Enhanced secondary electron emission properties of Zn doped MgO thin films prepared by aerosol assisted chemical vapor deposition

Abstract

In this study Zn doping was applied to MgO thin films in order to improve the secondary electron emission (SEE) property via relieving the surface charging and modifying the electron structure of MgO. MgO and Mg1-xZnxO thin films (the Zn doping proportion x is within 11 at.%) were prepared on Si substrates by a simple, cost effective aerosol assisted chemical vapor deposition method followed by annealing at elevated temperature. The surface morphology and microstructure of the Mg1-xZnxO films were characterized. Secondary electron yield (δ) as a function of primary electron energy the films was examined. First principles calculation based on the density functional theory was introduced to evaluate the electronic structure and work function of Mg1-xZnxO crystals. SEE testing results revealed that δ of the MgO film is effectively improved by Zn doping of proper concentration. The undoped MgO film with relatively smooth surface exhibits a maximum secondary electron yield (δm) of 5.1 at Ep of 750 eV. The δm of the Mg1-xZnxO film (x = 0.09) is 7.0 at Ep = 1500 eV, which is 34.6% higher than that of the MgO film prepared under identical method. Improvement of δ of the Mg1-xZnxO films with x < 0.1 is probably due to the unique surface morphology with protrusions and sharp edges and the increase of electrical conductivities of the films. Another factor contributing to the δ increase is the decrease of work function due to Zn doping, which is confirmed by first-principles calculation of Mg1-xZnxO crystals.