Public defence in Engineering Physics, M.Sc. Zhenyu Xu

Title of the thesis: Public defence from the Aalto University School of Science, Department of Applied Physics. 

Thesis defender: Zhenyu Xu 
Opponent: PhD Shunsuke Sakurai, National Institute of Advanced Industrial Science and Technology (AIST), Japan
Custos: Prof. Esko Kauppinen, Aalto University School of Science

This doctoral research focuses on double-walled carbon nanotubes (DWCNTs), which exhibit exceptional electrical, thermal, and mechanical properties, making them highly suitable for use in advanced technologies such as flexible electronics, sensors, and optoelectronic devices.

The aim of this study was twofold: to improve the synthesis of high-quality DWCNTs using floating catalyst chemical vapor deposition (FC-CVD), and to develop a novel technique for directly patterning DWCNTs for integration into devices. The work also explored the application of these DWCNTs in functional electronic components.

One of the key findings is the role of sulfur in the growth process. This study revealed how sulfur effect the growth of high-purity DWCNTs. By optimizing sulfur concentration, up to 87% DWCNT content were achieved. This led to a better understanding of how to control the structural quality and electrical properties of the resulting CNTs.

In addition, The research developed a new dry patterning technique that allows DWCNTs to be directly transferred to various surfaces without the need for damaging or contaminating post-processing. This method enables the fabrication of clean, high-resolution nanotube patterns suitable for use in electronic devices.

The research provides new insights into the mechanisms of DWCNT growth and introduces scalable methods for their integration into real-world applications. These results contribute to the broader field of nanomaterials and support the development of next-generation electronic systems.

Key words: FC-CVD, double-walled carbon nanotube, patterning electrode, sulfur, gas-phase synthesis

Thesis available for public display 10 days prior to the defence at Aaltodoc.