Gate Dielectric Effects on Ambipolar Transport in Polymer-Wrapped Single-Walled Carbon Nanotube Network Transistors

This study examines the effects of polymer gate dielectric layers on the charge transport properties of both holes and electrons in solution-processed polymer-wrapped single-walled carbon nanotube (s-SWCNT) network transistors. The dielectric constant plays a crucial role in determining charge transport characteristics, leading to a transition from hole-dominated to electron-dominated ambipolarity as it increases. To elucidate the underlying mechanisms, we analyze the contact resistance (R_c), effective trap state density (N_eff), and mobility in relation to the induced charge density (Q_ind). Our findings indicate that high-k polymer dielectrics exhibit two distinct effects: their randomly aligned dipoles induce energetic disorder at the s-SWCNT network interface, while their high capacitance reduces R_c and N_eff. Hole transport is primarily affected by energetic disorder, whereas electron transport is influenced by reduced R_c and N_eff. This difference arises due to variations in the Schottky–Mott limit between the gold source/drain electrodes and the conduction and valence bands.