Electronic Properties of Edge-Hydrogenated Phosphorene

Subscriber access provided by The Libraries of the | University of North Dakota

Article

Electronic Properties of Edge-Hydrogenated Phosphorene Nanoribbons: A First-Principles Study Weifeng Li, Gang Zhang, and Yong-Wei Zhang J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/jp506996a • Publication Date (Web): 02 Sep 2014 Downloaded from http://pubs.acs.org on September 4, 2014

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry C is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 17

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

The Journal of Physical Chemistry

Electronic Properties of Edge-Hydrogenated Phosphorene Nanoribbons: A First-Principles Study

Weifeng Li, Gang Zhang*, Yong-Wei Zhang† Institute of High Performance Computing, A*STAR, Singapore 138632.

Abstract We perform first-principles calculations to study the electronic structures and edge properties of phosphorene nanoribbons (PNRs) with and without edge hydrogenation. In contrast to the direct band gap semiconducting characteristic observed in phosphorene sheet, bare armchair PNRs are semiconductors with an indirect band gap; while bare zigzag PNRs are conductors. Through edge hydrogenation, both armchair and zigzag PNRs become semiconductors with a direct band gap. Interestingly, the electronic properties of edge-hydrogenated PNRs are independent of their edge orientation, which are in contrast to that of bare PNRs, which show a significant edge orientation-dependence. In addition, our edge energy and stress analysis show that hydrogenated PNRs have an extremely low edge energy and also low edge stress, indicating that they are stable both energetically and mechanically. The present work indicates that hydrogenated PNRs, which are of a moderate band gap energy, a direct band gap and high edge stability, are promising candidates for applications in electronic and optoelectronic devices. Keywords: black phosphorus, edge engineering; two-dimensional materials; band structure

* †

[email protected], +65-64191583 [email protected], +65-64191478

1 ACS Paragon Plus Environment


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

1. Introduction Two-dimensional (2D) materials have attracted great interest recently due to their various intriguing electronic properties arising from the dimension and size reduction and resulting quantum effects1. To date, some 2D crystals, such as graphene, hexagonal boron nitride (hBN) and transition metal disulphide (TMD) have been studied extensively2-6. In addition, their one-dimensional (1D) forms, such as nanoribbons, have also drawn considerable interest both from fundamental point of view to understand their intrinsic properties and also from practical point of view to explore their applications in electronic, spintronic and photonic devices. In general, 1D nanoribbons offer different electronic properties from their 2D sheet counterparts. For example, graphene sheet has a band structure following a linear dispersion relation at the Fermi energy level (EF) in the reciprocal space, forming the so-called semimetal structure4. However, graphene nanoribbon can be either metallic or semiconducting, depending on the crystallographic direction and ribbon width7-9. Another well-studied 2D material is molybdenum disulfide (MoS2) monolayer, which is a semiconductor with a direct band gap of 1.9 eV10. However, MoS2 nanoribbons can be metallic or semiconducting, depending on the crystallographic directions of ribbon edges11-14. Very recently, field effect transistors based on micrometer-sized flakes of semiconducting black phosphorus was fabricated15. This new member of 2D crystals, in the form of few-layer or monolayer (the monolayer form is often called phosphorene), possesses attractive characteristics, such as a moderate band gap between that of graphene and MoS2 16-19, making this material particularly potentially useful for various applications, ranging from infrared optoelectronics to quantum transport. Although the electronic band structures of monolayer and multilayer phosphorus sheets have been studied, for example, the effects of layer number16, stacking order17 and strain18, the electronic band structures of phosphorus


Page 2 of 17

Page 3 of 17

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


nanoribbons are still not well-documented. Compared to its 2D counterpart, the band structure of nanoribbon is usually more complex, thus can offer distinct and often intriguing properties and applications. Hence, it is of both fundamental interest and technological importance to systematically investigate the electronic properties of nanoribbons derived from phosphorus. In addition, edge chemical functionalization, such as hydrogenation or fluorination, can often bring about new electronic properties and edge stability of 2D nanoribbons11, 20. A very recent work even shows that edge hydrogenation can effectively tune the topological edge states of Bi nanoribbon21. An interesting question is: How does such edge chemical functionalization affect the electronic properties and stability of phosphorene ribbons? Using density functional theory (DFT) calculations, here, we studied the structural and electronic properties of phosphorene nanoribbons (PNRs). In contrast to the direct band gap of the phosphorene sheet, bare armchair (ac) PNRs possess an indirect band gap; while bare zigzag (zz) PNRs exhibit a metallic characteristic. Through edge hydrogenation, PNRs become a direct band gap semiconductor with considerably high edge stability. In addition, the direct band gap characteristic of these hydrogenated PNRs is independent of their edge orientation, armchair or zigzag. This is in contrast to that of bare PNRs, which show a significant edge orientation-dependence. The present work suggests that edge hydrogenated PNRs, which are of a moderate gap energy, a direct band gap, and high edge stability, are promising for developing novel electronic and photonic devices.

2. Computing Methods and Model The structural optimization and band structure calculations were performed using DFT in the generalized gradient approximation (GGA)22 with the Perdew–Burke–Ernzerhof (PBE) exchange correlation functional, as implemented in the Vienna ab initio simulation package



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

(VASP)23-24. Following the conventional notation, we use the number of dimer lines across the nanoribbon width M (or N) to denote the width of armchair (or zigzag) PNRs. Depending on the parity of M or N, the two edges can be in different symmetries. For ac-PNRs, an even value of M results in two symmetric edges, and the corresponding PNRs are denoted as s-ac; while an odd number results in two asymmetric edges and the corresponding PNRs are denoted as a-ac. For zz-PNRs, when N is even, the PNR is symmetric from top view but antisymmetrical from side view, and for simplicity, the corresponding PNRs are denoted as s-zz; when N is odd, the PNR is asymmetric from top view but symmetric from side view, and for simplicity, the corresponding PNRs are denoted as a-zz. In addition, these different PNR edges can also be hydrogenated. Here, a suffix H is added to the above notations to denote hydrogenated PNRs. For example, s-zz+H denotes a hydrogenated symmetrical zigzag PNR. In the present study, we consider four different types of PNRs, that is, M = 13, 14 and N = 10, 11. The width of these PNRs is in the range from 2.05 to 2.36 nm. Some selected configurations of these PNRs are shown in Fig. 1 and Fig. 2. For example, an s-ac PNR with M=13 and an a-ac+H PNR with M=14 are shown in Fig. 1(a) and (d), respectively; and a s-zz PNR with N=10 and an a-zz+H PNR with N=11 are shown Fig. 2(a) and (d), respectively. For the directions perpendicular to the ribbon length direction (as indicated by the arrows in Fig. 1(a), 1(d) and Fig. 2(a), 2(d)), a vacuum space of at least 20 Å was kept to avoid mirror interactions. Atomic relaxation was performed until the change of total energy was less than 0.01 meV and all the forces on each atom are less than 0.01eV/Å, which are sufficient to obtain relaxed structures. A k-point sampling of 1×1×10 was used for the structure relaxation, while a denser mesh of 1×1×50 was used to calculate energies, density of states (DOS) and band structures.

3. Results and Discussion


Page 4 of 17

Page 5 of 17

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


3.1 Edge-Targeted Hydrogenation Before hydrogenation, each edge P atom has two bonded neighbors and also one dangling bond. Structural distortions at PNR edges are clearly visible as illustrated in Fig. 1(a) and Fig. 2(a). Hydrogenation of the edge P atoms effectively reduces the distortions as shown in Fig. 1(d) and Fig. 2(d). The formation of P-H covalent bond is exothermic, which can be quantitatively described by its formation energy: E = (E

− E

− m × E )/m

(1)

where E

, E

and E are the potential energies of ribbon+H complex, ribbon with bare edges and single H atom, respectively. For ac-PNRs, m=4 as there are four hydrogen binding sites in one primitive cell. For zz-PNRs, m=2. It is found that symmetric or asymmetric edges do not change the formation energy, E . Our calculations show that E is -2.86 eV/H for ac-PNR and -2.96 eV/H for zz-PNR. Besides two edges, PNRs also have interior portion. Previous studies have shown that the top and bottom surfaces of 2D materials like graphene are able to attract hydrogen adatoms25-26, and thus they may compete for edge hydrogenation. Hence we need to examine the adsorption of hydrogen on the surfaces of phosphorene sheet. We consider a 2D phosphorene model containing 4×3 primitive cells (48 phosphate atoms) with one binding hydrogen atom. A 15×15×1 k-point mesh is used to optimize the structure. A fully relaxed hydrogen is found to form a bond with one phosphate atom with binding energy of only -1.25 eV/H, which is much weaker than the edge binding energy of -2.86 or -2.96 eV/H. This difference clearly demonstrates that the PNR edges are the most energetically favorable binding sites for hydrogen atoms.

3.2 Electronic Structure of PNRs



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

We first examined the band structure of ac-PNRs without edge hydrogenation. As shown in Fig. 1(b) and 1(e), compared to the phosphorene sheet with a direct band gap of 0.892 eV, both s-ac and a-ac PNRs become an indirect band gap semiconductor by shifting the conduction band minimum (CBM) by about one third towards the X point in the reciprocal lattice space. While this transition is independent of the edge symmetry, the values of band gap are slightly different: 0.436 eV for the s-ac PNR and 0.450 eV for the a-ac PNR. The Fermi energy level EF lies slightly above the valence band maximum (VBM) by only 0.086 and 0.091 eV for the s-ac PNR and a-ac PNR, respectively. This indirect band gap characteristic in bare ac-PNRs may result in their inapplicability for many optical devices. Fig.1(c) and 1(f) show the electronic band structures for the s-ac+H and a-ac+H PNRs, respectively. It is interesting to observe that edge hydrogenation can cause significant changes in the electronic band structure of ac-PNRs. As shown in Fig. 1(c) and 1(f), both the CBM and VBM are located at the Γ point, indicating a transition from indirect to direct band gap for both s-ac and a-ac PNRs, arising from edge hydrogenation. For edge hydrogenated ac-PNRs, the band gaps are 0.952 and 0.950 eV for s-ac and a-ac PNRs, respectively, therefore comparable to that of phosphorene sheet. Fig. 2(b) and 2(e) show the electronic band structures of the s-zz and a-zz PNRs, respectively. It is seen that two half-filled bands cross the Fermi energy level EF for the two bare zz-PNRs, indicating their metallic character, which is different from the indirect band gap character observed in bare ac-PNRs.

Hence, for bare PNRs, their electronic band

structures are strongly orientation-dependent, similar to that for graphene and MoS2 nanoribbons, which also exhibit an orientation-dependent electronic band structure. Fig.2(c) and 2(f) show the electronic band structures for the s-zz+H and a-zz+H PNRs, respectively. It is seen that edge hydrogenation on these PNRs has led to remarkable changes in the electronic band structures. Upon edge hydrogenation, there is a metallic to


Page 6 of 17

Page 7 of 17

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


semiconducting transition for both zz PNRs. Importantly, these hydrogenated zz PNRs are direct band gap semiconductors with even larger band gaps of 1.373 and 1.309 eV, respectively, for the s-zz+H and a-zz+H PNRs.

3.3 Frontier Orbital Analysis In order to understand the origin of the changes in the band structures, we have analyzed the compositions of frontier orbitals. As the edge symmetry (symmetric or asymmetric) does not affect the band structure significantly, in the following discussion, we only focus on the symmetric PNRs (s-ac PNR and s-zz PNR) without and with hydrogenation. Fig. 3(a) shows the charge density isosurface and a cross-section of the CB (the two doubly-degenerated empty bands above the EF) of the s-ac PNR. The two lobed-shape electron clouds (characterized by p orbitals) from adjacent edge P atoms overlap efficiently, which corresponds to the inward-curvature of the bands. For the s-zz PNR, the two half-filled bands at EF are also characterized by p orbitals of edge P atoms, and efficient overlapping of the adjacent p electron clouds forms the electron conducting channel as illustrated in Fig. 3(b). From the projected density of states (PDOS) analysis (Fig. 3(c) and 3(d)), frontier orbitals mainly originate from the pz orbitals, with a weak contribution from the py orbitals. For the edge hydrogenated PNRs, the DOS projected on P and H atoms, respectively, are shown in Fig. 3(e) (for the s-ac+H PNR) and 3(f) (for the s-zz+H PNR). It is clear that, for both CBM and VBM, the compositions are mainly contributed from the P atoms, while there is negligible contribution from H atoms. More detailed projections on the p orbitals of P atoms (Fig. 3(g) and 3(h)) indicated that, the pz orbitals still play a major role in the VBM and CBM for both s-ac+H PNR and s-zz+H PNR. Moreover, there is an important change in the CB arising from the edge hydrogenation: the dominance of pz orbitals is slightly weakened, and CBM shifts upwards, leading to the increase in the band gap energy.



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

Page 8 of 17

3.4 Energy Stability of PNRs It is important to examine the stability of PNRs with and without edge hydrogenation. Generally, the edge stability can be described by the edge energy, which accounts for the energy cost to form an edge27. Here we define the edge energy (E ) as: E = (E

− mμ − nμ )⁄2L

(2)

where E

is the total energy of phosphorene nanoribbon, μ is the chemical potential of P atom from phosphorene monolayer, μ is the chemical potential of H atom from H2 molecule, m and n are the numbers of P and H atoms in the nanoribbon, and L is the cell length of the nanoribbon. According to this definition, a smaller value of Eedge indicates a more chemically stable ribbon structure. The calculated values of E for the four bare PNRs and also four edge-hydrogenated PNRs are summarized in Fig. 4(a). In general, it is known that cutting 2D phosphorene into nanoribbons leaves highly active and unstable edge states. The values of E for the s-ac and a-ac PNRs are 0.265 or 0.264 eV/Å, respectively; while that for s-zz and a-zz PNRs are 0.276 or 0.284 eV/Å, respectively. Hence, the zz-PNRs are only slightly less stable than the ac-PNRs. This is in contrast to the MoS2 ribbon, where the zigzag edge is significantly more stable than the armchair edge11. Overall, these higher energy values indicate that bare PNRs are much less chemically stable than their phosphorene sheet. It is seen from Fig. 4(a) that hydrogen treatment has saturated the dangling bonds and leads to more stable edges in PNRs. The values of E for the s-ac+H PNR and a-ac+H PNRs are only 0.008 and 0.007eV/Å, respectively. The values of E for the s-zz+H and azz+H PNRs are 0.066 and 0.074 eV/Å, respectively, which are slightly higher than their armchair counterparts, but are still considerably lower than their bare edge counterparts. The


Page 9 of 17

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


low edge energy values for edge-hydrogenated PNRs suggest that they can be as nearly stable as their phosphorene sheet.

3.5 Mechanical Stability of PNRs Another fundamental thermodynamic quantity for a ribbon structure is its edge stress27, which has been used successfully to investigate mechanical stability of graphene nanoribbon. Fig. 4(b) shows the edge stress of four phosphorene ribbons before and after edge hydrogenation. We find that the armchair edges have edge stress with value of -0.058 and 0.065 eV/Å (the negative sign denotes the compressive stress) for s-ac and a-ac PNR, respectively. The zigzag edges have significantly larger edge stress with value of -0.384 and 0.418 eV/Å for s-zz and a-zz PNR, respectively. The compressive stresses indicate that the edges of PNRs have a tendency to stretch, which is potentially able to induce edge twisting and warping instability. After edge hydrogenation, the armchair edge stresses change from compression to tension (positive value); meanwhile the strengths are also reduced to 0.039 (sac+H PNR) and 0.024 eV/Å (a-ac+H PNR), which can improve the mechanical stability of the ribbons. This is in line with graphene nanoribbons where edge hydrogenation also effectively reduces the edge stress27. Similarly, edge hydrogenation also reduces the zigzag edge stresses to -0.364 (s-zz+H PNR) and -0.397 eV/Å (a-zz+H PNR). By comparison, we see that the edge-hydrogenated ac-PNRs are not only energetically, but also mechanically more stable than their zigzag counterparts. The different properties of bare PNRs observed here may offer various opportunities for the development of different electronic devices. However, the coexistence of both metallic and semiconducting PNRs is a major obstacle for many practical applications in electronics or photonics, which often require a uniform electronic property. In addition, their chemically active edges may also be problematic for practical applications. In the present work, we have



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

shown that edge-hydrogenation not only uniformly turns various kinds of bare PNRs into direct band gap semiconductors, but also effectively stabilizes the edges of PNRs. Hence, edge-hydrogenated PNRs are a promising nanomaterial for high-performance electronic and photonic applications.

4. Conclusion To conclude, we have systematically studied the electronic properties and edge stability of PNRs with and without hydrogenation. Although bare-edged PNRs offer diverse electronic properties, they are potentially chemically unstable due to its relatively high edge energy. Hydrogen treatment is able to saturate the edge dangling bonds and thus effectively stabilize PNRs. In fact, we have shown that the edge-hydrogenated PNRs have extremely low edge energy and also low edge stress, indicating that they are both energetically and mechanically stable. Importantly, all the hydrogenated PNRs are direct band gap semiconductors with moderate band gap energies. These novel electronic properties, together with their high edge stability, suggest that the edge-hydrogenated PNRs are promising candidates for applications in electronic and photonic devices.

Acknowledgements This work was supported by the A*STAR Computational Resource Centre through the use of its high performance computing facilities.


Page 10 of 17

Page 11 of 17

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


Figure 1. (a) Schematic of symmetric armchair (s-ac) PNR, M is the ribbon width index number. Since hydrogenation has little effect on central part of PNR structure, the edgehydrogenated s-ac PNR is not shown. (b) Band structures of bare s-ac PNR. (c) Band structures of s-ac PNR with edge-hydrogenation. (d) Schematic of asymmetric armchair (a-ac) PNR with hydrogenation. For brevity, the bare a-ac PNR is not shown. (e) Band structures of a-ac PNR. (f) Band structures of a-ac PNR with edge-hydrogenation. The green arrows in (a) and (d) indicate the ribbon length direction. The blue arrows in (b) and (e) indicate the indirect band-gap. In (a) and (d), P and H atoms are represented in purple and white, respectively.



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

Figure 2. (a) Schematic of symmetric zigzag (s-zz) PNR, N is the ribbon width index number. Since hydrogenation has little effect on central part of PNR structure, the edge-hydrogenated s-zz PNR is not shown. (b) Band structures of bare s-zz PNR. (c) Band structures of s-zz PNR with edge-hydrogenation. (d) Schematic of asymmetric zigzag (a-zz) PNR with edgehydrogenation. For brevity, the bare a-zz PNR is not shown. (e) Band structures of a-zz PNR. (f) Band structures of a-zz PNR with edge-hydrogenation. In (a) and (d), P and H atoms are represented in purple and white, respectively, and the green arrows indicate the ribbon length direction.


Page 12 of 17

Page 13 of 17

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


Figure 3. Charge density isosurface (0.002|e|/bohr3) and cross section of (a) CBM of bare s-ac PNR and (b) half-filled bands at EF of bare s-zz PNR. The dash lines indicate the positions of the cross section. (c) PDOS of p orbitals of P atom of bare edged s-ac PNR. (d) PDOS of p orbitals of P atom of bare edged s-zz PNR. (e) PDOS of P and H atoms of s-ac PNR with edge-hydrogenation. (f) PDOS of P and H atoms of s-zz PNR with edge-hydrogenation. (g) PDOS of p orbitals of P atom of s-ac PNR with edge-hydrogenation. (h) PDOS of p orbitals of P atom of s-zz PNR with edge-hydrogenation.



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

Figure 4. The edge energies (a) and edge stresses (b) of the four PNRs with and without edge hydrogenation.


Page 14 of 17

Page 15 of 17

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


Reference: 1. Grigorieva, A. G. I., Van Der Waals Heterostructures. Nature 2013, 499, 419-425. 2. Geim, A. K.; Novoselov, K. S., The Rise of Graphene. Nat. Mater. 2007, 6, 183-191. 3. Najmaei, S.; Liu, Z.; Zhou, W.; Zou, X.; Shi, G.; Lei, S.; Yakobson, B. I.; Idrobo, J.-C.; Ajayan, P. M.; Lou, J., Vapour Phase Growth and Grain Boundary Structure of Molybdenum Disulphide Atomic Layers. Nat. Mater. 2013, 12, 754-759. 4. Neto, A. C.; Guinea, F.; Peres, N.; Novoselov, K. S.; Geim, A. K., The Electronic Properties of Graphene. Rev. Mod. Phys. 2009, 81, 109-162. 5. Balandin, A. A., Thermal Properties of Graphene and Nanostructured Carbon Materials. Nat. Mater. 2011, 10, 569-581. 6. Polini, M.; Guinea, F.; Lewenstein, M.; Manoharan, H. C.; Pellegrini, V., Artificial Honeycomb Lattices for Electrons, Atoms and Photons. Nat Nano 2013, 8, 625-633. 7. Son, Y.-W.; Cohen, M. L.; Louie, S. G., Energy Gaps in Graphene Nanoribbons. Phys. Rev. Lett. 2006, 97, 216803. 8. Barone, V.; Hod, O.; Scuseria, G. E., Electronic Structure and Stability of Semiconducting Graphene Nanoribbons. Nano Lett. 2006, 6, 2748-2754. 9. Yan, Q.; Huang, B.; Yu, J.; Zheng, F.; Zang, J.; Wu, J.; Gu, B.-L.; Liu, F.; Duan, W., Intrinsic Current−Voltage CharacterisAcs of Graphene Nanoribbon Transistors and Eﬀect of Edge Doping. Nano Lett. 2007, 7, 1469-1473. 10. Mak, K. F.; Lee, C.; Hone, J.; Shan, J.; Heinz, T. F., Atomically Thin Mos2: A New Direct-Gap Semiconductor. Phys. Rev. Lett. 2010, 105, 136805. 11. Pan, H.; Zhang, Y.-W., Edge-Dependent Structural, Electronic and Magnetic Properties of Mos2 Nanoribbons. J. Mater. Chem. 2012, 22, 7280-7290. 12. Li, Y.; Zhou, Z.; Zhang, S.; Chen, Z., Mos2 Nanoribbons: High Stability and Unusual Electronic and Magnetic Properties. J. Am. Chem. Soc. 2008, 130, 16739-16744. 13. Cai, Y.; Zhang, G.; Zhang, Y.-W., Polarity-Reversed Robust Carrier Mobility in Monolayer Mos2 Nanoribbons. J. Am. Chem. Soc. 2014, 136, 6269-6275. 14. Li, W.; Zhang, G.; Guo, M.; Zhang, Y.-W., Strain-Tunable Electronic and Transport Properties of Mos2 Nanotubes. Nano Res. 2014, 7, 518-527. 15. Li, L.; Yu, Y.; Ye, G. J.; Ge, Q.; Ou, X.; Wu, H.; Feng, D.; Chen, X. H.; Zhang, Y., Black Phosphorus Field-Effect Transistors. Nat Nano 2014, 9, 372-377. 16. Liu, H.; Neal, A. T.; Zhu, Z.; Luo, Z.; Xu, X.; Tománek, D.; Ye, P. D., Phosphorene: An Unexplored 2d Semiconductor with a High Hole Mobility. ACS Nano 2014, 8, 4033-4041. 17. Dai, J.; Zeng, X. C., Bilayer Phosphorene: Effect of Stacking Order on Bandgap and Its Potential Applications in Thin-Film Solar Cells. J. Phys. Chem. Lett. 2014, 5, 1289-1293. 18. Fei, R.; Yang, L., Strain-Engineering the Anisotropic Electrical Conductance of Few-Layer Black Phosphorus. Nano Lett. 2014, 14, 2884-2889. 19. Qiao, J.; Kong, X.; Hu, Z.-X.; Yang, F.; Ji, W., High-Mobility Transport Anisotropy and Linear Dichroism in Few-Layer Black Phosphorus. Nature communications 2014, 5, 4475. 20. Cai, Y.; Bai, Z.; Pan, H.; Feng, Y. P.; Yakobson, B. I.; Zhang, Y.-W., Constructing Metallic Nanoroads on a Mos2 Monolayer Via Hydrogenation. Nanoscale 2014, 6, 1691-1697. 21. Wang, Z. F.; Chen, L.; Liu, F., Tuning Topological Edge States of Bi(111) Bilayer Film by Edge Adsorption. Nano Lett. 2014, 14, 2879-2883. 22. Perdew, J. P.; Chevary, J. A.; Vosko, S. H.; Jackson, K. A.; Pederson, M. R.; Singh, D. J.; Fiolhais, C., Atoms, Molecules, Solids, and Surfaces: Applications of the Generalized Gradient Approximation for Exchange and Correlation. Phys. Rev. B 1992, 46, 6671-6687. 23. Kresse, G.; Furthmuller, J., Efficiency of Ab-Initio Total Energy Calculations for Metals and Semiconductors Using a Plane-Wave Basis Set. Comput. Mater. Sci. 1996, 6, 15-50. 24. Kresse, G.; Furthmuller, J., Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169-11186. 15 ACS Paragon Plus Environment


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

25. Yu, D.; Liu, F., Synthesis of Carbon Nanotubes by Rolling up Patterned Graphene Nanoribbons Using Selective Atomic Adsorption. Nano Lett. 2007, 7, 3046-3050. 26. Li, W.; Zhao, M.; He, T.; Song, C.; Lin, X.; Liu, X.; Xia, Y.; Mei, L., Concentration Dependent Magnetism Induced by Hydrogen Adsorption on Graphene and Single Walled Carbon Nanotubes. J. Magn. Magn. Mater. 2010, 322, 838-843. 27. Huang, B.; Liu, M.; Su, N.; Wu, J.; Duan, W.; Gu, B.-l.; Liu, F., Quantum Manifestations of Graphene Edge Stress and Edge Instability: A First-Principles Study. Phys. Rev. Lett. 2009, 102, 166404.


Page 16 of 17

Page 17 of 17

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 of Contents graphic


Electronic Properties of Edge-Hydrogenated Phosphorene

Recommend Documents