PRECISE MEASUREMENT OF ENERGY DISTRIBUTION IN Ga LMIS

Abstract
Temperature dependence of energy distribution.for Ga⁺ ion from Ga liquid metal ion source(LMIS) is measured in the range of more than 3 digits in ion current by using a single focusing sector magnet with an energy resolution of less than 2 eV. As increasing the source temperature at a fixed ion current of l µA, the distribution curve changes from a single Gaussian peak to three peaks including 1) the Gaussian, 2) the peak at the energy position about 7 eV lower than it, and 3) the peak at about 32 eV. From the calculation of the energy deficit based on free space field ionizattion of neutrals coming from the outer space, it is shown that the experimental energy deficit agrees with the calculated for the liquid apex radius of 1 nm and the field strength of 16 V/nm. The rate equation representing variation of ion flux is proposed and it is shown that the ratio of the ion fluxes produced by field evaporation, free space field ionization, and charge tranfer collision can be quntitatively explained.