Highly selective GaN-nanowire/TiO2-nanocluster hybrid sensors for detection of benzene and related environmentpollutants

Abstract

Nanowire–nanocluster hybrid chemical sensors were realized by functionalizinggallium nitride (GaN) nanowires (NWs) with titanium dioxide (TiO2) nanoclusters for selectively sensing benzene and other related aromaticcompounds. Hybrid sensor devices were developed by fabricating two-terminaldevices using individual GaN NWs followed by the deposition ofTiO2 nanoclusters using RF magnetron sputtering. The sensor fabrication process employedstandard microfabrication techniques. X-ray diffraction and high-resolutionanalytical transmission electron microscopy using energy-dispersive x-ray andelectron energy-loss spectroscopies confirmed the presence of the anatase phase inTiO2 clusters afterpost-deposition anneal at 700 °C. A change of current was observed for these hybrid sensors when exposed tothe vapors of aromatic compounds (benzene, toluene, ethylbenzene, xylene andchlorobenzene mixed with air) under UV excitation, while they had no response tonon-aromatic organic compounds such as methanol, ethanol, isopropanol,chloroform, acetone and 1,3-hexadiene. The sensitivity range for the noted aromaticcompounds except chlorobenzene were from 1% down to 50 parts per billion (ppb)at room temperature. By combining the enhanced catalytic properties of theTiO2 nanoclusters with the sensitive transduction capability of the nanowires, an ultra-sensitiveand selective chemical sensing architecture is demonstrated. We have proposed amechanism that could qualitatively explain the observed sensing behavior.