Figure 1

Dependence of PL emission on the excitation energy in sample R64. (a) Excitation-energy-dependent emission (EDE) spectra, (b) Normalized curves (by peak intensity) of the data in (a), (c) log10 of the PL peak area plotted as a function of excitation energy. The slope calculated using the natural logarithm of the PL data are also shown, (d) the emission peak of PL spectra plotted as a function of the corresponding excitation energy, demonstrating the excitation-energy-dependent emission (EDE) effect.