ENERGY DISTRIBUTION OF ION BEAM FROM VARIOUS LIQUID METAL ION SOURCES

We have precisely measured energy distributions of mass separated Si, Be, and B ion beams from various liquid metal (LM) alloy ion sources using Au-Si-Be, Pd-Ni-Si- Be-B, Al-Si, and Pt-Si alloys. It was found that singly charged ion species have long tails in both the higher and lower energy regions of the energy distribution at two orders of magnitude below the peak ion current intensity. The higher energy ion tail can be explained by charge transfer collision between doubly charged ions and neutral atoms. The lower energy ion tail is caused by charge transfer collision and free space field ionisation of neutral atoms. It was found that the energy distribution of singly charged Si+ depends strongly on alloy systems. Si+ from the Pt-Si ion source exhibited no tails in the energy spectrum. We also discussed this phenomenon with the field dissociation model of Si cluster ions