Table 1. Values of Thickness (L), Optical Energy Band Gap (E_g), and Energies of Inter-Band Transitions (E₁–E₄) Determined from SE Measurements.

	OK1	OK2	OK3
L [nm]	772 ± 1	132 ± 1	1039 ± 1
Eg [eV]	2.80 ± 0.02	2.73 ± 0.02	2.81 ± 0.02
E1 [eV]	2.46 ± 0.03
E2 [eV]	3.01 ± 0.01	2.98 ± 0.04	3.06 ± 0.01
E3 [eV]	3.40 ± 0.05	3.18 ± 0.07	3.47 ± 0.17
E4 [eV]	4.56 ± 0.07	4.14 ± 0.03	4.26 ± 0.03