Transmission electron microscopy studies on structure and defects in crystalline yttria and lanthanum oxide thin films grown on single crystal sapphire by molecular beam synthesis

Abstract

The Molecular beam synthesis and characterization are reported for Y 2O3 thin films grown on Al2O3 (0001) substrate. The Y2O3 layer was highly oriented in the [111] direction with predominant orientation relations (111) Y2O 3 ∥ (0001) Al2O3 and [11̄0] Y 2O3 ∥ [2̄110] Al2O3, corresponding to a lattice mismatch of ∼20% at the interface. No significant interfacial layers were found at the Y2O3/Al 2O3 interface and the large lattice misfit was accommodated by formation of stacking faults, dislocations and secondary orientation in the Y2O3 layer. A La2O 3 interlayer improved the quality of the Y2O3 films. Full width at half maximum (FWHM) of the Y2O3 (222) peak decreased from 3.12° to 1.43° and the defect density in the Y 2O3 layer was significantly reduced. These results may be relevant in the broader context of designing oxide heterolayers with controlled microstructures. © 2010 Taylor & Francis.