Transient Formation of Single Layer Diamond During Friction Force Microscopy of SiC‐Supported Epitaxial Graphene

Carbon allotropes are crucial to advanced interfaces to control friction and wear because of their unique range of mechanical properties: from diamond's hardness to graphite's lubricity. Friction force microscopy (FFM) is reported for diamond tips sliding on SiC(0001)‐supported epitaxial graphene. A sharp friction increase is observed at a threshold normal force, linked to an intermittent graphene rehybridization. Comparing the FFM response of a diamond tip to that of a previously studied silicon tip with a comparable radius reveals a similar abrupt friction increase, though at roughly half the threshold force. Atomistic simulations of SiC(0001)‐supported graphene sliding against hydroxylated amorphous carbon (a‐C) and silicon oxide show low shear stress at low pressures for both systems. The shear stress increases at higher pressures due to bond formation between graphene and the counterbody. For a‐C, the transition threshold shifts to higher pressures, consistent with FFM results. In simulations with high normal pressures, epitaxial graphene undergoes a structural transformation into single‐layer diamond, contributing to the abrupt increase in friction. The graphene structure recovers after lifting the a‐C counterbody, demonstrating structural robustness under tribological stress. These findings provide insights into the stability of low‐friction interfaces between epitaxial graphene and key materials for current micro‐electro‐mechanical systems (MEMS)