A thin diffusion barrier was self-formed by annealing at an interface between a Cu-Mn alloy film and a SiO2 substrate. The growth of the barrier layer followed a logarithmic rate law, which represents field-enhanced growth mechanism in the early stage and self-limiting growth behavior in the late stage. The barrier layer was stable at 450 °C for 100 h and at 600 °C for 10 h. The interface diffusivity was estimated from the morphology change of the barrier layer at 600 °C and was found to be smaller than the grain-boundary diffusivity of bulk Cu.

The thermal diffusion of germanium and oxygen atoms in HfO2/GeO2/Ge gate stacks was comprehensively evaluated by x-ray photoelectron spectroscopy and secondary ion mass spectrometry combined with an isotopic labeling technique. It was found that 18O-tracers composing the GeO2 underlayers diffuse within the HfO2 overlayers based on Fick's law with the low activation energy of about 0.5 eV. Although out-diffusion of the germanium atoms through HfO2 also proceeded at the low temperatures of around 200 °C, the diffusing germanium atoms preferentially segregated on the HfO2 surfaces, and the reaction was further enhanced at high temperatures with the assistance of GeO desorption. A technique to insert atomically thin AlOx interlayers between the HfO2 and GeO2 layers was proven to effectively suppress both of these independent germanium and oxygen intermixing reactions in the gate stacks.

Organized two-dimensional Ti-SiO 2 metal quantum dot composites induced by subplantation A self-forming diffusion barrier ͑SFB͒ layer was formed at Cu-Mn/ SiO 2 interface. Spatial variation of the chemical composition and valence state of the elements in the SFB was investigated in a subnanometer resolution using electron energy loss spectroscopy and transmission electron microscopy. The SFB was found to have a layered structure with graded compositions of nanocrystalline MnO and amorphous MnSiO 3 . The valence state of Mn was found to be +2 in the MnO layer and gradually increased to +3 in the MnSiO 3 layer. The reported dielectric constant of the SFB could be explained by the observed composition and microstructure.

We measured cathodoluminescence (CL) spectra of SiO2 films grown on 4H-SiC wafers and found that for an acceleration voltage of 5 kV, CL peaks at 460 and 490 nm, assigned to oxygen vacancy centers (OVCs), become weak by post-oxidation annealing in N2O ambient at 1300 °C whereas the CL peak around 580 nm, related to Si-N bonding structures, becomes intense. Furthermore, the peak assigned to N-Si3 configurations in x-ray photoelectron spectroscopy (XPS) spectra was observed in the SiO2/SiC interface in only samples annealed in N2O ambient. These results suggest that the interface trap densities decrease and the channel mobility in n-type MOS capacitors increases by the termination of dangling bonds by the N atom in the SiO2/SiC interface. CL spectroscopy and XPS provide us with extensive information on OVCs and dangling bonds in the SiO2/SiC interface on the 4H-SiC substrate.

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