JOURNAL OF APPLIED PHYSICS, vol. 91, no. 1, page. 336 - 343, 2002-01-01
SOLID STATE COMMUNICATIONS, vol. 119, no. 8-9, page. 527 - 532, 2001-01
JOURNAL OF MATERIALS SCIENCE, vol. 31, no. 19, page. 5083 - 5092, 1996-10-01