Rise, fall, and rebirth of an oxide: Growth and evolution of bismuth oxide on Au(111)

We report a comprehensive, multitechnique study of bismuth oxide growth on Au(111) under different conditions such as temperature and exposure to molecular oxygen. By combining synchrotron-based x-ray photoelectron spectroscopy and diffraction with low-energy electron diffraction and scanning tunneling microscopy, we elucidate the structural evolution of the system during controlled oxidation and subsequent annealing. We find that Bi deposition induces well-defined surface reconstructions, whereas oxidation triggers the formation of a complex sequence of bismuth oxide domains. High-resolution spectroscopic and diffraction data enable us to identify an oxide structure consistent with the (201) surface of β − Bi 2 O 3 . In addition, angle-resolved photoemission experiments and work function measurements reveal substantial electronic modifications triggered by a complex interplay of segregation of Bi and Au. Notably, a work function of 3.4 eV is achieved for oxidation at 423 K. These results provide benchmark structural and electronic insights into the Bi oxide/Au(111) system and establish a framework for integrating Bi 2 O 3 as a contact material in devices using two-dimensional semiconductors, where it can enable low contact resistance.