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Development of Highly-Sensitive Surface Acoustic Wave (SAW)-based UV Corona Sensor Array with Portable Interface Electronics
- Author(s)
- 김시혁
- Alternative Author(s)
- Sihyeok Kim
- Advisor
- 이기근
- Department
- 일반대학원 전자공학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2023-02
- Language
- eng
- Keyword
- Core-shell heterostructure; Corona sensor; In2O3; Interface electronics; Nanoparticles; Nanorod; SAW sensor; Ta2O5; UV sensor; ZnO
- Alternative Abstract
- As the world is progressing so fast, numerous high-voltage and high-power facilities are employed in various application fields. Aging and deterioration of the power equipment cause various defects and corona discharge phenomena, which leads to serious unpredicted accidents. Accordingly, accurate and prompt diagnosis of such defects in real-time is attracting attention as a critical issue. Recently, various types of corona sensors have been reported including infrared (IR) cameras, ozone or chemical gas sensors, acoustic emission (AE) sensors, ultra-high frequency (UHF) sensors, and UV cameras. However, low sensitivities, slow response, vulnerability to interference from electrical noise and sunlight, difficulty in determining the location of corona discharge origin and high-cost limit their real applications. The UV sensor is one of the candidates for detecting corona discharge. But, conventional UV sensor technologies based on MOSFETs, photodiodes, and transistors require an external bias voltage for sensing materials. This causes several problems such as voltage/current fluctuations due to external electrical noise and long-term stability issues. The surface acoustic wave (SAW) UV sensor is a promising alternative technology because it does not require any external biasing. Nevertheless, several issues such as low sensitivity, slow response/recovery time, low selectivity, environmental interference as temperature and humidity effect, and the need for a specific measurement system are still challenging to be solved. <br>In this dissertation, a novel UV corona sensor system including surface acoustic wave (SAW) sensor arrays and their interface electronics is proposed. The main research objectives for realizing the system can be classified into: i) Optimal design of SAW sensor platform, ii) Optimization of UV-corona sensing materials, iii) 2x2 sensor array and their electronic interfaces. <br>Before device fabrication, coupling of mode (COM) modeling and COMSOL simulation were conducted to determine the optimal parameters for the SAW-based UV sensor. Sequentially, three sensors using different UV corona sensing materials have been developed including Ta2O5 passivated ZnO/SnO2 heterostructure, In2O3/Ta2O5 core-shell heterostructure and Ta2O5 nanoparticle structure respectively. Each sensor exhibited excellent sensing performance for a particular aspect. The ZnO/SnO2/Ta2O5 heterostructure presented high sensitivity of 120.36 (ppm (mW/cm2)-1) and fast recovery/recovery compared to the previous ZnO-based UV sensors. The experimental results indicated that the ultrathin coating of a Ta2O5 layer over the ZnO/SnO2 core-shell structure effectively suppressed the recombination of photogenerated electrons and holes, resulting in an increase in the charge carrier density and a decrease in surface recombination. Using COMSOL simulations and photo corrosion experiments, we also found that the Ta2O5-coated ZnO/SnO2 core-shell heterostructure minimizes the effects of humidity and improves stability. <br>In2O3/Ta2O5 core-shell heterostructure shows high sensitivity of 368.3 (ppm (mW/cm2)-1) and high UV selectivity indicating that photogenerated electron-hole pairs were effectively separated resulting in improvement of carrier lifetime and charge carrier density. <br>Hydrothermally synthesized Ta2O5 nanoparticles show the highest UV-C selectivity and sensitivity (1621.1 (ppm (mW/cm2)-1)) in the range of 0.5–5 μW/cm2. During the day and night operation, similar sensor performance was observed without any sunlight interference due to its high UV-C selectivity. Also, the sensing mechanism of the SAW-based UV corona sensor was identified by separately describing the mass-loading effect and the acoustoelectric effect, this will contribute to the efficient SAW sensor design in future studies. <br>Additionally, a 2x2 sensor array, a reference device and their interface electronics were developed to detect and exactly locate the position of corona discharge. The interference of the surrounding environment, such as temperature and humidity was effectively compensated by the reference device, and the frequency responses of four sensor channels due to corona discharge located in different directions were monitored in real-time. <br>Finally, the feasibility of corona discharge detection with a similar environment to the real-field application was demonstrated using the proposed system. Based on all of the theoretical and experimental studies, it is considered that our novel SAW-based UV corona sensor system will be used effectively in various fields and be able to contribute the society.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Electronic Engineering > 4. Theses(Ph.D)
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