Template-free scalable growth of vertically-aligned MoS nanowire array -structural films towards robust superlubricity.

Two-dimensional (2D) molybdenum disulfide exhibits a variety of intriguing behaviors depending on its orientation layers. Therefore, developing a template-free atomic layer orientation controllable growth approach is of great importance. Here, we demonstrate scalable, template-free, well-ordered vertically-oriented MoS nanowire arrays (VO-MoS NWAs) embedded in an Ag-MoS matrix, directly grown on various substrates (Si, Al, and stainless steel) one-step sputtering. In the -structured film, vertically-standing few-layered MoS NWAs of almost micron length (∼720 nm) throughout the entire film bulk. While near the surface, MoS lamellae are oriented in parallel, which are beneficial for caging the bonds dangling from the basal planes. Owing to the unique T-type topological characteristics, chemically inert Ag@MoS nano-scrolls (NSCs) and nano-crystalline Ag (nc-Ag) nanoparticles (NPs) are formed under the sliding shear force. Thus, incommensurate contact between (002) basal planes and nc-Ag NPs is observed. As a result, robust superlubricity (friction coefficient = 0.0039) under humid ambient conditions is reached. This study offers an unprecedented strategy for controlling the basal plane orientation of 2D transition metal dichalcogenides (TMDCs) substrate independence, using a one-step solution-free easily scalable process without the need for a template, which promotes the potential applications of 2D TMDCs in solid superlubricity.