Enhanced ferroelectricity in ultrathin films grown directly on silicon

Suraj S. Cheema, Daewoong Kwon, Nirmaan Shanker, Roberto dos Reis, Shang Lin Hsu, Jun Xiao, Haigang Zhang, Ryan Wagner, Adhiraj Datar, Margaret R. McCarter, Claudy R. Serrao, Ajay K. Yadav, Golnaz Karbasian, Cheng Hsiang Hsu, Ava J. Tan, Li Chen Wang, Vishal Thakare, Xiang Zhang, Apurva Mehta, Evguenia KarapetrovaRajesh V. Chopdekar, Padraic Shafer, Elke Arenholz, Chenming Hu, Roger Proksch, Ramamoorthy Ramesh, Jim Ciston, Sayeef Salahuddin

Research output: Contribution to journalArticlepeer-review

517 Scopus citations


Ultrathin ferroelectric materials could potentially enable low-power perovskite ferroelectric tetragonality logic and nonvolatile memories1,2. As ferroelectric materials are made thinner, however, the ferroelectricity is usually suppressed. Size effects in ferroelectrics have been thoroughly investigated in perovskite oxides—the archetypal ferroelectric system3. Perovskites, however, have so far proved unsuitable for thickness scaling and integration with modern semiconductor processes4. Here we report ferroelectricity in ultrathin doped hafnium oxide (HfO2), a fluorite-structure oxide grown by atomic layer deposition on silicon. We demonstrate the persistence of inversion symmetry breaking and spontaneous, switchable polarization down to a thickness of one nanometre. Our results indicate not only the absence of a ferroelectric critical thickness but also enhanced polar distortions as film thickness is reduced, unlike in perovskite ferroelectrics. This approach to enhancing ferroelectricity in ultrathin layers could provide a route towards polarization-driven memories and ferroelectric-based advanced transistors. This work shifts the search for the fundamental limits of ferroelectricity to simpler transition-metal oxide systems—that is, from perovskite-derived complex oxides to fluorite-structure binary oxides—in which ‘reverse’ size effects counterintuitively stabilize polar symmetry in the ultrathin regime.
Original languageEnglish (US)
Pages (from-to)478-482
Number of pages5
Issue number7804
StatePublished - Apr 22 2020
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-06-14
Acknowledged KAUST grant number(s): OSR-2016-CRG5-2996
Acknowledgements: Acknowledgements This research was supported in part by the Berkeley Center for Negative Capacitance Transistors (BCNCT), ASCENT (Applications and Systems-Driven Center for Energy-Efficient Integrated NanoTechnologies), one of the six centres in the JUMP initative (Joint University Microelectronics Program), an SRC (Semiconductor Research Corporation) programme sponsored by DARPA, the DARPA T-MUSIC (Technologies for Mixed-mode Ultra Scaled Integrated Circuits) programme and the UC MRPI (University of California Multicampus Research Programs and Initiatives) project. This research used resources of the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract number DE-AC02-06CH11357. This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract number DE-AC02-05CH11231. Use of the Stanford Synchrotron Radiation Light source, SLAC National Accelerator Laboratory, is supported by the US DOE, Office of Science, Office of Basic Energy Sciences under contract number DE-AC02-76SF00515. Electron microscopy was performed at the Molecular Foundry, LBNL, supported by the Office of Science, Office of Basic Energy Sciences, US DOE (DE-AC02-05CH11231). J.C. and R.d.R. acknowledge additional support from the Presidential Early Career Award for Scientists and Engineers (PECASE) through the US DOE. J.X and X.Z acknowledge support from the National Science Foundation (NSF) under grant 1753380 and the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research award OSR-2016-CRG5-2996.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

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