L1 0 FePt thin films with [0 0 1] crystalline growth fabricated by SiO 2 addition—rapid thermal annealing and dot patterning of the films

Abstract

FePt films that have a high degree of order S in their L1 0 structure ( S>0.90) and well-defined [0 0 1] 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 L1 0 ordering and [0 0 1] crystalline growth perpendicular to the film plane arising through the oxide addition and RTA process is also discussed. The L1 0 ordering ( S>0.90) and the [0 0 1] 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 0 ordering started at below 400 °C and was completed at 500 °C. 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.