Continuous advancement in nonvolatile and morphotropic beyond-Moore electronic devices requires integration of ferroelectric and semiconductor materials. The emergence of hafnium oxide (HfO 2 )–based ferroelectrics that are compatible with atomic-layer deposition has opened interesting and promising avenues of research. However, the origins of ferroelectricity and pathways to controlling it in HfO 2 are still mysterious. We demonstrate that local helium (He) implantation can activate ferroelectricity in these materials. The possible competing mechanisms, including He ion–induced molar volume changes, vacancy redistribution, vacancy generation, and activation of vacancy mobility, are analyzed. These findings both reveal the origins of ferroelectricity in this system and open pathways for nanoengineered binary ferroelectrics.

By controlling the configuration of polymorphic phases in high‐k Hf0.5Zr0.5O2 thin films, new functionalities such as persistent ferroelectricity at an extremely small scale can be exploited. To bolster the technological progress and fundamental understanding of phase stabilization (or transition) and switching behavior in the research area, efficient and reliable mapping of the crystal symmetry encompassing the whole scale of thin films is an urgent requisite. Atomic‐scale observation with electron microscopy can provide decisive information for discriminating structures with similar symmetries. However, it often demands multiple/multiscale analysis for cross‐validation with other techniques, such as X‐ray diffraction, due to the limited range of observation. Herein, an efficient and automated methodology for large‐scale mapping of the crystal symmetries in polycrystalline Hf0.5Zr0.5O2 thin films is developed using scanning probe‐based diffraction and a hybrid deep convolutional neural network at a 2 nm2 resolution. The results for the doped hafnia films are fully proven to be compatible with atomic structures revealed by microscopy imaging, not requiring intensive human input for interpretation.

Constructing a mono-atom step-level ultra-flat material surface is challenging, especially for thin films, because it is prohibitively difficult for trillions of clusters to coherently merge. Even though a rough metal surface, as well as the scattering of carriers at grain boundaries, limits electron transport and obscures their intrinsic properties, the importance of the flat surface has not been emphasised sufficiently. In this study, we describe in detail the initial growth of copper thin films required for mono-atom step-level flat surfaces (MSFSs). Deposition using atomic sputtering epitaxy leads to the coherent merging of trillions of islands into a coplanar layer, eventually forming an MSFS, for which the key factor is suggested to be the individual deposition of single atoms. Theoretical calculations support that single sputtered atoms ensure the formation of highly aligned nanodroplets and help them to merge into a coplanar layer. The realisation of the ultra-flat surfaces is expected to greatly assist efforts to improve quantum behaviour by increasing the coherency of electrons.

The intrinsic nature of electronic transport has been screened by the carrier scattering at grain boundaries in two-dimensional noble metals, such as copper. Here, by realizing the impossible assumption of growing without grain boundaries in thin films, we demonstrate that the transport by hole carriers in 2D copper is the intrinsic nature, which has been screened by the scattering of carriers at grain boundaries. Unlike the grain boundaries, twin boundaries are invisible to conduction carriers, but even a slight tilt from regular twin boundaries is recognized as grain boundaries to electrons, so only complete suppression of grain boundaries can reveal the hidden hole-like characteristic of 2D-single crystal copper. The hole carriers can be explained by the concave Fermi surface of the 2D single-crystal copper, which suggests a breakthrough in manipulating the polarity of majority carriers in metals based on grain boundary engineering in a 2D geometry.

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