Abstract:Four kinds of nanostructures, nanoneedles, nanohooks, nanorods, and nanotowers of In2O3, have been grown by the vapor transport process with Au catalysts or without any catalysts. The morphology and structure of the prepared nanostructures are determined on the basis of field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The growth direction of the In2O3 nanoneedles is along the [001], and those of the other three nanostructures are along th… Show more
“…2 have been displayed in our previous work which is about the field emission properties of the In 2 O 3 nanostructures [7]. The highly magnified FESEM image of the synthesized In 2 O 3 nanotowers is shown in Fig.…”
Section: Resultsmentioning
confidence: 99%
“…2e recorded with an electron beam perpendicular to the surface of the In 2 O 3 nanotower demonstrates that the In 2 O 3 nanotower is single crystal and the growth direction is along [200].Fig. 2
a The highly magnified FESEM image and b the XRD pattern of the In 2 O 3 nanotowers [7]. c The bright-field image, d the HRTEM image, and e the SAED pattern of an individual In 2 O 3 nanotower [7]…”
Section: Resultsmentioning
confidence: 99%
“…2
a The highly magnified FESEM image and b the XRD pattern of the In 2 O 3 nanotowers [7]. c The bright-field image, d the HRTEM image, and e the SAED pattern of an individual In 2 O 3 nanotower [7]…”
Section: Resultsmentioning
confidence: 99%
“…c The bright-field image, d the HRTEM image, and e the SAED pattern of an individual In 2 O 3 nanotower [7]…”
Indium oxide (In2O3) tower-shaped nanostructure gas sensors have been fabricated on Cr comb-shaped interdigitating electrodes with relatively narrower interspace of 1.5 μm using thermal evaporation of the mixed powders of In2O3 and active carbon. The Schottky contact between the In2O3 nanotower and the Cr comb-shaped interdigitating electrode forms the Cr/In2O3 nanotower Schottky diode, and the corresponding temperature-dependent I-V characteristics have been measured. The diode exhibits a low Schottky barrier height of 0.45 eV and ideality factor of 2.93 at room temperature. The In2O3 nanotower gas sensors have excellent gas-sensing characteristics to hydrogen concentration ranging from 2 to 1000 ppm at operating temperature of 120–275 °C, such as high response (83 % at 240 °C to 1000 ppm H2), good selectivity (response to H2, CH4, C2H2, and C3H8), and small deviation from the ideal value of power exponent β (0.48578 at 240 °C). The sensors show fine long-term stability during exposure to 1000 ppm H2 under operating temperature of 240 °C in 30 days. Lots of oxygen vacancies and chemisorbed oxygen ions existing in the In2O3 nanotowers according to the x-ray photoelectron spectroscopy (XPS) results, the change of Schottky barrier height in the Cr/In2O3 Schottky junction, and the thermoelectronic emission due to the contact between two In2O3 nanotowers mainly contribute for the H2 sensing mechanism. The growth mechanism of the In2O3 nanotowers can be described to be the Vapor-Solid (VS) process.
“…2 have been displayed in our previous work which is about the field emission properties of the In 2 O 3 nanostructures [7]. The highly magnified FESEM image of the synthesized In 2 O 3 nanotowers is shown in Fig.…”
Section: Resultsmentioning
confidence: 99%
“…2e recorded with an electron beam perpendicular to the surface of the In 2 O 3 nanotower demonstrates that the In 2 O 3 nanotower is single crystal and the growth direction is along [200].Fig. 2
a The highly magnified FESEM image and b the XRD pattern of the In 2 O 3 nanotowers [7]. c The bright-field image, d the HRTEM image, and e the SAED pattern of an individual In 2 O 3 nanotower [7]…”
Section: Resultsmentioning
confidence: 99%
“…2
a The highly magnified FESEM image and b the XRD pattern of the In 2 O 3 nanotowers [7]. c The bright-field image, d the HRTEM image, and e the SAED pattern of an individual In 2 O 3 nanotower [7]…”
Section: Resultsmentioning
confidence: 99%
“…c The bright-field image, d the HRTEM image, and e the SAED pattern of an individual In 2 O 3 nanotower [7]…”
Indium oxide (In2O3) tower-shaped nanostructure gas sensors have been fabricated on Cr comb-shaped interdigitating electrodes with relatively narrower interspace of 1.5 μm using thermal evaporation of the mixed powders of In2O3 and active carbon. The Schottky contact between the In2O3 nanotower and the Cr comb-shaped interdigitating electrode forms the Cr/In2O3 nanotower Schottky diode, and the corresponding temperature-dependent I-V characteristics have been measured. The diode exhibits a low Schottky barrier height of 0.45 eV and ideality factor of 2.93 at room temperature. The In2O3 nanotower gas sensors have excellent gas-sensing characteristics to hydrogen concentration ranging from 2 to 1000 ppm at operating temperature of 120–275 °C, such as high response (83 % at 240 °C to 1000 ppm H2), good selectivity (response to H2, CH4, C2H2, and C3H8), and small deviation from the ideal value of power exponent β (0.48578 at 240 °C). The sensors show fine long-term stability during exposure to 1000 ppm H2 under operating temperature of 240 °C in 30 days. Lots of oxygen vacancies and chemisorbed oxygen ions existing in the In2O3 nanotowers according to the x-ray photoelectron spectroscopy (XPS) results, the change of Schottky barrier height in the Cr/In2O3 Schottky junction, and the thermoelectronic emission due to the contact between two In2O3 nanotowers mainly contribute for the H2 sensing mechanism. The growth mechanism of the In2O3 nanotowers can be described to be the Vapor-Solid (VS) process.
“…As for the growth mechanisms of these In 2 O 3 microcrystals and In 2 O 3 micro‐rods, careful observation revealed that a particle‐like shape was not found on the top of the structures as it would be in the case of VLS process often reported as the growth mechanism on Au‐catalyzed In 2 O 3 1D‐structures . Therefore, the growth mechanism associated with our structures cannot be explained by the well‐known VLS mechanism.…”
In 2 O 3 rods with dodecahedron In 2 O 3 microcrystals on top were synthesized in an electrical furnace via Au-catalyzed vapor transport process. A catalyst-assisted selective vapor-solid (VS) growth was proposed to explain the formation of the dodecahedron In 2 O 3 microcrystal, while the self-catalytic VS growth mechanism dominated the subsequent one-dimensional (1D) growth of the In 2 O 3 rod underneath the In 2 O 3 microcrystal. The structural evolution of these structures was carefully examined during the synthesis process by controlling the growth parameters. The morphologies, crystalline structures and surface chemistry were characterized by scanning electron microscopy (SEM), X-ray diffraction technique (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. The photoluminescence (PL) spectrum at room temperature of the as-grown In 2 O 3 structures exhibited both UV and blue luminescence emission under one excitation at 260 nm, which may be related to the existence of oxygen vacancies. The synthesized multifaceted In 2 O 3 microcrystal has shown to contain a large number of vertices and may find many applications in developing threedimensional (3D) resonators. This work will not only enrich the synthesis science but also will open doors for applications of such structures in optical devices.
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