Simulated soft X-ray scattering bridges real-space and reciprocal-space characterization of multi-phase organic materials

While resonant soft X-ray scattering is increasingly used to measure compositional fluctuations in multi-phase organic materials, some more recent approaches exploit the X-ray polarization to simultaneously probe orientational ordering in the constituent bonds. However, to simultaneously measure orientational and compositional fluctuations with precision, a complementary real-space characterization method becomes necessary. Here, we show how three real-space imaging techniques – Photo-induced atomic force microscopy (PiFM), conventional AFM, and TEM – can be used as the basis for models from which we can simulate soft X-ray scattering using a "virtual instrument", the NIST RSoXS Simulation Suite (NRSS). We show that this combined experimental and computational analysis method leads to sub-nm sensitivity to molecular orientation gradients at the interfaces between domains in co-vapor deposited films, which cannot be found from the X-ray scattering alone. Conversely, the X-ray scattering reveals a secondary compositional length-scale in the materials that is invisible to the real-space microscopies. The combination of the transmission reciprocal-space technique with the real-space microscopy provides a means to investigate the bulk structure of the film, as opposed to simply the surface layer. This approach fuses real-space and reciprocal-space characterization to enhance the information content of both synergistically – that is, the resulting measurement is greater than the sum of its parts.