Public defence in Engineering Physics, M.Sc Peng Liu

Title of the thesis: Gas-phase Synthesis of Semiconducting Single-walled Carbon Nanotubes for Advanced Electronics

Doctoral student: Peng Liu
Opponent: Principal Researcher Don N. Futaba, National Institute of Advanced Science and Technology, Japan
Custos: Professor Esko Kauppinen, Aalto University School of Science, Department of Applied Physics

Gas-phase Synthesis of Semiconducting Single-walled Carbon Nanotubes for Advanced Electronics

Single-walled carbon nanotubes (SWCNTs), a one-dimensional nanomaterial composed of a single layer of carbon atoms, possess unique physical and chemical properties. These attributes enable their application in diverse fields, including electronics, optoelectronics, and sensors. However, unlocking their full potential for high-performance, portable electronics demands high-purity semiconducting SWCNTs (s-SWCNTs) and scalable fabrication techniques.

This thesis addresses these challenges, focusing on two core objectives: achieving a direct, controllable synthesis of high-purity s-SWCNTs and developing scalable methods for fabricating flexible electronic devices based on raw s-SWCNTs. By optimizing the floating catalyst chemical vapor deposition process and key growth parameters, this study achieved a continuous, controllable synthesis of s-SWCNTs with a remarkable purity of 94%, one of the highest purities achieved through direct synthesis methods. The synthesized nanotubes exhibited significantly longer mean lengths than solution-sorted SWCNTs, demonstrating high carrier mobility. Furthermore, the study introduced a lithography- and chemical-free method for fabricating wafer-scale, all-CNT arrays. This dry technique mitigated common issues such as contamination and structural damage associated with wet processing, preserving the intrinsic properties of CNTs. The resulting flexible devices demonstrated excellent uniformity, wearability, environmental stability, and broadband photoresponsivity.

This dissertation has made substantial progress in s-SWCNTs, achieving high-purity synthesis and their integration in flexible devices, laying the groundwork for the development of carbon-based electronics. 

Keywords: Gas-phase synthesis, semiconducting single-walled carbon nanotubes, transistor, wearable electronics, all-carbon nanotube devices; photodetector

Contact information:

Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/ 

Doctoral theses at the School of Science: https://aaltodoc.aalto.fi/handle/123456789/52