Structural and charge trapping properties of two bilayer (Ge+SiO2)/SiO2 films deposited on rippled substrate

We report on structural properties and charge trapping in [(Ge+SiO2)/SiO2]×2 films deposited by magnetron sputtering on a periodically corrugated-rippled substrate and annealed in vacuum and forming gas. The rippled substrate caused a self-ordered growth of Ge quantum dots, while annealing in different environments enabled us to separate charge trapping in quantum dots from the trapping at the dot-matrix and matrix-substrate interfaces. We show that the charge trapping occurs mainly in Ge quantum dots in the films annealed in the forming gas, while Si-SiO2 interface trapping is dominant for the vacuum annealed films.