Single nanowire spin-valve based infrared photodetctors and equality bit comparators

红外线是人眼看不见的。它通常是用半导体探测器检测的，在红外线照射下，半导体探测器的电阻会发生变化。然而，在室温下，电阻的相对变化很小，这就需要用液氮来冷却探测器。在这项研究中，将展示一种新型的探测器，它依靠光通过影响携带电流的电子的量子力学自旋属性来改变探测器的电阻。利用这种检测原理，有可能在室温下使探测器中的电阻变化更大。常温红外探测器被用于夜视、法医学、天文学、导弹防御、汽车防撞系统和监测全球变暖，仅举几例。比特比较器是比较信息的两个数字(二进制)比特并根据这两个比特相同还是不同来做出是/否决定的电子设备。它们是电子电路的重要组成部分，通常是用晶体管实现的，一旦做出决定，晶体管就不能记住决定。利用自旋相关特性并使用磁性器件而不是晶体管的比较器可以记住这个决定，也可以使用更少的能量。记忆能力使人们有可能建造速度更快、容错性更强的高级数字电子电路。在这项研究中，将演示这样一个比较器。这个项目还将把研究与研究生和本科教育结合起来，通过院长的早期研究倡议计划将K-12扩展，并通过里士满少数民族工程合作伙伴关系来丰富少数族裔。这是一个制造和展示两个在室温下工作的新型自旋电子器件的建议-一个红外光电探测器和一个可重新配置的比特比较器。它们将被制造成直径为10 nm和50 nm的纳米线自旋阀，带有InSb间隔物和钴触点。在InSb隔离层中，室温下只有一个电子子带被占据。实验室的初步实验表明，在这些纳米线中，电子的主要自旋弛豫机制--即D‘yakonov-Perel机制--由于单子带占据而被消除，导致自旋弛豫时间增加数倍。研究还表明，自旋弛豫时间可以用红外光进行调制，这将被用来制作光电探测器。这种光电探测器原则上可以表现出接近于零的暗电流、巨大的明暗对比度和非常高的探测率，这些都是由于声子激发而总是避开传统光电探测器的。我们实验室最近证明了用电生应变来控制纳米磁体的磁化状态。这一特性将被用来建造具有前所未有的能效的可重新配置的比特比较器。这些比特比较器是非易失性的，因为它们结合了磁性元件，因此比较结果可以无限地存储在比较器中。这些器件将通过纳米线的电化学自组装、用于图案化铁磁接触的电子束光刻和用于在一对接触之间捕获单个纳米线的介电来制造，以实现光电探测器和比特比较器。

Infrared light is not visible to the human eye. It is usually detected with semiconductor detectors which exhibit a change in their electrical resistance under infrared illumination. The relative change in resistance at room temperature is, however, quite small, which necessitates cooling the detector with liquid nitrogen. In this research, a novel detector will be demonstrated, which relies on light changing the detector's resistance by affecting the quantum mechanical spin properties of the electrons that carry current. With this principle of detection, it is possible to make the resistance change in the detector much larger at room temperature. Room temperature infrared detectors are used in night vision, forensic science, astronomy, missile defense, car-collision avoidance systems and monitoring of global warming, to name a few. Bit comparators are electronic devices that compare two digital (binary) bits of information and render a yes/no decision based on whether the two bits are the same or different. They are important ingredients of electronic circuits and are typically implemented with transistors which cannot remember the decision once the decision has been rendered. A comparator that exploits spin dependent properties and uses magnetic devices instead of transistors can remember the decision and also use less energy. The ability to remember makes it possible to build superior digital electronic circuits that are faster and more error-resilient. In this research, such a comparator will be demonstrated. This project will also integrate research with graduate and undergraduate education, K-12 outreach through the Dean's Early Research Initiative program, and minority enrichment through the Richmond Minorities in Engineering Partnership.This is a proposal to fabricate and demonstrate two novel spintronic devices - an infrared photodetector and a reconfigurable bit comparator - working at room temperature. They will be fabricated with 10- and 50-nm diameter nanowire spin valves with InSb spacer and cobalt contacts. In the InSb spacer, only a single electronic subband is occupied at room temperature. Preliminary experiments in the lab have shown that in these nanowires, the major spin relaxation mechanism of electrons - namely the D'yakonov-Perel' mechanism - is eliminated owing to single subband occupancy, resulting in several-fold increase in the spin relaxation time. It has also been shown that the spin relaxation time can be modulated with infrared light, which will be exploited to build the photodetector. Such a photodetector can, in principle, exhibit near-zero dark current, giant light-to-dark contrast ratio and very high detectivity which always elude conventional photo-detectors because of phonon excitations. Controlling the magnetization state of a nanomagnet with electrically generated strain has been recently demonstrated in our lab. That property will be leveraged to build the reconfigurable bit comparator with unprecedented energy efficiency. These bit comparators are "non-volatile" since they incorporate magnetic elements and hence the result of the comparison can be stored indefinitely in the comparator. The devices will be fabricated with electrochemical self-assembly of nanowires, electron-beam lithography for patterning ferromagnetic contacts, and dielectrophoresis for capturing a single nanowire between a pair of contacts to implement the photodetector and bit comparator.