Abstract
Direct, atomic-scale visualization of polarization switching in a functional, polycrystalline, binary oxide via insitu high-resolution transmission electron microscopy (HRTEM) biasing is reported for the first time. Antiferroelectric (AFE) ZrO2 was used as the model system, which is important for commercial DRAMs and as emerging NVMs (through work-function engineering). We observed (1) clear shifting and coalescing of domains within a single grain, and (2) dramatic changes of the atomic arrangements and crystalline phases-both at voltages above the critical voltage measured for AFE switching. Similar synergistic in-situ structural-electrical characterization can pave the way to understand and engineer microscopic mechanisms for retention, fatigue, variability, sub-coercive switching and analog states in ferroelectric and AFE-based memory devices.
| Original language | English |
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| Title of host publication | 2020 IEEE Symposium on VLSI Technology, VLSI Technology 2020 - Proceedings |
| Publisher | Institute of Electrical and Electronics Engineers Inc. |
| ISBN (Electronic) | 9781728164601 |
| DOIs | |
| State | Published - Jun 2020 |
| Event | 2020 IEEE Symposium on VLSI Technology, VLSI Technology 2020 - Honolulu, United States Duration: Jun 16 2020 → Jun 19 2020 |
Publication series
| Name | Digest of Technical Papers - Symposium on VLSI Technology |
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| Volume | 2020-June |
| ISSN (Print) | 0743-1562 |
Conference
| Conference | 2020 IEEE Symposium on VLSI Technology, VLSI Technology 2020 |
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| Country/Territory | United States |
| City | Honolulu |
| Period | 06/16/20 → 06/19/20 |
Funding
Zoomed-in images of the same area obtained from the HRTEM images show a rectangular arrangement of Zr atoms (Fig. 6). When 0V images are superimposed with Zr atoms along the (112ത) projection (which is perpendicular to the growth direction, i.e., [111]) of the tetragonal P42/nmc phase, an excellent (but not necessarily unique) match is observed (Fig. 7). When voltage is applied, a ‘sudden’ appearance of additional face-centered atoms in half of the rectangles occurs, indicating a partial phase transformation (Fig. 8b). Suggested (but not unique) atomic arrangements of the two phases at 4V are shown in Fig. 8. These changes were observed in each subsequent cycle (i.e., 0V4V0V4V, Fig. 9). Conclusions: We studied micro-structural evolution during polarization switching in AFE ZrO2 via in-situ HRTEM probing. Our study is the first of its kind for fluorite-type binary FEs/AFEs that can provide correlation between structural and electrical features for understanding and engineering the microscopic mechanisms behind fatigue, retention, endurance, reliability and variability, sub-coercive switching, analog states and so on for VLSI memory applications. Acknowledgements: This work was supported by ASCENT, one of six JUMP centers, an SRC program sponsored by DARPA, and the SRC GRC program. A part of the work was conducted at CNMS, a DOE Office of Science User Facility.