The catalytic potential of high-κ dielectrics for graphene formation

Abstract

The growth of single and multilayer graphene nano-flakes on MgO and ZrO 2 at low temperatures is shown through transmission electron microscopy. The graphene nano-flakes are ubiquitously anchored at step edges on MgO (100) surfaces. Density functional theory investigations on MgO (100) indicate C 2 H 2 decomposition and carbon adsorption at step-edges. Hence, both the experimental and theoretical data highlight the importance of step sites for graphene growth on MgO.PACS numbers: 81.05.ue, 81.16.Hc Graphene promises a great leap forward in electronic device speed due to its high charge carrier mobility. 1 Restricting its dimensions sufficiently (< 10 nm for room temperature applications) to introduce finite size effects can open an energy gap. 2,3 Confining the width and keeping the length infinitely long forms a graphene nano-ribbon (GNR) whilst restricting both the width and length forms a graphene nano-flake. Interesting electronic properties can also arise from bi-layer nanoribbons/flakes and even higher order stacked flakes. Their energy gaps are not just dependent on size, but also on the edge states and electric fields. [4][5][6][7][8] Hence, the richness of electronic properties afforded by graphene causes great excitement for its use in nano-electronic devices. However, various technical hurdles exist. For example, the implementation of graphene in nano-electronic technology is hindered by difficulties in obtaining defect free and clean graphene on suitable substrates. The substrates need to be insulating, ideally have a high dielectric constant, κ, to prevent gate current leakage and hence allow greater miniaturization. In graphene, the carrier concentration and polarity can be modulated by an electric field. However, the fabrication of graphene devices with an atomically uniform gate dielectric, so as to provide a uniform electric field over the active graphene area without damaging the graphene surface remains a challenge. 9 For this reason and the ease with which graphene can be observed, most reported graphene devices are fabricated on Si/SiO 2 which forms a global back gate. Attempts to deposit dielectrics on the surface of graphene to form top gates have been made, however the deposition processes employed tend to damage the graphene, see e. g. Ref. 10. The situation for graphene based devices is further complicated due to restrictions imposed by most of the available synthesis routes. Aside from mechanical cleaving, graphene synthesis generally involves the use of metal catalysts 11-13 which then necessitates postsynthesis transfer of the graphene or in the case of epitaxia) Electronic mail: f.boerrnert@ifw-dresden.de b) Electronic mail: m.ruemmeli@ifw-dresden.de ally grown graphene in SiC high temperatures are required. 14 Other synthesis routes like chemical exfoliation or the necessary transfer steps from the aforementioned routes to dielectric substrates introduce high levels of contamination and defects into the graphene making such synthesis routes incompatible with current planar fabricat...

Topological Defects in Metal‐Free Nanocarbon for Oxygen Electrocatalysis

“…The porous MgO derived from Mg(OH) 2 provides on one hand an effi cient substrate to catalyse the decomposition of carbon/nitrogen sources, resulting in ultrathin graphene layers with a mesoporous framework and 3D conductive scaffold (NGM: ≈1.2 S cm −1 , GM: ≈5.8 S cm −1 ). [45][46][47] While on the other hand, the in-situ released water vapor and gas from the precursor decomposition and the random nucleation-growth behaviors from different sites of precursors on the substrate generate micro holes and edge sites. The resulting NaCl by-products can also serve as effective pore-forming agents ( Figure S6, Supporting Information).…”

Vertical Graphene Growth from Amorphous Carbon Films Using Oxidizing Gases

“…The direct chemical vapor deposition (CVD) growth of graphene over oxides is possible but issues in terms of the graphene quality and scalability remain. [6][7][8][9][10] Plasma enhanced CVD, PECVD, can be used to grow (vertical) graphene on almost any substrate, and like thermal CVD graphene growth over oxides, this is for the most part also a non-catalytic growth process. [11][12][13][14] The catalyst-free growth of graphene from amorphous carbon has also been explored.…”

Understanding the catalyst-free transformation of amorphous carbon into graphene by current-induced annealing

“…Another surface that can provide suitable sites for growth is a bulk oxide support without any metal catalyst present where the carbon precursor is supplied by a hydrocarbon feedstock11121314. In the case of graphene growth from stable oxides as the support material, carbon dissolution is unlikely and therefore the growth probably occurs through surface diffusion processes.…”