1. State Key Laboratory of Electronic Thin Films and Integrated DevicesSchool of Optoelectronic Science and EngineeringUniversity of Electronic Science and Technology of China (UESTC)ChengduSichuan610054China
2. Department of Electronic and Electrical EngineeringUniversity College LondonTorrington PlaceLondonWC1E 7JEUnited Kingdom
3. Institute of Fundamental and Frontier SciencesUniversity of Electronic Science and Technology of ChinaChengdu610054China
4. Department of Electrical and Computer EngineeringCenter for Nanoscale Science and EngineeringUniversity of KentuckyLexingtonKY40506USA