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: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=588026
• 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.

由于核衰变释放出高能粒子，所以放射性很容易被探测到。事实上，它最初是在照相胶片被这种粒子偶然曝光时发现的。现代电子探测器非常灵敏，甚至可以从几个放射性原子中检测出放射性，从而使“放射性示踪”技术成为可能，在这种技术中，用放射性原子标记的化学物质可以通过化学、物理和生物过程进行跟踪。这是医学成像技术的基础，如正电子发射断层扫描（PET）。在这里，放射性衰变仅仅报告了放射性标记物种的位置。然而，某些类型的放射性可以给出放射性探针原子的局部环境的更详细的图像，这是β探测核磁共振（ß-NMR）的基础，这是该提议所基于的技术。