Enhanced Secondary Electron Emission of ZnO-Doped MgO Coatings: An Experimental and Theoretical Study

The microstructures,electronic structures,and secondary electron emission properties of vacuum evaporated MgO and MgO-ZnO films were characterized with conventional surface probes.The influence of the primary electron energy(E_P) and e-beam bombardment time on the maximum secondary electron yield(δ_m) and its stability was evaluated; and the band-gaps and densities of states were calculated in first-principles density functional theory(DFT).The results show that the MgO-ZnO film outperforms MgO film.To be specific,MgO-ZnO film has higher δ and better stability under long-time heavy e-beam bombardment than MgO film.For example,bombarded at E_p of 800 eV,the MgO-ZnO film,activated at 5 Pa of O₂ and 500℃,had a δ_m of 12.1,and the bombardment by 20 μA e-beam for 120 h merely decreased δ_m to~11.The fact that the ZnO-doping reduces the band-gap and Zn-atoms prevent surface charge accumulation may explain the higher and more stable δ_m.