Superlubric Sliding of Graphene Auto-Kirigami with Interfaces Containing Self-Assembled Stripe-Pattern Adsorbates

Abstract

Van der Waals heterostructures formed by stacked 2D materials show exceptional electronic, mechanical, and optical properties. Superlubricity, a condition where atomically flat, incommensurate planes of atoms results in ultra-low friction, is a prime example enabling, for example, self-assembly of optically visible graphene nanostructures in air via a sliding auto-kirigami process. Here, we demonstrate that a subtle but ubiquitous adsorbate stripe structure found on graphene and graphitic surfaces in ambient conditions remains stable within the interface between twisted graphene layers as they slide over each other. Despite this contamination, the interface retains an exceptional superlubricious state, indicating that direct atomic incommensurate contact is not required to achieve ambient superlubricity for 2D materials. Using a simple continuum model for the self-assembly, we calculate an upper bound frictional shear strength of 10 kPa consistent with estimates of microscale graphite pillar superlubricity. Our results suggest that any phenomena depending on 2D heterostructure interfaces such as exotic electronic behaviour may need to consider the presence of stripe adsorbate structures that remain intercalated.