High temperature MBE of graphene on sapphire and hexagonal boron nitride flakes on sapphire

Cheng, Tin S. and Davies, Andrew and Summerfield, Alex and Cho, YongJin and Cebula, Izabela and Hill, Richard J. A. and Mellor, Christopher J. and Khlobystov, Andrei N. and Taniguchi, Takashi and Watanabe, Kenji and Beton, Peter H. and Foxon, C. Thomas and Eaves, Laurence and Novikov, Sergei V. (2016) High temperature MBE of graphene on sapphire and hexagonal boron nitride flakes on sapphire. Journal of Vacuum Science and Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 34 (2). 02L101. ISSN 2166-2754

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    Abstract

    The discovery of graphene and its remarkable electronic properties has provided scientists with a revolutionary material system for electronics and optoelectronics. Here, the authors investigate molecular beam epitaxy (MBE) as a growth method for graphene layers. The standard dual chamber GENxplor has been specially modified by Veeco to achieve growth temperatures of up to 1850°C in ultrahigh vacuum conditions and is capable of growth on substrates of up to 3 in. in diameter. To calibrate the growth temperatures, the authors have formed graphene on the Si-face of SiC by heating wafers to temperatures up to 1400°C and above. To demonstrate the scalability, the authors have formed graphene on SiC substrates with sizes ranging from 10 × 10 mm2 up to 3-in. in diameter. The authors have used a carbon sublimation source to grow graphene on sapphire at substrate temperatures between 1000 and 1650°C (thermocouple temperatures). The quality of the graphene layers is significantly improved by growing on hexagonal boron nitride (h-BN) substrates. The authors observed a significant difference in the sticking coefficient of carbon on the surfaces of sapphire and h-BN flakes. Our atomic force microscopy measurements reveal the formation of an extended hexagonal moiré pattern when our MBE layers of graphene on h-BN flakes are grown under optimum conditions. The authors attribute this moiré pattern to the commensurate growth of crystalline graphene on h-BN.