Ferroelectrics everywhere: Ferroelectricity in magnesium substituted zinc oxide thin films

We demonstrate ferroelectricity in Mg-substituted ZnO thin films with the wurtzite structure. Zn1−xMgxO films are grown by dual-cathode reactive magnetron sputtering on (111)-Pt // (0001)-Al2O3 substrates at temperatures ranging from 26 to 200 °C for compositions spanning from x = 0 to x = 0.37. X-ray diffraction indicates a decrease in the c-lattice parameter and an increase in the a-lattice parameter with increasing Mg content, resulting in a nearly constant c/a axial ratio of 1.595 over this composition range. Transmission electron microscopy studies show abrupt interfaces between Zn1−xMgxO films and the Pt electrode. When prepared at pO2 = 0.025, film surfaces are populated by abnormally oriented grains as measured by atomic force microscopy for Mg concentrations >29%. Raising pO2 to 0.25 eliminates the misoriented grains. Optical measurements show increasing bandgap values with increasing Mg content. When prepared on a 200 °C substrate, films display ferroelectric switching with remanent polarizations exceeding 100 μC cm−2 and coercive fields below 3 MV cm−1 when the Mg content is between ∼30% and ∼37%. Substrate temperature can be lowered to ambient conditions, and when doing so, capacitor stacks show only minor sacrifices to crystal orientation and nearly identical remanent polarization values; however, coercive fields drop below 2 MV/cm. Using ambient temperature deposition, we demonstrate ferroelectric capacitor stacks integrated directly with polymer substrate surfaces.

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Work Title Ferroelectrics everywhere: Ferroelectricity in magnesium substituted zinc oxide thin films
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Open Access
Creators
  1. Kevin Ferri
  2. Saiphaneendra Bachu
  3. Wanlin Zhu
  4. Mario Imperatore
  5. John Hayden
  6. Nasim Alem
  7. Noel Giebink
  8. Susan E. Trolier-McKinstry
  9. Jon-Paul Maria
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. Journal of Applied Physics
Publication Date July 28, 2021
Publisher Identifier (DOI)
  1. https://doi.org/10.1063/5.0053755
Deposited December 08, 2021

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  • Added Ferroelectrics_Everywhere_-_Ferroelectrticity_in_Magnesium_Substituted_Zinc_Oxide_Thin_Films-JAP-2021.pdf
  • Added Creator Kevin Ferri
  • Added Creator Saiphaneendra Bachu
  • Added Creator Wanlin Zhu
  • Added Creator Mario Imperatore
  • Added Creator John Hayden
  • Added Creator Nasim Alem
  • Added Creator Noel Giebink
  • Added Creator Susan E. Trolier-McKinstry
  • Added Creator Jon-Paul Maria
  • Published
  • Updated
  • Updated