Author Affiliations

Sangwan Sim,^*,****** Houk Jang,^*,****** Nikesh Koirala,^**,****** Matthew Brahlek,^**,****** Ji Ho Sung,^{***,****,******} Jun Park,^*,****** Soonyoung Cha,^*,****** Seongshik Oh,^{**,*****,******} Moon-Ho Jo,^{***,****,*****,******} Jong-Hyun Ahn,^*,****** and Hyunyong Choi^*,******

^*School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea

^**Department of Physics and Astronomy, Rutgers the State University of New Jersey, Piscataway, New Jersey 08854, USA

^***Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea

^****Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea

^*****Institute for Advanced Materials, Devices and Nanotechnology, Rutgers the State University of New Jersey, Piscataway, New Jersey 08854, USA

^******Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea