Co clustering and ferromagnetism in chemical vapor deposited Ti1-xCoxO2-δ thin films

Stoichiometric Ti1-xCoxO2 and oxygen-deficient Ti1-xCoxO2-delta thin films were grown on Si (001) by plasma-enhanced metal-organic chemical vapor deposition and their microstructures and ferromagnetic properties were investigated. The stoichiometric film grown at 430 degrees C showed no discernable Co metal clustering or measurable coercive field. In contrast, oxygen-deficient films fabricated without supplying O-2 contained significant Co clusters of similar to 10-20 nm, which appeared to be the major reason for the observed room-temperature ferromagnetism. With increasing oxygen vacancies of the films, the coercive field and saturation magnetization values increased to similar to 460 Oe and similar to 27 emu/cm(3) (1.55 mu(B)/Co atom) approached that for bulk cobalt, respectively. (c) 2007 American Institute of Physics.