Evaluation of Field-Effect Mobility and Contact Resistance of Transistors That Use Solution-Processed Single-Walled Carbon Nanotubes

Solution-processed single-walled carbon nanotubes (SWNTs) offer many unique processing advantages over nanotubes grown by the chemical vapor deposition (CVD) method, including capabilities of separating the nanotubes by electronic type and depositing them onto various substrates in the form of ultradensely aligned arrays at low temperature. However, long-channel transistors that use solution-processed SWNTs generally demonstrate inferior device performance, which poses concerns over the feasibility of using these nanotubes in high-performance logic applications. This paper presents the first systematic study of contact resistance, intrinsic field-effect mobility (mu(FE)), and conductivity (sigma(m)) of solution-processed SWNTs based on both the transmission line method and the Y function method. The results indicate that, compared to CVD nanotubes, although solution-processed SWNTs have much lower mu(FE) for semiconducting nanotubes and lower sigma(m) for metallic nanotubes due to the presence of a higher level of structural defects, such defects do not affect the quality of electric contacts between the nanotube and metal source/drain electrodes. Therefore, solution-processed SWNTs are expected to offer performance comparable to that of CVD nanotubes in ultimately scaled field-effect transistors, where contacts will dominate electron transport instead of electron scattering in the channel region. These results show promise for using solution-processed SWNTs for high-performance nanoelectronic devices.