Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 151-744, Korea.
Nanoscale. 2017 Mar 23;9(12):4265-4271. doi: 10.1039/c6nr08555e.
We theoretically elucidate the origin of unintentional doping in two-dimensional transition-metal dichalcogenides (TMDs), which has been consistently reported by experiment, but which still remains unclear. Our explanation is based on the charge transfer between TMDs and the underlying SiO in which hydrogen impurities with a negative-U property pin the Fermi level of the SiO as well as adjacent TMD layers. Using first-principles calculations, we obtain the pinning point of the Fermi level from the charge transition level of the hydrogen in the SiO, ε(+/-), and align it with respect to the band-edge positions of monolayer TMDs. The computational results show that the Fermi levels of TMDs estimated by ε(+/-) successfully explain the conducting polarity (n- or p-type) and relative doping concentrations of thin TMD films. By enlightening on the microscopic origin of unintentional doping in TMDs, we believe that the present work will contribute to precise control of TMD-based electronic devices.
我们从理论上阐明了二维过渡金属二卤族化合物（TMD）中无意掺杂的起源，这一现象在实验中一直被报道，但仍不清楚其原因。我们的解释基于 TMD 与底层 SiO 之间的电荷转移，其中具有负-U 特性的氢杂质会固定 SiO 以及相邻 TMD 层的费米能级。通过第一性原理计算，我们从 SiO 中氢的电荷转移能级 ε(+/-)获得费米能级的固定点，并将其与单层 TMD 的能带边缘位置对齐。计算结果表明，ε(+/-) 估算的 TMD 费米能级成功解释了薄 TMD 薄膜的导电极性（n 型或 p 型）和相对掺杂浓度。通过阐明 TMD 中无意掺杂的微观起源，我们相信本工作将有助于精确控制基于 TMD 的电子器件。
