Development and Application of Depth-Resolved beta-Detected Nuclear Magnetic Resonance to electronic, ionic and molecular phenomena in the Solid State

深度分辨 β 检测核磁共振技术在固态电子、离子和分子现象中的开发和应用

• 批准号: RGPIN-2014-04806
• 负责人: MacFarlane, William
• 金额: $ 2.48万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=632308
• 关键词: Development; Application; Depth; Resolved; beta

Radioactivity is easy to detect since the nuclear decay emits high energy particles. In fact, it was first discovered by the accidental exposure of photographic film by such particles. Modern electronic detectors are extremely sensitive and can detect radioactivity from even a few radioactive atoms, enabling *radiotracer* techniques, where a chemical species, tagged with a radioactive atom, is followed through chemical, physical and biological processes. This is the basis for medical imaging techniques, such as Positron Emission Tomography (PET). Here, radioactive decay merely reports the location of the radiolabelled species. Certain kinds of radioactivity, however, can give a much more detailed picture of the local environment of the radioactive probe atom, a property that is the basis of beta-detected nuclear magnetic resonance (ß-NMR), the technique on which this proposal is based.Detection by radioactive beta decay makes ß-NMR an exceptionally sensitive means to study the local atomic properties of materials. However, it is complicated to carry out such measurements. The radioactive ions used necessarily have very short halflives on the order of seconds or less, so they must be made immediately before being used. The ISAC facility at TRIUMF, Canada's national lab for nuclear and particle physics, located at UBC in Vancouver, provides beams of such short-lived radioactive ions. Our main probe is a heavy isotope of Li, 8Li (halflife 848 milliseconds). Only a few other labs in the world can make such beams but more are being constructed. Our efforts at TRIUMF lead the world in the development of ß-NMR, and based on our success, other labs are now looking to follow.The difficulty and complexity of such measurements means that we restrict the use of ß-NMR to problems that it is uniquely capable of addressing. A key capability of ß-NMR is the ability to implant the radioactive probe at different depths in a material. While there are many powerful probes of the *surface*, the top atomic layer, of a material, there are very few that can study materials as a function of depth below a surface. Our main motivation then is to use ß-NMR to study surface and interface effects that give rise to poorly understood depth-dependent phenomena in solids on depth scales of a few nanometers (1 billionth of a meter) to a few hundred nm, an important range for modern electronic technology.Interfaces between dissimilar materials like metal/semiconductor, metal/polymer or electrode/electrolyte are crucial to all sorts of devices. As devices are further miniaturized towards the limit of *nanotechnology*, every atom in the device is near an interface. However, interface effects are not well understood. This proposal aims to study interface problems using the depth-resolved power of ß-NMR.Specifically, we will study new materials that may be the basis for next generation technologies, e.g. topological insulators and correlated electronic conductors that have unique electromagnetic properties for new types of devices that may sidestep fundamental limitations of conventional semiconductor devices. We will study nanostructured catalytic metals and interface effects in Li ion conductors, with the aim of a better fundamental understanding and enable new generations of battery technology, crucial for the increasing energy demands of portable devices. We will also explore new applications of ß-NMR to polymers and certain problems in biochemistry that cannot be addressed in other ways.Canada will benefit by leading the world in advanced materials research with outcomes that lead to a better fundamental understanding that will afford optimization of current technologies as well as development of radically new ones.

由于核衰变会释放出高能粒子，因此放射性很容易被检测到。事实上，它是通过这种颗粒对照相胶片的意外曝光而首次发现的。现代电子探测器极其灵敏，甚至可以检测到一些放射性原子的放射性，从而实现了“放射性示踪剂”技术，其中用放射性原子标记的化学物质通过化学、物理和生物过程进行跟踪。这是医学成像技术的基础，例如正电子发射断层扫描 (PET)。在这里，放射性衰变仅报告放射性标记物质的位置。然而，某些类型的放射性可以更详细地描述放射性探针原子的局部环境，这种特性是 β 检测核磁共振 (ß-NMR) 的基础，该技术也是本提案的基础。放射性 β 衰变检测使 ß-NMR 成为研究材料局部原子特性的异常灵敏的手段。然而，进行此类测量很复杂。所使用的放射性离子必然具有非常短的半衰期，大约为数秒或更短，因此必须在使用前立即制备它们。位于温哥华 UBC 的加拿大国家核与粒子物理实验室 TRIUMF 的 ISAC 设施提供这种短寿命放射性离子束。我们的主要探测器是 Li 的重同位素 8Li（半衰期 848 毫秒）。世界上只有少数其他实验室可以制造这种梁，但更多的实验室正在建造中。我们在 TRIUMF 的努力在 ß-NMR 的开发方面处于世界领先地位，基于我们的成功，其他实验室现在正在寻求效仿。此类测量的难度和复杂性意味着我们将 ß-NMR 的使用限制在它独特能够解决的问题上。 ß-NMR 的一项关键功能是能够将放射性探针植入材料的不同深度。虽然有许多针对材料的“表面”（顶部原子层）的强大探针，但很少有能够将材料作为表面以下深度的函数来研究的。我们的主要动机是使用 ß-NMR 来研究表面和界面效应，这些效应会在几纳米（十亿分之一米）到几百纳米的深度尺度上引起人们知之甚少的固体深度相关现象，这是现代电子技术的一个重要范围。金属/半导体、金属/聚合物或电极/电解质等不同材料之间的界面对于各种设备都至关重要。随着设备进一步小型化，达到*纳米技术*的极限，设备中的每个原子都靠近一个界面。然而，界面效应尚不清楚。该提案旨在利用 ß-NMR 的深度分辨能力来研究界面问题。具体来说，我们将研究可能成为下一代技术基础的新材料，例如拓扑绝缘体和相关电子导体具有独特的电磁特性，适用于新型器件，可以避开传统半导体器件的基本限制。我们将研究锂离子导体中的纳米结构催化金属和界面效应，目的是更好地了解基础知识并实现新一代电池技术，这对于便携式设备不断增长的能源需求至关重要。我们还将探索 β-NMR 在聚合物中的新应用以及生物化学中无法通过其他方式解决的某些问题。加拿大将受益于先进材料研究领域的世界领先地位，其成果将带来更好的基本了解，从而优化现有技术并开发全新技术。