Atomic Mechanism in Layer-by-Layer Growth via Surface Reconstruction.

Layer-by-layer growth played a critical role in the fine design of novel materials and devices. Although it has been widely studied during materials synthesis, the atomic mechanism of the growth remains unclear due to the lack of direct observation at the atomic scale. Here, we report a new mode in layer-by-layer growth via surface reconstruction on MoO2 (011) by environmental transmission electron microscopy and density functional theory calculations. Our in situ environmental transmission electron microscopy results demonstrate that the layer-by-layer growth of MoO2 experiences two steps that occur in an oscillatory manner: (1) the formation of an atomic ledge by transforming a section of the reconstructed layer to the intrinsic surface layer and then (2) the spontaneous reconstruction of the newly formed intrinsic surface section. Thus, the surface reconstruction can be considered as an intermediated phase during the layer-by-layer growth of MoO2. A similar phenomenon was also observed in the MoO2 dissolution procedure.