Detect isolated oxygen interstitials below the current imaging threshold

Determine whether isolated single oxygen interstitial atoms are present in Sr$_2$CuO$_{3+\delta}$ below the detection limit of the reported multislice electron ptychography imaging conditions.

Background

The study reports that, under a moderate electron dose of $1.2\times 10^{5}$ electrons/\AA{}$^2$, the minimum detectable signal corresponds to two oxygen interstitials per atomic column. Dose-dependent simulations indicate that a substantially higher dose of $1\times 10^{7}$ electrons/\AA{}^2wouldbeneededtoclearlydistinguishasingleoxygeninterstitialfrombackgroundnoise.Consequently,theexperimentsidentifysmallinterstitialclustersbutdonotresolvewhetherisolatedsingleoxygeninterstitialatomsoccurbelowthepresentdetectionthreshold.Establishingtheirpresencewouldimprovethequantitativecharacterizationofoxygen−dopantdistributionsinSrwould be needed to clearly distinguish a single oxygen interstitial from background noise. Consequently, the experiments identify small interstitial clusters but do not resolve whether isolated single oxygen interstitial atoms occur below the present detection threshold. Establishing their presence would improve the quantitative characterization of oxygen-dopant distributions in Sr2CuOCuO{3+\delta}$.