1. Materials Research Centre, Indian Institute of Science, Bangalore, Karnataka 560012, India
2. Department of Materials Science & Engineering, University of California, Berkeley, California 94720, United States
3. Department of Physics, University of California, Berkeley, California 94720, United States
4. Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Avenida de los Castros s/n, E-39005 Santander, Spain
5. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
6. School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China
7. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
8. Department of Materials Science and Nanoengineering, Department of Physics and Astronomy, Rice University, Houston, Texas 77251, United States