Advancing Atom Probe Tomography of SrTiO$_3$: Measurement Methodology and Impurity Detection Limits

Strontium titanate (STO) possesses promising properties for applications in thermoelectricity, catalysis, fuel cells, and more, but its performance is highly dependent on stoichiometry and impurity levels. While atom probe tomography (APT) can provide detailed three-dimensional atomic-scale chemical information, STO specimens have been challenging to analyze due to premature specimen fracture. In this study, we show that by applying a thin metal coating to atom probe tips, STO specimens can be analyzed with nearly 100% success. Using this approach, we investigate both undoped STO and 1 at% Nb-doped STO, achieving sufficient sensitivity to detect Nb concentrations as low as 0.7 at%. This work establishes a reliable APT method for high-resolution chemical analysis of STO at the nanoscale.