Atomic-scale investigation of spinel Li Fe5O8 thin films on SrTiO3(001) substrates

Microstructural properties of spinel Li Fe5O8(LFO)films grown on(001)-oriented Sr TiO3(STO)substrates have been investigated at the atomic-scale by advanced electron microscopy techniques.Two types of orientation relationship(OR)between the LFO films and the STO substrates have been determined,cube-on-cube and(111)[ī10]LFO//(111)[1ī0]STO.Antiphase boundaries(APBs)and three types of twin boundaries(TBs)form within the LFO films,and the propagation of TBs and APBs results in their complex interactions.In most cases,interactions between TBs and APBs change the type of TBs and terminate the propagation of APBs since the APBs introduce a displacement vector of(a/4)110 into the TBs.In addition,the interactions between two coherent TBs are observed to generate the incoherent TB.The epitaxial strain of the LFO/STO(001)heterosystem can be released by the formation of TBs and APBs in the films and misfit dislocations at the interface.Considering that the magnetic coupling across the APBs and TBs can lead to novel physical properties,the appearance of APBs and TBs with a high density in the LFO films would affect the magnetic properties of the films.

Microstructure and secondary phases in epitaxial LaBaCo_2O_(5.5 + δ) thin films

Aberration-corrected scanning transmission electron microscopy was employed to investigate the microstructures and secondary phases in LaBaCo2O5.5＋δ（LBCO） thin films grown on SrTiO3 （STO） substrates. The as-grown films showed an epitaxial growth on the substrates with atomically sharp interfaces and orientation relationships of [100]LBCO//[100]STO and （001）LBCO//（001）STO. Secondary phases were observed in the films, which strongly depended on the sample fabrication conditions. In the film prepared at a temperature of 900 ℃, nano-scale CoO pillars nucleated on the substrate, and grew along the [001] direction of the film. In the film grown at a temperature of 1000 ℃, isolated nano-scale C0304 particles appeared, which promoted the growth of {111 } twinning structures in the film. The orientation relationships and the interfaces between the secondary phases and the films were illustrated, and the growth mechanism of the film was discussed.