The oxidation behavior of 0.6 and 1.1 ML hafnium on Si(001) was studied by using scanning reflection electron microscopy with in situ x-ray photoelectron spectroscopy. The submonolayer sample was designed to purposely grow SiO2 on the partially exposed surfaces, and was compared with a 1.1 ML sample to discriminate the structural and chemical differences between the two samples. This approach revealed that oxygen ions were likely to form Si-O and Hf-O bonding units separately at 400 °C in 2×10-6 Torr oxygen, but at 700 °C in 5×10-5 Torr oxygen, the bonding priority of oxygen ions transforms into Hf-O-Si bonding units implying silicate formation by Si migration. Despite silicate formation, ∼0.27-nm-thick SiO2-like layer is believed to have remained underneath silicate layers.
Physical Review B
- Pub Date:
- December 2002
- Composition and phase identification;
- Scanning electron microscopy;
- Low-energy electron diffraction and reflection high-energy electron diffraction