Fig. 6

Plot of (αhν)^1/γ as a function of photon energy (hν) is presented for all samples. (a) (αhν)² vs. (hν) direct Allowed (b) (αhν)^2/3 vs. (hν) direct Forbidden (c) (αhν)^2/3 vs. (hν) direct Allowed (d) (αhν)^1/2 vs. (hν) indirect forbidden.