Raman Mapping Analysis of Graphene-Integrated Silicon Micro-Ring Resonators

Abstract

We present a Raman mapping study of monolayer graphene G and 2D bands, after integration on silicon strip-waveguide-based micro-ring resonators (MRRs) to characterize the effects of the graphene transfer processes on its structural and optoelectronic properties. Analysis of the Raman G and 2D peak positions and relative intensities reveal that the graphene is electrically intrinsic where it is suspended over the MRR but is moderately hole-doped where it sits on top of the waveguide structure. This is suggestive of Fermi level ‘pinning’ at the graphene-silicon heterogeneous interface, and we estimate that the Fermi level shifts down by approximately 0.2 eV from its intrinsic value, with a corresponding peak hole concentration of ~ 3 × 1012 cm−2. We attribute variations in observed G peak asymmetry to a combination of a ‘stiffening’ of the E 2g optical phonon where the graphene is supported by the underlying MRR waveguide structure, as a result of this increased hole concentration, and a lowering of the degeneracy of the same mode as a result of localized out-of-plane ‘wrinkling’ (curvature effect), where the graphene is suspended. Examination of graphene integrated with two different MRR devices, one with radii of curvature r = 10 μm and the other with r = 20 μm, indicates that the device geometry has no measureable effect on the level of doping.

Graphene oxide integrated silicon photonics for detection of vapour phase volatile organic compounds

“…However, the I D /I G ratio is also known to be electrically tuneable 32 , suggesting that it is influenced by localised (trapped) charges, e.g. at the GO/silicon waveguide interface, which could explain the difference we observe here for the GO close to the MRR structure 33 .…”

“…The quality factor (λ/Δλ) of the MRR cavity resonance decreases from ~9000 to ~7500 after GO deposition. This relatively small change suggests that the absorption of light by the GO is not as strong as for graphene 33,36 , which is a key aspect for a functional layer for MRR based gas or vapour sensing, where a high quality factor is preferred, for a given detection resolution, in order to be able to measure relatively small shifts in the resonant wavelength.…”

Inhibition of cold‐welding and adhesive wear occurring on surface of the 6061 aluminum alloy by graphene oxide/polyethylene glycol composite water‐based lubricant

“…The GO/PEG composite shows strong FT‐IR absorption peaks at 3421, 2889, 1488, 1343, 1109, 962, and 842 cm −1 . Of these, CH stretching at 2889 cm −1 , CH bending at 1488 and 1343 cm −1 , COC stretching at 1109 cm −1 , and CO stretching and CH stretching at 962 and 842 cm −1 , respectively, are attributed to PEG access 26,36 …”

“…Figure 2H represents the TGA curves for GO and GO/PEG from the graph. It can be seen that GO shows an acute heat loss from 30°C to 100°C, 160°C to 200°C, and 480°C to 530°C, respectively, which is mainly attributed to the water and oxygen‐containing functional groups in the sample, whereas GO/PEG shows a larger acute heat loss from 180°C to 420°C, this is due to the higher PEG content in GO/PEG and the degradation of the PEG backbone resulting in a loss of mass 36 …”

Hybrid Integrated Nanophotonic Silicon-based Structures

“…In order to achieve optical integrated functions, some "active" materials, e.g. polymers [16][17][18][19], graphene [20,21], carbon nanotubes (CNTs) [22][23][24][25][26][27], III/V compounds [28][29][30], quantum dots [31][32][33] have been integrated in/on silicon. Among those, semiconducting single-walled CNTs (s-SWNTs) have also drawn much attention because of their outstanding unique physical properties and chemical stability as well as nonlinear optical behavior [34][35][36].…”