NER: High-Bandwidth Scanning DC SQUID Susceptometer for Characterization of Nanomagnetic Structures and Phenomena

[210877]如果没有更快、更灵敏的表征工具来直接探测纳米级现象和材料结构，就无法开发用于量子计算和大容量存储器等应用的磁性器件。提出的工作目标是推进一种非侵入性，高灵敏度的技术-扫描超导量子干涉器件（SQUID）电纳测量的能力，用于纳米磁系统和现象的动态表征。首席研究员将通过两项创新来实现这一目标。首先，自旋灵敏度将从目前的技术水平（每Hz1/2有几千个电子自旋）提高到每Hz1/2有几十个自旋。这一改进将通过减少光学和电子束光刻工艺中的拾取环路尺寸以及利用超低噪声直流SQUID工艺来实现。其次，通过使用直流SQUID系列阵列放大器作为直流SQUID电纳计的前置放大器，将带宽从目前最先进的几十kHz提高到几十MHz。该器件将具有在4 K和20 mK下的通量灵敏度和带宽。该器件将在4 K下有许多应用，尽管在20 mK下运行对于电子系统中量子退相干机制的研究至关重要。本科生将与合作者实验室的研究生一起工作，通过对单个钴纳米磁球进行成像，表征设备的自旋灵敏度及其在真实扫描条件下的性能，这些球体的直径范围为3纳米至10纳米，磁矩范围为数十到数万个电子自旋。此外，将使用一个SQUID电纳计对另一个相同的设备成像，以定量表征设备产生的噪声。该项目的科学重点是生产将在纳米级结构、新现象和量子控制领域应用的传感器，并使用这些传感器对单个钴纳米磁铁的静态和动态特性进行成像。将高灵敏度、高带宽SQUID电纳计集成到扫描平台中，将显著增加可研究系统的数量和种类，减少周转时间，增加单次实验可研究的样品数量。因此，此计画的成功实现将有助于奈米装置和系统架构的进步。这个项目的另一个好处是丹佛大学（PI的机构）和斯坦福大学（合作者的机构）的教育效益，这是丹佛大学本科生和斯坦福大学研究生之间合作的结果。

0210877HuberNanomagnetic devices for applications such as quantum computing and high-capacity memory cannot be developed without faster, more sensitive characterization tools to directly probe phenomena and material structures at the nanoscale. The objective of the proposed work is to advance the capability of a non-invasive, high-sensitivity technique-scanning superconducting quantum interference device (SQUID) susceptometry for the dynamic characterization of nanomagnetic systems and phenomena.The principal investigator will achieve this objective through two innovations. First, spin sensitivity will be improved from the current state of the art, a few thousand electron spins per Hz1/2, to a few tens of spins per Hz1/2. This improvement will be accomplished by reduction of pickup loop dimensions in a combined optical and electron-beam lithography process and by utilizing an ultra-low-noise dc SQUID process. Second, bandwidth will be increased from the current state of the art, tens of kHz, to tens of MHz by the use of dc SQUID series array amplifiers as preamplifiers for the dc SQUID susceptometer.The devices will be characterized for flux sensitivity and bandwidth at 4 K and 20 mK. The devices will have many applications at 4 K, although operation at 20 mK will be essential for the study of quantum decoherence mechanisms in electronic systems. Undergraduates, working with graduate students in the collaborator's laboratory, will characterize the spin sensitivity of the devices and their performance under realisticscanning conditions by imaging individual cobalt nanomagnetic spheres of controlled diameters ranging from 3 nm to 10 nm and magnetic moments ranging from tens to tens of thousands of electron spins. Further, one SQUID susceptometer will be used to image a second, identical device to quantitatively characterize the noise generated by the devices.The scientific emphasis of this project is to produce sensors that will have applications in the area of nanoscale structures, novel phenomena, and quantum control and to use these sensors image both static and dynamic properties of individual cobalt nanomagnets. Integration of a high-sensitivity, high-bandwidth SQUID susceptometer into a scanning platform will significantly increase the number and kind of systems that can be studied, decrease turn-around time, and increase the number of samples that can be studied in ansingle experiment. Thus, the successful realization of this project will contribute to advances in nanoscale devices and system architecture. An added benefit of this project will be the educational benefits at both CU-Denver (PI's institution) and Stanford University (collaborator's institution) resulting from the collaboration between CU-Denver undergraduate students and Stanford graduate students.