Effect of the Strength of Carbon Nanotube Network on the Efficiency of CNFET Based on Self-Assembled Molecular Monolayer Gate Dielectric

The current demand calls for the development of electronic devices that are efficient, compact, lightweight, and cost-effective. Researchers are striving to enhance the performance of field-effect transistors (FETs), the fundamental components of microelectronics. However, a persistent challenge in present FETs is the trade-off between mobility and the I-ON/I-OFF current ratio, which hampers their overall performance. To address this issue, our work introduces an innovative approach to creating field-effect transistors based on single-walled carbon nanotubes (SWCNTs) combined with self-assembled monolayers (SAMs) as the gate dielectric. Three distinct SAMs, octanethiol, dodecanethiol (DDT), and benzyl mercaptoan (BMT), each with differing dielectric constants, serve as gate dielectrics in SWCNT-FETs. Our research involves a comparative analysis of the three fabricated FETs. This study explores the influence of different SAMs and carbon nanotube (CNT) surface coverage on the performance of carbon nanotube field-effect transistors (CNTFETs) based on random networks. Parameters evaluated include the on/off ratio, field-effect mobility, and subthreshold swing. Intriguingly, the research reveals that CNTFETs with lower surface coverage exhibit significantly improved characteristics compared to those of high surface coverage devices. Among the manufactured CNTFETs, the DDT sample with low surface coverage demonstrates an optimal balance between the I-ON/I-OFF current ratio and mobility. Furthermore, our findings are supported by density functional theory results, indicating that SAMs with longer chain lengths, such as DDT, and aromatic molecules, such as BMT, possess higher dielectric constants, rendering them more favorable for transistor applications.