1. Department
of Physics, Arizona State University, Tempe, Arizona 85287, United States
2. Environmental
Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
3. Device
Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, California 90095, United States
4. Department
of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei City, Taiwan 10607, Republic of China
5. Department
of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States