The decay processes of Al-n(+/-) (n = 2-24) and Si-n(+/-) (n = 2-12) clusters sputtered from A, Si targets under Xe+ and Cs+ ion bombardment have been studied. We have determined the most probable fragmentation channels of positively and negatively charged clusters in the acceleration zone of tool in time region of 10(-9) to 10(-7) s from the emission moment and in the field-free zones of the apparatus in the time interval of 5 x 10(-7) to 5 x 10(-5) s. The intensive fragmentation of Al-n and Si-n+ occurs with Al and Si+ formation. It permits to make a conclusion, that one part of Al and Si+ ions on the detector corresponds to "true" secondary ions, while another part is due to cluster decays and corresponds to the fragments. (C) 2002 Elsevier Science B.V. All rights reserved.