Work function of MgO single crystals from ion-induced secondary electron emission coefficient

The work functions Φ_ω of MgO single crystals with its respective orientation (111), (200), and (220) have been investigated from their ion-induced secondary electron emission coefficient γ, respectively, using various ions with different ionization energies in a γ-focused ion beam system. The work function Φ_ω for MgO single crystal with (111) orientation has the lowest value, 4.22 eV, whereas it is 4.94 eV for (200) and the highest value is 5.07 eV for (220). These work functions of MgO single crystals can explain the nonzero values of the ion-induced secondary electron emission coefficient γ for Xe⁺ ions, whose ionization energy is 12.13 eV. © 2003 American Institute of Physics.