Highfield ESR using integrated CMOS LC tank oscillator as detectors

• Applicant: Professor Dr. Jens Anders
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Microsystems
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262194705

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.

• DFG Programme: Research Grants