Twisted van der Waals (vdW) heterostruc-
tures have drawn growing interest in recent
years.1–7 The twist angle creates a moiré pat-
tern at a larger length scale than the periodicity
in each independent layer, leading to spatially-
dependent interactions between the layers. As
such, the twist angle has been used as a con-
tinuous knob to effectively tune the Hamilto-
nian of the system and realize novel electronic
phases.8,9 At small twist angles, large domains
of lowest energy stacking configurations sepa-
rated by sharp domain walls form through the
atomic relaxation process,10–14 resulting in mul-
tiple different stacking orders coexisting within
the multilayer.
Recently, several works have explored how the
twist angle and the consequent changes to the
global electronic structure of the material, such
as the emergence of flat bands or modified den-
sity of states, affect the surface chemistry and
catalytic properties of moiré systems.15–18 Ad-
ditionally, preferential adsorption of chemical
species due to corrugation and strain effects
on the moiré surface has also been observed.19
In general, strain has been utilized as a means
of manipulating the moiré patterns in twisted
vdW heterostructures.20–22 However, until now,
no investigation has focused on the local stack-
ing order as a platform for controlling the sur-
face chemistry of this class of materials.
Here, we demonstrate domain-dependent sur-
face adhesion as a new avenue to observe and
manipulate the surface chemistry of moiré sys-
tems, a phenomenon we call moiré-assisted
chemistry. We first show selective adhesion
of metallic film on the rhombohedral domain
of twisted double bilayer graphene (tDBG)
while avoiding the Bernal domain. We then
explore the robustness of this observation in
twisted double trilayer graphene (tDTG) un-
der varying ambient conditions and through
domain-dependent adhesion of another mate-
rial, namely, water droplets. Finally, we demon-
strate how the particles that selectively adhere
to the surface can be used to reshape the under-
lying moiré lattice. Overall, our results estab-
lish a basis for the development of capabilities
in moiré engineering via domain-dependent sur-
face interactions.
In tDBG, the relaxed moiré superlattice is
composed of two triangular stacking order do-
mains: the lowest energy Bernal configuration
(ABAB) and the metastable rhombohedral con-
figuration (ABCA).11,23 Due to the small but fi-
nite energy difference between the Bernal phase
and the rhombohedral phase, the rhombohe-
dral domain walls exhibit a finite inward curva-
ture.11 This characteristic curving allows us to
unambiguously identify the rhombohedral do-
mains with scanning probe microscopy tech-
niques (see Supporting Note A). Fig. 1a shows
a mid-IR scanning nearfield optical microscopy
(mIR-SNOM) map measured on a tDBG sam-
ple with a 0.3-degree twist angle. The rhombo-
hedral and Bernal stacking domains are iden-
tified by the light and dark contrast respec-
tively (see Fig. 1a insets); simultaneous to-
pography imaging (lower left inset of Fig. 1a)
shows that the sample is featureless on the sur-
face. We deposit Field’s metal onto this sur-
face using a mechanical ablation technique (see
Supporting Note A). This process breaks the
molten metal and scatters its nanoparticles on
the surface. One would naively expect the for-
mation of random patches of metallic film on
the surface, with no correlation to the moiré
superlattice. Instead, the tapping mode atomic
force microscopy (AFM) map of Fig. 1b re-
veals the formation of metallic films with com-
plete correlation to the rhombohedral domains
of the moiré superlattice, as imaged in mid-IR
nearfield. The triangular metallic film domains
exhibit sharp corners and fine features, as nar-
row as the thin double domain walls separating
two Bernal phases,11 as shown in Fig. 1b (diag-
onal lines along the top right part of the panel).
After 45 days of storage within vacuum, the
same AFM measurement over the surface of
the sample shows degradation of fine nanopar-
ticle features. Particularly along double do-
main walls, previously visible nanoparticle fea-
tures no longer appear in subsequent topog-
raphy scans (Fig. 1c). After 173 additional
days and again 302 days of storage in a dry
N2environment, no further degradation is ob-
served (Fig. 1d). Robust coverage of the
larger triangular regions persists regardless of
the storage conditions of the sample. Theoreti-
3