Post annealing effect on the electrical properties of top-gate SWNT network transistors

High performance top-gate single walled carbon nanotube network transistors are fabricated with aluminum oxide (Al ₂O ₃) layer as a gate dielectric by atomic layer deposition. It exhibits large on/off ratio (>10 ⁴) due to selective growth of semiconducting tubes by the plasma enhanced chemical vapor deposition. I-V characteristics show p-type or n-type depending on the deposition temperature. We investigate the type dependent characteristics for the carrier polarities with the post annealing effect on the top-gate SWNT network transistors. The dramatic change in the polarity of the top-gate SWNT network transistors, from n-type to p-type due to conversion of I-V characteristics is observed by post-annealing at 350 .5 C for 30 minutes under vacuum. Our observation suggests that competition between electron transfer from the Al ₂O ₃ layers to the SWNT surface and electron capture by oxygen molecules adsorbed on the tube walls seems to be the key point for the V _th change as a function of Al ₂O ₃ deposition temperature.