Enhancement of p-type Behavior of Inkjet-Printed Single-Walled Carbon Nanotube
Transistors from Phenylphosphonic acid Coating

Single-walled carbon nanotube (SWCNT) had interest over the past decade as a high potential material due to their thermal stability and high conductivity [1-2]. In particular, SWCNTs had high carrier mobility and advantages of solution processing lead to their development for applications in electronic devices such as transistors and logic circuits [3-4]. However, the doping technology for controlling the charge carrier transport of SWCNT is still immature. The chemical doping method is a process that modulates the Schottky barrier without damaging SWCNT. In this paper, we present p-type behavior enhanced SWCNT transistor by patterning semiconductors and electrodes using inkjet printing technology and doping them with the self-assembled monolayer (SAM) material phenylphosphonic acid (PPA). The benzene rings of PPA coated on the SWCNTs without annealing process fill the voids in the channels by π-stacking interaction. As a result, SWCNTs connected through PPA form additional pathway for charge carrier transport. The p-type current of the SWCNT transistor is enhanced 4.3 times due to the improved hole injection resulting from PPA doping effect. In addition, the 10 PPA-doped SWCNT transistors increased the hole mobility by an average of 8.25 cm² V^-1 s^-1. Finally, the positive-shifted threshold voltage of 0.55 V indicates the potential for application in depletion mode of PPA-doped SWCNT transistor.