How transparent is graphene? A surface science perspective on remote epitaxy

TL;DR

The paper addresses whether graphene truly transmits the substrate lattice potential to enable remote epitaxy or if observed epitaxial phenomena arise from alternative mechanisms. It argues that the remote potential is generally weak and modulated by graphene screening, substrate bonding, and graphene-induced reconstructions, with a bias-free Fourier/beating framework proposed to disentangle graphene, substrate, and reconstruction contributions. While some long-range epitaxial relationships (e.g., rotated GdPtSb on graphene/sapphire) hint at genuine remote effects, the authors contend that most experimental observations can be explained by pinhole or vdW epitaxy, or by graphene-mediated reconstructions, rather than a dominant remote potential. The outlook emphasizes direct remote-potential measurements, explicit pairwise interactions, and systematic kinetic studies to clarify the balance between remote epitaxy and competing mechanisms, with significant implications for heterogeneous integration and film templating at graphene interfaces.

Abstract

Remote epitaxy is the synthesis of a single crystalline film on a graphene-covered substrate, where the film adopts epitaxial registry to the substrate as if the graphene is transparent. Despite many exciting applications for flexible electronics, strain engineering, and heterogeneous integration, an understanding of the fundamental synthesis mechanisms remains elusive. Here we offer a perspective on the synthesis mechanisms, focusing on the foundational assumption of graphene transparency. We identify challenges for quantifying the strength of the remote substrate potential that permeates through graphene, and propose Fourier and beating analysis as a bias-free method for decomposing the lattice potential contributions from the substrate, from graphene, and from surface reconstructions, each at different frequencies. We highlight the importance of graphene-induced reconstructions on epitaxial templating, drawing comparison to moiré epitaxy. We highlight the role of the remote potential in tuning surface diffusion and adatom kinetics on graphene, which are crucial for navigating the competition between remote epitaxy and defect-seeded mechanisms like pinhole epitaxy. In light of this weak remote potential, we re-evaluate the current state-of-the-art experimental evidence, highlighting why it remains challenging to experimentally validate a ``remote'' epitaxy mechanism that cannot be explained by alternatives, such as pinhole-seeded epitaxy or serial van der Waals epitaxy. We end with one experimental example that, to out knowledge, cannot be explained by competing mechanisms: a different long-range epitaxial relationship for GdPtSb films grown on graphene/sapphire, compared to direct epitaxy on sapphire. We suggest for future experiments that directly measure the remote potential and impact of tunable growth kinetics.

Figures (8)

• Figure 1: Challenges for interpreting electrostatic potential maps of graphene/substrate heterostructures. (a,b) Crystal structures of graphene/Si (001) and graphene/GaN (0001), with fixed in-plane positions and allowed out-of-plane relaxation. (c,d) Electrostatic potential maps. The potential fluctuations of the graphene itself have been subtracted away. Atom position labels 1, 2, 3 and crystallographic axes are added for clarity. Note that (d) is sheared from the hexagonal symmetry of GaN (0001). (e,f) Line cuts of the electrostatic potentials. (g) Summary of extracted $\Delta \varphi$ for different graphene covered substrates. (h) Periodic profiles of the selected regions from (e) and (f). For graphene/Si it is the region $x=0$ to $x=0.5$ in (e). For graphene/GaN it is the region $x\approx 0.8$ to $x\approx 0.1$ (atom 3 to atom 1) in (d). Adapted from Kong et. al., "Polarity governs atomic interaction through two-dimensional materials," Nature Materials 17, 999–1004 (2018) Springer Nature kong2018polarity. Reproduced with permission from Springer Nature.
• Figure 2: Electrostatic potential calculations highlighting the interference from the graphene and substrate potentials. Lattice vectors are added for clarity. Adapted from Dai et. al. "Highly heterogeneous epitaxy of flexoelectric BaTiO$_{3-\delta}$ membrane on Ge," Nature Commun., 13, 2990 (2022), Springer Nature dai2022highly, under Creative Commons CC BY license.
• Figure 3: Screened Morse model for the remote potential above graphene/GaAs (001). Blue curve is the potential through an insulating hBN spacer, in which there is no screening. Red curves are the screened potential through graphene for different graphene carrier densities. Dotted black curve is the Lennard-Jones potential of graphene. Solid black curve is the Morse potential for a bare GaAs substrate. Adapted from Kawasaki and Campbell, "An analytical model for the remote epitaxial potential," arXiv:2507.09913 (2025) kawasaki2025model.
• Figure 4: Graphene induced surface reconstructions. (a-d) Schematic lattice potential $\varphi(x)$ above crystalline surfaces and their Fourier transform $\hat{\varphi}(Q)$. (e) STM image of the $(6\sqrt 3 \times6\sqrt 3)$$R30\degree$ reconstruction of buffer-layer graphene/SiC(0001) beneath the first epitaxial layer of graphene, inset shows the lattice of epitaxial graphene. Adapted from Poon et. al. Phys. Chem. Chem. Phys., 12, 13522-13533 (2010) CoGrSiC_Sticking with permission from the Royal Society of Chemistry. (f) STM image of the "$6\times2$" reconstruction of graphene/Ge(110). From Campbell et. al. Phys. Rev. Materials 2, 044004 (2018) cambell2018_GrGe6x2 with permission from the American Physical Society. (g) STM image of the graphene/Ir (111) with $(10 \times 10)_{gr} / (9 \times 9)_{Ir}$ moiré structure. The x marks the HCP site that is favored for nucleation. From N'Diaye et. al. Phys. Rev. Lett. 97, 215501 (2006) NDiaya2006_IrGrIr with permission from the American Physical Society. (h,i,j) Cross-sectional structural models of graphene on SiC(0001), Ge(110), and Ir(111). Graphene/Ge model from Rogge et. al. MRS Commun. 5, 539–546 (2015) Rogge2015_Ge110_6x2_Model under Creative Commons Attribution 4.0 International License. Graphene/Ir adapted from Hämäläinen et. al. Phys. Rev. B 88, 201406(R) (2013) Hamalainen2013_RrIr_Moire_Image with permission from the American Physical Society.
• Figure 5: Impact of graphene moiré and reconstructions on nucleation and epitaxy. (a,b) Models for adatom sticking and ordering on graphene/SiC and graphene/Ir. (c) STM image of preferred Co sticking on buffer graphene vs. epitaxial graphene on SiC(0001). Adapted from Poon et. al. Phys. Chem. Chem. Phys., 12, 13522-13533 (2010) CoGrSiC_Sticking with permission from the Royal Society of Chemistry. (d) Ordered superlattice of Ir clusters that follows the moiré peridicity of graphene/Ir(111). Adapted from N'Diaye et. al. Phys. Rev. Lett. 97, 215501 (2006) NDiaya2006_IrGrIr with permission from the American Physical Society.