Tuning Conductivity and Spin Dynamics in Few‐Layer Graphene via In Situ Potassium Exposure

Abstract

Chemical modification such as intercalation or doping of novel materials is of great importance for exploratory material science and applications in various fields of physics and chemistry. Herein, the systematic intercalation of chemically exfoliated few‐layer graphene with potassium is reported while monitoring the sample resistance using microwave conductivity. It is found that the conductivity of the samples increases by about an order of magnitude upon potassium exposure. The increased number of charge carriers deduced from the electron spin resonance (ESR) intensity also reflects this increment. The doped phases exhibit two asymmetric Dysonian lines in ESR, a usual sign of the presence of mobile charge carriers. The width of the broader component increases with the doping steps; however, the narrow components seem to have a constant line width.

Magnetoplasma and Cyclotron Phenomena in the High-Temperature X-Band Electron Paramagnetic Resonance Spectra of Graphite

“…This dependence was described as anisotropy of the g -value with the principal values g ⊥ = 2.0023 and g || = 2.0495 at room temperature and g ⊥ = 2.0023 and g || = 2.127 at 77 K. These observations have been confirmed through further research. − The temperature-dependent anisotropy of the g -value was theoretically explained by the spin–orbit interaction and admixture of electron d-functions. , However, the drawbacks of this approach have been discussed in the literature, particularly the direction of the angular dependence of the sharp signal predicted through calculations in the case of three-dimensional graphite differing from that of the experiment. ,, Currently, EPR signals are widely used for investigating and describing carbon-based materials. − Based on the finding that the graphite EPR signal has an asymmetric Dysonian shape, the signal is commonly attributed to charge carriers. Currently, the Dysonian line form of EPR signals is widely used to characterize semimetals, semiconductors, topological insulators, organic conductors, etc. − …”