Study on the Mechanism and Process of Femtosecond Laser Induced Interconnection of Carbon Nanotubes

Abstract

Over the past two decades, breakthrough advances have been made in Carbon Nanotubes (CNTs) electronics involving various aspects of material optimization, nanoscale devices, and integrated circuits. The compatibility of solution-based CNTs random networks with high-throughput printing processes has led to the application of CNTs stochastic networks in large-scale, large-area flexible and stretchable electronics. However, there are a large number of CNT-CNT junctions formed by overlapping CNTs in the randomly distributed CNTs networks, which results in the need for carriers to tunnel through multiple CNTs junctions during transports and, thus, seriously hinders the research on the properties and applications of CNTs random networks. Therefore, in order to solve this technical problem, a femtosecond pulsed laser irradiation technique was proposed to irradiate CNT based on the solution method to prepare a random network of CNTs, so as to achieve the controllable manufacturing of CNTs interconnect wires or interconnect films of different scales and functions. The mechanism of laser induced covalent interconnection of CNTs and femtosecond pulsed laser induced Single-walled Carbon Nanotubes (SWCNTs) were studied by combining molecular dynamics (MD) simulation and experimental studies. A series of theoretical and experimental results have been obtained in the process of covalent interconnection of SWCNTs and Multi-walled Carbon Nanotubes (MWCNTs) for in the manufacture and application of CNTs functional network thin films.

In terms of theoretical research on femtosecond pulse laser-induced covalent interconnection of CNTs, a full atomic MD model was established to simulate the effects of laser parameters such as laser energy, pulse width, irradiation region, and chirality and orientation of CNTs on the bonding behaviour of CNTs. The optimal laser parameters for inducing covalent interconnection of CNTs were optimized by maximizing the axial mechanical strength of the connected CNTs, and a defect free covalent interconnection junction was obtained. On this basis, the evolution mechanism of carbon atom slip, exfoliation and recombination on the wall of CNTs under different laser parameters was studied, revealing the microscopic mechanism of covalent interconnection induced by femtosecond pulse laser.

In the process research of femtosecond pulse laser-induced covalent interconnection of CNTs, combined with MD simulation optimization of femtosecond pulse laser irradiation parameters, the effects of femtosecond pulse laser irradiation mode, scanning speed, power, etc. on the morphology, structural defects, atomic network structure, etc. of SWCNTs and MWCNTs were studied based on solution prepared SWCNTs and MWCNTs random networks. It was confirmed that appropriate laser parameter combinations can achieve different scales of MWCNTs SWCNTs, SWCNTs, and SWCNTs bundles The mechanism of CNTs interconnection controlled by femtosecond pulse laser was revealed from MD simulation and experimental perspective, and the correctness of theoretical simulation models and results was verified. At the same time, the mechanism of action of femtosecond pulsed laser and electron beam on SWCNTs was compared and analyzed from the changes in pipe wall structure of CNTs through in-situ observation in TEM, confirming the superiority of femtosecond pulse laser interconnection technology.

In terms of controllable manufacturing of functional network films, the random network of CNTs was transferred to different substrates by means of spin coating, drop coating and dispensing, and then SWCNTs and MWCNTs interconnected films with excellent performance were constructed based on the technique of covalent interconnection induced by femtosecond pulse, resulting in the formation of different high-performance devices, such as planar conducting electrodes, field-effect tubes, resistive bending and strain sensors. These devices exhibit excellent electrical performance and stable output response signals after being connected to the CNT networks, which also verifies the effectiveness, repeatability and stability of random network connection of SWCNT/MWCNT thin films induced by femtosecond pulse laser. The proposed optimal combination of femtosecond pulse laser irradiation parameters provides technical support for the actual manufacturing and application of CNT functional network thin films in flexible electronic devices.

This article conducts research on the mechanism and process of femtosecond pulse laser-induced covalent interconnection of CNTs and deeply reveals the micro mechanism of controllable interconnection of CNTs induced by femtosecond pulse laser from the perspectives of MD simulations and experimentations. A stable manufacturing process is formed for connecting random networks of SWCNT/MWCNT of different scales using the laser irradiation, providing a scientific basis and basic technical support for the manufacturing process of subsequent new carbon based devices.

Date of Award	20 Feb 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Jianlei Cui (External Supervisor), Xiaoqiao HE (Supervisor) & Wenjun Wang (External Supervisor)