• Hofer, Ferdinand
• Kothleitner, Gerald
• Unterleutner, Elena Martina
• Kobald, Alexander
• Knez, Daniel

Abstract

SrTiO3 (STO) is one of many complex oxide materials, which are of high interest in a<br/>plethora of technological applications due to their wide range of magnetic and electronic<br/>properties. Introducing small amounts of dopants and/or vacancies into the materials can<br/>tailor these properties over a wide range. Therefore, information about the electronic and the<br/>structural configuration of defects is essential. In metal oxides such as STO, solids are<br/>ionically bonded with many types of defects that shape the properties. 0D-defects or point<br/>defects play a major role regarding controlling and optimizing these materials. Figure 1<br/>shows different point defects in ionic compounds. The materials chosen for method<br/>development and optimization is STO, doped with low concentrations of Ta or Al. By<br/>leveraging the various modalities available in an aberration corrected STEM, such as<br/>integrated differential phase contrast (iDPC) imaging, annular dark field (ADF) imaging and<br/>core-loss electron energy loss spectroscopy (EELS), we deduce information about the<br/>distribution and defect structure of the point defects introduced by doping on an atomic level.<br/>This requires extremely thin samples (&lt; 20 unit cells), prepared through wedge polishing.<br/>Precise thickness determination of crystalline parts will be performed by position averaged<br/>convergent beam electron diffraction (PACBED) measurements, in order to allow direct<br/>quantitative comparison with MS<br/>simulations based on atomistic<br/>modelling. Our main focus lies on<br/>the presence of O and Sr<br/>vacancies. Preliminary results<br/>obtained from STO:Ta are<br/>illustrated in Figure 2. The highangle<br/>annular dark-field (HAADF)<br/>signal demonstrates a 30%<br/>intensity increase at certain TiO<br/>atom columns, indicating the<br/>presence of Ta atoms within<br/>those positions. Additionally, a<br/>minor decrease in Sr intensities<br/>adjacent to identified dopant<br/>sites is observed, suggesting the<br/>possible existence of Sr<br/>vacancies near Ta dopants.

Topics

• impedance spectroscopy
• compound
• phase
• simulation
• electron diffraction
• mass spectrometry
• electron energy loss spectroscopy
• defect structure
• polishing
• point defect