(378b) Ni Adsorption, Ingress, and Egress on SrTiO3 Single Crystals

Perovskite-oxides are ubiquitous in numerous application e.g., electronic and optical devices, as well as heterogenous catalysis [1,2]. One highly studied perovskite is strontium titanate (SrTiO₃) due to its piezoelectricity, high-temperature stability, and doping tunability [1,2,3]. Specifically, metal ion, such as Ni, adsorption, doping, and migration, both ingress or egress from the surface, on STO has gotten attention [4,5,6]. Depending on the application and starting point, the Ni-STO system can be tuned toward Ni ingress or egress. For example, Ni egress from STO₃ is a preferred process in novel heterogenous catalyst synthesis methods like exsolution, while Ni ingress is of relevance for applications where maintaining uniform doping is crucial to guarantee specific electronic properties for semiconducting modifications, or simply as dispersed surface Ni-adatoms [4,5,6]. Currently, a comprehensive understanding of the different elementary reaction steps and factors involved in these processes is still lacking.

In this study, we examined the thermodynamics and particular interactions of Ni across different surface facets of STO. A detailed analysis was performed for the distinct factors that are involved in such interactions including metal adsorption sites, binding strength, and doping specifically for the Ni-STO system to name a few. Furthermore, using ab initio steered molecular dynamics and umbrella sampling in the NVT ensemble, we investigated the ingress/egress behavior of Ni across the considered STO surface facets by studying different migration mechanisms including interstitial and doped ingress/egress pathways. Figure 1 shows the most stable binding energies for Ni adsorbed on STOon four different surface facets and terminations, clearly displaying the trends and differences among them. Using these metrics, and understanding the nature of these unique interactions, we are able to rationalize the system’s stability, ingress/egress propensity, and identify the major factors that influence design choices for this system.