title: Surface of room-temperature-stable electride [Ca24Al28O64]4+(e-)4: preparation and its characterization by atomic-resolution scanning tunneling microscopy.
abstract: The nanocage compound crystal [Ca24Al28O64]4+(e-)4 (C12A7:e-) is a room-temperature-stable electride. Although bulk C12A7:e- exhibits metallic conduction, the surface of an as-prepared sample or one prepared by mechanical fracture in ultrahigh vacuum is almost insulating and exhibits distinct non-ohmic contact. We studied whether the intrinsic surface of this electride exhibits metallic conduction or not by examining various conditions for preparing the intrinsic surface. A combination of sputtering with thermal annealing led to the emergence of metallic conductivity in a specific condition. Suitably prepared surfaces revealed ohmic contact even in an ambient atmosphere. Atomic-resolution scanning tunneling microscopy (STM) images of the surfaces were consistent with a structural model in which the cage structure in the bulk C12A7:e- electride is conserved at the surface.
authors.affiliation: Frontier Research Center and Material and Structure Laboratory, Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Toda
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Kubota
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hirano
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hirayama
authors.forename: Hideo
authors.initials: H
authors.lastname: Hosono
mesh_terms: D017607:Aluminum Compounds / Q000138:chemical synthesis*; D017610:Calcium Compounds / Q000138:chemical synthesis*; D004553:Electric Conductivity; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D016252:Microscopy, Scanning Tunneling / Q000379:methods*; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013499:Surface Properties; D013696:Temperature
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D046911:Macromolecular Substances; C035219:calcium aluminate