Photoelectron and NEXAFS microscopy of radiation induced changes in cadmium arachidate films

Abstract

The radiation induced changes caused by both low energy Ar+ ion bombardment and high energy H+ ion bombardment on Langmuir-Blodgett (LB) films of cadmium arachidate were investigated using a commercial photoelectron microscope installed at the German synchrotron facility BESSY. For the low energy situation, XPS imaging was performed using damage induced differential charging as the contrast mechanism. The high energy H+ bombardment produced less damage and no resolvable charging shift, so this contrast mechanism cannot be used for imaging. However, chemical shifts in the C NEXAFS (near edge X-ray absorption fine structure), caused by the H+ bombardment, are sufficiently large to use as a contrast mechanism. NEXAFS, of course, requires tunable radiation and hence spectromicroscopy in conjunction with synchrotron radiation offers the possibility for imaging chemical changes in organic films which are not observable using fixed energy laboratory sources. In principle, molecular orientation changes are also imageable, as the relative intensities of different features in a NEXAFS spectrum often vary with orientation. © 1995.