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

红外光是人眼不可见的。它通常是用半导体探测器来检测的，半导体探测器在红外线照射下表现出电阻的变化。然而，在室温下电阻的相对变化非常小，这需要用液氮冷却检测器。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，可以使检测器中的电阻变化在室温下大得多。室温红外探测器用于夜视，法医学，天文学，导弹防御，汽车防撞系统和全球变暖监测，仅举几例。 位比较器是比较两个数字（二进制）信息位并基于这两个位是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，通常用晶体管实现，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决定，并且使用更少的能量。记忆的能力使人们有可能建立更快、更能容错的上级数字电子电路。在本研究中，将演示这样的比较器。 该项目还将研究与研究生和本科生教育，K-12通过院长的早期研究计划的推广，并通过工程合作伙伴里士满少数民族丰富。这是一个建议，制造和演示两个新的自旋电子器件-红外光电探测器和可重构位比较器-在室温下工作。它们将与10和50纳米直径的纳米线自旋阀与InSb间隔和钴接触。在室温下，只有一个单一的电子子带被占用的InSb间隔。实验室中的初步实验表明，在这些纳米线中，电子的主要自旋弛豫机制-即D 'yakonov-Perel'机制-由于单个子带占用而被消除，导致自旋弛豫时间增加数倍。它还表明，自旋弛豫时间可以调制与红外光，这将被用来建立光电探测器。 这样的光电探测器，在原则上，可以表现出接近零的暗电流，巨大的明暗对比度和非常高的探测率，总是逃避传统的光电探测器，因为声子激发。最近我们的实验室证明了利用电产生的应变控制纳米磁体的磁化状态。该属性将被利用来构建具有前所未有的能量效率的可重构位比较器。这些位比较器是“非易失性”的，因为它们包含磁性元件，因此比较结果可以无限期地存储在比较器中。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捕获一对接触之间的单个纳米线以实现光电检测器和位比较器的介电泳来制造。

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.