Quantitative studies of long-term stable, top-down fabricated silicon nanowire pH sensors

Abstract

We report a simple and effective method to develop long-term stable, top-down fabricated silicon nanowire (SiNW) pH sensors along with systematic studies on the performance of the sensors. In this work, we fabricated the SiNW pH sensors based on top-down fabrication processes. In order to improve the stability of the sensor performance, the sensors were coated with a passivation layer (PECVD-based silicon nitride) for effective electrical insulation and ion-blocking. The stability, pH sensitivity, and repeatability of the sensor response are critically analyzed with regard to the physics of sensing interface between sample liquid and the sensor surface. Also, trade-off between the stability and pH sensitivity of the sensor response is discussed.

CMOS-Compatible Silicon Nanowire Field-Effect Transistor Biosensor: Technology Development toward Commercialization

“…For instance, ultra-thin SiO 2 layers can be slowly dissolved in aqueous solution by hydrolysis, particularly in high ionic strength solution [ 79 , 80 , 81 ]. SiO 2 gate dielectric is also being limited by a drifting effect of the device’s output current, as well as by gradual incorporation of charged ions from the electrolyte [ 82 , 83 , 84 ]. These issues can be overcome by using other materials with high dielectric constants such as Si 3 N 4 ( k = 7.5), Al 2 O 3 ( k = 9), SnO 2 ( k = 9.86), HfO 2 ( k = 25), and T 2 O 5 ( k = 26).…”

AC and Phase Sensing of Nanowires for Biosensing

“…Typical nanowire resistance is in the range of 100 kΩ to 100 MΩ [ 5 , 6 , 8 , 19 , 38 , 39 , 40 ] so that the currents are of the order of tens to hundreds of nA. Our measurement system is a portable test board that implements a two electrode potentiostat with a lock-in measurement technique for complex impedance detection as described in previous section [ 41 ].…”

A pH sensor with a double-gate silicon nanowire field-effect transistor

“…16 The measured value of the drift in the proposed sensor is 27 mV/h, which is comparable to that of other nanowirebased pH sensors. 17 The long-term stability can be improved with optimization of the sensing oxide material. The SiO 2 used in this work is not the best material for the long-term stability due to high diffusivity of ions and easy hydration of the surface.…”