Abstract
The performance of Cs+, C-60(+) and Ar-n(+) (with n approximate to 1700) sputtering ions have been compared for depth profiling multilayer films made from three evaporated phenylalanine layers sandwiched between four thicker evaporated tyrosine layers. Using Cs+, the ion signals and depth resolution degrade with depth and were significantly affected beyond a 200-nm depth. The depth profiling quality was more successful using C-60(+). However, in this case, the depth resolution and the layer width values still degrade with the sputtered depth and are particularly poor after reaching a depth of about 400 nm. When Ar-1700(+) clusters were used, a depth resolution as low as 6 nm was obtained, and this value never exceeds 9 nm. Moreover, the experimental layer width is found to be of the same order of magnitude as the real value. Copyright (C) 2012 John Wiley & Sons, Ltd.