title: Microstructural evolution of ZnO by wet-etching using acidic solutions.
abstract: The characteristics of the wet-etching of ZnO thin films were investigated using hydrochloric and phosphoric acid solutions as etchants. The etch rate of ZnO films, using a highly diluted hydrochloric acid solutions at a concentration of 0.25% in deionized water, was determined to be about 120 nm/min, and linearly increased with increasing the acid concentration. The surface of ZnO(0001) etched by an HCl solution, observed by scanning electron microscopy, showed a rough morphology with a high density of hexagonal pyramids or cones with sidewall angles of about approximately 45 degrees. Moreover, the sidewall angles of the masked area were similar to those of the pyramids on the surface. In comparison, the surface of ZnO(0001) etched by a phosphoric acid had a smooth surface morphology. The origin of this difference is from the very initial stage of etching, indicating that the etch-mechanism is different for each solution. Furthermore, when H3PO4 was added to the HCl aqueous solution, the morphology of the etched surface was greatly enhanced and the sidewall angle was also increased to about 65 degrees.
authors.affiliation: Department of Materials Science and Metallurgical Engineering, Sunchon National University, Suncheon, Jeonnam 540-742, Korea.
authors.forename: Ji-Myon
authors.initials: JM
authors.lastname: Lee
authors.forename: Kyoung-Kook
authors.initials: KK
authors.lastname: Kim
authors.forename: Chan-Kyung
authors.initials: CK
authors.lastname: Hyun
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tampo
authors.forename: Shigeru
authors.initials: S
authors.lastname: Niki
mesh_terms: D000143:Acids / Q000737:chemistry*; D006851:Hydrochloric Acid / Q000737:chemistry; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D010756:Phosphoric Acids / Q000737:chemistry; D013696:Temperature; D014867:Water / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D000143:Acids; D010756:Phosphoric Acids; D014867:Water; C030242:phosphoric acid; D006851:Hydrochloric Acid; D015034:Zinc Oxide