Fig. 7

Plots of (αE)^1/2 vs. E for TiO₂ ultrathin films of a 600 cycles caculated by the F-B dispersion model, b 600 cycles caculated by the point-by-point data inversion method, c 500 cycles caculated by the F-B dispersion model, and d 300 cycles caculated by the F-B dispersion model. The inset of a shows the trend chart of band gap for 600 cycles, and the inset of c shows the trend chart of band gap for 500 cycles