1. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA
2. Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA
3. SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025, USA
4. Department of Chemical Science and Engineering, Tokyo Institute of Technology, Ookayama Meguro-ku, Tokyo 152-8550, Japan