Tuning the Conductivity and Electron Work Function of a Spin-Coated PEDOT:PSS/PEO Nanofilm for Enhanced Interfacial...

We report a novel phenomenon of increasing the adherence of a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS/PEO) nanofilm for Si₃N₄ through cosolvent treatment by DMSO. By varying the w/w% ratio of DMSO, nanofilms with different conductivities were produced. Atomic force microscopy (AFM) analysis showed that the adhesive force between the AFM's Si₃N₄ probe and the nanofilm increased by 35.8% as the conductivity of the nanofilm increased. The conductivity became saturated after the PEDOT:PSS-to-DMSO ratio reached a certain level. This study demonstrates that the variations in the adhesive force are determined by two factors: (1) the difference in EWF between the nanofilm and the counter-body Si₃N₄ and (2) the electrical conductivity of the materials involved. The former is used for establishing a dipole layer at the interface, while the latter determines the degree of ease to achieve the dipole layer. This study demonstrates an approach to tailor interfacial bonding for different types of materials without atomic diffusion, which is promising for applications in various fields such as control of biomedical films on implants and functional films for electronic devices.