Bandaru Sateesh, Saranya Govindarajan, English Niall J, Yam Chiyung, Chen Mingyang
Beijing Computational Science Research Center, Beijing, 100084, China.
School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland.
Sci Rep. 2018 Jul 4;8(1):10144. doi: 10.1038/s41598-018-28522-7.
First-principles calculations were carried out to understand how anionic isovalent-atom doping affects the electronic structures and optical properties of α-MoO. The effects of the sulphur and selenium doping at the three unique oxygen sites (O, O, and O) of α-MoO were examined. We found that the valence p orbitals of Sulphur/Selenium dopant atoms give rise to impurity bands above the valence band maximum in the band structure of α-MoO. The number of impurity bands in the doped material depends on the specific doping sites and the local chemical environment of the dopants in MoO. The impurity bands give rise to the enhanced optical absorptions of the S- and Se-doped MoO in the visible and infrared regions. At low local doping concentration, the effects of the dopant sites on the electronic structure of the material are additive, so increasing the doping concentration will enhance the optical absorption properties of the material in the visible and infrared regions. Further increasing the doping concentration will result in a larger gap between the maximum edge of impurity bands and the conduction band minimum, and will undermine the optical absorption in the visible and infrared region. Such effects are caused by the local geometry change at the high local doping concentration with the dopants displaced from the original O sites, so the resulting impurity bands are no long the superpositions of the impurity bands of each individual on-site dopant atom. Switching from S-doping to Se-doping decreases the gap between the maximum edge of the impurity bands and conduction band minimum, and leads to the optical absorption edge red-shifting further into the visible and infrared regions.
进行了第一性原理计算，以了解阴离子等价位原子掺杂如何影响α-MoO的电子结构和光学性质。研究了硫和硒在α-MoO的三个独特氧位点（O、O和O）处的掺杂效应。我们发现，硫/硒掺杂原子的价p轨道在α-MoO的能带结构中产生了高于价带最大值的杂质带。掺杂材料中杂质带的数量取决于特定的掺杂位点以及MoO中掺杂剂的局部化学环境。杂质带导致了S掺杂和Se掺杂的MoO在可见光和红外区域的光吸收增强。在低局部掺杂浓度下，掺杂位点对材料电子结构的影响是累加的，因此增加掺杂浓度会增强材料在可见光和红外区域的光吸收特性。进一步增加掺杂浓度会导致杂质带的最大边缘与导带最小值之间的能隙增大，并会削弱可见光和红外区域的光吸收。这种效应是由高局部掺杂浓度下的局部几何结构变化引起的，掺杂剂从原来的O位点位移，因此产生的杂质带不再是每个单个在位掺杂原子的杂质带的叠加。从S掺杂切换到Se掺杂会减小杂质带的最大边缘与导带最小值之间的能隙，并导致光吸收边缘进一步红移到可见光和红外区域。
