Atomistic understanding of two-dimensional monatomic phase-change material for non-volatile optical applications
Abstract
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.
Authors 10
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Affiliation as printed
Center for Alloy Innovation and Design (CAID) , State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an , China
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Affiliation as printed
Center for Alloy Innovation and Design (CAID) , State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an , China
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Affiliation as printed
Center for Alloy Innovation and Design (CAID) , State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an , China
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Affiliation as printed
Center for Alloy Innovation and Design (CAID) , State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an , China
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Affiliation as printed
Center for Alloy Innovation and Design (CAID) , State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an , China
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Affiliation as printed
Center for Alloy Innovation and Design (CAID) , State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an , China
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Affiliation as printed
Center for Alloy Innovation and Design (CAID) , State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an , China
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Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University
Affiliation as printed
Institute of Physics IA , JARA-FIT , RWTH Aachen University , 52074 Aachen , Germany
Peter Grünberg Institute (PGI 10) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany
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Affiliation as printed
Department of Physics , Sapienza University of Rome , Rome 00185 , Italy
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Affiliation as printed
Center for Alloy Innovation and Design (CAID) , State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an , China
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