Pushing the Limits of Biosensing: Selective Calcium Ion Detection with High Sensitivity via High- k Gate Dielectric Engineered Si Nanowire Random Network Channel Dual-Gate Field-Effect Transistors.

Calcium ions (Ca) are abundantly present in the human body; they perform essential roles in various biological functions. In this study, we propose a highly sensitive and selective biosensor platform for Ca detection, which comprises a dual-gate (DG) field-effect transistor (FET) with a high- engineered gate dielectric, silicon nanowire (SiNW) random network channel, and Ca-selective extended gate. The SiNW channel device, which was fabricated via the template transfer method, exhibits superior Ca sensing characteristics compared to conventional film channel devices. An exceptionally high Ca sensitivity of 208.25 mV/dec was achieved through the self-amplification of capacitively coupled DG operation and an enhanced amplification ratio resulting from the high surface-to-volume ratio of the SiNW channel. The SiNW channel device demonstrated stable and reliable sensing characteristics, as evidenced by minimal hysteresis and drift effects, with the hysteresis voltage and drift rate measuring less than 6.53% of the Ca sensitivity. Furthermore, the Ca-selective characteristics of the biosensor platform were elucidated through experiments with pH buffer, NaCl, and KCl solutions, wherein the sensitivities of the interfering ions were below 7.82% compared to the Ca sensitivity. The proposed Ca-selective biosensor platform exhibits exceptional performance and holds great potential in various biosensing fields.