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。它们使得能够研究顺磁物质的结构、动力学和空间分布。与基于核磁共振（NMR）的方法相比，由于更大的平衡磁化强度，基于ESR的技术显示出显著更好的自旋灵敏度，使其成为现代生命科学应用中质量受限样品分析的良好候选者。尽管可以用许多不同的物理原理检测ESR现象，但其中一些显示出显著更好的自旋灵敏度，电感检测，由于其非侵入性的性质和与所有生物样品的完全兼容性，是迄今为止最通用的ESR检测方法。基于这一事实，建议的研究项目的目标是进一步开发和改进一种用于感应ESR检测的新型频率敏感方法，该方法应允许将自旋灵敏度的最新技术水平提高几个数量级。建议的频率-灵敏的检测方法利用完全集成的LC谐振振荡器作为传感器。使用全集成CMOS振荡器作为探测器与标准电感ESR探测相比具有三大优势：首先，全集成CMOS探测器为探测器小型化提供了一种优雅的方法，提供了本质上更好的自旋灵敏度。接下来，在给定技术中，与例如低噪声放大器相比，振荡器可以被设计用于显著更高的操作频率。由于可实现的自旋灵敏度与工作频率的平方成比例地提高，这是基于振荡器的检测的最重要的优点。最后，基于振荡器的检测不需要昂贵的外部RF源来产生B1场，因为线圈既检测信号又同时产生激励自旋系综的RF场。在这个项目的框架中，我们计划设计用于Q-V-和W-波段操作的全集成CMOS LC振荡器，并使用基于ESR的方法验证它们的自旋灵敏度。通过这种方式，我们期望获得约106自旋/G/Hz^（1/2）（300 K）和104自旋/G/Hz^（1/2）（4 K）的自旋灵敏度，将现有技术提高约两个数量级。

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.