Resonance enhancement of x rays in layered materials: Application to surface enrichment in polymer blends

Resonance enhancement of x rays of both add and er en orders has been obser ved in a thin polymer blend him of polystyrene (PS) and polybromostyrene (P BrxS) spin cast on a smooth Au layer on a silicon substrate. The x-ray inte nsity enhancement has been measured by detecting fluorescence from the Br a toms in the PBrxS component of the compatible polymer blend. Analysis of th e Br K alpha fluorsscence has yielded the PBrxS distribution in the polymer blend layer in agreement with a PS surface enrichment model. PS is largely enriched at the free surface of the polymer layer and partially enriched a t the underlying interface.