Fabrication of 2D-Material-Based Ionic Transistors

Student’s Full Name: Siyi (Cathy) Chen Home Institution: University of Illinois at Urbana Champaign NNCI Site: CNF @ Cornell University REU Principal Investigator: Yu Zhong, Materials Science and Engineering, Cornell University REU Mentor: Kaushik Chivukula Abstract: We used CNF's Heidelberg Mask Writer DWL-2000, ABM Contact Aligner, Oxford 81 RIE, AJA Ion Mill, and SC4500 Even-Hour Evaporator to fabricate the 2D-material-based ionic transistors. Traditional electronic field-effect transistors (FETs), which utilize electrons and holes as charge carriers, are indispensable in modern electronic devices such as integrated circuits and microprocessors. They form the backbone of today's digital technology by enabling efficient information processing, storage, and transmission. Despite ongoing challenges in the miniaturization of electronic transistors, ionic FETs offer distinct advantages, particularly biocompatibility and tunable conductance. Our project aims to fabricate ionic transistors using advanced 2D materials and address the limitation of low on-off current ratios in these devices. The human brain, with its highly selective ionic transmission system, processes vast amounts of information and facilitates neural communication daily. To mimic the ultra-functional capabilities of the brain, nano-channeled ionic field-effect transistors that use ions like Na+ and Ca2+ as carriers, similar to those in neural processes, show great potential for future applications. Such transistors are promising for artificial brain systems and memory devices like neuromorphic memristors due to their unique ability to maintain discrete conductivity states, which serve as memory storage units. To replicate the ultra-selectivity of brain ionic channels, we aim to fabricate ionic transistors with nanochannels approaching the Debye length. Conventional microchannels, with their short Debye length and discontinuous electric field effect, result in the undesirable coexistence of both negative and positive ions. In contrast, the nanochannel design enables the electric field to penetrate the entire channel, predominantly permitting the passage of only a single ion type, mirroring brain function. After completing the entire fabrication process—depositing the nanoscale organic cage molecules akin to Cu-TCPP with pyridine treatment, forming a heterostructure with a monolayer of MoS₂, coating SiO₂ as the insulating layer, and setting up the drain, source, and gate electrodes—the transistor is expected to show a current of less than 10-11A when the drain and source are not connected. This would indicate a successful fabrication with no leakage, making it ready for future integrations.