Continuous and ultrathin platinum films on graphene using atomic layer deposition: a combined computational and experimental study

Abstract

Integrating metals and metal oxides with graphene is key in utilizing its extraordinary material properties that are ideal for nanoelectronic and catalyst applications. Atomic layer deposition (ALD) has become a key technique for depositing ultrathin, conformal metal(oxide) films. ALD of metal(oxide) films on graphene, however, remains a genuine challenge due to the chemical inertness of graphene. In this study we address this issue by combining first-principles density functional theory (DFT) simulations with ALD experiments. The focus is on the Pt ALD on graphene, as this hybrid system is very promising for solar and fuel cells, hydrogen technologies, microreactors, and sensors. Here we elucidate the surface reactions underpinning the nucleation stage of Pt ALD on pristine, defective and functionalized graphenes. The employed reaction mechanism clearly depends on (a) the available surface groups on graphene, and (b) the ligands accompanying the metal centre in the precursor. DFT calculations also indicate that graphene oxide (GO) can afford a stronger adsorption of MeCpPtMe, unlike Pt(acac), as compared to bare (non-functionalized) graphene, suggesting that GO monolayers are effective Pt ALD seed layers. Confirming the latter, we evince that wafer-scale, continuous Pt films can indeed be grown on GO monolayers using a thermal ALD process with MeCpPtMe and O gas. Besides, the current in-depth atomistic insights are of practical use for understanding similar ALD processes of other metals and metal oxides on graphene.

Uniform Atomic Layer Deposition of Al2O3 on Graphene by Reversible Hydrogen Plasma Functionalization

“…A detailed discussion regarding the choice of these models can be found in the Supporting Information (HG) and elsewhere (PG and GO). 37 …”

Atomic Layer Deposition for Graphene Device Integration

“…ALD on pristine graphene and HOPG is a challenge due to the lack of reactive surface sites or functional groups on graphene. As a result ALD on pristine graphene often leads to non‐uniform film coverage or even the absence of film growth ( Figure ) . However, for graphene device integration the deposition of uniform layers on graphene is essential.…”

“…The preferential deposition on defect sites, grain boundaries and graphene wrinkles is a result of the lack of functionalized dangling bonds on the graphene basal plane. Only on defect sites and grain boundaries where functional groups are present ALD nucleation is possible . Density functional theory (DFT) calculations have shown that various ALD precursors tend to physisorb on the graphene basal plane .…”

“…The initiation of ALD growth on graphene however, is known to be a challenge . This is because graphene consists of pure sp 2 bonded carbon and therefore lacks out‐of‐plane bonds or surface groups needed for the initiation of ALD growth . To overcome these nucleation issues several different surface preparation techniques to initialize ALD on graphene have been explored over the years.…”

Oriented Attachment and Nanorod Formation in Atomic Layer Deposition of TiO2 on Graphene Nanoplatelets

“…1 Nonetheless, ALD growth can still start from the very first cycle because, in contrast to ideal graphene or perfect graphitic surfaces, the surface of graphene nanoplatelets is inherently defective, and as such it can be activated by the incorporation of the oxygen-containing species during the ozone pretreatment step. 17,41,42 …”