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Hinge-like structure induced unusual properties of black phosphorus and new strategies to improve the thermoelectric performance.

Qin G, Yan QB, Qin Z, Yue SY, Cui HJ, Zheng QR, Su G - Sci Rep (2014)

Bottom Line: The hinge-like structure of BP brings unusual mechanical responses such as anisotropic Young's modulus and negative Poisson's ratio.By comparing the structure of BP with SnSe, a family of potential TE materials with hinge-like structure are suggested.This study not only exposes various novel properties of BP under strain, but also proposes effective strategies to seek for better TE materials.

View Article: PubMed Central - PubMed

Affiliation: College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.

ABSTRACT
We systematically investigated the geometric, electronic and thermoelectric (TE) properties of bulk black phosphorus (BP) under strain. The hinge-like structure of BP brings unusual mechanical responses such as anisotropic Young's modulus and negative Poisson's ratio. A sensitive electronic structure of BP makes it transform among metal, direct and indirect semiconductors under strain. The maximal figure of merit ZT of BP is found to be 0.72 at 800 K that could be enhanced to 0.87 by exerting an appropriate strain, revealing BP could be a potential medium-high temperature TE material. Such strain-induced enhancements of TE performance are often observed to occur at the boundary of the direct-indirect band gap transition, which can be attributed to the increase of degeneracy of energy valleys at the transition point. By comparing the structure of BP with SnSe, a family of potential TE materials with hinge-like structure are suggested. This study not only exposes various novel properties of BP under strain, but also proposes effective strategies to seek for better TE materials.

No MeSH data available.


Related in: MedlinePlus

Band gap Eg of bulk black phosphorus as function of the strain along x (a), y (b) and z (c) directions.The areas corresponding to direct, indirect and zero band gap are indicated with different colors. The insets depict the relation between the stress and strain.
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f3: Band gap Eg of bulk black phosphorus as function of the strain along x (a), y (b) and z (c) directions.The areas corresponding to direct, indirect and zero band gap are indicated with different colors. The insets depict the relation between the stress and strain.

Mentions: Figure 2(c) also shows that the scale of b is much larger than that of a, implying BP might be harder along the x direction than along the y direction. The Young's modulus along x, y and z directions can be evaluated to be 49.89 GPa, 15.11 GPa and 15.68 GPa based on the slopes of the stress-strain curves plotted in the insets of Fig. 3, revealing that BP is indeed much harder in x direction than in y or z direction. The fact that Young's modulus along the y direction is close to that along the z is unexpected, as the interactions in BP along y and z directions are dominated by strong covalent bonds and weak van der Waals forces, respectively. The negative Poisson's ratio and the anisotropic Young's modulus both indicate that bulk BP has unusual mechanical responses, which is closely related to its layered hinge-like structure.


Hinge-like structure induced unusual properties of black phosphorus and new strategies to improve the thermoelectric performance.

Qin G, Yan QB, Qin Z, Yue SY, Cui HJ, Zheng QR, Su G - Sci Rep (2014)

Band gap Eg of bulk black phosphorus as function of the strain along x (a), y (b) and z (c) directions.The areas corresponding to direct, indirect and zero band gap are indicated with different colors. The insets depict the relation between the stress and strain.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4221793&req=5

f3: Band gap Eg of bulk black phosphorus as function of the strain along x (a), y (b) and z (c) directions.The areas corresponding to direct, indirect and zero band gap are indicated with different colors. The insets depict the relation between the stress and strain.
Mentions: Figure 2(c) also shows that the scale of b is much larger than that of a, implying BP might be harder along the x direction than along the y direction. The Young's modulus along x, y and z directions can be evaluated to be 49.89 GPa, 15.11 GPa and 15.68 GPa based on the slopes of the stress-strain curves plotted in the insets of Fig. 3, revealing that BP is indeed much harder in x direction than in y or z direction. The fact that Young's modulus along the y direction is close to that along the z is unexpected, as the interactions in BP along y and z directions are dominated by strong covalent bonds and weak van der Waals forces, respectively. The negative Poisson's ratio and the anisotropic Young's modulus both indicate that bulk BP has unusual mechanical responses, which is closely related to its layered hinge-like structure.

Bottom Line: The hinge-like structure of BP brings unusual mechanical responses such as anisotropic Young's modulus and negative Poisson's ratio.By comparing the structure of BP with SnSe, a family of potential TE materials with hinge-like structure are suggested.This study not only exposes various novel properties of BP under strain, but also proposes effective strategies to seek for better TE materials.

View Article: PubMed Central - PubMed

Affiliation: College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.

ABSTRACT
We systematically investigated the geometric, electronic and thermoelectric (TE) properties of bulk black phosphorus (BP) under strain. The hinge-like structure of BP brings unusual mechanical responses such as anisotropic Young's modulus and negative Poisson's ratio. A sensitive electronic structure of BP makes it transform among metal, direct and indirect semiconductors under strain. The maximal figure of merit ZT of BP is found to be 0.72 at 800 K that could be enhanced to 0.87 by exerting an appropriate strain, revealing BP could be a potential medium-high temperature TE material. Such strain-induced enhancements of TE performance are often observed to occur at the boundary of the direct-indirect band gap transition, which can be attributed to the increase of degeneracy of energy valleys at the transition point. By comparing the structure of BP with SnSe, a family of potential TE materials with hinge-like structure are suggested. This study not only exposes various novel properties of BP under strain, but also proposes effective strategies to seek for better TE materials.

No MeSH data available.


Related in: MedlinePlus