Affiliation:
1. Department of Physics, University of North Texas, Denton, Texas 76203
2. Department of Mechanical and Energy Engineering, University of North Texas, Denton Texas 76203
3. Department of Materials Science and Engineering, University of North Texas, Denton Texas 76203
Abstract
We report on the properties of defects in exfoliated graphene on SiO2 produced by electron irradiation at 25 keV and dosages from 4.96 × 1015 to 9.56 × 1017 electrons/cm2. With increasing dosage, graphene exhibits the two-stage amorphization trajectory reported for the Ar ion bombardment of graphene. Initially, the ratio of the D-peak height, ID, to the G peak height, IG, increases as new defects are formed. In the second stage, ID/ IG decreases as defects cover most of the sample. In the second stage, we find that the full width at half maximum of the Raman 2 D, D, and G peaks increases by 3, 3, and 6 cm−1, respectively. These values are less by factors of about 10, 5, and 10, respectively, than those reported for amorphous graphene produced by Ar ion bombardment. We find that ID/ IG monotonically decreases in the second stage as the annealing temperature increases from 80 to 220 °C. Assuming that ID/ IG is proportional to the defect density, we find an activation energy for defect healing, Ea = 0.48 eV, which is significantly less than Ea = 0.95 eV reported for vacancies and closer to Ea = 0.29 and 0.58 eV reported for hydrogen and hydroxyl group adsorbates, respectively. We propose that, in the second stage, graphene does not become amorphous, and the defects responsible for the D peak are adsorbates.
Subject
Surfaces, Coatings and Films,Surfaces and Interfaces,Condensed Matter Physics
Cited by
3 articles.
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