Control of ternary alloy composition during remote epitaxy on graphene
- Univ. of Wisconsin, Madison, WI (United States); University of Wisconsin-Madison
- Univ. of Wisconsin, Madison, WI (United States)
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 growth of the magnetic shape memory alloy Ni2 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 and energy-dispersive x-ray spectroscopy. 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°C). By initiating growth below 400°C, where the sticking coefficients are closer to unity and wetting on the graphene surface is improved, we demonstrate the epitaxy of Ni2 MnGa films with controlled stoichiometry that can be exfoliated to produce freestanding membranes. Straining these membranes tunes the magnetic coercive field. Finally, our results provide a route to synthesize membranes with complex stoichiometries whose properties can be manipulated via strain.
- Research Organization:
- Univ. of Wisconsin, Madison, WI (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); US Air Force Office of Scientific Research (AFOSR); USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0016007
- OSTI ID:
- 2339632
- Journal Information:
- Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 8 Vol. 7; ISSN 2475-9953
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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