Abstract:Doped BaSnO3 has arisen many interests recently as one of the promising transparent conducting oxides for future applications. Understanding the microstructural characteristics are crucial for the exploration of relevant devices. In this paper, we investigated the microstructural features of 0.001% La doped BaSnO3 thin film using both conventional and aberration corrected transmission electron microscopes. Contrast analysis shows high densities of Ruddlesden-Popper faults in the film, which are on {100} planes… Show more
“…Strong strain contrast around these boundaries even in HAADF-STEM images implicates the existence of a high level of microstrain, in agreement with the SAED results from above. Different from the previous reports on BSO thin films 15 , 22 , Ruddlesden-Popper faults were rarely observed in the films. Figure 5 Plan-view ADF-STEM images of BSO on LAO ( a – c ) and PSO ( d – f ): ( a , d ) HAADF-, ( b , e ) LAADF-STEM, and ( c , f ) high-magnification HAADF-STEM images.…”
Section: Resultscontrasting
confidence: 99%
“…6(a) ), BSO on PSO displays no such contrast. This periodic contrast originates from the strain around MDs at the interface 22 , 26 . The periodicity of the contrast is half of the distance between MDs as the two-beam condition with g = 020 generates two contrast flips per MD with b = a BSO [010] 20 , 33 .…”
Section: Resultsmentioning
confidence: 99%
“…Conventional TEM (CTEM) techniques have thus been widely used to visualize dislocations and high-resolution scanning TEM (STEM) has been exploited to study characteristic atomic structures in many forms of thin films 13 – 15 , 17 – 19 , 21 – 25 . In particular, the structure at the film-substrate interface and characteristic defects in perovskite thin films, including BSO, have been studied recently 22 , 26 , 27 .…”
Detailed microstructure analysis of epitaxial thin films is a vital step towards understanding essential structure-property relationships. Here, a combination of transmission electron microscopy (TEM) techniques is utilized to determine in detail the microstructure of epitaxial La-doped BaSnO3 films grown on two different perovskite substrates: LaAlO3 and PrScO3. These BaSnO3 films are of high current interest due to outstanding electron mobility at ambient. The rotational disorder of low-angle grain boundaries, namely the in-plane twist and out-of-plane tilt, is visualized by conventional TEM under a two-beam condition, and the degree of twists in grains of such films is quantified by selected-area electron diffraction. The investigation of the atomic arrangement near the film-substrate interfaces, using high-resolution annular dark-field scanning TEM imaging, reveals that edge dislocations with a Burgers vector along [001] result in the out-of-plane tilt. It is shown that such TEM-based analyses provide detailed information about the microstructure of the films, which, when combined with complimentary high-resolution X-ray diffraction, yields a complete structural characterization of the films. In particular, stark differences in out-of-plane tilt on the two substrates are shown to result from differences in misfit dislocation densities at the interface, explaining a puzzling observation from X-ray diffraction.
“…Strong strain contrast around these boundaries even in HAADF-STEM images implicates the existence of a high level of microstrain, in agreement with the SAED results from above. Different from the previous reports on BSO thin films 15 , 22 , Ruddlesden-Popper faults were rarely observed in the films. Figure 5 Plan-view ADF-STEM images of BSO on LAO ( a – c ) and PSO ( d – f ): ( a , d ) HAADF-, ( b , e ) LAADF-STEM, and ( c , f ) high-magnification HAADF-STEM images.…”
Section: Resultscontrasting
confidence: 99%
“…6(a) ), BSO on PSO displays no such contrast. This periodic contrast originates from the strain around MDs at the interface 22 , 26 . The periodicity of the contrast is half of the distance between MDs as the two-beam condition with g = 020 generates two contrast flips per MD with b = a BSO [010] 20 , 33 .…”
Section: Resultsmentioning
confidence: 99%
“…Conventional TEM (CTEM) techniques have thus been widely used to visualize dislocations and high-resolution scanning TEM (STEM) has been exploited to study characteristic atomic structures in many forms of thin films 13 – 15 , 17 – 19 , 21 – 25 . In particular, the structure at the film-substrate interface and characteristic defects in perovskite thin films, including BSO, have been studied recently 22 , 26 , 27 .…”
Detailed microstructure analysis of epitaxial thin films is a vital step towards understanding essential structure-property relationships. Here, a combination of transmission electron microscopy (TEM) techniques is utilized to determine in detail the microstructure of epitaxial La-doped BaSnO3 films grown on two different perovskite substrates: LaAlO3 and PrScO3. These BaSnO3 films are of high current interest due to outstanding electron mobility at ambient. The rotational disorder of low-angle grain boundaries, namely the in-plane twist and out-of-plane tilt, is visualized by conventional TEM under a two-beam condition, and the degree of twists in grains of such films is quantified by selected-area electron diffraction. The investigation of the atomic arrangement near the film-substrate interfaces, using high-resolution annular dark-field scanning TEM imaging, reveals that edge dislocations with a Burgers vector along [001] result in the out-of-plane tilt. It is shown that such TEM-based analyses provide detailed information about the microstructure of the films, which, when combined with complimentary high-resolution X-ray diffraction, yields a complete structural characterization of the films. In particular, stark differences in out-of-plane tilt on the two substrates are shown to result from differences in misfit dislocation densities at the interface, explaining a puzzling observation from X-ray diffraction.
“…2a) as well as the half-period displacement of the La-columns across the stacking fault (Fig. 2b) are characteristic of a Ruddlesden-Popper (RP) fault due to the double LaO layer 28 .…”
Solid phase crystallization offers an attractive route to synthesize Ni nanoparticles on a La2O3 support. These materials have shown great promise as catalysts for methane oxidation and similar reactions. Synthesis is achieved by the reduction of a LaNiO3 (LNO) precursor at high temperatures, but the reduction pathway can follow a variety of routes. Optimization of catalytic properties such as the long-term stability has been held back by a lack of understanding of the factors impacting the reduction pathway, and its strong influence on the structure of the resulting Ni/La2O3 catalyst. Here we show the first evidence of the importance of extended structural defects in the LNO precursor material (2D stacking faults and 3D inclusions) for determining the reaction pathway and therefore the properties of the final catalyst. Here we compare the crystallization of LNO nanoparticles via two different pathways using in-situ STEM, in-situ synchrotron XRD, and DFT electronic structure calculations. Control of extended defects is shown to be a key microstructure component for improving catalyst lifetimes.
“…Prior to the work by Huang et al . 13 , while there had been studies at atomic resolution of PK multi-layer structures 26 , PK BiFeO 3 layers 27 and Ruddelsden-Popper faults in perovskite PK BaSnO 3 layers 28 , there had been no direct observations of B -site cation distributions within Aurivillius phase structures, either generally or specifically in the multiferroic B6TFMO system 29 , 30 . As Huang et al .…”
The five-layer Aurivillius phase Bi6TixFeyMnzO18 system is a rare example of a single-phase room temperature multiferroic material. To optimise its properties and exploit it for future memory storage applications, it is necessary to understand the origin of the room temperature magnetisation. In this work we use high resolution scanning transmission electron microscopy, EDX and EELS to discover how closely-packed Ti/Mn/Fe cations of similar atomic number are arranged, both within the perfect structure and within defect regions. Direct evidence for partitioning of the magnetic cations (Mn and Fe) to the central three of the five perovskite (PK) layers is presented, which reveals a marked preference for Mn to partition to the central layer. We infer this is most probably due to elastic strain energy considerations. The observed increase (>8%) in magnetic cation content at the central PK layers engenders up to a 90% increase in potential ferromagnetic spin alignments in the central layer and this could be significant in terms of creating pathways to the long-range room temperature magnetic order observed in this distinct and intriguing material system.
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