The impact of Mn nonstoichiometry on the oxygen mass transport properties of La0.8Sr0.2MnyO3±δ thin films

Oxygen mass transport in perovskite oxides is relevant for a variety of energy and information technologies. In oxide thin films, cation nonstoichiometry is often found but its impact on the oxygen transport properties is not well understood. Here, we used oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry to study oxygen mass transport and the defect compensation mechanism of Mn-deficient La0.8Sr0.2Mn (y) O-3 +/-delta epitaxial thin films. Oxygen diffusivity and surface exchange coefficients were observed to be consistent with literature measurements and to be independent on the degree of Mn deficiency in the layers. Defect chemistry modeling, together with a collection of different experimental techniques, suggests that the Mn-deficiency is mainly compensated by the formation of La-x(Mn) antisite defects. The results highlight the importance of antisite defects in perovskite thin films for mitigating cationic nonstoichiometry effects on oxygen mass transport properties

The impact of Mn nonstoichiometry on the oxygen mass transport properties of La0.8Sr0.2Mn y O3±δ thin films

Oxygen mass transport in perovskite oxides is relevant for a variety of energy and information technologies. In oxide thin films, cation nonstoichiometry is often found but its impact on the oxygen transport properties is not well understood. Here, we used oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry to study oxygen mass transport and the defect compensation mechanism of Mn-deficient LaSrMn O epitaxial thin films. Oxygen diffusivity and surface exchange coefficients were observed to be consistent with literature measurements and to be independent on the degree of Mn deficiency in the layers. Defect chemistry modeling, together with a collection of different experimental techniques, suggests that the Mn-deficiency is mainly compensated by the formation of La Mn × antisite defects. The results highlight the importance of antisite defects in perovskite thin films for mitigating cationic nonstoichiometry effects on oxygen mass transport properties.This research was supported by the funding from the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 101017709 (EPISTORE) and the 'Generalitat de Catalunya' (2017 SGR 1421, NANOEN). LY acknowledges support from the MINECO (Spain) through the IJC2018-037698-I grant. MICIIN projects PID2019-106165GB-C21 and RED2018-102609-T are also acknowledged. PN acknowledges the support from the AGAUR through the 2021 FI_B 00157 Grant. RADS acknowledges funding from German Research Foundation (DFG) from project DE 2854/12-1 and from the collaborative research center SFB917 'Nanoswitches'. J S acknowledges the financial support of the Spanish Ministry of Economy, Industry and Competitiveness (Project: PID2019-108573GB-C21)

Quantitative Determination of Native Point‐Defect Concentrations at the ppm Level in Un‐Doped BaSnO 3 Thin Films

The high-mobility, wide-bandgap perovskite oxide BaSnO3 is taken as a model system to demonstrate that the native point defects present in un-doped, epitaxial thin films grown by hybrid molecular beam epitaxy can be identified and their concentrations at the ppm level determined quantitatively. An elevated-temperature, multi-faceted approach is shown to be necessary: oxygen tracer diffusion experiments with secondary ion mass spectrometry analysis; molecular dynamics simulations of oxygen-vacancy diffusion; electronic conductivity studies as a function of oxygen activity and temperature; and Hall-effect measurements. The results indicate that the oxygen-vacancy concentration cannot be lowered below 1017.3 cm−3 because of a background level of barium vacancies (of this concentration), introduced during film growth. The multi-faceted approach also yields the electron mobility over a wide temperature range, coefficients of oxygen surface exchange and oxygen-vacancy diffusion, and the reduction enthalpy. The consequences of the results for the lowest electron concentration achievable in BaSnO3 samples, for the ease of oxide reduction and for the stability of reduced films with respect to oxidation, are discussed