Bottom-up Synthesis of Metastable 2D Hexagonal Copper(I) Iodide on Monolayer and within Bilayer Graphene
Abstract
Copper(I) iodide (CuI) is a wide-bandgap semiconductor crystallizing in the 3D γ-phase under ambient conditions; its layered van der Waals bulk phase β-CuI is stable only between 643 and 673 K. The two-dimensional (2D) h-CuI form has been obtained via liquid-phase exfoliation of mechanochemically prepared precursors and via encapsulation between graphene sheets, whereas bottom-up growth of 2D h-CuI on open surfaces has not yet been demonstrated. Here, we report a vapor-phase synthesis of h-CuI directly on low-defect, large-area monolayer and within bilayer reduced oxo-graphene (r-oxo-G) at low temperatures. Using a copper TEM grid as the solid-state precursor for copper, HI-vapor exposure at 40 °C initiates nucleation, while annealing at 180 °C promotes the growth of extended h-CuI domains. Aberration-corrected HRTEM resolves the atomic structure, local twist angles, and lattice anisotropy of the CuI/r-oxo-G nanohybrid, while STEM-EDX yields a Cu:I ratio consistent with 1:1. First-principles calculations show that van der Waals adhesion to graphene stabilizes the supported hexagonal layer. Under the presented low-temperature precursor conditions, pathways for nucleation of the γ-phase are not available, allowing the hexagonal phase to form selectively at the graphene interface. Ab initio molecular dynamics simulations show that the heterostructure retains its hexagonal lattice order at 600 K, including on an open monolayer graphene support. The lateral extent of the growth is limited mainly by remaining interfacial adsorbates. These results establish a route to metastable 2D h-CuI on a chemically inert graphene template, which may be useful for wide-bandgap electronic and optoelectronic devices.
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BibTeX
@misc{kaiser2026bottomup,
title = {{Bottom-up Synthesis of Metastable 2D Hexagonal Copper(I) Iodide on Monolayer and within Bilayer Graphene}},
author = {David Kaiser and Guobin Jia and Janis Köster and Sadegh Ghaderzadeh and Christian E. Halbig and Siegfried Eigler and Andrey Turchanin and Benjamin Dietzek-Ivanšić and Arkady V. Krasheninnikov and Jonathan Plentz and Elena Besley and Ute Kaiser},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.11459},
eprint = {2609.11459},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.11459},
}
RIS
TY - UNPB
TI - Bottom-up Synthesis of Metastable 2D Hexagonal Copper(I) Iodide on Monolayer and within Bilayer Graphene
AU - David Kaiser
AU - Guobin Jia
AU - Janis Köster
AU - Sadegh Ghaderzadeh
AU - Christian E. Halbig
AU - Siegfried Eigler
AU - Andrey Turchanin
AU - Benjamin Dietzek-Ivanšić
AU - Arkady V. Krasheninnikov
AU - Jonathan Plentz
AU - Elena Besley
AU - Ute Kaiser
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.11459
UR - https://arxiv.org/abs/2609.11459
AB - Copper(I) iodide (CuI) is a wide-bandgap semiconductor crystallizing in the 3D γ-phase under ambient conditions; its layered van der Waals bulk phase β-CuI is stable only between 643 and 673 K. The two-dimensional (2D) h-CuI form has been obtained via liquid-phase exfoliation of mechanochemically prepared precursors and via encapsulation between graphene sheets, whereas bottom-up growth of 2D h-CuI on open surfaces has not yet been demonstrated. Here, we report a vapor-phase synthesis of h-CuI directly on low-defect, large-area monolayer and within bilayer reduced oxo-graphene (r-oxo-G) at low temperatures. Using a copper TEM grid as the solid-state precursor for copper, HI-vapor exposure at 40 °C initiates nucleation, while annealing at 180 °C promotes the growth of extended h-CuI domains. Aberration-corrected HRTEM resolves the atomic structure, local twist angles, and lattice anisotropy of the CuI/r-oxo-G nanohybrid, while STEM-EDX yields a Cu:I ratio consistent with 1:1. First-principles calculations show that van der Waals adhesion to graphene stabilizes the supported hexagonal layer. Under the presented low-temperature precursor conditions, pathways for nucleation of the γ-phase are not available, allowing the hexagonal phase to form selectively at the graphene interface. Ab initio molecular dynamics simulations show that the heterostructure retains its hexagonal lattice order at 600 K, including on an open monolayer graphene support. The lateral extent of the growth is limited mainly by remaining interfacial adsorbates. These results establish a route to metastable 2D h-CuI on a chemically inert graphene template, which may be useful for wide-bandgap electronic and optoelectronic devices.
ER -