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Negative differential resistance and bias-modulated metal-to-insulator transition in zigzag C 2 N- h 2D nanoribbon

View Article: PubMed Central - PubMed

ABSTRACT

Motivated by the fabrication of layered two-dimensional material C2N-h2D [Nat. Commun. 6, 6486 (2015)], we cut the single-layer C2N-h2D into a zigzag nanoribbon and perform a theoretical study. The results indicate that the band structure changes from semiconducting to metallic and a negative differential resistance effect occurs in the I-V curve. Interestingly, the current can be reduced to zero and this insulator-like state can be maintained as the bias increases. We find this unique property is originated from a peculiar band morphology, with only two subbands appearing around the Fermi level while others being far away. Furthermore the width and symmetry of the zigzag C2N-h2D nanoribbon can be used to tune the transport properties, such as cut-off bias and the maximum current. We also explore the electron transport property of an aperiodic model composed of two nanoribbons with different widths and obtain the same conclusion. This mechanism can be extended to other systems, e.g., hybrid BCN nanoribbons. Our discoveries suggest that the zigzag C2N-h2D nanoribbon has great potential in nanoelectronics applications.

No MeSH data available.


(a) Band structure of W = 1.0 zigzag C2N-h2D nanoribbon around the Fermi level. The left is without bias, the middle is under positive bias of 0.25 V and the right is under negative bias of −0.25 V. The two subbands near the Fermi level are shown in red (index n = 1) and blue (index n = 1′) respectively. The energy points of the four subbands near the Fermi level at the Γ-point are respectively represented by A, B, C and D. The dotted line is the Fermi level. (b) Isosurface plots of the Γ-point wave functions of n = 1 and n = 1′ subbands.
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f5: (a) Band structure of W = 1.0 zigzag C2N-h2D nanoribbon around the Fermi level. The left is without bias, the middle is under positive bias of 0.25 V and the right is under negative bias of −0.25 V. The two subbands near the Fermi level are shown in red (index n = 1) and blue (index n = 1′) respectively. The energy points of the four subbands near the Fermi level at the Γ-point are respectively represented by A, B, C and D. The dotted line is the Fermi level. (b) Isosurface plots of the Γ-point wave functions of n = 1 and n = 1′ subbands.

Mentions: In Fig. 2(a), we have pointed out that the phenomenon of NDR effect and insulator-like state also occurs in W = 1.0 zigzag C2N-h2D nanoribbon, whereas the same analysis is invalid for such models with an integer width. For example, the conduction should not be cut off at 0.5 V, so this abnormal phenomenon is worthy of further investigation. Figure 5(a) shows the band structure of the unit cell of the W = 1.0 zigzag C2N-h2D nanoribbon. It is clear that W = 1.0 model has the same band morphology as W = 1.5 model, except that the n = 1 and n = 1′ subbands are more delocalized. Figure 5(b) presents the wave functions of n = 1 and n = 1′ subbands. It is easy to see that the n = 1 subband has even parity, nevertheless, the n = 1′ subband has odd parity under σ mirror operation. Since these two subbands have opposite σ parity, an electron belonging to n = 1′ subband (blue) can not hop to n = 1 (red) subband1819, so the subbands with different colors can not couple with each other. Simultaneously, we should note that the n = 1 and n = 1′ subbands have no parity for W = 1.5 model due to its asymmetric structure as shown in Fig. 4(b), so the electrons can hop between them. This phenomenon has been reported in graphene and its related structures19. Under a low bias, there exists an overlapping between the subbands in the V+ and V− region, but the electron transport only comes from the coupling between the same color subbands. When the bias increases to 0.5 V, the n = 1 subbands in the V+ and V− region are connected in the energy window. However the n = 1 subband in the V+ region and the n = 1′ subband in the V− region have different parity, and the tunneling between these two subbands is forbidden, so that the current is reduced to zero. This state is held as the bias continues to increase. When the bias is high, we can find the insulator-like state is still derived from the presence of band gaps in the range of EAB and ECD. Consequently, the phenomenons of NDR effect and insulator-like state of W = 1.0 model originate from the peculiar band morphology too, except that the different parity between the subbands near the Fermi level prevents the electron transport and promotes the insulation-like state to happen in lower bias.


Negative differential resistance and bias-modulated metal-to-insulator transition in zigzag C 2 N- h 2D nanoribbon
(a) Band structure of W = 1.0 zigzag C2N-h2D nanoribbon around the Fermi level. The left is without bias, the middle is under positive bias of 0.25 V and the right is under negative bias of −0.25 V. The two subbands near the Fermi level are shown in red (index n = 1) and blue (index n = 1′) respectively. The energy points of the four subbands near the Fermi level at the Γ-point are respectively represented by A, B, C and D. The dotted line is the Fermi level. (b) Isosurface plots of the Γ-point wave functions of n = 1 and n = 1′ subbands.
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f5: (a) Band structure of W = 1.0 zigzag C2N-h2D nanoribbon around the Fermi level. The left is without bias, the middle is under positive bias of 0.25 V and the right is under negative bias of −0.25 V. The two subbands near the Fermi level are shown in red (index n = 1) and blue (index n = 1′) respectively. The energy points of the four subbands near the Fermi level at the Γ-point are respectively represented by A, B, C and D. The dotted line is the Fermi level. (b) Isosurface plots of the Γ-point wave functions of n = 1 and n = 1′ subbands.
Mentions: In Fig. 2(a), we have pointed out that the phenomenon of NDR effect and insulator-like state also occurs in W = 1.0 zigzag C2N-h2D nanoribbon, whereas the same analysis is invalid for such models with an integer width. For example, the conduction should not be cut off at 0.5 V, so this abnormal phenomenon is worthy of further investigation. Figure 5(a) shows the band structure of the unit cell of the W = 1.0 zigzag C2N-h2D nanoribbon. It is clear that W = 1.0 model has the same band morphology as W = 1.5 model, except that the n = 1 and n = 1′ subbands are more delocalized. Figure 5(b) presents the wave functions of n = 1 and n = 1′ subbands. It is easy to see that the n = 1 subband has even parity, nevertheless, the n = 1′ subband has odd parity under σ mirror operation. Since these two subbands have opposite σ parity, an electron belonging to n = 1′ subband (blue) can not hop to n = 1 (red) subband1819, so the subbands with different colors can not couple with each other. Simultaneously, we should note that the n = 1 and n = 1′ subbands have no parity for W = 1.5 model due to its asymmetric structure as shown in Fig. 4(b), so the electrons can hop between them. This phenomenon has been reported in graphene and its related structures19. Under a low bias, there exists an overlapping between the subbands in the V+ and V− region, but the electron transport only comes from the coupling between the same color subbands. When the bias increases to 0.5 V, the n = 1 subbands in the V+ and V− region are connected in the energy window. However the n = 1 subband in the V+ region and the n = 1′ subband in the V− region have different parity, and the tunneling between these two subbands is forbidden, so that the current is reduced to zero. This state is held as the bias continues to increase. When the bias is high, we can find the insulator-like state is still derived from the presence of band gaps in the range of EAB and ECD. Consequently, the phenomenons of NDR effect and insulator-like state of W = 1.0 model originate from the peculiar band morphology too, except that the different parity between the subbands near the Fermi level prevents the electron transport and promotes the insulation-like state to happen in lower bias.

View Article: PubMed Central - PubMed

ABSTRACT

Motivated by the fabrication of layered two-dimensional material C2N-h2D [Nat. Commun. 6, 6486 (2015)], we cut the single-layer C2N-h2D into a zigzag nanoribbon and perform a theoretical study. The results indicate that the band structure changes from semiconducting to metallic and a negative differential resistance effect occurs in the I-V curve. Interestingly, the current can be reduced to zero and this insulator-like state can be maintained as the bias increases. We find this unique property is originated from a peculiar band morphology, with only two subbands appearing around the Fermi level while others being far away. Furthermore the width and symmetry of the zigzag C2N-h2D nanoribbon can be used to tune the transport properties, such as cut-off bias and the maximum current. We also explore the electron transport property of an aperiodic model composed of two nanoribbons with different widths and obtain the same conclusion. This mechanism can be extended to other systems, e.g., hybrid BCN nanoribbons. Our discoveries suggest that the zigzag C2N-h2D nanoribbon has great potential in nanoelectronics applications.

No MeSH data available.