Abstract
We investigate the intercalation process of oxygen in-between a PVD-grown graphene layer and different copper substrates as a methodology for reducing the substrate-layer interaction. This growth method leads to an extended defect-free graphene layer that strongly couples with the substrate. We have found, by means of X-ray photoelectron spectroscopy, that after oxygen exposure at different temperatures, ranging from 280 °C to 550 °C, oxygen intercalates at the interface of graphene grown on Cu foil at an optimal temperature of 500 °C. The low energy electron diffraction technique confirms the adsorption of an atomic oxygen adlayer on top of the Cu surface and below graphene after oxygen exposure at elevated temperature, but no oxidation of the substrate is induced. The emergence of the 2D Raman peak, quenched by the large interaction with the substrate, reveals that the intercalation process induces a structural undoing. As suggested by atomic force microscopy, the oxygen intercalation does not change significantly the surface morphology. Moreover, theoretical simulations provide further insights into the electronic and structural undoing process. This protocol opens the door to an efficient methodology to weaken the graphene-substrate interaction for a more efficient transfer to arbitrary surfaces.
Highlights
Over last decade, since the discovery of graphene [1], many methods have been developed for its synthesis and among them chemical vapor deposition (CVD) is the most widely employed [2]
The main objective of this work is to study the oxygen intercalation process in the system formed by physical vapor deposition (PVD) graphene on Cu foil samples
It was first necessary to determine the best conditions for the intercalation process, which are defined by the temperature range and the minimum oxygen dose
Summary
Since the discovery of graphene [1], many methods have been developed for its synthesis and among them chemical vapor deposition (CVD) is the most widely employed [2]. One of the most promising protocols for the transfer of metal-grown graphene is the so-called electrochemical delamination method [5], a simple chemical process that has been demonstrated to be very effective and allows substrate recycling. The protons, released from the electrochemical reaction, intercalate through graphene This method has been widely used on systems with a copper substrate, due to its relatively low interaction with the graphene layer. In order to be able to transfer the graphene layer via the delamination method in systems where the interaction between the graphene layer and the substrate is important, this interaction must be suppressed In this respect, there have been many reports on the graphene decoupling from strongly interacting substrates such as iridium, ruthenium or rhodium, amongst others [6,7,8,9]. From results obtained by intercalating different elements underneath the graphene layer it is possible to tune the electronic properties of the system, obtaining different graphene materials ranging from a strong n-type doping to a strong p-type doping [7]
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