CL properties showing the emissions of Tb(OH)
PCs under different excitation currents. (a) Stimulated CL emission spectra of Tb(OH)3/SiO2 PCs with a diameter of 250 nm taken at an electron acceleration voltage of 15 kV. (b) Emission intensity at 543 and 551 nm vs the excitation current. The inset is the CL image taken at full wavelength with an acceleration voltage of 5 kV.