Understanding the SiO2/Si interface on atomic level is an important subject for fabricating silicon based superior devices. However, despite of many studies on the SiO2/Si interface, the interfacial electronic states have been evaluated as the average, but not specifically with individual states. In the present study, we successfully observed the electronic states of particular atoms at the SiO2/Si interface for the first time, using soft X-ray absorption and emission spectroscopy. The interfacial states are noticeably different from those of the bulk SiO2 and strongly depend on the intermediate oxidation states at the interface. Furthermore, comparing the experimental results to theoretical calculations reveals the local interfacial structures.
