Hydrogenated diamond-like carbon (H-DLC) is typically produced as a coating or thin film through plasma-enhanced chemical vapor deposition (PE-CVD). H-DLC is relatively hard and well known to exhibit superlubricity. Is superlubricity an intrinsic property of H-DLC? This paper argues that H-DLC is not intrinsically superlubricious, but it has an ideal structure that allows transition of the interface region to a superlubricious structure upon frictional shear in proper conditions. Thus, its superlubricity is an extrinsic property. This argument is made by comparing frictional behaviors of three allotropes of carbon materials—graphite, amorphous carbon (a-C), and diamond, and carefully scrutinizing the run-in behavior as well as environment sensitivity of H-DLC friction. The superlubricious structure is generally known to be graphitic, but its exact structure remains elusive and is subject to further study. Nevertheless, accurate knowledge of how superlubricity is induced for H-DLC can guide engineering design to achieve superlubricious behaviors with other carbon materials produced via different synthetic routes.

The atomic edge structure of graphene governs its unique electronic properties with applications in nanoscale electronics and optoelectronics. To fully realize its potential, it is critical to develop a precision etching process producing graphene edges along desired directions. Here, we present a novel approach utilizing scanning probe lithography (SPL) facilitated by a mechanochemical atomic attrition process. This technique enables the fabrication of nanopatterns in single-layer graphene from graphene edges, precisely along the crystallographic orientation of zigzag (ZZ) and armchair (AC) edges, without inducing mechanical damage to the surrounding area. Density functional theory (DFT) calculations revealed that the dissociation of C‒C bonds by the SPL probe is mediated by the formation of interfacial bridge bonds between the graphene edge and the reactive silica surface. This SPL-based mechanochemical etching method enables the construction of various nanodevice structures with specific edge orientations, which allows the exploitation of their electronic properties.