Li, Peining
Lewin, Martin
Kretinin, Andrey V.
Caldwell, Joshua D.
Novoselov, Kostya S.
Taniguchi, Takashi
Watanabe, Kenji
Gaussmann, Fabian
Taubner, Thomas
Article History
Received: 24 December 2014
Accepted: 14 May 2015
First Online: 26 June 2015
Competing interests
: The authors declare no competing financial interests.