Nickel Carbide as a Source of Grain Rotation in Epitaxial Graphene

Abstract

Graphene has a close lattice match to the Ni(111) surface, resulting in a preference for 1 × 1 configurations. We have investigated graphene grown by chemical vapor deposition (CVD) on the nickel carbide (Ni(2)C) reconstruction of Ni(111) with scanning tunneling microscopy (STM). The presence of excess carbon, in the form of Ni(2)C, prevents graphene from adopting the preferred 1 × 1 configuration and leads to grain rotation. STM measurements show that residual Ni(2)C domains are present under rotated graphene. Nickel vacancy islands are observed at the periphery of rotated grains and indicate Ni(2)C dissolution after graphene growth. Density functional theory (DFT) calculations predict a very weak (van der Waals type) interaction of graphene with the underlying Ni(2)C, which should facilitate a phase separation of the carbide into metal-supported graphene. These results demonstrate that surface phases such as Ni(2)C can play a major role in the quality of epitaxial graphene.

Sequential synthesis of free-standing high quality bilayer graphene from recycled nickel foil

“…Under our high carbon precursor concentration, the number of graphene layers was minimized to 2 by the very fast cooling we used. In comparison to other reported works with fast rates in the range of 10e600 C min À1 [13,26,45,46], our average cooling rate is much higher (>900 C min À1 ). Fast cooling facilitates the quenching process and reduces the amount of carbon atoms segregated, only carbon situated near the surface had enough time to segregate and form graphene.…”

Dominantly epitaxial growth of graphene on Ni (1 1 1) substrate

“…In the entire examined parameter range the formation of continuous, large area single layer graphene was observed. Between the nickel and the graphene there is a stronger interaction than between two graphene layers [21,45].…”

“…above the Ni grain boundaries) [15][16][17]. Therefore, a solution to this problem can be the use of single crystal nickel (sc-Ni) without GBs as a substrate to avoid inhomogeneous carbon precipitation and formation of concomitant carbon deposits [15,[18][19][20][21]. A very small lattice misfit (1.3%) exists between Ni [111] and graphene, so an epitaxial growth is anticipated and growth of graphene without GBs seems to be possible.…”

“…That arrangement is called the Rosai structure (hollow site), and only that arrangement provides a global minimum in the interaction energy between the substrate surface and the graphene layer [30]. However, scanning tunneling microscopy (STM) studies demonstrated the presence of GBs in the graphene grown on Ni (111), which was attributed to the fact that monolayer NiC can form locally on the nickel surface and on that NiC the graphene will not grow epitaxially [21]. The presence of single layer thin NiC was only observed below 460 o C [21,31].…”

“…However, scanning tunneling microscopy (STM) studies demonstrated the presence of GBs in the graphene grown on Ni (111), which was attributed to the fact that monolayer NiC can form locally on the nickel surface and on that NiC the graphene will not grow epitaxially [21]. The presence of single layer thin NiC was only observed below 460 o C [21,31]. When deposition temperature exceeded 600 o C only graphene was formed [18].…”