scholarly journals The Role of ALD-ZnO Seed Layers in the Growth of ZnO Nanorods for Hydrogen Sensing

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 491 ◽  
Author(s):  
Yangming Lu ◽  
Chiafen Hsieh ◽  
Guanci Su
Keyword(s):  
Zinc Oxide ◽  
Surface Area ◽  
Gas Sensing ◽  
Zno Nanorods ◽  
Clean Energy ◽  
Hydrogen Sensor ◽  
Zno Films ◽  
Hydrogen Sensing ◽  
Highly Sensitive ◽  
Seed Layers

Hydrogen is one of the most important clean energy sources of the future. Because of its flammability, explosiveness, and flammability, it is important to develop a highly sensitive hydrogen sensor. Among many gas sensing materials, zinc oxide has excellent sensing properties and is therefore attracting attention. Effectively reducing the resistance of sensing materials and increasing the surface area of materials is an important issue to increase the sensitivity of gas sensing. Zinc oxide seed layers were prepared by atomic layer deposition (ALD) to facilitate the subsequent hydrothermal growth of ZnO nanorods. The nanorods are used as highly sensitive materials for sensing hydrogen due to their inherent properties as oxide semiconductors and their very high surface areas. The low resistance value of ALD-ZnO helps to transport electrons when sensing hydrogen gas and improves the sensitivity of hydrogen sensors. The large surface area of ZnO nanorods also provides lots of sites of gas adsorption which also increases the sensitivity of the hydrogen sensor. Our experimental results show that perfect crystallinity helped to reduce the electrical resistance of ALD-ZnO films. High areal nucleation density and sufficient inter-rod space were determining factors for efficient hydrogen sensing. The sensitivity increased with increasing hydrogen temperature, from 1.03 at 225 °C, to 1.32 at 380 °C after sensing 100 s in 10,000 ppm of hydrogen. We discuss in detail the properties of electrical conductivity, point defects, and crystal quality of ALD-ZnO films and their probable effects on the sensitivity of hydrogen sensing.

scholarly journals Synthesis and Characterization of c-Axis Oriented Zinc Oxide Thin Film and Its Use for the Subsequent Hydrothermal Growth of Zinc Oxide Nanorods

MRS Advances ◽  
2019 ◽  
Vol 4 (16) ◽  
pp. 921-928
Author(s):  
S.F.U. Farhad ◽  
N.I. Tanvir ◽  
M.S. Bashar ◽  
M. Sultana
Keyword(s):  
Zinc Oxide ◽  
Band Gap ◽  
Seed Layer ◽  
Optical Band Gap ◽  
Zno Nanorods ◽  
Zinc Oxide Nanorods ◽  
Oxide Thin Film ◽  
Yellow Emission ◽  
Zno Films ◽  
Seed Layers

ABSTRACTOriented ZnO seed layers were deposited by three different techniques, namely, simple drop casting (DC), sol-gel derived dip coating (DPC) and spin coating of ball-milled ZnO powder solution(BMD) for the subsequent growth of vertically aligned ZnO nanorods along the substrate normal. X-ray diffraction (XRD) analyses revealed that ZnO(DC) seed layer exhibit the highest preferential c-axis texturing among the ZnO seed layers synthesized by different techniques. The Scanning Electron Microscopy (SEM) analysis evident that the morphology of ZnO seed layer surface is compact and coherently carpets the underlying substrate. ZnO nanorods(NRs) were then grown by hydrothermal method atop the ZnO seeded and non-seeded substrates grown by different techniques to elucidate the best ZnO seed layer promoting well-aligned ZnO Nanorods. The presence of c-axis oriented ZnO(DC) seeding layers was found to significantly affect the surface morphology and crystallographic orientation of the resultant ZnO NRs films. The optical band gap of ZnO(DC) seed and ZnO NRs were estimated to be 3.30 eV and in the range of 3.18 – 3.25 eV respectively by using UV-VIS-NIR diffuse reflection spectroscopy. The room temperature photoluminescence analyses revealed that nanostructured ZnO films exhibit a sharp near-band-edge luminescence peak at ∼380 nm consistent with the estimated optical band gap and the ZnO nanorod arrays are notably free from defect-related green-yellow emission peaks.

scholarly journals Facile synthesis of oriented zinc oxide seed layer for the hydrothermal growth of zinc oxide nanorods

2018 ◽  
Vol 53 (4) ◽  
pp. 233-244 ◽  
Author(s):  
SFU Farhad ◽  
NI Tanvir ◽  
MS Bashar ◽  
MS Hossain ◽  
M Sultana ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Seed Layer ◽  
Room Temperature ◽  
Zinc Acetate Dihydrate ◽  
Zno Nanorods ◽  
Zinc Oxide Nanorods ◽  
Yellow Emission ◽  
Zno Films ◽  
Near Band Edge ◽  
Seed Layers

Oriented zine oxide (ZnO) seed layers were deposited by simple drop casting of zinc acetate dihydrate (ZAD) solution on glass substrates at room temperature followed by a post-heat treatment at 250 oC. X-ray diffraction (XRD) analyses revealed that ZAD solutions with concentration 0.0025 – 0.0100 M produced amorphous type thin films, whereas 0.0200 M ZAD solutions produced ZnO seed layers with a preferential c-axis texturing.The Scanning Electron Microscopy (SEM) analyses evident that the morphology of ZnO seed layer surface is compact and coherently carpets the underlying glass substrate. ZnO nanorods were then grown by hydrothermal method atop the ZnO seeded and non-seeded substrates. The presence of ZnO seeding layers was found to be beneficial for growing ZnO NRs films vertically. The optical bandgap of ZnO seed and ZnO NR were estimated to be in the range of 3.40 – 3.95 eV and 3.20 – 3.25 eV respectively by using UV-VIS-NIR diffuse reflection spectroscopy. The room temperature photoluminescence analyses revealed that nanostructured ZnO films exhibit a sharp near-band-edge luminescence peak at ~380 nm consistent with the estimated optical band gap and the ZnO nanorod arrays are notably free from defect-related green-yellow emission peaks.Bangladesh J. Sci. Ind. Res.53(4), 233-244, 2018

scholarly journals Hydrogen Sensor Of TiO2-Based Nanomaterials

2015 ◽  
Vol 60 (2) ◽  
pp. 935-940 ◽  
Author(s):  
B. Łysoń-Sypień ◽  
K. Zakrzewska ◽  
M. Gajewska ◽  
M. Radecka
Keyword(s):  
Gas Sensing ◽  
Hydrogen Sensor ◽  
Integrating Sphere ◽  
Flame Spray ◽  
X Ray Diffraction ◽  
Hydrogen Sensing ◽  
Transmission Electron ◽  
Optical Spectrometry ◽  
Flame Spray Synthesis ◽  
Reference Atmosphere

Abstract The aim of this research was to examine gas sensing properties of TiO2 based nanomaterials. Nanopowders of Cr doped TiO2 with constant Specific Surface Area, SSA, were obtained using Flame Spray Synthesis technique, FSS. Nanomaterials were characterized by Brunauer – Emmett – Teller adsorption isotherms, BET, X – ray diffraction, XRD, Transmission Electron Microscopy, TEM, optical spectrometry UV – vis with the use of an integrating sphere as well as impedance spectroscopy. Detection of hydrogen was carried out over the concentration range of 50 - 3000 ppm at the temperatures extending from 200 to 400°C and synthetic air working as a reference atmosphere. As a result of experiments it appeared that incorporation of 5 at.% of Cr into TiO2 improved hydrogen sensing features due to small crystallite size and predominance of rutile polymorphic phase.

Aspect ratio-controlled ZnO nanorods for highly sensitive wireless ultraviolet sensor applications

2017 ◽  
Vol 5 (46) ◽  
pp. 12256-12263 ◽  
Author(s):  
Teahoon Park ◽  
Kang Eun Lee ◽  
Nari Kim ◽  
Youngseok Oh ◽  
Jung-Keun Yoo ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Aspect Ratio ◽  
Zno Nanorods ◽  
Sensor Applications ◽  
Highly Sensitive ◽  
Ultraviolet Sensor

Structurally controlled zinc oxide (ZnO) nanorods (NRs) were synthesized for ultraviolet (UV) sensing.

ZnO-Based Gas Sensors Prepared by EPD and Hydrothermal Growth

2015 ◽  
Vol 654 ◽  
pp. 94-98 ◽  
Author(s):  
Roman Yatskiv ◽  
María Verde ◽  
Jan Grym
Keyword(s):  
Gas Sensors ◽  
Room Temperature ◽  
Gas Sensing ◽  
Low Cost ◽  
Zno Nanorods ◽  
Zno Films ◽  
Nanorod Arrays ◽  
Zno Nanorod Arrays ◽  
Current Voltage ◽  
Gas Sensing Properties

Arrays of vertically well aligned ZnO nanorods (NRs) were prepared on nanostructured ZnO films using a low temperature hydrothermal method. We propose the use of the low cost, environmentally friendly electrophoretic deposition technique (EPD) as seeding procedure, which allows the obtaining of homogeneous, well oriented nanostructured ZnO thin films. ZnO nanorod arrays were covered with graphite in order to prepare graphite/ZnO NRs junctions. These nanostructured junctions showed promising current-voltage rectifying characteristics and gas sensing properties at room temperature.

Influence of Al, Ta Doped ZnO Seed Layer on the Structure, Morphology and Optical Properties of ZnO Nanorods

2019 ◽  
Vol 4 (1) ◽  
pp. 45-58
Author(s):  
S. Mageswari ◽  
Balan Palanivel
Keyword(s):  
Zinc Oxide ◽  
Optical Properties ◽  
Band Gap ◽  
Seed Layer ◽  
Hexagonal Phase ◽  
Zno Nanorods ◽  
Oxide Material ◽  
Vertically Aligned ◽  
Doped Zno ◽  
Seed Layers

Background: Zinc oxide (ZnO) is one of the most attractive II-VI semiconductor oxide material, because of its direct wide band gap (3.37 eV) and large binding energy (60 meV). Zinc oxide (ZnO) is a promising semiconductor due to its optimised optical properties. Among semiconductor nanostructures, the vertically aligned one-dimensional ZnO nanorods are very important for nano device application. Methods: Vertically aligned ZnO nanorod arrays were grown on ZnO, aluminum doped ZnO (ZnO:Al), tantalum doped ZnO (ZnO:Ta) and aluminum and tantalum co-doped ZnO (ZnO:Al,Ta) seed layer by hydrothermal method. Results: The X-Ray Diffraction (XRD) investigation indicated the presence of hexagonal phase for the both seed layers and nanorods. The Scanning Electron Microscope (SEM) images of ZnO and doped ZnO seed layer thin-films show spherical shaped nanograins organized into wave like morphology. The optical absorption spectra revealed shift in absorption edge towards the shorter wavelength (blue shifted) for ZnO nanorods grown on ZnO:Al, ZnO:Ta and ZnO:Al,Ta seed layer compared to ZnO nanorods grown on ZnO seed layer. Conclusion: The increase in band gap value for the ZnO nanorods grown on doped ZnO seed layers due to the decrease in crystallite size and lattice constant as evidenced from XRD analysis. The unique property of Al, Ta doped ZnO can be used to fabricate nano-optoelectronic devices and photovoltaic devices, due to their improved optical properties.

scholarly journals W-Sn Mixed Oxides and ZnO to Detect NOx and Ozone in Atmosphere

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 836
Author(s):  
Ambra Fioravanti ◽  
Sara Morandi ◽  
Alessia Amodio ◽  
Mauro Mazzocchi ◽  
Michele Sacerdoti ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mixed Oxides ◽  
Gas Sensing ◽  
Molar Fraction ◽  
Functional Materials ◽  
X Ray Diffraction ◽  
X Ray

Thick films of zinc oxide (ZnO) in form of nanospheres or hexagonal prisms and of tungsten-tin (W-Sn) mixed oxides at nominal Sn molar fraction (0.1, 0.3 and 0.5) were prepared. The functional materials were synthesized and characterized by SEM and TEM, X-ray diffraction, specific surface area measurements, UV-Vis-NIR and IR spectroscopies. The gas sensing measurements highlighted that ZnO is more performant in form of nanoprisms, while W-Sn sensors offer a better response towards NOx and ozone with respect to pure WO3.

Growth of Arrayed ZnO Nanorods from Aqueous Solution at 60°C

2010 ◽  
Vol 123-125 ◽  
pp. 691-694
Author(s):  
Gang Qiang Yang ◽  
Xiao Ping Zou ◽  
Xiang Min Meng ◽  
Gong Qing Teng ◽  
Jin Cheng ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Zinc Oxide ◽  
Low Temperature ◽  
Zno Nanorods ◽  
The Other ◽  
Zinc Oxide Nanorods ◽  
Zno Films ◽  
Growth Mechanisms ◽  
Oxide Nanorods ◽  
Zno Particles

In this paper, zinc oxide nanorods were prepared on many different substrates in the aqueous solution without adding alkali solution at 60°C. A layer of ZnO particles as the seeds for the growth were not needed to be coated on the substrates beforehand. A higher uniform and denser packed array of hexagonal ZnO nanorods forms on the glass substrate than that on the other substrates in our experiments. This technique is applicable for the preparation and patterning of functional ZnO films at low temperature. The growth mechanisms of the as-synthesized ZnO nanorods were also proposed.

scholarly journals Room-temperature hydrogen sensing performance of Nb2O5 nanorod arrays

RSC Advances ◽  
2018 ◽  
Vol 8 (30) ◽  
pp. 16897-16901 ◽  
Author(s):  
Yanan Zou ◽  
Jing He ◽  
Yongming Hu ◽  
Rui Huang ◽  
Zhao Wang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hydrogen Sensor ◽  
Nanorod Arrays ◽  
Hydrogen Sensing ◽  
Highly Sensitive ◽  
Sensing Performance

A hydrogen sensor based on Nb2O5 nanorod arrays was synthesized and exhibited a fast and highly-sensitive response at room temperature.

Ammonia Gas Detection Using Fabricated Zinc Oxide (ZnO) Nanoparticles on Glass Tube Substrates

2018 ◽  
Vol 775 ◽  
pp. 266-271 ◽  
Author(s):  
Kurt Brian Daine B. Punzalan ◽  
Franz Kevin B. Manalo ◽  
Emmanuel A. Florido
Keyword(s):  
Zinc Oxide ◽  
Gas Sensing ◽  
Linear Trend ◽  
Glass Tube ◽  
Ammonium Hydroxide ◽  
Zno Films ◽  
Ammonia Gas ◽  
Layer Adsorption ◽  
Different Temperatures ◽  
Silar Technique

This study aimed to determine the ammonia (NH3) gas sensing ability of zinc oxide (ZnO) films deposited on glass tube substrates via successive ionic layer adsorption and reaction (SILAR) technique. The fabricated films were annealed at different temperatures. The sensor films were exposed to different volumes of ammonium hydroxide (NH4OH), converted to parts per million (ppm). The change in voltage from concentrations 595ppm up to 1189ppm exhibited a linear trend. However, no trend was revealed in concentrations 2378ppm and 3964ppm due to film saturation. Results showed that the films annealed at 250 °C, 300 °C, 350 °C, and 400 °C presented sensitivities of 2.7×10-4V/ppm, 1.0×10-4V/ppm, 2.3×10-4V/ppm, and 1.5×10-4V/ppm with R2values of 0.997, 0.994, 0.904, 0.999 and resolutions of 3.7 ppm/mV, 9.9 ppm/mV, 4.4 ppm/mV, and 6.6 ppm/mV, respectively. Furthermore, this research study had proven that high quality gas sensors may be fabricated at a lower cost.

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