Depth-profiling molecular composition and orientation in vapor-deposited glasses using polarized resonant soft X-ray reflectivity

Physical vapor deposition (PVD) can produce molecular glasses with a preferred molecular orientation, leading to anisotropic optical and electronic properties. Understanding how these properties emerge is essential for applications in devices such as organic light-emitting diodes (OLEDs), yet experimental characterization remains challenging. We use polarized resonant soft X-ray reflectivity (P-RSOXR) to simultaneously depth-profile chemical composition and molecular orientation in multi-component PVD glass thin films of organic semiconductors. P-RSOXR exploits molecular contrast from near-edge X-ray transition dipoles to probe buried structures, independent of electron density. Polarized X-rays further enable quantification of the ensemble-average out-of-plane molecular orientation throughout the nanostructure. We present nanometer-scale measurements of molecular orientation at buried interfaces and in uniformly mixed blends of multiple components.