[1] Xi An Jiao Tong Univ, Elect Mat Res Lab, Key Lab, Minist Educ, Xian 710049, Shaanxi, Peoples R China
[2] Xi An Jiao Tong Univ, Int Ctr Dielect Res, Sch Elect & Informat Engn, Xian 710049, Shaanxi, Peoples R China
[3] Queen Mary Univ London, Sch Engn & Mat Sci, Mile End Rd, London E1 4NS, England
[4] Inst Mat Phys & Engn, Dept Appl Sci & Technol, Corso Duca Abruzzi 24, I-10129 Turin, Italy
[5] Queen Mary Univ London, Sch Biol & Chem Sci, Mile End Rd, London E1 4NS, England
[6] Queen Mary Univ London, Mat Res Inst, Mile End Rd, London E1 4NS, England