Electron spin resonance microcopy (ESRM) is an imaging method aimed at the observation of paramagnetic species in small samples with micron-scale spatial resolution. At present, this technique is pursued mainly for biological applications at room temperature and in relatively low static magnetic fields. This work is focused on the use of ESRM for the measurement of solid samples. First, a brief comparison of various electron spin resonance (ESR) detection techniques is provided, with an emphasis on conventional "induction detection". Following that, some methodological details are provided along with experimental examples carried out at room temperature and in a static field of approximately 0.5 T. These examples show for the first time the imaging of solid samples measured by "induction detection" ESR with a resolution better than 1 mum. Based on these experimental examples and capabilities, an outlook for the future prospects of this methodology in terms of spin sensitivity and resolution is provided. It is estimated that single-spin sensitivity could be achieved for some samples at liquid-helium temperatures and static fields of approximately 2 T. Furthermore, under these conditions, spatial resolution could reach the nanometer scale. Finally, a description of possible applications of this new methodology is provided.
This work presents the design, construction, and experimental testing of unique sensitive surface loop-gap microresonators for electron spin resonance (ESR) measurements. These resonators are made of "U"-shaped gold structures with typical sizes of 50 and 150 μm that are deposited on a thin (220 μm) rutile substrate and fed from the rear by a microstrip line. This allows accommodating a large flat sample above the resonator in addition to having variable coupling properties. Such resonators have a very small volume which, compared to previous designs, improves their absolute spin sensitivity by a factor of more than 2 (based on experimental results). They also have a very high microwave field-power conversion ratio of up to 86 gauss/√Hz. This could facilitate the use of very short excitation pulses with relatively low microwave power. Following the presentation and the discussion of the experimental results, ways to further increase sensitivity significantly are outlined.
Electron spin resonance microscopy (ESRM) was employed in the evaluation of diffusion characteristics of point defects (E′ ′ ′ ′ paramagnetic centers) in amorphous SiO 2. Samples were subjected to inhomogeneous γ γ γ γ-irradiation creating a heterogeneous distribution of E′ ′ ′ ′-centers in SiO 2 substrates. The samples were measured by ESRM after preparation and following several heat treatment cycles.
Electron Spin Resonance Microcopy (ESRM) is an imaging method capable of observing stable free radicals in small samples with a spatial resolution of ∼1 micron. Currently this technique is pursued mainly for biological applications at room temperature and at relatively low static magnetic fields. Future progress, which involves the use of higher magnetic fields at cryogenic temperatures, could significantly improve sensitivity and resolution and thus make this method attractive to many solid‐state and physical science applications. Here we consider a possible application of ESRM to the field of quantum computing employing Endohedral Nitrogen fullerene (N@C60) molecules. In order to fully address the challenges of quantum computing, the resolution should be significantly improved to ∼10 nm and the sensitivity should approach the single spin level. In the present work we show some preliminary results conducted with diluted N@C60 samples. A 2D image of N@C60 dispersed on a surface was obtained at a field of ∼0.6 T and at room temperature. Under these conditions the current sensitivity of the ESRM system is around 107−108 spins, and due to the low enrichment factor of the N@C60 sample (∼10−6), we were able to reach image resolution of only ∼50 m̈m. Future steps that are taken in order to significantly improve resolution and sensitivity of the system are discussed. These include the use of highly concentrated samples to be measured at ∼4 K and at a field of more than 1 T, which would lead to a resolution of ∼100 nm and a sensitivity of ∼100 spins.
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