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 Chopdekar, Padraic Shafer, Elke Arenholz, Chenming Hu, Roger Proksch, Ramamoorthy Ramesh, Jim Ciston, Sayeef Salahuddin

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

Ultrathin ferroelectric materials could potentially enable low-power perovskite ferroelectric tetragonality logic and nonvolatile memories(1,2). 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 system(3). Perovskites, however, have so far proved unsuitable for thickness scaling and integration with modern semiconductor processes(4). 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.

Enhanced switchable ferroelectric polarization is achieved in doped hafnium oxide films grown directly onto silicon using low-temperature atomic layer deposition, even at thicknesses of just one nanometre.

Original languageEnglish
Pages (from-to)478-+
Number of pages20
JournalNature
Volume580
Issue number7804
DOIs
StatePublished - Apr 2020

Keywords

  • THIN-FILMS
  • GATE OXIDES
  • POLARIZATION
  • NANOSCALE
  • ORIGIN

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