Drastic reduction in the growth temperature of graphene on copper via enhanced London dispersion force

Abstract

London dispersion force is ubiquitous in nature, and is increasingly recognized to be an important factor in a variety of surface processes. Here we demonstrate unambiguously the decisive role of London dispersion force in non-equilibrium growth of ordered nanostructures on metal substrates using aromatic source molecules. Our first-principles based multi-scale modeling shows that a drastic reduction in the growth temperature, from ,10006C to ,3006C, can be achieved in graphene growth on Cu(111) when the typical carbon source of methane is replaced by benzene or p-Terphenyl. The London dispersion force enhances their adsorption energies by about (0.5-1.8) eV, thereby preventing their easy desorption, facilitating dehydrogenation, and promoting graphene growth at much lower temperatures. These quantitative predictions are validated in our experimental tests, showing convincing demonstration of monolayer graphene growth using the p-Terphenyl source. The general trends established are also more broadly applicable in molecular synthesis of surface-based nanostructures. , and molecular assembly at surfaces 6,7 . To a large extent, such advances through quantitative definitive studies were enabled by the availability of more accurate descriptions of the weak interactions associated with long-range electron correlation effects within first-principles approaches [8][9][10] . In this study, we exploit the power of predictive modeling using state-of-the-art first-principles calculations within density functional theory (DFT), coupled with kinetic rate equation analysis and definitive experimental tests, to establish unambiguously the decisive role of London dispersion force in molecular self-assembly of aromatic source molecules. We choose graphene growth on Cu substrates as an important class of prototypical model systems, and the microscopic mechanisms revealed are broadly applicable in other nanofabrication processes via molecular assembly.Because of its exotic electronic properties [11][12][13][14][15]

Comparison of graphene growth on arbitrary non-catalytic substrates using low-temperature PECVD

“…However, in the low-temperature regime used in this work, while thermal dehydrogenation of CH 4 on Cu is not attainable [26], dehydrogenation is realized due to the energetic plasma, thus allowing graphene growth to occur at reduced temperatures. To validate this hypothesis, we executed a test run with the same process conditions but without the plasma and found that no graphene growth occurs on any of the samples.…”

Mechanisms of Graphene Growth on Metal Surfaces: Theoretical Perspectives

“…Notice that desorption is an important process to compete with dehydrogenation. For some precursor molecules, such as benzene, vdW interaction can thus play an important role in graphene growth …”

“…First principles calculations can reliably predict reaction energies and barriers for elementary processes. Notice that, although the general gradient approximation (GGA) of density functional theory (DFT) is widely used for this purpose, the inclusion of van der Waals (vdW) correction can also be very critical to reach a high accuracy in some cases . Using first principles results as an input, kinetic Monte Carlo (kMC) simulation can then be performed to study the growth dynamics.…”

Heterogeneous Solid Carbon Source‐Assisted Growth of High‐Quality Graphene via CVD at Low Temperatures

“…[ 8 ] High temperatures T > 1000 °C are required for the synthesis of CVD graphene using CH 4 because the adsorption and dehydrogenation of methane on Cu surfaces rarely occurs at T < 800 °C due to the high activation energy barrier for these processes. [ 9 ] The required high growth temperatures also impose disadvantages of high production costs and safety problems. Therefore, an effi cient and safe method for synthesizing graphene at low temperatures is needed.…”

“…[ 10,11 ] Solid hydrocarbons can be used safely in high-T processes while enabling the bottom-up growth of prepatterned graphene for use in electronic applications. [ 6 ] The use of polycyclic aromatic hydrocarbons (PAHs) as carbon sources for graphene growth can signifi cantly reduce the growth T to 400-600 °C because the interaction between PAH and Cu reduces the activation energy for dehydrogenation and nucleation on the Cu surface at low T ; [ 9,12 ] however, graphene grown using PAHs at low T typically includes numerous defects that limit the utility of the graphene in electronic devices. [ 13 ] A lack of understanding about defect formation in graphene grown from PAH sources has hindered the rational engineering of CVD methods for the growth of high-quality graphene at low T .…”