Influence of ageing on Raman spectra and the conductivity of monolayer graphene samples irradiated by heavy and light ions

Abstract

The influence of long-term ageing (about one year) on the Raman scattering (RS) spectra and the temperature dependence of conductivity has been studied in two series of monolayer graphene samples irradiated by different doses of C + and Xe + ions. It is shown that the main result of ageing consists of changes in the intensity and position of D-and G-and 2D-lines in RS spectra and in an increase of the conductivity. The observed effects are explained in terms of an increase of the radius of the "activated" area around structural defects.

Irradiation-induced broadening of the Raman spectra in monolayer graphene

“…The value of k reflects the average fraction of carbon vacancies in the graphene lattice per ion impact. For C + ions with M = 12 in atomic mass units (amu) and for Xe + ions (M = 131 amu) with E = 35 keV, k = 0.06-0.08 and 0.8 correspondingly [10]. The changes in the intensities of both D-and 2D-lines ID and I2D with increase of Nd in these samples were studied in [10][11][12].…”

“…For C + ions with M = 12 in atomic mass units (amu) and for Xe + ions (M = 131 amu) with E = 35 keV, k = 0.06-0.08 and 0.8 correspondingly [10]. The changes in the intensities of both D-and 2D-lines ID and I2D with increase of Nd in these samples were studied in [10][11][12]. It was shown that I2D continuously decreases, while ID first increases and then decreases, the maximal value is achieved at Nd ≈ 4x10 12 cm -2 , which corresponds to the mean distance between defects Ld ≈ (Nd) -1/2 ≈ 5 nm.…”

“…In this work we study the broadening Γ (full width at half maximum, FWHM) for three main RS lines (G-, D-, and 2D-) for series of monolayer graphene samples gradually disordered by irradiation with Xe + and C + ions [10][11][12]. Fig.…”

“…Ion irradiation induced disorder is not quite stable: some changes in the intensity of RS line were observed in irradiated samples after the long-term ageing (about one year) [10]. It was shown also that high-temperature annealing of radiation damage in vacuum and in the forming gas leads to partial reconstruction of the intensity of RS lines and lattice structure [11].…”

Effect of annealing on Raman spectra of monolayer graphene samples gradually disordered by ion irradiation

“…Details of sample preparation, ion irradiation and measurements of RS in our samples before annealing were reported in our previous papers 22,23 . Two initial large scale monolayer graphene specimens (5x5 mm) were supplied by Graphenea Inc.. Monolayer graphene was produced by CVD on copper catalyst and transferred to a 300 nm SiO 2 /Si substrate using wet transfer process.…”