Towards electron spin resonance of mechanically exfoliated graphene

Abstract

We have attempted to prepare graphene samples by mechanical exfoliation of HOPG (highly oriented pyrolytic graphite) using scotch tape. Random testing of the flakes by AFM has shown in majority single layer graphene. Nevertheless, the presence of ultrathine graphite cannot be excluded in the large assembly of flakes needed for electron spin resonance (ESR) measurements. Graphene flakes sitting on ESR-silent scotch tapes were stacked parallel to form a multilayer sandwich. The ESR measurements performed in the 4-300 K range yielded narrow Lorentzian line.The spin susceptibility was decreasing linearly with decreasing temperature as expected for the conical band dispersion of graphene. Below 70 K the spin susceptibility started to deviate from the linear temperature dependence and a Curie-like behavior was observed. This contribution to the susceptibility is due to the existence of defects or impurities, which are in strong exchange coupling limit with conduction electrons. The temperature dependence of the linewidth suggests Elliott's mechanism for spin relaxation in graphene flakes.

Preparation and characterization of partially reduced graphene oxide aerogels doped with transition metal ions

“…The EPR signals shape, intensity, g factor, linewidth, spin concentration is source of large number of information about local site symmetry, local dynamic and electron relaxation [50]. EPR study of graphene and graphene-related materials gives an important information about interactions and magnetism sources like defects, not passivated magnetic moments on edges, surface adatoms with unpaired magnetic moments, conduction electrons, and also remaining metal ion contamination [28,[51][52][53][54][55][56][57][58][59]. Unpaired electrons located on edges, on/in the graphene surface, are extremely sensitive to external conditions like atmosphere (oxygen, helium and vacuum) or moisture influencing the localization of Figure 7 Raman spectra of the reference and TMi-doped prGO aerogels.…”

Size effects in the conduction electron spin resonance of anthracite and higher anthraxolite

“…CESR was studied, e.g. in metals: sodium, lithium, and semiconductors and carbon materials: graphite and graphene, where the signal is entirely or mostly stemming from quasi‐free electrons or holes. The observation of the CESR phenomenon in materials with high electrical conductivity is technically difficult, and the description of the spectra requires consideration of a number of additional effects.…”

Testing the Elliott-Yafet spin-relaxation mechanism in KC8: A model system of biased graphene

“…It is, however, limited by the relatively large amount of samples required, which has hindered ESR studies on graphene. 23 It was recently shown by angle-resolved photoemission studies that alkali intercalated graphite is a model system of biased graphene since the alkali atoms effectively decouple the graphene layers. [24][25][26] Graphite intercalation compounds (GICs) have been known for decades 27 and ESR was reported on them, 28 but to our knowledge no thorough study has been performed in order to unravel the relaxation mechanism and in particular to study its anisotropy.…”