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BC8 Silicon (Si-III) is a narrow-gap semiconductor



Haidong Zhang, Hanyu Liu, Kaya Wei, Oleksandr Kurakevych, Zhenxian Liu, Yann Godec, Joshua B. Martin, Michael Guerrette, George S. Nolas, Timothy A. Strobel


Large-volume, phase-pure synthesis of BC8 silicon (Ia3 ̅, cI16) has enabled bulk measurements of optical, electronic and thermal properties. Unlike previous reports that conclude BC8-Si is semimetallic, we demonstrate that this phase is a direct band gap semiconductor with a very small energy gap and moderate carrier concentration and mobility at room temperature, based on far- and mid-infrared optical spectroscopy, temperature-dependent electrical conductivity, Seebeck and heat capacity measurements. Samples exhibit a plasma wavelength near 11 µm, indicating potential for infrared plasmonic applications. Thermal conductivity is reduced by one to two orders of magnitude depending on temperature as compared with the diamond cubic (DC- Si) phase. The electronic structure and dielectric properties can be reproduced by first- principles calculations with hybrid functionals after adjusting the level of exact Hartree–Fock (HF) exchange mixing. These results clarify existing limited and controversial experimental datasets and ab initio calculations.
Physical Review Letters


silicon, direct band gap semiconductor, optical spectroscopy, Seebeck coefficient


Zhang, H. , Liu, H. , Wei, K. , Kurakevych, O. , Liu, Z. , Godec, Y. , Martin, J. , Guerrette, M. , Nolas, G. and Strobel, T. (2017), BC8 Silicon (Si-III) is a narrow-gap semiconductor, Physical Review Letters, [online], (Accessed June 17, 2024)


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Created April 7, 2017, Updated October 12, 2022