Tailoring the Growth of Graphene on Ru(0001) via Engineering of the Substrate Surface

Abstract

In situ low-energy electron microscopy (LEEM) studies in the epitaxial growth of graphene on Ru(0001) show that the graphene growth can be tailored via surface treatments of the substrate. Downhill growth of graphene was observed over the clean Ru(0001) surface with well-defined steps, forming sector-shaped graphene sheets. When the substrate surface was treated by Ar + sputtering to produce subsurface Ar gas bubbles, round-shape graphene sheets were obtained by growing in both uphill and downhill directions. Correspondingly, anisotropic intercalation of oxygen occurs at the graphene/normal Ru(0001) interface, whereas isotropic intercalation of oxygen occurs at the graphene/Ar-sputtered Ru(0001) interface. The subsurface gas bubbles affect C−Ru interaction, which is attributed to the observed different behaviors of the graphene growth and oxygen intercalation. ■ INTRODUCTIONGraphene has attracted extensive attention due to its fascinating physical and chemical properties.1,2 Controllable growth of high-quality graphene structures is essential to the potential applications of the new material, and epitaxial growth on metals has been regarded as one of the most important routes. 3−9Various factors such as metal substrates, carbon precursors, growth temperature, and pressure have been shown to affect the growth mechanism. 10−19Many experimental and theoretical results have indicated that the graphene growth depends strongly on the interaction between graphene and metals. Generally, two classes of graphene−metal interactions can be identified: physisorption and chemisorption. 20 For example, graphene is strongly chemisorbed on Ru(0001) via significant hybridization of C p z states and Ru d states. 5,21,22 In the initial stage of the graphene growth on Ru(0001), identical-size 7-C6 and 3-C6 graphene nanoclusters form on the Ru(0001) terraces, which is thought to be mediated by the substrate-induced clustering effect.23 At higher temperatures, the lower edges of the substrate steps are found to be the preferential nucleation sites for graphene sheets.11,24,25 Downhill growth of graphene was almost exclusively observed, producing continuous sectorshaped carpets across descending substrate steps. 5,13,15,26 Graphene on Pt(111) is a typical system with weak interfacial bonding. In the nucleation stage, the surface carbon nanostructures are inhomogeneous. 23,27 Following the nucleation, each graphene domain expands by attachment of carbon to its edge, which produces a single-crystalline graphene sheet. In contrast to the unidirectional growth on Ru(0001), graphene expands across the Pt(111) steps in the uphill and downhill directions. 9 The climbing up growth of graphene sheets over substrate steps has been observed on Cu(111) and Ir(111) surfaces, which also interact weakly with graphene. 7,8,19 The previous results indicate that the interaction of carbon with a metal substrate controls the epitaxial growth of graphene. The strong interaction of carbon atoms with metal surfaces, in particular, the step sites, t...

Keeping argon under a graphene lid—Argon intercalation between graphene and nickel(111)

“…This is in line 162 with argon TPD spectra, which show that argon desorption from the 163 surface-near region is completed at this temperature, when Ar is 164 implanted with 1 keV kinetic energy [31]. as described for other materials such as ruthenium [33,34], aluminum 191 or silicon [35,36], where two Ar contributions are found in XPS. Fig.…”

“…the attachment of OH or H groups, the electronic 31 structure and resistivity of graphene can significantly be altered, or 32 even changed from semi-metallic to semi-conducting [7,8]. Besides its 33 electronic structure, also the mechanical and chemical properties of 34 graphene are of interest: The atomic structure of graphene, that is, 35 close packed six membered rings of carbon atoms, is proposed to be 36 helium leak tight, and it was therefore suggested to be used as a gas bar-37 rier [9]. In this context, applications for gas containment, gas separation 38 [10][11][12], or protective coatings are discussed [13][14][15].…”

Facile oxygen intercalation between full layer graphene and Ru(0001) under ambient conditions

“…Recent experiments, however, show that many gases can intercalate under graphene flakes grown on metal surfaces [16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Particularly, oxygen intercalation at the graphene/metal interfaces in O 2 atmosphere and at elevated temperatures has been reported [16][17][18][19].…”

Epitaxial Graphene and Graphene–Based Devices Studied by Electrical Scanning Probe Microscopy

“…In general, LEEM often serves as a very useful tool to accurately determine the local extent of graphene layers as well as the layer thickness. In particular, the role of the defective structure [42,43] and active treatment of the substrate [44] in formation of graphene layers were successfully studied. Another interesting approach is investigation of the effect of oxygen adsorption on the local structure and electronic properties of monolayer graphene.…”