Contact Engineering in Single-Walled Carbon Nanotube Thin-Film Transistors: Implications for Silane-Treated SiO2 Substrates

Semiconducting single-walled carbon nanotubes (sc-SWCNTs) are promising candidates for thin-film transistors (TFTs). The interface between this semiconducting material and the metal electrodes is critical for both device performance and mechanical robustness, such as adhesion. Sc-SWCNTs were incorporated into top-contact TFTs with different source-drain contact interlayers as a means of improving gold adhesion to silane-treated SiO2 substrates and to study the effect of the contact interlayers on TFT performance. Molybdenum trioxide (MoO3), manganese (Mn), chromium (Cr), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) were all investigated as potential contact interlayers. The incorporation of contact interlayers significantly improved TFT device yield; additionally, the presence of a MoO3 or Mn interlayer resulted in a much higher yield of working TFTs compared to devices made using bare Au. Sc-SWCNT TFTs characterized in air showed a smaller dependence on the contact interlayer compared to TFTs characterized in nitrogen, despite differences in the work function of the contact electrodes. In air, there was little to no difference in contact resistance and other metrics when comparing MoO3–Au and Au contacts, while a drop in performance was observed for Mn–Au-, Cr–Au-, and BCP–Au-based devices. When testing in nitrogen, Mn–Au was comparable to Au and MoO3–Au contacts. These differences suggest oxygen adsorption at the contact surface and that the contact interface is contributing to changes in electrical performance depending on the choice of contact material.