Defects in crystals play a fundamental role in modulating mechanical, electrical, luminescent, and magnetic behaviors of materials. However, accurate measurement of defect structures is hindered by symmetry breaking and the corresponding complex modifications in atomic configuration and/or crystal tilt at the defects. Here, we report the deep-sub-angstrom resolution imaging of dislocation cores via multislice electron ptychography with adaptive propagator, which allows sub-nanometer scale mapping of crystal tilt in the vicinity of dislocation cores and simultaneous recovery of depth-dependent atomic structure of dislocations. The realization of deep-sub-angstrom resolution and depth-dependent imaging of defects shows great potential in revealing microstructures and properties of real materials and devices.
The development of high-performance thermoelectric materials can help solve the energy crisis in the future. Thin-film thermoelectric materials can meet the flexibility requirement for wearable devices while supplying electrical power to them. In this study, high-quality Nb-doped SrTiO<sub>3</sub> films (Nb:STO) with different thicknesses were prepared on SrTiO<sub>3</sub> (STO) and La<sub>0.3</sub>Sr<sub>0.7</sub>Al<sub>0.65</sub>Ta<sub>0.35</sub>O<sub>3</sub>(LSAT) substrates by pulsed laser deposition. The surface morphology, crystal structure and thermoelectric performance of the films were characterized. The results show that the thermoelectric performance of the strain-free film increase with different thicknesses. The power factor at room temperature increases by 187%. The Seebeck coefficient of the 144 nm-thick-Nb:STO/LSAT sample with strain is greatly improved to 265.95μV/K at room temperature, which is likely due to strain induced changes in the energy band of the thin films. The improvement of the thermoelectric performance of Nb:STO thin films by strain engineering provides a new approach to improving the thermoelectric properties of oxide thin films.
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