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Indium oxide (In2O3) is a widely used n-type semiconductor for detection of pollutant gases; however, its gas selectivity and sensitivity have been suboptimal in previous studies. In this work, zinc-doped indium oxide nanowires with appropriate morphologies and high crystallinity were synthesized using chemical vapor deposition (CVD). An accurate method for electrical measurement was attained using a single nanowire microdevice, showing that electrical resistivity increased after doping with zinc. This is attributed to the lower valence of the dopant, which acts as an acceptor, leading to the decrease in electrical conductivity. X-ray photoelectron spectroscopy (XPS) analysis confirms the increased oxygen vacancies due to doping a suitable number of atoms, which altered oxygen adsorption on the nanowires and contributed to improved gas sensing performance. The sensing performance was evaluated using reducing gases, including carbon monoxide, acetone, and ethanol. Overall, the response of the doped nanowires was found to be higher than that of undoped nanowires at a low concentration (5 ppm) and low operating temperatures. At 300 °C, the gas sensing response of zinc-doped In2O3 nanowires was 13 times higher than that of undoped In2O3 nanowires. The study concludes that higher zinc doping concentration in In2O3 nanowires improves gas sensing properties by increasing oxygen vacancies after doping and enhancing gas molecule adsorption. With better response to reducing gases, zinc-doped In2O3 nanowires will be applicable in environmental detection and life science. [ABSTRACT FROM AUTHOR]

In this study, indium oxide nanowires of high-density were synthesized by chemical vapor deposition (CVD) through a vapor–liquid–solid (VLS) mechanism without carrier gas. The indium oxide nanowires possess great morphology with an aspect ratio of over 400 and an average diameter of 50 nm; the length of the nanowires could be over 30 μm, confirmed by field-emission scanning electron microscopy (SEM). Characterization was conducted with X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence spectrum (PL). High-resolution TEM studies confirm that the grown nanowires were single crystalline c-In2O3 nanowires of body-centered cubic structures. The room temperature PL spectrum shows a strong peak around 2.22 eV, originating from the defects in the crystal structure. The electrical resistivity of a single indium oxide nanowire was measured to be 1.0 × 10−4 Ω⋅cm, relatively low as compared with previous works, which may result from the abundant oxygen vacancies in the nanowires, acting as unintentional doping. [ABSTRACT FROM AUTHOR]

Heterostructured TiO 2 /In 2 O 3 nanowires have been extensively applied in various photonic devices; their performance is highly related to the microstructures, which has not been, however, clearly understood; thus, it is important to investigate the microstructural evolution of the material during processing. In this work, the crystallinity and microstructure of TiO 2 /In 2 O 3 nanowires were successfully controlled with the variation of annealing temperatures via solid-state reactions. The dynamic phase transformation process was demonstrated by in situ transmission electron microscope (TEM). Moreover, the elemental information at different states was identified by energy dispersive spectroscopy (EDS). It is found that different annealing temperatures would contribute to different solid-state reactions and nanowire heterostructures. Additionally, photoresponse studies show characteristics enhancement for such nanoheterostructures. This study provides the knowledge of the fundamental science in kinetics of heterostructured nanostructures, which benefits the improvement of the performance for future photonic applications. [Display omitted] • The solid-state reaction of In 2 O 3 /TiO 2 heterostructured nanowires was investigated by in situ TEM. • The microstructure and crystallinity of TiO 2 were successfully controlled with varying temperatures. • The nanowire would be broken with the reaction length achieving 4.975 times the radius. • A U-shape phase boundary was formed during the diffusion of Ti, resulting from the different diffusion rates of facets. • This study provides the fundamentals in nano-heterostructures, advancing the performance for future photonic applications. [ABSTRACT FROM AUTHOR]