Abstract
Graphene’s novel electrical, optical, and mechanical properties are affected both by substrate interaction and processing steps required to fabricate contacts and devices. Annealing is used to clean graphene devices, but this can lead to doping and defect changes and strain effects. There is often disagreement about which of these effects are occurring and which result in observed changes in Raman spectra. The effects of vacuum annealing on mechanically exfoliated pristine, suspended, and attached thin and thick few-layer graphene on SiO2/Si are investigated here using scanning electron microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM). Before annealing, Raman shows that the differences in 2D and G band positions and the appearance of a disorder-induced D band of all regions were mainly because of compressive or tensile structural deformations emerging through mechanical exfoliation instead of charge doping. Annealing at low temperature is sufficient to eliminate most of the defects. However, compressive strain is induced in the sheet by annealing at high temperature, and for thin regions increased substrate conformation leads to the apparent disappearance of the sheets. The intensity ratio of the 2D and G bands also reduces with induced compressive strain, and thus should not be used to detect doping.
Highlights
Graphene has many novel electrical, optical, and mechanical properties that make it a promising material for building the generation of nanoelectronics [1,2,3]
Raman shows that the differences in 2D and G band positions and the appearance of a disorder-induced D band of all regions were mainly because of compressive or tensile structural deformations emerging through mechanical exfoliation instead of charge doping
2 and attached to the substrate, studying we investigate the effects of holes annealing exfoliated pristine by graphene of the changes with Raman spectroscopy, scanning electron microscopy (SEM), and atomic force different thicknesses, both suspended over holes in SiO
Summary
Graphene has many novel electrical, optical, and mechanical properties that make it a promising material for building the generation of nanoelectronics [1,2,3]. D bandtoisthe caused by the breathingBrillouin modes of sp band arisesBrillouin from thezone first-order process doubly degenerate zone atoms is activated by doubly disorder It does notmodes appearofinspdefect-free graphene, and center and phonon mode. We investigate the effects of holes annealing exfoliated pristine by graphene of the changes with Raman spectroscopy, scanning electron microscopy (SEM), and atomic force different thicknesses, both suspended over holes in SiO and attached to the substrate, by studying the microscopy at 200. At higher temperatures effects are induced, of thin regions of graphene The onset of these effects occurs at different temperatures for thick, causing wrinkles in the sheets, increased deformation, and the apparent disappearance of thin, thin and suspended graphene. The onset of these effects occurs at different temperatures for thick, thin, and suspended graphene
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