Friction measurement with single atom resolution

This thesis presents high-precision lateral force microscopy (LFM) measurements using atomically characterized tips, focusing on the atomic-scale mechanisms underlying frictional forces. The research investigates the role of atomic interactions on LFM contrast as a function of tip-sample distance, explores friction across single chemical bonds, and examines the contribution of phonons to friction. Advanced experimental setups, including qPlus sensors for simultaneous scanning tunneling microscopy (STM) and LFM measurements, and precise tip characterization techniques, are employed to study these subjects. The study reveals critical insights into in-plane interactions and energy dissipation at the single-atom level. High-resolution imaging with CO-functionalized tips elucidates the relationship between friction and factors like system stiffness. By mapping energy dissipation across chemical bonds, the work establishes a linear correlation between bond order and energy dissipation and applies theoretical models, including density functional theory (DFT) and machine learning, to refine predictions. Further investigations address the role of atomic and molecular mass in phononic contributions to friction, using isotopic variations and experiments with hydrogen- and deuterium-terminated surfaces. This includes the discussion about the influence of atomic mass on energy dissipation and discrepancies of previous studies that demand more precise research. Overall, this work advances the understanding of friction mechanisms at the nanoscale, providing valuable insights into atomic-scale energy dissipation and its theoretical underpinnings.