SHF: Small: Pipelined and wireless ultra-low power straintronics: An acoustically clocked combinational and sequential nanomagnetic architecture

具有两个稳定磁化取向的椭圆形单畴纳米磁体作为逻辑开关比传统晶体管能效高得多。然而，用来切换它们的方法也必须是节能的，以便建立超低功率的纳米磁逻辑和存储范例。理论上已经证明，使用多铁性(磁致伸缩-压电)纳米磁体，其磁化强度可以随着压电层上施加的微小静电势产生的应变而反转，从而产生了一种非常节能的开关方案。与其他纳米磁开关方案相比，在~1 GHz的时钟频率下，开关/时钟电路的功耗降低了四个数量级。虽然这很吸引人，但纳米磁逻辑链的一个不吸引人的特点是，为了建立流水线结构并因此保持可接受的比特传输速率，每个磁体必须单独计时。这就需要用一根接触线来接触每个磁体，这就带来了巨大的光刻负担。PI建议通过设计和制造一种新的计时声学方案来完全克服这一问题，该方案允许流水线，同时不需要接触到每个磁铁，从而完全减轻了光刻负担。表面声波(SAW)在衬底中发射，并随着周期性放置质量而减速，只要磁体之间的间距是SAW？S波长的四分之一，就会以正确的比特传输顺序在磁体阵列中产生应变。采用这种方案，在室温条件下，栅极工作时的能量消耗可以非常低。该项目将：(I)设计基于声控磁致伸缩纳米磁铁作为逻辑开关的组合和时序逻辑，并使用随机Landau-Lifshitz-Gilbert(LLG)方程进行广泛的模拟，以了解和优化存在热噪声的可靠性和容错性；(Ii)实验演示流水线单向逻辑流程；以及(Iii)开发表面声波(SAW)应力下纳米磁铁开关动力学的全面耦合模型。这项研究将产生一种新的计算模式，其惊人的能源效率与非常少的光刻负担相结合，可以生产出廉价、高产量和极低功耗的处理器。这样的处理器消耗的能源非常少，可以利用从环境中获得的能量来运行。这可能会带来迄今无法想象的应用，比如仅由患者身体运动提供动力的医学植入处理器，或者由风或交通引起的振动提供动力的监测桥梁和建筑物结构健康的处理器。将这项研究与教育和指导相结合，将产生传统的培训活动，如指导两名博士生，他们将获得先进纳米制造、纳米表征和建模方面的多学科技能，以及将由皮？S博士生指导的声表面波器件和磁致伸缩纳米磁体纳米制造的本科生项目。其他创新的外展计划将包括通过数学科学创新中心(MSIC)为高中生举办纳米磁铁和计算研讨会，并通过VCU里士满工程少数民族地区计划(RAPME)在夏季接待代表不足的K-12学生，将多样性纳入外展计划。这些学生将在监督下进行纳米光刻，并学习他们用MFM创建的磁性结构。

Elliptical single-domain nanomagnets with two stable magnetization orientations are far more energy-efficient as logic switches than traditional transistors. However, the method employed to switch them must be energy-efficient as well in order to build ultra-low-power nanomagnetic logic and memory paradigms. It has been theoretically shown that using multiferroic (magnetostrictive-piezoelectric) nanomagnets, whose magnetization can be flipped with strain generated by a tiny electrostatic potential applied across the piezoelectric layer, results in a remarkably energy-efficient switching scheme. It reduces the dissipation in the switching/clocking circuit by four orders of magnitude at a clock rate of ~ 1 GHz compared to other nanomagnet switching schemes. While this is attractive, an unattractive trait of nanomagnetic logic chains is that in order to build a pipelined architecture and hence retain an acceptable bit transfer rate, each magnet must be clocked individually. This necessitates contacting each magnetic with a contact line, which imposes a Herculean lithographic burden. The PIs propose to overcome this problem completely by designing and fabricating a novel acoustic scheme for clocking that allows pipelining and at the same time does not require contacts to every magnet, thereby completely lifting the lithography burden. A surface acoustic wave (SAW) launched in the substrate, and slowed down with periodically placed masses, generates strain in an array of magnets in the correct sequence for bit transfer, as long as the spacing between the magnets is one quarter of the SAW?s wavelength. With this scheme, the energy dissipation in a gate operation at room temperature can be very low. This project will: (i) design combinational and sequential logic based on acoustically clocked magnetostrictive nanomagnets acting as logic switches, as well as perform extensive simulations using the stochastic Landau-Lifshitz-Gilbert (LLG) equation to understand and optimize reliability and fault tolerance in the presence of thermal noise; (ii) experimentally demonstrate pipelined unidirectional logic flow, and (iii) develop comprehensive coupled models for the switching dynamics of nanomagnets stressed by surface acoustic wave (SAW). This research will result in a novel computational paradigm whose astonishing energy efficiency combined with very little lithographic burden could enable the production of cheap, high yield and extremely low power processors. Such processors would consume so little energy that they can be run off the energy harvested from the environment. This could open up hitherto unimaginable applications such as medically implanted processors powered only by the motion of the patient's body, or processors that monitor the structural health of bridges and buildings while being powered by vibrations caused by wind or traffic. Integration of this research with education and mentoring will result in traditional training activities such as guiding two doctoral students who will gain multidisciplinary skills in advanced nanofabrication, nanocharacterization and modeling, as well as undergraduate projects on SAW devices and nanofabrication of magnetostrictive nanomagnets that will be mentored by the PI and co-PI?s doctoral students. Other innovative outreach programs will include holding workshops on nanomagnets and computing for high school students through the Math Science Innovation Center (MSIC) and incorporating diversity into outreach programs by hosting under-represented K-12 students in summer with the help of VCUs Richmond Area Program for Minorities in Engineering (RAPME) program. These students will perform nanolithography under supervision and study the magnetic structures they create with MFM.