PhD - Leuven | More than two weeks ago
High aspect ratio (HAR) nanostructures are fundamental building blocks for many applications, such as microelectronic devices, energy storage, photovoltaics as well as biomimetic antifouling and antibacterial materials. Due to high surface-to-volume ratios and nano-confinement effects, nanostructures often possess unique properties that are different from their bulk counterparts, which makes them of particular interest for many applications.
In the past few years, we have explored three main applications, i.e. superhydrophobic surfaces1–4, biomimetic antibacterial surfaces5–8, and elastocapillary self-assembly (a.k.a. pattern collapse)9. For all these applications, advanced characterization techniques play an essential role and open new opportunities to probe nanoscale phenomena. With a novel application of optical reflectance spectroscopy1 and ATR-FTIR3,4, the wetting states and wetting dynamics on nanostructured surfaces have been directly probed, for the first time, at a nanoscale level. Utilizing environmental transmission electron microscopy, mechanisms of nanoscale silicon etching10 and capillary-induced self-assembly of nanostructures9 have been revealed with unprecedented details.
Advanced characterization techniques, whether it’s based on in situ visualizations or an indirect coupling of various physical properties, can greatly facilitate our understanding of the nanoscale mechanisms and allow many industrial and everyday processes to be understood and controlled at the fundamental level. In this project, we will continue to explore different techniques including ATR-FTIR, scatterometry and nanoindentation to characterize wetting and mechanical property of nanostructures. Such a fundamental study has important applications in advanced patterning process for the N3 and beyond technology nodes, such as gap fill by flowable CVD, nanoscale wet etching and cleaning in confined space, pattern collapse of high aspect ratio EUV resist or new device architectures like finFET or gate-all-around transistors. This Ph.D. topic aims at providing a fundamental understanding on the wetting and mechanical deformation mechanisms of nanostructures. The gained insights could also be translated into novel designs of antibacterial functional materials, where bacterial cells can be killed by a mechanical stress inserted by nanostructures5–7.
The successful candidate should have a solid background in physics and engineering, with strong problem-solving skills and good writing and oral communication skills.
Type of work: literature 10 %, 50% experiments and 40 % analysis and modeling.
Contact: XiuMei Xu (firstname.lastname@example.org)
1. Xu, X. et al. Capturing wetting states in nanopatterned silicon. ACS Nano 8, 885–893 (2014).
2. Li, S. et al. High-frequency acoustic for nanostructure wetting characterization. Langmuir 30, 7601–8 (2014).
3. Vrancken, N. et al. Superhydrophobic Breakdown of Nanostructured Surfaces Characterized in Situ Using ATR-FTIR. Langmuir 33, 3601–3609 (2017).
4. Vrancken, N. et al. In-situ ATR-FTIR for dynamic analysis of superhydrophobic breakdown on nanostructured silicon surfaces. Sci. Rep. 8, (2018).
5. Ivanova, E. P. et al. The multi-faceted mechano-bactericidal mechanism of nanostructured surfaces. Proc. Natl. Acad. Sci. U. S. A. 117, 12598–12605 (2020).
6. Nguyen, D. H. K. et al.The idiosyncratic self-cleaning cycle of bacteria on regularly arrayed mechano-bactericidal nanostructures. Nanoscale 11, 16455–16462 (2019).
7. Zahir et al. Model-Driven Controlled Alteration of Nanopillar Cap Architecture Reveals its Effects on Bactericidal Activity. Microorganisms 8, 186 (2020).
8. Elbourne, A. et al. Imaging the air-water interface: characterising biomimetic and natural hydrophobic surfaces using in situ atomic force microscopy. J. Colloid Interface Sci. 536, 363–371 (2019).
9. Vrancken, N. et al. Nanoscale Elastocapillary Effect Induced by Thin-Liquid-Film Instability. J. Phys. Chem. Lett. 11, 2751–2758 (2020).
10. Aabdin, Z. et al. Transient Clustering of Reaction Intermediates During Wet Etching of Silicon Nanostructures. Nano Lett. 17, 2953–2958 (2017).
Required background: Engineering Science
Type of work: 10% literature, 50% experiments and 40 % analysis and modeling.
Supervisor: Stefan De Gendt
Co-supervisor: XiuMei Xu
Daily advisor: XiuMei Xu
The reference code for this position is 2021-068. Mention this reference code on your application form.