Noise Spectroscopy of Liquid–Solid Interface Processes in Adjusted Physiological Solutions Using GAA Si Nanowire FET Biosensors

Liquid gate‐all‐around (LGAA) field‐effect transistor (FET) biosensors represent advanced material device structures responding electrically to surface potential change and allowing ultra‐high sensitivity to biochemical liquids and human bodily fluids. However, the origin and physical working mechanisms for such a type of signals in different complex biochemical solutions remain still many opened questions. Here, noise spectroscopy and impedance methods are applied to study liquid–solid interface properties in LGAA FETs working in adjusted physiological solutions of different pH values. High‐quality liquid LGAA Si nanowire (NW) FET biosensors demonstrate the high electronic performance of I–V characteristics in good agreement with modeling data. Impedance spectroscopy measurements allow for analyzing the double‐layer capacitances and ion behavior under different pH conditions. Moreover, the noise spectra of the current fluctuations in the biosensors for several solutions are analyzed at different applied liquid‐gate and drain‐source voltages. The results demonstrate accurate detection of the dynamic ion processes on the nanowire surface. Charge inversion effect is revealed in single‐valent ion solutions. Tiny signal characterization results obtained using the LGAA NW FET biosensors provide broader insights into the optimization of sensor parameters for biomedical molecular detection.