Silicon nanowire structures for neuronal cell interfacing

During last decade silicon nanowire (NW) field effect transistors (FETs) attracted considerable attention of researchers as perfect candidates for development of highly sensitive and reliable biosensors, which are compatible with cost-efficient CMOS technology. Recently the liquid-gated FETs were used to demonstrate proof of principle extracellular measurements of neuronal cells action potential, which is of great interest regarding the large variety of applications like monitoring of electrical communication within neuronal networks, transmission paths of ionic channels etc. The NWs are expected to provide an improved contact between neuronal cells and NW surface, which is of crucial importance for signal transduction from the cell to the channel of the NW. However, it is still challenging to establish robust tool for the extracellular monitoring of electrogenic cell activity. One of the important milestones of the research in this area is the signalto- noise ratio (SNR), which determines the detection limit of such type of sensors. Therefore, current work is devoted to design, technology development and fabrication of Si NW FET structures for neuronal cell interfacing and characterizing of their transport properties and reliability utilizing technique of noise spectroscopy. During the work we study the transport properties of single Si NW FET transistors, in order to improve understanding of the factors influencing SNR of the NW biosensors. The results demonstrate modulation effect of the channel current by single trap located in the gate dielectric, which reflects extreme charge sensitivity of the NW FET devices. Arising from these investigations we developed and fabricated the Si NW FET structures based on arrays of 50 NWs connected in parallel. Fabricated liquid-gated NW FET structures are characterized in order to find optimal regimes of operation. The revealed front-back gate coupling effect was used to improve the SNR of the fabricated devices by 50%. According to our measurements, the developed Si NW FET structures meet the requirements needed for extracellular detection of the neuronal cell activity. The interface between neuronal cells and fabricated structures was studied using FIB technique. The results demonstrate that the cells contact NWs without a cleft