Abstract
Wide bandgap semiconductor ZnO, GaN and InN nanowires have displayed the ability to detect many types of gases and biological and chemical species of interest. In this review, we give some recent examples of using these nanowires for applications in pH sensing, glucose detection and hydrogen detection at ppm levels. The wide bandgap materials offer advantages in terms of sensing because of their tolerance to high temperatures, environmental stability and the fact that they are usually piezoelectric. They are also readily integrated with wireless communication circuitry for data transmission.
Highlights
The explosion of interest in nanoscience, coupled with growing demand for reliable, low‐power chemical sensors for a wide variety of industrial applications, has led to a surge in the development of nanostructured materials for gas detection [1,2,3,4,5]
In terms of material selection, wide band‐gap semiconductors are ideal for gas sensing, having numerous advantageous properties, including an ability to operate at high temperatures, radiation and environmental stability, and mechanical robustness
The growth of InN nanostructures by conventional metal organic chemical vapour deposition (MOCVD) has met with difficulty because of the low thermal decomposition temperature of InN (< ~600 oC) under nitrogen at standard pressure, which has led to the formation of indium droplets at the substrate surface
Summary
The explosion of interest in nanoscience, coupled with growing demand for reliable, low‐power chemical sensors for a wide variety of industrial applications, has led to a surge in the development of nanostructured materials for gas detection [1,2,3,4,5]. Several issues must still be addressed, including quantifying sensitivity, improving detection limits at room temperature, establishing the reproducibility and stability of the sensors and reducing power consumption. Materials such as ZnO show sensitivity to environmental exposure, in terms of forming surface conducting layers in the presence of oxygen or water vapour exposure. The use of catalyst metal coatings on GaN, InN and ZnO nanowires has been found to greatly enhance the detection sensitivity for hydrogen. Improvements in growth techniques for InN nanostructures have produced nanobelts and nanorods capable of hydrogen detection down to 20 ppm after catalyst coating. Note that no underlying thin film of GaN was observed for the conditions used to grow the tested nanowires
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