Electrical conductivity-morphology relationships of liquid-exfoliated graphite

Abstract

Liquid phase exfoliation (LPE) is a frequently employed technique for the scalable production of dispersible graphene and graphite nanosheets for electronic, optoelectronic, and photonic applications. Fundamental information on how the liquid exfoliation process and resulting size-distribution of these nanoflakes affects their electrical properties is lacking. To address this gap, terahertz time-domain spectroscopy (THz-TDS) is employed as a non-contact optical approach for determining the AC conductivity behavior and charge transport dynamics of these materials. Cascade centrifugation is employed to separate exfoliated flakes into a range of sizes as confirmed by profilometry measurements. Correlations between the flake area and carrier concentration/scattering time are observed and related to flake morphology through changes to carrier mean free paths and edge defects. A lack of control to the flake chemistry leaves open questions regarding the influence of doping levels on the charge carrier dynamics, which will be the focus of future work.