2025/12/11 by Hanyi Zhang, Xueqi Xing, Zhang, Hanyi +18
Materials Science · #2D Materials and Applications #Amorphous solid #Antimony #Chemical and Physical Properties of Materials #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Molar absorptivity #Nanophotonics #Phase (matter) #Phase-change materials and chalcogenides #Photonics #Scaling #Spectroscopy #Thin film
paper · pdf · doi:10.48550/arxiv.2512.10469
published in arXiv (Cornell University) (Cornell University)
openalex publication_date 2025/12/11 · openalex created_date 2025/12/13 · openalex updated_date 2026/08/01
Elemental antimony (Sb) is a promising material for phase-change memory, neuromorphic computing and nanophotonic applications, because its compositional simplicity can prevent phase segregation upon extensive programming. Scaling down the film thickness is a necessary step to prolong the lifetime of amorphous Sb, but the optical properties of Sb are also significantly altered as the thickness is reduced to a few nanometers, adding complexity to device optimization. In this work, we aim to provide atomistic understanding of the thickness-dependent optical responses in Sb thin films. As thickness decreases, both the extinction coefficient and optical contrast reduce in the near-infrared spectrum, consistent with previous optical measurements. Such thickness dependence gives rise to a bottom thickness limit of 2 nm in photonic applications, as predicted by coarse-grained device simulations. Further bonding analysis reveals a fundamentally different behavior for amorphous and crystalline Sb upon downscaling, resulting in the reduction of optical contrast. Thin film experiments are also carried out to validate our predictions. The thickness-dependent optical trend is fully demonstrated by our ellipsometric spectroscopy experiments, and the bottom thickness limit of 2 nm is confirmed by structural characterization experiments. Finally, we show that the greatly improved amorphous-phase stability of the 2 nm Sb thin film enables robust and reversible optical switching in a silicon-based waveguide device.