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Achieving stable single-digit nanometer inverted domains in ferroelectric thin films is a fundamental issue that has remained a bottleneck for the development of ultrahigh density (>1 Tbit/in.2) probe-based memory devices using ferroelectric media. Here, we demonstrate that such domains remain stable only if they are fully inverted through the entire ferroelectric film thickness, which is dependent on a critical ratio of electrode size to the film thickness. This understanding enables the formation of stable domains as small as 4 nm in diameter, corresponding to 10 unit cells in size. Such domain size corresponds to 40 Tbit/in.2 data storage densities. [ABSTRACT FROM AUTHOR]

The emergence of new technologies, such as whole genomesequencingsystems, which generate a large amount of data, is requiring ultrahighstorage capacities. Due to their compactness and low power consumption,probe-based memory devices using Pb(Zr0.2Ti0.8)O3(PZT) ferroelectric films are the ideal candidatefor such applications where portability is desired. To achieve ultrahigh(>1 Tbit/in2) storage densities, sub-10 nm inverteddomainsare required. However, such domains remain unstable and can invertback to their original polarization due to the effects of an antiparallelbuilt-in electric field in the PZT film, domain-wall, and depolarizationenergies. Here, we show that the built-in electric-field can be tunedand 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 compensatesfor charges induced by the Pb vacancies. This tuning mechanism isused to demonstrate the writing of stable and equal size sub-4 nmdomains in both up- and down-polarized PZT films, corresponding toeight inverted unit-cells. The bit sizes recorded here are the smallestever achieved, which correspond to potential 60 Tbit/in2data storage densities. [ABSTRACT FROM AUTHOR]