Highfield ESR using integrated CMOS LC tank oscillator as detectors

基于电子自旋共振(ESR)效应的方法是医学以及自然科学和材料科学中最强大的分析技术之一。它们能够研究顺磁物种的结构、动力学和空间分布。与基于核磁共振的方法相比，由于平衡磁化强度更大，基于ESR的技术表现出更好的自旋敏感性，使其成为现代生命科学应用中分析质量有限的样品的良好候选者。尽管利用许多不同的物理原理来检测ESR现象是可能的，其中一些表现出显著更好的自旋敏感性，但感应检测由于其非侵入性和与所有生物样品的完全兼容，是迄今为止最通用的ESR检测方法。基于这一事实，该研究项目的目标是进一步开发和改进一种新型的电感ESR频率敏感检测方法，该方法将使自旋灵敏度提高几个数量级。该频率敏感检测方法使用全集成LC坦克振荡器作为传感器。与标准电感ESR检测相比，使用全集成振荡器作为检测器有三个主要优势：第一，全集成CMOS检测器提供了一种优雅的探测器小型化方法，提供了本质上更好的自旋灵敏度。接下来，在给定的技术中，振荡器可以被设计成与例如低噪声放大器相比具有显著更高的工作频率。由于可实现的自旋灵敏度与工作频率的平方成正比，这是基于振荡器的检测的最大优势。最后，基于振荡器的检测不需要昂贵的外部射频源来产生B1场，因为线圈既检测信号又产生激发自旋系综的RF场。在该项目的框架内，我们计划设计用于Q-V和W波段工作的全集成的CMOSLC水槽振荡器，并使用基于ESR的方法验证其自旋灵敏度。通过这种方式，我们预计将获得大约106自旋/G/赫兹^(1/2)(300K)和104自旋/G/赫兹^(1/2)(4K)的自旋灵敏度，将最先进的技术提高大约两个数量级。

Methods based on the electron spin resonance (ESR) effect are amongst the most powerful analytical techniques in medicine as well as in the natural and material sciences. They enable to study the structure, dynamics and spatial distribution of paramagnetic species. Compared to nuclear magnetic resonance (NMR) based methods, due to the larger equilibrium magnetization, ESR based techniques display a significantly better spin sensitivity, rendering them a good candidate for the analysis of mass-limited samples in modern life science applications.Despite the possibility of detecting the ESR phenomenon with many different physical principles, some of them displaying significantly better spin sensitivities, inductive detection, due to its non-invasive nature and its full compatibility with all biological samples, is by far the most versatile ESR detection method.Building upon this fact, the goal of the proposed research project is to further develop and improve a novel frequency-sensitive approach for inductive ESR detection which should allow to improve the state-of-the-art in spin sensitivity by several orders of magnitude.The proposed frequency-sensitive detection method utilizes a fully-integrated LC tank oscillator as sensor. Using fully-integrated CMOS oscillators as detectors offers three major advantages over standard inductive ESR detection: First, fully-integrated CMOS detectors present an elegant approach towards detector miniaturization providing an intrinsically better spin sensitivity. Next, in a given technology oscillators can be designed for a significantly higher operating frequency compared to e.g. low noise amplifiers. Since the achievable spin sensitivity improves proportional to the square of the operating frequency, this is the most important advantage of the oscillator based detection. Last, the oscillator based detection requires no expensive external RF source to produce the B1-field because the coil both detects the signal and produces the RF field exciting the spin ensemble at the same time. In the frame of the project we plan to design fully-integrated CMOS LC tank oscillators for Q- V- and W-band operation and verify their spin sensitivity using ESR based methods. In this way, we expect to obtain spin sensitivities around 106 spins/G/Hz^(1/2) (300 K) and 104 spins/G/Hz^(1/2) (4 K), improving the state-of-the-art by about two orders of magnitude.