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Enhancement of the anisotropic photocurrent in ferroelectric oxides by strain gradients

Nature Nanotechnology volume 10, pages 972–979 (2015)Cite this article

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Abstract

The phase separation of multiple competing structural/ferroelectric phases has attracted particular attention owing to its excellent electromechanical properties. Little is known, however, about the strain-gradient-induced electronic phenomena at the interface of competing structural phases. Here, we investigate the polymorphic phase interface of bismuth ferrites using spatially resolved photocurrent measurements, present the observation of a large enhancement of the anisotropic interfacial photocurrent by two orders of magnitude, and discuss the possible mechanism on the basis of the flexoelectric effect. Nanoscale characterizations of the photosensitive area through position-sensitive angle-resolved piezoresponse force microscopy and electron holography techniques, in conjunction with phase field simulation, reveal that regularly ordered dipole-charged domain walls emerge. These findings offer practical implications for complex oxide optoelectronics.

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Figure 1: Enhancement of photocurrent in mixed-phase areas.
Figure 2: Light polarization dependence of the photocurrent.
Figure 3: Estimation of photocurrent enhancement at the polymorphic phase interfaces.
Figure 4: Position-sensitive angle-resolved PFM in a mixed-phase area.
Figure 5: Phase field simulation to explore the flexoelectric effect at the interfacial region.
Figure 6: Strain and total charge density maps of a mixed-phase area obtained using inline electron holography.

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Acknowledgements

This work was supported by the National Research Foundation (NRF) of Korea funded by the Korean Government (contract nos. NRF-2011-0016133, 2013S1A2A2035418, 2014R1A2A2A01005979, 2015R1A2A2A01007904 and 2012R1A2A2A01046191). This work was also supported by the Institute for Basic Science (IBS), Korea, under project code IBS-R014-G1. The research was supported by the Pioneer Research Center Program through the NRF of Korea funded by the Ministry of Science, ICT & Future Planning (no. 2012-0009460) and the Global Frontier Hybrid Interface Materials of the NRF of Korea funded by the Korea Government (2013M3A6B1078872). C.-H.Y. acknowledges support from the T.J. Park Science Fellowship. S.-H.O. thanks P. van Aken, head of the Stuttgart Center for Electron Microscopy, for granting us access to the SESAM.

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Authors and Affiliations

  1. Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 305-701, Republic of Korea

    Kanghyun Chu, Byung-Kweon Jang, Jin Hong Lee, Chang-Su Woo, Seung Jin Kim & Chan-Ho Yang

  2. Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Gyeongbuk, Korea

    Ji Ho Sung & Moon-Ho Jo

  3. Center for Artificial Low-Dimensional Electronic Systems, Institute for Basic Science (IBS), POSTECH, Pohang, 790-784, Gyeongbuk, Republic of Korea

    Ji Ho Sung & Moon-Ho Jo

  4. Department of Materials Science and Engineering, POSTECH, Pohang, 790-784, Gyeongbuk, Republic of Korea

    Yoon Ah Shin, Kyung Song, Sang-Ho Oh & Moon-Ho Jo

  5. Graduate School of Nanoscience and Technology, KAIST, Daejeon, 305-701, Republic of Korea

    Eui-Sup Lee & Yong-Hyun Kim

  6. Department of Materials Modeling and Characterization, Korea Institute of Materials Science, Changwon, 642-831, Republic of Korea

    Si-Young Choi

  7. Pohang Accelerator Laboratory, POSTECH, Pohang, 790-784, Gyeongbuk, Republic of Korea

    Tae Yeong Koo

  8. KAIST Institute for the NanoCentury, Daejeon, 305-701, Republic of Korea

    Chan-Ho Yang

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Contributions

K.C. and C.-H.Y. conceived the work. J.H.S., K.C. and M.-H.J. performed and analysed the photocurrent measurements. K.C. measured angle-resolved PFM images. Y.A.S., K.S., S.-Y.C. and S.-H.O. performed TEM and electron holography. K.C. and B.-K.J. carried out phase field simulations and finite element method simulations. E.-S.L. and Y.-H.K. calculated materials parameters using density functional calculations. J.H.L. and T.Y.K. analysed the crystalline structures using X-ray reciprocal space mapping. C.-S.W. and S.J.K. grew epitaxial films. K.C. and C.-H.Y. wrote the manuscript with help from all the other authors.

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Correspondence to Chan-Ho Yang.

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Chu, K., Jang, BK., Sung, J. et al. Enhancement of the anisotropic photocurrent in ferroelectric oxides by strain gradients. Nature Nanotech 10, 972–979 (2015). https://doi.org/10.1038/nnano.2015.191

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