Quadrupole Hyperfine Interactions in Si-Hf-O Systems Subjected to High Energy Ball Milling

CECILIA Y. CHAIN; SERGIO FERRAI; LAURA C. DAMONTE; JORGE A. MARTINEZ; ALBERTO F. PASQUEVICH

Gijón

Simposio; 18th International Symposium on Metastable, Amorphous and Nanostructured Materials; 2011

Universidad de Oviedo

Hafnia (HfO2) appears as a good candidate to replace silica (SiO2) in Si complementary metal-oxide-semiconductor devices due to its hardness, its high dielectric constant and its wide band gap. It has been reported that the mixture of silica with hafnia (or zirconia) exhibits excellent electrical properties and high thermal stability in direct contact with Si. This fact makes the study of the solid-state reactions between SiO2 and HfO2 of great interest. Being the Perturbed Angular Correlation (PAC) technique a very sensitive method to detect small changes in solid state, the goal of this work is to follow the different stages that occur while preparing Si-Hf-O systems by mechanical milling using different raw materials by inspecting the hyperfine quadrupole interactions at Hf sites in the mixtures. The evolution of the hyperfine quadrupole interactions at hafnium sites in equimolar mixtures of HfO2‑Si and HfO2-SiO2 was measured after different milling times. The characterization was complemented by X-ray diffraction (XRD) analysis. PAC results revealed that mechanical milling produces nanocrystalline defective phases. The damage and/or distortion of the HfO2 lattice produced by the milling process are more important for the blends HfO2‑Si than those for HfO2-SiO2. As milling proceeds, the evolution of the hyperfine interactions reveals the degree of atomic mixing that occur in both blends. The obtained results will be discussed in terms of different known hyperfine interactions.