Advanced characterization of carbon nanotube arrays for next generation nanoelectronics

Aligned semiconducting carbon nanotubes (CNTs) are promising channel material candidates for industrial scale next-generation field-effect transistors (FETs) due to their exceptional electrical and thermal properties [1-3]. In order to select purely semiconducting CNTs required for FETs and further assemble them into aligned arrays on the substrate of interest, CNT wrapping by conjugated polymers within the CNT dispersion is a widely used approach [1-4]. Residual wrapping polymers remaining with the CNTs after their aligned deposition are expected to adversely affect FET performance and need to be removed without damaging CNTs [5].Understanding and optimizing fabrication processes to remove such residues without compromising structural integrity and pristine electronic properties of CNTs are crucial.​ A range of cleaning methods will be applied, including downstream plasma techniques, solvent-based treatment and annealing [5-7]. Characterization methods to accurately extract chemical information with high spatial resolution are highly desirable, and it is essential that they are compatible with FAB processes. The combination of Atomic Force Microscopy-Infrared Spectroscopy (AFM-IR) and Quantitative Nanomechanical Mapping microscopy have been identified as the most promising approach to qualify efficacy of the cleaning treatments. Here, the former method can detect and map chemical residues at the nanoscale through local IR absorption and the latter can assess both changes in the defectivity-induced mechanical properties of CNTs and polymer-induced surface adhesion. By leveraging advanced scanning probe microscopy (SPM) techniques and other complementary techniques, the research aims to provide insights into the interactions between various process treatments and CNT materials and to develop characterization strategy to assess efficacy of various chemical (wet- and dry-) treatments on the removal of polymer residues.

For this research, the student will be trained in advanced SPM techniques including AFM-IR and peak-force AFM. The student will gain hands-on experience with state-of-the-art AFM technique and data analysis, build understanding of nanoscale chemical phenomena, and develop skills relevant to both academic research and industrial semiconductor R&D. For deeper understanding of the results, complimentary material characterization analysis such as Raman/Photoluminescence including tip-enhanced Raman spectroscopy, Transmission electron microscopy (TEM) and X-ray photoelectron microscopy (XPS) analysis can be availed through collaborations. With the guidance of his supervisors, data interpretation and analysis will also be a major part of this thesis/internship. As such, the student will be guided in the design of the experiment and understanding the resulting experimental data. A good command of English is necessary. The project duration is 6 months, with the possibility of extension if further exploration is warranted.

​Required background: Physics, Chemistry, Material science, Nanotechnology

Type of work: 60% experimental, 40% data analysis and theory

Focus of work: Materials; Semiconductor Physics; Chemistry; Metrology & characterization

References

[1] Liu et al, Science 368, 850 (2020)

[2] Jinkins et al, Sci. Adv. 7 (2021)

[3] Lin et al, Nat. Electron, 6 (2023)

[4] Srimani et al, Adv. Electron. Mater. 8, 2101377 (2022)

[5] Brady et al, Science Adv. 2, 9 (2016)

[6] Marinov et al, npj 2D Mater. Appl. 5, 17 (2021)

[7] Wyndaele et al, npj 2D Mater. Appl., 8, 25 (2024)