Although metal oxides dominate many areas of materials technology, many questions remain regarding how these materials function at the atomic scale. One way to model them is by using single crystals prepared under ultra-high vacuum (UHV). The standard preparation treatments used to clean surfaces in UHV, however, may result in rougher-than-desired surfaces, making it difficult to model atomic processes.

Franceschi et al. presented an experimental strategy to work around this problem and optimize the flatness of oxide surfaces in UHV. By tuning the reconstructions of three model oxide surfaces through the chosen values of oxygen chemical potential, the group could enforce reconstructions of different compositions while promoting the flattening of the surface morphology, demonstrating a new way to enhance surface diffusion.

In addition to optimizing surface morphologies, the strategy is poised to improve the growth of oxide films.

“We have found a way to prepare ultra-flat surfaces of oxide films, and we can explain why it works so well: the arrangement of surface atoms changes depending on the surrounding gas atmosphere,” Giada Franceschi. “Each time the environment changes, the structure changes, and atoms are driven across the surface. The enhanced mobility leads to a smoothing of asperities.”

They chose three oxides – α-Fe2O3, La(1-x)SrxMnO3, and In2O3 – to showcase the diversity of applications the process can accommodate, from spintronics to water splitting to gas-sensing.

“In our group, we work with many other oxides – and we have indications that our strategy works for all of them!” Franceschi said.

Franceschi hopes the work encourages others to examine atom-level diffusion on oxide surfaces. The group aims to continue work on these materials.

Source: “Reconstruction changes drive surface diffusion and determine the flatness of oxide surfaces,” by Giada Franceschi, Michael Schmid, Ulrike Diebold, and Michele Riva, Journal of Vacuum Science & Technology A (2022). The article can be accessed at

This paper is part of the Honoring Dr. Scott Chambers’ 70th Birthday and His Leadership in the Science and Technology of Oxide Thin Films Collection, learn more here.