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While it is well established that elevated temperatures can induce surface roughening of metal surfaces, the effect of a high electric field on the atomic structure at ambient temperature has not been investigated in detail. Here we show with atomic resolution using in situ transmission electron microscopy how intense electric fields induce reversible switching between perfect crystalline and disordered phases of gold surfaces at room temperature. Ab initio molecular dynamics simulations reveal that the mechanism behind the structural change can be attributed to a vanishing energy cost in forming surface defects in high electric fields. Our results demonstrate how surface processes can be directly controlled at the atomic scale by an externally applied electric field, which promotes an effective decoupling of the topmost surface layers from the underlying bulk. This opens up opportunities for development of active nanodevices in e.g. nanophotonics and field-effect transistor technology as well as fundamental research in materials characterization and of yet unexplored dynamically-controlled low-dimensional phases of matter., Comment: The manuscript is 10 pages long and the supplemental material is 15 pages. There are six supplemental movies that can be provided upon request to LDK

Oxide films play a significant role in a wide range of industrial fields, mostly due to the thickness-dependent variation of their properties. Recently, it has been proposed based on the experimental study that carrier transport in CaO films proceeds via strong phonon excitations with a variable signal depending on the film thickness. In this paper, we report a detailed investigation in the frame of the density functional theory of structural and electronic properties of freestanding and Mo(100)-supported CaO films, as well as phonons therein, as functions of the film thickness and intensity of the external static electric field. Our calculations demonstrate that phonon frequencies negligibly depend on the external electric field. A small gradual increase of the energy of CaO phonons upon increase of the film thickness was found to be in line with earlier experimental findings. The effect of Mo support was observed in the systematic decrease of the energy of phonons. The applied electric field showed a minor effect on the structure of CaO films, whereas electronic properties of the oxide were significantly affected. In particular, the band gap of CaO films was found to gradually decrease with the growing intensity of the external electric field, while the effect is a more pronounced for thicker films. Overall, our paper provides innovative insights into the mechanism of electron transport and electronic properties of CaO films that might lead to new potential applications of oxide materials. peerReviewed