Structure analysis of new homologous compounds Ga2O3(ZnO) m (m = integer) by high-resolution analytical transmission electron microscopy

Abstract

The crystal structure of a new homologous compound series, Ga2O3(ZnO) m (m = integer), is determined by high-resolution lattice imaging and high spatial resolution energy-dispersive X-ray spectroscopy (EDS) analysis in a field-emission analytical transmission electron microscope. This work was carried out mainly on the compound with m = 9 (digallium nonazinc dodecaoxide), which belongs to the orthorhombic system and has lattice constants ao = 0.33, bo = 2.0 and co = 3.4 nm. From the extinction rules three possible space groups are selected and from them a unique space group is assigned as noncentrosymmetric Cmc21 (No. 36) on the basis of structural requirements. Ga2O3(ZnO) m is a layered structure consisting of Ga–O and m + 1 Ga/Zn–O layers stacked alternately along the c axis. It is shown that the structure of Ga2O3(ZnO) m differs from that of M 2O3(ZnO) m (M = In, Fe; m = integer) reported previously. In Ga2O3(ZnO) m the Ga atoms occupy the tetrahedral sites in the Ga–O layers, whereas the M atoms in the M–O layers occupy the octahedral sites in M 2O3(ZnO) m (M = In, Fe).