Sample 4
Graphene on Copper Sample Characterization
This document summarizes the general characteristics of the graphene samples that are grown on 70µm copper foils. This recipe is optimized to reduce the presence of multilayer graphene and provide truly monolayer graphene. A summary of the graphene properties is listed in the table below.
Description of Characterization
| Graphene Coverage (%) | >99% |
| Multilayer Coverage (%) | < 1% - Higher coverage on edge of samples is expected |
| Average Crystal size | ~ 50 µm |
| Sheet resistance (Ω/sq) – large area average | 799 ± 35 Ω/sq |
| I2D/IG Average - after transfer | > 1 |
| ID/IG Average - after transfer | < 0.1 |
| 2D peak width average (cm-1) - after transfer | ~ 35 |
| Cu grain orientation | Polycrystalline |
After the graphene growth on copper, samples are inspected by optical microscopy, scanning electron microscopy and Raman Spectroscopy then transferred to silicon wafers using the wet etching method for further characterizations. Hereafter details of the characterizations are presented.
Optical Microscopy Images
Samples show high graphene coverage on Cu catalyst. Grain boundaries between Cu grains are present indicating that the catalyst is polycrystalline.
Scanning Electron Microscopy Images
Graphene on 70µm copper
Notes : The sample shows high graphene coverage (>99%). Presence of minimal tearing and multilayer graphene is expected on parts of the samples, and specifically at sample edges.
Raman Spectroscopy
Graphene defect levels are evaluated using Raman Spectroscopy. This technique is sensitive to changes on the atomic scale and is useful for the study of disorder in graphene films. At General Graphene, Raman spectroscopy is performed using InVia Renishaw Raman microscope equipped with 50x and 100x·objectives with 532 nm laser excitation on 1800-line grating.
Raman Spectroscopy shows the presence of G and 2D peaks indicative of graphene presence – A low D-peak (ID/IG < 0.1) may be seen on some parts of the samples. Below shows representative Raman spectra for graphene on SiO2/Si wafer and on Cu.
Raman spectra of graphene on copper:
