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arXiv · 2305.07793

Control of ternary alloy composition during remote epitaxy on graphene

Zach LaDuca·Katherine Su·Sebastian Manzo·Michael S. Arnold·Jason K. Kawasaki
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Abstract

Understanding the sticking coefficient $σ$, i.e., the probability of an adatom sticking to a surface, is essential for controlling the stoichiometry during epitaxial film growth. However, $σ$ on monolayer graphene-covered surfaces and its impact on remote epitaxy are not understood. Here, using molecular-beam epitaxial (MBE) growth of the magnetic shape memory alloy Ni$_2$MnGa, we show that the sticking coefficients for metals on graphene-covered MgO (001) are less than one and are temperature and element dependent, as revealed by ion backscattering spectrometry (IBS) and energy dispersive x-ray spectroscopy (EDS). This lies in stark contrast with most transition metals sticking on semiconductor and oxide substrates, for which $σ$ is near unity at typical growth temperatures ($T<800\degree$C). By initiating growth below $400 \degree$ C, where the sticking coefficients are closer to unity and wetting on the graphene surface is improved, we demonstrate epitaxy of Ni$_2$MnGa films with controlled stoichiometry that can be exfoliated to produce freestanding membranes. Straining these membranes tunes the magnetic coercive field. Our results provide a route to synthesize membranes with complex stoichiometries whose properties can be manipulated via strain.

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Zach LaDuca, Katherine Su, Sebastian Manzo, Michael S. Arnold, Jason K. Kawasaki. 2023-05-12. Control of ternary alloy composition during remote epitaxy on graphene. https://doi.org/10.1103/physrevmaterials.7.083401

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