Effect of the Ba⁺ Ion Implantation on the Composition and Electronic Properties of MoO₃/Mo(111) Films

It is shown that a film consisting of the Mo–O, Mo–Ba–O, and Ba–O compounds is formed in the ion-implanted layer upon implantation of MoO₃ with the Ba⁺ ions. Such a process leads to a sharp variation in the density of state of valence electrons, a decrease in work function eφ to 2.7 eV, a decrease in band gap E_g by a factor of about 1.5, and an increase in maximum coefficient of the secondary electron emission σ_m by a factor of 1.5. It is shown that the emission efficiency of the secondary electrons of the near-surface layer of pure Mo is significantly higher than the emission efficiency of the ion-implanted Mo layers. Thus, an increase in coefficient σ_m after the ion implantation is predominantly due to a decrease in surface work function eφ. Heating of the ion-implanted MoO₃ to 900 K leads to a decrease in work function eφ to 2 eV, and coefficient σ_m increases when temperature increases to 1000 K.