Naval Research Laboratory, Washington, DC 20375, USA.
Nat Nanotechnol. 2012 Nov;7(11):737-42. doi: 10.1038/nnano.2012.161. Epub 2012 Sep 30.
Spin manipulation in a semiconductor offers a new paradigm for device operation beyond Moore's law. Ferromagnetic metals are ideal contacts for spin injection and detection, but the intervening tunnel barrier required to accommodate the large difference in conductivity introduces defects, trapped charge and material interdiffusion, which severely compromise performance. Here, we show that single-layer graphene successfully circumvents the classic issue of conductivity mismatch between a metal and a semiconductor for electrical spin injection and detection, providing a highly uniform, chemically inert and thermally robust tunnel barrier. We demonstrate electrical generation and detection of spin accumulation in silicon above room temperature, and show that the contact resistance-area products are two to three orders of magnitude lower than those achieved with oxide tunnel barriers on silicon substrates with identical doping levels. Our results identify a new route to low resistance-area product spin-polarized contacts, a key requirement for semiconductor spintronic devices that rely on two-terminal magnetoresistance, including spin-based transistors, logic and memory.
半导体中的自旋操控为超越摩尔定律的器件操作提供了新的范例。铁磁金属是自旋注入和检测的理想触点，但为了适应电导率的巨大差异而需要的中间隧道势垒会引入缺陷、俘获电荷和材料互扩散，从而严重影响性能。在这里，我们表明单层石墨烯成功地规避了金属和半导体之间电导率不匹配的经典问题，为电自旋注入和检测提供了一个高度均匀、化学惰性和热稳定的隧道势垒。我们证明了在室温以上硅中自旋积累的电产生和检测，并表明与具有相同掺杂水平的硅衬底上的氧化物隧道势垒相比，接触电阻-面积乘积低了两到三个数量级。我们的结果确定了低电阻-面积乘积自旋极化接触的新途径，这是依赖于两端磁电阻的半导体自旋电子器件的关键要求，包括基于自旋的晶体管、逻辑和存储器。
