Controlling the balance between remote, pinhole, and van der Waals epitaxy of Heusler films on graphene/sapphire

Abstract

Remote epitaxy on monolayer graphene is promising for synthesis of highly lattice mismatched materials, exfoliation of free-standing membranes, and re-use of expensive substrates. However, clear experimental evidence of a remote mechanism remains elusive. In many cases, due to contaminants at the transferred graphene/substrate interface, alternative mechanisms such as pinhole-seeded lateral epitaxy or van der Waals epitaxy can explain the resulting exfoliatable single-crystalline films. Here, we find that growth of the Heusler compound GdPtSb on clean graphene on sapphire substrates produces a 30 degree rotated epitaxial superstructure that cannot be explained by pinhole or van der Waals epitaxy. With decreasing growth temperature the volume fraction of this 30 degree domain increases compared to the direct epitaxial 0 degree domain, which we attribute to slower surface diffusion at low temperature that favors remote epitaxy, compared to faster surface diffusion at high temperature that favors pinhole epitaxy. We further show that careful graphene/substrate annealing ($T\sim 700^{\circ }C$) and consideration of the film/substrate vs film/graphene lattice mismatch are required to obtain epitaxy to the underlying substrate for a variety of other Heusler films, including LaPtSb and GdAuGe. The 30 degree rotated superstructure provides a possible experimental fingerprint of remote epitaxy since it is inconsistent with the leading alternative mechanisms.

References in corpus (4)

• Heusler 4.0: Tunable Materials
• Pinhole-seeded lateral epitaxy and exfoliation of GaSb films on graphene-terminated surfaces
• High electrical conductivity in the epitaxial polar metals LaAuGe and LaPtSb
• Selective area epitaxy of GaAs films using patterned graphene on Ge

Cited by in corpus (6)

• Perspective: strain and strain gradient engineering in membranes of quantum materials
• Metamagnetism and anomalous magnetotransport properties in rare-earth-based polar semimetals $R$AuGe ($R=$ Dy, Ho, and Gd)
• Cold Seeded Epitaxy and Flexomagnetism in Smooth GdAuGe Membranes Exfoliated from graphene/Ge(111)
• Control of ternary alloy composition during remote epitaxy on graphene
• How transparent is graphene? A surface science perspective on remote epitaxy
• Electronic Structure of Kramers Nodal-Line Semimetal YAuGe and Anomalous Hall Effect Induced by Magnetic Rare-Earth Substitution