Simultaneous Surface and Bulk Imaging of Polymer Blends with X-ray Spectromicroscopy

We demonstrate the utility of soft X-ray spectromicroscopy to simultaneously image the surface and bulk composition of polymer blend thin films. In addition to conventional scanning transmission X-ray microscopy that employs a scintillator and photomultiplier tube to measure the transmitted X-ray flux, channeltron detection of near-surface photoelectrons is employed to provide information of the composition of the first few nanometers of the film. Laterally phase-separated blends of two polyfluorene co-polymers are studied, with the structure of both wetting and capping layers clearly imaged. This new information provides insight into the connectivity of bulk and surface structures that is of particular relevance to the operation of such blends in optoelectronic devices.