title: Identification of ultradilute dopants in ceramics.
abstract: The properties of ceramic materials are strongly influenced by the presence of ultradilute impurities (dopants). Near-edge X-ray absorption fine structure (NEXAFS) measurements using third-generation synchotron sources can be used to identify ultradilute dopants, provided that a good theoretical tool is available to interpret the spectra. Here, we use NEXAFS analysis and first-principles calculations to study the local environments of Ga dopants at levels of 10 p.p.m in otherwise high-purity MgO. This analysis suggests that the extra charge associated with substitutional Ga on a Mg site is compensated by the formation of a Mg vacancy. This defect model is then confirmed by positron lifetime measurements and plane-wave pseudopotential calculations. This powerful combination of techniques should provide a general method of identifying the defect states of ultradilute dopants in ceramics.
authors.affiliation: Department of Materials Science and Engineering, Kyoto University, Sakyo, Kyoto 606-8501 Japan. itanaka@MTL.kyoto-u.ac.jp
authors.forename: Isao
authors.initials: I
authors.lastname: Tanaka
authors.forename: Teruyasu
authors.initials: T
authors.lastname: Mizoguchi
authors.forename: Masafumi
authors.initials: M
authors.lastname: Matsui
authors.forename: Satoru
authors.initials: S
authors.lastname: Yoshioka
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Adachi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Okajima
authors.forename: Masanori
authors.initials: M
authors.lastname: Umesaki
authors.forename: Wai Yim
authors.initials: WY
authors.lastname: Ching
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Inoue
authors.forename: Masataka
authors.initials: M
authors.lastname: Mizuno
authors.forename: Hideki
authors.initials: H
authors.lastname: Araki
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Shirai
mesh_terms: D002516:Ceramics / Q000032:analysis / Q000737:chemistry; D003198:Computer Simulation; D003461:Crystallography / Q000379:methods; D005708:Gallium / Q000032:analysis* / Q000737:chemistry; D008277:Magnesium Oxide / Q000032:analysis* / Q000737:chemistry; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D008832:Microchemistry / Q000295:instrumentation / Q000379:methods; D008958:Models, Molecular; D012666:Semiconductors; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D008277:Magnesium Oxide; D005708:Gallium