Atom Probe Tomography of Organic Molecular Materials: Sub-Dalton Nanometer-Scale Quantification
In this paper, we demonstrate that atom probe tomography (APT) can be applied to small-molecule organic materials. We show that APT can provide an unprecedented combination of mass resolution of $\lt 1~\mathrm{Da}$, spatial resolution of $\sim 0.3~\mathrm{nm}$ in z and $\sim 1~\mathrm{nm}$ in x-y, and analytic sensitivity of $\sim 50~\mathrm{ppm}$ with no evidence of molecular fragmentation. We discuss two systems that demonstrate the power of APT to uncover structure-property relationships in organic systems that have proven extremely difficult to probe using existing techniques: (1) a previously published model organic photovoltaic system in which we show a chemical reaction occurs at the heterointerface; and (2) a model organic light-emitting diode system in which we show molecular segregation occurs in the emissive layer bulk. These examples illustrate the power of APT to enable new insights into organic molecular materials.