Research and synthesis of sno2 nanowirestransition metal dichalcogenides heterostructure towards gas sensing applications

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Research and synthesis of SnO2 nanowires/ transition metal dichalcogenides heterostructure towards gas sensing applications TRUONG TIEN HOANG DUONG duong.tth202767M@sis.hust.edu.vn Materials Science Supervisor: Dr Chu Manh Hung Institute: International Training Institute for Materials Science Hanoi, 05/2022 HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Research and synthesis of SnO2 nanowires/ transition metal dichalcogenides heterostructure towards gas sensing applications TRUONG TIEN HOANG DUONG duong.tth202767M@sis.hust.edu.vn Materials Science Supervisor: Dr Chu Manh Hung Institute: International Training Institute for Materials Science Hanoi, 05/2022 Supervisor’s signature THESIS TOPIC Research and synthesis of SnO2 nanowires/ transition metal dichalcogenides heterostructure towards gas sensing applications SUPERVISOR Dr Chu Manh Hung SOCIALIST REPUBLIC OF VIETNAM Independence – Freedom - Happiness CONFIRMATION OF MASTER’S THESIS ADJUSTMENT Full name of author: Truong Tien Hoang Duong Thesis topic: Research and synthesis of SnO2 nanowires/ transition metal dichalcogenides heterostructure towards gas sensing applications Major: Materials Science Student ID: 20202767M The author, the supervisor, and the Committee confirmed that the author has adjusted and implemented the thesis according to the report of the Committee on May 19th, 2022 with the following contents: - Figure format - Bibliography format Day month year Supervisor Author Dr Chu Manh Hung Truong Tien Hoang Duong COMMITTEE’S CHAIRMAN Prof Vu Ngoc Hung Acknowledgements First of all, I would like to express my deepest gratitude to my supervisor, Dr Chu Manh Hung, for his thoughtful feedback and conscientious guidance throughout my master’s program His expertise and critical thinking in science is what I want to achieve in my future career I also extend my gratitude to Prof Nguyen Duc Hoa and Assoc Prof Nguyen Van Duy for their valuable suggestions and explanations regarding my research topic I would also like to take this chance to express my special thanks to my very first advisor, Dr Le Minh Hai, whose perspective and knowledge have inspired and guided my research interests since my undergraduate days In appreciation of my peers, I would like to thank my lab mates and classmates for their friendly and helpful collaboration, and especially Ho Huu Hau for accompanying me throughout experiments and discussions I am grateful to my senior Nguyen Ngoc Yen for her constant emotional support and mentoring that helped me overcome difficult times during my study To my best friend Tuc Anh, thank you for always being by my side Last but not least, I would like to express my sincere gratitude to my family for their constant, unconditioned love and care I also acknowledge the financial and motivational support from Vingroup Innovation Foundation during the course of my master’s program i Abstract In the modern era, where air pollution is a serious threat to human health, gas sensors have become an essential device in every home, facility, and workplace to monitor the state of the environment and prevent potential health risks Conventional gas sensors usually involve the use of semiconducting metal oxides, with SnO2 as one of the most studied candidates, due to their high sensitivity, excellent stability, and low cost However, they require high temperature (200-600 o C) to exhibit the highest sensing performance, thus increasing power consumption In recent years, TMDs have become a rising star in many electronic applications and devices, because of their unique structural, chemical and electrical characteristics TMDs gas sensors are particularly promising due to their ability to operate even at room temperature; therefore, a SnO2/TMD heterostructure gas sensor is believed to have an enhanced gas sensing performance with a relatively low working temperature This thesis focuses on the fabrication of SnO2 NW/WS2 heterostructure gas sensors via physical approaches followed by a facile drop casting method The as-obtained heterostructure gas sensors showed enhanced gas response and selectivity towards NO2, and the working temperature is lowered compared to that of the SnO2 NW gas sensor This result contributes to the development of a new generation of gas sensors with high performance and low energy consumption STUDENT Truong Tien Hoang Duong ii TABLE OF CONTENTS INTRODUCTION CHAPTER LITERATURE REVIEW 1.1 1.2 1.3 SnO2 nanowires 1.1.1 Crystal structure of SnO2 1.1.2 Electrical properties of SnO2 1.1.3 On-chip growth of SnO2 nanowires by thermal evaporation 1.1.4 SnO2 NW gas sensors Two-Dimensional Transition Metal Dichalcogenides (WS2) 1.2.1 Crystal structure of WS2 1.2.2 Electrical properties of WS2 1.2.3 Fabrication methods 1.2.4 WS2-based gas sensors 12 SMO/TMD heterostructure gas sensors 13 CHAPTER EXPERIMENTAL DETAILS 16 2.1 2.2 Synthesis of on-chip SnO2 NWs by evaporation method 16 2.1.1 Fabrication of interdigitated Pt chips 16 2.1.2 Fabrication of on-chip SnO2 NWs by the evaporation method 16 Synthesis of TMD nanomaterials 17 2.2.1 Fabrication of WS2 NSs 17 2.3 Synthesis of SnO2 nanowire/ TMD nanomaterial heterojunction gas sensors 18 2.3.1 2.4 Fabrication of WS2@SnO2 gas sensor 18 Characterization methods 18 2.4.1 X-Ray Diffraction 19 2.4.2 Raman spectroscopy 19 2.4.3 Ultraviolet-Visible Spectroscopy (UV-Vis) 20 2.4.4 Scanning Electron Microscope and Energy-Dispersive X-ray Spectroscopy 20 2.4.5 Transmission Electron Microscopy and Selected-Area Electron Diffraction 20 2.5 Gas sensing measurement 21 CHAPTER RESULTS AND DISCUSSION 23 3.1 SnO2 NW gas sensor 23 iii 3.2 3.3 3.1.1 Structure and morphology 23 3.1.2 Gas sensing performance 24 WS2 NS gas sensor 28 3.2.1 Influence of solvent in the LPE of WS2 29 3.2.2 Structure and morphology 29 3.2.1 Gas sensing performance 30 SnO2@WS2 gas sensor 36 3.3.1 Structure and morphology 36 3.3.2 Gas sensing performance 39 CONCLUSIONS AND FUTURE WORK 45 LIST OF PUBLICATION 46 REFERENCES 47 iv LIST OF ABBREVIATIONS TMDs Transition Metal Dichalcogenides SMOs Semiconducting Metal Oxides LPE Liquid-Phase Exfoliation CVD Chemical Vapor Deposition NWs Nanowires NSs Nanosheets VS Vapor -Solid VLS Vapor-Liquid-Solid XRD X-ray Diffraction FESEM Field Emission Scanning Electron Microscopy HRTEM High Resolution Transmission Electron Microscopy SAED Selected-Area Electron Diffraction EDX Energy-dispersive X-ray spectroscopy JCPDS Joint Committee on Powder Diffraction Standards sccm Standard cubic centimeters per minute ppm Parts per million ppb Parts per billion v LIST OF FIGURES Fig 1.1 Unit cell of rutile SnO2 [18] Fig 1.2 Different structures of TMDs: a) 1H, b) 1T, c) 1T’, d) 1T”, e) 2H, and f) 3R [60] Fig 1.3 Layer-dependent band structures of WS2 ultrathin films [65] Fig 1.4 (a) Step-by-step process of TMD hydrothermal synthesis and (b) sequential phenomena appear in hydrothermal reactions [69] 10 Fig 1.5 Liquid-phase exfoliation routes for 2D TMDs Adapted from Ref [85] 11 Fig 1.6 (a-b) TEM and HRTEM of WS2-WO3 hybrid Gas responsive curve to ppm at 25 °C of (c) WS2 and (d) WS2-WO3 gas sensor (e) Responsive curve to different NO2 concentrations of WS2-WO3 gas sensor at 25 °C, (f) Energy band structure of WS2-WO3 heterojunction [110] 14 Fig 2.1 Interdigitated Pt electrodes 16 Fig 2.2 Schematic diagram of the on-chip fabrication of SnO2 NWs 17 Fig 2.3 Schematic illustration of the LPE of WS2 NSs 18 Fig 2.4 Fabrication of WS2@SnO2 gas sensors by drop casting 18 Fig 2.5 (a) Gas sensing measurement setup at ITIMS and (b) Inside the test chamber 21 Fig 3.1 XRD spectrum of SnO2 NWs grown on interdigitated Pt electrode 23 Fig 3.2 (a-c) SEM images of on-chip SnO2 NWs, with inset showing the corresponding interdigitated electrodes (d) EDX spectrum of SnO2 NWs 24 Fig 3.3 (a) Transient resistive curves to different NO2 concentrations of SnO2 NW gas sensor and (b) the corresponding gas response at different temperatures, (c) response and recovery times of the SnO2 NW gas sensor at 200 °C 25 Fig 3.4 I-V characteristic of SnO2 NW gas sensor 26 Fig 3.5 (a) Linear fit of gas response as a function of NO2 concentration and (b) Arrhenius polynomial fit of 40 base resistance data points of SnO2 NW gas sensor at 200 °C 27 Fig 3.6 Selectivity of the SnO2 NW gas sensor at 200 °C 27 Fig 3.7 NO2 sensing mechanism of SnO2 NW gas sensor 28 Fig 3.8 UV-Vis absorption spectra of exfoliated WS2 using different solvent ratios 29 Fig 3.9 SEM images of (a) bulk WS2 and (b) exfoliated WS2 NSs 30 Fig 3.10 TEM images of (a) exfoliated WS2 NS, with (b) higher magnification of the yellow-dashed region (c) HRTEM image of the red-dashed region (d) SAED pattern of WS2 NSs 30 Fig 3.11 (a) XRD spectrum and (b) Raman scattering spectroscopy of bulk and exfoliated WS2 NSs 30 vi CONCLUSIONS AND FUTURE WORK Conclusions  SnO2 NWs were directly grown on Pt electrodes using a thermal evaporation method, having 40-160 nm in diameter The as-obtained networked SnO2 NW gas sensor showed good linearity, low detection limit, and high gas response (43.1 to ppm NO2) at optimal working temperature of 200 °C  WS2 NSs were successfully exfoliated in an ethanol:water solvent The results showed that WS2 NSs were 2-3 layers in thickness, and the WS2 NS gas sensor showed the highest gas response (10.2 to ppm NO2) at RT, with good stability and minor humidity dependence  WS2@SnO2 heterostructure gas sensors were successfully fabricated by a facile drop casting method The optimal addition of WS2 NSs was found to have a good uniformity and good contact with SnO2 NWs WS2@SnO2 gas sensor showed Schottky characteristic and an enhanced gas response (116 to ppm NO2) with improved selectivity and sensitivity The optimal working temperature of WS2@SnO2 sensor was at 100 °C  The enhancement in gas response to NO2 and working temperature of WS2@SnO2 was explained by the formation of p-n heterojunction as well as by the increase in surface area and active sites Future work For further investigation regarding this research, several future suggestions can be taken into consideration, as listed below:  Investigation of gas sensing performance of the heterostructure between SnO2 NWs and other TMD materials, such as MoSe2, TiS2, etc  Investigation of gas sensing performance of n-p-n SnO2/TMD/SnO2 heterostructures 45 LIST OF PUBLICATION Truong Tien Hoang Duong, Ho Huu Hau, Le Thi Hong, Chu Manh Hung*, Nguyen Van Duy, Le Anh Vu, Nguyen Duc Hoa*, “Pt-decorated MoS2 ultrathin nanoflowers for enhanced NH3 gas sensing”, Materials Science in Semiconductor Processing, Q2 (Under revision) Ho Huu Hau, Truong Tien Hoang Duong, Nguyen Khac Man, Tran Thi Viet Nga, Chu Thi Xuan, Dang Thi Thanh Le, Nguyen Van Toan*, Chu Manh Hung*, Nguyen Van Duy, Nguyen Van Hieu, Nguyen Duc Hoa, “Enhanced NO2 gas-sensing performance at room temperature using exfoliated MoS2 nanosheets”, Sensors and Actuators A: Physical, Volume 332, (2021) 113137, Q1, [IF2021: 3.407] Truong Tien Hoang Duong, Ho Huu Hau, Chu Manh Hung*, Dang Thi Thanh Le, Nguyen Van Duy, Nguyen Duc Hoa, “Synthesis and investigation of SnO2 nanowires/MoS2 nanosheets heterojunction”, The 11th Vietnam National Conference of Solid Physics and Materials Science, 2021 (Submitted) Truong Tien Hoang Duong, Vuong Tuan Anh, Chu Manh Hung*, Nguyen Van Duy, Nguyen Duc Hoa, “Synthesis and characterization of NiS nanostructures by hydrothermal method”, The 10th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN 2021) (Proceedings) 46 [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] REFERENCES P Zhu, S Li, C Zhao, Y Zhang, J Yu, 3D synergistical rGO/Eu(TPyP)(Pc) hybrid aerogel for high-performance NO2 gas sensor with enhanced immunity to humidity, J Hazard Mater 384 (2020) 121426 https://doi.org/10.1016/j.jhazmat.2019.121426 R.S Downen, Q Dong, E Chorvinsky, B Li, N Tran, J.H Jackson, D.K Pillai, Personal NO2 sensor 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vertically grown on SnO2 nanotubes as highly effective room-temperature NO2 gas sensor, J Hazard Mater 416 (2021) https://doi.org/10.1016/j.jhazmat.2021.125830 59 ...HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Research and synthesis of SnO2 nanowires/ transition metal dichalcogenides heterostructure towards gas sensing applications TRUONG... THESIS TOPIC Research and synthesis of SnO2 nanowires/ transition metal dichalcogenides heterostructure towards gas sensing applications SUPERVISOR Dr Chu Manh Hung SOCIALIST REPUBLIC OF VIETNAM... the title: ? ?Research and fabrication of SnO2 nanowires/ transition metal dichalcogenides heterostructure towards gas sensing applications? ?? Research Objectives The main objectives of this thesis