Epitaxial growth of Fe_3Si/CaF-2/Fe_3Si magnetic tunnel junction structures on CaF_2/Si(111) by molecular beam epitaxy

摘要

The Fe_3Si(24 nm)/CaF_2(2 nm)/Fe_3Si(12 nm) magnetic tunnel junction (MTJ) structures were grown epitaxially on CaF_2/Si(111) by molecular beam epitaxy (MBE). The 12-nm-thick Fe_3Si underlayer was grown epitaxially on CaF_2/Si(111) at approximately 400 ℃; however, the surface of the Fe_3Si film was very rough, and thus a lot of pinholes are considered to exist in the 2-nm-thick CaF_2 barrier layer. The average roughness (Ra) of the CaF_2 barrier layer was 7.8 nm. This problem was overcome by low-temperature deposition of Fe and Si at 80 ℃ on CaF_2/Si(111), followed by annealing at 250 ℃ for 30 min to form the Fe_3Si layer. The Ra roughness was significantly reduced down to approximately 0.26 nm. A hysteresis loop with coercive field H_c of approximately 25 Oe was obtained in the magnetic field dependence of Kerr rotation at room temperature (RT).