Controlling the number of layers of Mo-grown CVD graphene through the catalyst thickness

Abstract

Depending on the applications based on graphene, single-layer or few-layer graphene would be more beneficial. Ideally, graphene could be nucleated directly with the required thickness. However, some aspects related to graphene thickness and uniformity control still need to be solved. This work aims to better understand graphene formation using Mo thin films as a catalyst. The grown graphene films were characterized using SEM, TEM, XPS, AFM, standard Raman spectroscopy and 3D Raman surface imaging. A correlation between the catalyst thickness and the number of layers is established. All the characterization techniques show that the number of graphene layers inversely scales with the Mo catalyst thickness used for the graphene synthesis. Then, by simply adjusting the catalyst thickness, the number of graphene layers can be engineered from few-layer graphene (FLG) up to multi-layer graphene (MLG). A pinhole distribution of 1 % was detected on the films synthesized on 50 nm and 100 nm Mo thicknesses after the catalyst was etched. On the synthesized FLG (500 nm Mo), no holes were observed on the surface film after the etching process and even after a transfer onto another substrate. These results can enable the formation of FLG with a controlled thickness and good uniformity.