Effect of gamma irradiation on Schottky-contacted vertically aligned ZnO nanorod-based hydrogen sensor.
TL;DR: The impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor is reported and the relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZNO using 1 kGy gamma ray treatment.
Abstract: We report the impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor. RF-sputtered vertically aligned highly c-axis-oriented ZnO NRs were grown on Si(100) substrate. X-ray diffraction shows no significant change in crystal structure at low gamma doses from 1 to 5 kGy. As gamma irradiation doses increase to 10 kGy, the single crystalline ZnO structure converts to polycrystalline. The photoluminescence spectra also shows suppression of the near-band emission peak and the huge wide-band spectrum indicates the generation of structural defects at high gamma doses. At 1 kGy, the hydrogen sensor response was enhanced from 67% to 77% for 1% hydrogen in pure argon at a 150 °C operating temperature. However, at 10 kGy, the relative response decreases to 33.5%. High gamma irradiation causes displacement damage and defects in ZnO NRs, and as a result, degrades the sensor's performance as a result. Low gamma irradiation doses activate the ZnO NR surface through ionization, which enhances the sensor performance. The relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZnO using 1 kGy gamma ray treatment.
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TL;DR: In this paper, several techniques related to the synthesis of ZnO nanostructures and their efficient performance in sensing are reviewed, such as functionalization of noble metal nanoparticles, doping of metals, inclusion of carbonaceous nanomaterials, using nanocomposites of different MO x, UV activation, and post-treatment method of high-energy irradiation on ZnOs, with their possible sensing mechanisms.
323 citations
TL;DR: In this article, the mesoporous In2O3 sensors exhibited good reversibility and repeatability towards hydrogen gas and showed a good selectivity for hydrogen compared to other commonly investigated gases including NH3, CO, ethyl alcohol, styrene, CH2Cl2 and formaldehyde.
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TL;DR: In this paper, a vertically aligned single crystalline ZnO nanorods arrays were grown on a silicon substrate in a CVD reactor using Au as a catalyst, and the structural and morphological properties of the resulting nanorod arrays were studied by means of X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction and field emission scanning microscopy.
38 citations
TL;DR: In this article, a strategy is proposed to synthesize 2D ZnO holey nanosheets by engineering the tunable pore/hole size with controlled oxygen vacancies using the annealing process for H2 detection at room temperature.
Abstract: Conquering the issue of room temperature H2 detection at ppm/ppb level and their fundamental sensing mechanism are vitally needed for the development of highly sensitive/selective sensing devices. Herein, a strategy is proposed to synthesize 2D ZnO holey nanosheets by engineering the tunable pore/hole size with controlled oxygen vacancies using the annealing process for H2 detection at room temperature. 2D ZnO holey nanosheets annealed at 400 °C shows a highly porous network owing to its high surface area, more channels for gas diffusion, and mass transport that exhibits improved gas-sensing performance. ZnO@400 sensor exhibits maximum response of ∼115 (20 times more than ZnO@800 sample) towards 100 ppm of H2 at room temperature. The sensor response (recovery) times of the order ∼9(6) secs recorded to be fastest for ZnO@400 sensor as compared to ZnO@600 (∼19(13) secs) and ZnO@800 (∼27(20) secs) sensor respectively. Further, the ZnO@400 sensor also displays superior repeatability and stability of ∼97−99% after 45 days. The involved gas sensing mechanism has also been verified by carrying out XPS measurements before and after H2 exposure at room temperature that helps to complement the theoretical justification about room temperature metallization effect. Thus, 2D ZnO holey nanosheets turn out to be a pivotal strategy to improve the gas sensing performance due to the synergetic effect of highly porous network and large specific surface areas of 2D nanosheets. The present approach proves to be one of the best methodologies to alleviate the restacking issue of the 2D nanosheets by opening up the inaccessible surfaces.
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TL;DR: In this paper, a ZnO hierarchical nanostructure based gas sensor is presented, which features short response/recovery time and ultra-high output response at room temperature (RT).
Abstract: In this paper, a ZnO hierarchical nanostructure based gas sensor is presented. The proposed implementation features short response/recovery time and ultra-high output response at room temperature (RT). In order to take the advantages of complementary-metal-oxide-semiconductor (CMOS) process in terms of miniaturization and cost-effectiveness, a novel fabrication recipe, consisting of CMOS-compatible techniques, is proposed to form a patterned triple-layer metal, which functions as both interconnection electrodes and catalyst for our reported ZnO hierarchical nanostructure. This enables rapid and local growth of ZnO hierarchical nanostructure directly on a single silicon chip. Reported peak RT output response of 32 (20 ppm NO 2 ) provides a significant 28-fold improvement over the traditional widely adopted nanowire-based gas sensor. Meanwhile, a time efficient gas sensor is also validated by the presented temporal performance with a response and recovery time of 72 s and 69 s, respectively. In addition, compared with the previously demonstrated gas sensors operating at 200–300 °C, the proposed RT sensing completely removes the power-hungry heater and eliminates the related thermal reliability issues. Moreover, the demonstrated process flow well addresses the challenging issues of the traditional mainstream “drop-cast” method, including poor yield, non-uniformity of device performance and low efficiency caused by inevitable manual microscope inspection.
82 citations
TL;DR: A novel method for fabricating a highly sensitive chemical sensor based on a ZnO nanorod array that is epitaxially grown on a Pt-coated Si substrate, with a top–top electrode configuration is reported.
Abstract: We report a novel method for fabricating a highly sensitive chemical sensor based on a ZnO nanorod array that is epitaxially grown on a Pt-coated Si substrate, with a top–top electrode configuration. To practically test the device, its O2 and NO2 sensing properties were investigated. The gas sensing properties of this type of device suggest that the approach is promising for the fabrication of sensitive and reliable nanorod chemical sensors.
81 citations
TL;DR: The results hint toward an epitaxial growth of aligned ZnO NRs on graphene by a vapor-liquid-solid mechanism and establish the importance of defect engineering in graphene for controlled fabrication of graphene-semiconductor NW hybrids with improved optoelectronic functionalities.
Abstract: We demonstrate graphene-assisted controlled fabrication of various ZnO 1D nanostructures on the SiO2/graphene substrate at a low temperature (540 °C) and elucidate the growth mechanism. Monolayer and a few layer graphene prepared by chemical vapor deposition (CVD) and subsequently coated with a thin Au layer followed by rapid thermal annealing is shown to result in highly aligned wurtzite ZnO nanorods (NRs) with clear hexagonal facets. On the other hand, direct growth on CVD graphene without a Au catalyst layer resulted in a randomly oriented growth of dense ZnO nanoribbons (NRBs). The role of in-plane defects and preferential clustering of Au atoms on the defect sites of graphene on the growth of highly aligned ZnO NRs/nanowires (NWs) on graphene was established from micro-Raman and high-resolution transmission electron microscopy analyses. Further, we demonstrate strong UV and visible photoluminescence (PL) from the as-grown and post-growth annealed ZnO NRs, NWs, and NRBs, and the origin of the PL emiss...
71 citations
TL;DR: In this paper, a planar-type structure sensor containing a SnO2 thin film sensitized with micro-sized Pd islands was used for monitoring hydrogen gas at low concentrations of 50ppm-500ppm, with fast response and recovery time.
51 citations
51 citations