Direct Visualization of Native Defects in Graphite and Their Effect on the Electronic Properties of Bernal-Stacked Bilayer Graphene

Abstract

Graphite crystals used to prepare graphene-based heterostructures are generally assumed to be defect free. We report here scanning tunneling microscopy results that show graphite commonly used to prepare graphene devices can contain a significant amount of native defects. Extensive scanning of the surface allows us to determine the concentration of native defects to be 6.6 × 108 cm–2. We further study the effects of these native defects on the electronic properties of Bernal-stacked bilayer graphene. We observe gate-dependent intravalley scattering and successfully compare our experimental results to T-matrix-based calculations, revealing a clear carrier density dependence in the distribution of the scattering vectors. We also present a technique for evaluating the spatial distribution of short-scale scattering. Finally, we present a theoretical analysis based on the Boltzmann transport equation that predicts that the dilute native defects identified in our study are an important extrinsic source of scattering, ultimately setting the charge carrier mobility at low temperatures.

Weak localisation driven by pseudospin-spin entanglement

“…For the case of ultra-clean graphene (i.e. with reduced intervalley scattering due to the absence of point-like defects [54][55][56] ) without SOC, we observe the same WAL behaviour as the SOC 2DEG in both theory and experiment [57][58][59][60] . The intrinsic SOC in graphene is negligible and so cannot be responsible for this observation of WAL.…”

Gate-Tunable Resonance State and Screening Effects for Proton-Like Atomic Charge in Graphene

“…Indeed, we find that such a perturbation, with Δ 0 = −7 eV, Δ 1 = −0.7 eV, and δt = 0.5 eV, shown in Figure b, gives a good agreement with the ab initio results (Figure c), reinforcing the short-range nature of the N-induced perturbation. In addition, real-space spectral function maps calculated using the TB formalism reproduce experimental d I /d V maps by revealing both the characteristic triangular shape near to N (Figure f) and the surrounding FO concentric rings, arising from the intravalley scattering (Figure d,e). We note that earlier work presents different TB parameters.…”

Characterization and Manipulation of Intervalley Scattering Induced by an Individual Monovacancy in Graphene

“…In pristine graphene, electrons have valley degree of freedom, providing the opportunity of information coding and processing [10][11][12][13][14]. However, atomic defects can generate intervalley scattering [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32], which greatly limits the ability to manipulate the valley. Previous studies on defect-induced intervalley scattering mainly relied on mesoscopic transport measurements [25][26][27][28][29][30][31][32][33][34][35][36].…”