Tunneling Hot Spots in Ferroelectric SrTiO₃

Journal Article · Fri Dec 15 00:00:00 EST 2017 · Nano Letters

DOI:https://doi.org/10.1021/acs.nanolett.7b04444· OSTI ID:1484747

Lu, Haidong ^[1]; Lee, Daesu ^[2]; Klyukin, Konstantin  ^[3]; Tao, Lingling ^[1]; Wang, Bo ^[4]; Lee, Hyungwoo ^[2]; Lee, Jungwoo ^[2]; Paudel, Tula R. ^[1]; Chen, Long-Qing ^[4]; Tsymbal, Evgeny Y. ^[5]; Alexandrov, Vitaly ^[5]; Eom, Chang-Beom ^[2]; Gruverman, Alexei  ^[5]

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1. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Physics and Astronomy
2. Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering
3. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Chemical and Biomolecular Engineering
4. Pennsylvania State Univ., University Park, PA (United States). Dept. of Material Sciences and Engineering
5. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Chemical and Biomolecular Engineering, and Nebraska Center for Materials and Nanoscience

Strontium titanate (SrTiO₃) is the “silicon” in the emerging field of oxide electronics. While bulk properties of this material have been studied for decades, new unexpected phenomena have recently been discovered at the nanoscale, when SrTiO₃ forms an ultrathin film or an atomically sharp interface with other materials. One of the striking discoveries is room-temperature ferroelectricity in strain-free ultrathin films of SrTiO₃ driven by the TiSr antisite defects, which generate a local dipole moment polarizing the surrounding nanoregion. Here, we demonstrate that these polar defects are not only responsible for ferroelectricity, but also propel the appearance of highly conductive channels, “hot spots”, in the ultrathin SrTiO₃ films. Using a combination of scanning probe microscopy experimental studies and theoretical modeling, we show that the hot spots emerge due to resonant tunneling through localized electronic states created by the polar defects and that the tunneling conductance of the hot spots is controlled by ferroelectric polarization. Our finding of the polarization-controlled defect-assisted tunneling reveals a new mechanism of resistive switching in oxide heterostructures and may have technological implications for ferroelectric tunnel junctions. It is also shown that the conductivity of the hot spots can be modulated by mechanical stress, opening a possibility for development of conceptually new electronic devices with mechanically tunable resistive states.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: FG02-06ER46327; AC02-05CH11231
• OSTI ID: 1484747
• Journal Information: Nano Letters, Vol. 18, Issue 1; ISSN 1530-6984
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE