講演情報
[16a-D61-2]Spin Hall effect in annealed BiSb topological thin films deposited on Si/SiOx substrates
〇(D)HOANGHUY HO1, WENTAO L.1, TAKAHASHI S.2, HIRAYAMA Y.2, KATO Y.2, NAM HAI PHAM1 (1.Tokyo Tech., 2.Samsung Japan Corp.)
キーワード：
BiSb、topological insulator、spin-orbit torque
BiSb topological insulator (TI) has attracted attention as a promising spin-orbit torque (SOT) material owing to its giant spin Hall effect and high electrical conductivity σ for ultrafast and ultralow power SOT-MRAM and SOT domain-wall memory. Although high crystal quality BiSb thin films have been studied so far on single crystalline substrates, such as GaAs(111), GaAs(001), sapphire(0001), and BaF_{2} (111), realizing high quality of BiSb with high spin Hall angle (SHA) and high σ on amorphous SiO_{x} is essential to realize realistic SOT spintronic devices.
In this work, we aim to realize BiSb TI thin films with SHA and high σ on amorphous SiO_{x} using oxide buffer layers and post annealing. We first deposited an oxide buffer layer and an optional oxide buffer layer on thermally oxidized Si/SiO_{x} substrates. The 1st oxide buffer layer is typically a 6 nm-thick TiO_{x} layer which prevents oxygen diffusion from the SiO_{x} layer to BiSb during high temperature annealing, while the optional 2nd oxide layer is typically TaO_{x}, both are deposited by reactive sputtering of a Ti/Ta target using Ar and O_{2} mixing gas. Next, we deposited a 10 nm-thick BiSb on top of the oxide layers. Finally, we deposited a 3 nm-thick Ti cap layer. The stack was then annealed at high temperature for 1 hour and cooled in ultrahigh vacuum to low temperature, after that we deposited the ferromagnetic (FM) multilayers for SOT evaluation. Here we used Pt/Co/Pt or Ta/CoFeB/MgO as the FM mutillayers. We confirmed the (012) orientation growth of BiSb by XRD on a sample with TiOx buffer and Pt/Co/Pt FM layers. By high temperature annealing, we can improve the BiSb conductivity up to 1.1 × 105 Ω-1 m-1 and achieve a relatively high SHA of θSH ~ 1.7 – 5. Our results show that utilizing oxide buffer layers and post-annealing is an effective way to achieve high performance BiSb on Si/SiOx substrates.
In this work, we aim to realize BiSb TI thin films with SHA and high σ on amorphous SiO_{x} using oxide buffer layers and post annealing. We first deposited an oxide buffer layer and an optional oxide buffer layer on thermally oxidized Si/SiO_{x} substrates. The 1st oxide buffer layer is typically a 6 nm-thick TiO_{x} layer which prevents oxygen diffusion from the SiO_{x} layer to BiSb during high temperature annealing, while the optional 2nd oxide layer is typically TaO_{x}, both are deposited by reactive sputtering of a Ti/Ta target using Ar and O_{2} mixing gas. Next, we deposited a 10 nm-thick BiSb on top of the oxide layers. Finally, we deposited a 3 nm-thick Ti cap layer. The stack was then annealed at high temperature for 1 hour and cooled in ultrahigh vacuum to low temperature, after that we deposited the ferromagnetic (FM) multilayers for SOT evaluation. Here we used Pt/Co/Pt or Ta/CoFeB/MgO as the FM mutillayers. We confirmed the (012) orientation growth of BiSb by XRD on a sample with TiOx buffer and Pt/Co/Pt FM layers. By high temperature annealing, we can improve the BiSb conductivity up to 1.1 × 105 Ω-1 m-1 and achieve a relatively high SHA of θSH ~ 1.7 – 5. Our results show that utilizing oxide buffer layers and post-annealing is an effective way to achieve high performance BiSb on Si/SiOx substrates.
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