1. H. Strunz, B. H. Geier, and E. Seliger, Am. Mineral. 44, 906 (1959).
2. A. Rocket and R. W. Birkmire, J. Appl. Phys. 70, R80 (1991).
3. J. C. Rife, R. N. Dexter, P. M. Bridenbaugh, and B. W. Veal, Phys. Rev. B 16, 4491 (1977).
4. C. Parlak and R. Eryigit, Phys. Rev. B 73, 245217 (2006).
5. F. Y. Liu, J. Yang, J. L. Zhou, et al., Thin Solid Films 520, 2781 (2012).