2. ALTERNATIVELY DRIVEN DUAL NANOWIRE ARRAYS BY ZnO AND CuO FOR
3.3. CONCLUSIONS
In conclusion, we describe a strategy for creating an air-bridge-structured percolating nanowire array platform that capable of promptly detecting and reliably discriminating between three gases (H2, CO, and NO2). Air-bridge-structured, which has the contact point between nanowire, alternatively driven multiple nanowires, which were made by metal deposition (by e-beam evaporator) and post annealing process in nanoscale on single substrate, was used to form two-dimensional microarray. The current transport characteristics are determined by the conduction paths through the overlapping nanowires.
In n-n junction, the current, known as the thermionic emission current, has to pass the overlapping nanowires over the barrier height due to the depletion zone, while in p-p junction, the hole will pass through the hole accumulation layer in air. In p-n junction, the electrons also flow over the barrier height, however, the resistance of the sensor also depends on the chemical reaction of the analytes on the surface of CuO, which decrease the sensitivities of the gases. These provide the ability of a given sensor array to differentiate among the junctions. The sensors were tested for their ability to distinguish three gases (H2, CO, and NO2), which they were able to do unequivocally when the data was classified using LDA.
Although several strategies for creating an e-nose have been suggested earlier, such as gradients in temperature, nanowire thickness and density, and variation of materials, forming the nanowire junctions array can be used to differentiate the sensor properties of the nanowire-based arrays. Other than the synthesis of the nanowires, all other steps in the fabrication of the e-nose were carried out using top-down microfabrication process, useful for making low cost, nanowire-based e-nose chips, useful for the for a variety of commercial industries, including the food, environmental, bio-medical, and various scientific research fields. As future work, since the e-nose here was carried out by means of artificial gases, a robust sensing study will be carried out with real gas samples for real-world gas comparison test74.
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