Selective Growth of ZnO Nanosheets via Ionic Layer Epitaxy for UV Photodetection Application

Zinc oxide (ZnO) nanosheets have shown great promise for ultraviolet (UV) photodetectors due to their excellent optoelectronic properties and atomically thin structure. Surfactant-assisted ionic layer epitaxy (ILE) is a simple and scalable technique for synthesizing monolayered ZnO nanosheets; however, the formation of a byproduct is inevitable and detrimental for optoelectronic device applications. This study demonstrates a rational strategy for the selective growth of ZnO nanosheets in ILE growth without byproduct formation. The detailed investigation revealed that the formation of byproducts originates from surfactant-induced heterogeneous nucleation. We found that increasing the surfactant concentration suppresses the byproduct formation by localizing the zinc precursor at the water–air interface and opens a concentration window for promoting nanosheet growth. By precise control of the zinc precursor concentration within the concentration window, a selective growth of ca. 1-nm-thick ZnO nanosheets was successfully achieved. A device composed of a single ZnO nanosheet demonstrated a fast-response UV photodetection (rise time/recovery time = 12.3 ms/24.7 ms), which is shorter than the previously reported ZnO nanosheet devices.