Effect of the Ba$^+$ ion implantation on the composition and electronic properties of MoO$_{3}$/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 MoO$_{3}$ 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 $e\varphi$ 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 $\sigma_ m$ 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 $\sigma_ m$ after the ion implantation is predominantly due to a decrease in surface work function $e\varphi$. Heating of the ion-implanted MoO$_{3}$ to 900 K leads to a decrease in work function $e\varphi$ to 2 eV, and coefficient $\sigma_ m$ increases when temperature increases to 1000 K.