Enhancement of Cold Electron Emission in Europium Doped Zinc Oxide Rod: An Experimental Verification of Simulative Prediction

The present work describes the enhanced cold emission properties of chemically synthesized zinc oxide (ZnO) rods after doping with europium (Eu). X-ray diffraction confirms the proper phase formation, whereas energy-dispersive X-ray analysis shows the material stoichiometry. The field emission scanning electron micrographs reveal that Eu doping increases the surface roughness of individual ZnO rods. Also, Eu doping notably enhances the water-repellent properties of ZnO with a water contact angle as high as 130 °. Fourier-transformed infrared spectra provide information regarding different vibrational energy levels present, whereas PL spectra show prominent signals at 440, 466, 580, and 615 nm come from both the host and dopant material. ANSYS-Maxwell simulation predicts a significant enhancement of cold emission properties of the doped ZnO. Experimentally, more than a 2.5-time increment is achieved in the enhancement factor for the doped sample. Also, the turn-on field shows a significant reduction from 5.26 to 2.65 V µm^-1. The reasons behind this enhancement are believed to be changes in material roughness, favorable band bending, and the newly evolved energy state. This work thus establishes the potential of Eu-doped ZnO to be simultaneously used as hydrophobic cold emitters as well as suitable components in optoelectronic devices.