Application of the 15N nuclear reaction technique for hydrogen analysis in polymer thin films

The 15N nuclear reaction technique for hydrogen analysis is applied for the first time to study hydrogen depth profiles in polymer thin films. Relevant details of this technique are given and in particular the important question of depth resolution is discussed. By using an optimized geometry a depth resolution of the order of 10 nm is achieved. Energy straggling data for 15N ions in polystyrene have been deduced from measured H-profiles. The ion dose necessary for the analysis is found to be low enough that radiation damage in the sample is of minor influence. Since the 15N technique discriminates between the isotopes H and D a suitable contrast between different components of a film system is obtained by deuterating one of them. This is illustrated by several examples, including interdiffusion of polystyrene layer systems and surface enrichment of one component of a diblock copolymer. (orig.)