Interfacial charge transfer in nanoscale polymer transistors

TL;DR

This study investigates interfacial charge transfer in nanoscale polymer transistors, revealing how contact material influences charge injection and device performance through transport measurements and microscopy.

Contribution

It provides direct experimental evidence of charge transfer effects at metal/polymer interfaces in short-channel transistors, highlighting differences between Pt and Au contacts.

Findings

Short channel conduction is enhanced with Pt contacts due to charge transfer.

ACSTM confirms hole transfer from Pt into P3HT.

Contact resistance varies with channel length and contact material.

Abstract

Interfacial charge transfer plays an essential role in establishing the relative alignment of the metal Fermi level and the energy bands of organic semiconductors. While the details remain elusive in many systems, this charge transfer has been inferred in a number of photoemission experiments. We present electronic transport measurements in very short channel ($L < 100$ nm) transistors made from poly(3-hexylthiophene) (P3HT). As channel length is reduced, the evolution of the contact resistance and the zero-gate-voltage conductance are consistent with such charge transfer. Short channel conduction in devices with Pt contacts is greatly enhanced compared to analogous devices with Au contacts, consistent with charge transfer expectations. Alternating current scanning tunneling microscopy (ACSTM) provides further evidence that holes are transferred from Pt into P3HT, while much less charge transfer takes place at the Au/P3HT interface.