The 4th International Conference on Matter and Radiation at Extremes (ICMRE 2019)

494 / 2019-03-18 21:23:43

New Hexagonal Boron Nitride Polytypes with Triple-layer Periodicity

hexagonal boron nitride, semiconductors, crystallographic defects, Density functional theory, direct band gap

Plenary track > High Pressure Physics and Materials Science

New Hexagonal Boron Nitride Polytypes with Triple-layer Periodicity
Kun Luo, Xiaohong Yuan, Zhisheng Zhao, Dongli Yu, Bo Xu, Zhongyuan Liu, Yongjun Tian, Guoying Gao, and Julong He
Center for High Pressure Science (CHiPS), State Key Laboratory of Metastable Materials Science and Technology, Yanshan Univ., Qinhuangdao 066004, China
*Email: hjl@ysu.edu.cn
Hexagonal boron nitride (h-BN or α-BN) exhibits unique electronic properties, such as a wide bandgap, low dielectric constant, high thermal conductivity, and chemical inertness. It is widely used in vacuum technology, electronics, nuclear energy, x-ray lithography, and lubrication. Despite the increased interest in h-BN, its bandgaps remain controversial given their inconsistent characterization and values. The inconsistencies in the experimentally measured h-BN bandgaps can be ascribed to the impurity of h-BN samples, which are likely a mixture of different stackings, even if they are crystalline.
To resolve this controversy, we designed eight possible BN polytypes with triple-layer periodicity. Under ambient pressure, the energies of all the proposed polytypes are between those of observed AA and Aa (h-BN) structures. Two proposed polytypes with direct bandgaps might be responsible for the direct bandgap observed in the h-BN samples. A model was proposed to show how the proposed structures might exist in the h-BN samples by analyzing the stacking characteristics and the previous experimental micrographs of h-BN samples.

Keywords: hexagonal boron nitride, semiconductors, crystallographic defects, Density functional theory, direct band gap