Proton Damage Effects on Carbon Nanotube Field-Effect Transistors

Abstract : This research investigated the effects of proton damage on single-walled carbon nanotube (SWCNT) transistors. The transistors were irradiated by 1.8 MeV protons to determine the damage induced in the SWCNTs and the device substrate using Raman spectroscopy, and to observe the effect on transistor functionality by measuring current-voltage characteristics. Irradiation of the SWCNT transistors to a fluence of 1x10 to the 13th power protons/cm2 resulted in 67% increase in the Raman D/G peak intensity ratio, while at a fluence of 2x10 to the 13th power protons/cm2 the increase in the D/G ratio was only 18%, likely due to radiation annealing. Current-voltage measurements indicated an increasingly negative threshold voltage shift in SWCNT transistors as a function of proton fluence: -1.3 V after a fluence of 1x10 to the 12th power protons/cm2and -1.9 V after a fluence of 2x10 to the 13th power protons/cm2. The drain current decreased 33% after a fluence of 1x10 to the 12th power protons/cm2 and 58% after a fluence of 2x10 to the 13th power protons/cm2. Charge pumping of the SWCNT transistors revealed a significant error attributed to the combination of the non-uniform distribution of SWCNTs across the gate region, adsorbates on the exposed SWCNT and gate oxide surfaces, and inconsistency in transistor performance. The transistor hysteresis also increased as a function of the proton fluence due to interface and bulk charge trapping. This research provided insight into the effect on SWCNT transistors due to proton irradiations up to a fluence of 2x10 to the 13th power protons/cm2 demonstrating both interface and bulk damage effects.