Ghasemifard Alireza, Kuc Agnieszka B, Heine Thomas
Theoretical Chemistry, TU Dresden, Bergstraße 66c, 01062 Dresden, Germany.
Helmholtz-Zentrum Dresden-Rossendorf, HZDR, Bautzner Landstraße 400, 01328 Dresden, Germany.
ACS Appl Mater Interfaces. 2025 Jul 9;17(27):39595-39604. doi: 10.1021/acsami.5c05099. Epub 2025 Jun 25.
Molybdenum disulfide (MoS) is a high-potential material for nanoelectronic applications, especially when thinned to a few layers. Liquid-phase exfoliation enables large-scale fabrication of thin films comprising single- and few-layer flakes of MoS or other transition-metal dichalcogenides (TMDCs), exhibiting variations in the flake size, geometry, edge terminations, and overlapping areas. Electronic conductivity of such films is thus determined by two contributions: the intraflake conductivity, reflecting the value of each single layer, and charge transport across these overlapping flakes. Employing first-principles simulations, we investigate the influence of various edge terminations and the overlap between flakes on the charge transport in MoS film models. We identify characteristic electronic edge states originating from the edge atoms and their chemical environment, which resemble donor and acceptor states of doped semiconductors. This makes either electrons or holes to majority carriers and enables selective control over the dominant charge carrier type (n-type or p-type). Compared to pristine nanosheets, overlapping flakes exhibit lower overall conductance. In the best-performing hexagonal flakes occurring in Mo-rich environments, the conductance is reduced by 18% compared to the pristine layer, while the drop by 46% and 58% is predicted for truncated triangular and triangular flakes, respectively, in S-rich environments. An overlap of 6.5 nm is sufficient to achieve the highest possible interflake conductance. These findings allow for rational optimization of experimental conditions for the preparation of MoS and other TMDC semiconducting thin films.
二硫化钼（MoS₂）是一种在纳米电子应用中具有高潜力的材料，特别是当它被减薄到几层时。液相剥离能够大规模制备包含单层和少层二硫化钼薄片或其他过渡金属二硫属化物（TMDCs）的薄膜，这些薄膜在薄片尺寸、几何形状、边缘终止和重叠区域方面存在差异。因此，此类薄膜的电导率由两方面因素决定：薄片内电导率，反映每一层的数值；以及电荷在这些重叠薄片之间的传输。通过第一性原理模拟，我们研究了各种边缘终止以及薄片之间的重叠对二硫化钼薄膜模型中电荷传输的影响。我们识别出源自边缘原子及其化学环境的特征性电子边缘态，它们类似于掺杂半导体的施主和受主态。这使得电子或空穴成为多数载流子，并能够对主导电荷载流子类型（n型或p型）进行选择性控制。与原始纳米片相比，重叠薄片的整体电导率较低。在富钼环境中出现的性能最佳的六边形薄片中，与原始层相比，电导率降低了18%，而在富硫环境中，截断三角形薄片和三角形薄片的电导率预计分别下降46%和58%。6.5纳米的重叠足以实现最高可能的薄片间电导率。这些发现有助于合理优化制备二硫化钼和其他TMDC半导体薄膜的实验条件。
