Identification of abrupt intense rhombohedral stacking-transitions in dense-staircase-sublattices created by manual exfoliation of highly oriented pyrolytic graphite

Abstract

Controlling Bernal (AB) to rhombohedral (ABC) stacking-transitions has recently become an important goal towards manipulation of the electronic properties of highly- oriented-pyrolytic-graphite (HOPG) and graphene.In this letter we report a novel investigation of AB to ABC stacking transitions in exfoliated-HOPG-lamellae with variable thickness. The samples were produced by employing I) an edge-tape-exfoliation-method to extrude lamellae of ∼ 80–140 μm thickness and 2) a manual-exfoliation-method, which yielded samples of ∼ 300–450 μm thickness. Characterization was carried out by employing Raman-point/mapping-spectroscopy in certain selected defective-regions of the samples. We demonstrate an abrupt enhancement of the rhombohedral-phase-content within dense- and thick-staircase-sublattices, indicative of a possible crucial role of the sublattice-defect-thickness in preventing ABC to AB post-exfoliation stacking-relaxation. Relaxation of the produced ABC stacks was then found after approximately four weeks from exfoliation (in thick lamellae).

Keywords

• Rhombohedral-graphite
• exfoliation
• phase-transition
• percolative theory