Morphological control in the adaptive ionic layer epitaxy of ZnO nanosheets

2D nanomaterials such as graphene and transition-metal dichalcogenides, with their thickness at only one or a few atomic layers, have now been positioned at the research frontier of nanoscience and nanotechnology, thanks to their exotic physical properties dissimilar to their bulk counterpart and other dimensionalities. To date, the preparation of 2D nanomaterials with desirable thickness and appreciable size has been mostly limited to the naturally layered materials, also known as van der Waals solids. Although a number of nanosheets from non-van der Waals solids have also been prepared, the control over their size and thickness, as well as understandings of a general mechanism for 2D nucleation and growth, remain obstacles for the further development of 2D nanomaterials for various advanced applications. We recently prepared few nanometers thick, tens of microns sized ZnO nanosheets by a novel method, named adaptive ionic layer epitaxy (AILE), which employs the surfactant monolayer at the water-air interface and has the potential to become a robust and versatile strategy. In this work, we present a detailed study on the independent control over the size and thickness of nanosheets, and a revisit to our model on AILE with discussions on its relations to our experimental findings.