Surface polarity and shape-controlled synthesis of ZnO nanostructures on GaN thin films based on catalyst-free metalorganic vapor phase epitaxy

A study was conducted to investigate surface polarity and shape-controlled synthesis of zinc oxide (ZnO) nanostructures on gallium nitride (GaN) thin films, based on catalyst-free metalorganic vapor phase epitaxy (MOVPE). The synthesis reaction was based on MOVPE, due to its several significant features, such as thermodynamic-dependent growth and precise control of partial pressures of the reactants, along with impurities. It was demonstrated that these features enable the growth of high quality nanomaterials in a controlled manner. It was observed that the introduction of GaN films leads to selective growth of ZnO nanostructures on the top of hillocks. It was also observed that decreasing the ZnO feeding ratios enables ZnO nanostructures, ranging from smooth-surfaced nanorod-nanowell networks with non-polar planes as side faces, to corrugated and stacked pyramid-structured nanorods terminated with O-polar and planes.