Figure 1

Oxygen $K$-edge absorption spectra of (a) $1.8\mathrm{nm}$ thick $\mathrm{Si}{\mathrm{O}}_2∕\mathrm{Si}\left(111\right)$ and (b) $8\mathrm{nm}$ thick $\mathrm{Si}{\mathrm{O}}_2∕\mathrm{Si}\left(111\right)$ structures. The inset shows the magnified spectrum of (a). The incident photon angle was 36° from surface normal and $p$-polarized light was used. The Auger electrons were detected at the take of angle of 54°. Note that absorption from $\mathrm{O}1s$ orbital to $\mathrm{O}2s$ orbital is forbidden due to selection rules. Thus, these absorption spectra represent unoccupied $\mathrm{O}2p$ states.Reuse & Permissions

Figure 2

(Color) $\mathrm{O}K$-edge SXE spectra for the $1.8\mathrm{nm}$ thick $\mathrm{Si}{\mathrm{O}}_2∕\mathrm{Si}\left(111\right)$ structure and the calculated $\mathrm{O}2p$ DOS obtained from the model presented in this figure. For the SXE spectra shown as the black lines, incident photon energies were (a) $537.5\mathrm{eV}$, (b) $533\mathrm{eV}$, and (c) $530\mathrm{eV}$. The incident photon angle was 60° from the surface normal and a $p$-polarized light was used. Note that in order to selectively excite P3, we used $533\mathrm{eV}$ as the incident light energy. Red lines show the calculated $\mathrm{O}2p$ DOS for (d) $\mathrm{Si}{\mathrm{O}}_2$, (e) P3 atoms of $\mathrm{Si}{\mathrm{O}}_2∕\mathrm{Si}\left(111\right)$ interface with P3, and (f) P1 atoms of $\mathrm{Si}{\mathrm{O}}_2∕\mathrm{Si}\left(111\right)$ interface with P1. The calculated DOS spectrum was the average of each oxygen atom spectrum for amorphous $\mathrm{Si}{\mathrm{O}}_2$ and that of each interface oxygen atom spectrum in the case of P1 and P3. Gaussian broadening was applied for the $\mathrm{O}2p$ DOS using experimental and lifetime broadening (total $1.1\mathrm{eV}$). Red and yellow balls correspond to oxygen and silicon atoms, respectively.Reuse & Permissions

Figure 3

Calculated energy band-gap variation in the structures with P1 and P3 along the normal direction to the interface. The position of the topmost silicon of the substrate, shown in Fig. 2, is the set to be the origin of the distance.Reuse & Permissions