MRI: Development of an Ultra-high Sensitivity Scanning SQUID Multi-Function Microscope for Nanoscale Magnetometry, Susceptometry, and Thermometry

技术进步越来越依赖于新材料的开发，这往往需要深入了解它们在纳米级的物理性质。仅靠传统的散装或非本地数量测量是不够的。必须开发出能够在纳米尺度上探测材料性质的新一代仪器。然而，在这些标度下，来自这些微小区域的信号(例如，电、磁或热)的强度很弱，因此这些仪器也必须非常灵敏。该项目支持基于非侵入式超导量子干涉器件(SQUID)传感器的低温扫描探针显微镜的开发，该传感器对磁和热特性都具有超高的灵敏度。该仪器中使用的特定纳米SQUID技术，即纳米吸管尖端的鱿鱼，可应用于广泛的系统。该仪器可以在超导、纳米磁学、自旋电子学、量子信息和计算、拓扑材料以及量子化的热传输和耗散机制方面进行材料研究。多功能扫描探针显微镜是科罗拉多大学丹佛和博尔德校区的教职员工和学生通过跨学科合作开发的。它的发展培养了一名全日制研究生和三名本科生，在两名高级教员和两名具有互补专业领域的高级工程人员的指导下，学习仪器、低温和多种其他物理和工程主题。该仪器是科罗拉多前沿的一套纳米光谱工具的一部分，该工具吸引了来自当地和全国各地的学者、国家实验室科学家和行业成员的不同用户基础。该项目开发了一种低温(300MK)扫描探针显微镜，在纳米级石英吸管的尖端加入了SQUID传感器，满足了了解当地磁性和热材料性质的关键需求。这种“SQUID-on-Tip”可用作磁强计、磁感度计和温度计，其空间分辨率高达50 nm，具有单电子自旋磁灵敏度和微开尔文热灵敏度，比其他探头的热灵敏度高出一个数量级。在一台仪器中结合这些功能，可以进行许多其他仪器无法进行的研究。这台新仪器支持的研究项目包括拓扑超导体、Majorana费米子、拓扑保护的磁孤子以及新型量子开关、人工工程热电、量子化热传输研究等。这个项目是发展中的，因为商业上没有类似的仪器可用。该项目的范围是实施SQUID-On-Tip传感器的制造技术，并将该传感器集成到使用干燥低温恒温器的超低温扫描探针显微镜中。传感器的制造需要一种新的真空沉积系统，该系统允许在低温冷却的石英纳米吸管上热蒸发超导薄膜。扫描探针显微镜将商业定位平台与SQUID-On-Tip传感器和相关电子设备集成在一起。该项目的范围包括使用磁性或超导弯曲器或用于显微镜验证的磁涡流的调试阶段。该项目的目标是为来自学术界、国家实验室和工业界的不同用户群提供对这种多功能仪器的协作访问。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Technological advances are increasingly dependent on the development of new materials, often requiring a deep understanding of their physical properties at the nanoscale. Traditional measurements of bulk or non-local quantities alone are insufficient. A new generation of instruments must be developed that can probe materials properties at nanometer length scales. However, at these scales, the strength of signals (e.g., electric, magnetic, or thermal) from these tiny regions is weak, so these instruments must also be extremely sensitive. This project supports development of a cryogenic scanning probe microscope based on a non-invasive superconducting quantum interference device (SQUID) sensor with ultra-high sensitivity to both magnetic and thermal properties. The specific nanoSQUID technology employed in this instrument, a SQUID at the tip of a nano-pipette, has application to a broad range of systems. The instrument enables materials research in superconductivity, nanomagnetism, spintronics, quantum information and computing, topological materials, and quantized thermal transport and dissipation mechanisms. The multi-function scanning probe microscope is developed through an interdisciplinary collaboration of faculty, staff, and students at the Denver and Boulder campuses of the University of Colorado. Its development trains a full-time graduate student and three undergraduate students in instrumentation, cryogenics, and multiple other physics and engineering topics under the mentorship of two senior faculty and two senior engineering staff with complementary areas of expertise. This instrument is part of a suite of nanospectroscopy tools in the Colorado Front Range that brings in a diverse user base of academics, national laboratory scientists, and industry members from the local area and across the country.This project develops a low-temperature (300 mK) scanning probe microscope incorporating a SQUID sensor on the tip of a nanoscale quartz pipette that meets a critical need in the understanding of local magnetic and thermal material properties. This "SQUID-on-Tip" operates as magnetometer, susceptometer, and thermometer with spatial resolution as good as 50 nm, single-electron-spin magnetic sensitivity, and micro-Kelvin thermal sensitivity, orders of magnitude beyond the thermal sensitivity of other probes. The combination of these capabilities in one instrument enables many studies that cannot be carried out by any other instrument. Research projects enabled by this new instrument include studies of topological superconductors, Majorana fermions, topologically protected magnetic solitons as well as novel quantum switches, artificially engineered thermoelectrics, studies of quantized thermal transport, and more. This project is developmental because no comparable instrument is available commercially. The project scope is to implement the fabrication technology of the SQUID-on-Tip sensor and to incorporate the sensor in an ultra-low-temperature scanning probe microscope utilizing a dry low-temperature cryostat. Fabrication of the sensor requires a novel vacuum deposition system that allows for thermal evaporation of a superconducting film on a cryogenically cooled quartz nano-pipette. The scanning probe microscope integrates commercial positioning stages with the SQUID-on-Tip sensor and associated electronics. The project scope includes a commissioning phase using magnetic or superconducting meanders, or magnetic vortices for microscope verification. The goal of this project is to provide collaborative access to this multi-function instrument to a diverse user base from academia, national laboratories, and industry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.