Development of Wideband Scanning Superconducting Quantum Interference Device Susceptometers for Nanomagnetic Materials Research and Education

用于纳米磁性材料研究和教育的宽带扫描超导量子干涉装置磁感受计的开发

• 批准号: 0216470
• 负责人: Martin Huber
• 金额: $ 22万
• 依托单位: University of Colorado at Denver-Downtown Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-15 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0216470&HistoricalAwards=false
• 关键词: Development; Wideband; Scanning; Superconducting; Quantum

Nanomagnetic 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 this 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 materials, systems, and phenomena. The principal investigator achieves this objective through two innovations. First, spin sensitivity is 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 is 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 is 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 are characterized for flux sensitivity and bandwidth at 300 mK and 20 mK. Operation at 300 mK is necessary for the e-beam defined Al pick-up loops to become superconducting, and operation at 20 mK is essential for the study of quantum decoherence mechanisms in electronic systems. Undergraduates, working with graduate students in the collaborator's laboratory, characterize the spin sensitivity of the devices and their performance under realistic scanning 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 is 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 have applications in the area of nanoscale structures, novel phenomena, and quantum control and to use these sensors to image both static and dynamic properties of individual cobalt nanomagnets. Integration of a high-sensitivity, high-bandwidth SQUID susceptometer into a scanning platform significantly increases the number and kind of systems that can be studied, decreases the turn-around time, and increases the number of samples that can be studied in a single experiment. Thus, this project contributes to advances in nanoscale materials, devices and system architecture. An added benefit of this project is 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.

如果没有更快，更敏感的表征工具，可以开发用于量子计算和高容量记忆等应用的纳米磁性设备，以直接探测纳米级的现象和材料结构。这项工作的目的是提高非侵入性，高敏化技术，扫描超导量子干扰装置（squid）苏联苏联的能力，用于纳米磁物质，系统和现象的动态表征。主要研究人员通过两项创新实现了这一目标。首先，自旋灵敏度从目前的技术状态提高，每Hz1/2每千次电子旋转到每Hz1/2的几十旋转。通过在组合的光学和电子光刻过程中以及使用超低噪声DC鱿鱼过程中降低拾音器循环尺寸来实现此改进。其次，通过使用DC Squid系列阵列放大器作为DC Squid启动器的前置放大器，从数十个KHz的当前状态（数十KHz）增加了带宽。 这些设备的特征在于300 mk和20 mk的通量灵敏度和带宽。在300 MK处的操作对于电子束定义的Al拾取环成为超导所必需的，并且在20 MK处的操作对于研究电子系统中的量子去碳机制至关重要。本科生与研究生合作在合作者的实验室中工作，表征了设备的旋转敏感性及其在逼真的扫描条件下的旋转敏感性，它通过对受控直径的单个钴纳米磁球体进行成像，范围为3 nm至10 nm，磁性力矩从3 nm到10 nm，磁性力矩从数量到数千到数千的电子旋转。此外，一个鱿鱼启示仪用于对第二个相同的设备进行映像，以定量地表征设备产生的噪声。该项目的科学重点是生成在纳米级结构，新现象和量子控制区域中应用的传感器，并使用这些传感器来对单个钴纳米磁体的静态和动态特性进行成像。将高敏，高带宽鱿鱼启示仪集成到扫描平台中会显着增加可以研究的系统的数量和种类，减少转折时间，并增加单个实验中可以研究的样品数量。因此，该项目有助于纳米级材料，设备和系统体系结构的进步。该项目的额外好处是Cu-denver（PI的机构）和斯坦福大学（合作者机构）的教育益处，这是由于Cu-denver本科生与斯坦福大学的研究生之间的合作。