Identification of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>A</mml:mi></mml:math>- and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi></mml:math>-Site Cation Vacancy Defects in Perovskite Oxide Thin Films

Abstract

Cation vacancies on both sublattices (${V}_{\mathrm{Ti}}$, ${V}_{\mathrm{Sr}}$) have been identified in homoepitaxial pulsed laser deposited ${\mathrm{SrTiO}}_{3}$ films using high intensity variable energy positron annihilation lifetime spectroscopy (PALS) measurements. Film nonstoichiometry was varied by varying laser fluence. PALS showed that on increasing the fluence above the $\mathrm{Ti}/\mathrm{Sr}\ensuremath{\sim}1$ value, the concentration ratio $[{V}_{\mathrm{Sr}}]/[{V}_{\mathrm{Ti}}]$ systematically increased. Reducing the fluence into the Ti-poor region below resulted in additional vacancy cluster defect formation. Vacancy concentrations greater than $\ensuremath{\sim}50\text{ }\text{ }\mathrm{ppm}$ were observed in all films.