Development of quasi-2D Si devices with large magnetoresistance

1)薄硅通道中的自旋输运：我们在厚度从70 nm到25 nm的薄硅通道上沉积了Fe/MgO。我们采用分子束外延法生长Fe/MgO， RHEED模式显示出高质量的外延Fe/MgO。然后我们制作了器件并测量了自旋输运特性作为Si通道厚度的函数。我们观察到所有器件明显的双端磁阻（2T-MR）。随着硅沟道厚度的减小，硅沟道的2T-MR增大，而硅沟道的电阻率随着硅沟道厚度的减小而增大。这使我们无法以系统的方式解释结果，因为我们需要保持电阻率恒定才能比较结果。2)新型的自旋注入隧道势垒：我们研究了BaO在Si上的外延生长作为一种新型的隧道势垒。BaO晶格与Si晶格的匹配度高于MgO晶格。因此，可以在Si上获得更高质量的外延BaO，并且可能更适合作为Si自旋输运器件的隧道势垒。3)硅基自旋输运器件中2T-MR的最佳接触电阻我们确定了具有不同MgO厚度的Si通道和Fe/MgO隧道接触的自旋输运器件中的2T-MR。结果表明，自旋极化随接触电阻的变化对2T-MR的最佳化和标度有深刻的影响。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).