Stacking-dependent properties of trilayer graphene

Abstract

Graphene, a single atomic layer of graphite, consists of carbon atoms arranged in a honeycomb lattice. Since its experimental isolation on insulating SiO2 (silica) substrates in 2004,1 it has quickly taken the scientific and technological communities by storm. It has been dubbed as a ‘carbon flatland,’ ‘carbonwonderland,’ and a new ‘wonder material’ because of its extraordinary material properties. For instance, it is the ultimate 2D system: it is softer than silk yet stronger than steel; it conducts heat better than copper; and it conducts electricity better than silicon. It is also transparent and elastic, yet as a capping layer it is impermeable to even the smallest molecules. These and other material properties continue to astound. The 2010 Nobel Prize in physics was awarded to Andre Geim andKonstantinNovoselov for their groundbreaking experiments on graphene. The initial flurry of activity following discovery mainly focuses on single-layer graphene. Its few-layer cousins were largely ignored, since they are assumed to be similar to graphite, a well-studied material. More recently, however, researchers have realized that few-layer graphene (FLG) hosts a wealth of fascinating physics and potential applications.2–5 For instance, band structures are more amenable to band-gap engineering and application in digital electronics, while allowing stronger electron interactions that lead to novel correlated phenomena. Equally fascinating is the dependence of their properties on the manner in which successive graphene layers are stacked.6–9 Most FLG and graphite are Bernal-stacked. In other words, one corner of the hexagons of the top sheet is located above the center of the hexagons of the bottom sheet. Because the adjacent atoms in each graphene sheet are considered crystallographically inequivalent, there are up to 2n 2 distinct stacking sequences in n-layer graphene, with different band structures. Stacking order thus provides an important yet rarely explored degree of freedom for tuning the electronic properties of FLG. Figure 1. (a) Schematics of ABA (Bernal)and ABC (rhombohedral)stacked three-layer graphene (TLG), respectively. (b) Resistance (R) vs. charge density n (in log-linear scales) for suspended ABA (red curve) and ABC (blue curve) TLG devices. Upper inset: Scanning electron microscopy image of a suspended TLG graphene device. Scale bar: 2 m.