[2] [2] Ho Seong Jang, Jong Hyuk Kang, Yu-Ho Wonm Sora Lee, et al. Applied

          Physics Letters, 2007, 90: 071908.

[3] [3] Physics Letters, 2004, 84(10): 1647.

          Joung Kyu Park, Chang Hae Kim, Seung Hyok Park, et al. Applied

[4] [4] Liu Ru-shi, Liu Yu-huan, Nitin C Bagkar, et al. Applied Physics

          Letters, 2007, 91: 061119.

[5] [5] Piao Xiaoqing, Machida Ken-ichi, Horikawa Takashi, et al. Journal

          of The Electrochemical Society, 2008, 155: J17.

[6] [6] Sivakumar V, Varadaraju U V. Journal of The Electrochemical

          Society, 2007, 154(5): J167.

[7] [7] Hu Yunsheng, Zhuang Weidong, Ye Hongqi, et al. Journal of Alloys

          and Compounds, 2005, 390: 226.

[8] [8] Tang Yu-sheng, Hu Shu-fen, Lin Chun-che, et al. Applied Physics

          Letters, 2008, 93: 131114.

[9] [9] Hu Yunsheng, Zhuang Weidong, Ye Hongqi, et al. Journal of

          Luminescence, 2005, 111: 139.

[10] [10] Yang Zhiping, Wang Shaoli, Yang Guangwei, et al. Materials Letters,

          2007, 61(30): 5258.

[11] [11] Electrochemical Society, 2008, 155: J310.

          Guo Chongfeng, Luan Lin, Xu Yan, et al. Journal of the

[12] [12] Chang Chun-kuei, Chen Teng-ming. Applied Physics Letters, 2007, 91:

          081902.

[13] [13] Vengala B Rao, Rambabu U, Buddhudu S. Physica B, 2007, 391: 339.

[14] [14] Manam J, Sharma S K. Journal of Materials Science, 2004, 39(20):

          6203.

[15] [15] 2009, 63: 751.

          Li Panlai, Wang Zhijun, Yang Zhiping, et al. Materials Letters,

[17] [17] Sun L D, Qian C, Liao C S, et al. Solid State Communications, 2001,

          119: 393.