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Register a new userAtomic-Scale Structure Relaxation, Chemistry and Charge Distribution of Dislocation Cores in SrTiO3
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By using the state-of-the-art microscopy and spectroscopy in aberration-corrected scanning transmission electron microscopes, we determine the atomic arrangements, occupancy, elemental distribution, and the electronic structures of dislocation cores in the 10{deg}tilted SrTiO3 bicrystal. We identify that there are two different types of oxygen deficient dislocation cores, i.e., the SrO plane terminated Sr0.82Ti0.85O3-x (Ti3.67+, 0.48<x<0.91) and TiO2 plane terminated Sr0.63Ti0.90O3-y (Ti3.60+, 0.57<y<1). They have the same Burgers vector of a[100] but different atomic arrangements and chemical properties. Besides the oxygen vacancies, Sr vacancies and rocksalt-like titanium oxide reconstruction are also identified in the dislocation core with TiO2 plane termination. Our atomic-scale study reveals the true atomic structures and chemistry of individual dislocation cores, providing useful insights into understanding the properties of dislocations and grain boundaries.
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At the interface between complex insulating oxides, novel phases with interesting properties may occur, such as the metallic state reported in the LaAlO3/SrTiO3 system. While this state has been predicted and reported to be confined at the interface, some works indicate a much broader spatial extension, thereby questioning its origin. Here we provide for the first time a direct determination of the carrier density profile of this system through resistance profile mappings collected in cross-section LaAlO3/SrTiO3 samples with a conducting-tip atomic force microscope (CT-AFM). We find that, depending upon specific growth protocols, the spatial extension of the high-mobility electron gas can be varied from hundreds of microns into SrTiO3 to a few nanometers next to the LaAlO3/SrTiO3 interface. Our results emphasize the potential of CT-AFM as a novel tool to characterize complex oxide interfaces and provide us with a definitive and conclusive way to reconcile the body of experimental data in this system.
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The local structure of CeTe3 in the incommensurate charge density wave (IC-CDW) state has been obtained using atomic pair distribution function (PDF) analysis of x-ray diffraction data. Local atomic distortions in the Te-nets due to the CDW are larger than observed crystallographically, resulting in distinct short and long Te-Te bonds. Observation of different distortion amplitudes in the local and average structures are explained by the discommensurated nature of the CDW since the PDF is sensitive to the local displacements within the commensurate regions whereas the crystallographic result averages over many discommensurated domains. The result is supported by STM data. This is the first quantitative local structural study within the commensurate domains in an IC-CDW system.
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