1. W. E. Spicer, Surf. Sci. 86, 763 (1979).
2. V. N. Bessolov and M. V. Lebedev, Fiz. Tekh. Poluprovodn. 32(11), 1281 (1998) [Semiconductors 32 (11), 1141 (1998)].
3. M. V. Lebedev, N. Shimomura, and Ya. Fukuda, Fiz. Tekh. Poluprovodn. 41(5), 539 (2007) [Semiconductors 41 (5), 521 (2007)].
4. A. Ohtake, T. Komura, T. Hanada, et al., Phys. Rev. B 59(12), 8032 (1999).
5. B. I. Sysoev, N. N. Bezryadin, G. I. Kotov, et al., Fiz. Tekh. Poluprovodn. 29(1), 24 (1995) [Semiconductors 29 (1), 12 (1995)].