Combinatorial near-edge x-ray absorption fine structure: Simultaneous determination of molecular orientation and bond concentration on chemically heterogeneous surfaces

We show that simultaneous molecular orientation and bond chemistry of planar chemically heterogeneous surfaces can be obtained by combining near-edge x-ray absorption fine structure (NEXAFS) spectroscopy and rastering the incident x-ray beam on the specimen. This rastering produces serially two-dimensional NEXAFS images in space and energy, revealing information about the chemistry (including bond concentration) and orientation of the surface-bound molecules with submillimeter planar spatial resolution and submonolayer molecular sensitivity. We illustrate the power of the combinatorial NEXAFS method by simultaneously probing the concentration and molecular orientation of semifluorinated (SF) molecules in double-SF molecular gradients on flat silica substrates