Development of quasi-2D Si devices with large magnetoresistance

1)薄Si沟道中的自旋输运：我们在厚度范围为70 nm至25 nm的薄硅沟道上沉积了Fe/MgO。我们使用分子束外延生长Fe/MgO，和RHEED图案表明高质量的外延Fe/MgO。然后，我们制造的设备和测量自旋输运特性作为Si沟道厚度的函数。我们观察到明确的两端磁阻（2 T-MR）的所有设备。虽然随着Si沟道厚度的减小，观察到2 T-MR增加，但是Si沟道的电阻率随着沟道厚度的减小而增加。这使我们无法系统地解释结果，因为需要保持电阻率恒定以比较结果。2）用于自旋注入到Si中的新型隧道势垒：我们研究了作为新型隧道势垒的BaO在Si上的外延生长。BaO晶格与Si晶格的匹配比MgO更好。因此，更高质量的外延BaO可以在Si上获得，并且可能更适合作为Si自旋输运器件的隧道势垒。我们研究了BaO的不同生长温度，并找到了在Si上获得外延BaO的最佳生长条件。3）Si基自旋输运器件中2 T-MR的最佳接触电阻对于具有Si沟道和不同MgO厚度的Fe/MgO隧道接触的器件，确定了自旋输运器件中的2 T-MR。我们发现，最佳和缩放的2 T-MR的深刻影响的自旋极化与接触电阻的变化。研究结果发表在APL（2023）上。

1) Spin transport in thin Si channels:We have deposited Fe/MgO on thin silicon channels having thicknesses ranging from 70 nm to 25 nm. We used molecular beam epitaxy to grow Fe/MgO, and the RHEED patterns indicate high quality epitaxial Fe/MgO. We then fabricated devices and measured spin transport properties as a function of the Si channel thickness. We observed clear two-terminal magnetoresistance (2T-MR) for all the devices. Although an increase of the 2T-MR was observed as the Si channel thickness decreases, the resistivity of the Si channel increased with decreasing the channel thickness. This prevented us from interpreting the results in a systematic manner, as one need to keep the resistivity constant in order to compare the results.2) Novel tunnel barrier for spin injection into Si:We investigated the epitaxial growth of BaO on Si as a novel tunnel barrier. The BaO lattice matches that of Si better than MgO. Therefore, higher quality epitaxial BaO might be obtained on Si, and potentially be a better fit as a tunnel barrier for Si spin transport devices. We investigated different growth temperature for BaO and found the optimum growth conditions to obtain epitaxial BaO on Si.3) Optimum contact resistance for 2T-MR in Si-based spin transport devicesThe 2T-MR in spin transport devices was determined for devices with a Si channel and Fe/MgO tunnel contacts of varying MgO thickness. We showed that the optimum and scaling of the 2T-MR are profoundly affected by the variation of the spin polarization with contact resistance. The results were published in APL (2023).