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

红外光是人眼看不见的。它通常是用半导体探测器来检测的，在红外照射下，它们的电阻会发生变化。然而，在室温下电阻的相对变化非常小，这就需要用液氮冷却探测器。在这项研究中，将展示一种新型探测器，它依赖于光通过影响携带电流的电子的量子力学自旋特性来改变探测器的电阻。利用这种检测原理，可以使探测器在室温下的电阻变化大得多。室温红外探测器用于夜视、法医科学、天文学、导弹防御、汽车防撞系统和全球变暖监测等领域。比特比较器是一种电子设备，它比较两个数字（二进制）比特信息，并根据这两个比特是相同还是不同，给出是/否的决定。它们是电子电路的重要组成部分，通常由晶体管实现，一旦做出决定，晶体管就不能记住决定。一种利用自旋相关特性并使用磁性器件代替晶体管的比较器可以记住这个决定，而且能耗更低。记忆的能力使得制造速度更快、容错能力更强的高级数字电子电路成为可能。在本研究中，将演示这样一个比较器。该项目还将整合研究生和本科教育的研究，通过院长早期研究倡议计划的K-12外展，以及通过里士满少数民族工程合作伙伴关系的少数民族丰富。这是一个制造和演示两种新型自旋电子器件-红外光电探测器和可重构位比较器-在室温下工作的建议。它们将由直径为10和50纳米的纳米线自旋阀制造，带有InSb间隔器和钴触点。在InSb间隔器中，在室温下只有一个电子子带被占用。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-由于单子带占用而被消除，导致自旋弛豫时间增加了几倍。研究还表明，自旋弛豫时间可以用红外光调制，这将用于构建光电探测器。这种光电探测器在原理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，而传统的光电探测器由于声子激发而无法做到这一点。利用电应变控制纳米磁铁的磁化状态最近在我们的实验室得到了证实。该特性将用于构建具有前所未有的能效的可重构位比较器。这些位比较器是“非易失性”的，因为它们包含磁性元件，因此比较的结果可以无限期地存储在比较器中。该器件将采用纳米线的电化学自组装、用于绘制铁磁触点图形的电子束光刻和用于捕获一对触点之间的单个纳米线的介电电泳来制造，以实现光电探测器和位比较器。

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.