Measurement of work function at MgO crystal surface by the γ-focused ion beam system

We have suggested that the work function phi(omega), of various kinds of dielectric material can be experimentally obtained from the direct measurement of ion-induced secondary electron emission coefficient gamma for various kinds of slow ion with different ionization energies. To demonstrate this, the work functions phi(omega) of MgO single crystals have been investigated by the gamma-focused ion beam system. The work functions phi(omega) of MgO single crystals have been measured to be 4.22 eV, 4.94 eV, and 5.07 eV according to their respective orientations of (111), (200), and (220), respectively, based on the Auger neutralization mechanism. These work functions of MgO single crystals well explain the non-zero values of ion-induced secondary electron emission coefficient gamma for Xe+ ions whose ionization energy is 12.13 eV.