Silicon Nanowires as pH Sensor

Abstract

Silicon nanowires (SiNWs) have been used as the sensing layer in an extended gate field effect transistor (EGFET) for the measurement of pH solutions. The SiNWs were synthesized directly from the silicon substrates via a catalytic reaction under N 2 atmosphere at 955 o C without supplying any gaseous or liquid Si sources. Nickel catalyst was deposited on the silicon substrates by sputtering. The average diameter of the SiNWs was about 30 ~ 50 nm and a length of up to a few tens of micrometers. In this research, the silicon bulk materials and SiNWs were used respectively as the sensing layer in an extended gate field effect transistor to measure the sensitivity of the pH solutions. Experimental results showed that the pH sensitivity of silicon bulk materials is poor. However, a good pH sensing properties of SiNWs, with sensitivities in the range of 58.3mV/pH, was observed. Therefore, it was suggested that the pH sensitivity of silicon bulk materials was greatly improved by downsizing into nanoscale.

Chemical sensors based on nanostructured materials

“…Bashir and co-workers [69] described silicon nanowire oxygen sensor that was realized using top-down microelectronics processing techniques. Unlike the idea of Lieber's group, Hsu et al [70] presented a SiNWbased pH sensor in an extended-gate field-effect transistor. They suggested that SiNWs could support a three-dimensional contact mode, resulting in a larger total surface area, and the SiNWs were cylindrical, which caused the non-bridging Si O bonds of the surface to be of the suspended and standing types.…”

Variable range hopping conduction in N- and P-typein situdoped polycrystalline silicon nanowires

“…Quasi-one dimensional semiconductor nanowires feature a high surface-to-volume ratio and special electronic and optical properties, arising from the size confinement in the nano-sized channel region [1][2][3][4]. These unique aspects, especially in silicon nanowires (SiNWs), stimulate enormous research efforts to design and develop a new generation of high performance FET transistors and sensors by incorporating the SiNWs as the functional channels.…”

Initial nucleation and growth of in-plane solid-liquid-solid silicon nanowires catalyzed by indium

“…1͒ and oxide-assisted growth ͑Ref. 2͒ modes, and serve as the key elements for high performance SiNWsbased transistors, 3,4 biosensors, 5,6 and energy harvesting devices. 7,8 Recently, we reported an in-plane solid-liquidsolid ͑IPSLS͒ growth mode for fabricating lateral SiNWs in a plasma-enhanced chemical-vapor deposition ͑PECVD͒ system during an all-in situ process.…”