Raman scattering and electrical resistance of highly disordered graphene

TL;DR

This study investigates how increasing disorder in graphene affects its Raman spectra and electrical resistance, revealing that extreme disorder leads to film fragmentation and a resistance limit related to graphene's minimal conductivity.

Contribution

It provides a detailed analysis of the relationship between structural disorder, Raman spectral features, and electrical resistance in irradiated graphene films, highlighting the transition to non-continuous states.

Findings

Raman spectra disappear at high disorder levels.

Resistance exponentially increases with disorder.

Maximum resistance approaches the reciprocal of minimal graphene conductivity.

Abstract

Raman scattering (RS) spectra and current-voltage characteristics at room temperature were measured in six series of small samples fabricated by means of electron-beam lithography on the surface of a large size (5x5 mm) industrial monolayer graphene film. Samples were irradiated by different doses of C${}^+$ ion beam up to $10^{15}$ cm${}^{-2}$. It was observed that at the utmost degree of disorder, the Raman spectra lines disappear which is accompanied by the exponential increase of resistance and change in the current-voltage characteristics.These effects are explained by suggestion that highly disordered graphene film ceases to be a continuous and splits into separate fragments. The relationship between structure (intensity of RS lines) and sample resistance is defined. It is shown that the maximal resistance of the continuous film is of order of reciprocal value of the minimal graphene conductivity $\pi h/4e^2\approx 20$ kOhm.