Completing the picture of initial oxidation on copper

Highlights: • Accurate atomistic models for interfaces play a pivotal role in many applications. • Detailed atomic structure models of oxygen-copper surface oxides remain elusive. • State-of-the-art STM simulations and high-resolution STM experiments are performed. Accurate atomistic models for metal/oxide interfaces play a pivotal role in determining copper-based interfacial processes, ranging from electronic circuitry wirings to chemical catalysis. The "29" and "44" surfaces represent two of the most classical embryonic oxides on Cu(111). Although many attempts have been made to offer detailed atomistic models of these surface oxides, their atomic structures remain elusive. Here, we address this open question via ab initio STM simulations, where the functionalized-metal tips are explicitly included, and they are corroborated by STM experiments. We find that the fine structures of STM images of the "29" and "44" surfaces are correctly captured with STM theories going beyond the Tersoff-Hamann approximation only. Furthermore, we elucidate a complete atomistic model for the larger "44" surface, completing the picture of early oxidation on copper.