Novel synthesis technologies for two-dimensional transition metal dichalcogenides and their heterostructures

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2022-12-02
Degree programme
130 + app. 44
Aalto University publication series DOCTORAL THESES, 165/2022
Two-dimensional (2D) materials, especially 2D transition metal dichalcogenides (TMDs), have been recently expected to play important roles in future applications due to their atomic-thickness nanostructure and various physical properties. Chemical vapour deposition (CVD) is considered to be the most promising synthesis method for two-dimensional materials, due to the best balance between yield and quality of the products. Hence, this thesis focuses on two novel CVD methods for synthesising TMDs and their heterostructures. The first one is molten salt-assisted chemical vapour deposition (Salt 2.0). By applying the Salt 2.0 technique, an abnormal anti-pyramid stacked MoS2/WS2 heterostructure and a MoS2/double-wall carbon nanotube mix-dimensional heterostructure with negative photoresponse are synthesised respectively. These heterostructures can provide new approaches for engineering two-dimensional nanoelectronic devices.Another technique is gas-phase chemical vapour deposition (GCVD). Different from other synthesis methods, the GCVD technique can continuously produce clean and large-mass TMD nanoflakes in aerosols which can be simply collected by a filter for device fabrication and integration at room temperature. A demonstration is achieved for producing MoS2 nanoflakes in the gas phase with an output of up to 24 μg.min-1. The MoS2 nanoflakes have comparable sizes and qualities to the ones from current methods, promising their potential to replace the current MoS2 materials in many applications. In addition, the synthesis without substrate provides a better understanding of the nucleation and growth mechanism in the synthesis of TMDs. The extension of an available novel method and the development of a completely new method provide new approaches for the synthesis of TMDs and other 2D materials.
Supervising professor
Sun, Zhipei, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland
chemical vapour deposition, transition metal dichalcogenide, salt-assisted chemical vapour deposition, gas-phase chemical vapour deposition
Other note
  • [Publication 1]: Xueyin Bai, Shisheng Li, Susobhan Das, Luojun Du, Yunun Dai, Lide Yao, Ramesh Raju, Mingde Du, Harri Lipsanen and Zhipei Sun. Singlestep chemical vapour deposition of anti-pyramid MoS2/WS2 vertical heterostructures. Nanoscale, 13, 8, 4537-4542, 2021.
    Full text in Acris/Aaltodoc:
    DOI: 10.1039/d0nr08281c View at publisher
  • [Publication 2]: Xueyin Bai, Zhenyu Xu, Qiang Zhang, Shisheng Li, Yunyun Dai, Xiaoqi Cui, Hoon Hahn Yoon, Lide Yao, Hua Jiang, Mingde Du, Yi Zhang, Esko I. Kauppinen and Zhipei Sun. Molybdenum disulfide/double-Wall carbon nanotube mixed-dimensional heterostructures. Advanced MaterialsInterfaces, 9, 13, 202200193, 2022.
    Full text in Acris/Aaltodoc:
    DOI: 10.1002/admi.202200193 View at publisher
  • [Publication 3]: Xueyin Bai, Qiang Zhang, Xiaoqi Cui, Zhenyu Xu, Jiancheng Zheng, Mingde Du, Hoon Hahn Yoon, Shisheng Li, Juan Arias Muñoz, Yi Zhang, Hua Jiang, Jouko Lahtinen, Esko I. Kauppinen and Zhipei Sun. Continuous production of high-quality few-layer MoS2 nanoflakes via gasphasechemical vapour deposition. Submitted to Nature Synthesis, 13 pages, 2022
  • [Publication 4]: Yi Zhang, Xueyin Bai, Juan Camilo Arias Muñoz, Yunyun Dai, Susobhan Das, Yadong Wang and Zhipei Sun. Coherent modulation of chiral nonlinear optics with crystal symmetry. Light: Science & Applications, 11, 216, 2022.
    Full text in Acris/Aaltodoc:
    DOI: 10.1038/s41377-022-00915-4 View at publisher