Most of the sensors are in the form of chemiresistors, and their conductance is changed by the surface adsorbed molecules and depends highly on the analyte concentrations.The traditional Ohm contacted nanosensor is hard to realize the ultra-sensitive detection in real circumstances where open environment must be considered. However, Schottky contact could largely improve the sensitivity of nanosensors, because Schottky barrier serves as a “gate” controlling the current passing. A small change induced by molecuels adsorption in Schottky barrier height will lead to a huge change in current.
The sensor constructed by Prof. DOU’s group showed high sensitivity towards room temperature saturated vapors of 2,4,6-trinitrotoluene (TNT), dinitrotoluene (DNT), para-nitro toluene (PNT), picric acid (PA), hexogen (RDX) and octagon (HMX). In the design, graphene or reduced graphene oxide (rGO) with high charge carrier mobility, atomically thin nature and abundant adsorption sites, makes the semiconductor/graphene Schottky heterojunction ultra-sensitive for gas sensing. Besides, vertical alligned silicon nanowires offer distinct merits in terms of the capability for surface functionalization and the sufficient gaps for molecules diffusion. SiNWs array-based sensor has also been considered as an ideal platform for gas sensing due to the higher signal-to-noise ratios and faster response.
Researchers found that the insertion of TiO2 could increase the Schottky barrier height and adsorption energy towards nitro-explosives. Superior selectivity was shown even compared with interfering gases of 10 ppm. The reported interface modulation strategy can be adopted to greatly improve the sensing performance of Schottky sensors and provides a new approach for designing ultra-sensitive and selective sensors.
The study has been published online in Advanced Functional Materials.
This work was financially supported by the National Natural Science Foundation of China, and Hundred Talent Program of CAS, Xinjiang International Science & Technology Cooperation Program, etc.
Figure：TiO2 insertion boosted SiNWs array/TiO2/rGO Schottky sensor towards ultra-sensitive and selective nitro-explosives vapors detection(Image by XTIPC)
Prof. DOU Xincun
Xinjiang Technical Institute of Physics & Chemistry, CAS