Study of secondary ions from a sputter ion source

Secondary sputtered ions, produced from polycrystalline aluminium under 3-8 keV Zn+ ion bombardment have been studied by a quadrupole mass spectrometer. The sputtered ions are usually multiply and singly charged, mono- and polyatomic, positive and negative ions characteristic of the target. Al++, Al2+, Al3+ ions have been detected so far. In the present paper, the study of the intensity of secondary Al+ ions as a function of the bombarding Zn+ ion energy for three different values of target current density is reported. The variation is found to be linear for each value of target current density. The diminishing behaviour of secondary positive ion emission yield with the rise of primary ion current density may be due to the gradual reduction in the degree of oxygen coverage on the sample surface under the present experimental condition. The present studies are important in the operation of ion sources whose various components are frequently subjected to energetic ion bombardment giving rise to ions of the component materials. (auth.)