Fig. 2: Multi-modal characterization of interfacial charge transfer in graphene/CrSBr heterostructures.
From: Engineering anisotropic electrodynamics at the graphene/CrSBr interface
A Left panel: Atomically-resolved topographic STM image of a graphene/CrSBr heterostructure (VS = 1.2 V, I = 50 pA, T = 5.7 K). Right panel: Fast Fourier transform (FFT) of topographic data shows Bragg peaks associated with the graphene atomic lattice (orange circles), the CrSBr atomic lattice (cyan circles) and the second-order moiré pattern (yellow circles) corresponding to a twist angle of ~4° between the graphene armchair axis and CrSBr a-axis. B STS collected on a graphene/CrSBr heterostructure (VS = 1.8 V, I = 50 pA). Inset: Low bias STS (VS = 0.3 V, I = 100 pA) shows a dI/dV minimum at 540 mV corresponding to the Dirac-point energy (EDirac) of graphene shifted due to interfacial charge transfer with the underlying CrSBr. Additional nearby dI/dV minima are also observed at 0 V, 150 mV, and 330 mV. C Typical s-SNOM image of a graphene/CrSBr heterostructure showing oscillations in the near-field S4 amplitude that are characteristic of SPPs (ω = 905 cm–1; S4 normalized relative to the value in the graphene/CrSBr bulk). The graphene is draped over the CrSBr edge (dashed black line), creating a sharp gradient in the graphene charge density that acts as a hard boundary for plasmonic reflections. D The experimental SPP dispersion for graphene/CrSBr (red circles) extracted from the line profiles of SPP fringes collected at different frequencies (see Fig. S3). Calculated Im rp for the experimental stack using an input value of EF = 0.5 eV for the graphene Fermi energy. Maxima in the Im rp correspond well with the experimental dispersion, indicating that the SPP behavior is consistent with an 0.5 eV shift in EDirac of graphene due to charge transfer with the underlying CrSBr.
