[17a-D704-1~9] 10.3 スピンデバイス・磁気メモリ・ストレージ技術

▼ [17a-D704-9] Large magnetoresistance ratio in polycrystalline silicon vertical spin valve

〇(M2)Tatsuki Watanabe¹、Minori Goto^1,2,3、Ando Yuichiro⁴、Nomura Hikaru^1,2,3、Suzuki Yoshishige^1,2,3 (1.Osaka Univ.、2.CSRN Osaka Univ.、3.OTRI Osaka Univ.、4.Kyoto Univ.)

キーワード：magnetoresistance, vertical spin valve, magnetic tunnel junction

Spin metal-oxide-semiconductor field-effect transistors (spin-MOSFETs) are expected to be low-power-consumption electronic devices due to their nonvolatility. High magnetoresistance ratio (MR ratio) is required to realize spin MOSFETs. So far, lateral spin valves utilizing silicon as the channel (Si-LSVs) have been fabricated, and their MR ratios have been over 1%. In order to improve the MR ratio, the vertical spin valve (VSV), which can shorten the channel length, is desirable. The VSV utilizing germanium has been reported, but VSV utilizing silicon (Si-VSV) has not been reported. In addition, Si-VSV is a promising candidate since Si have high compatibility with conventional MOS technology and long spin lifetime. In this study, we fabricate Si-VSV and attempt to achieve high MR ratio. A multilayer film consisting of MgO(5)|Fe(30)|MgO(1.2)|Si(t_Si=0-5)|MgO(1.2)|Fe(10) |Co(5)|Au(10) (described by nm) was deposited on a single crystal MgO(001) substrate by molecular beam epitaxy. Here, MgO insulating layer is inserted at the Fe|Si junctions for efficient spin injection. The Si layer was grown at a substrate temperature of 550 °C, and the RHEED image shows that it forms polycrystalline. 6×7 μm² elliptical Si-VSVs were fabricated from the multilayer film by the combination of photolithography, Ar-ion milling, and lift-off methods. The magnetic field H was applied parallel to the film plane in [100] direction of Fe, and the MR ratio was calculated. We found that the MR ratio of 33.3% and 4.7% were obtained at t_Si = 0.19 nm and 0.74 nm, respectively.