1. Department of Materials Science and Engineering; The Pennsylvania State University; University Park PA 16802 USA
2. School of Optical and Electronic Information; Huazhong University of Science and Technology; Wuhan Hubei 430074 China
3. Materials Research Institute and Department of Electrical Engineering; The Pennsylvania State University; University Park PA 16802 USA
4. Department of Mechanical and Nuclear Engineering; The Pennsylvania State University; University Park PA 16802 USA