Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University in Prague, 128 43 Prague 2, Czech Republic.
Bremen Center for Computational Materials Science, University of Bremen, Am Fallturm 1, 28359 Bremen, Germany.
Phys Chem Chem Phys. 2019 Dec 14;21(46):25802-25808. doi: 10.1039/c9cp05638f. Epub 2019 Nov 15.
MXenes are 2D transition metal carbides with high potential for overcoming limitations of conventional two-dimensional electronics. In this context, various MXenes have shown magnetic properties suitable for applications in spintronics, yet the number of MXenes reported so far is far smaller than their parental MAX phases. Therefore, we have studied the structural, electronic and magnetic properties of bimetallic and vacancy-ordered MXenes derived from a new (VZr)AlC MAX phase to assess whether MXene exfoliation would return stable magnetic materials. In particular, we have investigated the properties of pristine and surface-functionalized (VZr)CX bimetallic and (V□)CX (where □ denotes the vacancies) vacancy-ordered MXenes (X = O, F and OH). Our density functional theory (DFT) calculations showed that modifying the MXene stoichiometry and/or MXene surface functionalization changes MXene properties. After testing all possible combinations of metallic motifs and functionalization, we identified (VZr)CX, (V□)CF and (V□)C(OH) as stable structures. Among them, (VZr)CO MXene is predicted to be an FM intrinsic half-semiconductor with a remarkably high Curie temperature (T) of 270 K. The (VZr)C(OH) MXene exhibits a rather low work function (WF) (1.37 eV) and is thus a promising candidate for ultra-low work function electron emitters. Conversely, the (V□)CF MXene has a rather high WF and hence can be used as a hole injector for Schottky-barrier-free contact applications. Overall, our proof-of-concept study shows that theoretical predictions of MXene exfoliation and properties support further experimental research towards developing spintronics devices.
MXenes 是具有二维过渡金属碳化物，具有克服传统二维电子学限制的高潜力。在这种情况下，各种 MXenes 表现出适合用于 spintronics 的磁性特性，但迄今为止报道的 MXenes 数量远远小于其母体 MAX 相。因此，我们研究了源自新型 (VZr)AlC MAX 相的双金属和空位有序 MXenes 的结构、电子和磁性性质，以评估 MXene 剥离是否会返回稳定的磁性材料。特别是，我们研究了原始和表面功能化的 (VZr)CX 双金属和 (V□)CX（其中□表示空位）空位有序 MXenes（X = O、F 和 OH）的性质。我们的密度泛函理论（DFT）计算表明，改变 MXene 的化学计量和/或 MXene 表面功能化会改变 MXene 的性质。在测试了所有可能的金属图案和功能化组合之后，我们确定了 (VZr)CX、(V□)CF 和 (V□)C(OH) 为稳定结构。其中，(VZr)CO MXene 被预测为具有 270 K 高居里温度（T）的 FM 本征半半导体。(VZr)C(OH) MXene 的功函数（WF）（1.37 eV）相当低，因此是超低 WF 电子发射器的有前途的候选者。相反，(V□)CF MXene 的 WF 相当高，因此可用于无肖特基势垒接触应用的空穴注入器。总体而言，我们的概念验证研究表明，MXene 剥离和性质的理论预测支持进一步的实验研究，以开发 spintronics 器件。
