Yamashita N, Lee S, Ohshima R, Shigematsu E, Koike H, Suzuki Y, Miwa S, Goto M, Ando Y, Shiraishi M
Department of Electronic Science and Engineering, Kyoto University, Kyoto, Kyoto, 615-8510, Japan.
Advanced Products Development Center, TDK Corporation, Ichikawa, Chiba, 272-8558, Japan.
Sci Rep. 2021 May 19;11(1):10583. doi: 10.1038/s41598-021-90114-9.
Improvement in the thermal tolerance of Si-based spin devices is realized by employing thermally stable nonmagnetic (NM) electrodes. For Au/Ta/Al electrodes, intermixing between Al atoms and Au atoms occurs at approximately 300 °C, resulting in the formation of a Au/Si interface. The Au-Si liquid phase is formed and diffuses mainly along an in-plane direction between the Si and AlN capping layers, eventually breaking the MgO layer of the ferromagnetic (FM) metal/MgO electrodes, which is located 7 µm away from the NM electrodes. By changing the layer structure of the NM electrode from Au/Ta/Al to Au/Ta, the thermal tolerance is clearly enhanced. Clear spin transport signals are obtained even after annealing at 400 °C. To investigate the effects of Mg insertion in FM electrodes on thermal tolerance, we also compare the thermal tolerance among Fe/Co/MgO, Fe/Co/Mg/MgO and Fe/Co/MgO/Mg contacts. Although a highly efficient spin injection has been reported by insertion of a thin Mg layer below or above the MgO layer, these thermal tolerances decrease obviously.
通过采用热稳定的非磁性（NM）电极，实现了硅基自旋器件热耐受性的提高。对于金/钽/铝电极，铝原子和金原子在约300℃时发生混合，导致形成金/硅界面。形成了金-硅液相，主要沿硅和氮化铝覆盖层之间的面内方向扩散，最终破坏了距NM电极7微米远的铁磁（FM）金属/氧化镁电极的氧化镁层。通过将NM电极的层结构从金/钽/铝改变为金/钽，热耐受性明显增强。即使在400℃退火后也能获得清晰的自旋输运信号。为了研究在FM电极中插入镁对热耐受性的影响，我们还比较了铁/钴/氧化镁、铁/钴/镁/氧化镁和铁/钴/氧化镁/镁接触之间的热耐受性。尽管通过在氧化镁层下方或上方插入薄镁层已报道了高效的自旋注入，但这些热耐受性明显降低。
