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An In-Depth Study on Electrical and Hydrogen Sensing Characteristics of ZnO Thin Film with Radio Frequency Sputtered Gold Schottky Contacts
摘要： Electrical and hydrogen sensing characteristics of radio frequency sputtered Au/ZnO thin film Schottky diodes on n-silicon substrate have been investigated over a wide temperature range. Current-voltage characterizations of the device in the temperature range of 25°C to 200°C confirm its excellent rectifying property with forward to reverse current ratio of 1610 at an external bias of 5 V. Ideality factor in the range of 4.12 to 2.98 is obtained for Au/ZnO Schottky diode in the aforementioned temperature range, at atmospheric conditions. On exposing diode to hydrogen, a reduction in ideality factor is observed which makes thermionic emission more prominent. The proposed device has proven to be hydrogen sensitive, on account of the lateral shift observed in I ? V characteristics at different hydrogen concentrations (50 ppm-1000 ppm). Maximum barrier height variation of 99 meV and sensitivity of 144% have been observed at 1000 ppm hydrogen at 200°C. A Detailed perusal of the steady-state reaction kinetics of the sensor using I ? V characteristics affirmed that the atomistic hydrogen adsorption at Au/ZnO interface is accountable for the barrier height modulation. The studied sensor depicts remarkable performance for high-temperature detection.
关键词： Hydrogen sensing,Zinc oxide (ZnO) thin film,Electrical characteristics,Schottky diode,Metal-semiconductor interface,Palladium catalyst
更新于2025-09-23 15:22:29
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Design and Mechanism of Embedding Specific Carbon Nanotubes in Sputtered Sandwiched InGaZnO Thin Film Transistors
摘要： Amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) with high mobility are highly desirable to achieve high-speed operation in active-matrix displays and large-area sensors. Only a few works provided potential solutions. In this work, we have embedded carbon nanotubes (CNTs) into sputtered a-IGZO film to form a-IGZO/CNT/a-IGZO (ACA) sandwiched channel. In the ACA channel, the CNT percolation networks connected by the a-IGZO film work as high-speed carrier paths to enable faster transport of carriers during the on state while it does not degrade the leakage performance during the off state. The type and the embedding location of the CNT percolation network are critical to determine the ACA device performance, which is analyzed and verified by experiment and simulation. The optimum ACA design has approximately doubled the mobility and the on current density of the TFT. The design owns relatively better uniformity and provides a high-speed TFT solution for the advanced electronics.
关键词： mobility,amorphous indium gallium zinc oxide,carbon nanotube,thin film transistor,sandwiched structure
更新于2025-09-23 15:22:29
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Plasma-Assisted Chemical Vapor Synthesis of Aluminum-Doped Zinc Oxide Nanopowder and Synthesis of AZO Films for Optoelectronic Applications
摘要： Transparent conducting oxide aluminum-doped zinc oxide (AZO) nanoparticles were synthesized by a plasma-assisted chemical vapor synthesis route using zinc nitrate and aluminum nitrate as the precursors. The injected precursors vaporized in the plasma flame, followed by vapor-phase reaction and subsequent quenching of the vaporized precursors, producing nanosized AZO powder. The amount of aluminum nitrate was varied to obtain samples with 2 at.%, 4 at.% and 8 at.% Al, designated as AZO1, AZO2 and AZO3, respectively. The XRD patterns of the AZO1 and AZO2 nanoparticles indicated the presence of a wurtzite structure without any alumina peaks except in the AZO3 sample, and scanning electron microscopy micrographs revealed spherical particles. The magnetization measurements revealed a ferromagnetic behavior at room temperature in the AZO1 sample, and the ferromagnetic order is decreased in the high field region with an increase in the Al doping amount. AZO thin films were deposited on glass substrates by spin-coating a dispersion of nanoparticles. All the AZO films had a hexagonal wurtzite structure and exhibited a c-axis preferred orientation perpendicular to the substrate. The Hall effect measurements yielded a minimum resistivity of 9.9 × 10?? Ω cm for the AZO2 film and optical transmission of 80% for both the AZO1 and AZO2 films. However, with 8 at.% Al in the AZO3 film, deterioration in crystallinity, electrical and optical properties were observed. Post-annealing of the AZO1 film in H2 atmosphere caused a significant decrease in resistivity from 1.2 × 10?3 Ω cm to 8.7 × 10?? Ω cm. The optical band gap energies of the AZO films were determined from the transmission spectra. The blue shift in the band gap from 3.2 eV to 3.28 eV, observed with an increase in Al doping, was interpreted by the Burstein–Moss effect. The photoluminescence spectra of the AZO films revealed a UV near-band edge emission and a green emission peak.
关键词： Plasma,optoelectronics,doped-zinc oxide,chemical vapor synthesis
更新于2025-09-23 15:22:29
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Multi- and single-step in-situ microwave annealing as low-thermal-budget techniques for solution-processed indium–gallium–zinc oxide thin films
摘要： In this study, low-thermal-budget in-situ microwave annealing of solution-processed indium–gallium–zinc oxide (IGZO) thin films was investigated as a potential alternative to the conventional high-thermal-budget annealing process. The low-temperature baking and high-temperature post-deposition annealing of the solution-processed IGZO film were continuously performed using the same microwave equipment, leading to a reduced heat treatment processing time and temperature. We compared the electrical characteristics of IGZO thin film transistors (TFTs) produced using single- and multi-step in-situ microwave annealing methods with those of TFTs manufactured via the conventional annealing method and found that the proposed single-step microwave annealing method yielded TFTs with electrical characteristics better than those of the TFTs fabricated using the multi-step and conventional annealing methods. In addition, the reliability was evaluated by conducting positive and negative gate bias stress tests, in which the IGZO TFTs manufactured using the proposed heat treatment method proved superior to those fabricated via the conventional heat treatment method. We investigated the effects of heat treatment on the composition and energy band structures of the IGZO films by performing X-ray photoelectron spectroscopy analysis and found that the proposed in-situ microwave annealing method is more effective than the conventional method in solution processing.
关键词： low thermal budget,indium-gallium-zinc oxide,Microwave,solution process
更新于2025-09-23 15:21:21
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Influence of Electrochemical Deposition Parameters on Morphological Properties of ZnO on Si (100)
摘要： In this study, ZnO layer was deposited on Si (100) by electrochemical deposition (ECD) technique. Mixture of zinc chloride (ZnCl2) and potassium chloride (KCl) at different volume ratio was used as the electrolyte. The current density was fixed at 10 mA/cm2 with deposition time of 50 and 30 minutes. The effect of substrate treatment has also been observed to improve the adhesion of the deposited layer. The morphology of the ZnO layer was analyzed using field emission scanning electron microscopy (FESEM), and variable pressure scanning electron microscopy (VPSEM) equipped with energy dispersive X-ray (EDX) module. Four types of ZnO structure had been obtained; needle, flake, coral and pillar-like structures at different deposition conditions. These structures were obtained by changing several parameters such as substrate doping and chloride medium of electrolyte. It was found that the flake-size become smaller as the amount of Chloride ion (Cl-) in electrolyte increased. In addition, substrate type also found to affect the deposition process. As indicated by the EDX spectra, the ZnO is managed to fully cover the target area of deposition for the n-type Si substrate but a bit poor on p-type Si substrate. The targeted EDX ratio of Zn:O is 1:1, which indicates balance stoichiometry of ZnO. However, the best EDX ratio of Zn:O found in this study was only 1.4:1 which was achieved from deposition on p-type Si substrate with no post-annealing applied. The thickness of deposited ZnO was found to decrease with decreasing deposition time. The average thickness was more than 150 μm for 50 minute deposition while 30 minutes deposition yielded thickness less than 100 μm. It is clearly shown that parameters such as time, electrolyte volume ratio and substrate doping have influence on the morphology and thickness of the deposited ZnO on Si (100) by ECD process.
关键词： morphology,electrochemical deposition,zinc oxide
更新于2025-09-23 15:21:21
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Design guidelines for high sensitivity ZnO nanowire gas sensors with Schottky contact
摘要： Zinc oxide nanowire (ZnO NW) gas sensor with single Schottky contact is capable of sensitive detection of gas molecules. In this study, we investigate the effect of design factors such as nanowire defect density, diameter, and length on the gas sensitivity using 3-D numerical simulation. The sensor with lower defect density or smaller NW diameter exhibits improved gas sensitivity, while length does not have an impact when not considering the external environment such as background gases and binding probability. Lower defect density causes low electron density within the NW in air environment, and the change in electron density due to gas adsorption is intensified, thus improving gas sensitivity. As the NW diameter decreases, the change in the electrical conductivity due to gas molecules is greatly increased due to an increase in the ratio of the depletion area to the entire NW area. In contrast, the nanowire length does not impact the gas sensitivity because the change in the electron density is independent of the length. These results are helpful to understand the sensing mechanism and provide design guidelines to maximize the sensitivity.
关键词： Zinc oxide,Gas sensitivity,Nanowire,Numerical simulation,Gas sensor
更新于2025-09-23 15:21:21
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Optical and Structure Analysis of ZnO:Al Film
摘要： ZnO and ZnO:Al are wide-bandgap semiconductors which have many applications, mainly as transparent conducting films. Thin films of these compounds were deposited onto glass and silicon substrates by RF magnetron sputtering for the investigation of structural and optical characteristics. The XRD results show that the films present wurtzite structure. The formation of a polycrystalline film having a preferential crystallographic orientation in the plane (002) is observed in the doped samples. The Al incorporated films exhibited optical transmittance above 80% in the visible spectrum and a clear absorption band in the infrared due to free carriers. Additionally, the optical band gap around 3.48 eV is significantly above intrinsic ZnO (3.25 eV). Photoluminescence (PL) measurements showed a broad emission band in the visible region. In addition, PL emission lines at 3.32 and 3.37 eV showed up in Al incorporated films, and were related to excitonic emissions. The results show that the Burstein-Moss effect plays a central role in determining the optical characteristics of the doped material.
关键词： AZO,Zinc Oxide,Burstein-Moss
更新于2025-09-23 15:21:21
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Structural, optical and photocatlytic properties of zinc oxide nanoparticles obtained by simple plant extract mediated synthesis
摘要： We report a facile and inexpensive method to prepare zinc oxide nanoparticles with different particle size and shape using Achyranthes aspera and Couroupita guianensis leaf extracts as the reducing agent and zinc nitrate as a precursor. The prepared zinc oxide nanoparticles were analyzed by various characterization methods and obtained results evidently revealed that crystalline parameter, purity, optical absorption, band gap, particle size and shape of the ZnO nanoparticles significantly influenced by the type of leaf extract used as reducing agent. Further, photocatlytic activity study obviously demonstrates that prepared samples exhibits superior photocatlytic activity for the degradation of methylene blue dye by creating superoxide anion radicals and OH radicals under photonic irradiation. Hence, prepared zinc oxide nanoparticles by plant extract mediated synthesis can be applied as a photocatlyst for the possible waste water treatment in textile industry.
关键词： Waste water treatment,Photocatalytic activity,Plant extract mediated synthesis,Methylene blue dye,Zinc oxide nanoparticles
更新于2025-09-23 15:21:21
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Zinc Oxide Nanoparticles Synthesized by Suaeda japonica Makino and Their Photocatalytic Degradation of Methylene Blue
摘要： Green chemistry gained special attention for the environmental safety. In addition, green synthesized plant based nanoparticles for the degradation of industrial pollutant dye also received special focuses. Thus, photocatalytic activity of nanosized zinc oxide (Sj-ZnONps) synthesized by a simple co-precipitation method using sodium hydroxide, zinc nitrate, and Suaeda japonica extract as starting materials was carried out. The reaction was implemented in comparatively low temperature (50oC) without further calcination. The absorption spectrum demonstrated an extinction peak at ~362 nm, which is characteristic to the ZnO nanoparticles. Field-emission transmission electron microscope revealed smaller agglomeration of hexagonal Sj-ZnONps (~100 nm). X-ray diffraction patterns exposed polycrystalline ZnO with hexagonal wurtzite structure. The self-assembly of Sj-ZnONps was achieved due to the capping of phytoconstituents present in extract as evident from Fourier-transform infrared spectroscopy analysis. The photocatalytic degradation of Sj-ZnONps was estimated in reduction of methylene blue (MB). The reaction mixtures comprising of MB, S. japonica extract and Sj-ZnONps had the most significant decrease of MB by 54 %. In conclusion, the Sj-ZnONps can be used as a photocatalyst for decomposition of organic pollutions present in water.
关键词： Photocatalytic degradation,Green synthesis,Suaeda japonica Makino,Methylene blue,Zinc oxide nanoparticles
更新于2025-09-23 15:21:21
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Nanocrystalline ZnO Obtained by the Thermal Decomposition of [Zn(H2O)(O2C5H7)2] in 1-Butanol: Synthesis and Testing as a Sensing Material
摘要： The influence of conditions of heat treatment of a solution [Zn(H2O)(O2C5H7)2] in 1-butanol (temperature 125–185°C, treatment times 2, 4, and 6 h) on dispersion and microstructure of the formed nanocrystalline and poorly aggregated zinc oxide, promising component for optoelectronics, including as receptor materials of chemical gas sensors, was investigated. IR spectroscopy showed that the precursor decomposition occurs through the cleavage of the Cβ–Cγ bond of the ligand to form acetone and butyl acetate. It was determined that at the minimum treatment temperature and time (125°C, 2 h) ZnO nanoparticles are nearly spherical, and under hard conditions, rodlike particles are formed. At 125°C (treatment times 4 and 6 h), rodlike particles are organized into dense agglomerates resembling bundles in shape, and at the higher temperatures there is no aggregation of ZnO nanoparticles. The high CO selectivity and sensitivity (4–100 ppm) was revealed for oxide coatings obtained by screen printing using ZnO nanopowders synthesized at 125°C (treatment times 2 and 4 h).
关键词： ZnO,acetylacetonate,zinc oxide,gas sensor,nanoparticles,1-butanol
更新于2025-09-23 15:21:21