A continuous-wave and pulsed X-band electron spin resonance spectrometer operating in ultra-high vacuum for the study of low dimensional spin ensembles
June 24, 2024
Franklin H. Cho, Juyoung Park, Soyoung Oh, Jisoo Yu, Yejin Jeong, Luciano Colazzo, Lukas Spree, Caroline Hommel, Arzhang Ardavan, Giovanni Boero, Fabio Donati
Rev. Sci. Instrum.
Description
In recent research, significant progress has been made in investigating individual magnetic atoms and molecules deposited onto surfaces. Ensemble-averaging measurements using electron spin resonance offer a promising way to explore surface spin systems, avoiding the additional decoherence introduced by scanning probe tips. In this work, we developed a novel ensemble-averaging electron spin resonance spectrometer specifically designed for investigating surface spin ensembles. Operating at cryogenic temperatures under ultra-high vacuum conditions, our spectrometer has demonstrated a remarkable ten-fold improvement in sensitivity compared to previously realized spectrometers under similar conditions. Our setup enables investigations of spin dynamics and quantum coherence properties, providing a novel tool to evaluate the potential of atomic and molecular spin qubits at surfaces.
Abstract
We report the development of a continuous-wave and pulsed X-band electron spin resonance (ESR) spectrometer for the study of spins on ordered surfaces down to cryogenic temperatures. The spectrometer operates in ultra-high vacuum and utilizes a half-wavelength microstrip line resonator realized using epitaxially grown copper films on single crystal Al2O3 substrates. The one-dimensional microstrip line resonator exhibits a quality factor of more than 200 at room temperature, close to the upper limit determined by radiation losses. The surface characterizations of the copper strip of the resonator by atomic force microscopy, low-energy electron diffraction, and scanning tunneling microscopy show that the surface is atomically clean, flat, and single crystalline. Measuring the ESR spectrum at 15 K from a few nm thick molecular film of YPc2, we find a continuous-wave ESR sensitivity of 2.6 × 1011 spins/G · Hz1/2, indicating that a signal-to-noise ratio of 3.9 G · Hz1/2 is expected from a monolayer of YPc2 molecules. Advanced pulsed ESR experimental capabilities, including dynamical decoupling and electron-nuclear double resonance, are demonstrated using free radicals diluted in a glassy matrix.