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Cadatal-Raduban M, Pope J, Olejníček J, Kohout M, Harrison JA, Hasan SMR. Ultraviolet-C Photoresponsivity Using Fabricated TiO 2 Thin Films and Transimpedance-Amplifier-Based Test Setup. SENSORS (BASEL, SWITZERLAND) 2022; 22:8176. [PMID: 36365873 PMCID: PMC9657381 DOI: 10.3390/s22218176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 10/18/2022] [Accepted: 10/19/2022] [Indexed: 06/16/2023]
Abstract
We report on fabricated titanium dioxide (TiO2) thin films along with a transimpedance amplifier (TIA) test setup as a photoconductivity detector (sensor) in the ultraviolet-C (UV-C) wavelength region, particularly at 260 nm. TiO2 thin films deposited on high-resistivity undoped silicon-substrate at thicknesses of 100, 500, and 1000 nm exhibited photoresponsivities of 81.6, 55.6, and 19.6 mA/W, respectively, at 30 V bias voltage. Despite improvements in the crystallinity of the thicker films, the decrease in photocurrent, photoconductivity, photoconductance, and photoresponsivity in thicker films is attributed to an increased number of defects. Varying the thickness of the film can, however, be leveraged to control the wavelength response of the detector. Future development of a chip-based portable UV-C detector using TiO2 thin films will open new opportunities for a wide range of applications.
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Affiliation(s)
- Marilou Cadatal-Raduban
- School of Natural Sciences, Massey University, Auckland 0632, New Zealand
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita 565-0871, Osaka, Japan
| | - Jade Pope
- School of Natural Sciences, Massey University, Auckland 0632, New Zealand
| | - Jiří Olejníček
- Department of Low Temperature Plasma, Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 182 21 Prague 8, Czech Republic
| | - Michal Kohout
- Department of Low Temperature Plasma, Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 182 21 Prague 8, Czech Republic
| | - John A. Harrison
- School of Natural Sciences, Massey University, Auckland 0632, New Zealand
| | - S. M. Rezaul Hasan
- Center for Research in Analog and VLSI Microsystem Design, Massey University, Auckland 0632, New Zealand
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Cadatal-Raduban M, Kato T, Horiuchi Y, Olejníček J, Kohout M, Yamanoi K, Ono S. Effect of Substrate and Thickness on the Photoconductivity of Nanoparticle Titanium Dioxide Thin Film Vacuum Ultraviolet Photoconductive Detector. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 12:10. [PMID: 35009959 PMCID: PMC8746592 DOI: 10.3390/nano12010010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/06/2021] [Accepted: 12/10/2021] [Indexed: 06/14/2023]
Abstract
Vacuum ultraviolet radiation (VUV, from 100 nm to 200 nm wavelength) is indispensable in many applications, but its detection is still challenging. We report the development of a VUV photoconductive detector, based on titanium dioxide (TiO2) nanoparticle thin films. The effect of crystallinity, optical quality, and crystallite size due to film thickness (80 nm, 500 nm, 1000 nm) and type of substrate (silicon Si, quartz SiO2, soda lime glass SLG) was investigated to explore ways of enhancing the photoconductivity of the detector. The TiO2 film deposited on SiO2 substrate with a film thickness of 80 nm exhibited the best photoconductivity, with a photocurrent of 5.35 milli-Amperes and a photosensitivity of 99.99% for a bias voltage of 70 V. The wavelength response of the detector can be adjusted by changing the thickness of the film as the cut-off shifts to a longer wavelength, as the film becomes thicker. The response time of the TiO2 detector is about 5.8 μs and is comparable to the 5.4 μs response time of a diamond UV sensor. The development of the TiO2 nanoparticle thin film detector is expected to contribute to the enhancement of the use of VUV radiation in an increasing number of important technological and scientific applications.
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Affiliation(s)
- Marilou Cadatal-Raduban
- Centre for Theoretical Chemistry and Physics, School of Natural and Computational Sciences, Massey University, Auckland 0632, New Zealand
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita 565-0871, Osaka, Japan;
| | - Tomoki Kato
- Department of Physical Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Aichi, Japan; (T.K.); (Y.H.); (S.O.)
| | - Yusuke Horiuchi
- Department of Physical Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Aichi, Japan; (T.K.); (Y.H.); (S.O.)
| | - Jiří Olejníček
- Department of Low-Temperature Plasma, Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Prague, Czech Republic; (J.O.); (M.K.)
| | - Michal Kohout
- Department of Low-Temperature Plasma, Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Prague, Czech Republic; (J.O.); (M.K.)
| | - Kohei Yamanoi
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita 565-0871, Osaka, Japan;
| | - Shingo Ono
- Department of Physical Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Aichi, Japan; (T.K.); (Y.H.); (S.O.)
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Trung DQ, Quang NV, Tran MT, Du NV, Tu N, Hung ND, Viet DX, Anh DD, Huy PT. Single-composition Al 3+-singly doped ZnO phosphors for UV-pumped warm white light-emitting diode applications. Dalton Trans 2021; 50:9037-9050. [PMID: 34160493 DOI: 10.1039/d1dt00971k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The development of full-visible-spectrum phosphors is essential for next-generation light-emitting devices with better light quality. Herein, we report on a novel broad-band-emitting phosphor based on single-composition Al-doped ZnO phosphors. Under the UV excitation of 325 nm, the ZnO : Al phosphor exhibits a full spectrum emission in the visible wavelength range from 400 to 800 nm with a CIE chromaticity coordinate of (0.42, 0.48), a quantum efficiency of 43%, a color rendering index (CRI) of 74, a correlated color temperature (CCT) value of 3873 K and an activation energy of 0.22 eV. A prototype of a UV-pumped warm WLED with a high CRI of 87 and a CCT of 4067 K has been achieved by using only this broad-band-emitting Al3+-doped ZnO phosphor. The obtained results indicate that the single-composition Al3+-singly doped warm white emitting phosphor is a promising candidate for UV-pump warm white light-emitting diodes.
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Affiliation(s)
- D Q Trung
- Phenikaa Institute for Advanced Study (PIAS), Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam. and Phenikaa Research and Technology Institute (PRATI), Phenikaa University, 167 Hoang Ngan, Hanoi 10000, Vietnam and Faculty of Fundamental Sciences, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - N V Quang
- Faculty of Materials Science, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam and Department of Chemistry, Hanoi Pedagogical University 2, Phuc Yen, Vinh Phuc, Vietnam
| | - M T Tran
- Phenikaa Research and Technology Institute (PRATI), Phenikaa University, 167 Hoang Ngan, Hanoi 10000, Vietnam and Faculty of Materials Science, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - N V Du
- Phenikaa Research and Technology Institute (PRATI), Phenikaa University, 167 Hoang Ngan, Hanoi 10000, Vietnam and Faculty of Materials Science, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - N Tu
- Phenikaa Institute for Advanced Study (PIAS), Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam. and Phenikaa Research and Technology Institute (PRATI), Phenikaa University, 167 Hoang Ngan, Hanoi 10000, Vietnam and Faculty of Fundamental Sciences, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - N D Hung
- Advanced Institute of Science and Technology (AIST), Hanoi University of Science and Technology (HUST), N0 01 Dai Co Viet, Hanoi, Vietnam
| | - Dao Xuan Viet
- Advanced Institute of Science and Technology (AIST), Hanoi University of Science and Technology (HUST), N0 01 Dai Co Viet, Hanoi, Vietnam
| | - D D Anh
- Faculty of Materials Science, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
| | - P T Huy
- Phenikaa Research and Technology Institute (PRATI), Phenikaa University, 167 Hoang Ngan, Hanoi 10000, Vietnam and Faculty of Materials Science, Phenikaa University, Yen Nghia, Ha-Dong District, Hanoi 10000, Vietnam
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Effects of Al-Impurity Type on Formation Energy, Crystal Structure, Electronic Structure, and Optical Properties of ZnO by Using Density Functional Theory and the Hubbard-U Method. MATERIALS 2016; 9:ma9080647. [PMID: 28773769 PMCID: PMC5509097 DOI: 10.3390/ma9080647] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 07/23/2016] [Accepted: 07/27/2016] [Indexed: 11/17/2022]
Abstract
We systematically investigated the effects of Al-impurity type on the formation energy, crystal structure, charge density, electronic structure, and optical properties of ZnO by using density functional theory and the Hubbard-U method. Al-related defects, such as those caused by the substitution of Zn and O atoms by Al atoms (Als(Zn) and Als(O), respectively) and the presence of an interstitial Al atom at the center of a tetrahedron (Ali(tet)) or an octahedron (Ali(oct)), and various Al concentrations were evaluated. The calculated formation energy follows the order Ef(Als(Zn)) < Ef(Ali(tet)) < Ef(Ali(oct)) < Ef(Als(O)). Electronic structure analysis showed that the Als(Zn), Als(O), Ali(tet), and Ali(oct) models follow n-type conduction, and the optical band gaps are higher than that of pure ZnO. The calculated carrier concentrations of the Als(O) and Ali(tet)/Ali(oct) models are higher than that of the Als(Zn) model. However, according to the curvature of the band structure, the occurrence of interstitial Al atoms or the substitution of O atoms by Al atoms results in a high effective mass, possibly reducing the carrier mobility. The average transmittance levels in the visible light and ultraviolet (UV) regions of the Als(Zn) model are higher than those of pure ZnO. However, the presence of an interstitial Al atom within the ZnO crystal reduces transmittance in the visible light region; Als(O) substantially reduces the transmittance in the visible light and UV regions. In addition, the properties of ZnO doped with various Als(Zn) concentrations were analyzed.
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