Enhanced Sensing of Nonpolar Volatile Organic Compounds by Silicon Nanowire Field Effect Transistors

Abstract

Silicon nanowire field effect transistors (Si NW FETs) are emerging as powerful sensors for direct detection of biological and chemical species. However, the low sensitivity of the Si NW FET sensors toward nonpolar volatile organic compounds (VOCs) is problematic for many applications. In this study, we show that modifying Si NW FETs with a silane monolayer having a low fraction of Si-O-Si bonds between the adjacent molecules greatly enhances the sensitivity toward nonpolar VOCs. This can be explained in terms of an indirect sensor-VOC interaction, whereby the nonpolar VOC molecules induce conformational changes in the organic monolayer, affecting (i) the dielectric constant and/or effective dipole moment of the organic monolayer and/or (ii) the density of charged surface states at the SiO(2)/monolayer interface. In contrast, polar VOCs are sensed directly via VOC-induced changes in the Si NW charge carriers, most probably due to electrostatic interaction between the Si NW and polar VOCs. A semiempirical model for the VOC-induced conductivity changes in the Si NW FETs is presented and discussed.

Fluorinated alkyne-derived monolayers on oxide-free silicon nanowires via one-step hydrosilylation

“…[9] One of the approaches is to create an active channel layer by the chemical adsorption of organic molecules via Si-O or Si-C bonds onto the Si surface, which passivates the surface of pure Si. [10][11][12][13] This strategy improves the surface properties of the NWs as well as enhances the electron transport in Si NWs based FETs. [14,15] Since Si surface atoms are easily oxidized, asprepared Si NWs, as well as other Si materials, are always coated with a native oxide layer.…”

Tunable diameter electrostatically formed nanowire for high sensitivity gas sensing

“…In particular, silicon nanowire (SiNW)-based FETs were demonstrated as highly sensitive and selective chemical sensors operating at room temperature (RT) [2][3][4][5]. Single-crystalline SiNWs are fabricated via bottom-up or top-down methods with uniform spatial dimensions and high carrier mobility [6][7][8][9][10][11].…”

“…Single-crystalline SiNWs are fabricated via bottom-up or top-down methods with uniform spatial dimensions and high carrier mobility [6][7][8][9][10][11]. FETs based on arrays of SiNWs, usually modified with molecular groups, have been predominantly reported to be highly sensitive and selective to volatile organic compounds (VOCs) [2,4,[12][13][14][15][16][17][18]. Owing to the high surface-tovolume ratio of SiNWs, surface states have a large impact on the device performance and often require surface passivation.…”

Controlled Synthesis of Horizontal Silicon Nanowires for Biosensor Application

“…[1][2][3] Functionalized with biomaterials, SiNWs connected between electrodes operate well in sensing devices. 4 The top-down method is considered the representative approach for the synthesis of SiNW arrays, and is based on the microelectromechanical systems (MEMS) process, which has been broadly applied with good controllability of diameter and length because of the lithography process.…”