Ångström-resolved Interfacial Structure in Organic-Inorganic Junctions

Author(s): Schwartz, Craig P; Raj, Sumana L; Jamnuch, Sasawat; Hull, Chris J; Miotti, Paolo; Lam, Royce K; Nordlund, Dennis; Uzundal, Can B; Pemmaraju, Chaitanya Das; Mincigrucci, Riccardo; Foglia, Laura; Simoncig, Alberto; Coreno, Marcello; Masciovecchio, Claudio; Giannessi, Luca; Poletto, Luca; Principi, Emiliano; Zuerch, Michael; Pascal, Tod A; Drisdell, Walter S; Saykally, Richard J | Abstract: Charge transport processes at interfaces which are governed by complex interfacial electronic structure play a crucial role in catalytic reactions, energy storage, photovoltaics, and many biological processes. Here, the first soft X-ray second harmonic generation (SXR-SHG) interfacial spectrum of a buried interface (boron/Parylene-N) is reported. SXR-SHG shows distinct spectral features that are not observed in X-ray absorption spectra, demonstrating its extraordinary interfacial sensitivity. Comparison to electronic structure calculations indicates a boron-organic separation distance of 1.9 {\AA}, wherein changes as small as 0.1 {\AA} result in easily detectable SXR-SHG spectral shifts (ca. 100s of meV). As SXR-SHG is inherently ultrafast and sensitive to individual atomic layers, it creates the possibility to study a variety of interfacial processes, e.g. catalysis, with ultrafast time resolution and bond specificity.