Journal Article

Scanning tunnelling microscopy and spectroscopy of ultra-flat graphene on hexagonal boron nitride

Bulmash, Danny, Jacquod, Philippe, Sanchez-Yamagishi, Javier, Deshpande, Aparna, Jarillo-Herrero, Pablo, LeRoy, Brian J., Xue, Jiamin, Watanabe, K., Taniguchi, T.

2011

Overview

Using boron nitride as a substrate for graphene has been suggested as a promising way to reduce the disorder in graphene caused by space fluctuations. It is now shown by scanning tunnelling microscopy that graphene conforms perfectly to boron nitride and the charge fluctuations are minimal compared with the conventionally used substrate, silica. Boron nitride could really be the natural graphene substrate. Graphene has demonstrated great promise for future electronics technology as well as fundamental physics applications because of its linear energy–momentum dispersion relations which cross at the Dirac point 1 , 2 . However, accessing the physics of the low-density region at the Dirac point has been difficult because of disorder that leaves the graphene with local microscopic electron and hole puddles 3 , 4 , 5 . Efforts have been made to reduce the disorder by suspending graphene, leading to fabrication challenges and delicate devices which make local spectroscopic measurements difficult 6 , 7 . Recently, it has been shown that placing graphene on hexagonal boron nitride (hBN) yields improved device performance 8 . Here we use scanning tunnelling microscopy to show that graphene conforms to hBN, as evidenced by the presence of Moiré patterns. However, contrary to predictions 9 , 10 , this conformation does not lead to a sizeable band gap because of the misalignment of the lattices. Moreover, local spectroscopy measurements demonstrate that the electron–hole charge fluctuations are reduced by two orders of magnitude as compared with those on silicon oxide. This leads to charge fluctuations that are as small as in suspended graphene 6 , opening up Dirac point physics to more diverse experiments.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/301/119/998 / 639/301/357/918 / 639/301/930/328/968 / 639/301/930/527 / Biomaterials / Boron / Boron nitride / Charge / Chemistry and Materials Science / Condensed Matter Physics / Devices / Disorders / Electrons / Fabrication / Fluctuation / Fluctuations / Graphene / letter / Materials Science / Microscopy / Nanotechnology / Optical and Electronic Materials / Physics / Scanning tunneling microscopy / Spectroscopy / Spectrum analysis / Technology