Properties of self-assembled ZnO nanostructures on Si and SiO2 wafers

The formation of self-assembled ZnO nanoclusters on Si and SiO₂/Si surfaces, using diblock copolymers and wet chemical processing compatible with semiconductor manufacturing, is reported. The diblock copolymers, consisting of a majority polymer (norbornene) and a minority polymer (norbornene-dicarboxcylic acid), were synthesized with a block repeat unit ratio of 400 (majority block) to 50 (minority block), to obtain spherical microphase separation for the minority block and hence a spherical morphology for the metal oxide nanoclusters. The self-assembly of the inorganic nanoparticles was achieved at room temperature in the liquid phase by incorporating ZnCl₂ precursor dopant that associates with the minority polymer, then solidifying the copolymer on the semiconductor surface, and using wet chemical processing to substitute the chlorine atoms with oxygen, and form ZnO. Fourier transform infrared (FTIR) and X-ray photoemission (XPS) spectroscopy confirmed the association of the ZnCl₂ with the minority block and the formation of ZnO after polymer treatment with the wet chemical process. Transmission electron microscopy (TEM) showed spherical morphology of the ZnO nanoclusters as targeted, and a relatively narrow size distribution ranging between 7 and 15 nm. The doped diblock copolymer was spin-cast on Si and SiO₂/Si wafers, and its photolithographic patterning, metallization, and reactive ion etching using CF₄/O₂ were developed