hybridized bands due to doping play a crucial role. In particular, doping can regulate the carrier mobility of ribbons, and the difference of two orders of magnitude for hole mobility can be generated by BN-doping. In addition, constructed devices based on these ribbons exhibit there is a prominent negative differential resistance characteristics occurring in a BN-doped ribbon device.

Section snippets

Structure Models and Theoretical Method

The schematic diagram for the atomic structure of 2D phagraphene is demonstrated in Fig. 1(a), and when tailoring it along x direction, we can obtain one kind of typical nanoribbon, MPHAGNR, whose each edge is a mixture structure of alternating armchair and zigzag segments. A MPHAGNR contains two classes of carbon chains across its width direction, both pure zigzag-type carbon chains and mixture-type carbon chains consisting of alternating armchair and zigzag segments. Thus, the width of a

Structure stability

After full relaxations, the geometrical deformations occurring in the area near a dopant are extremely small, and all atoms, including carbon atoms and a dopant, are all stay in the same plane. To assess structural stability, we firstly calculate the binding energy of all doped ribbons to demonstrate their energetic stability, and the binding energy is defined as: $E_{B E} = (E_{D N R} - n_{C} E_{C} - n_{H} E_{H} - n_{B} E_{B} - n_{N} E_{N}) / (n_{C} + n_{H} + n_{B} + n_{N}),$ where E_DNR is the total energy of one unit cell for doped ribbons. E_C, E_H, E_B, and E_N

Conclusion

Using first-principles calculations based on the density functional theory, we study the structural stability, electronic structure, carrier mobility, and device property of the mixed-edge phagraphene nanoribbon (MPHAGNR) with B-, N-, and BN-doping, respectively. The calculated binding energy suggests that these structures are energetically stable. Born-Oppenheimer molecular dynamics (BOMD) simulations demonstrate that the thermal stability of all systems is also higher. In particular, our

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant Nos. 61371065 and 51604042), the Hunan Provincial Natural Science Foundation of China (Grant Nos. 12JJ3004, 2015JJ3002, 2015JJ2009, 2015JJ2013), and Project supported by the scientific research project of the Education Department of Hunan Province (Grant No. 16C0029).

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Electronic structure, carrier mobility and device properties for mixed-edge phagraphene nanoribbon by hetero-atom doping

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Structure Models and Theoretical Method

Structure stability

Conclusion

Acknowledgments

Carbon

Carbon

Comput. Mater. Sci.

Org. Electron

Carbon

Org. Electron.

Org. Electron.

Carbon

Org. Electron.

Org. Electron.

Org. Electron.

Graphene: an emerging electronic material

Adv. Mater. (Deerfield Beach, Fla.)

Experimental observation of the quantum Hall effect and Berry's phase in graphene

Nature

Unconventional quantum Hall effect and Berry's phase of 2π in bilayer graphene

Nat. Phys.

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Adv. Mater.

Ultrahigh electron mobility in suspended graphene

Solid State Commun.

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Phys. Rev. Lett.

The two-dimensional phase of boron nitride: few-atomic-layer sheets and suspended membranes

Appl. Phys. Lett.

Structural and magneto-electronic properties and electric field-mediated effects for transition metal-terminated zigzag h-BN nanoribbons

Phys. Chem. Chem. Phys.

BN nanoflake quantum-dot arrays: structural stability, and electronic and half-metallic properties

Phys. Chem. Chem. Phys. PCCP

Synthesis of borophenes: anisotropic, two-dimensional boron polymorphs

Sci. (New York, N.Y.)

Electronic structure, spin-orbit coupling, and interlayer interaction in bulk MoS2 and WS2

Phys. Rev. B

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Phys. Rev. Lett.

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Sci. (New York, N.Y.)

Electronic structure and carrier mobility in graphdiyne sheet and nanoribbons: theoretical predictions

ACS Nano

Penta-graphene: a new carbon allotrope

Proc. Natl. Acad. Sci. U. S. A.

Electronic structure and magnetic properties of penta-graphene nanoribbons

Phys. Chem. Chem. Phys. PCCP

Electronic structure, spin-orbit coupling, and interlayer interaction in bulk MoS₂ and WS₂