Contact Engineering and Reliability of Atomically Precise Graphene Nanoribbon Transistors

Abstract

Atomically precise graphene nanoribbons (GNRs), synthesized from the bottom-up, exhibitpromising electronic properties for high-performance field-effect transistors (FETs) in post-silicon logic computing. However, realizing their immense potential requires overcoming several challenges. In our research, we focused on two critical aspects: contact engineering for GNRs and their long-term reliability and stability. In both studies, we used nine-atom-wide armchair GNRs (9-AGNRs) grown from bottom-up synthesis as transistor channel. In the first study, we investigated strategies to reduce contact resistance at the GNR-metal interface, aiming to improve charge transport. Our findings revealed that indium (In) contacts, compared to palladium (Pd) contacts, exhibit favorable Ohmic-like transport due to reduced interface defects. Additionally, the quality of the GNR channel’s edge structure plays a crucial role in determining overall device performance. In the second study, for the first time, we observed significant performance degradation in 9-AGNR field-effect transistors (9-AGNRFETs) over consecutive full transistor logic cycles. Drawing inspiration from work with other low-dimensional materials (such as molybdenum disulfide (MoS2) and carbon nanotubes (CNTs)), we addressed this issue. By depositing a thin (∼10 nm) layer of aluminum oxide (Al2O3) directly onto these devices using atomic layer deposition (ALD), we demonstrated that the devices operated well for several thousand continuous full cycles without degradation. We strongly believe that our studies enhance our understanding of the factors influencing device performance and provide invaluable insights for guiding future research in GNR-based electronics.