The achievement of ultraclean Ohmic van der Waals (vdW) contacts at metal/transition-metal dichalcogenide (TMDC) interfaces would represent a critical step for the development of high-performance electronic and optoelectronic devices based on two-dimensional (2D) semiconductors. Herein, we report the fabrication of ultraclean vdW contacts between indium (In) and molybdenum disulfide (MoS₂) and the clarification of the atomistic origins of its Ohmic-like transport properties. Atomically clean In/MoS₂ vdW contacts are achieved by evaporating In with a relatively low thermal energy and subsequently cooling the substrate holder down to ~100 K by liquid nitrogen. We reveal that the high-quality In/MoS₂ vdW contacts are characterized by a small interfacial charge transfer and the Ohmic-like transport based on the field-emission mechanism over a wide temperature range from 2.4 to 300 K. Accordingly, the contact resistance reaches ~600 Ω μm and ~1000 Ω μm at cryogenic temperatures for the few-layer and monolayer MoS₂ cases, respectively. Density functional calculations show that the formation of large in-gap states due to the hybridization between In and MoS₂ conduction band edge states is the microscopic origins of the Ohmic charge injection. We suggest that seeking a mechanism to generate strong density of in-gap states while maintaining the pristine contact geometry with marginal interfacial charge transfer could be a general strategy to simultaneously avoid Fermi-level pinning and minimize contact resistance for 2D vdW materials.

在金属/过渡金属二硫化碳（TMDC）界面上实现超洁净的欧姆范德华（vdW）接触将代表开发基于二维（2D）半导体的高性能电子和光电设备的关键一步。在此，我们报道了铟（In）和二硫化钼（MoS ₂）之间超净vdW接触的制造以及其类似于欧姆的传输性质的原子起源的澄清。原子清洁的In / MoS ₂ vdW触点可通过以相对较低的热能蒸发In，然后通过液氮将衬底支架冷却至〜100 K来实现。我们揭示了高质量的In / MoS ₂vdW触点的特点是界面电荷转移小，并且基于在2.4至300 K的较宽温度范围内的场发射机理，具有类似于欧姆的传输。因此，接触电阻在600Ωμm和1000Ωμm时达到低温分别适用于少层和单层MoS ₂情况。密度泛函计算表明，由于In和MoS ₂之间的杂化，形成了较大的能隙状态导带边缘状态是欧姆电荷注入的微观起源。我们建议寻找一种机制来产生高的间隙状态密度，同时保持原始的接触几何结构和边际界面电荷转移，这可能是同时避免费米能级钉扎并使二维vdW材料的接触电阻最小化的一般策略。