Study of the SiO2-Si Interface Using Variable Energy Positron Two-Dimensional Angular Correlation of Annihilation Radiation

The defect structure of the Si${\mathrm{O}}_2$-Si interface has been studied using variable energy positron two-dimensional angular correlation of annihilation radiation (2D-ACAR). As the first depth-resolved 2D-ACAR measurement, unique information about this interface was obtained: The formation and trapping of positronium atoms are observed at the microvoids ( $\sim 10Å$ in size) in the oxide and interface regions. Positron trapping and annihilation at the $P_b$ centers in the interface region are inferred. The existence of the microvoids in the interface region is beyond the current interface model, and the results may have a profound impact on the understanding of the interface growth.