Drift-Free pH Detection With Silicon Nanowire Field-Effect Transistors

The drift of drain current (
$I_{D})$
in silicon nanowire field-effect transistor sensors is analyzed under various conditions of pHs and liquid gate voltages (
$V_{LG})$
. It is found that H
⁺
penetration into Helmholtz layer or sensing insulator is the cause of the current drift. To suppress the drift, a novel and fast measurement method with a two-step
$V_{LG}$
is proposed and demonstrated. The drift could be completely suppressed by controlling the duration of the first step pulse. The time required to remove the
$I_{D}$
drift is significantly reduced by the proposed method, from
$\sim 1200$
s to below 100 s on average.