Anisotropic Crystallographic Engineering of α-MoO3

Anisotropic Crystallographic Engineering of α-MoO3

ACS Nano

10.1021/acsnano.5c07199

https://doi.org/10.1021/acsnano.5c07199

Qiyao Liu, Zhipeng Li, Xuezhi Ma, Qiushi Liu, Fengxia Wei, Siew Lang Teo, Ruihuan Duan, Adrianzka Mayreswara Dewa Rachmawisista, Yueqian Zhang, Coryl Jing Jun Lee, Jie Deng, Aihong Huang, Ping Luo, Hui Kim Hui, Sherry Lee Koon Yap, Meng Zhao, Rong Ji, Yu Luo, Zheng Liu, Qian Wang

Surface phonon polariton

30 May 2025

Liu, Q., Li, Z., Ma, X., Liu, Q., Wei, F., Teo, S. L., Duan, R., Rachmawisista, A. M. D., Zhang, Y., Lee, C. J. J., Deng, J., Huang, A., Luo, P., Hui, H. K., Yap, S. L. K., Zhao, M., Ji, R., Luo, Y., Liu, Z., & Wang, Q. (2025). Anisotropic Crystallographic Engineering of α-MoO3. ACS Nano, 19(22), 21179–21188. https://doi.org/10.1021/acsnano.5c07199

The α-phase molybdenum trioxide (α-MoO3), a biaxial hyperbolic van der Waals (vdW) crystal, supports highly confined and anisotropic phonon polaritons (PhPs), positioning it as a superior platform for mid-infrared light manipulation. The performance of PhP-based devices critically depends on the properties of α-MoO3 flakes, including their thickness, roughness, and pattern geometry. However, conventional patterning techniques, such as ion beam milling and plasma etching, often introduce doping artifacts and surface damage, resulting in high PhP losses. In this work, we develop a hot-water-based technique for the crystallographic engineering of α-MoO3, leveraging its anisotropic etching properties for surface polishing and nanopatterning. This method exploits the notably higher etching rate along intralayer directions ([100], [001]) compared to the interlayer direction ([010]). Consequently, a 24% enhancement in PhP lifetime was observed in RIE-treated α-MoO3 flakes after hot water polishing, with no measurable change in material thickness. To further validate this technology, we fabricated various two-dimensional PhP manipulation devices using standard nanopatterning and thinning processes, followed by chemical-free hot water anisotropic crystallographic etching. This approach enabled the creation of nanoresonators, lenses, nanocavities, and unidirectional emitters with sharp edges precisely aligned along the crystallographic planes. Our crystallographic engineering approach unlocks precise control of surface waves at the nanoscale, facilitating the development of photonic devices for cutting-edge nanophotonic and nanoscale sensing applications.

Publisher Copyright

This research / project is supported by the Agency for Science, Technology, and Research (A*STAR) - Advanced Manufacturing and Engineering (AME) Individual Research Grant
Grant Reference no. : M22K2c0080, M24N7c0081

This research / project is supported by the Agency for Science, Technology, and Research (A*STAR) - Manufacturing, Trade, and Connectivity programmatic
Grant Reference no. : M23M2b0056

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see 10.1021/acsnano.5c07199

https://oar.a-star.edu.sg/communities-collections/articles/20618

1936-0851
1936-086X

Institute of Materials Research and Engineering