Graphene monolayer produced on Pt reusable substrates for transparent conductive electrodes applications

Abstract

We developed a growth process by chemical vapour deposition (CVD) allowing high quality single layer graphene using a microelectronic industrial tool able to deposit graphene on 200 mm substrates. Growth was achieved by catalytic decomposition of CH4 at a very low CH4/H2 flow rate ratio to decrease the nucleation density of graphene on platinum (Pt) and favour large graphene grains. Graphene production with a high nucleation control is obtained on Pt thin film substrates at 800°C compared to 1000°C for Cu. In these conditions, grains with typically 10th of µm size are obtained. Each grain is formed with high quality single crystal(s) without any obvious atomic defect as verified by high resolution transmission electron microscopy (HRTEM). To better assess the graphene quality, Raman spectra and mapping were performed. The intensity ratio (IG/I2D) and linewidth (G and 2D band) attested that the deposited graphene is made of a single layer at least on the tested mapped area. We devised a new electrochemical transfer method which should allow re-using the Pt substrates. Graphene sheets transferred by electrochemistry are of high quality: the density of defects such as cracks and holes is minimised. The sheet resistance of a monolayer of graphene transferred onto glass by the electrochemical process is around RS = 1300 Ω/square (four point method). By improving this route we hope to produce high quality contaminant-free graphene grade material.