JAPANESE JOURNAL OF APPLIED PHYSICS, vol. 47, no. 2, page. 862 - 866, 2008-02
ELECTROCHEMICAL AND SOLID STATE LETTERS, vol. 11, no. 2, page. H29 - H31, 2008-01
SOLID-STATE ELECTRONICS, vol. 52, no. 1, page. 1 - 6, 2008-01