Microscopic origin and location of interfacial Ti3+ states

Determine whether the Ti3+ states at the RuO2/TiO2 interface are confined to an interfacial TiO2 layer as a result of charge transfer or are incorporated into an interfacial TixRu1−xO2 layer through local Ru–Ti intermixing.

Background

Angle-dependent hard X-ray photoemission spectroscopy establishes Ti3+ formation at the buried RuO2/TiO2 interface, but quantitative modeling is consistent with two distinct microscopic scenarios. In one scenario, Ti3+ is confined to an interfacial TiO2 layer; in the other, Ti3+ is incorporated into an interfacial TixRu1−xO2 layer. Because the available spectroscopy cannot distinguish these possibilities, the microscopic location and formation mechanism of the Ti3+ states remain unresolved.

Resolving this problem is important for determining whether the interfacial Ti3+ states arise from charge redistribution across the interface or from local Ru–Ti intermixing, and for assessing their possible role in the anomalous Hall effect. The paper addresses whether Ti3+ is sufficient to account for the anomalous Hall response through Ti-alloyed control heterostructures, but it does not resolve the microscopic location of the Ti3+ states in the original RuO2/TiO2 interface.