Amorphous to Polycrystalline Phase Transition in La2O3 Films Grown on a Silicon Substrate Forming Si-Doped La2O3 Films

Herein, La2O3 films are fabricated on a Si substrate without a La-Sr intermixing layer at the La2O3/Si interface using a pulsed laser deposition method. X-ray diffraction data shows only two discernible peaks of the La2O3 films: hexagonal La2O3 (10-1) and cubic La2O3 (222), indicating polycrystalline character. During film growth, the reflection high-energy electron diffraction pattern from the La2O3 surface changes from an initial column shape to a complicated distributed dot pattern with narrow lines, suggesting possible structural property changes in the La2O3 film. The occurrence of a structural transition is confirmed by high-resolution transmission electron microscopy (HRTEM), which exhibits a clear crystalline phase change from an initial approximate to 10 nm thick amorphous La2O3 film to polycrystalline La2O3 film on Si. Rutherford backscattering shows a reduced La-Si intermixing between La2O3 and Si. Furthermore, the results of X-ray photoelectron spectroscopy atomic depth profile analysis show that observation of La-silicate over the whole La2O3 film indicates that Si diffuses through whole thick La2O3 films forming Si-doped La2O3 films. This study of the well-defined structural characteristics and sharp interface of La2O3/Si will enable further understanding of high dielectric constant materials grown on Si by the introduction of advanced film growth technique.