L1_0 FePt thin films with [0 01] crystalline growth fabricated by SiO_2 addition: rapid thermal annealing and dot patterning of the films

摘要

FePt films that have a high degree of order S in their L1_0 structure (S > 0.90) and well-defined [001] crystalline growth perpendicular to the film plane were fabricated on thermally oxidized Si substrates by the addition of an oxide and successive rapid thermal annealing (RTA). The mechanism of LI 0 ordering and [001] crystalline growth perpendicular to the film plane arising through the oxide addition and RTA process is also discussed. The Ll0 ordering (S > 0.90) and the [001] crystalline growth were achieved by (1) lowering the activation energy due to in-plane tensile stress and the initiation of L1_0 ordering at a low temperature, (2) [0 0 1 ] crystalline growth through in-plane tensile stress, and (3) enhancement of atomic diffusion via the addition of an oxide and the resultant lowering of the ordering temperature. Effect (1) was observed in the case of SiO_2 addition, effect (2) was generally observed in the case of oxide addition and the RTA process, and effect (3) was prominent in the case of ZnO addition. With the addition of ZnO, the L1_00 ordering started at below 400℃ and was completed at 500℃. Finally, dot patterns were successfully fabricated down to a diameter of 15 nm using electron beam lithography, and the magnetic state of the dot pattern was observed by magnetic force microscopy.