Wei Liu, Stephan Kraemer, Deblina Sarkar, Hong Li, Pulickel M. Ajayan, Kaustav Banerjee. Chem. Mater. 2014, 26, 2, 907-915

Abstract

Bilayer graphene has attracted wide attention due to its unique band structure and bandgap tunability under specific (Bernal or AB) stacking order. However, it remains challenging to tailor the stacking order and to simultaneously produce large-scale and high-quality bilayer graphene. This work introduces a fast and reliable method of growing high-quality Bernal stacked large-area (>3 in. × 3 in.) bilayer graphene film or trilayer graphene domains (30 μm × 30 μm) using chemical vapor deposition (CVD) on engineered Cu–Ni alloy catalyst films. The AB stacking order is evaluated by Raman spectra, electron diffraction pattern, and dual gate field-effect-transistor (FET) measurements, and a near-perfect AB stacked bilayer graphene coverage (>98%) is obtained. The synthesized bilayer and trilayer graphene with Bernal stacking exhibit electron mobility as high as 3450 cm2/(V·s) and 1500 cm2/(V·s), respectively, indicating comparable quality with respect to exfoliated bilayer and trilayer graphene. The record high (for CVD bilayer graphene) ON to OFF current ratios (up to 15) obtained for a large number (>50) of dual-gated FETs fabricated at random across the large-area bilayer graphene film also corroborates the success of our synthesis technique. Moreover, through catalyst engineering, growth optimization, and element analysis of catalyst, it is shown that achieving surface catalytic graphene growth mode and precise control of surface carbon concentration are key factors determining the growth of high quality and large area Bernal stacked bilayer graphene on Cu–Ni alloy. This discovery can not only open up new vistas for large-scale electronic and photonic device applications of graphene but also facilitate exploration of novel heterostructures formed with emerging beyond graphene two-dimensional atomic crystals.