Figure 3

Si 2 p XPS spectra of samples 1, 2, 3, and 4 with varying thicknesses. (a) Sample 1 with Al₂O₃ thickness of 1.3 nm. (b) Sample 2 with Al₂O₃ thickness of 1.98 nm. (c) Sample 3 with Al₂O₃ thickness of 2.32 nm. (d) Sample 4 with Al₂O₃ thickness of 3.59 nm. The black solid line represents the original data of Si 2p spectrum; the red solid line is for the fitting curve. The blue dash line stands for the Gaussian peak of Si-C bonds and the magenta dash-dot line stands for the Gaussian peak of Si-O bonds. Both Gaussian peaks were separated from the core-level Si 2p spectrum.