Neeraj Mishra, Stiven Forti, Filippo Fabbri, Leonardo Martini, Clifford McAleese, Ben R. Conran, Patrick R. Whelan, Abhay Shivayogimath, Bjarke S. Jessen, Lars Buß, Jens Falta, Ilirjan Aliaj, Stefano Roddaro, Jan I. Flege, Peter Bøggild, Kenneth B. K. Teo, Camilla Coletti
Small (2019), Volume 15, Issue 50
https://doi.org/10.1002/smll.201904906
The adoption of graphene in electronics, optoelectronics, and photonics is hindered by the difficulty in obtaining high-quality material on technologically relevant substrates, over wafer-scale sizes, and with metal contamination levels compatible with industrial requirements. To date, the direct growth of graphene on insulating substrates has proved to be challenging, usually requiring metal-catalysts or yielding defective graphene. In this work, a metal-free approach implemented in commercially available reactors to obtain high-quality monolayer graphene on c-plane sapphire substrates via chemical vapor deposition is demonstrated. Low energy electron diffraction, low energy electron microscopy, and scanning tunneling microscopy measurements identify the Al-rich reconstruction (√31×√31)R±9° of sapphire to be crucial for obtaining epitaxial graphene. Raman spectroscopy and electrical transport measurements reveal high-quality graphene with mobilities consistently above 2000 cm2 V−1 s−1. The process is scaled up to 4 and 6 in. wafers sizes and metal contamination levels are retrieved to be within the limits for back-end-of-line integration. The growth process introduced here establishes a method for the synthesis of wafer-scale graphene films on a technologically viable basis.
