[1] Wen Pengyan, Zhang Shuming, Liu Jianping, et al. Journal of Applied Physics, 2016, 119(21): 213107.

[2] Li D, Sun X, Song H, et al. Advanced Materials, 2012, 24(6): 845.

[3] Zhang M, Banerjee A, Bhattacharya P. Journal of Crystal Growth, 2011, 323(1): 470.

[4] Wu Y R, Lin Y Y, Huang H H, et al. Journal of Applied Physics, 2009, 105(1): 013117.

[6] Li Z C, Liu J P, Feng M X, et al. Journal of Applied Physics, 2013, 114(9): 093105.

[7] Liu H, Lin T, Wan L, et al. Materials Research Express, 2018, 5(8): 086201.

[8] Lin T, Kuo H C, Jiang X D, et al. Nanoscale Research Letters, 2017, 12(1): 137.

[9] Cho Y H, Lee S K, Kwack H S, et al. Applied Physics Letters, 2003, 83(13): 2578.

[10] Yang F, Wilkinson M, Austin E J, et al. Physical Review Letters, 1993, 70(3): 323.

[11] Minsky M S, Watanabe S, Yamada N. Journal of Applied Physics, 2002, 91(8): 5176.

[12] Chichibu S F, Onuma T, Sota T, et al. Journal of Applied Physics, 2003, 93(4): 2051.