Effect of mobile ions on ultrathin silicon-on-insulator-based sensors

The presence of mobile $Na+$ and $K+$ ions in biological solutions often lead to instabilities in metal-oxide-semiconductor devices and is therefore an important consideration in developing sensor technologies. Permanent hysteresis is observed on silicon-on-insulator field-effect-transistors based sensors after exposure to $Na+$-based buffer solutions but not after exposure to $K+$-based solutions. This behavior is attributed to the difference in mobilities of the ions in silicon dioxide. Mobile charge measurements confirm that ions can be transferred from the solution into the oxide. Self-assembled monolayers are shown to provide protection against ion diffusion, preventing permanent hysteresis of the sensors after exposure to solutions.