Tuning the Built-in Electric
Field in Ferroelectric
Pb(Zr<sub>0.2</sub>Ti<sub>0.8</sub>)O<sub>3</sub> Films for Long-Term
Stability of Single-Digit Nanometer Inverted Domains
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Abstract
The emergence of new technologies, such as whole genome
sequencing
systems, which generate a large amount of data, is requiring ultrahigh
storage capacities. Due to their compactness and low power consumption,
probe-based memory devices using Pb(Zr<sub>0.2</sub>Ti<sub>0.8</sub>)O<sub>3</sub> (PZT) ferroelectric films are the ideal candidate
for such applications where portability is desired. To achieve ultrahigh
(>1 Tbit/in<sup>2</sup>) storage densities, sub-10 nm inverted
domains
are required. However, such domains remain unstable and can invert
back to their original polarization due to the effects of an antiparallel
built-in electric field in the PZT film, domain-wall, and depolarization
energies. Here, we show that the built-in electric-field can be tuned
and suppressed by repetitive hydrogen and oxygen plasma treatments.
Such treatments trigger reversible Pb reduction/oxidation activity,
which alters the electrochemistry of the Pb overlayer and compensates
for charges induced by the Pb vacancies. This tuning mechanism is
used to demonstrate the writing of stable and equal size sub-4 nm
domains in both up- and down-polarized PZT films, corresponding to
eight inverted unit-cells. The bit sizes recorded here are the smallest
ever achieved, which correspond to potential 60 Tbit/in<sup>2</sup> data storage densities