Direct observations of Ca ordering in Ca0.33CoO2 thin films with different superstructures

作者：Huang Rong^*; Mizoguchi Teruyasu; Sugiura Kenji; Ohta Hiromichi; Koumoto Kunihito; Hirayama Tsukasa; Ikuhara Yuichi

来源：Applied Physics Letters, 2008, 93(18): 181907.

DOI：10.1063/1.3021369

• calcium compounds
• epitaxial layers
• ion exchange
• scanning electron microscopy
• solid phase epitaxial growth
• vacancies (crystal)

Ca-ion superstructures such as root 3a X root 3a (hexagonal) and 2a X root 3a (orthorhombic) in layered Ca0.33CoO2 crystalline film, which were prepared by the reactive solid-phase epitaxy and the subsequent ion-exchange treatment, were directly distinguished by using spherical-aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The fluctuation of Ca intensities in the HAADF-STEM image indicates the existence of many Ca vacancies in the 2a X root 3a orthorhombic superstructure, which is consistent with the partial occupation of Ca (x=0.33) in the cation sites of x=0.5.

• 出版日期2008-11-3