Density of states deduced from ESR measurements on low‐dimensional nanostructures; benchmarks to identify the ESR signals of graphene and SWCNTs

Abstract

Electron spin resonance (ESR) spectroscopy is an important tool to characterize the ground state of conduction electrons and to measure their spin-relaxation times. Observing ESR of the itinerant electrons is thus of great importance in graphene and in single-wall carbon nanotubes (SWCNTs). Often, the identification of CESR signal is based on two facts: the apparent asymmetry of the ESR signal (known as a Dysonian lineshape) and on the temperature independence of the ESR signal intensity. We argue that these are insufficient as benchmarks and instead the ESR signal intensity (when calibrated against an intensity reference) yields an accurate characterization. We detail the method to obtain the density of states from an ESR signal, which can be compared with theoretical estimates. We demonstrate the success of the method for K doped graphite powder. We give a benchmark for the observation of ESR in graphene.

Strong Interplay between the Electron Spin Lifetime in Chemically Synthesized Graphene Multilayers and Surface‐Bound Oxygen

“…[13] Hence, in regions in which O 2 and graphene electron spins are separated by less than % 1.1 nm, an ESR signal would not be observed in our experiments. This is because ESR can only detect regions in which the line width is sufficiently narrow, as the signal amplitude is inversely proportional to the square of the line width.…”

“…This is because ESR can only detect regions in which the line width is sufficiently narrow, as the signal amplitude is inversely proportional to the square of the line width. [13] Hence, in regions in which O 2 and graphene electron spins are separated by less than % 1.1 nm, an ESR signal would not be observed in our experiments. This is the origin of the loss of the ESR signal upon O 2 exposure.…”

“…The absolute value of c was determined by a calibrated CuSO 4 ·5 H 2 O reference sample. [13] The g-factor was determined with the aid of 10 ppm Mn-doped Mn/MgO powder with g = 2.0014. [14] 3.…”

Light-induced charge transfer at the CH3NH3PbI3/TiO2 interface—a low-temperature photo-electron paramagnetic resonance assay

“…Although all three spectra reveal the presence of paramagnetic species, it can be concluded that blue-TiO 2 NWs provide the strongest EPR-detectable feature (blue trace). In particular, as discussed in details in [53], the strong EPR signal observed for blue-TiO 2 NWs corresponds to a powder EPR spectrum of the surfacelocated Ti 3+ paramagnetic centers. We demonstrate our general approach to study the interface using the blue-TiO 2 NWs due to the large Ti 3+ surface defect concentration and the corresponding large EPR signal intensity.…”

“…We demonstrate our general approach to study the interface using the blue-TiO 2 NWs due to the large Ti 3+ surface defect concentration and the corresponding large EPR signal intensity. For distorted (tetragonally-elongated) octahedral sites this signal can be fitted with a uniaxial powder distribution having two g-factor components: parallel (g P =1.94) and perpendicular (g ⊥ =1.97) ( [53] and references therein). The temperature dependence of the EPR signal intensity confirmed the Curie-type behaviour for these Ti 3+ -related paramagnetic centers in blue-TiO 2 NWs (see supplementary material, figure S4.).…”