X-ray nanoscopy study on metal nano-structure formation at a metal-organic interface

Abstract

Scanning transmission X-ray microscopy (STXM) with ~30-nm spatial resolution revealed at annealing effect on the metal-organic interface of an Al layer with a poly (3-hexylthiophene) (P3HT) organic semiconducting layer with and without phenyl-C61-butyric acid methyl ester (PCBM). In the case of a P3HT/Al layer with a high-tensile-strain organic over-layer, the overall interface changed to a zagged morphology with Al nano pillars after thermal annealing. On the contrary, a P3HT:PCBM/Al layer with a less-tensile-strain organic over-layer showed a smooth interface except for a few nano pillars. These interfacial morphology changes were related to the initial strain status and to the relaxation process and the phase separation of P3HT crystals relating to the PCBM. Grazing-incident wide-angle X-ray scattering (GI-WAXS) measurements were also conducted to examine the residual strain and the crystalline properties of P3HT in the presence of PCBM.