Silicon-Based Ion-Sensitive Field-Effect Transistor Shows Negligible Dependence on Salt Concentration at Constant pH

I(o)n‐sensitive transistors: The response of (miniaturized) ion‐sensitive field‐effect transistors (ISFETs) with oxide interfaces to changes in the electrolyte concentration is discussed. It is shown that FETs covered with a thin alumina layer are almost insensitive to changes in the ionic strength of the electrolyte, while being extremely pH‐sensitive.