Threshold Voltage and On–Off Ratio Tuning for Multiple-Tube Carbon Nanotube FETs

In this paper, we demonstrate postprocessing techniques to adjust the threshold voltage ( $V_{t}$) and on–off ratio ( $I_{{ON}}/I_{{OFF}}$) of multiple-tube carbon nanotube field effect transistors (CNFETs). These postprocessing techniques open up an additional degree of freedom to further tune individual CNFETs in addition to various device synthesis and processing techniques. We demonstrate proof-of-concept experiments and fully characterize their design spaces and tradeoffs. The techniques, Threshold Voltage Setting and On–Off Ratio Tuning, were able to adjust the threshold by as much as 2 V and tune the on–off ratio across $\hbox{5} \times \hbox{10}^3$ to $\hbox{5} \times \hbox{10}^5$. In addition, $V_{t}$ Setting could be used as an analysis tool to infer the $V_{t}$ distribution of grown carbon nanotubes (CNTs). These tuning techniques, combined with processes such as doping, will enable high-performance multiple-nanotube devices.