A research team with leading scientists of Prof. MA Xiuliang, Prof. ZHU Yinlian and Dr. TANG Yunlong from Institute of Metal Research, Chinese Academy of Sciences, recently fabricate a lead-free perovskite nanostructure array with a linear gradient as giant as 106/m, featuring an extremely lower elastic energy cost compared with a uniformly strained state.
As known that elastic strains, particularly inhomogeneous strains, can tune, enhance, or create novel properties of some nanoscale functional materials. It's still infeasible to achieve potential devices with exotic properties dominated by inhomogeneous strains. Such stagnations lie in the general predetermination that the elastic energy resultant from the disclination strains therein would be so pronounced that a large scale assembling of inhomogeneous strains could be rather difficult.
Thanks to a long-standing tradition with several decades of applying transmission electron microscopy to materials science, the research team have artificially produced a giant linear strain gradient in the BiFeO3/LaAlO3 multilayer nanostructures by a controlled pulsed laser deposition via a high deposition flux mode.
The present strain gradient, causes a polarization of several microcoulomb per square centimeter through flexoelectric coupling, which is derived from the strain mapping on the basis of aberration-corrected scanning transmission electron microscopy.
The present strain gradient also leads to a large built-in electric field of several megavoltage per meter which is comparable to that of the conventional p-n junctions and Schottky diodes. And it makes it possible to greatly enhance the solar absorption as confirmed by the UV-visible absorption measurements.
The elastic energy consumption for producing such a giant strain gradient is extremely lower than previously regarded. And it is shown that the giant strain gradient enables to transfer across a multilayer structure possibly reaching a practical scale.
These results indicate the possibility of building up a large-scale strain-dominated nanostructure array with exotic properties by engineering strains with giant linear gradient, which in turn could be useful for a potential application in the field of electromechanics and photoelectricity.
Their work, entitled "Giant linear strain gradient with extremely low elastic energy in a perovskite nanostructure array", is detailed in Nature Communications.
Figure. Lattice rotation (ω) and in-plane strain (εxx) maps of the two-layer LaAlO3/BiFeO3/LaAlO3(001) nanostructures. (a) 2D lattice rotation (ω) and (b) in-plane strain (εxx) maps via GPA. Profiles corresponding to the three marked lines in (a) are visualized in (c). A white boxed area labeled as ‘line profile’ in (b) is chosen as a visualization line-profile shown in (d). A blue dotted line in (d) indicates the nominal mismatch magnitude (4.5%) for BiFeO3/LaAlO3(001). The strain gradient of εxx is estimated by the slopes of the curve in (d), which is well above 106/m order.(Image by IMR)
Contact:
Prof. MA Xiuliang
Institute of Metal Research, Chinese Academy of Sciences
72 Wenhua Road, Shenyang 110016, China
E-mail:xlma@imr.ac.cn
