HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Fabrication of In2O3 nanowires for self- heated gas sensor application NGUYEN THANH DUONG Duong.vn Specialized: Materials science (Electronic materials) Supervisor 1: Associate Professor. Nguyen Van Duy Unit: International Training Institute for Materials Science (ITIMS) Signature of supervisor Supervisor 2: Ph.Phùng Thị Hồng Vân Unit: Hanoi University of Natural Resources & Environment Signature of supervisor HANOI, 09/2022 i DECLARATION I hereby declare that this thesis represents my work which has been done after the registration for the degree of Master at the International Training Institute of Materials Science – Hanoi University of Science and Technology and has not been previously included in a thesis or dissertation submitted to this or any other institution for a degree, diploma or other qualifications. Hanoi, 22th April, 2022 Nguyen Thanh Duong ii ACKNOWLEDGEMENT First of all, I am sincerely grateful to my thesis supervisor Assoc. Nguyen Van Duy and Prof.
Nguyen Duc Hoa - International Training Institute of Materials Science, for allowing me this opportunity to be their student; all of their advices, indication, and inspiration during the time I studied and carried out my Master thesis in ITIMS. I am very proud to have their whole guidance, encouragement, and insight which have always been invaluable. I would like to show my gratitude to all of teachers and staff not only in ITIMS but also in HUST to support me, I would like to send special thanks to Mr. Dang Ngoc Son and Mr Lai Van Duy - ITIMS for sharing me the initial experiences and many useful suggestions relevant to my work.
Last but not the least, I would like to thank my family and my friends for their support and encouragement. SUMMARY OF MASTER THESIS In this work, we focused on the fabrication and testing of the H2S gas sensing characteristic of the self-heated In2O3 nanowires sensor via a one-step CVD technique and drop-casting on the IDE electrode. The self-heated In2O3 NWs gas sensor was measured at room temperature with different applied power toward H2S gas. This performance was better than the state-of-the-art microheater gas sensor.
The sensor is a potential candidate for application related to H2S detection such as breath exhaled analysis and environmental monitoring. Hanoi, 20th August, 2022 Master. Student Nguyen Thanh Duong iii CONTENT DECLARATION. vi LIST OF FIGURES .vii LIST OF TABLES.
Foundation of the thesis. Aims of the thesis. Research object and scope of the thesis. New contributions of the thesis.
Structure of the thesis. Self-heated gas sensor. Error! Bookmark not defined. Self-heating effect.
In2O3 materials in gas sensor. In2O3 nanowires in gas sensor. Hazardous properties of H2S gas. Synthesis of In2O3 nanowires.
Equipment and chemical. Fabrication of In2O3 nanowires. Fabrication of self-heated In2O3 gas sensor. RESULT AND DISCUSSION.
Morphology of Indium Oxide (In2O3) synthesized by CVD method and In2O3 NWs based sensor fabricate by drop-casting. Effect of Sn proportion on the morphology of Indium Oxide (In2O3) materials. The distribution of In2O3 NWs in the various isopropanol solvent ratio. The microstructure characterization.
Gas sensing properties.35 CONCLUSION AND RECOMMENDATIONS. 49 v ABBREVIATIONS Abbreviations Number Meaning and symbols 1 ads Adsorption 2 BET Brunauer- Emnet-Teller 3 CVD Chemical Vapour Deposition 4 EDS/EDX Energy-dispersive X-ray spectroscopy 5 HRTEM High Resolution Transmission Electron Microscope 6 IoT Internet of Things International Training Institute 7 ITIMS for Materials Science 8 Nanowires NWs 9 ppb Parts per billion 10 ppm Parts per million 11 Ra Rair 12 Rg Rgas 13 S Sensitivity 14 SEM Scanning Electron Microscope 15 TEM Transition Electron Microscope 16 VOCs Volatile Organic Compounds vi 17 XRD X-ray Diffraction LIST OF FIGURES Figure 1. Detection methods of semiconductor gas sensing materials [1]. Different material classes for gas sensing application [1].
Sensing mechanism of metal oxide based gas sensor [1]. Power consumption and temperature characterized of Hwang WJ’s micro- heater [8]. Sang Chung Gwiy, Jae-Min Young group’s micro heater [9]. KMHP 100 commercial micro heater.
Single SnO2 NW contacted with electron beam assisted platinum deposition in a four probes configuration before (a) and after (b) a few hours of operating in self- heating mode.8: In2O3 crystalline structure. The response of single oxide and composite sensors to 5 ppm ethanol vapor at 100% RH [36]. CVD system - ITIMS. Thermal cycle of In2O3 nanowires fabrication process.
FESEM microscope – HUST. Procedure of self-heated In2O3 NWs based gas sensor. Gas sensitive measuring system at ITIMS (A), Diagram of the gas measuring system by static measurement method (B). Morphology and microstructure of three composite samples at (A),(B): 0 %; (C),(D): 20 %; (E),(F): 50 %; (G),(H): 80 % mass ratio of Sn were observed by SEM scanning electron microscopy.
Distribution of In2O3 NWs onto silicon substrate with (A)10 ml (B)20 ml and (C) 30ml of Isopropanol solvent. SEM image of In2O3 nanowires dispersion on the electrode with various ratio solvent. (a–d) XRD pattern of 0%, 20%, 50 and 80% SnO2/In2O3 NWs. EDX spectrum of (A) Pure In2O3 NWs and (B),(C) SnO2/In2O3 NWs.
The response of self-heated In2O3 gas sensor versus time at different power of 600, 800, 1200, 1200 μW (a) and the function of response with concentration H2S gas (b). The response of self-heated 20% wt SnO2/In2O3 NWs gas sensor versus time at different power of 300, 500 and 700 μW (RT) (a) and the function of response with concentration H2S gas (b). The response of self-heated 50% wt SnO2/In2O3 NWs gas sensor versus time at different power of 300, 500 and 700 μW (RT) (a) and the function of response with concentration H2S gas (b). The response of self-heated 80% wt SnO2/In2O3 NWs gas sensor versus time at different power of 300, 500 and 700 μW (RT) (a) and the function of response with concentration H2S gas (b).10 Response and heating power graph of four fabricated sensors.
The response of self-heated 80% wt SnO2/In2O3 NWs gas sensor versus time at different temperature of 200RC, 250 RC, 300 RC and 350 RC and the function of response with concentration H2S gas. Response characteristic of In2O3 – nanowires gas sensor toward 5 ppm H2S at 250 oC and self-heating with a power consumption of 700 μW. Response characteristic of 80% SnO2/In2O3 NWs gas sensor toward 5 ppm H2S at 250 RC and self-heating with a power consumption of 700 μW. Response to H2S of the 80% wt SnO2/In2O3 NWs sensor used self-heating effect (Orange line) and sensor using the external heater at 200 oC (Blue line).
Stability of sensor A. Self-heated mode. Selectivity of In2O3 NWs gas sensor toward NH3, Ethanol and H2S gas under self-heating mode. In2O3 material H2S gas sensing mechanism.47 ix LIST OF TABLES Table 1.
Summary of publication reporting quantitative information about self-heated devices based on nanomaterial. Publications reported self- heating effects in gas sensor using metal oxide materials. Precusor material in this experiment .1: Comparison with previous study at ITIMS with same approach method. Foundation of the thesis Since the first device was invented by the Greeks to manage the level of water using a floater, similar to those that are used today in water boxes to keep a water container at a constant level, sensors have been used to gather signals from the environment for more than 2000 years.
Many other sensors and actuators, include gas sensors, a branch of the sensor family, have been developed after a thousand years of development. It's critical to monitor gases, humidity, and moisture in areas including agriculture, medicine, and industrial processes. Gas sensors are frequently used to monitor environmental pollution and detect low concentrations of hazardous, flammable, or explosive gases. In many different industries and applications, such as smart building and smart home systems, environmental monitoring, and food quality monitoring, the usage of chemical sensor devices to detect and measure gases has become truly indispensable.
Recently, the Fourth Industrial Revolution is dramatically changing the world with Internet of Things (IoT), cloud computing, 3D Graphic, Augmented Reality, Machine learning, sensor technology and Artificial intelligence. Among them, IoT brings in a lot of advantages in almost aspects of human life. IoT is the result of the fusion of the internet, wireless technology, and micro mechatronics technology, all of which have great utility and are beneficial to human society. Gas sensors and sensor nodes are essential parts of cutting-edge communication systems like the Internet of Things.
Modern sensor requirements for IoT include: (1) dependability; (2) energy consumption; (3) cost; (4) communication ability; and (5) data security. With that being said, alongside with the high requirement of energy saving, promote researches of low power consumption devices are critically important. In addition, the metal oxide-based gas sensor requires thermal energy to activate the interaction between the analytic gas molecule and the sensing material. Self-heated gas sensors have recently been developed to reduce the device's power usage.
It has been proved that Joule self-heating effect is nearly ideal for operating NWs gas sensors at 1 ultralow power consumption, without external heaters. In this thesis, we present an optimal fabrication process of In2O3 multiple NWs as well as the sensing capability of the self-heated networked In2O3 NWs effectively prepared by drop-casting method with H2S gas. Finally, I identify the limitations of these sensors and highlight the most promising approaches to enable the use of these technologies in real-world applications 2. Aims of the thesis - To successfully fabricate self-heated gas sensor based on In2O3 NWs using the chemical vapor deposition method (CVD) and drop-casting method.
- To investigate the microstructure of the synthesized In2O3 NWs as well as comparing self-heated operating mode with using external heater sensor sensitivity toward H2S gas. Research object and scope of the thesis To implement this study with the above objectives, the thesis focused on researching the following key issues: - Fabrication In2O3 NWs and In2O3, SnO2 composite NWs. - Survey of gas sensing properties, analysis of factors affecting the gas sensing characteristics material by using external heaters as well as self-heating operation. Research Methods The thesis was carried out based on experimental methods combined with theoretical research and surveying the published articles.
In details, the In2O3 NWs were synthesized by the CVD method. Morphology and structure properties of the material were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and diffusing X-ray Energy dispersive (EDX). The gas-sensing characteristics of In2O3 NWs -based sensors have studied by static measurement techniques on the gas sensing characteristics of the Air Sensing Group (iSensor.vn) at the ITIMS Institute-Institute for International Scientific Training on scientific research materials University of Technology-Hanoi. New contributions of the thesis By CVD and drop-casting method, the author has successfully synthesized In2O3 nanowires as well as SnO2/In2O3 nanowires which being used to fabricate self-heated gas sensor.
At the same time, the results of the thesis also prove the potential application of In2O3 material in the gas sensor, especially with low power consumption advantage. Structure of the thesis To achieve the proposed goals, the thesis was divided into the following sections: Chapter 1: Overview In this chapter, we present an overview of gas sensor and self-heated gas sensor as well as introducing the In2O3, SnO2 NWs material. Chapter 2: Experimental approach In this chapter, we present the technological process of manufacturing In2O3 nanowire by the CVD method and fabrication of self-heated gas sensor based on In2O3 NWs structure. Introducing the method of surveying morphology of the material, gas- sensitive and electric properties of self-heated gas sensor used in the thesis.
Chapter 3: Result and conclusion In this chapter, we present the results and discuss on the morphology, gas-sensing properties, and the sensitivity mechanism of In2O3 and SnO2/In2O3 material structures. Details on the effect of synthesis condition on the morphology and gas sensing properties of synthesized materials are reported and discussed.