Influence of the support on stabilizing local defects in strained monolayer oxide films

Research by the Surface Nanoscience group led by Professor Castell and collaborators at the French National Center for Scientific Research as reported in Nanoscale , shows a variety of non-hexagonal local defects in a honeycomb monolayer Ti₂O₃ film on an Au(111) support. The most familiar of these types of defects is the Stone-Wales defect, frequently found in graphene and other 2D materials. Often these non-hexagonal defects also include a divacancy, which tends to lead to local tensile strain around the defects. Our oxide monolayer film is elastically compressively strained due to the pseudomorphic interaction with the Au substrate, which means that in our system divacancy defects act to reduce the local strain in the monolayer. They therefore have relatively low formation energies compared to similar defects in graphene. The wider implication is that the same change in defect energies will be observed in other compressively strained epitaxially monolayers. However, for monolayers in tension, the opposite will be the case, resulting in a prevalence of Stone-Wales defects compared with divacancy defects.