KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 9 of 9

Some of the metrics are blocked by your
consent settings
Ultraviolet response of ZnO nanorod/Sb-doped ZnO thin film homojunction structure prepared by all-chemically wet process
(2025-02-01)
Boonyarattanakalin, Kanokthip
;
Sinornate, Wuttichai
;
Mimura, Hidenori
;
Mekprasart, Wanichaya
;
Pecharapa, Wisanu
In this work, ZnO nanorod/Sb-doped ZnO thin film structure was fabricated and its relevant properties were investigated. The device was prepared by Sb-doped ZnO sol-gel spin coating technique onto ITO substrate annealed in nitrogen atmosphere followed by the hydrothermal process to obtain ZnO nanorod. The crystal structure demonstrates (002) plane dominant hexagonal wurtzite ZnO without phase impurity. The deterioration in the crystal structure of Sb-doped ZnO due to the Sb is incorporated in the ZnO lattice. The element component in each layer is confirmed by depth profile measurement. The low transmittance in the visible region is due to high reflection at the surface of the ZnO nanorod. The electrical measurement confirms that ZnO nanorod/Sb-doped ZnO thin film has p-n homojunction properties under dark conditions and 18 times higher photovoltage than the Sb-doped/undoped ZnO double layer device under UV LED irradiation due to enhanced photon harvesting of ZnO nanorod structure.
Some of the metrics are blocked by your
consent settings
Structural, optical and electrical properties of Sb-doped ZnO/ZnO homojunction thin film structures prepared by sol-gel based coating process under nitrogen annealing atmosphere
(2022-09-01)
Sinornate, Wuttichai
;
Mimura, Hidenori
;
Pecharapa, Wisanu
This investigation focuses on structural, optical and electrical properties of Sb-doped/undoped ZnO double layer structure annealed in nitrogen atmosphere. The double layer film was prepared by sol-gel spin coating technique onto ITO substrate then annealed in nitrogen atmosphere. The crystal structure demonstrates hexagonal ZnO without phase impurity. The deterioration in the crystal structure due to Sb is incorporated in ZnO lattice and nitrogen annealing atmosphere and the decrease in diffraction intensity due to the different thickness of the ZnO film. The existence of Sb atom in the doped ZnO film is confirmed by depth profile measurement. The transmittance spectra exhibit high transparency with interference fringe and the photoluminescence spectrum shows the near-band-edge emission of ZnO without any emission in the visible region. The electrical properties demonstrate diode characteristics and photocurrent under dark and UV irradiation, respectively.
Some of the metrics are blocked by your
consent settings
MORPHOLOGICAL and PHYSICAL PROPERTIES of ZnO NANOSTRUCTURES GROWN on Sb-DOPED ZnO SEEDING FILMS ANNEALED under DIFFERENT ATMOSPHERES
(2021-12-01)
Sinornate, Wuttichai
;
Mimura, Hidenori
;
Pecharapa, Wisanu
In this work, morphological and physical properties of pyramid-like ZnO nanostructures fabricated on Sb-doped ZnO seeding films annealed under different atmospheres are extensively studied. The Sb-doped ZnO seeding films were first prepared by sol-gel spin coating technique onto glass substrate then annealed in nitrogen, air and argon followed by low-temperature hydrothermal process for ZnO nanostructures fabrication. The morphological results exhibit the growth of pyramid-like ZnO nanostructure with increasing density of the ZnO nanostructures. The crystal structure shows pyramid-like ZnO wurtzite hexagonal growth along the c-axis without any impurity phase. The growth of pyramid-like ZnO nanostructures is due to the high growth rate of (002) plane. Photoluminescence spectra exhibit the near-band-edge of all samples while the red emission appears in ZnO nanostructures after the hydrothermal process due to the imperfection in the crystal. The reflectance of ZnO nanostructures covers the visible region with the absorption edge of 375nm. The calculation shows the relevant energy band gaps in the range of 3.26-3.28eV. The difference in hydrothermally grown ZnO nanostructures is significantly affected by different annealing atmospheres.
Some of the metrics are blocked by your
consent settings
Structural, Morphological, Optical, and Electrical Properties of Sol–Gel Derived Sb-Doped ZnO Thin Films Annealed Under Different Atmospheres
(2021-01-01)
Sinornate, Wuttichai
;
Mimura, Hidenori
;
Pecharapa, Wisanu
Herein, undoped and antimony (Sb)-doped zinc oxide (ZnO) thin films are prepared by a sol–gel spin-coating method. The influence of different annealing atmospheres including nitrogen and argon on pertinent properties of the prepared films is scrutinized. Structural, optical, morphological, and electrical properties of all annealed films are investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), ultraviolet–visible spectroscopy, and current–voltage measurement. The XRD results exhibit that the films possess ZnO hexagonal wurtzite without impurity. The deterioration in the crystallinity of the film is highly influenced by Sb dopant and annealing atmosphere exhibiting the decrease in nanoparticle size after annealing in nitrogen, argon atmosphere, and upon doping. XPS results confirm that Sb3+ is well incorporated in ZnO lattice and the shift of XPS spectra in the films annealed in nitrogen atmosphere indicates nitrogen bonding with zinc. The PL spectra exhibit blueshift of near band edge emission due to the Sb dopant substituting in Zn site in ZnO lattice and red-infrared emission induced by Sb dopant. The decrease in electrical resistance of ZnO film can be obtained by Sb doping and annealing in nitrogen atmosphere.
Some of the metrics are blocked by your
consent settings
Influence of oxygen assisted recombination on persistent photocurrent characteristics of ZnO polycrystalline thin films prepared by RF magnetron sputtering
(2020-07-01)
Worasawat, Suchada
;
Neo, Yoichiro
;
Hatanaka, Yoshinori
;
Pecharapa, Wisanu
;
Mimura, Hidenori
Decay characteristics in persistent photocurrent (PPC) of zinc oxide (ZnO) polycrystalline films highly aligned in the hexagonal c-axis direction (0002) deposited by radio frequency magnetron sputtering were investigated. Long-term decay of the photocurrent after turning off UV light illumination has been known as a PPC, which affected the performance of optical and electrical devices. Compared to the case of argon ambient, the decay characteristics were strongly influenced by the oxygen ambient. Our phenomenological model proposed could derive the recombination coefficient from an average waiting time that electrons/holes encounter the oxygen molecules attacking the surface of the ZnO polycrystalline films. The decay time response resulted is explained as a modified hyperbolics with the time constant τ and dispersion parameter β. Our experimental results are adapted to the theoretical equation. Using the average β value, τ dependence on the oxygen volume rate is in agreement with the theoretical one and presented a dispersive process on the surface reaction of oxygen gas. These investigations are useful for applications such as photoconductive sensors, gas sensors and a photocatalytic electrode.
Some of the metrics are blocked by your
consent settings
Persistent photocurrent characteristics of ZnO polycrystalline films prepared by RF magnetron sputtering
(2019-01-01)
Worasawat, Suchada
;
Tasaki, Katsuyosi
;
Neo, Yoichiro
;
Pecharapa, Wisanu
;
Hatanaka, Yoshinori
We study zinc oxide (ZnO) polycrystalline films highly aligned in the hexagonal c-axis direction 0002 deposited by RF magnetron sputtering. Photoconductive decay current characteristics are investigated. The decay current shows a long decay tail called persistent current. This temporal feature is analyzed with regard to the inhomogeneous amorphous semiconductor structure. We conclude that the photo-excited carriers of electrons and holes recombine between spatially separated states near the thermo-activated conduction band edge and those near the valence band edge. Although the activation energy of the recombination process is dependent on the ultraviolet irradiation intensity, under weak values an activation potential of about 0.15 eV is obtained, which clarifies the carrier transport in this polycrystalline system, and may give rise to future applications of this system, e.g., catalytic processes.
Some of the metrics are blocked by your
consent settings
Role of Sb-dopant on physical and optical properties of ZnO thin film deposited by sol-gel-based coating method
(2019-01-01)
Sinornate, Wuttichai
;
Mimura, Hidenori
;
Pecharapa, Wisanu
Sb-doped ZnO films were prepared by sol-gel spin coating technique on glass substrate. The sol-gel was prepared from zinc acetate dihydrate as zinc precursor and diethanolamine as sol stabilizer. Antimony (III) acetate was selected as the precursor of Sb. The doping concentration was varied from 0 to 10 mol%. The films were prepared by spin coating technique following by annealing at 500°C for 2 h in ambient air. The XRD exhibits ZnO hexagonal wurtzite without impurity phase. Their XRD peaks show deterioration in crystallinity that is in accordance with FESEM and TEM images showing decreasing in particle size with increasing doping content. The XPS confirm the existence of Sb3+ that could substitute Zn2+ on the zinc site or zinc vacancy. The photoluminescence results exhibit blue-shift with increasing Sb doping concentration. The transmittance spectra show high transmittance above 90% in visible region.
Some of the metrics are blocked by your
consent settings
Growth of ZnO nano-rods and its photoconductive characteristics on the photo-catalytic properties
(2019-01-01)
Worasawat, Suchada
;
Tasaki, Katsuyoshi
;
Hatanaka, Yoshinori
;
Neo, Yoichiro
;
Mimura, Hidenori
Zinc oxide (ZnO) nano-rods has widely been investigated as a promising material for photo-catalysis, due to its high photocatalytic activity for the ambient gas molecules. Well-aligned ZnO nano-rods arrays were obtained by the two steps growth. Firstly, seeding layer deposition by RF magnetron sputtering, and secondly, nano-rods growth by hydrothermal processes were investigated. Moreover, after the samples were annealed at 450 ºC, these samples were compared in crystalline characteristics and photo-electronic characteristics. The morphology of grown ZnO nano-rods were observed as the hexagonal nano-rods and XRD shows a (002) orientation in wurtzite crystals structure. Annealing processes shows a remarkable improvement of crystallinity. PL measurements showed a steep band edge emission and broad defect states emission and also fairly improvement in crystalline properties by the annealing process. The photoconductivity measurement could lead to investigate the photo-catalytic phenomena on the surface of ZnO nano-rods against the environmental gas molecules. The annealed samples showed a higher photo-conductivity and surface activity for the oxygen gas molecules comparing to the as grown samples.
Some of the metrics are blocked by your
consent settings
Synthesis and characterization of ZnO nanorods by hydrothermal method
(2018-01-01)
Worasawat, Suchada
;
Masuzawa, Tomoaki
;
Hatanaka, Yoshinori
;
Neo, Yoichiro
;
Mimura, Hidenori
Hydrogen generation through solar-driven photoelectrolysis of water is a promising technology for clean power supply. Zinc oxide (ZnO) is often applied to a photoelectrochemical (PEC) cells for water splitting, because ZnO has a favorable band edge that straddles the redox potential of photoelectrolysis in water. In addition, formation of ZnO nanostructure is attracting much attention, since the efficiency of PEC cell largely depends on a surface area of contacts. Here we report a modified hydrothermal method to prepare ZnOnanorods, whose structures can be controlled by changing preparation parameters. Our method includes seeding process by simple dip-coating technique, followed by post annealing process and hydrothermal growth process of ZnO nanostructures. The morphology of the grown ZnO depended on the concentration of the solvent used to form the seed layer formation, post-annealing temperature, and growth temperature. At the seed layer solvent concentration of 0.2 M, the ZnOnanorods were needle-like. At 0.9 M, hexagonal ZnOnanorods were obtained. We have successfully prepared hexagonalZnOnanorods by varying seed layer concentration at 0.9M, annealed at 150 ºC for 2 h and grown at 120 ºC for 1 h.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results