TiN Nanogap Electrodes for DNA Nanoelectronics and Computing: Fabrication and Characterization

Abstract:
Deoxyribonucleic acid (DNA) has emerged as a promising scaffold for next-generation nanoelectronics, driven by the growing focus on evolving green electronics and the expanding role of biomaterials in devices. As the field of green electronics advances, DNA's environmental compatibility, abundance, and scalability underscore its versatility, positioning it as a crucial component for enabling eco-friendly, cost-effective biosensors and memory devices. To explore the intrinsic functionalities of DNA for potential device integration, including its tunable electronic, electrochemical, and charge transport dynamics, DNA molecules are functionalized within the surfaces of metal nanogap electrodes (NGEs). NGEs transduce DNA's specific biomolecular interactions into digital signals, facilitating direct electrical detection and analysis of DNA characteristics across diverse environmental conditions. Given the rising demand for DNA-based devices in bioelectronics and biosensing applications, a strong emphasis is being placed on developing efficient NGE fabrication methods that strike a balance between production affordability, scalability, and precision. This study focuses on fabricating planar NGEs with sub-50 nm nanogap widths employing standard photolithography, electron beam lithography (EBL), and reactive ion etching (RIE) techniques to ensure compatibility with large-scale production. Sputter-deposited titanium nitride (TiN), a biocompatible, CMOS-compliant, and cost-effective material, was used to fabricate NGEs on the SiO2/Si substrates. Electrical characterization of the NGEs was conducted through current-voltage (I–V) measurements under ambient conditions both before and after nanogap formation. Pre-etching I–V characterization showed current densities of ~3 mA/µm, corresponding to a specific resistance of ~0.1 mOmega·cm. Following nanogap formation, current density dropped to ~25 pA/µm—an over 9-order magnitude decrease—indicating effective disruption of electrical continuity. This translates to a post-etch specific resistance of ~1 GOmega·cm, confirming complete electrical isolation between TiN electrodes separated by ~30 nm nanogaps. The sharp transition in I–V characteristics before and after etching demonstrates the precision of the nanogap fabrication process and its suitability for integration into high-impedance nanoscale DNA-functionalized electronic devices for emerging biosensing and computing technologies.