title: Electronic structure of the muonium center as a shallow donor in ZnO.
abstract: The electronic structure and the location of muonium centers (Mu) in single-crystalline ZnO were determined for the first time. Two species of Mu centers with extremely small hyperfine parameters have been observed below 40 K. Both Mu centers have an axial-symmetric hyperfine structure along with a <0001> axis, indicating that they are located at the antibonding (AB(O, parallel )) and bond-center (BC( parallel )) sites. It is inferred from their small ionization energy ( approximately 6 and 50 meV) and hyperfine parameters ( approximately 10(-4) times the vacuum value) that these centers behave as shallow donors, strongly suggesting that hydrogen is one of the primary origins of n type conductivity in as-grown ZnO.
authors.affiliation: Meson Science Laboratory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Shimomura
authors.forename: Kusuo
authors.initials: K
authors.lastname: Nishiyama
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kadono