Influence of iron and nitrogen ion beam exposure on the gas sensing properties of CuO nanowires

A precise surface decoration technique, ion implantation, was examined for tuning the p-type gas sensing properties of CuO nanowires. To understand the effects of ion size, ion beam energy and ion beam fluence, heavy Fe and light N ions were implanted with two different ion beam energies (60, 100 keV) and fluences (1 × 1013, 2.5 × 1016 ions/cm2). The morphological changes after ion bombardments have been tracked by a scanning electron microscope (SEM), revealing massive destruction of the nanowires on Fe ion-implanted samples with high energy and fluence values. Transmission electron microscopy (TEM) provided a closer look on single ion-implanted nanowires, highlighting the different size and mass effects of Fe and N ions. The reduction of CuO peaks intensities registered in GI-XRD profiles and the shifts of Cu 2p peaks in X-ray photoemission spectra (XPS) suggest that the monoclinic crystal structure of the CuO nanowires was transformed to amorphous Cu2O and Cu(OH)2 after ion implantations. All ion-implanted sensors improved their sensing abilities compared to pristine CuO nanowires towards various concentrations of target gases (hydrogen, ethanol, and acetone) at 400 °C in dry air flows. In the presence of humid air, sensors showed different characteristics related to outcomes of surface-ion beam interactions.