  A scalable platform to synthesize ultrathin heavy metals may enable high
efficiency charge-to-spin conversion for next-generation spintronics. Here we
report centimeter-scale synthesis of air-stable, epitaxially registered
monolayer Pb underneath bilayer graphene on SiC (0001) by confinement
heteroepitaxy (CHet). Diffraction, spectroscopy, and microscopy reveal
CHet-based Pb intercalation predominantly exhibits a mottled hexagonal
superstructure due to an ordered network of Frenkel-Kontorova-like domain
walls. The system's air stability enables ex-situ spin torque ferromagnetic
resonance (ST-FMR) measurements that demonstrate charge-to-spin conversion in
graphene/Pb/ferromagnet heterostructures with a 1.5x increase in the effective
field ratio compared to control samples.
