Control and Detection of Organosilane Polarization on Nanowire Field-Effect Transistors

Abstract

We demonstrated control and detection of UV-induced 3-aminopropyltriethoxysilane (APTES) polarization using silicon nanowire field-effect transistors made by top-down lithograph technology. The electric dipole moment in APTES films induced by UV-illumination was shown to produce negative effective charges. When individual dipoles were aligned with an externally applied electric field, the collective polarization can prevail over the UV-induced charges in the wires and give rise to an abnormal resistance enhancement in n-type wires. Real-time detection of hybridization of 15-mer poly-T/poly-A DNA molecules was performed, and the amount of hybridization-induced charges in the silicon wire was estimated. Based on these results, detection sensitivity of the wire sensors was discussed.Hetero-interfaces between organic and semiconductor oxides have attracted extensive attentions 1-4 due to the critical role of molecule assembly in the sensing electronics involving hybrid structures. APTES 5 (3-aminopropyltriethoxysilane) and other compounds such as PTS 6 (n-propyltrichlorosilane), OTS 7 (n-octadecyltrichlorosilane), TCTS 8 (n-triacontyltrichlorosilane), OTMS 9 (n-octadecyltrimethoxysilane), and AHT-MS 9 (n-aminoheptadecyltrimethoxysilane) with head-andtail functional groups are widely used interfacing molecules, and assembly of these molecules is essential in surfacemodification technologies. Silanization of oxidized semiconductor surfaces is a commonly employed scheme for functionalization of sensors. The functional groups would then provide binding sites for attachment of probe molecules, such as single-strand DNA (ssDNA), on the semiconductor sensing devices. The nanowire-based sensors have been demonstrated 10-14 as an ultra sensitive detector for probing molecular charges at the wire surface. However, surface modification of the functional groups on the nanowire surface is not a trivial task. Extensive studies in the surfacemodification were reported in the past years, 5-9 but issues concerning monolayer molecule ordering in terms of the electric dipole moment remain unexplored. Taking APTES as an example, in this study, we proposed a simple method to align the molecule dipoles, and the degree of alignment was examined by underneath Si-nanowire (SiNW) field effect transistors. This method provides a sensitive way for structure investigation of few molecules at the nanometer scale, which is otherwise unfeasible by the present-day examination tools. † These authors contributed equally to this work.

Organic Surface Modification of Silicon Nanowire-Based Sensor Devices

“…Alternative approaches have been reported as well, e.g., the use of UV/ozone for the surface activation, followed by the use of neat APTES (Li, 2010). Also toluene (Lobert, 2003) and acetone (Lin, 2007) have been used as a solvent in the silanization step.…”

“…To overcome the problem of the disordered monolayers, Lin et al performed a posttreatment of APTES-functionalized devices (Lin, 2007). After the APTES modification, they aligned the internal dipoles of the APTES molecules using high electric fields, thus decreasing the disorder in the monolayer.…”

“…This linker molecule is used to form an aldehyde-terminated surface, which increases the possibilities for further reactions, including the reaction with amine groups of, e.g., anti-bodies (Kim, 2007), proteins and enzymes (Lee, 2008;Wang, 2008;Zhang, 2010). Also amino-terminated, single-stranded DNA (ss-DNA) has been attached to APTES/GA-modified surfaces to measure hybridization-induced mismatches in 15-mer ss-DNA chains (Lin, 2007). The addition of glutaraldehyde is, like that of APTES, both performed from solution (Bi, 2008b;Zhang, 2010) and from the gas phase (Wang, 2008).…”

Top-down nanofabrication of silicon nanoribbon field effect transistor (Si-NR FET) for carcinoembryonic antigen detection

“…In the top-down approach, the nanostructure is fabricated on a silicon-on-insulator (SOI) wafer 26 and patterned by lithographic processes. The source and drain electrodes are defined by electron-beam etching and doping technique.…”

Direct protein detection with a nano-interdigitated array gate MOSFET

“…Electronic biosensors have strongly benefited from the development and application of nanotechnologies. Among recent proposed devices, nanowire sensors have attracted much attention because the large surface-to-volume ratio of nanowires potentially increases sensor sensitivity to the single-molecule detection level (Cui et al, 2001;Elfström et al, 2007Elfström et al, , 2008Hahm and Lieber, 2004;Li et al, 2004;Lin et al, 2007;Maki et al, 2008;Patolsky et al, 2006;Talin et al, 2006). Two main technologies are used to realize those nanowire sensors: bottom-up and top-down approaches.…”