Substrate dependent growth modes of ZnO nanorods grown by metalorganic chemical vapor deposition

Transmission electron microscopy studies were performed to reveal the underlying growth modes of ZnO nanorods by metalorganic chemical vapor deposition with respect to the type of substrates. On well-matched substrates, such as GaN/Al2O3 (0001) and ZnO (0001) substrates, a 2-dimensional (D) layer-by-layer growth occurs. During further growth after a certain critical thickness of ∼40 nm, 1D nanorods start to grow on the 2D layer. In contrast, only vertically-aligned ZnO nanorods grow on a partially-matched substrate, such as Al2O3 (0001), after the coalescence of 3D ZnO islands. On mismatched substrates, such as Si (111) and Si (001), an Si–O amorphous layer of ∼5 nm forms first, on which 3D ZnO islands grow. After their coalescence, 1D nanorods start to grow.

► Growth modes of ZnO nanorods are studied with respect to the type of substrates.
► For ZnO nanorods, a layer-by-layer growth occurs on well-matched substrates.
► Only vertically-aligned ZnO nanorods grow on a partially-matched substrate.
► 3D ZnO islands grow on mismatched substrates.