Cui Jingjing, Peng Qiong, Zhou Jian, Sun Zhimei
School of Materials Science and Engineering, Beihang University, Beijing 100191, People's Republic of China. Center for Integrated Computational Materials Engineering, International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191, People's Republic of China.
Nanotechnology. 2019 Aug 23;30(34):345205. doi: 10.1088/1361-6528/ab1f22. Epub 2019 May 3.
The feature of an indirect bandgap of most semiconducting transition metal carbides (MXenes) limits their applications in optoelectronics devices. By means of density functional theory (DFT) calculations, we have found that the transition of indirect-direct bandgap can occur in MXenes with different functional groups and structures under appropriate biaxial strain. The controllable bandgap of MXenes stems from the fact that the electronic states near the Fermi level have different responses to tensile strain. The stress-strain curves and phonon spectra suggest that semiconducting MXenes can maintain their stability during a wide range of strains. Moreover, the optical dielectric constants of MXenes are red-shifted and enhanced continuously via applying tensile strains. The tunable electronic and optical properties of semiconducting MXenes make them promising candidates for the design of optoelectronic devices.
大多数半导体过渡金属碳化物（MXenes）的间接带隙特性限制了它们在光电器件中的应用。通过密度泛函理论（DFT）计算，我们发现，在适当的双轴应变下，具有不同官能团和结构的MXenes中可发生间接-直接带隙转变。MXenes的可控带隙源于费米能级附近的电子态对拉伸应变有不同的响应。应力-应变曲线和声子谱表明，半导体MXenes在很宽的应变范围内都能保持其稳定性。此外，通过施加拉伸应变，MXenes的光学介电常数会不断发生红移并增强。半导体MXenes的可调控电子和光学性质使其成为光电器件设计的有前途的候选材料。
