(53o) Ultrasensitive Probing of the Local Electronic Structure of Nitrogen Doped Carbon and Its Applications to 2D Electronics, Catalysis and Bio-Physics. 

Chemical doping of carbon is an effective way to tailor their electronic and chemical properties such as band level alignment, charge carrier mobilities, and catalytic activity. Nitrogen doped carbon-based materials have received a lot of attention due to its premise in 2D electronics (e.g. as contact layer with tunable electronic properties), fuel cell applications (e.g. ORR) or metal-air batteries.

It has been shown that different bond types such as graphitic, pyrrolic, and pyridinic can exist in N-doped carbon, and they play a crucial role in determining the electronic properties both locally and for the whole matrix (doping effect). Core-level X-ray spectroscopy has been proven to be a powerful analytic method for characterizing different bond types in doped carbon. X-ray emission spectroscopy has the ability to map out the local electronic structure around elements in a site- and symmetry-specific way, and direct comparison to DFT based theory is possible. However, XES has been inaccessible in the soft x-ray regime since the current technology lacks the sensitivity to measure the weak signal from low concentration dopants.

Superconducting transition edge sensor (TES) technology presents a unique opportunity to build novel detectors with greatly increased sensitivity in the soft x-ray regime while maintaining excellent energy resolution. We have commissioned a new generation soft x-ray superconducting TES spectrometer with a scientific motivation to probe the local electronic structure of ultra-low concentration sites in biology, chemistry, and materials, currently inaccessible in the soft x-ray regime due to the limited sensitivity of existing technology.

We will show the applicability of TES based spectrometers to provide detailed insight into the local electronic structure of nitrogen in graphene, carbon catalysts, carbon for chemical storage as well as nano-diamond. The applicability of this unprecedented photon in / photon out sensitivity in the soft x-ray regime to future in-operando studies of chemical transformations and the (potential) active role of nitrogen sites will also be discussed.